Technical Handbook - Skat Consulting Ltd.

Short Span Trail Bridge Standard

Technical Handbook

Volume I: Guideline for Survey,Design & Construction

Volume II: Forms

How to Build a Short Span Trail Suspended Bridge

His Majesty's Government of Nepal, Ministry of Local DevelopmentDepartment of Local Infrastructure Development and Agricultural Roads

Trail Bridge Section

Edited and compiled by : His Majesty's Government of Nepal, Trail Bridge Section, of the Department of Local Infrastructure Development and Agricultural Roads / DoLIDAR with the support of Helvetas Nepal

Published by : SKAT, Swiss Centre for Development Cooperation in Technology and ManagementVadianstrasse 42, 9000 St. Gallen, Switzerland

First edition 2002

Project commissioned by : HELVETASSwiss Association for International Cooperation Post Box 8042 Zürich, Switzerland

Financed by the Swiss GovernmentSwiss Agency for Development and Cooperation, SDCBern, Switzerland

Printed by : Dongol Printers

Copyright : Material from this publication may be freely quoted, translated or otherwise used. Acknowledgement is requested.

Distributors : In NepalTrail Bridge Section, Shree Mahal, Lalitpur, Nepal

Outside NepalSKAT - Bookshop, Vadianstrasse 42, 9000 St. Gallen, Switzerland

ISBN 3-908156-05-X

The views, interpretations, and calculation in this Handbook are the author's and are not attributable to SBD and Helvetas. Anyone using this manual should verify the calculations according to the specific conditions of the site on which the bridges are to be constructed.

FOREWORD

Congruent with HMG's Policy and the Decentralization Act shall the Central Government focus on policy matters, as well as issuing and monitoring norms and standards and shall the Local Governments focus on the implementation thereof.

With this division of mandates, a demarcation policy as well as two technical manuals are DoLIDAR's prime tools for harnessing the trail bridge sector. The first manual on Long Span Trail Bridges (LSTB), this manual on Short Span Trail Bridges (SSTB) together with the demarcation policy form the single most important accomplishment for said sector.

Niranjan P. Chalise Director GeneralDoLIDAR March 2002

The Trail Bridge Section (TBS formerly Suspension Bridge Division, SBD) of the Department of Local Infrastructure and Agricultural Roads (DoLIDAR) is proud on its long-term collaboration with its Swiss Partners represented by Helvetas for project execution and SDC being the funding agent. The collaboration dates back to 1972 and has resulted in the construction of over 500 trail bridges primarily on Main Trails.

In 1989, HMG and Helvetas initiated a new project "Bridge Building at the Local Level (BBLL)" based on indigenous technologies that maximized local resources while minimizing the environmental impact. In its original form, Communities take the lead building their bridges off the main trail according to procedures developed by BBLL. The demand for these bridges that are generally of a short span has proven to be very high resulting in the construction of over 1000 "BBLL bridges" till today. Meanwhile, Local Governments have commenced a vital role supporting the Communities, which will eventually yield BBLL sustainable.

Encouraged by BBLL's success, SBD carefully assessed the situation and decided to develop the Short Span Trail Bridge (SSTB) Handbook for application by any bridge building agent. This new Manual is intended for national application complementing the ”SBD Standard Design" that primarily deals with Long Span Trail Bridges (LSTB). The development of the SSTB-Manual was spearheaded by Helvetas with relentless inputs by Robi Groeli.

Meanwhile, a demarcation policy has been put in place, indicating the applications by the two bridge types, LSTB and SSTB. The Demarcation Policy essentially puts down a cut off point of 120 m span below which SSTB norms apply and above which LSTB norms apply. The reader is referred to the Policy for the finer details of the applications.

I, on behalf of DoLIDAR/TBS, acknowledge the valuable efforts put up by the project team and extend my sincere thanks to all those who were involved in the preparation of this Hand Book.

Neeraj ShahSenior Divisional Engineer DoLIDAR/TBS January 2002

Despite the rugged topography of the Himalayan State of Nepal, the people established and maintained a traditional trail network for centuries. Footpaths and mule trails are the lifelines for the exchange of goods, the sick going to health posts and the children going to school. Despite great efforts in road construction, a large part of the hill population will depend on the traditional trail network for decades to come.

The Himalayan drainage system consists of countless rivers, which divide the hill areas into many micro economic areas. River crossings are the critical links for roads as well as for trails. For bridging shorter spans, the Nepalese have developed in numerous Regions simple, yet remarkable local techniques. This Handbook is an attempt to standardize the indigenous local trail bridge types for span of up to 120 meters, thereby making them conform to modem engineering practices. It encompasses the practical experience made under HELVETAS' local trail bridge programme named "Bridge Building at the Local Level," BBLL, and the Suspension Bridge Project SBP under HMG's Suspension Bridge Division SBD. The Handbook named "Short Span Trail Bridge Standard" is complementary to SBD's "Long Span Trail Bridge Standard" which is applicable for bridges exceeding 120 meter span.

We acknowledge with thanks the efforts provided by the project teams of HMG's Trail Bridge Section and Helvetas under the leadership of Robi Groeli and Gyanendra Rajbhandari. Om B. Khadka was responsible to convert all the standard drawings, sketches and photos onto computer and also for all the desktop publishing.

Our sincere thanks go to all persons who have been involved in the preparation of this Handbook and forwarded their valuable comments and suggestions.We hope that this long awaited Handbook will be widely used by technicians appointed to construct a pedestrian trail bridge of limited span of up to 120 meters.

HELVETAS Nepal, Swiss Association for International Cooperation P.O. Box 688 Kathmandu, Nepal January 2002

Short Span Trail Bridge Standard Suspended Type Volume 1

V O L U M E I : G u id e l in e f o r S u r v e y , D e s ig n & C o n s t r u c t io n

1 . In t r o d u c t i o n _________________________________________________________________________ 1

1.1 B a c k g r o u n d ..................................................................................................................................... 1

1.2 C o n c e p t o f t h e H a n d b o o k ...................................................................................................... 1

1.3 P r e s e n t a t io n o f t h e S u s p e n d e d B r id g e T y p e ............................................................... 2

1.4 T e c h n ic a l F e a t u r e s a n d L im it a t io n s ..................................................................................2

2 . S u r v e y a n d B r id g e S it e S e l e c t i o n ______________________________________________ 3

2.1 S u r v e y a n d B r id g e S ite S e l e c t io n ......................................................................................3

2.1 .1 S o c ia l F e a s ib il it y S u r v e y ..........................................................................................4

2 .1 .2 T e c h n ic a l S u r v e y ..........................................................................................................4

2 .2 P r e p a r a t io n f o r S u r v e y ..........................................................................................................4

2 .3 G e n e r a l D a t a C o l l e c t io n ....................................................................................................... 52.3.1 Lo c a tio n o f B r id g e S i t e ................................................................................................ 52.3.2 Na t u r e o f C r o s s in g a n d Fo r d a b il it y ...................................................................... 62.3.3 T r a f fic V o l u m e ................................................................................................................. 62.3.4 W idth o f W a l k w a y ........................................................................................................... 72.3.5 Lo c a l Pa r t ic ip a t io n .........................................................................................................72.3.6 T r a n s p o r t a t io n D is t a n c e ............................................................................................ 72.3.7 A v a ila b il it y o f Lo c a l Ma t e r ia l s ................................................................................ 82.3.8 A v a ila b il it y o f Lo c a l B r id g e B u il d e r s ....................................................................82.3.9 T e m p o r a r y C r o s s in g ...................................................................................................... 8

2 .4 B r id g e S ite S e l e c t io n ............................................................................................................... 92.4.1 G e n e r a l C o n d it io n ........................................................................................................... 92.4.2 R iver C o n d it io n ............................................................................................................... 122.4.3 S lo pe a n d Ba n k C o n d it io n ..................... 132.4.4 Ev a lu a t io n o f th e B r id g e S it e ................................................................................. 222.4.5 C la s s if ic a t io n o f S o il a n d R o c k ..............................................................................222.4.6 Id e n t if ic a t io n o f S o il a n d Ro c k ...............................................................................24

2 .5 T o p o g r a p h ic S u r v e y ............................................................................................................... 2 52.5.1 S u r v e y A r e a ..................................................................................................................... 252.5.2 S e tt in g o f B r id g e C e n t e r l in e ................................................................................. 252.5.3 S u r v e y M e t h o d s ............................................................................................................ 272.5.4 S u r v ey by A b n e y Le v e l ................................................................................................ 272.5.5 S u r v e y By T h e o d o l it e ................................................................................................. 332.5.6 T o p o g r a p h ic M a p s .........................................................................................................39

2 .6 P h o t o g r a p h s ............................................................................................................................... 4 3

2 .7 S u r v e y R e p o r t ........................................................................................................................... 43


3. B r id g e D e s ig n ____________________________________________________________453.1 B r id g e T y p e s ......................................................................................................... : ....................4 5

3 .2 B a s ic D e s ig n C o n c e p t ............................................................................................................. 4 93.2.1 Lo a d in g s .............................................................................................................................493.2.2 C o n s tr u c t io n Ma t e r ia l s ............................................................................................ 503.2.3 S t r u c t u r a l A n aly s is A nd D e s ig n ...........................................................................53

3 .3 D e s ig n o f S t a n d a r d S u s p e n d e d B r id g e ........................................................................583.3.1 T he Ma jo r B ridg e C o m p o n e n t s ...............................................................................583.3.2 D es ig n P r o c e d u r e .........................................................................................................583.3.3 D e s ig n in g th e Po s it io n o f th e B r id g e Fo u n d a t io n s ...................................... 593.3.4 Ca b le D e s ig n .....................................................................................................................643.3.5 D es ig n o f B r id g e Fo u n d a t io n S t r u c t u r e s .........................................................663.3.6 Ot h e r St r u c t u r e s .........................................................................................................723.3.7 G e n e r a l A r r a n g e m e n t D r a w in g ............................................................................. 77

3 .4 D e s ig n E x a m p l e ...........................................................................................................................78

4. B r id g e S t a n d a r d D r a w in g s _____________________________________________ 794.1 In t r o d u c t io n a n d O v e r v ie w o f D r a w in g s ....................................................................79

4 .2 C o n c e p t o f t h e S t a n d a r d D r a w in g s ...............................................................................81

4 .3 R e l a t io n s h ip b e t w e e n c o n s t r u c t io n a n d s t e e l d r a w in g s .................................85

5. C a l c u l a t io n o f Q u a n t it y a n d C o s t E s t im a t e ___________________________875.1 Im p l e m e n t a t io n b y t h e C o m m u n it y ................................................................................... 87

5 .2 Im p l e m e n t a t io n b y t h e C o n t r a c t o r t h r o u g h t h e P u b l ic T e n d e r ..................88

6. C o n s t r u c t io n ____________________________________________________________ 896.1 B r id g e La y o u t ..............................................................................................................................8 9

6 .2 F o u n d a t io n E x c a v a t io n ......................................................................................................... 91

6 .3 L o c a l M a t e r ia l C o l l e c t io n ................................................................................................926.3.1 St o n e /B o u l d e r s ............................................................................................................. 926.3.2 Sa n d ......................................................................................................................................936.3.3 G r a v e l .................................................................................................................................93

6 .4 TRANSPORTATION AND STORAGE OF THE MATERIALS...................................................... 936.4.1 C e m e n t T r a n s p o r ta t io n a n d St o r in g .................................................................. 936.4.2 St e e l Pa r t s T r a n s p o r t a t io n a n d St o r in g .........................................................936.4.3 W ire Ro p e T r a n s p o r ta t io n a n d S t o r in g ............................................................ 94

6 .5 M a s o n r y a n d S t o n e D r e s s in g W o r k ...............................................................................966.5.1 R e q u ir e m e n ts fo r B u ild in g St o n e s ....................................................................... 966.5.2 Q u a r r y in g ..........................................................................................................................966.5.3 St o n e D r e s s in g .............................................................................................................. 976.5.4 Sto n e Ma s o n r y La y in g ................................................................................................98


6 .6 C e m e n t W o r k s .................................... 1006.6.1 C o m p o s it io n a n d M ix t u r e s .......................................................................................1006.6.2 C o n c r e t e W o r k fo r C e m e n t Sto n e Ma s o n r y (CSM ) T o w e r s ................1026.6.3 C o n s t r u c t in g th e D e a d m a n B e a m .........................................................................1046.6.4 C o n s t r u c t in g D rum A n c h o r a g e s in R o c k ........................................................105

6 .7 C a b l e H o is t in g a n d S a g S e t t in g .....................................................................................1076.7.1 C a lc u la t io n o f Ho is t in g Sa g ..................................................................................1076.7.2 C a b le Ho s t in g ............................................................................................................... 108

6 .8 F in a l iz in g t h e C a b l e A n c h o r a g e .....................................................................................1086.8.1 R u st P r o t e c tio n fo r th e C a b l e .......................................................................... 1086.8.2 C o m p le t in g th e G r a v ity S t r u c t u r e ...................................................................108

6 .9 W a l k w a y F it t in g ...................................................................................................................... 109

6 .1 0 W a t e r M a n a g e m e n t B a c k f il l in g a n d G e n e r a l f in is h in g W o r k s ...................1106.10.1 W a t e r Ma n a g e m e n t ..................................................................................................1106.10.2 F in is h in g W o r k .......................................................................................................... 110

7. B r id g e M a in t e n a n c e ___________________________________________________ 1117.1 In t r o d u c t io n .............................................................................................................................. 111

7 .2 R o u t in e M a in t e n a n c e .......................................................................................................... 111

7 .3 M a j o r M a in t e n a n c e .............................................................................................................. 112

VOLUME II F o r m s

F o r m N o .1 S u r v e y F o r m a n d C h e c k l is t F o r m N o .2 B r id g e D e s ig n

F o r m N o .3 Q u a n t it y & C o s t E s t im a t e f o r C o m m u n it y A p p r o a c h F o r m N o .4 Q u a n t it y & C o s t E s t im a t e f o r P u b l ic T e n d e r & C o n t r a c t in g

VOLUME III S t e e l & C o n s t r u c t io n D r a w in g s(IN SEPARATE FOLDER)

Short Span Trail Bridge Standard Suspended Type Volume I

V olum e I :

G uideline for S u r vey , D esign & C o nstructio n


1. In t r o d u c t io n

1.1 B a c k g r o u n d

For centuries, people have built simple and inexpensive bridges throughout Nepal. With the advent of modem development, organizations emerged which built suspension bridges where local resources appeared to be over burdened. In this manner, some five hundred sophisticated and costly bridges have been built over the last four decades, which greatly facilitate the movement of goods and people along the major traffic arteries of this country.

At the same time, the intervention of extraneous agencies may have weakened the attitude of self-reliance of many communities. It is also widely understood that external agencies will never be able to meet all the demands for local river crossings. Hence the idea of reactivating and supporting communities' own initiatives for improving their environment and infrastructure in the spirit of decentralization. In view of the absence for technical guidance material, it has become significant for technicians at district level to have a tool for designing economic bridges appropriate for communities in rural areas.

Against this background, the development of the Short-Span Trail Bridge Standard started in 1989, when both HMG and Helvetas concluded that the time has come to initiate a programme with a fresh approach to community trail bridge building in the hill areas of Nepal.

The ultimate objective of this programme, named Bridge Building at the Local Level (BBLL) was to help reactivate, promote and support people's problem solving and self-help ability for local bridge building. For achieving this goal the development of appropriate techniques for pedestrian trail bridges was o f paramount importance.

The bridge design presented in this manual originates from indigenous local trail bridge types built by Nepali craftsmen for centuries. Recognizing the well-established skills of local trail bridge builders and craftsmen of bridge fabricators, critical and weak components have been improved by an appropriate input of cement and galvanized steel parts.

In the course of the last 12 years, the engineers, overseers, sub-overseers, site supervisors and consultants of the joint Trail Bridge Programs between SDC/Helvetas and HMG's Suspension Bridge Division have developed a standardized, economical and well-tested suspended bridge type design satisfying both engineering requirements and the call for bridge building by local craftsmen.

1 .2 C o n c e p t o f t h e H a n d b o o k

This Handbook provides technical guidelines for the construction of unstiffened pedestrian suspended type cable bridges (catwalk). It does not apply for suspension bridges, which require higher towers or pylons on both sides of the bridge. For these suspension bridges a separate Handbook will be prepared.

This Handbook comprises three volumes and follows the actual step-by-step process of constructing a bridge.

It starts with preparatory work for the site assessment and survey, design and cost estimate and ends with practical guidelines for bridge construction and maintenance.

Chapter 1 Introduction 1


The three volumes have been structured as follows:

Volume I This volume is the guidebook for site survey, bridge design, cost estimation and construction.It serves as a Help and Reference for using the drawings provided in Volume II and the predesigned formats in Volume III.

Volume II Volume two provides all the necessary formats for survey, design and cost estimation.

Volume III Volume three contains all the standardized steel and construction drawings and examples of bridge designs.

The above three volumes provide all the necessary information, drawings and formats for the construction of a suspended type cable bridge. The volumes are structured in such a way that well versed practitioners need to work with Volume II and III only, whereby Volume I serves as a reference Volume II + III. For more scientific background information, respective engineering sources need to be consulted.

1 .3 P r e s e n t a t io n o f t h e S u s p e n d e d B r id g e T y p e

The Suspended Cable Bridge design presented in this Handbook (for details refer to chapter 3.1) has been developed from existing indigenous river crossings built for many generations by Nepali artisans and craftsmen. The major structural elements are steel wire ropes, which are anchored by gravity blocks or rock anchors at either side of the river. The superstructure is completely unstiffened and thus allows "some" reasonable degree of lateral, vertical and torsional vibrations. For economic reasons the design allows a choice between two options for the width of the walkway. The 70 cm walkway is mainly applicable for pedestrian traffic, whereas the 106 cm walkway should be applied for crossings where pack animal traffic is also expected.

Utmost care was taken to make maximum use of local resources, users' capacity, know-how and skills of rural Nepal. The main aim in choosing this approach is to build on existing traditions and thereby promote people's participation, but also make it suitable for local contractors.

1 .4 T e c h n ic a l F e a t u r e s a n d L im it a t io n s

The Short-Span Trail Bridge Standard as presented in this manual conforms to mainly Indian Standard, but also to Swiss and German Standards, codes and norms. All its components fulfill the necessary safety factors by applying the loadings prescribed in the SBD standard design.

All the construction materials conform to international specifications. Exposed steel parts are all hot dip galvanized, and should not be altered unless proven to fulfill standard norms.

For practical, economical and safety reasons the span range for the Short-Span Trail Bridge Standard presented in this Handbook is limited to 120 m.

Longer spans are possible but would require special engineering input. As with every standard design, not all site conditions are covered with this standard. It is especially not suitable in unfavorable geological site conditions. At such sites, as mentioned above for longer spans, engineers' input is mandatory.

1 .5 U s e r s

This Handbook along with the Forms and the Drawings is intended to give quick and reliable technical methods of surveying, designing and constructing simple pedestrian bridges for engineers, overseers and sub-overseers.

2 Chapter 1 Introduction


2. S u r v e y a n d B r id g e S ite S e l e c t io n

2.1 S u r v e y a n d B r id g e S it e S e l e c t io n

Careful Surveys and Bridge Site Assessments are the basis for proper planning and designing and form the main source for successful bridge construction. The main objective of the Survey and Bridge Site Assessment is to identify the proper bridge site by considering socio-economic as well as technical points of view. Survey and Bridge Site Assessment is done in the following two stages:

• Social Feasibility Survey and

• Technical Survey

9 ^ follow Form No. 1 Survey Form and Checklist

Both surveys are of equal importance. The social feasibility survey establishes community ownership and responsibility, and the technical survey ensures that bridge construction is sound and safe.

The Survey process follows as per the flow chart below:

Design

Chapter 2: Survey and Bridge Site Selection 3


2.1.1 S o c ia l F e a s ib il it y S u r v e y

A Social Feasibility Survey is necessary to justify the construction of a requested bridge. For ranking and prioritizing the vast number of requests, the following socio-economic indicators are of utmost importance:

• Level of local participation • Size of area of influence• Size of traffic flow • Socio-economic benefits produced by the proposed bridge

The first step for conducting a social feasibility survey is to introduce the participants, the survey team and other groups who will be involved in the process of bridge construction. This is best done in the fonn of a mass meeting right at the spot, or nearby the place, where the bridge is going to be built. The mass meeting should consist of the following agenda:

• Verification of the proposed bridge site with official documentation together with the community• Explanation of the bridge building process and the role of the community:

Phase I: collection o f local materials (sand, gravel, stones and boulders), dressing o f stones andexcavation work.Phase II: carrying (portering) o f construction materials from the nearest road head to the sitePhase III: masonry and concrete work, cable pulling and fitting

• Explanation of the self-help nature of the project• Evaluation and explanation of the bridge location regarding technical limitations and requirements

(e.g. width of walkway see 2.3.4), costs and situation of local traffic• Assessment of capacity of the community, funds & technical support from outside

One of the major indicators reflecting the real need of the bridge is the degree of participation and the commitment demonstrated by the local community or beneficiaries in the construction of the iequested bridge. These indicators are assessed and measured from different points of view depending on the need and purpose of the bridge. However a Social Feasibility Survey is not included in this Technical Handbook, for further details refer to the Social Organization Support (SOS) Manuals of the BBLL Programme.

2 .1 .2 T e c h n ic a l S u r v e y

The technical survey includes:• Bridge site selection and Topographic Survey of the selected bridge site

2 .2 P r e p a r a t io n f o r S u r v e y

The following preparatory work must be completed before going to the field for the survey:• Collect maps with tentative location of the bridge and any available background information.• Collect the survey equipment.

Survey equipment consists of the following materials:

For Survey by Abney Level- Abney Level, Survey Form & Checklist- Measuring Tape (50 or 100m and 3m)- Red Enamel Paint and Paint Brush- Marker Pen, Scale and A3 Graph Paper- Camera and Film Roll- Hammer- Ranging Rod (prepared at site)- Calculator, Note Book & Pencil- Nylon Rope (min. 50m) Masons Thread

For Survey by Theodolite- Theodolite, Tripod & Staff- Measuring Tape (50m and 3m)- Red Enamel Paint and Paint Brush- Marker Pen, Scale and A3 Graph Paper- Camera and Film Roll- Hammer- Survey Form and Checklist- Calculator, Note Book & Pencil- Thread and Plumb Bob

4 Chapter 2: Survey and Bridge Site Selection


2 .3 G e n e r a l D a t a C o l l e c t io n

General data is required for needs assessment and construction planning of the proposed bridge. Collect the following general data and information:- Location of bridge site - Transportation distance - Nature of crossing and fordability- Availability of local materials - Traffic volume - Availability of local bridge builders- Temporary crossing - Local participation

2.3.1 Lo ca tio n of B r id g e S ite

Describe the location of the bridge site:

Left Bank Right BankVDCWard No.llaka No.District.Zone

Draw a bridge site location map covering the proposed bridge’s area of influence as shown in the example below. The map should contain the following information:

• River system with names and river flow direction• Location of proposed bridge and traditional crossing point• Location of the nearest bridge (approximate walking distance from the proposed bridge site)• Existing trail system and, if required, specify length of new trail for access to the proposed bridge• Location of the villages, health posts, schools and other important places with approx, distances to the

bridge site

\Bridge Site Location Map (Example)

To village “E”f - Hospital

To village “D”- Airstrip


2.3 .2 Na t u r e o f C r o s s in g a n d F o r d a b il it y

Examination of the present crossing situation is necessary to determine the need and the priority of the requested bridge.Assess period of time the river cannot be crossed in one year.

a. whole yearb. some months per year onlyc. some days during high flood only

Situation (a) should be given first priority for construction and least priority given to situation (c).

Study the type of crossing facility available at present and also the location of the nearest bridge. Assess whether the available crossing facility or the existing nearest bridge is sufficient for the crossing or that a new bridge is necessary.

2.3 .3 T r a f f ic V o l u m e

Traffic volume at the crossing is one of the key indicators in the need assessment of the bridge. Information should be collected by 2 methods. Count traffic volume at the traditional crossing point for at least one day. And then interview the local people to form a broader impression of the traffic volume throughout the year.

Average Number o f Traffic per Day

Goods TrafficPorters

Pack Animals

Non-goods TrafficPersons

Animals

Determine the purpose of the traffic by interviewing the persons crossing and the local people as per the table below. This will indicate the importance of the crossing.

Access to Yes No

SchoolsHospital / Health postsBazaar/MarketsRoad headPost office/TelephoneFarmingOthers (specify)

The most important crossing is one which provides access to schools, hospital and health posts.



2 .3 .4 W id th o f W a l k w a y

The standard width of walkway in this handbook is 70 cm or 106 cm.In most cases the 70 cm walkway is sufficient. In stances of heavy traffic, mule and pack animal passage carrying bulky goods, or if the crossing is on a main trail, a 106 cm walkway is necessary.Discuss this issue with the local people, infonning them that more work, especially collection of stones, is required for the 106 cm walkway.

Recommended Width of Walkway: 70 cm | | 106 cm | |

2.3 .5 L o c a l Pa r t ic ip a t io n

The commitment and participation of the local people in the construction of the proposed bridge will truthfully indicate the need of the bridge. The stronger the commitment and participation, the higher is the need of the bridge.

For informing the community on how much labor work is overall generally necessary for constructing the bridge, the following formulas can be used to compute the tentative preliminary number of mandays:

• Mandays for skilled Labor: = 1.3 x span [m] + 400

• Mandays for unskilled Labor: = 5 x Span [m] + 1300

Assess the availability of local participation for bridge building from within the concerned local community.

By Whom Type o f Participation

Local Community

User’s Committee

VDC

DDC

Local NGO

Individual

Others (specify)

2.3 .6 T r a n s p o r t a t io n D is t a n c e

Information on the transportation distance from nearest road head, airstrip and helipad to the site is required for planning the construction of the bridge.

Type o f Transport Name o f nearest Roadhead/Airstrip etc.

Disidance from Site up to Rroadhea d/A i rs trip

Km/Kosh PorterDays

By Mule, Days

Served by Truck

Served by Tractor

Airstrip

Helipad



2 .3 .7 A v a il a b il it y o f Lo c a l M a t e r ia l s

Assess the availability of local materials needed for the bridge construction. Identify the nearest collection place for these materials.

Description Haulage Distance, m Remarks

Stones

Natural Gravel

Sand

Wood

Bamboo

2.3 .8 A v a il a b il it y o f L o c a l B r id g e B u il d e r s

In the villages nearby there may be local bridge builders who have already built some bridges. Their skill can be used in construction of the proposed bridge. If such people are available, record their names.

Names Skill (Mason, Bridge Fitter) Village /Address

2.3 .9 T e m p o r a r y C r o s s in g

Is a temporary crossing necessary during the construction of the bridge? Yes No

If yes, what kind of temporary crossing do you propose? Ferry Cable Car

Temporary Bridge, m Span m



2 .4 B r id g e S it e S e l e c t io n

The main purpose of the technical field survey is to select the appropriate brieve site. The site should optimally serve the local people. The selected site must economically justified and have along life span:

- fulfill the general condition - have stable bank and slope conditions- have favorable river conditions - have shortest possible span

2.4.1 G e n e r a l C o n d it io n

The bridge site should fulfill a number of general conditions:

- traditional crossing point - minimum free board- maximum bridge span - space for the bridge foundations

Use the following checklist to evaluate the general condition:

Traditional Crossing PointFeatures Condition

The bridge site should be selected at or near to the traditional crossing point.

Favorable:Selected site is at or nearby the traditional crossing point

Unfavorable:Selected site is far from the traditional crossing point

• For minor river detour from the tradditional crossing point is not acceptable.

• For major rivers, detour up to 500 m u/s and 500 m d/s from the tradditional crossing point may be acceptable.

Bridge SpanThe bridge span in this standard is limited to 120 m span.

Favorable:span, t is equal or shorter than 120 m

Unfavorable:span, i is longer than 120 m

• Measure tentative span• Compare with the limit



Features

Level Difference between two BanksThe level difference h between the two foundation blocks should

Condition

not be more than i /25.

Favorable:h is equal or less than^/25

Unfavorable:h is bigger than t /25

• Locate the tentative position of the bridge foundations at both banks• Measure the level difference h between the foundations of two

banks.• Compare with the condition.

Space for FoundationFoundation should be placed at least 3 m behind the soil slope and 1.5 m behind the rock slope from the front edge of the riverbank.

Favorable:Condition can be fulfilled

Unfavorable:Condition can not be fulfilled



Features Condition

Slope ProfileThe bridge foundation should be placed behind the line of the angle of internal friction. (Angle of internal friction is the angle of slope of soil or rock at which it is still stable and does not slide).

• Draw a slope line of 35° (angle of internal friction) in case of a Soil slope and 60° in case of a Rock slope.

• Foundation should be placed behind this line.• Check if these conditions can be fulfilled

Favorable:Condition can be fulfilled

Unfavorable:Condition can not be fulfilled

Free Board

The Freeboard between the lowest point of the bridge and the highest flood level should not be less than 5 m. For this, sufficient clearance between the lower foundation saddle and HFL should be maintained.

up to 50 m5171 ■ 91

110

70 m 90 m

110m 120 m

Favorable Unfavorable

Clearance between lower foundation saddle and HFL is:

not less than:

7.5 m8.0 m9.0 m

10.0 m 1 1 . 0 m

less than:

7.5 m8.0 m9.0 m

10.0 m 11.0m

• Identify HFL by local observation and villagers’ information.

• Calculate available clearance and compare with the requirement.

• Exception: At flat or wide river banks free board may be reduced.At gorges free board may have to be increased.



2.4 .2 R iv e r C o n d it io n

The selected bridge site must have favorable river conditions. Accordingly, a bridge should be located:

• on a straight reach of the river• beyond the disturbing influence of larger tributaries• on well defined banks

Use the following checklist to evaluate the river condition:

Features Condition

River FlowIn order to protect the bridge from sudden over-flooding and strong erosion, the bridge site should not be located near the confluence area of two rivers.

Favorable:Bridge site far from river confluences

Unfavorable:Bridge site near river confluences

River BedThe river bed at the selected bridge site should be stable without the possibility of erosion or filling up with bed load (boulders, gravel, silt, or sand)

River bed filled up after heavy flood

Favorable:River bed is not erosive, not filling up

Unfavorable:

River bed is erosive or filling up



2 .4 .3 S lo pe and Ba n k C o n d it io n

A bridge should be located at a site with safe and stable slope and bank conditions. The surveyor must identify any potential instability features or failure modes of the soil or rock slope and along the bank.

If the slope and bank is soil, potential instability features and failure modes are:• bank erosion• toppling instability of the bank• erosion of the slope• land slide

If the slope and bank is rock, potential instability features and failure modes are:• plain failures in a rock slide along the slope.• wedge failure leading to the fall of rock mass.• toppling leading to the fall of rock blocks.• rotational slide is similar to the landslide in a soil slope. Such failure is likely when the material of the

rock is very weak (soft rock) and the rock mass is heavily jointed and broken into small pieces.

To avoid the above instability features, use the following checklist to evaluate the slope and bank of the selected site:

Features

If the River Bank or Slope is SOIL

Bank ProfileThe bank profile should be smooth.

Smooth Partially cut out

Condition

Strongly cut out

Favorable:Bank profile is smooth to partially cut out

Unfavorable.Bank profile is strongly cut out

River Bank ContourThe bridge site should be located at the straight reach of the river to avoid the river from undercutting or bank erosion.

Favorable:River contour is straight or convex

Unfavorable:River contour is concave

Straight Convex Concave



Features Condition

Bank ErosionThe River bank should not show any sign of erosion.

Bank erosion due to high river current

Favorable:No sign of fresh erosion

Unfavorable:Presence of fresh erosion

Slope ProfileThe slope profile should be smooth.

Smooth Partially cut out Strongly cut out

Favorable:Slope profile is smooth to partially cut out

Unfavorable:Slope profile is strongly cut out

Transverse SlopeThe transverse slope should be smooth.

Transverse slope strongly cut out

Favorable:Transverse slope is smooth to partially cut out

Unfavorable:Transverse slope is strongly cut out




Features Condition

Slope Inclination (Soil Slope)The slope inclination should be less than 35°.

Favorable: Slopeinclination isequal or

smaller than 35°

Unfavorable: Slopeinclination isbigger than 35°

Estimate the slope inclination and compare it with the condition. If the site has an unfavorable slope inclination, it can still be selected provided the general condition of slope profile is fulfilled.

River UndercuttingThe bridge site should be free from river undercutting which may lead to landslide.

Landslide caused by river undercutting

Favorable:There is no river undercutting

Unfavorable:River undercutting is active or there is potential for river undercutting



Features Condition

Inclined Trees

Inclined trees on landslide mass

Favorable:Inclined trees are not present

Unfavorable:Inclined trees are present

Seepage or Swampy AreaThe bank slope should not have any seepage or swampy area, which may lead to slope instability.

Favorable:No Seepage or swampy area is absent

Gully ErosionNo signs of gully erosion should exist within the vicinity of the selected site.

Unfavorable:Seepage or swampy area is present

Active gully erosion

Favorable:No sign of gully erosion or only light gully erosion

Unfavorable:Heavy gully erosion exists

• Observe if any rivulets are within the vicinity of the selected site.• If rivulet exists, examine the dimension of the gully cutting.



Slipped (Slump) Soil MassFeatures Condition

The bridge should not be located on already slipped soil masses.

Slope with slipped soil mass

Favorable:There are no back scars or signs of soil mass movement

Unfavorable:There are back scars or signs of soil mass movement

back scar

• Examine and identify any indication of soil mass movement. This can be done by observing traces of back scars on the slope.



Features Condition

If the River Bank is ROCK Plain FailurePlain failures lead to the slide of rock layers along the slope. The rock bank/slope of the selected site should not have any feature of plain failure.

Bedding plain is parallel to the slope and plain failure is active. Site is extremely unfavorable!

Side elevation Plan view Side elevation

\ \ \ \ \\ \ \ \ \\ \ \ \ \ ,\ \ \ \ \

\ \ \ \ \\ \ \ \ \\ \ \ \ \\ \ \ \ \

\ \ \ \ \

Bedding fracture Plane parallel to the slope

Sub parallel to the slope

Opposite to the slope

Direction of movement Bedding / Fracture Plane

Favorable:

Plain failure will not takeplace, if:

• Bedding/fracture plain is subparallel to opposite to the slope

• Bedding/fracture plain is parallel to the slope, but inclination is less than 35°

Unfavorable:

Plain failure will take place, if:

• Bedding/fracture plain is parallel to the slope and inclination is greater than 35°

• Presence of old slided rocks

Plain Failure Model

• Identify bedding/fracture plain (layers of rock)• Check its direction and inclination

Compare with the condition



Features

Wedge FailureAny form of wedge failure leads to sliding of rock masses. The roek bank/slope should not have wedge failures or potential wedge failures.

Condition

Traces of wedge failure

^ Direction of movement ........Fracture Plane

Wedge Failure Model

Wedge Failure

Favorable:

Wedge failure will not take place, if

• There are no fracture plains facing each other

• There are two or more intersecting fracture plains but the inclination of its line of intersection is less than 35°

• There are two or more intersecting fracture plains but the inclination of its line of intersection is opposite to the slope

Unfavorable:

Wedge failure will take place, if

• There are two or more intersecting fracture plains and the inclination of its intersection line is more than 35° to the slope

• Presence of old slided wedge

• Identify if there are fracture plains facing each other (intersecting)

• Check the inclination of the intersection line• Compare with the condition



Features

Toppling FailureThe rock bank/slope should not have any features of toppling failure.

Condition

Potential toppling failure

Favorable:

Toppling will not take place, if

• the Rock slope is less than 60°

• there is no formation of rock blocks

• there is a formation of rock block but b/h (width of the block/height of the block) is bigger than 1

Toppling Failure Model

Unfavorable:

Toppling will take place, if

• there is a formation of vertically elongated rock blocks in a steep slope bigger than 60° and the blocks are tilted towards the slope

• old toppled rock blocks are present

• Identify if there is formation of vertically elongated rock blocks (cubes) due to vertical and horizontal fracture planes/joints

• Estimate inclination of the slope• Estimate inclination and orientation of the rock block and

compare with the conditions



Features Condition

Translational Failure (Slide)The rock slope should not have any potential of rotational failure.

Favorable:

Translational failure (sliding) of soft rock slope

failure (slide) model

Sliding will not take place, if the

• slope is hard rock

• slope is soft rock but not weathered

• slope is soft rock and weathered but not steeper than 40°

Unfavorable:

Sliding will take place, if

• the slope is highly weathered soft rock and steep than 40°

• back scars or old slide are present

• Identify type of rock and its weathering grade• Estimate inclination of the slope• Compare with the conditions



2 .4 .4 Ev a lu a tio n of th e B r id g e S ite

After completing investigation of the site as per chapter 2.4.1 to 2.4.3, categories the bridge site as

Good All or most of the features are favorable and if the surveyor is confident about thestability of the slopes. Proceed with further survey work.

Bad Most of the features are unfavorable. Reject site.

Questionable Most of the features are favorable and some are unfavorable. The site is questionable. In this case, further detailed investigation by an experienced geotechnical engineer is necessary. For detail refer to the SBD Survey Manual.

As far as possible, the bridge site should be selected at a location where protection works will not be required. If protection works are unavoidable determine the required special structures like retaining wall, drainage channels, etc. A tentative design with dimensions and location of these structures should be illustrated in a sketch showing a plan view and a typical section. But it is best to avoid bridge sites, which require river protection works.

2 .4 .5 C l a s s if ic a t io n o f S o il a n d R o c k

Identification of Soil and Rock types is required for appropriate foundation design. Soil and Rocks can broadly be classified as per the following tables.

Soil Classification

Soil Type How to Identify

Soil ParametersApplicableFoundation

Design

BearingCapacity,

[kN/m2]

Angle of Internal Friction,

<p°

UnitWeight,

Y ,[ kN/m2]

Coarse Grained SoilsMore than half of the materials are of individual grains visible to the naked eye (grain size bigger than 0.06 mm)

GravellySoils

Estimate the percentage (%) of coarse grains larger than 6 mm.If, more than half of the coarse fraction is larger than 6 mm, the soil is Gravelly Soil

400-600(400)

32-38(35) 19

Dea

dman

A

ncho

r

SandySoils

If, more than half of the coarse fraction is smaller than 0.06 mm grain size, the soil is Sandy Soil

200-300(200)

31-37(33) 18

Fine Grained SoilsMore than half of the materials are individual grains not visible to the naked eye (grain size smaller than 0.06mm)

Silty Soils

Prepare moist soil ball from the soil sample and cut it with a knife. If, the cut surface is dull or scratched, the soil is Silty Soil

150-200(150)

30-32(30) 17

Clay

Prepare moist soil ball from the soil sample and cut it with a knife. If, the cut surface is smooth and shiny, the soil is Clay.

1 0 0 -2 0 0(100)

9-25(22) 16



For estimating the percentage (%) of coarse grains use the following figure:

Ratio of coarse grains

12k

2%

• •

IT

# %

3 % % *

k ‘ « i f )

1 * 4 30

n - - - - - - - - - - - - i —* 1 * %

é 1 f « «

% # »»

# * 7 <

* #

* I

a/ » * ^ /o » / f #

' w > '

* : i o

» . « , V » * V

« 4

i % *

W . @

i i â ?

J — «»I i A Ä j'» : * - 1 5 % • - • I

■ âf: A J 5

j_ * ä •[2o%¡ - ? • iA.

f i ; í > > • ___ a _ ■FV « ' *

*«« :m*

♦ i t

5 5 3

Rock Classification

RockType Examples How to

Identify

Degree of Fractures or Weathering

How to Identify

Rock ParametersApplicableFoundationDesign

BearingCapacity,[kN/m2]

Angle of Sliding

Friction,<p°

Har

d R

ock

Quartzite

Limestone

Granite,

Dolomite

etc.

Givesmetallicsoundafterhammerblow

Rock is sound and fresh to fairly weathered

Rock has no sign of weathering or only faint signs of weathering up to 1-5 cm thickness

1500-2 0 0 0

(1500)

35-50(40)

Drum Anchor in Hard Rock

Highlyfractured rock and fresh to fairly weathered

In the rock exists widely open cracks, fractures and bedding

1500 35-50(40)

Drum Anchor in Fractured Rock

Soft

Roc

k

Phylite

Slate

Siltstone

Clay stone

Schist

etc.

Givesdullsoundafterhammerblow

Fresh No sign of weathering 1300 25-40

(30)


Fairly tohighlyweathered

Most of the original rock has been seriously altered Rock can be broken by hand

600-750(650)

25-40(30)

DeadmanAnchor



2 .4 .6 Id e n t if ic a t io n o f S o il a n d R o c k

Excavate a test pit with a depth of up to the estimated foundation level (but not less than 2.0m) or up to the bedrock at the proposed foundation locations. If the bank/slope is soil, investigate each layer of soil in the pit and classify the soil according to the Soil Classification chart, filling in the soil investigation table as per the following example.

Example for Soil

Location: Main Anchorage Foundation at Right Bank

SketchDepth from

Surface, [m]

Soil Type

Soil Parameter

RemarksBearingCapacity,[kN/m2!

Angle of Internal Friction,

<P

/ r 0 7 p \ 0 .0 Top soil

o

' ; ' ; ' ® • ; * o z ~i> r ; *

^ ' y0.3 Sandy Soil

o ' ' ° * *_ - O r . O* O * .- Vo % :

/ . »1.1 Gravelly Soil 400 35 Foundation Design

Parameter

If the bank/slope is rock, investigate the rock type according to the Rock Classification chart, filling in the rock investigation table as per the following example.

Example for Rock

Location: Main Anchorage Foundation at Left Bank

Rock Type Degree ofF racture/Weathering

Rock Parameter ApplicableFoundation

DesignRemarksBearing

Capacity,[kN/m2]

Angle of Sliding

Friction, cp

Hard Rock Highly fractured and fairly weathered

1500 40Drum anchorage foundation in fractured rock



2 .5 T o p o g r a p h ic S u r v e y

After final selection of the bridge site, the surveyor proceeds with the topographic survey. The purpose is to:

• provide a topographic map of the bridge site with details relevant to the bridge design• establish axis pegs and bench marks for use during construction of the bridge

2.5.1 S u r v e y A r e a

Area to be covered by the topographic survey:

For bridges without windguy arrangement,• A profile along the bridge axis covering up to 25m behind the main anchorage blocks.

For bridges with windguy arrangement,• A profile along the bridge axis covering up to 25m behind the main anchorage blocks and a

topographic plan covering the area of 1 0m upstream and 1 0 m downstream from the tentative location of the windguy foundations.

2.5 .2 S e t t in g o f B r id g e C e n t e r l in e

Fix the bridge centerline with two permanent axis points A on the left bank and B on the right bank. Permanent axis points A and B should be fixed on rock out crop along the bridge centerline, if available. If rock out crop is not available, these points should be marked on a boulder sufficiently embedded into the ground as per the sketch below:

Chisdedhole

Additional survey points along the centerline should be fixed to survey the bridge axis profile as shown in the sketch below. These survey points should be fixed at breaking points of slope and terraces, which will accurately indicate the topography of the bridge axis. The profile should cover 25m behind the main anchorage block up to the edge of the river flow.



Draw a sketch of the profile/cross section of the bridge axis (centerline) with axis points A and B, with all the survey points and topographic features, including tentative position of the bridge foundations, low water level and high flood level.

Profile/Cross Section (Example)

Draw a plan view with the bridge axis (centerline), axis points A and B, with all the benchmarks and fixed objects like trees, houses etc. Give distances and directions from the reference points so that the axis points and benchmarks can be located during the construction. A plan view is necessary only when a windguy arrangement needs to be considered in bridge design.

Plan (Example)

FLOOD M A R K

102.20

+

4-

HFL

BM II

P O N M A 1 I-o --O—oTjf--0 — "I 1 —-©--------o----------c -

3-o

4 5 B S T U—■ D---O—j~ ~ •—|~ -(§)----O | | - -1—O ---- O---



2 .5 .3 S u r v e y M eth o d s

There are two options for conducting the topographic survey. Depending upon the span and type of bridge, a profile along the bridge axis or a more detailed survey including contour lines will be necessary.In general Windguy Arrangement is not required for bridges with span up to 120 m.

• A detailed profile along the selected bridge axis is sufficient for bridges without windguy arrangement. A topographic profile can be made by the Abney level, however for fixing precise levels a Level Instrument is necessary.

• For bridges requiring a windguy arrangement a more detailed topographic survey is necessary, from which a detailed contour plan can be plotted. This type of survey should be done by a Theodolite.

2 .5 .4 S u r v ey by A b n e y Level

The main function of the Abney Level is to measure the vertical angle cp. By measuring the slope distance d between the survey points with a measuring tape, the horizontal distance D and the vertical difference of elevation AH can be calculated.

Measurement of Vertical Angle:The principal of measuring the vertical angle by the Abney Level is illustrated in the sketch and

procedure described below:

1 _ Horizontal Distance, D |



The Procedure of measurement is as follows:

1. The Surveyor stands at point A with the Abney level.2. The Assistant stands at the target point C with a stick (or ranging rod). The target mark at the stick,

which the Surveyor sights must be at the same height above the ground as the Abney Level. For this, the height of the ranging rod should be equal to height up to Surveyor’s eye level.

3. The Surveyor holds the Abney Level to the eye and sights towards the target at point C, centering the cross hair against the target.

4. The index arm is then adjusted until the bubble is centered against the target and cross hair.5. When the bubble is centered horizontally and the cross hair is aligned with the target, read the vertical

angle on the arc.

Measurement of Slope Distance d:

The slope distance d between the survey points is measured with a measuring tape. Distances larger than 30m should be divided into sub-distances. The total distance can then be calculated by adding the subdistances. Slope distances should be measured twice and the mean value should be taken as the accurate slope distance.

Calculation of Horizontal and Vertical Distance and Elevations of Survey Points:

Horizontal distance D between a and c D = d x cos (pVertical distance AH between a and c AH = d x sin (pElevation of c H = Elevation of a ± AHAdd +AH, if sighting is upward and subtract -AH, if sighting is downward.

d = slope distance from a to c 9 = vertical angle from a to c

To take the profile along the bridge axis, the Surveyor should first set the exact centerline as described in chapter 3.5.2. There are two methods of setting the centerline.

• By Nylon Rope and Plumb Bob:

This method is accurate only for spans up to 50m. Survey points along the bridge centerline are fixed with the help of a nylon rope and plumb bob.

The Nylon rope is stretched along the axis point A of the left bank and B of the right bank. Care should be taken that the tape or nylon rope is hanging freely and does not touch any obstacles. The survey points are then fixed along this rope with the plumb bob as per the procedures shown in the sketch below:



• By Bamboo or Wooden Sticks or Ranging Rods:This method is applied for span above 50m. In this method the survey points along the bridge

centerline are fixed with the help of Bamboo or Wooden Sticks or Ranging Rods. Fix Stick at each axis point A and B in vertical position. Now the surveyor can aim at other points along the bridge centerline line of A and B. By fixing in line additional survey points behind and in front of A and B, more points can be gained along the bridge centerline ranging as per the procedures shown in the sketch below:

Bridge Axis Profile:Proceed with the survey of the bridge axis profile after having fixed the centerline as per following steps (refer to example on page 31).

1. The survey starts from the fixed permanent axis points A or B and proceeds to other survey points M, N, O, P, 1, 3, 4, 5 or S, T, U, V, 4, 5, 6 (refer example sketch of bridge axis profile below)

2. Measure the vertical angles and slope distances between these survey points of the centerline.It is important that the sighted target is on the same height above the ground as the Abney Level while taking the readings

3. Measure all points M, N, O, P, 1, 2, 3 starting from the permanent axis point A, as described in the second step above

4. Similarly, measure all points S, T, U, V, 3, 4, 5, 6 starting from the permanent axis point B5. Measure vertical angles from A to B and B to A to check the accuracy in vertical angle

readings

Before calculating the horizontal and vertical distances, it is necessary to determine the accuracy of the measurement of the vertical angles. This can be done by comparing the measured vertical angle from A to B with the vertical angle from B to A. Both angle readings should be equal. Differences in these readings indicate an error in the angle measurements and needs correction.

The error factor 4 E’ is calculated with the following formula:[<t?a b 1 — T ^ b a I

E = --------------- ; Corrected angle cp' = cpAB ± E or cp' = cpBA ± E

Example: Error Correction of Measured Vertical Angles

measured vertical angle from A to B measured vertical angle from B to A error factor corrected angle corrected angle

<Pa b = 0°50’ (Downhill sighted) (P b a = 1°30’ (Uphill sighted)E = (l°30’ -0°50’)/2 = 0°20’ <p’AB = 0°50’ + 20’ - 1°10’cp’ e A = 1°30’ - 20’ = 1°10’

All measured vertical angles should be corrected as:Corrected angle cp' = [cp] + E for downhill sighted (-) angles Corrected angle 9 ' = [cp] - E for uphill sighted (+)angles



Compute the horizontal distances and elevations of the corresponding survey points with the corrected vertical angles as per the following example.

Example: Calculation of Horizontal Distance D and Elevation H of Survey Points:

Elevation of Ameasured vertical angle from A to M, (Pamcorrected vertical angle from A to M <P’ammeasured slope distance A to M dhorizontal distance between A and M Dvertical distance between A and M AHElevation of M H

= 1 0 0 . 0 0 m= +7°0’ (upward sighting)= +7°0’- 0°20’ = +6°40’= 13.35 m= d x cos cp’ = 13.35 x cos 6°40’ = 13.26 m = dxsin cp’ = 13.35 x sin 6°40’ = +1.55 m= Elevation of ‘A’ + AH =100.0 +1.55

= 101.55 m

Enter the measurements and calculations into the Abney Level survey sheet as per given example on page 32.

Measuring the River Width:

In certain cases, it might not be possible to directly measure the river width from one bank to another bank by tape. In such a situation, the river width should be measured by indirect method as described in the following example.

How much is the width of the river 1 = Distance from L to R ?

The procedure of the measurement is as follows:

1. Set a base line R - B perpendicular to the line L - R along the river. This can be done easily by 3-4-5 method (refer below: Setting of a Right Angle).

2. On this base line R - B, mark the mid point C so that RC is equal to CB.3. Set again a base line B - A perpendicular to the line R - B similarly to stepl.4. Mark exactly point A by ranging through point L - C, so that all these three points lie in the same line

of sight.5. Measure length B - A. This length will be equivalent to the river width L - R = 1.



Setting of a Right Angle:

One simple method to set a right angle from a point of a base line is the 3-4-5 method. One measuring tape and 3 wooden pegs are needed, as shown in the sketch below:

L

The procedure of the measurement is as follows

1. The first person should hold ‘O’ and ‘ 12’m mark of the measuring tape at point R.2. The second person holds the tape at the 3m mark, and a third person at the 8 m mark of the tape.

Stretch all these sides of the tape as shown in the sketch above. A right angle triangle will be formed with sides of 3, 4, and 5m.

3. Line R - B’ is now perpendicular to the line R - L'.



Bridge Name : Tokre Ghat District: Nawalparasi__________ Surveyed by : Chuda Mani____ Date : 27.11.2055

STATION POrNTSSLOPE

DISTANCEdm

VERTICALANGLE

[Observed]<P

VERTICALANGLE

[Corrected]<p'

HORIZONTALDISTANCE

Dm

VERTICALDISTANCE

REDUCED LEVEL (ELEVATION)

HREMARKS

(Description of Points)+ AH m

A B -0°50' -i°10* Observation for vertical angle error correctionB A +1°30' + l°10'

A 100.00 Datum Level (Assumed)M 3.35 +7°20' +7°0* 3.32 + 0.40 100.41N 8.00 +6°20’ +6°0' 7.95 + 0.84 100.840 13.00 + iio0' + 10°40' 12.77 + 2.40 102.40P 17.25 +13°0* + 12°40' 16.83 + 3.78 103.781 4.20 -23°40' -24°0' bo 4 - 1.70 98.303 27.50 -18°40' -19°0' 26.00 - 8.95 91.05 HFL= Ela+l.Om4 34.90 -19°40' -20°0' 32.80 - 11.94 88.065 47.30 -15° 10' -15°30' 45.58 - 12.64 87.36 Water Level (WL)

B 98.673 41.80 -10°10' -10°30' 41.10 - 7.62 91.058 12.40 -19°40' -20°0' 11.65 - 4.24 94.43S 2.80 + 19°30' +19°10' 2.64 + 0.92 99.59T 5.45 +14°40' +14°20' 5.28 + 1.35 100.02U 15.20 +23°30' +23° 10' 13.97 + 5.98 104.65

3 91.052 17.00 + 1°50' -j-1°30* 17.00 + 0.44 91.49B 41.80 +10°50' +10°30' 41.10 + 7.62 98.67



2.5.5 S u r v ey B y T h e o d o lite

When the span of the bridge is more than 120 m or when a windguy arrangement needs to be included in the bridge design, the survey is conducted with a theodolite.

For proper use of a theodolite, refer to the respective instruction manual that comes with the theodolite and to the SBD Survey Manual.

Profile Along Bridge Axis:Fix the bridge centerline as described in chapter 2.5.2. Measure the distance between the axis points A

and B by horizontal triangulation method. Triangulation is done by measuring all three angles of a triangle and length of one side, as illustrated in the sketch below and in the example given on page 33.

C

For accuracy double triangulation is necessary. The procedure is:

I st Triangulation1. Set out a peg at C in such a way that the distance B - C can be easily measured. The length ‘d’ should

be at least 20% of the distance A - B2. Measure distance B - C = d accurately with a measuring tape. Measure this distance several times and

calculate the mean distance.3. Set up theodolite at B and measure the horizontal angle Z ABC = P from face left and face right4. Set up theodolite at C and measure the horizontal angle Z ACB = y from face left and face right5. Set up theodolite at A and measure the horizontal angle Z BAC = a from face left and face right6 . Sum up these angles (S=P+Y+a), which should be theoretically equal to 180° or 2008. If, the sum is

not equal to 180° or 200g, the difference A should be equally distributed to all the three angles so that the sum becomes 180° or 2 0 0 8

d x s i n /7. Calculate distance A - B = D with the trigonometric formula, D = -----------

s i n p

IInd Triangulation

1. Repeat the same procedure as above and calculate distance A - B = DfD + D’

2. Calculate final distance D = ----------2

Use the standard form “Triangulation” for recording the readings and calculation given in the example on page 34.


Exam

ple:

TR

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Elevation of Axis Points and Benchmarks:

It is necessary to establish the elevations of the Axis Points A and B and Benchmarks. This is done by vertical triangulation as shown in the sketch below and as per example given on page 36.

The procedure is as follows:

1. Select a first Bench Mark BM I on a rock or big boulder near to the axis point A and fix it as 1 0 0 .0 0 m

2. Select bench mark BMII near to the axis point B

3. Measure the horizontal distance D from A to BMI accurately with a tape

4. Measure the horizontal distance D from B to BMII accurately with a tape

5. Take the distance D between axis points A and B from the triangulation (refer to previous chapter)

6 . Set up the theodolite at the axis point A and measure the vertical angle to axis point B and the vertical angle to BM I. Take the middle hair reading Z and measure the instrument height I.

7. Set up the theodolite at the axis point B and measure the vertical angle to axis point A and the vertical angle to BM II. Take the middle hair reading Z and measure the instrument height I.

8 . Set up the theodolite at BM I, measure the vertical angle to axis point A. Take the middle hear reading Z, and measure the instrument height I.

9. Set up the theodolite at BM II, measure the vertical angle to axis point B. Take the middle hair reading Z, and measure instrument height I

10. Calculate the followings for all readings:

Vertical Distance V = D x tan cp or V = ———tan (5

Elevation difference AH = V - Z + I for upward vertical angle readingAH = V + Z - I for downward vertical angle reading

11. Calculate Elevations of A, B, BM I and BM II, starting from BM I to A to B to BM II

Elevation of A = EL of BMI ± AHElevation of B = El. of A ± AHElevation of BMII = El. of B ± AH

Insert the readings and the calculations in the Survey form of “Summary of Triangulation and Elevations of Pegs and Benchmarks” as per example given on page 36.


Chapter 2: Survey and Bridge Site Selection

asExample:SUMMARY of TRIANGULATION and ELEVATIONS of PEGS and BENCHMARKSBridge Name : /<o//>no District : AcAAa^n, Surveyed by : A . a/. Date : /Vtz-cA /???1. Summary of Triangulation 2. Elevation

V = D x tan cp = Dtan ß

AH = V- Z + I

AH = V + Z - 1

Is Triangulation Dj 2 'ki 'Triangulation D: =Difference AD _

Mean Distance D = P i+^ 2

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Volume 1


Topographic Detail Survey:

The topographic detail survey is necessary to represent the topography of the bridge site by means of a map (plan) with the contour lines.The topographic detail survey uses the tacheometric method. Tacheometric survey is done by Theodolite with stadia hairs (having constant value of 100) and leveling staff.

Checking the Stadia Hair:

Check the stadia hair of the theodolite before doing the detail survey by tacheometry. For this, measure a distance of about 40 m using stadia readings and compare them with actual tape measurements. If the difference between the stadia measurement and the tape measurement is more than 0.2%, calculation of horizontal and vertical distance needs to be corrected. The distances should be corrected for error A as per following Formula.

D = (100/ ± A) x cos2 (p V = (50/ ± A) x sin2$>

A is calculated before the survey as per following procedure:

1. Put the theodolite on horizontal ground and level it2. Level the telescope of the theodolite so that the vertical angle is 03. Put pegs at approximate distances of approx. 10, 20, 30, 40 and 50m4. Measure accurately the distance between the vertical axis of the theodolite and the pegs by tape5. Take the stadia hair readings by theodolite at each peg6 . Calculate the horizontal distance to each peg by tacheometric calculation7. Determine the difference (error) between the tape measurement and the tacheometric measurement

for each peg8 . Plot the graph for A correction

Example: A - Corrections

Top hair Bottom hair Difference Distance Tape Measurement Correction1. h 1 = li- h D’ = lx 100 Distance, D A = D - D’

(cm) (cm) (cm) (m) (m) (cm)

118.70 108.30 10.40 10.40 10.48 + 8

135.90 114.20 21.70 21.70 21.87 + 17140.75 109.80 30.95 30.95 31.33 + 38160.25 118.05 42.20 42.20 42.66 + 461 2 0 .2 0 66.45 53.75 53.75 54.36 + 61

+

The graph is used for the calculation of the tacheometric error for the horizontal distances

Distonce(m)

D1 = 1004



Tachometric Survey:

All topographic details are taken by the tacheometric survey. Tachometric details are mainly taken from the axis point A and B (theodolite stations). If the area of survey cannot be covered by these two points, details should be taken from other additional points. The survey points (staff points) should be taken at break points of slopes, terraces, fields and other features representing the actual topography of the ground as shown in the sketch below. Survey points should also include other details such as houses, trees, foot trails, rocks, river banks, high flood level, water level at survey time etc.

The procedure of survey is:1. Set up the theodolite on the axis point A. Measure the instrument height I2. Fix the 0 reading of horizontal circle along the bridge axis towards B as illustrated in the following

sketch

3. Take for every survey point (staff point) the readings of the horizontal circle, the vertical circle, the top hair, the middle hair and the bottom hair, after proper sighting to the respective survey points, as illustrated in the sketch of step 2 above and the sketch below.


Vertical Angle, ß = 948 06c Horizontal Angle a = 2148 97c

Top Hair, l \ =2.455 Bottom Hair, 1/2 = 1.844 Middle Hair, Z =2.15

Volume 1

4. Record the readings into the “Tacheometry ” survey sheet as shown in the example on page 40.5. Set up the theodolite on the axis point B. Measure the instrument height I.6. Fix the zero reading of the horizontal circle along the bridge axis towards A.7. Take the details, which were not covered from axis point A, following the procedure from step 3-4.8 . Calculate the horizontal and vertical distances and elevations of the survey points with the help of the

tacheometric formulas given in the “Tacheometry” survey sheet as shown in the example on page 40.

2.5 .6 T o p o g r a p h ic Ma ps

As per the field survey data, it is necessary to prepare the following topographic maps in the scale 1 :1 0 0 or 1 :2 0 0

• Profile along the bridge axis• Contour plan of the bridge site in scale (only when windguy arrangement is necessary)

Profile Along the Bridge Axis:Plot the profile along the bridge axis as per following steps (refer the example of the plotted bridge axis profile given on page 41).

1. Choose the scale of the drawing. Vertical and horizontal scale should be the same.2. Choose the datum level so that the points with lowest and highest elevations are within the drawing

area.3. Choose the position of the axis point A so that most farest survey point of Right Bank and left bank

from the axis point A are within the drawing area.4. Plot the axis point B as per its elevation and horizontal distance from axis point A.5. Draw the survey points of the bridge axis according to the horizontal distance and elevations as per

the data from the “Bridge Axis Profile by Abney Level” survey sheet or the “Tacheometry” survey sheet from axis point A. Refer also to the sketch of the bridge profile prepared during the field survey.

6 . Similarly, draw the remaining survey points of the bridge axis from axis point B.7. Join all the survey points by straight lines. This will represent the bridge axis profile.8 . Draw horizontal lines with the elevation of the high flood level and the water level at the time of

survey.

Contour Plan of the Bridge Site:The contour plan represents the overall topography of the bridge site by means of contour lines. A

contour line is a continuous line passing through points of equal elevation.A contour plan is necessary only when a windguy arrangement is to be considered in the bridge

design. In most of the cases of short span trail bridges, windguy arrangement will is not necessary, and a contour plan is not required for bridge design.

The method of plotting a detailed contour plan is not discussed here. For further information, refer to topographic survey books or the SBD Survey Manual. A sample of a contour plan is presented on page 42.


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2 .6 P h o t o g r a p h s

Photographs of the bridge site to support its technical feasibility / topography and facilitate the bridge design.

Take the following photographs:

• An overall view of the bridge site from upstream indicating approximate location of bridge foundations and the axis line

• An overall view of the bridge site from down stream indicating approximate location of bridge foundations the axis line

• View of the right bank from left bank with an approximate location of bridge foundations• View of the left bank from right bank with an approximate location of bridge foundations• An overall top view (if possible)• A close up view of the axis points and the bench marks• A view of the soil test pits at the location of the bridge foundation blocks• Other relevant photos

Take above photographs from the positions as per sketch below. If one picture does not cover the necessary area, take several pictures from the same spot with sufficient overlapping.

Present all the photographs systematically with respective captions.

2 .7 S u r v e y R e p o r t

The technical survey report consist of:

• Filled in Survey Forms and Checklist• Topographic map

1. Profile along the bridge axis in scale2. Contour plan of the bridge site in scale (only if windguy arrangement is necessary)



3. B r id g e D e s ig n

3.1 B r id g e T y p e s

There are basically two types of cable bridges developed in trail bridge standard, which are:

• Suspended Bridge Type

• Suspension Bridge Type

The selection from above bridge types depends mainly on the topography of the bridge site.

Suspended BridgeThis type of bridge has downward sagging walkway. Sagging walkway cables are suspended below

their anchorage. Cables are anchored in to the main anchorage foundation at both banks. The main components of this bridge are: Walkway cables and Handrail cables, Walkway system and Main anchorage foundations.

This type of bridge is selected where the bridge foundations can be placed at sufficiently high positiongiving required free board from the highest flood level.

Suspended type is more economic, simple to design and construct than suspension type bridge.

w follow Form No. 2Bridge Design Form

A suspended type bridge

The present handbook deals only with suspended type bridge.

Chapter 3-.Design 45


Suspension BridgeThis type of bridge has upward cambered walkway. Main cables are hanged over the towers and

anchored to the main anchorage foundation. Walkway cables are anchored to the pylon foundations. The main components of this bridge are: Main cables and Walkway cables, Towers, Walkway system, Main anchorage foundations and Pylon foundations.

This type of bridge is selected when the bridge site is comparatively flat terrain and suspended type bridge is not feasible due to the constraint of free board.

Suspension type Bridge is more expensive and needs more inputs to design and construct than suspended type.

A suspension type bridge

The present handbook will not deal with suspension type bridge. •

• Layout and SectionsThe typical Plan and Profile of a suspended type bridge is given in the next pages.

46 Chapter 3:Design

Chapter 3:Design

PEDESTRAIN SUSPENDED BRIDGE Typical Profile

ROCK SOIL


Volume

PEDESTRAIN SUSPENDED BRIDGE Typical Plan


• Walkway Section

There are two types of walkway width:70cm & 106cm

3 .2 B a s ic D e s ig n C o n c e p t

3.2.1 Lo a d in g s

For designing a bridge structure loadings as per LSTB standard (former SBD standard) is followed. Following are the probable loadings according to this standard.

• Live loadLive load for smaller span up to 50m is equivalent to 400 kg/m2 and for longer span as per formula,

P =300 + 100-— k g / m 2or kN / m 2t e

• Dead loadDead load includes the weight of all permanent components of the bridge structure. •

Width of Walkway 34 cm 70 cm 106 cm

Dead Load (without weight of Handrail- and Walkway Cables)

25 kg/m or 0.25 kN/m



• Wind LoadThe design wind load is taken as a uniformly distributed load based on a wind speed of 160km/h

acting horizontally to the walkway. This corresponds to a wind pressure of 1.3 kN/m2 acting on the lateral bridge area of 0.3 m2 per meter span. By maintaining a wind coefficient of 1.30 (ace. to Swiss Standard) the actual lateral design wind load is 0.50 kN (1.3 x 1.3 x 0.3) per meter span. The foundation structures are sufficient to resist this design wind load.

Wind load affects also the dynamic behavior of the bridge. However, practical experience has proven that bridge-spans of up to 120 m, no significant dynamic effects due to wind load has taken place. For minimizing dynamic wind-effects on the bridge sufficient dead load, a steel deck and most favorable span to sag ratios have been introduced. Therefore, no lateral stabilizing measures (windguy system) is considered in this standard suspended bridge design. However, for special cases (spans more than 120m or extreme windy areas exceeding wind speed of 160km/h) there is a provision for fixing a windguy system.(See also ’’Expertise on Windguy Arrangement for BBLL Standard Bridges by Dr.Heinrich Schnetzer, WGG Schnetzer Puskas Ingenieure AG SIA/USIC Basel, Switzerland, and para 3.3.6 A Windguy Arrangement.)

• Snow Load

The probability of occurrence of a full load on a bridge loaded with snow is low. Moreover, the design live load itself is comparatively high. Therefore, it is considered that the snow load is already covered by the design live load.

• Temperature effectLoading (cable forces) according to temperature effect is negligible in comparison with other loading conditions. Therefore, temperature effect has not been considered for the standard bridge design.

• Seismic LoadThere is low probability of a full live load occurring at the time of an earthquake. Moreover, the design live load itself is comparatively high. Therefore, it is assumed that the seismic load is already covered by the design live load. A separate loading combination with seismic load is not considered.

Chapter 3:Design 49

110

cm


3.2.2 C o n s t r u c t i o n M a t e r i a l s

The construction materials used for the standard trail bridges are wire ropes (cables), steel parts, steel fixtures and fasteners (thimbles, bulldog gripes, nuts and bolts), concrete and stone masonry. Specifications of these materials are based on Indian Standard (IS). Refer to Volume A of SBD Manual for detail material specifications. However, for frequently referred material, specifications are given below for quick reference.

• Steel Wire Ropes (Cables)For more convenient stock keeping, handling and transportation only three cable diameters are applied. This also reduces the number of steelparts, logistics and eventually bridge costs.

Steel wire ropes should comply with all the requirement of:

IS 1835 - 1977 IS 6594- 1977 IS 9282- 1979 IS 9182 (part II)-1979

Steel wires for ropesTechnical supply conditions for wire ropes and strands Specification for wire ropes and strands for suspension bridges Specification for Lubricants for Wire Strands and Ropes

Nominal diameters: 13 mm 26, 32 mm

Rope Construction Elongation - Lay CoreTensile strength of wire Preforming Coating Impregnation

7 x 7 (6/1) 7 x 19(12/6/1)non pre-stretched pre-stretched

RHO, right hand ordinary lay WRC, Wire Strand Core 160 kg/mm2 or 1.57 kN/mm2

PreformedGalvanized ‘A’ heavyNon-drying type and non-bituminous Lubricant

Nominal Diameter of Cable

mm

Weight kg/m N/m

Metallic Area [mm2]

Minimum Breaking Load in

Tones kN

Permissible load in

Tones kN132632

0.64 6.3 2.51 24.6 3.80 37.3

73292442

10.5 103 39.3 38659.6 585

3.5 34 13.1 129 19.9 195

Modulus of Elasticity, E = 110 kN/mm2 = 11 t/ mm2

S T R A N D

C O R E

C O N S T R U C T IO N

12 W IRES O U T S ID E 6 W IR E S IN T E R M E D IA T E 1 W IRE AS CORE

W IR E S T R A N D

RIGHT HAN D LAY

D IR E C T IO N OF Z

Cross-section and Lay of Wire Rope

50 Chapter 3:Design


• Bulldog GripsBulldog Grips are used for cable terminal to secure the cable ends.

Bulldog grips should conform to IS 2361-1970, specifications for Bulldog Grips. The bridges must be dropforged and suitably scored to grip a round strand rope of right hand lay having six strands. Bridges, U-bolt and nuts should be hot dip galvanized with minimum zinc coating of 40pm. The size of the bulldog grip is equal to the size of the cable to be anchored or connected.

The methods for applying Bulldog Grips to Wire Ropes at different terminals are given in Chapter6.6.3 Bridge Construction.

• Structural SteelSteel grade should be of standard quality Fe 410 and structural steel should comply with the requirement of:

IS 226 - 1975 Structural SteelIS 800 - 1984 General Construction in Steel

The steel should have the following mechanical properties :

Tensile Strength > 410 N/mm2

Yield Stress > 250 N/mm2

Modulus of Elasticity = 200 kN/mm:Elongation > 23%

• FastenersBolts, nuts and washers should be of grade C, property class 4.6 and should comply with the requirement of:

IS 1363 - 1984 (Part 1) Hexagonal Head Bolts and Nuts IS 1367 - 1983 Threaded Fasteners

All the fasteners should be hot dip galvanized with minimum zinc coating of 40pm.

• Reinforcement SteelReinforcement Steel should be of steel grade Fe415, high yield deformed bars and should comply with the requirement of:

IS 1786 - 1985 High Strength Deformed Steel Bars for Concrete ReinforcementIS 456 - 1978 Plain and Reinforced Concrete

The Reinforcement Steel should have the following mechanical properties :

Yield Stress = 415N/mm2Modulus of Elasticity = 210 kN/mm2

Chapter 3:Design 51


• Rust PreventionRust prevention of steel parts should be done by Hot Dip Galvanization according to:

IS 2629 - 1966 Recommended Practice for Hot Dip Galvanization of Iron and Steel IS 4759 - 1984 Specification for Hot-Dip Zinc Coating on Structural Steel

ProductsMinimum Mass of Coating

g/m2 N/m2Minimum Thickness of Coating

pmStructural Steel 610 6.0 80Threaded work, Nuts and Bolts 300 3.0 40

• Wire Mesh NettingWire for wire mesh netting should comply with the requirement of:

IS 280 - 1978 Mild Steel Wire for General Engineering PurposesIS 4826 - 1979 Hot-dipped Galvanizing Coatings on Round Steel Wire

Diameter of wire should be 12 SWG (2.64mm) and zinc coating should not be less than 270 g/m2. The average tensile strength of the wire should not be less than 380N/mm2.

• ConcreteConcrete should comply with all the requirements of:IS 456 - 1978 Plain and Reinforced Concrete IS 269- 1989 Ordinary Portland Cement IS 383 - 1970 Coarse and Fine Aggregate

Concrete Grades used in the standard design are:

Concrete 1:3:6 (M10) for miscellaneous useConcrete 1:2:4 (M15) for structure

• MasonryMasonry should comply with all the requirements of:

IS 1597 - 1967 Code of Practice for Construction of Stone MasonryIS 2250 - 1981 Preparation and Use of Masonry Mortars

Stone masonry used in the standard design are:Chisel Dressed Stone Masonry in 1:4 cement: sand mortar Hammer Dressed Stone Masonry in 1:6 cement: sand mortar Dry Stone Masonry.

• Unit Weight of Construction MaterialsThe unit weight of the construction material used in the standard design is given in the following table.

Materials Unit Weight, kg/m3 kN/m3

Concrete 2200 22.0Stone Masonry 2100 21.0Steel 7850 78.5Soil 1800 18.0Water 1000 10.0

52 Chapter 3: Design


3.2.3 St r u c t u r a l A n a ly s is A nd Design

Statical analysis is based on calculation of forces and stresses in the structures due to the external loadings. Calculated forces and stresses are compared with the permissible loads and stresses of these structures with some safety of factors.

The standard suspended bridge has been designed as per the following statical analysis and basic design concept.

• Cable DesignA cable hanging between two supports and carrying a uniformly distributed load “q” forms a

parabola. Thus Main Cables and Walkway Cables are assumed to be of parabolic geometry. In suspended type bridge, the main cables (walkway cables) and handrail cables carry the load equally proportional to their sectional area.

The following sketch represents the cable geometry and forces on it.

=> Maximum permissible Height Difference of Walkway Cable Saddles,

=> Sag of the Cable at Midspan in Dead Load for Spans up to 80m:

or for Spans over 80m:

The fundamental equations for the calculation of the cable forces are:

=> Total Horizontal Tension,

=> Total maximum Tension at the higher Foundation Saddle,

=> Cable Inclination at higher Foundation Saddle,

Example: ß max - a tan 4 2 2 + 25 0.1818-1 + 0.041——— — = a tan----------------------

h =

b =

b =

Span (£ )25

Span ( l )To

Span (£) ~22

H = g-8 6

T =A maxH

C O S P n

ß m a x = a t a " ( -----7 ~ )

= a tan 0.2218 = ß max = 12.51c

The Safety Factor for Cable Breaking Load is taken as fs > 3.Chapter 3:Design 53


As per above design concept, a simplified cable combination chart has been developed and standardized for suspended type bridge for different walkway width and span up to 120m.(refer to Table: Selection of Cables in Chapter 3.3.4 B).

These cable combinations depend only on the span and the chosen walkway width and do not depend on the site condition. The cable combination has been designed to satisfy the worst topographic condition, i.e. considering maximum allowable level difference between the cable saddles of right and left banks. Therefore, in more favorable topographic conditions, the cable may seem to be over designed, but, as per analysis this has no significant effect (less than 1%) on the over all cable strength.

• Steel PartsSteel parts of the suspended type bridge are mainly subject to axial tension, bending stress, shear

stress and bond stress. All the steel parts are designed for these forces and stresses with a safety factor of fs = 1.6.

All the steel parts have been standardized according to the cable combinations and do not depend onthe site condition.

• Walkway StructureWalkway structures (Steel deck, Cross beams, hangers) are designed for local loadings as steel parts

with safety factor of, fs = 1.6. Concentrated load P = 150 kg (weight of a porter with load) positioned along the walkway as well as across the walkway has been considered as per sketch below.

2 porters passing each other (P = 1.5 kN) walkway deck

Porters standing in row (P = 1.5kN)

• Main Anchorage FoundationsThere are mainly three basic types of main anchorage foundations:

=> Foundation on Soil

=> Foundation on Hard Rock

=> Foundation on Fractured Hard Rock or Soft RockAll foundations are designed as per the static analysis and principle of soil / rock mechanics. Soil and

rock parameters are determined by the site investigation (refer chapter 2.4.5 and 2.4.6). Following mode of failure and respective safety factors are considered in the design:

=> Sliding FSl ^ 1-5

=> Toppling Ft >1.5

=> Bearing Capacity FBc ^ 2.0

=> Maximum Ground Pressure a max < Bearing capacity of soil or rock

The standard design is without windguy system (refer chapter 3.3.6 for details). Therefore, foundations are designed to take the wind load satisfying the worst case from the following two load cases.

=> Load case A = dead load + full wind load

=> Load case B = full load + 1/3 wind load

54 Chapter 3:Design


• Foundation in Soil

RCC deadman and gravity soil anchor block has been designed as a main anchorage foundation on soil. The design concept of the foundation is given below.

The foundations have been designed to satisfy the safety against sliding with the following theoretical basis.

Safety factor against sliding:Re sistingForce DrivingForce

R ’v J a n ç s , ^ ] 5

R H

Where, R'v = Rv • cosa + Rh • since Ry = W, + W2 + ...+ Wn + Eav - TvR'h = Ry • since + Rh • cosa RH = T H+Eah

The gravity load has also been maintained to resist the uplift force at the dead man beam by providing minimum width (B |mjn) and height (Hlmin) as demonstrated be1""'

B ] min

Safety against uplifting:

Tmax • sina = (b+Blmin)-0.5Hlmin -Lb«*,,,H 1 mil

Bimm = b + Hlmin • tan30°Deadman Beam

The position of the foundation behind the slope line of the internal angle of friction guarantees the safety against the Ground Shear failure.

Further, a curtain wall with cement stone masonry of sufficient thickness has been provided to resist the lateral pressure and bulging effect. The lateral pressure has been calculated as lateral pressure against rigid wall as per elastic theory with the following formula.

Distribution of lateral pressure a z along B

Chapter 3:Design 55


• Foundation in Hard RockRCC C oncrete D rum w ith rock anchoring is used for foundation on sound hard rock. The sizes o f

drum and anchorage rods are designed to w ithstand the shear due to the horizontal tension o f the cables. It is also designed to resist the uplift force at Drum .

R equired num ber o f anchor rods, N is calculated as:

_ Tmax • cos aA S t ~

^ perm

N =n -d

or N =® Bperm

■ sin a • TC • d • t

N is adopted from w hichever is h igher from above.

Vmax Tmax

Hmax

• Foundation in Fractured Hard Rock or Soft RockD rum anchorage w ithout rock anchoring is used for foundation on fractured hard rock o r fresh soft rock.

The size o f drum is designed to w ithstand the shear failure due to horizontal tension o f the cables.The D rum size and num ber o f re inforcem ent bars are determ ined as follow s.

f■ Tc + Ast ■ Tst = Tm ax-c o s a

Required number o f anchor rods, N is calculated as:

N = 4 Ast K - d 2

Tmax

Hmax



• Stone Masonry TowerStone M asonry T ow er is designed to be safe against overturn ing and m axim um pressure on foundation. The ground bearing capacity (shear failure) is contro lled by p lacing the tow er foundation behind the critical slope line (see chapter 3.3.3, Step 1 for case 1& 2).The design concept is as show nin the fo llow ing sketches.

Forces on top of the Tower:

Tb — T f- pVx => Vj' — V ~ l b

H t = T f -cosß - Tb-cosa ju=0.

T _ T ( l - f i f(l + u s i n a )

tanSR II

cos SR

Anchor SideHt

Forces at Tower Base and Soil Pressure

Safety factor against overturning:

r _ All Re sisting Moments _ 2M^j ^ r cr yyf — — — - i • o

All Driving Moments AM“

Z M A =(V r X1 + V2-X2 + V 3-X3 + ...+ Vt -X )

ZM~a =( Ht -Y)

m A = m A + z m a

Safety against Ground Bearing Pressure:E ccentricity should be w ith in the perm issib le lim it so that there is no negative pressure on the foundation. It is achieved by m eeting the follow ing condition.

5*/2 = : ^ - > 5/32.Rv

W here, Ry = Wi + W 2 + . . .+ W n + Vx I M a = X M +- I M '

G round B earing P ressure should be less than the B earing C apacity o f the soil/rock. It is calculated as:

CL

Rv R i

B*/2 I e I B/2 B

• Reinforced Concrete WorksAll the reinforced concrete w orks are designed as per the p rincip le o f RCC design in w ork ing stress. For detail refer to the relevant literature o f R einforced C oncrete design.

Chapter 3:Design 57


3 .3 D e s ig n o f S t a n d a r d S u s p e n d e d B r id g e

3.3.1 T he M a j o r B r id g e C o m p o n e n t s

The sketch below shows the major bridge components and parameters.

lower foundation higher foundation

3 .3 .2 D e s ig n P r o c e d u r e

For designing a suspended standard bridge, follow the steps in sequence as follows: •

• Draw the bridge profile from the survey data

• Fix the position of the bridge foundations and the span

• Select walkway width

• Select walkway cables and handrail cables from Design Form No. 2 (Volume II)

• Design walkway tower

• Design main anchorage foundations

• Transfer data to the bridge profile and prepare the General Arrangement Drawing

• Compile and fill in the standard design drawings

• Calculate the quantities of works and prepare the Cost Estimate

58 Chapter 3:Design


3.3.3 D es ig n in g th e Po s it io n of th e B r id g e Fo u n d a tio n s

Fix the position of the bridge foundations and the actual span of the bridge in the bridge profile. This bridge profile will be the basis for the layout of the bridge at the construction site. Fulfill following criteria while fixing the position of the bridge foundations.

Criteria for fixing the Biridge Foundations

• The Bridge Foundations should be placed at least 3 meter back form the soil slope and 1.5 meter back from the rock slope

• The Bridge Foundations should be placed behind the line of angle of internal friction of the soil or rock. This angle is 35° for soil and 60° for rock.

• Level difference between the walkway cable saddles of two banks, h should not be more than span/25

• Walkway tower height should be as small as possible. However, walkway cable saddle should be at least a height of 1.3 meter from ground but should not be at a height more than 3.0 meter.

• Free board F, between lowest point of the bridge in dead load case and the high flood level should be not less than 5.0 m

Criteria for fixing the location of the bridge foundation

Procedure for fixing the Bridge Foundations

According to the above criteria, draw the bridge profile as per following steps.

• Draw the bridge axis profile on an A3 size paper in a scale 1:200 (for up to 50m span) or 1: 400 (for span above 50m) with all details like axis points A and B, HFL, WL and tentative location of the walkway towers at both banks based on the survey data as described in the chapter 2.5.6. •

• Fix location of the walkway towers at both banks as per following procedure.

Chapter 3:Design 59


Case-1: When Tentative Position of the Towers has been fixed during the Survey.Step 1: Fix the Front of the Tower and check with Slope Line.Mark front of the tower as fixed during the survey. Check position of the front of the tower as per minimum required distance from bank edge and slope line.If minimum required distance from bank edge is not sufficient, shift its position backward.Towers should be located behind the slope line. If tower is out of the slope line, shift its position backward.

Survey

Step 2: Fix the Position of the Walkway Saddle and Bridge Span, l.Mark position of the walkway cable saddles. Walkway cable saddles should be at height of 1.3m at soil slope and 0.8m at rock slope from the ground at tower front. Thus, fix its elevations, Ei, Eh & l.

min.3.00m

max

Location of Front

of Tow er Foundation

fixed during Survey

Step 3: Check the Level Difference, h.Level difference ‘h’ between walkway cable saddles of two banks should be less than //25. If ‘h’ is found more than the limit:Rise the elevation of the walkway cable saddle of lower bank by increasing saddle height (in the series of 1.3, 2.3, 3.3 meter) but not more than 3.3 meter from the ground level in case of hill slope

OrShift the position of the tower of lower bank backward to gain the required walkway cable elevation in case of flat ground. OrLower the elevation of the walkway cable saddle of higher bank. Avoid deep earth cutting.

Walkway Cable Saddle

Center Line , of Walkway > Cable Saddle

h = E^v - Ei < 1 /2 5

h i --------------

X7 HFL

\7 W L

Walkway Cable Saddle

60 Chapter 3 .Design


Case-1: (continued)Step 4: Calculate the vertical Distance, fmin and check the Free Board, fb.Calculate vertical distance fmjn between the lowest point of the bridge and walkway cable saddle of lower bank,

f m in(4 • l -

320 - I

Draw line of lowest point of the bridge.

Check available free board between lowest level of the bridge and high flood level.

Freeboard should be not less than 5.0m. If free board is not sufficient:Raise the elevations of walkway cable saddles at both banks. This can be done either by raising the tower height in case of the flat ground or by placing the tower further back in case of the hill slope.

Step 5: Finalize the Bridge Profile.Finalize bridge profile with final span and elevation of the walkway cable saddles.

Chapter 3 Design 61


Case-2: When the Position of the Towers has not been fixed during the Survey.

Step 1: Fix the Free Board Line and Front of the Towers.Mark minimum free board level. Minimum free board from high flood level is 5.0 meter.Fix the position of the front of the tower maintaining minimum required distance from bank edge and slope line.

Step 2: Fix the approximate Bridge Span, / and minimum Level of Walkway Cable Saddles.Calculate approximate bridge span as distance between the tower fronts.

£Mark minimum level of walkway cable saddles as per required sag of the cable, b = —

Step 3: Fix the Position of the Walkway and Cable Saddles.Walkway cable saddles should not be below the minimum level.Walkway cable saddles should be 1.3 meter above the ground level at soil slope and 0.9 meter at rock slope.

Thus, fix the elevations of the walkway cable saddles, Ei and Eh.

62 Chapter 3:Design


Case-2: (continued)Step 4: Check the Level Difference, h.Level difference ‘h’ between walkway cable saddles of two banks should be less than U25. If ‘h’ is found more than the limit:Rise the elevation of the walkway cable saddle of lower bank by increasing saddle height (in the series of 1.3, 2.3, 3.3 meter) but not more than 3.3 meter form the ground level in case of flat ground.

orShift the position of the tower of lower bank backward to gain the required walkway cable elevation in case of hill slope. orLower the elevation of the walkway cable saddle of higher bank. Avoid deep earth cutting.

Step 5: Calculate the vertical Distance fmIn and check the Free Board fb.Calculate vertical distance fmjn between the lowest point of the bridge and walkway cable saddle of lower bank.

Draw actual line of lowest point of the bridge f min 320

Check available free board between lowest level of the bridge and high flood level.

Freeboard should be not less than 5.0 meter. If free board is not sufficient:Raise the elevations of walkway cable saddles at both banks. This can be done either by raising the tower height in case of the flat ground or by placing the tower further back in case of the hill slope.

Finalize bridge profile with final span and elevation of the walkway cable saddles.

Chapter 3:Design 63


3.3.4 Cab le D esign

Designing the cable for a bridge involves selecting required numbers and diameter of the handrail and walkway cables for given span and selected walkway width.To design the cable proceed as per the steps below.• Select the appropriate walkway width (70cm or 106cm) according to the nature of the traffic

and type of trail, (refer to Survey Form and Check List)

• Fix the span of the bridge and height difference of cable saddles of the right bank and left bank from the bridge profile (refer chapter 3.3.3).

• Select cables from the Table: Selection of Cable according to the span and selected walkway width.

Design the Cable Structure as per following Checklist

A. Survey Data & Calculation of Freeboard

m

m

m

m

m

m

m

m

m

1. Span of the Bridge

4. Difference in Elevation(max. permissible height: hmax = U25)

5. Dead Load Sag: fo r Span up to 80m

fo r Span over 80m

6. f „,¡0 in Dead Load Case(at the lowest point of the cable)

7. Highest Flood Level

8. Free Board (min. 5.00m)

f .

£

the higher Side Eh

: the lower Side E,

h =Eh - E* h

* - * - - 20

bd

* - * ■ - 22

bd

(4 bd -h )2 16 bd

f . *111111

h f,

E/ - Hpi - f min = Fb

( i f freeboard is less than 5.00m, try either to raise the sadd le elevations or to adjust the span, but keep the ratio between span and sag alw ays fixed at / / brf =20 or / / b =22 )



B. Selection of CablesSelect a cable combination according to the span and walkway width of the bridge from the following table. Always select the higher cable combination when the span is in between two values.

Maximum Span for Cable Combinations Weight of allWalkway Width: Handrail Walkway Cables

70cm 106cm Cables Cables §hspan [m] span [m] nos 0mm nos 0mm [kg/m]

50 40 2 26 2 26 10.04

90 60 2 26 2 32 12.62

100 75 2 26 4 26 15.06

120 105 2 26 4 32 20.22

120 2 32 4 32 22.80

C. Calculation of Cable Length

Type of Cable dia[mm] Nos Backstay Length *

[m]Cutting Length**

[m/pc]

Fixation Cable 13 2

Handrail Cable 2

Walkway Cable

* Backstay Length = Cable length between saddle center and center of dead man or drum as per foundation drawing(both banks) + 6.0m.

**Cutting Length = 1.1 x Span + Backstay Lengths

D. Calculation of (fmin) Hoisting SagThis calculation has to be made after tower and foundation work is completed

1. Actual Span measured in the Field £ = ......... ...........m

2. Saddle Elevation of the Walkway Cable on th e higher S id e E h = ......... ...........m

3. Saddle Elevation of the Walkway Cable on th e lower S id e E, = ......... ...........m

4. Difference in Elevation h Eh ■ Ej h = ......... ...........m

5. Dead Load Sag: f o r Spans up to 80m bd£

20bd = ......... ...........m

or fo r Spans over 80m bd£

22bd = ......... ...........m

6. Hoisting Sag bh = 0.95 x b(] = bh = ......... ...........m

7. f min in hoisting Case fmin(4 b h - h ) 2

1 6 b hfmin ~ ......... ...........m

Chapter 3:Design 65


3.3.5 D esig n o f B ridg e Fo u n d a t io n Str u c tu r e s

Design of a bridge foundation structure is mainly to select the standard anchor block types for right bank and for left bank and fill in the required data in the selected drawings.

Standard anchor block (bridge foundation structure) types have been developed for all possible cases up to span 120m. The design concept and statical analysis has been followed as per chapter 3.2.3, while developing the standard anchor block types.

There are basically seven types of anchor blocks depending upon the soil or rock type, whereof the typical designs are illustrated below:

1. RCC Deadman and Gravity Soil Anchor Block on Flat Topography

JZ.Sf*©asuCJ£©H

ETfTfU©Ttrn 2

2. RCC Deadman and Gravity Soil Anchor Block on Slope Topography



3. RCC Single Drum Rock Anchor Block in Hard Rock.

min. 1.50 m min. 2.50 m 40 60

4. RCC Double Drum Rock Anchor Block in Hard Rock.

min. 2.80 40 60

Chapter 3-.Design 67


5. RCC Single Drum Rock Anchor Block in Fractured Hard Rock and Soft Rock

Rock

6. RCC Double Drum Rock Anchor Block in Fractured Hard Rock and Soft Rock

min. 2.80 40 60

FracturedRock

7. RCC Deadman Anchor Block in Fractured Hard Rock and Soft Rock

68 Chapter 3:Design

2.0

0m

----

----

---T

!

2.0

0 i

n

[ ;

2.0

0 m


To select an Anchor Block Type proceed as follows.• define the walkway width (refer chapter 3.3.4).• define the span of the bridge from the bridge profile (refer chapter 3.3.3).• define the topography of the ground where the anchorage block will be placed as flat or slope.• The topography is defined as flat if the ground slope is less than 10°, and slope if the ground slope is

more than 10°.• define the soil or rock type from the Form No 1: Survey Form and Checklist, chapter 4.6.• define the tower height from bridge profile (refer chapter 3.3.3). Tower height = Height of walkway

cable saddle from the ground + 1.1m in case of soil bank and flat topography. Tower height = 2.4m (fixed) in case of soil bank and slope topography. Tower height = 2.0 m (fixed) in case of Rock bank.

• select the anchor type and the corresponding drawing from the selection tables according to the above design data.

Design the Anchor Types as per following Checklist.

A. Design Data

Fill in the following Design Data from Form No. 1: Survey Form and Checklist

• Walkway Width, WW (70 or 106cm): ...... ...........cm

• Bridge Span: ...........m

Right Bank Condition

Geology: Soil □If Soil, how is the Ground Surface? Flat □ or Hill Slope □

(up to 10° slope) (more than 10° slope)What is the Soil Type? Gravelly □ Sandy □ Silty □Tower Height from Ground up to H.C.Saddle (data from bridge profile):

2.4m □ 3.4m □ 4.4m □If Rock, what is the Rock Type? Hard Rock □ Hard Rock □ Soft Rock □

(only few fractures) (highly fractured)

Tower Height 2.0m in Case of Rock □Left Bank Condition

Geology Soil □If Soil, how is the Ground Surface? Flat □ or Hill Slope □

(up to 10° slope) (more than 10° slope)What is the Soil Type? Gravelly □ Sandy □ Silty □Tower Height from Ground up to H.C.Saddle (data from bridge profile):

2.4m □ 3.4m □ 4.4m □If Rock, what is the Rock Type? Hard Rock □ Hard Rock □ Soft Rock □


Tower Height 2.0m in Case of Rock □Chapter 3¡Design 69


B. Selection of Anchorage TypesSelect appropriate anchorage type at Right Bank and Left Bank according to the above design data.

Procedure for Selection:• According to the Soil/Rock type and Slope of the ground, refer to respective tables for selection of

Anchorage Block as per below.for Soil and Flat Ground : Tablefor Soil and Hill Slope : Tablefor Hard Rock : Tablefor Fractured Hard Rock or Soft Rock:Span up to 90m (WW = 70cm) and up to 60m (WW = 106cm) : TableSpan Range 91 -120m (WW = 70cm), 61 -120m (WW = 106cm) : Table

• In the table match the design data:Selected Walkway Width —» Bridge Span — >Tower Height -» Soil type Anchor Type and Drawing No. for right bank and left bank respectively.

C. Anchor Type Selection Tables

• In Soil and Flat Ground:Table 1: Selection of RCC Deadman and Gravity Soil Anchor Block in Flat Ground

Span Range, m TowerHeight

[ml

Foundation Soil Type

BlockType

DrawingNo.Walkway: 70cm Walkway: 106cm

Up to 45m Up to 30m

2.4All

IF 21Dcon

3.4 2F 22Dcon

4.4 3F 23Dcon

46-90 31-60

2.4

All

4F 24Dcon

3.4 5F 25Dcon

4.4 6F 26Dcon

91 - 120 61 -75

2.4

All

7F 27Dcon

3.4 8F 28Dcon

4.4 9F 29Dcon

- 76-90

2.4

All

10F 30Dcon

3.4 8F 28Dcon

4.4 1 IF 31Dcon

- 91 - 105

2.4

All

12F 32Dcon

3.4 8F 28Dcon

4.4 13F 33Dcon

- 106-120

2.4Gravely 12F 32Dcon

Sandy, Silty 14F 34Dcon

3.4All

15F 35Dcon

4.4 13F 33Dcon

123 or Table 4

5 or Table 6 7

—> Select the corresponding

70 Chapter 3:Design


• In Soil and Slope Ground:

Table 2: Selection of RCC Deadman and Gravity Soil Anchor Block in Hill Slope


[m|


BlockType

DrawingNo.Walkway: 70cm Walkway: 106cm

Up to 60m Up to 40m 2.4 All IS 41Dcon

6 1 -9 0 41-60 2.4 All 2S 42Dcon

91 - 120 61-75 2.4 All 3S 43Dcon

- 76-90 2.4

Gravely 4S 44Dcon

Sandy 5S 45Dcon

Silty 6S 46Dcon

- 91 - 105 2.4Gravely, Sandy 7S 47Dcon

Silty 8S 48Dcon

- 106-120 2.4Gravely, Sandy 8S 48Dcon

Silty 9S 49Dcon

• In Hard Rock for all Span Range:

Table 3: Selection of RCC Single Drum Anchor in Hard Rock

Span Range, m Tower Height [m[ Block Type Drawing No

Walkway: 70cm Walkway: 106cm

up to 90 up to 60 2.0 1HRS 61Dcon

91-120 61 - 120 2.0 2HRS 62Dcon

When slope is too steep and there is not enough space for single drum anchorage system (Table 3), select the double drum system from following table 4.

Table 4: Selection of RCC Double Drum Anchor in Hard Rock

Span Range, m Tower Height [m] Block Type Drawing No


up to 90 up to 60 2.0 1HRD 63Dcon

91 - 120 61 - 120 2.0 2HRD 64Dcon

• In Fractured Hard Rock/Soft Rock for Span Range up to 90m (WW = 70 cm) and 60m (WW = 106cm ):

Table 5: Selection of RCC Single Drum Anchor in Fractured Hard Rock/Soft RockSpan Range, m Tower Height

[ml Block Typer

Drawing NoWalkway: 70cm Walkway: 106cmup to 90 up to 60 2.0 IFRS 65Dcon

Chapter 3:Design 71


When slope is too steep and there is not enough space for a single drum anchorage system (Table 5), select the double drum system from following table 6.

Table 6: Selection of RCC Double Drum Anchor in Fractured Hard Rock/Soft Rock

Span Range, m Tower Height [ml Block Type Drawing No


up to 90 up to 60 2.0 1FRD 66Dcon

• In Fractured Hard Rock/Soft Rock for Span Rang of 91- 120m (WW = 70 cm) and 61-120m (WW = 106cm):Table 7: Selection of RCC Deadman Anchor in Fractured Hard Rock/Soft Rock

Span Range, m Tower Height [ml Block Type Drawing No


91-120 61-120 2.0 2FRD 67Dcon

Selected Anchorage Foundation Type and corresponding Drawings from the Tables above:

Right Bank: Anchor Type.................... Drawing No

Left Bank: Anchor Type.................. Drawing No

D. List of DrawingsSelect the required Steel Drawings and Construction Drawings accoiding to the walkway width, selected cables and selected Anchorage Block types. For this, refer to Chapter 4: Bridge Standard Drawings.

Prepare a General Arrangement drawing for individual bridge design. For this, refer to Chapter 3.3.7: General Arrangement Drawing.

3.3.6 O th e r Str u c tu r e s

Besides the bridge structure, some other adjacent structures may be required for overall bridge stability and for safety measures. These are the following structures.

A. Windguy ArrangementB. Retaining StructuresC. Slope Protection worksD. River Bank Protection

A. Windguy ArrangementGenerally Windguy Arrangements are not required for bridges with span of up to 120m. Therefore, no

lateral stabilizing measures (windguy system) is considered in this standard suspended bridge design. However, for special cases (spans more than 120m or extreme windy areas exceeding wind speed of 160km/h) there is a provision for fixing a windguy system, (see also chapter 3.2.1 Loadings). For such cases the general layout for Windguy Arrangements is shown on the following pages. For detailed geometric calculations refer to the Design Manual, Volume A of the Suspension Bridge Project, Nepal. The Steel Drawing for the windtie cable clamps is shown on Drawing No. 11A and respective Construction Drawings for different types of windguy cable anchorages are given in Drawing Nos 51 Aeon, 52Acon, 53Aeon, 54Acon, 57Acon and 58Acon in Volume III.

72 Chapter 3 .Design


The Layout of the Windguy Arrangement

LEFT BANK RIGHT BANK

The Geometry of the Windguy Arrangement

Plan

/

The design of the Windguy Arrangement is to:• select the windguy cable and windties cable• select the windguy cable anchor blocks• calculate geometry of the windguy arrangement

Chapter 3: Design 73


• Selection of Windguy Cable and Windties Cable:Select the windguy & windtie cables from the following table according to the span of the bridge.

Selection of Windguy Cable and Windtie Cable

Span, m Windguy Cable, mm Windtie Cable, mm

Up to 150 26mm 13

150-200 32mm 13

• Selection of Windguy Cable Anchor Type:There are each two types of gravity Soil Anchor Blocks, gravity Rock Anchor Blocks and Drum Anchors depending on the soil or rock type and the diameter of the Windguy Cable.For details refer to respective construction drawings in Volume III.

w Select the Windguy Cable Anchorage Type from following Tables: *

Selection of Windguy Cable Gravity Anchor Block on Soil

Windguy Cable 0 [mm] Block type Drawing No

26 Soil Block 51 Aeon

32 Soil Block 53Acon

Selection of Windguy Cable Gravity Block on Rock *


26 Rock Block 52Acon

32 Rock Block 54Acon

Selection of Windguy Cable Drum Anchor on Hard Rock*


26 or 32 Hard Rock Drum 57Acon

Selection of Windguy Cable Drum Anchor on Fractured Hard Rock or Soft Rock*


26 or 32 Soft Rock Drum 5 8 Aeon

* If both banks are rock, select the Drum Anchor for one bank and the Gravity Rock Anchor for the other bank.If one bank is rock and the other bank is soil, select always the Drum Anchor for the rock bank.



B. Retaining structuresRetaining structures are necessary to retain the earth (soil, fractured rock and weathered soft rock)

behind the anchorage blocks of the bridge. There are many options of retaining structures. But for the trail bridge construction most feasible are retaining walls. Retaining walls can be of gabion boxes, rubble masonry and dry stone masonry. For the Short-Span trail bridge construction dry stone retaining wall or breast wall are preferable, since they require only local materials.

The choice between retaining wall and breast wall depends on different factors, such as available space behind the blocks, required height of the protection, soil conditions etc.

Retaining walls are used when the earth to be retained is loose soil with large protection height. For the design of the retaining wall use the following table.

Retaining Walls

Type Dry Stone Banded Dry Stone / Masonry

Section

]

w *_______ d r y S to n e

f f l

^ w! f > ! L

As----m o rta r

W b

T op w id th , W t 0 .6 - 1.0 m 0 . 6 - 1 . 0 mB ase w id th , W b 0 . 5 - 0 . 7 H 0 .6 - 0 . 6 5 HF ron t b a tte r v a rie s va rie sB ack b a tte r v a rie s ve rtic a lInw ard d ip o f fo u n d a tio n , n 1 : 3 1 : 3

F ounda tion d e p th > 0 .5 0 m > 0 .5 0 - 1 m

R ange o f he igh t, H 1 - 6 m 6 - 8 m

Hill s lope ang le , a < 3 5 ° N> o o

Breast walls are used when earth to be retained is fractured or weathered rock or compact soil with temporarily unstable nature. For designing breast walls use the following table.

Breast Walls

Type Dry Stone!-------------------------------------------

Banded DryStone / Masonry

Section sc

4

W t - r - f t

1

^ 3 *

? ifW b I

X/ J / L --------d r y S t o n e

y ----m o rta r

W b IT op w id th , W t 0 .5 0 m 0 .5 0 mB ase w id th , W b 0 .2 9 H 0.3H 0 .3 3 H > 0 .5HB ack b a tte r 3 : 1 4 : 1 5 : 1 3 : 1Inw ard d ip o f fou n d a tio n , n 1 : 3 1 : 4 1 : 5 1 : 3

F ounda tion dep th > 0 .5 0 m > 0 .5 0 m > 0 .5 0 m > 0 .5 0 m

R ange o f he ight, H < 6 m < 4 m < 3 m 3 - 8 m

Hill s lope ang le , a 35 - 60° 35 - 60°

Chapter 3:Design 75


C. Slope Protection MeasureSlope protection measure depends on the factors influencing slope instability. It is recommended to

select the bridge site, where there are no slope instability features (refer chapter 3.4.3). However, often it is necessary to drain out the surface runoff and seepage water from the slope as a slope protection measure.

Water should be collected as closely as possible from its origin and safely channeled to a nearby watercourse. The surface drainage can be catch drain on the slope or drainage around the anchorage foundation or combination of both. The choice depends on the position of the anchorage foundation and the profile of the natural terrain as shown in the sketch bellow.

The drain should be open type and section of the drain as per following design.

To avoid self-scouring, the drain outlet should be protected as shown in the following sketch.

In seepage area, sub-surface drainage is required around the anchorage foundation. The typical layout design of the sub-surface drain is as shown in the sketch bellow.

SECTION PLAN



The typical design of the sub-surface drain i£ as shown in sketch below.

drainage pipe (perforated

polyethylene)

gravel filling built up as filter bed

drainage canal, masonry 1:4

1-2 cm

Bio-EngineeringSurface drainage alone may not be sufficient for unstable slopes. The most effective method for

stabilizing such slopes is bio-engineering in combination with light civil structures such as catch drains, check dams, cascades etc. This is a cheap and easy method. The main concept of this method is to grow trees, plants such as shrubs or grasses. Deep rooted and fast growing trees and plants are most suitable for this purpose. Proper selection of plant types is most important and should be based upon local experience. Some of the vegetation measures are:• planted grass lines: contour/horizontal or down slope/vertical or random planting• grass seeding• turfing• shrub and tree planting• shrub and tree seeding• fascines (bundles of live branches are laid in shallow trenches)

For more and in-depth details about bioengineering techniques refer to the respective literatures and Manuals. One of the recommended manual is: " Road Side Bio-Engineering, Reference Manual by John Howell, published by HMG/Department of Roads”.

D. River Bank ProtectionRiver protection works are of temporary nature and costly. This requires frequent maintenance to

keep the structure functional. Therefore, avoid bridge site, which requires river protection works as far as possible. This is a complex subject and cannot be covered by this handbook. For detail refer to SBD Design Manual Vol.A.

3.3.7 G en er a l A r r a n g e m e n t D ra w in g

General Arrangement (GA) drawing shows the overall plan and profile of the bridge. The GA should reflect the major components of the bridge and its geometry including the elevations of the foundations at the right and left bank. The GA is required for overall view of the designed bridge and also for layout of the bridge for construction.

Draw the GA on the same bridge profile as already done under chapter 3.3.3, and mention the following data on the plan and the profile of the bridge:

• span and dead load sag,• distance from the axis point A and B (which, were fixed during survey) and the center of the tower,• cable elevations at saddles, elevation of the lowest bridge point and all bridge foundation levels,• over all dimensions of the bridge structures and its elevations.

The completed GA should be sufficient for the layout of the bridge. An example of a GA drawing of a bridge is given on the next page.

Chapter 3:Design 77

Chapter 3: D

esign

-400

pRO-

00c05T3fDE3a-a>a-

<o3“3CD

3.4 D

es

ign E

xa

mp

le


4. B r id g e S t a n d a r d D r a w in g s

4.1 In t r o d u c t io n a n d O v e r v ie w o f D r a w in g s

The Bridge Standard Drawings represent the centerpiece of the Short Trail Bridge Standard. They are composed as a unit component system and are categorized in two categories:

• Construction Drawings

• Steel Drawings

Both drawing categories are linked with each other and depending on the bridge design the required drawings are selected.

Construction Drawings

Drawing Titles Drawing Nos.

FITTING Walkway Fitting for 70 cm Walkway Width 19Dcon70DETAILS Walkway Fitting for 106 cm Walkway Width 19Dconl06

TOWER CSM Tower & RCC Core for 70 cm Walkway Width 20Dcon70DETAILS CSM Tower & RCC Core for 106 cm Walkway Width 20Dconl06

SOIL

TORS Fl

atG

roun

d RCC Deadman & Gravity Soil Anchor Block in Flat Ground for 2 Walkway Cables

RCC Deadman & Gravity Soil Anchor Block in Flat Ground for 4 Walkway Cables

21Dcon - 26Dcon (6 Drawings)

27Dcon - 35Dcon (9 Drawings)

uz< , wH Chà o

RCC Deadman & Gravity Soil Anchor Block in Hill Slope for 2 Walkway Cables

41Dcon & 42Dcon

RCC Deadman & Gravity Soil Anchor Block in Hill Slope for 4 Walkway Cables

43Dcon - 49Dcon(7 Drawings)

UOr/

RCC Single Drum Anchor in Hard Rock for 2 Walkway Cables 61DconinXO RCC Single Drum Anchor in Hard Rock for 4 Walkway Cables 62DconXu

nnRCC Double Drum Anchor in Hard Rock for 2 Walkway Cables 63Dcon

<*Ü

<a RCC Double & Single Drum Anchor in Hard Rock for 4 Walkway Cables

64Dcon

ooc Q

§ ^RCC Single Drum Anchor in fractured Rock for 2 Walkway Cables 65Dcon

RCC Double Drum Anchor in fractured Rock for 2 Walkway Cables 66Dcons “ RCC Deadman Anchor in fractured Rock for 4 Walkway Cables 67Dcon

u<2 w Gravity Soil Block for Cable 0 26mm 51 Aeon75 SU Gravity Rock Block for Cable 0 26mm 52Acon

r Dra

wi

dguy

Ci

optio

nal

Gravity Soil Block for Cable 0 32mm 53AconGravity Rock Block for Cable 0 32mm 54Acon

© cy ^

RCC single Drum Anchor in Hard Rock, Cable 0 26 or 32mm 57Acon< RCC single Drum Anchor in Fractured Rock, Cable 0 26 or 32mm 5 8 Aeon

see Volume IIISteel & Construction Drawings

Chapter 4: Bridge Standard Drawings 79


Steel Drawings

Drawing Titles Drawing Nos.

W a l k w a y

C r o s s B e a m s

Crossbeam for 2 Walkway Cables for walkway width = 34 cm* Crossbeam for 2 Walkway Cables for walkway width = 70 cm Crossbeam for 4 Walkway Cables for walkway width = 70 cm Crossbeam for 2 Walkway Cables for walkway width = 106 cmCrossbeam for 4 Walkway Cables for walkway width = 106 cm Steeldeck Standard Panel, length = 198 cm / width = 34 cm

S t e e l D e c k Steeldeck Standard Half Panel, length = 98 cm / width = 34 cm

C/3títíGG<in

HZtíStíUtíot íz3Pí

Steeldeck Special Panel,length = 223 cm / width = 34 cm

Saddles & Reinforcement for¿1 RCC Deadman & Gravity Soil Anchor for 2 Walkway Cables O5/5 Saddles & Reinforcement for

RCC Deadman & Gravity Soil Anchor for 4 Walkway CablesSaddles & Reinforcement forRCC Deadman Anchor in fractured Rock for 4 Walkway Cables

t íuooá

Saddles & Reinforcement forDrum Rock Anchor for 2 Walkway Cables

01D*02D02D403DQ3D408A09A10A

20D2

20D4

20D4S

60D2

optional

Saddles & Reinforcement forDrum Rock Anchor for 2 Walkway CablesWindties Cable Clamps for Windguys Cable o 26 or 32 mm Windguys Cable Anchorage for one Cable End o 26 or 32 mm

60D4

11A50A

*Also a narrow walkway of 34cm width (lpannel wide only) has been developed, but is not used very often and is, therefore not considered in this Handbook; but can be used, if dimensions of anchor blocks are designed accordingly.

Legend for the Drawing Numbers and Suffixes:

Drawing No. Suffix Bridge or Drawing Type

cn h A For All bridge typestí Ow 5 02 D For suspended bridge types« £ 1/3 *Q

02 D4 For 4 walkway cables02 D4W Suitable for Windguy cables20 D4S Special42 Dcon construction drawings

zo 20 Dcon 70 For 70 cm walkway widthl-N wh a Anchor Drawings (Block Types)u ztí 3F Block Type 3 in Flat Groundtí £t í 5S Block Type 5 in Hill Slopeto t í 1HRS Block Type 1 in Hard Rock for Single Drumz QO M 1HRD Block Type 1 in Hard Rock for Double Drumu IFRS

1FRDBlock Type 1 in Fractured Rock for Single Drum Block Type 1 in Fractured Rock for Deadman

80 Chapter 4: Bridge Standard Drawings


4 .2 C o n c e p t o f t h e S t a n d a r d D r a w in g s

Steel Drawings

Each Drawing is providing the necessary information and specifications for manufacturing the desired steel parts. Depending on the width of the walkway, the size of walkway cable and the span the empty spaces in the materials list have to be filled in and the total weight has to be calculated as per example below.



1 3T3

a f 13 5 —

12 for fixing first & joining Fixation Cable (]) 13 mm

1r 1.4°

1 4

blj ¥2-S 73T3 Qj~ Oí) i3 O 6 __0Q <+- 'tn2

2 for Handrail Cable (j) 26 or 32 mm r ...D

1 5 4 > -. 2 for Walkway Cable (|) 26 or 32 mm 1r ...D

A = ........................ .......... kgTotal transportationAVeight B+C+D+R+0.16 kg

B = ................. ^ ............. kgTotal Structural x\Steel = (u+g) N.

g = 10.64 kg Steel to be galvanized

C = 0.32 kg Nuts, Bolts, Washers

...........kg N.^^Bulldog^Grips '

R = " , ...........kgReinforcement Steel

fill in the <|) of the required Bulldog Grips plus the weight from the table below

compute total weights from weight column of material list

Fill in :Bridge Name No, Bank &Span

Width of Walkway

No of required foundation

HMG / Ministry of Local DevelopmentDoLIDAR / Short SpanTrail Bridge Standard

Bridge Name:No: Bank: Span:Steel Drawing:Saddles & Reinforcement for RCC Deadman & Gravity Soil Anchor

for 2 Walkway Cables■ - —- — -—► Walkway Width : cmSet for one Foundation

^ 1 or 2D ate : S ep t 20, 2001 D raw ing No. 20D2

Cable Bulldog Grips ———-^Weight<t> mm for two cables (kg/pc) Total kg

26 10 X m x S )

32 12 C f3 o ' y / XxCkh6(ï)



From the total weights of each drawing the grand total for each steel category has to be added up as follows:

A : Means the entire weight of steel including galvanization to be transported to the site.B : This is the total structural steel raw or untreated. This includes steel profiles, plates and flats but not

reinforcement bars and other steel items.C : This is the weight of Nuts, Bolts & Washers, (galvanized weight)D : This is the weight of Bulldog Grips or Thimbles, if required, (galvanized weight)R : This is the raw weight of Reinforcement Steel or Plain Rods they are never galvanized.

The total transportation weight A = B + C + D + R

g : The little g indicates the weight of structural steel to be galvanized. This weight is part or can be the sum of the total structural steel (B), but is not an additional weight.

Above distinction is made for quotation purposes, because the price per kg (or piece) is varying greatly among each other. Reinforcement steel is much cheaper and Nuts & Bolts are much more expensive than structural steel.

The weight of steel to be galvanized is necessary, to obtain the price for galvanization separately, without the cost of the steel as such.

Usually steel drawings are not necessary at the construction site but for assembly and identification of the steelparts a copy of each steel drawing should be available. Also for maintenance at a later stage copies of the steel drawings are useful.

Construction Drawings

The construction drawings are the actual site drawings of which one complete set is absolutely necessary at the site. Depending on the required width of the walkway the corresponding “Walkway Fitting” & “CSM Tower” drawings have to be selected (either 70 cm or 106 cm).

• Walkway Fitting Drawing(for 70 or 106 cm walkway)

• Details of CSM Tower & RCC Core(for 70 or 106 cm walkway)

The CSM Tower & RCC Core, drawing no. 20Dcon70 or 20Dconl06, are identical for all bridges.

For the actual anchorage arrangements there are two main categories of drawings:

• Soil Anchor Drawings• Rock Anchor Drawings

Both drawing types are complete designs and are fulfilling respective parameters selected in the design form. Also in both drawings the necessary quantities of construction materials are already calculated. These have to be filled in respective tables given in the cost estimate Form No. 3 or 4.

The Soil Anchor Drawings are sub-divided in to:

• Soil Anchor Block in Flat Ground• Soil Anchor Block in Hill Slope

In flat ground with a gradient of max 10° the block types IF - 15F are applicable, whereas in slopes over 10° the block types IS - 9S are to be applied.

It is absolutely necessary to fill in the Elevation and Cable diameters as indicated in the drawings. The levels are to be determined in the topographic profile of he survey whereas the cable diameter can be taken from the design form.



Example : Soil Anchor

G r a v i t y S o i l A n c h o r B l o c k660 ---------------

(id)—— Erection Hook

(id)— 3 Stirrups ^10

(n )---- Anchor Rods <f> 25



4 .3 R e l a t io n s h ip b e t w e e n c o n s t r u c t io n a n d s t e e l d r a w in g s

Each Construction Drawing has related Steel Drawings. Respective related drawing numbers are mentioned on the drawing itself and also respective steel parts numbers are shown on the construction drawing for easy reference.

The Construction Drawing "Walkway Fitting", Nos 19Dcon70 or 19Dconl06 is showing the superstructure of the bridge. The related Steeldrawings are the corresponding Steel Crossbeam and Steeldeck Drawings.

Construction Drawing No 19“Walkway Fitting”

Steel Drawing Nos 01 - 03“Crossbeam”

Steel Drawing Nos 0 8 - 1 0“Steeldeck”



The Steel Drawings for Saddle and Reinforcement, Nos 20 & 60 are related to the corresponding Construction Drawings Nos 20Dcon70 (70 cm walkway), or 20Dconl06 (106 cm walkway).

Furthermore, depending of the soil conditions (soil or rock), the Steel Drawing Nos 20 & 60 are related either to Anchor Drawings "Soil" or "Rock" as shown below.

Construction Drawing No 20“Details of CSM Tower & RCC Core”

Steel Drawing Nos 20 or 60“Saddles and Reinforcement”

Construction Drawings Nos 2 1 - 4 9 Construction Drawing Nos 61 - 67“SOIL ANCHORS” “ROCK ANCHORS”



5. C a l c u l a t io n o f Q u a n t it y a n d C o s t E s t im a t e

Calculation of quantities and cost estimate is required for the purpose of planning and implementation. The selected approach of implementation determines the methodology of calculating the quantities & cost estimate. There are basically two approaches of implementation. These are:

• Implementation by the Community follow Form No. 3 Quantity & Cost Estimate for Community Approach

• Implementation by Contractor

through Public Tender

follow Form No. 4 Quantity & Cost Estimate

for Public Tender & Contracting

Standard forms for calculation of quantities and cost estimate for both implementation approaches are presented in the Vol. II as Form No.3 and Form No.4. The methodology of calculating quantities and preparing cost estimate for the two approaches of implementation and how to use the respective Forms is described in the chapter below.

5.1 Im p l e m e n t a t io n b y t h e C o m m u n it y

Use the Form No.3: Cost Estimate (Mode of Execution: Community Approach).To calculate the quantities and to prepare the cost estimate in Form No.3, follow in sequence the procedure outlined below:

• Quantity Calculation

=> Calculate quantities of cables from the Form No.2: Cable Design. Fill in the Quantity Calculation Sheet of Wire Rope (Cables). This sheet will show the cable lengths of each diameter and the total weight of the cables.

=> Calculate quantities of Steel Parts and Steel Deck from the corresponding steel drawings. Fill in the Quantity Calculation Sheet of Steel Parts and Steel Deck.

=> Calculate quantities of Earth Works from General Arrangement Drawing. Fill in the Quantity Calculation Sheet of Construction.

=> Calculate quantities of other construction works from the corresponding Construction Drawings. Fill in the Quantity Calculation Sheet of Construction.

=> Prepare list of construction materials according to the calculated quantities of construction works.

=> Calculate transportation weights for cables and other construction materials locally not available.

=> Calculate quantities of Works and Labor.

• Rate AnalysisPrepare the rate analysis for fabrication of steel parts, steel decks and road transportation (items of external support to the community) as per unit quantity, unit cost and standard norms.

• Abstract of CostCompute the abstract of cost of the bridge as per the quantities of works (from Quantity Calculation Sheets) and the rates (from Rate Analysis) for each item of works and summarize the cost as per the category of works.

Chapter 5: Calculation of Quantities and Cost Estimate 87


• Summary of Estimated Cost

=> Bridge Cost: Calculate the Estimated Bridge Cost by summarizing the Abstract of Cost. Also calculate bridge cost per m span.

=> Contribution: Estimate the expected contribution from different partners.

=> Breakdown of the Contribution: Break down the contribution as Local Contribution and Outside Contribution.

• Summary of Actual CostIn the majority of cases, the actual bridge cost will not be the same as estimated. Therefore, calculate the actual bridge cost after completion of the bridge.

5 .2 Im p l e m e n t a t io n b y t h e C o n t r a c t o r t h r o u g h t h e P u b l ic T e n d e r

Use the Form No.4: Cost Estimate (Mode of Execution: Contractor).To calculate quantities and to prepare the cost estimate in Form No.4, follow in sequence the procedure outlined below:

• Quantity Calculation

=> Calculate quantities of cables from the Form No.2: Cable Design. Fill in the Quantity Calculation Sheet of Wire Rope (Cables).

=> Calculate quantities of Steel Parts from the corresponding steel drawings. Fill in the Quantity Calculation Sheet of Steel Parts and Steel Deck.

=> Calculate quantities of Earth Works from General Arrangement Drawing. Fill in the Quantity Calculation Sheet of Construction.

=> Calculate quantities of other construction works from the corresponding Construction Drawings. Fill in the Quantity Calculation Sheet of Construction

=> Prepare list of construction materials according to the calculated quantities of construction works.

=> Calculate the transportation weight for cable and other construction materials locally not available.

• Rate AnalysisPrepare the Rate Analysis for all items of works as per unit quantity, unit cost and standard norms. The Rate Analysis should include all taxes and overheads of the contractor.

• Abstract of CostCompute the Abstract of Cost of the bridge as per the quantities of works (from Quantity Calculation Sheets) and the rates (from Rate Analysis) for each item of works. Abstract of Cost should also include contingency of 5%. This contingency amount will cover miscellaneous costs of the project.

• Summary of Estimated CostCalculate the Estimated Bridge Cost by summarizing the Abstract of Cost. Finally also calculate bridge cost per m span.

88 Chapter 5: Calculation of Quantities and Cost Estimate


6. C o n s t r u c t io n

6.1 B r id g e L a y o u t

The Bridge Layout is to fix the bridge position and foundations at the site as per design.

Procedure for General Bridge Layout (refer to General Arrangement 'GA' Drawing):• Find the existing pegs and benchmarks.• Measure the horizontal distance between axis pegs A (L) and B(R) and compare with the

measurement given in the General Arrangement.• Check the elevations of the axis pegs A (L) and B(R) and compare with the elevations given in the

GA.

• If the horizontal distance between axis pegs A (L) and B(R) and its elevations is not similar to the measurements given in the GA, readjust the design according to the actual measurements

• If the horizontal distance between axis pegs A (L) and B(R) and its elevations is identical to the measurements given in the GA, fix the position of all foundation blocks as shown in the following sketch and procedure below.

Procedure for Detailed Foundation Layout:

• Align the centerline of the bridge by joining the permanent points with mason threads or by ranging between axis pegs 'A' and 'B' as shown in the following sketches.

Chapter 6: Bridge Construction 89


• Mark the front of the tower foundation on the bridge centerline (peg 1) with reference to the axis peg. The distance between front of the tower foundation and axis peg is given in the GA.

ii

B (R ) I 1 Bridge— ■--------- r---------------------------------------------------------- cl

• Check the location of the front of the tower to ensure it has sufficient distance (minimum 3 m for soil slope and 1,5m for rock slope) from the bank edge.

• Measure the length of the foundation from peg 1 and fix peg 2. Set up two additional centerline pegs at safe distance for the excavation works (peg 3 and 4).

B(R) 4 1 2 3

• Draw offset line (right angle) through peg 1 by 3-4-5 method (refer chapter 2.5.4). Starting from peg 1 set out pegs 5, 6, 7, and 8 for the reference line of the front edge.

16J

!B(R) 4 11 2 3----'---- ------jj90""-------------------------------------------- * *

ii\

• Draw offset line through peg 2 for reference line of the back edge. Starting from peg 2 fix the pegs 9, 10, 11 and 12. Similarly, fix the reference line of the tower foundation with pegs 13, 14, 15, 16.

8 <

5(

16 « 12 «

14 9

B(R) 4 ,

_____"J

6( 13 10

li » 15 < 11 <

• Determine the reference line at the downstream edge with the help of pegs 5 & 9, for the upstream edge, use pegs 6 & 10 (peg 19 & 20).

8 <

17 # 5‘

16 < 12 «

14 9 18

B(R) i -

19 • 6< 13 1° 20

li 15 < 11 «

• Fix the elevation line (datum level) and indicate the depth of the excavation work for tower and deadman or drum anchorage as per elevations shown in the GA and Anchorage Block drawings.

90 Chapter 6: Bridge Construction


6 .2 F o u n d a t io n E x c a v a t io n

In Soil:

Foundations should be excavated with slopes to provide stability of the cut slope. The cut slope in soil should not exceed to 3:1 (V:H). The foundation should be excavated stage wise as illustrated below.

• 1st Stage - All excavation as shown in the sketch below.

• 2nd Stage - Foundation excavation for tower as shown in the sketch below.

• 3rd Stage - Construction of tower as per design. Refer also to chapter 6.5 and 6.6.

• 4th Stage - Final Excavation for dead man beam as shown in the sketch below.



In all of the above excavation stages, excavation depth should be accurately maintained. For this, establish an elevation line (datum level) and measure the foundation depths with fixed stick.

All the excavated soils should be safely disposed without damaging the existing vegetation at down hillside, thus not effecting the environment.

In Rock:

Rock excavation is necessary to prepare the platform for the drum anchorage. Rock should be excavated manually without blasting.

Excavation in rock is done by first drilling holes to weaken the rock and then using the crowbars to break up and dig out the rock parts. The cutting can be carried out by forming steps, as shown in the following sketches.

1 st Stage 2nd Stage

Further detail on drum anchorage foundation in rock is given in chapter 6.6.4.

6 .3 L o c a l M a t e r ia l C o l l e c t io n

The required local materials for the bridge construction are sand, gravel (river gravel or broken aggregate), and stones/boulders.

collection of sand

The best stone collection is from the rock quarry. The rock should be unweathered, hard and dense with metallic sound.

In unavoidable case, boulders from the river deposits can also be collected. However, this can be used only for filling purpose (broken stone filling). In any case, stones from rock quarry are necessary for masonry works.

The quality requirement for the stone/boulders is further detailed in chapter 6.5.



6.3.2 Sand

Sand can be collected from river deposits or from a quarry. The quality of the sand should be assessed before sand collection. Check visually the content of the impurities such as mica, clay, loam, mud organic materials etc. If such impurities are unavoidable, it is recommended to wash the sand before use. Sand containing significant quantity of mica should be rejected. The grain size of the collected sand should not be too fine.

'PÂTÎTFill a bottle with sand and water and shake vigorously

and leave to settle. If the sand is clean the sedimentation will be less than 5mm after two hours. And the water above will only be lightly cloudy.

The quality for the sand is further detailed in chapter 6.6.1.

6.3.3 G r a v e l

Gravel can be collected from river deposits or by breaking boulders into the necessary size. The required sizes and their proportion should be

5 to 20mm - 40%20 to 40mm - 60%

Gravel should be of hard rock origin. Gravel of unsuitable rock such as mica, marl and sand stone should be rejected. Likewise flat and flaky particles should also be rejected. The collected gravel should be free from organic contaminants like clay, loam, mud or stone dust etc.

The quality requirement for the gravel is further detailed in chapter 6.6.1.

6 . 4 T R A N S P O R T A T IO N A N D S T O R A G E O F T H E M A T E R IA L S

Material other than local materials has to be transported from road head to the site by porter or other means. These materials are mainly Cement, Steel Parts and Wire Ropes.

6.4.1 C em e n t T r a n s p o r ta tio n a n d Sto r in g

Utmost care should be given for transportation and storing of the cement. The prime importance is the proper packing of the cement before transportation to make it watertight and airtight. For this, cement bags as received from the market or factory should be double packed by additional packing with Nylon Bags and plastic layer inside. Re-opening the bags (especially when transporting by mules) is not permitted before use at the site.

The following conditions must be met for the storing of the cement:• Cement must always be stored under a roof with adequate protection from rain. A raised plank floor is

necessary to prevent cement from damp.• Storage must be arranged in such a way, that the oldest cement can be used first.

6.4.2 Ste e l Pa r ts T r a n s p o r t a tio n an d Sto r in g

There is a great chance of damage of steel parts during loading/unloading and transportation. The most common damage is:

• deformation of cross beams and steel decks due to mishandling during loading and unloading,

• deformation of suspenders and reinforcement bars due to mishandling during loading and unloading

The steel parts should be loaded or unloaded carefully to avoid above damages. Do not allow steel parts to fall from a height. Suspenders should be bound together with the crossbeam.



Similarly, the following conditions must be met for the storing of steel parts to avoid any damage.

• Galvanized and non-galvanized steel parts must always be stored under a roof with adequate protection from rain and should not be in contact with the ground.

• Galvanized steel parts should not be transported and stored together with salt or acid.• Steel parts should be stacked and stored element/component-wise separately, avoiding the mix up of

different elements. Thus, any element or component can be easily located during the bridge erection.• All fixtures (nut/bolts, washers, thimbles and bulldog grips) should be packed/marked and stored

separately according to its sizes.• Steel parts, particularly suspenders and reinforcement bars, should not be permitted to bend during

portering and storage.

6.4.3 W ire Ro pe T r a n s p o r ta tio n a n d Sto r in g

It is vital to handle and transport the cable carefully to avoid any defects like kinks, splices and broken strands. Some examples of defects on cables due to mishandling and improper transportation are shown in the photographs below.

Also pulling or dragging the cable along the road for transportation is not permitted.

To avoid such defects, follow handling and transportation methods as described below.

• Method of Unreeling Light Cables with the Help of a Reel Support

Wrong Correct

Method of Unreeling Cables by Unrolling Each Loop Taken from the Reel.



Before cable cutting, the cable ends should be tightened by a binding-wire (seizing) to avoid loosening of the cable wires as shown in the following sketch.

Method of Transportation by Porters

Wire Binding

Cut here (Seizing)

There are mainly two methods of cable transportation as illustrated in the following photos.

Cable Transportation on the Shoulder (for short distances)

Bundled Cable Transportation(for longer distances)

Cable transportation as shown in the sketch below, is wrong and should not be practiced.



6 .5 M a s o n r y a n d S t o n e D r e s s in g W o r k

6.5.1 R e q u ir e m e n t s f o r B u il d in g S t o n e s

Building stones must be of high strength, density and durability. A good building stone should be hard, tough, compact grained and uniform in texture and color.

Crystalline stones are superior to non-crystalline stones. Metamorphic rocks are more durable than sedimentary rocks. Sedimentary rocks have been formed by water sediments of clay, sand or gravel, which got cemented together by lime, silica etc. Originally metamorphic rocks are either of volcanic or sedimentary origin but have subsequently been formed and shaped by movements of the earths' crust imposing high pressure and heat.

A good building stone absorbs no or very little water and must be free from decay, cracks and sand-holes.

6.5.2 Q u a r r y in g

Rocks for stone masonry works should be broken from a quarry by crowbars and wedges. Natural fractures and bedding planes of stratification are the weak features of rock. These natural joints are taken as advantage to break and separate one block from the other.

It is advised that only when natural joints do not exist that artificial fissures be made by drilling a line of holes in rows along the desired breaking line. By inserting conical wedges and driving them in succession with a hammer the rock will crack along the face of the holes.

However it is generally worthwhile to search for quarries with existing natural joints like dominant bedding planes, since the broken stones are much easier for dressing.

Boulders fallen from rocky slopes can also be used as building stones.

B u ild in g stones are first dressed to obtain two parallel planes, then outward faces must be dressed well with the help of the square bottom as shown below.

outward face

Stones from the riverbed are generally very hard and durable and can be used as filling stone, but are not suitable for stone dressing.



6.5.3 Sto n e D r es sin g

Broken stones from the quarry are to be dressed by hammer or chisel to required sizes. Depending on the function of the stone in stone masonry construction the following types of stones have to be prepared:

• Corner Stone: The comer stone is placed at each comer of the stone masonry structure. Recommended sizes are:LengthWidthHeight

30 - 85 cm min. 30 cm min. 10 cm

• Face Stone: Only one face of this stone faces outside; recommended sizes are:

LengthWidthHeight

30 - 75 cm min. 30 cm min. 10 cm

• Bond Stone: Like the face stone only one face is outside, but the bond stone extends to the interiors of the structure. Bond stones, also called through stones, go right through walls of up to 85 cm thick or more. Recommended sizes are:

Length : 45 - 85 cmWidth : min. 30 cm (face side)Height : min. 10 cm

• Coping Stone: Copingstones are put on top or at steps of stone masonry structures. Theyshould be larger and heavier than the stones below:

Length : as large as possibleWidth : as large as possibleHeight : min. 10 cm

• Filling Stone: Filling stones do not need to be dressed and are placed in the inner part of thestone masonry structure mainly to gain gravity load.

(iAK § hi) Coping Stone

(*T^T ^HT) Filling Stone ifnT) Bond Stone

Bond Stone ( TS qTT)Coping Stone <§ttt)

Comer Stone ^TT)

CopingStone (WS ^TT)

Comer Stone fr|T)

Face Stone ^ tjt)



6.5.4 Sto n e Ma s o n r y La yin g

There are many different kinds and types of stone masonries. For constructing anchor blocks and towers, only coursed (in layers of equal height) stone masonry is applied.

There are two types of stone masonry used for bridge construction:

• Coursed Random Rubble Stone MasonryThe stones are hammer-dressed, except the inside face. Gaps between beds and joints shall not exceed 12 mm.All Face Stones tail into the wall twice their height.

Bond Stones running right through the wall are inserted at least at every 150 cm intervals.

• Coursed Block Stone MasonryThe stones are chisel-dressed at all faces, except the inside face. Joints are dressed at right angles to the face. Gaps between beds and joints should not exceed 6 mm.

All Face Stones tail into the wall twice their height.

Bond Stones running right through the wall are inserted in each course at least at every 150 cm intervals.

Course Stone Masonry must be made in layers of equal height. Individual layer heights may vary but should never be less than 10 cm. Alternate joints shall be made between the layer above and below as shown in the following sketch.

In a reasonably well made stone masonry the inner friction between the beds amounts to approx. 35°.



The verification of comers as well as faces has to be checked carefully with the plumb-bob.

The Strength of stone masonry structures depends mainly on the qualities described in the table below.

.bigger. The Strength of Stone Masonry is... ...sm aller..

.with rectangular stones.

Form or Shape

...with irregular stones.

.the less stones are used.

/7 V 7 Í/A77 Number (Z3Z2Z1 ...the more stones are used.

.the rougher the joints are.

ARoughness of

joints...the smoother

the joints are.

.the smaller the beds are. Bed .the bigger the

beds are.

.the more compact the stones are.

.the better the bond across is.

.the higher strength of the mortar is.

Height & Width .the slimmer the stones are.

CD C D ) Bond Across (in plan view) CDCD

.the worse the bond across is.

I Strength of Mortar

i .the lower the strength of the mortar is.



6 .6 C e m e n t W o r k s

6.6.1 C o m p o s it io n a n d M ix t u r e s

Cement concrete is a mixture of following 4 components:

• CementOrdinary Portland Cement commonly used for general construction works

• Sand

• Gravel

• Water

Cement is very sensitive to humidity and moisture; therefore it should never be stored for a long time. In the rainy season cement bags have to be packed in additional sealed plastic bags plus additional nylon bags for protecting the cement against water and the plastic bags against damage.

Sand should be clean, sharp, angular, hard and durable. Sand must be well washed and cleaned from mud or any organic material before use. A well-graded sand should be used for cement works. All or most of the sand should pass through a 3 mm sieve or mesh wire. However sand should not be too fine, only max. 15% of the sand can be smaller than 150 microns, which is like dust.

Gravel should be clean, hard, angular and non-porous. Usually riverside gravel makes the best aggregate for preparing concrete. The com size of gravel should be smaller than 40 mm (1lA inches) but bigger than 5 mm.

Water from rivers or lakes is usually suitable for making cement mixtures. Do not use water fromponds or swamps; this water may contain a lot of organic materials.

The main characteristics of any cement work is given by the mix proportions of their components:

• Cement Mortar = Mix between Cement & Sand

• Cement Concrete = Mix between Cement, Sand & Gravel

Of course, Water is added in both cases, but the mix proportions of cement, sand and gravel give the main characteristics of any cemented work.

Mixing above components thoroughly is of utmost importance. Hand mixing should be done on a clean watertight platform. Cement and Sand should first be mixed dry, and then gravel added. Now the whole mixture should be turned over 3 times dry. Then mixing should take place for at least 5 minutes by slowly sprinkling water until the concrete is of a uniform color.



The table below depicts the most commonly used mix proportions and required quantities:

Quantities for various Types of Cement Works

Type of Dry required quantities for one cubic meter wet:iVllA. piUpUI liUIlb Stnnpc nrCement Cement bags

kgSand Gravel kJ lull V J vvl

Boulders[m3]Work Cement : Sand : Gravel @50 kg [m3] [m3]

1 : 1 - 20.4 1020 0.71 -

1 : 2 - 13.6 680 0.95 - -

CementMortars 1 : 3 - 10.2 510 1.05 - -

1 : 4 - 7.6 380 1.05 - -

1 : 6 - 5.0 250 1.05 -CementPlaster 1 : 4 0.18 9 0.024(20 mm includes 1 : 6 - 0.12 6 0.024 - -

12% waste)

1 : 4 uncoursedstone

2.66 133 0.37 - 1.2

CementStone

1 : 6 masonry 1.75 87.5 0.37 - 1.2

Masonries 1 : 4 coursedstone

2.28 114 0.32 - 1.25

1 : 6 masonry 1.50 75 0.32 " 1.25

1 : 4 : 8 3.4 170 0.47 0.94 -

CementConcretes

1 : 3 : 6 (M10) 4.4 220 0.46 0.92 -

(plain or reinforced) 1 : 2 : 4 (M l5) 6.4 320 0.45 0.90 -

1 : V : 3 (M20) 8 400 0.42 0.84 -

"Plum" 1 : 3 : 6 2.64 132 0.28 0.54 0.50Concrete with 50% bouldersSource: Indian practical Civil Engineers' Handbook, Section 20

The amount of Water should be about 50% or half the volume of cement. One 50 kg bag of cement has a volume of approx. 35 liters, which is equal to approx two kerosene tins.

Concrete and Mortars should be placed in its final position within one hour! After placing it should be well compacted by rods in order to remove any air pockets. For a concrete of high quality good compaction is essential. This may mean extra work during placing, but on no account should more water be added for reducing compacting work. Concreting should never be done if it is raining.

Curing means keeping completed cement works wet until its setting process is completed. If concrete works are not continuously kept wet during its setting process, cement mortars, cement stone masonry work and especially concrete does not develop its full strength. Curing should be done for at least 28 days.

For increasing the strength of concrete, ripped Tor-Steel bars are added whibh makes Reinforced Cement Concrete or RCC.



6 .6 .2 C o n c r e t e W o r k f o r C e m e n t S t o n e M a s o n r y (C S M ) T o w e r s

The CSM Towers or Limb Walls are concreted together to form one solid unit (See Drawing Nos. 20Dcon70 & 20Dconl06). The core and the connection of both the towers are made in R.C.C 1:2:4, whereas the limb walls are made in CSM 1:4.

Section through CSM Tower (Bridge Entrance)

• Placing the Saddles for the Walkway CablesThe saddles for the walkway cables are to be placed in between the towers. The position of the

saddles has to be checked thoroughly and the levels can be controlled with the help of a transparent plastic pipe filled with water (Level Pipe).

Concreting Work for CSM Tower Checking Level of Walkway CableSaddles



• Construction of Towers and Placing Saddles for Handrail CablesThe Towers or Limb walls support the handrail cables. The limb walls are made out of cement stone

masonry 1:4 with a R.C.C. core.The handrail cable saddles are to be placed on top of the ’’hump” of the limb wall. Make sure that the position and shape of the "hump” is correct so that the handrail cable touches the saddle plate only.

Finishing off the CSM Tower



6.6.3 C o n s t r u c t i n g t h e D e a d m a n B e a m

The Deadman Beam is a soil anchor cast in reinforced cement concrete R.C.C that lies buried under the gravity structure. The handrail and walkway cables are placed around the reinforcement bars before concreting the beam. At one bank the cables are inserted into a polyethylene (PE) pipe, so that the cables can still be moved while sag setting (See Chapter 6.6). Tensioning cable must be tightened with the bridge of bulldog grip. Use leftover plastic or cloth from cement bags to cover open parts of the pipe so that no concrete can flow into the pipe.

Fixation Cable.

The PE pipe has to be cut by two thirds at several places so that it can easily be bound around the reinforcement bars

The PE pipe can also be bent by preheating it before bending.

Deadman Beam80

ulldog Grips Erection Hook PE pipe </>63 ram*

rods <{> 20 mm

stirrups <)» 12 mm

Nos & spacing of Bulldog Grips

Cable <)> mm Nos G13 3 10 cm26 5 15 cm32 6 20 cm

Place and Fix Reinforcement Bars, Stirrups and Erection Hooks as Shown in Respective Drawings.

The fixation cable can be anchored at the temporary erection hook or fixed at one of the walkway cables.



6.6 .4 C o n s t r u c t in g D r u m A n c h o r a g e s in R o c k

There are two types of Drum Anchorages in Rock:

• R.C.C Drum Anchor in Hard Rock

• R.C.C Drum Anchor in Soft or highly fractured Rock

Drum Anchorages in Hard Rock are made by drilling holes of 32 mm diameter ( = diameter of crowbar) into the rock. Clean boreholes from dust and debris by flushing them with water.

Fill the holes with cement mortar 1:1 before the anchor rods are inserted.

The formwork for the drum is made by a chitra (bamboo mat) or plain G.I. sheet inside lined with a plastic sheet.

Use binding wire around the chitra to prevent the bamboo mat bulging during concreting.

Drilling starter holes (up to 1 foot) for Anchor Rods of a Drum Anchorage in Hard Rock.

Rotate chisel from time to time.

Use crow bar for making holes deeper.

' ' o r

■ ’Jsv.v h

Typical Cross Section of RCC Drum in Hard Rock



Drum Anchorages in soft or fractured Rock are not done by drilling holes but by excavating a round pit instead. The Anchor Reinforcement has to be placed into the pit and is fixed with the help of stirrups. The excavated pit is then filled and well compacted with concrete 1 : 2 : 4 up to ground level. At this stage the anchor rods should protrude (stand out) by approx. 40 cm. The formwork for the drum is made by a chitra (bamboo mat) inside lined with a plastic sheet bound together with a binding wire.

Typical Cross Section of RCC Drum in Soft or Fractured Rock

S

Concreting of a Drum Anchorage



6 .7 C a b l e H o is t in g a n d S a g S e t t in g

Cables are hoisted and the prescribed sag set after the Deadman Beams (see 6.5.3) or the Drum Anchors have been concreted. Please note that it takes 4 weeks until cast concrete develops its full strength. Therefore, the final cable pulling is done after a minimum of 4 weeks.

6.7.1 C a l c u l a t io n o f Ho is tin g S ag

Before starting any hoisting work, the actual span i from saddle to saddle of the bridge and the actual difference of elevation h between the walkway cable saddles have to be measured first and filled into Form No. 2 Chapter ID: Calculation of Hoisting Sag (see also Chapter 3.3.4 D).

Table for Calculating Elevation of Low Point for Cable Hoisting

1. Actual Span measured in the Field t = ........ m

2. Saddle Elevation of the Walkway Cable on the higher side Eh = ......... ........ m

3. Saddle Elevation of the Walkway Cable on the lower side E, = ......... ........ m

4. Difference in Elevation h = E|, - E, = h = ........ m

5. Dead Load Sag

For Span up to 80 meters: b„ = — 20

bd = ......... ........ m

For Span over 80 meters: bd - —:- - 22bd - ........ m

6. Hoisting Sag bh = 0.95 x b,| = bh = ........ m

(4 b. - h ) 27. f min in hoisting case f - " -111111 ” 1/: K

16 b hfmin ........ m

8. f max in hoisting case f'max — f min T h fmax = ......... ........ m

9. Elevation of Cable low point in hoisting case = E, - f „„„ = m



• Mark the calculated elevation of the cable hoisting sag (low point) on a prepared stick, tree or at the tower foundation.

• Now set up the Abney Level or Leveling Instrument at the Elevation of the cable hoisting sag so that the line of sight can easily see the mark and the low point of the cable. Setting up the Leveling Instrument at the calculated Elevation has to be done by trial and error and may take several attempts.

6.7 .2 C a b l e H o s t in g

Cables are first pulled by hand and for final sag setting with the help of the cable pulling machine or tirfor, which is fixed at the erection hook.

• Pull the cable until it reaches a level of about 20 cm higher than the calculated Elevation. Each cable should be left in this "over-pulled” position for at least 12 hours. "Over-pulling" is done to prevent any later relaxation of the cable, which may lead to a tilted walkway.

• For actual and precise sag setting first firmly clamp the special cable belonging to the tirfor machine to the backstay portion of the cable to be pulled. Then fix the tirfor machine at the erection hook and insert the special cable through the cable-pulling machine. Now apply force until the special cable is firmly under tension. Now loosen, do not remove, the bulldog grips. The cable should now be held by the tirfor machine only. Slowly release some force by carefully moving the lever of the cables pulling machine until the desired pre-calculated Elevation has been reached. When this is the case immediately retighten the bulldog grips, then completely release the tension applied by the tirfor machine.

The cable should now hang in proper hoisting position. If the low point has gone below the hoisting Elevation the whole process has to be repeated.

That means the cable has again to be over-pulled and then slowly released.

Check also that parallel cables have equal hoisting sag.

6 . 8 F i n a l i z i n g t h e C a b l e A n c h o r a g e

After the cables have been pulled and the hoisting sag is firmly set the Cable Anchorage has to be fully completed before any fitting works for the walkway can start.

6.8.1 R u s t P r o t e c t io n f o r t h e C a b l e

To achieve optimal rust protection, paint the cables in the gravity structure with coal tar and then cover with 20 x 20 cm cement concrete 1:3:6. Before painting, the bulldog grips need to be checked and retightened if required.

6.8.2 C o m p l e t in g t h e G r a v it y S t r u c t u r e

The actual gravity structure on top of the Dead Man Beam or Drum Anchors is constructed according to the respective construction drawing given in Volume III. The side and back walls as well as the top are made of coursed cement stone masonry 1:6, whereas the inside is filled with broken stones. The cement stone masonry work for the walls has to be made with hammer dressed stones of equal layer height. The broken stones for filling the inside should not be thrown but laid and interlocked as for as possible. (Refer also to chapter 6.4 Masonry and Stone Dressing Work).

Only after the gravity structure is completed can fitting work for the walkway structure start.



6 .9 W a l k w a y F it t in g

The fitting work for the walkway must only start after the gravity structure of the cable anchorage have been completed. Walkway fitting is simple and self-explanatory. Refer also to the construction Drawings No. 19Dcon70 or 19Dconl06 respectively.

Following points must be observed:

• Start fitting from one bank only• First fit crossbeam, steel panels or wooden planks as close as possible to the bridge entrance.• Always start fitting walkway deck with a "Flalf Panel" then continue with "Standard Panels" only.• Fix J-bolts at crossbeams first loosely and hang pre-bent suspender over handrail cable.• Avoid accidents by bolting panels loosely immediately after placing.• Maintain equal vertical distance between handrail and walkway cable by using a support guide

("Tokche") made of wood or bamboo.• Always finish walkway fitting with "Special Panels" and cut off extra length by hacksaw.• Check and retighten all Nuts and Bolts after completion of walkway fitting.• If wood is used for the bridge deck, the planks should be 2 meter long and min. 4 cm thick and should

be fitted in staggered way. Use washers below Bolt Heads. Distance between Crossbeams is 1 meter.

V IE W O F F E N C E W E A V IN G

Fencing is woven on the spot with gabion wire (12SWG) between the handrail cable and the fixation cable. First fix the fixation cable by pulling it through the bottom eye of the suspender along either side of the walkway, and then join it with the short piece at the other end of the bridge.



...for Fence weaving

Detail at - Z

6.10 Water Management Backfilling and General finishing Works

6.10.1 Water Management

The life expectancy of the bridge largely depends on proper water management.

Any water seepage encountered during excavation should be intercepted as close as possible to its origin and channeled safely to a nearby watercourse. Especially vulnerable is the place behind the Deadman Beam! If in doubt, or in case of unusual humidity of water seepage, provide a drain behind the Deadman Beam with side outlet. Sometimes water seepage occurs during rainy season only. Inquire with the local people.

Divert surface water and provide drainage channels as necessary. Do not hamper existing irrigation channels, rather improve and adjust them with some cement works. Discuss solutions with local people and decide on the spot.

As a general rule divert water as far away from bridge foundations as possible.

For managing surface water well, also fill the gaps around completed anchor blocks well above the existing surface. Back filling prevents surface water to flush out excavations.

Do B a c k F i l l ! ! !

6.10.2 F in is h in g W o r k

Provide finishing structures like retaining walls, staircases, small trail improvements, adjustments to nearby houses etc., if it adds functional value to the bridge.

Never do cement pointing or other non-functional works.

Also check the vegetation and plant life in the vicinity of the bridge. Plant some new trees if possible, especially if some had to be cut for bridge construction.



7. B r id g e M a in t e n a n c e

7.1 Intro duction

Maintenance of trail bridges is very crucial for keeping the mule and foot trails functional throughout the year. It is extremely essential to guarantee their permanent and safe use, maintain them in usable condition, and to preserve the investment made in these bridges. In order to determine the required maintenance, regular inspection of the bridge should be made after completion of the construction work.

The bridge maintenance work consists of the following two categories:

• Routine Maintenance

• Major Maintenance

A brief description of these two maintenance categories is given in the following sub-chapters.

7.2 Routine Main ten an c e

Routine maintenance is a preventive type of maintenance and should be done regularly. It is important to protect the bridges from getting big and irreparable damages and assures long-term use by keeping them in serviceable condition. After completion of the bridge construction, routine maintenance should be carried out on regular basis. In general, the works under routine maintenance are simple in nature.

The routine maintenance work includes the following important tasks:

1. Cleaning around the most important bridge elementsCleaning and removing all sorts of debris, dirt, plants and bushes in and around the drainage channels,

the cable anchorage terminals, the tower base, the area around foundations, the area below the bridge entrance and the bridge access trails.

2. Fixing and re-tightening of bridge partsFixing and re-tightening of walkway wire mesh, nuts and bolts, bulldog grips, etc., which are loose.

3. Repairing the walkway deckRe-tightening of loose nuts and bolts of steel decks and J-Hooks.

4. Minor repairing of gabion boxes for bank and slope protection purposesInspection and checking of the slope and riverbank protection structures and execution of minor repair work.

5. Reporting of the bridge conditionInspection and checking the general condition of all the bridge parts and structures and reporting to the concerned DDC and/or VDC and seek their necessary support in case of big landslides, bank erosion, etc., which may damage the bridge foundations and structures or even cause the collapse of the bridge.

Chapter 7: Bridge Maintenance 111


Routine maintenance work can be carried out either by forming a Bridge Maintenance Committee (BMC) or by appointing a bridge warden. In both cases one trained person must be assigned for regularly inspecting the bridge. S/he should preferably live close to the bridge and should be equipped with some basic tools.

Primarily the concerned VDCs are responsible for ensuring that routine maintenance is done. The DDCs, who bear the overall responsibility, shall monitor the routine maintenance and shall support the VDCs for cases beyond their capacity.

7 . 3 Majo r Maintenance

Major maintenance (MM) work includes all works, which need proper - planning, survey, design and cost estimates. A certain level of knowledge and skill is required to execute the major maintenance of the bridges.

The major maintenance work includes the following tasks:

1. Replacing rotten wooden planks with galvanized steel decks.

2. Replacing rotten wooden crossbeams with galvanized steel beams.

3. Repairing of windguy arrangements/system.

4. Repair, adjustment or replacement of suspenders including adjustment of camber of for suspension bridges.

5. Re-painting of all non-galvanized steel parts.

6. Re-tensioning of all loose cables and adjusting bridge alignment.

7. Coaltar treatment of all non-galvanized threads.

8. River bank and slope protection works.

The existing bridges, which were constructed in the past with wooden walkway decks and non- galvanized steel, need in the first instance major maintenance work. These bridges may require almost all tasks mentioned above under major maintenance.

Major maintenance responsibilities are gradually operationalized at the district level by imparting technical know-how, methods and practices for carrying out maintenance work and providing material support. The DDCs are becoming better prepared to implement the major maintenance and are responsible for the execution independently or with the support of the Trail Bridge Section (TBS), or other concerned bridge building agencies.

Reference Documents for Maintenance:

A. Bridge Maintenance Concept, Suspension Bridge Division, DoLIDAR, HMG/N, August 2000.

B. Routine Maintenance Manual for Trail Bridges, Suspension Bridge Division, HMG/N 1999.

C. Directives on execution of Routine Maintenance of Main Trail Bridges through Bridge Wardens, Suspension Bridge Division, DoLIDAR, HMG/N, Shrawan 2057.

D. Local Bridge Repair, Maintenance and Management, BBLL, Kathmandu.

112 Chapter 7: Bridge Maintenance

Short Span T ra il B r id ge S tan d ard S u sp en d ed T yp e V olu m e II

V o l u m e I I : F o r m s(m a k e p h o t o c o p y fo r u s e )

F o r m N o . 1 F o r m N o . 2 F o r m N o . 3 F o r m N o . 4

S u r v e y F o r m & C h e c k l is t B r id g e D e s ig nQ u a n t it y & C o s t E s t im a t e fo r C o m m u n it y A p p r o a c h Q u a n t it y & C o s t E s t im a t e fo r P u b lic T e n d e r & C o n t r a c t in g

His Majesty's Government of NepalMinistry of Local Development SDC/Helvetas NepalDepartment of Local Infrastructure Trail Bridge Sub-Sector ProjectDevelopment and Agricultural Roads

Short Span Trail Bridge Standard Suspended Type Volume II

Form No. 1 : Survey Form & Checklist

His Majesty's Government of NepalMinistry of Local Development SDC/Helvetas NepalDepartment of Local Infrastructure Trail Bridge Sub-Sector ProjectDevelopment and Agricultural Roads


SURVEY FORM AND CHECK LIST(total 54 pages)

Crossing Name

River

District

Surveyed by

Date

His Majesty’s Government SDC /Helvetas NepalMinistry of Local Development Trail Bridge Sub-Sector ProjectDepartment of Local Infrastructure Development and Agriculture Roads

Short Span Trail Bridge Standard Volume II, Form No. 1

Table of Content

1. S u r v e y a n d B r id g e S ite S e l e c t io n ____________________________________________________________________________ 11.1 Socia l Feasib ility S u rv e y _____________________________________________________________________________________________ 11.2 Techn ica l S u rv e y _____________________________________________________________________________________________________ 2

2. P r e p a r a t io n fo r S u r v e y _____________________________________________________________________________________ 2

3. G e n e r a l Da t a C o l l e c t io n _________________________________________ __________________________________________ 23.1 Location o f Bridge S ite ________________________________________________________________________________________________ 23.2 Nature o f C rossing and Fordab ility_____________________________________________________________________________________ 43.3 T ra ffic V o lum e _______________________________________________________________________________________________________43.4 W idth o f W alkw ay_____________________________________________________________________________________________________ 43.4 Local P a rt ic ip a tio n ____________________________________________________________________________________________________ 53.5 T ransporta tion D is ta n c e _ _ ____________________________________________________________________________________________ 53.6 A va ilab ility o f Local M a te ria ls__________________________________________________________________________________________ 53.8 A va ilab ility o f Local B ridge B u ilde rs____________________________________________________________________________________ 63.9 Tem porary C ross ing______________ 6

4. Bridge S ite Selection ____________________________________________________________________________________ 64.1 G eneral C o n d it io n _________ 64.2 R iver C ondition______________ _ _ _ _ _________________________________________________________________________________ 114.3 S lope and Bank C ondition _ ^ _ _ _ ___________________________________________________________________________________ 124.4 Evaluation o f the B ridge S ite _ _ _ _ _ _____________________________________________________________________________ 234.5 C lassifica tion o f soil and R o c k ______ ________ 244.6 Identification o f Soil and R o c k ____________ 26

5. T opographic S urvey_ ____________________________________________________________________________________315.1 S urvey A re a _____________________ 315.2 Setting o f B ridge C en te rline ____________________________________________________________________________________ 315.3 Survey M e tho d s___________________________ 345.4 Survey by A bney Level _____________________________________________________________________________________________ 325.5 S urvey by T h e o d o lite ________ 38

6. P h o t o g r a p h s ________ ________________________________________________________________________________________________________46

7. Survey Re p o r t ___________ 53


1. S u r vey a n d B r id g e S ite S elec tio nSurvey and Bridge Site Assessment is the basis for planning and design and forms the main resource for bridge construction. The main objective of the Survey and Bridge Site Assessment is to identify the proper bridge site by considering socio -economic as well as technical points of view. Survey and Bridge Site Assessment is done in the following two stages:

Social Feasibility Survey and Technical Survey

1.1 S o c ia l F e a s ib il it y S u r v e y

A Social Feasibility Survey is necessary to justify the construction of a req uested bridge. For ranking and prioritizing the vast number of requests, the following socio-economic indicators are of utmost importance:

- Level of local participation - Size of traffic flow- Size of area of influence - Socio-economic benefits produced by the proposed bridge

One of the major indicators reflecting the real need of the bridge is the degree of participation by the local community or beneficiaries in the construction of the requested bridge. These indicators are assessed and measured fro m different points of view depending on the need and purpose of the bridge. A detailed Social Feasibility Survey is not included in this Technical Handbook, for further details refer to Social Organization Support (SOS) Manual.

Local Persons contacted:

Write down the names of local persons contacted or consulted during the survey work.

Name / Address Occupation

1 ....................................................................... ................................................................

2 ............................................................................... .....................................................................................

3 .............................................................. ..........................................................

4 .............................................................. ..........................................................

5 .............................................................. ..........................................................

6 .................................................................... ................................................................

Survey Form and Checklist 1


1.2 T e c h n ic a l S u r v e y

The technical survey includes: - Bridge site selection and- Topographic survey of the selected bridge site

2. P r e p a r a tio n fo r S u r v e y

The following preparatory work must be completed before going to the field for survey:

- Collect maps with tentative location of the bridge and any available background information.- Collect the survey equipment.

Survey equipment consists of the fol lowing materials:

For Survey by Abney Level- Abney Level, Survey Form & Checklist- Measuring Tape (50 or 100m and 3m)- Nylon Rope (Min. 50m)- Masons Thread and Plumb Bob- Red Enamel Paint and Paint Brush- Marker Pen, Scale and A3 Graph Paper- Camera and Film Roll- Hammer- Ranging rod (can be prepared at site also)- Note Book, Calculator & Pencil

3. G en e r a l Da ta C o lle c tio n

General data is required for needs assessment and construction planning of the proposed b ridge. Collect the following general data and information:

3.1 Lo c a tio n of B r id g e S ite

Left Bank Right Bank

VDC

Ward No.

Ilaka No.

District No.

Zone

For Survey by TheodoliteTheodoliteStaff and Plumb BobMeasuring Tape (50m and 3m)Red Enamel Paint and Paint Brush Marker Pen, Scale and A3 Graph Paper Camera and Film Roll HammerSurvey Form and Checklist Note Book & Pencil Calculator

2 Survey Form and Checklist


Draw a bridge site location map covering the proposed bridge’s area of influence as shown in the example below. The map should contain the following information:

• River system with names and river flow direction

• Location of proposed bridge and traditional crossing point

• Location of the nearest bridge (approximate walking distance from the prop osed bridge site)• Existing trail system and, if required, specify length of new trail for access to the proposed bridge

• Location of the next villages, health post, school and other important places with approximate distances from the bridge site

Bridge Site Location Map:___________________________________________________________ __________________________________________

tN



3 .2 N a t u r e o f C r o s s in g a n d F o r d a b il it y

Assess period of time the river cannot be crossed in one year?

........................... whole year

........................... months per year only

........................... days during high flood only

What type of crossing facility is available at present? .....

3 .3 T r a f f ic V o l u m e

Traffic volume at the crossing is one of the key indicators in the need assessment of the bridge. Information should be collected by 2 methods. Count traffic volume at the traditional crossing point for at least one day. And then interview the local people to form a broader impression of the traffic volume throughout the year.

Average number of traffic per day

Goods traffic PortersPack animals

Non-goods trafficPersonsAnimals

Determine the purpose of the traffic by interviewing the persons crossing and the local people as per the table below. This will indicate the importance of the crossing.

Access to Yes NoSchoolHealth post/HospitalBazaar/MarketPost office/TelephoneRoad headFarmingOthers (specify)

3 .4 W id t h o f W a l k w a y

The standard width of walkway in this handbook is 70 cm or 106 cm.In most cases the 70 cm walkway is sufficient. In stances of heavy traffic, mule and pack animal passage carrying bulky goods, or if the crossing is on a main trail, a 106 cm walkway is necessary.Discuss this issue with the local people, informing them that more work, especially collection of stones, is required for the 106 cm walkway.

Recommended width of walkway: 70 cm I I 106 cm I I



3 .5 L o c a l P a r t ic ip a t io n

Assess the availability of local participation for bridge building from within the concerned local communityBy Whom Type o f Participation/SupportLocal Community

User’s Committee

VDC

DDC

Local NGO

Individual

3 .6 T r a n s p o r t a t io n D is t a n c e

Type o f Ttransport Name o f nearest Roadhead/Airstrip etc. Distance from site up to Rroadhead/AirstripKm/Kosh Porter days By Mule, days

Served by TrucksServed by Tractors

Airstrip

Helipad

3 .7 A v a il a b il it y o f L o c a l M a t e r ia l s

Assess the availability of local materials needed for the bridge construction.*Do not overestimate hau age distance. Identify the nearest col ection place for stone, gravel and sand.Description H aulage Distance*, m Rem arks

StonesNatural GravelSandWoodBamboo

Tentative preliminary required number of mandays:

Mandays for skilled Labor: = 1.3 x span [m] + 400Mandays for unskilled Labor: = 5 x Span fm] + 1300



3 .8 A v a i l a b i l i t y o f L o c a l B r id g e B u i l d e r s

Are there any local bridge builders? If yes, record their names.

Names Skill (Mason, Bridge Fitter) Village /Address

3 .9 T e m p o r a r y C r o s s in g

Is temporary crossing is necessary during the construction of the bridge ?

If yes, what kind of temporary crossing do you propose? ____ Ferry

Yes

Cable car

No

Temporary bridge, m span.

4. B r id g e S ite S elec tio n

The main purpose of the technical field survey is to select the appropriate bridge site. The site should optimally serve the local people. The selected site must be economically justified and have along life span:

fulfill the general conditions (listed below) - have stable bank and slope conditions- have Favorable river conditions - have shortest possible span

4.1 G e n e r a l C o n d i t i o n

The bridge site should fulfill a number of general conditions:

- Traditional crossing point - Minimum free board- Maximum bridge span - Space for the bridge foundations

=> Use the checklist on following pages to evaluate the general condition at the survey site:



Features Condition Site AssessmentFavorable Unfavorable

Traditional crossing point

The bridge site should be selected at or near to the traditional crossing point.

Favorable: Selected site is at ornearby traditional crossing point

Unfavorable: Selected site is far from the traditional crossing point

• For minor river, detoure from the tradditional crossing point is not acceptable.• For major river, detour up to 500 m u/s and 500 m d/s from the traditional crossing point may be

acceptable.

Bridge span

At local level bridge can be built only up to 120 m span.

Favorable: span, t is equal orshorter than 120 m

Unfavorable: span, i is longerthan 120m

Approximate span m

• Measure tentative span.• Compare with the limit.




Level Difference between two BanksThe level difference between the two foundation blocks should not be more than £ ¡25.

Favorable: h is equal or lessthan £ ¡25

Unfavorable: h is bigger than £ ¡25

• Locate the tentative position of the bridge foundations at both banks.• Measure the level difference between the foundations of two banks.• Compare with the condition.

Space for Foundation

Foundation should be placed at least 3 m behind the soil slope and 1.5 m behind the rock slope.

Favorable: Condition can befulfilled

Unfavorable: Condition can not befulfilled



Slope Profile


Bridge foundation should be placed behind the line of the angle of internal friction. (Angle of internal friction is the angle of slope of soil or rock at which it is still stable and does not slide).

• Draw a slope line of 35° (angle of internal friction) in case of Soil slope and 60° in case of Rock slope.

• Foundation should be placed behind this line.

• Check if these conditions can be fulfilled.




Free BoardClearance between (Free board) the lowest point of the bridge and the highest flood level (HFL) should not be less than 5 m. For this, sufficient clearance between lower walkway saddle and HFL should be maintained.

Favorable Unfavorable

Clearance between lower foundation saddle and HFL is:

not less less thanspan than:

up to 55 m 7.5 m 7.5 m55 - 65 m 8.0 m 8.0 m66 - 85 m 9.0 m 9.0 m86 - 110 m 10.0 m 10.0 m

111 - 120 m 10.5 m 10.5 m

• Identify HFL by local observation and villagers’ information.

• Calculate available cleamace and compare with the requirement.

• Exception: At flat or wide river banks free board may be reduced.At gorge free board has to be increased.



4 .2 R iv e r C o n d it io n

The selected bridge site must have favorable river condition. Accordingly, a bridge should be loc ated:a) on a straight reach of the river, b) beyond the disturbing influence of larger tributaries, c) on well defined banks.

Use the following check list to evaluate the river condition:


River Flow

In order to protect the bridge from sudden over-flooding and strong erosion, the bridge site should not be located near the confluence area of two rivers.

Favorable: Bridge site far from the confluence

Unfavorable: Bridge site near theconfluence

River Bed

The river bed at the selected bridge site should be stable without the possibility of erosion or filling up with bed load (boulders, gravel, silt, or sand)

Favorable: River bed is noterosive not filling up

Unfavorable: River bed is erosive or filling up

River bed filled up after heavy flood



4 .3 S l o p e a n d B a n k C o n d i t i o n

A bridge should be located at the site with safe and stable slope and bank condition. The surveyor must identify any potential instability features or failure modes of the soil or rock slope and bank.

If the slope and bank is soil, potential instability features and failure modes are:

• bank erosion• toppling instability of the bank• erosion of the slope• land slide

If the slope and bank is rock, potential instability features and failure modes are:

• plain failures in a rock slide along the slope.• wedge failure leading to the fall of rock mass.• toppling, leading to the fall of rock blocks.• rotational slide, similar to the landslide in a soil slope. Such failure is likely when the material of the rock is very weak (soft rock) and the rock mass is

heavily jointed and broken into small pieces.

To avoid the above instability features, use the following checklist to evaluate the slope and bank of the selected site



Features

If the River Bank or Slope is SOILBank Profile

Bank profile should be smooth.

Condition Site AssessmentFavorable Unfavorable

Favorable: Bank profile is smoothto partially cut out

RB

LB

Unfavorable: Bank profile is strongly cut out

RB

LB


River Bank ContourThe bridge site should be located at the straight reach of the river to avoid the river from undercutting or bank erosion.

Favourable Unfavourable

Favorable: River contour isstraight or convex

Unfavorable: River contour is concave

Concave


* •Short Span Trail Bridge Standard Volume II, Form No. 1

Features

Bank ErosionThe river bank should not show sign of erosion.


Favorable: No Fresh erosion

Unfavorable: Presence of Fresh erosion

Bank erosion due to high river current

Slope Profile

Select applicable profile from pictures given below. The slope profile should be smooth.


Favorable: Slope profile issmooth to partially cut out

Unfavorable: Slope profile isstrongly cut out

RB

LB

RB

LB



Features

Transverse Slope

The transverse slope should be smooth.

Transverse slope strongly cut out

a a 1 a a1a 1’V _ rTTT^ X t t t t /

Partially cut out Strongly cut out

Slope Inclination

Slope inclination should be less than 35°.

Estimate the slope inclination and compare it with the condition. If the site has an unfavourable slope inclination, it can still be selected provided the general condition of slope profile is fulfilled._________

Condition

F avorable : Transverse slope is smooth topartially cutout

U nfavorable: Transverse slope is strongly cutout

Favorab le : Slope inclination is equal orsmaller than 35°

U nfavorable: Slope inclination is biggerthan 35°

Site AssessmentFavorable Unfavorable

RB

LB

RB

LB

RB

LB

RB

LB




River Undercutting

Bridge site should be free from river undercutting which may lead to landslide.

Landslide caused by river undercutting

Inclined Trees

Selected site should not have inclined trees which indicate an active land slide.

Inclined trees on landslide mass

F avorable : No river undercutting

U nfavorable: River undercutting is active or there is potential

RB

LB

RB

LB

Favorab le : Inclined trees not present RB

LB

U nfavorable: Inclined trees present RB

LB



Features

Seepage or Swampy Area

The bank slope should not have any seepage or swampy area which may lead to slope instability. Favorable:


Seepage or swampy area is absent

RB

LB

U nfavorable: Seepage or swampyarea is present

RB

LB

Gully Erosion

No signs of gully erosion should exist within the vicinity of the selected site.

Favorable: No sign of gully erosion or only light gully erosion

RB

LB

U nfavorable: Heavy gully erosion exists RB

LB

Active gully erosion

• Observe if any rivulets are within the vicinity of the selected site.• If rivulet exists, examine the dimension of the gully cutting.




Slipped (Slump) Soil Mass

The bridge should not be located on already slipped soil masses.

Slope with slipped soil mass

F avorable : There are no backscars or signs of soil mass movement

RB

LB

U nfavorable: There are back scars or signs soil mass movement

RB

LB

back scar

Slop failure model

• Examine and identify of soil mass movement by observing traces of back scars on the slope.




If the river bank is ROCKPlain FailurePlain failure leads to the slide of rock layers along the slope. The rock bank/slope of the selected site should not have any feature of plain failure.

Bedding plain is parallel to the slope and plain failure is active.

Site is extremely unfavorable.

S ide e leva tion P lan view S ide e leva tion

\ \ \ \ \\ \ \ \ \\ \ \ \ \

\ \ \ \ \\ \ \ \ \\ \ \ \ \\ \ \ \ \\ \ \ \ \

\ \ \ \ \

Bedding fracture Plane p a ra lle l to

th e slope

Sub parallel to the slope

'' Opposite to the slope

Identify bedding/fracture plain (layers of rock) Check its direction and inclination Compare with the condition_______________

F avorable :

Plain failure will not take place, if• Bedding/fracture plain is sub

parallel to the slope

• Bedding/fracture plain is parallel to the slope but inclination is less than 35°

U nfavorable:Plain failure will take place, if• Bedding/fracture plain is parallel to

the slope and inclination is greater than 35°

• Presence of old slided rocks

RB

LB

RB

LB

RB

LB




Wedge FailureAny form of wedge failure leads to sliding of rock masses. The rock bank/slope should not have wedge failures or potential wedge failures.

Trace of wedge failure

Direction of movement Fracture Plane

Identify if there are fracture plains facing each other (intersecting)Check the inclination of the intersection lineCompare with the condition_______________________________

Favorable:

Wedge failure will not take place, if• There are no fracture plains facing

each other

• There are two or more intersecting fracture plains but the inclination of its line of intersection is less than 35°

• There are two or more intersecting fracture plains but the inclination of its line of intersection is opposite to the slope

Unfavorable:

Wedge failure will take place, if• There are two or more intersecting

fracture plains and the inclination of its intersection line is more than 35° to the slope

Presence of old slided wedge

RB

LB

RB

LB

RB

LB

RB

LB



Features

Toppling FailureThe rock bank/slope should not have any features of toppling failure.


Potential toppling failure

To p lin g Fa ilu re model

Favorable:

Toppling will not take place, if• the Rock slope is less than 60°

• there is no formation of rock blocks

• there is formation of rock block but b/h (width of the block/height of the block) is > 1

Unfavorable:

Toppling will take place, if• there is formation of vertically

elongated rock blocks in the steep slope > 60° and the blocks are tilted towards slopes

• old toppled rock blocks are present

RB

LB

RB

LB

• Identify if there is formation of vertically elongated rock blocks (cubes) due to vertical and horizontal fracture planes/joints

• Estimate inclination of the slope• Estimate inclination and orientation of the rock block and compare with the conditions



Features

Translational Failure (Slide)The rock slope should not have any potential of translational failure.


Translational failure (sliding) of soft rock slope

failure(slide) model

• Identify type of rock and its weathering grade• Estimate inclination of the slope• compare with the conditions

Favorable:

Sliding will not take place, if• slope is hard rock

• slope is soft rock but not weathered

• slope is soft rock and weathered but not steeper than 40°

Unfavorable:

Sliding will take place, if• Slope is highly weathered soft rock

and steep > 40°

• Presence of back scar or old slide



4 .4 E v a l u a t io n o f t h e B r id g e S it e

After completing investigation o f the site as per chapter 4.1 to 4.3, categorize the bridge site as

Good | | Questionable | | Bad | |

Good

Questionable

Bad

All or most o f the features are favorable and if the surveyor is confident about the stability o f the slopes. Proceed with further survey work.Most o f the features are favorable and some are unfavorable. The site is questionable. In this case, further detailed investigation by an experienced geo-technical engineer is necessary. For detail refer to the SBD Survey Manual.M ost o f the features are unfavorable. Reject site.

As far as possible, the bridge site should be selected at a location where protection works will not be required. If protection works are unavoidable determine the required special structures like retaining walls, drainage channels, etc. A tentative design with dimensions and location o f these structures should be illustrated in a sketch showing a plan view and a typical section. But it is best to avoid bridge sites which require r iv e r protection works.

W rite down remarks, if any and note also proposed spec ial structures, if necessary: retaining walls, gabion walls, drainage, lining o f existing irrigation canal, river protection works etc. Mention height, length and location o f these structures and also reflect it in the sketch o f plan (page no 34).

Rem arks:



4 .5 C l a s s if ic a t io n o f s o il a n d R o c k

Identification o f Soil and Rock type is required for appropriate foundation design. Soil and Rock can be broadly classified and categorized for the foundation design proposes as per the following tables.

Soil Typ e H ow to identifySoil Parameters U n it

W eighty, kN/m3

ApplicableFoundation

DesignBearing capacity

kN/ m2Angle of internal

Friction, cp°

Coarse G ra ined SoilsMore than half o f the materials are individual grains visible to the naked eye (grain size bigger than 0.06 mm)

G ra ve llySoils

Estimate the percentage (%) of coarse grains larger than 6 mm

If, more than half of the coarse fraction is larger than 6 mm, the soil is Gravelly Soil

400-600(400)

32-38(35)

19

Dead

man

A

ncho

r

SandySoils

If, more than half of the coarse fraction is smaller than 6 mm grain size, the soil is Sandy Soil

200-300(200)

31-37(33)

18

Fine Gra ined SoilsMore than half o f the materials are individual grains not visible to the naked eye (grain size smaller than 0.06mm)

S iltySoils

Prepare moist soil ball from the soil sample and cut it with a knife. If, the cut surface is dull or scratched, the soil is Silty Soil

150-200(150)

30-32(30) 17

C la yPrepare moist soil ball from the soil sample and cut it with a knife. If, the cut surface is smooth and shiny, the soil is Clay.

100-200(100)

9-25(22) 16

For estimation o f percentage (%) o f coarse grain use the figure.

Ratio of coarse grains

•d•« ••

k j %+ * m «

* V£ 0

0 . *

1 ♦ sq* %• • fm Ê% m•

' : • & -m

* V -‘ : *4v-: m 2 •• p i* Lim0• 0

. * m

mm

•• : ? ft ** t

a \ y *

|2C-— X

1 *‘ *%\% *% p ft

' i * •* ♦ r%i 0m- •

:y 0 • «

r#j

♦ . ».W ¿îî- V.

te s » ;



Rock Classification

Degree of Fractures or Weathering

Rock ParametersRockType Examples How to

identify How to identify BearingCapacity,

kN/m2

Angle of Sliding

Friction, cp°

Applicable Foundation Design

■O ¿4 u a 03 ©

Quartzite

Limestone

Granite,

Dolomiteetc.

Gives metallic sound after

Rock is sound and fresh to fairly weathered

Rock has no sign of weathering or only faint signs of weathering up to 1-5 cm thickness

1500-2000(1500)

35-50(40) Drum Anchor in Hard Rock

X X hammerblow Highly fractured

rock and fresh to fairly weathered

In the rock exists widely open cracks, fractures and bedding

1500 35-50(40)


u (

Phylite

SlateGives dull

Fresh No sign of weathering 1300 25-40(30)


waao

Cfl

Siltstone

Claystone

Schistetc.

sound afterhammerblow Fairly to highly

weathered

• Most of the original rock has been seriously altered

• Rock can be broken by hand

600-750(650)

25-40(30) Deadman Anchor



4 .6 Id e n t if ic a t io n o f S o il a n d R o c k

Excavate a test pit with a depth of up to the estimated foundation level (but not less than 2.0m) or up to the bed rock at the proposed foundation locations. If the bank/slope is soil, investigate each layer of soil in the pit and classify according to the Soil Classification chart, filling in the soil investigation table as per the following example.

R ight Bank (at location of Main Anchorage Block) ________________ _________ ___________________________________ S O IL

SketchDepth from Surface, m

Soil Typ e

Soil Param eter

Rem arksBearing

Capacity,kN/m2

Angle of In terna l

F ric tio n , cp

U n itW eight

y, kN/m3

Left Bank (at location of Main Anchorage Block)_____ __________________________________________________________________ S O IL


Soil Typ e

Soil Param eter

Rem arksBearing

Capacity,kN/m2

Angle of In te rna l

F ric tio n , cp

U n itW eight

y, kN/m3


R ight Bank (at location of windguy block of up stream)_______________ __ _______________________________________________________________________ S O IL __________



Soil Typ e

Soil Param eter

Rem arksBearing

Capacity,kN/m2

Angle of In terna l

F ric tio n , cp

U n itW eight

Y, kN/m3

Left Bank (at location of windguy block of up stream) S o i l


Soil Typ e

Soil Param eter

Rem arksBearing

Capacity,kN/m2


F ric tio n , cp

U n itW eight

Y, kN/m3


Right Bank (at location of windguy block of down stream)_______________________________________________________________________________________ S O IL __________



Soil T yp e

Soil Param eter

Rem arksBearing

Capacity,kN/m2


F ric tio n , cp

U n itW eight

Y , kN/m3

Left Bank (at location of windguy block of down stream)________________________________________________________________________________________ S O IL


Soil T yp e

Soil Param eter

Rem arksBearing

Capacity,kN/m2

Angle o f In te rna l

F ric tio n , cp

U n itW eight

Y, kN/m3


If the bank/slope is rock, investigate the rock type according to the Rock Classification chart, filling in the following rock investi gation table.


R ight Bank (at location of Main Anchorage Block)_________________________________________________________________________________________________ R O C K

Rock TypeDegree of

F racture/W eathering

Rock Param eter

Applicable Foundation Design Rem arksBearing

Capacity,kN/m2

Angle of S lid ing

F ric tio n , cp°

Left Bank (at location of Main Anchorage Block)__________________________________________________________________________________________________ R O C K

Rock TypeDegree of

F racture/W eathering

R ock Param eter

Applicable Foundation Design Rem arksBearing

C apacity,kN/m2

Angle o f S lid ing

F ric tio n , cp°



Right Bank (at location of windguy block of up stream) ROCK

Left Bank (at location of windguy block of down stream) R o c k



5. T o p o g r a p h ic S u r vey

After final selection of the bridge site, the surveyor proceeds with the topographic su rvey. The purpose is to:

• provide a topographic map of the bridge site with details relevant to the bridge design• establish axis pegs and bench marks for use during construction of the bridge

5.1 S u r v e y A r e a

Area to be covered by the topographic survey:,

• A profile along the bridge axis covering up to 25m behind the main anchorage blocks, for bridges w ithout w indguy arrangement.

• A profile along the bridge axis covering up to 25m behind the main anchorage blocks and a topographic plan covering the area of 10m up stream and 10m downstream from the tentative location of the windguy foundations; for bridges w ith w indguy arrangement

5 .2 S e t t in g o f B r id g e C e n t e r l in e

Fix the bridge centerline with two permanent axis points L on the left bank and R on the right bank. Permanent axis points L and R should be fixed on rock out crop along the bridge centerline, if available. If rock out crop is not available, these points should be marked on a boulder sufficiently embedded into the ground as per the sketch below:

Chiseledhole OR

Additional survey points along the centerline should be fixed to survey the bridge axis profile as shown in the sketch below. These survey points should be fixed at breaking points of slope and terraces, which will accurately indicate the t opography of the bridge axis. The profile should cover 25m behind the main anchorage block up to the edge of the river flow.


Volume II, Form No. 1

• • •Short Span Trail Bridge Standard

5 .3 S u r v e y M e t h o d s

There are two options for conducting the topographic survey. Depending upon the span and type of bridge, a profi le along the bridge axis or a more detailed survey including contour lines will be necessary.

• Profile along the B ridge axis:Generally bridges up to 120 m do not need windguy arrangement. A detailed profile along the selected bridge axis is sufficient f or this bridge design. A topographic profile can be taken by the Abney level, however for fixing precise levels a Level Instrument is necessary.

• For bridges over 120 m span, a Theodolite should be used to carry out the topographic survey.

5 .4 S u r v e y b y A b n e y L e v e l

The main function of the Abney Level is to measure the vertica l angle cp. By measuring the slope distance d between the survey points with a measuring tape, the horizontal distance D and the vertical difference of elevation AH can be calculated.The principle of measuring the vertical angle by the Abney Level is illustrated in the sketch and procedure described below:

To take a profile along the bridge axis, the surveyor should first set the exact centerline as described in chapter 5.2. Ther e are two methods of setting the centerline.B y measurement tape o r nylon rope and plum b bob:This method is accurate enough for span up to 50m. The survey points along the bridge centerline are fixed with the help of a measurement tape or nylon rope and a plumb bob as per procedure shown in the sketch below.



B y Bamboo or W ooden Sticks or R anging Rods:This method is applied for span above 50m. In this method the survey points along the bridge centerline are fixed with the help of Bamboo or Wooden Sticks or Ranging Rods. Fix a Stick at each axis point L and R in vertica l position. Now the surveyor can aim at other points along the bridge centerline line of L and R. By fixing in line additional survey points behind and in front of L and R, more points can be gained along the bridge centerline ranging as per the procedures shown in the sketch below:

Proceed with the survey of bridge profile after having fixed the centerline. Measure the vertical angles and sloped dista nces between the points of the centerline. The measured vertical angle between axis points L - R and R - L should be checked for error correction.

The "error-factor" is calculated with the following formula:

E - (-^¿/?)+ (- V r l ) _ ±e ; Corrected angle cp' = cp ± E 2

Compute the horizontal distances and elevations of the corresponding survey points with the corrected vertical angles as per trigonometry.

Enter the measurements and calculations into the Bridge Axis Profile by Abney Level sheet.



# • •Short Span Trail Bridge Standard

Draw a plan view with the bridge axis (centerline), axis points L and R , with all the benchmarks and fixed objects like trees, houses etc. Give distances and directions from the reference points so that the axis points and benchmarks can be located during the construction. A plan view is necessary only when a windguy arrange ment needs to be considered in bridge design.

Plan(indicate river flow and north direction)



Draw a sketch of the profile/cross section of the bridge axis (centerline) with axis points L and R, with all the survey points and topographic features, including tentative position of the bridge foundations, low water level and high flood level.

Profile/Cross Section



BRIDGE AXIS PROFILE BY ABNEY LEVEL Page No. 1

Bridge Name : District: Surveyed by : Date :Horizontal Distance, P

D = d x Coscp'AH = d x Sintp'H = R.L. of Station ± AH

STATION POINTS

SLOPEDISTANCE

dm

VERTICALANGLE

<P

CorrectedVERTICAL

ANGLE<p'

HORIZONTALDISTANCE

Dm

VERTICALDISTANCE


Hm

REMARKS (Description of

Points)± ah

Remarks: 1. Applicable only for suspended type bridge up to 100m span and suspension type up to 70m.2. For other cases use Theodolite.



BRIDGE AXIS PROFILE BY ABNEY LEVEL| Bridge N am e: District: Surveyed b y : D ate:

STATION POINTSSLOPE

DISTANCEdm

VERTICALANGLE

<P

CorrectedVERTICAL

ANGLE<p’

HORIZONTALDISTANCE

Dm

VERTICALDISTANCE


Hin

REMARKS (Description of

Points)± aH

Page No. 2




S u r v e y b y T h e o d o l i t e

When the span of the bridge is more than 120 m or when a windguy arrangement needs to be included in the bridge design, the survey is conducted with a Theodolite.

For proper use of a Theodolite, refer to the respective instruction manual, that comes with the Theodolite, and to the SBD Survey Manual .

Profile A long Bridge A x is :Fix the bridge centerline as described in chapter 5.2. Measure distance between the axis points L and R by horizontal triangulation method. Triangulation is done by measuring all three angles of a triangle and length of one si de as illustrated in the sketch below. For accuracy double triangulation is necessary.

C

LJA)

Insert all the readings in the Tria ng u la tio n Survey Form and calculate distance between axis points L and R by trigonometry formulas given therein.

Elevation o f A xis Points and Benchm arks:It is necessary to establish the elevations of Axis Points L and R and Benchmarks. Select elevation of one of the Bench mark BM i as 100.00m. Establish elevations of axis points and other benchmarks by vertical triangulado n as illustrated in the sketch below.

Insert the readings in the Survey form of Sum m ary o f T ria ng u la tio n and Elevations o f Pegs and Benchm arks and calculate the Elevations (reduced levels) of the points by trigonometry formulas given ther ein.



T R I A N G U L A T I O N

Bridge Name : District :

1st Triangulation

di = ----------d2 = ----------d3= ----------

a = a 0 + A/3 ß = ßo±A/3 r = Yo± a/3

If ô > + 0.02s or 0.018° repeat the angle readings

Sketch:

n dmean x Sin ySin ß

Survey Form and Checklist


Surveyed by : Date

2nd Triangulation

d ,=d2 = d3 = d,

Sketch:

mean — D = dme Sin ySin ß

H O R IZO N TA L C IR CLE

FACE R IG H T FACE LEFT

A N G LE

FACE R IG H T FACE LEFT

Ö = 0to + ß0 + Yo =

M E A N

an

= ßo

Yo

A = (200g or 180°)-5 =a = a 0 ± A/3 =P = ßo±A/3 Y = y0±A/3

If 5 > ± 0.028 or 0.018° repeat the angle readings

39


SUMMARY of TRIANGULATION and ELEVATIONS of PEGS and BENCHMARKSBridge Name : District : Surveyed by : Date

1. Summary of Triangulation

1st Triangulation D, 2nd Triangulation D2 Difference AD

Mean Distance D = =2

AD/D =

If AD/D> 0.0025 repeat the triangulation

REDUCED LEVELS: BMI BMII A B

= 100.00

2. Elevation

V = D x tan cp

B M I

B M I

Dtan ß

AH = V-Z + I

AH = V + Z -I

zU. 2 u. H < < H H

___ Ç/5

B M I

B M I I

Zw1 Hg SCH a2 35 X NN

m cm

u§ ssi g sim cm

VERTICAL ANGLE

F A C E R IG H TF A C E L E F T

M E A N

(L e ft + R ight) 2

Wuz<HCAO >

D IF F E R E N C E IN E L E V A T IO N

AH M E A Nm cm



Topographic Detail Survey:Topographic detail survey is necessary to represent the topography of the bridge site by means of the contour lines. This is done by tacheometric su rvey. Tacheometric survey is done by Theodolite with stadia hairs and leveling staff. The horizontal, vertical distances and position of the points are measured by horizontal and vertical angles and stadia hair readings as illustrated in the sketches below .

The survey points should be taken at break points of slopes, terraces, fields and other features representing the actual topography of the ground as shown in the sketch .

® Points to be measured

Insert all the readings in the Tacheometry Survey Form and calculate the horizontal distances and elevations by the formulas given therein.

Check the stadia hair of the Thedolite before the survey. For this measure a distance of about 40m by stadia readings and actual measurement by a tape. If the difference between stadia measurement and tape measurement is more than 0.2%, corrections on calculation of horizontal and vertical distance should be applied. The distances should be corrected for error A as per following Formula.

D = (100x1+A) x Cos2<p V = (50xl+A) x Sin2(p



TACHEOMETRY P a g e N o. 1

Bridge Name :_______________________________ District :______________________ Surveyed by :_________________________ Date :









6. P h o t o g r a p h s

Photographs of the bridge site to support its technical feasibility / topography and faci litate the bridge design.Take following photographs:

• Overall view of the bridge site from upstream indicating approximate location of bridge foundations and axis line• Overall view of the bridge site from down stream indicating approximate location of bri dge foundations axis line• View of the right bank from left bank with approximate location of bridge foundations• View of the left bank from right bank with approximate location of bridge foundations• Over all top view (if possible)• Close up view of axis points and bench marks• Soil test pits at the location of bridge foundation blocks• Other relevant photos

Take above photographs from the positions as per sketch below. If one picture does not cover the necessary area, take several pictures from the same spot with sufficient overlapping.

Present all the photographs on the following blank pages.



;

1. Overall view of the bridge site from upstream (with approximate location of bridge foundations on both R/B & L/B and axis line)

2. Overall view of the bridge site from downstream (with approximate location of bridge foundations on both R/B & L/B and axis line)



3. Overall view of the right bank (with approximate location of bridge foundatio n and axis line)

4. Overall view of the left bank (with approximate location of bridge foundation and axis line)



5. View of the right bank with proposed location of bridge foundation

7. View of Axis Peg/Left Bank



6. View of the left bank with proposed location of bridge foundation

8. View of Axis Peg/Right Bank

49


9. View of Bench Mark

11. Pit excavation at











16.

51

• •Short Span Trail Bridge Standard

17.

19.

52




# # •Short Span Trail Bridge Standard

7. S u r vey R e p o r tThe technical survey report consists of:

• Filled in Survey Forms and Checklist

• Topographic map

1. Profile along the bridge axis in scale2. Contour plan of the bridge site in scale ( only, if windguy arrangement is necessary)



Note Pad


His Majesty’s Government SDC / Helvetas NepalMinistry of Local Development Trail Bridge Sub-Sector ProjectDepartment of Local Infrastructure Development and Agriculture Roads

Short Span T ra il B rid ge S tan d ard S u sp en d ed T yp e V o lu m e II

His Majesty’s Government of Nepal Ministry of Local Development Department of Local Infrastructure Development and Agricultural Roads

Form No. 2 : Bridge Design

SDC/Helvetas Nepal Trail Bridge Sub-Sector Project

Short Span T ra il B r id ge S tan d ard S u sp en d ed T yp e V olu m e II

Form No. 2

Bridge Design 1. Cable Design

2. Anchor Block Design

3. Bridge Standard Drawings

Bridge Name:

River Name:

District Name:

Designed by:

Date:

His Majesty's Government of NepalMinistry of Local Development SDC/Helvetas NepalDepartment of Local Infrastructure Pedestrian Trail Bridge ProgrammeDevelopment and Agricultural Roads


Bridge N o : ................Bridge Name :............................................District:.........................................

Span:......................m, Walkway Width (70 or 106):.........................cm

1. Cable Design for Suspended Bridge TypeA. Survey Data and Calculation of Freeboard

1.

2.

3.

4.

5.

6.

7.

8.

Span of the Bridge i = ...................m

Saddle Elevation of the Walkway Cable on the higher Side E h = ...................m

Saddle Elevation of the Walkway Cable on the lower Side E , = ...................m

Difference in Elevation(max. permissible height: hmax = £125)

h — E h “ E * —

. _ tbd — — — 20

h ...................m

Dead Load Sag: for Span up to 80m: bd = ...................m

for Span over 80m:- é -

bd = ...................m

f min in Dead Load Case (at the lowest point of the cable)

, (4 bd -h )2 mm 16 bd

f m i n ...................m

Highest Flood Level H f , = ...................m

Free Board (min. 5.00m) Fb = E j - H f i - f min = Fb = ...................m

( i f the fr e e b o a r d is less than 5.00m, try eith er to ra ise the sa d d le e leva tion s o r to ad ju st the span, but keep the ra tio betw een span an d s a g a lw a ys fixed at / / b(j =20 o r / / b r f -22)

Form No. 2: Bridge Design 1


B. Selection of Cables

Select a cable combination according to the span and walkway width of the bridge. Always select the higher cable combination, when the span is in between two values.

Maximum Span for Walkway Width:

70cm 106cm

Cable Combinations

Handrail Walkway Cables Cables

Weight of all Cables

gh

span [m] span[m] nos 0mm nos 0mm [kg/m]

50 40 2 26 2 26 10.04

90 60 2 26 2 32 12.62

100 75 2 26 4 26 15.06

120 105 2 26 4 32 20.22

— 120 2 32 4 32 22.80

Above cable combinations are calculated for the following specifications:

Cables: construction 7x19, wire strand core, 160 kg/mm2 (1.57 kN/mm2) tensile strengthof wireSafety Factor: minimum 3 or higher than 3Live load p= (300 + 5222.) kg/m2 or (3 + - ^ - ) kN/m2

r v span 7 0 v span

or p= 400 kg/m2 (4 kN/m2) if the span is 50.0 m or less

Sag to Span Ratio: = 20 for Spans up to 80 meters(in dead load case) = 22 for Spans over 80 meters

spatMax. permissible Height Difference of Saddles: h = ----

25

Example: w idth o f w a lk w a y = 70cm ;=> se le c te d ca b le com bin ation :

span = 88mH a n d ra il C ab les 2 26m m W alkw ay C a b le s 2 0 32m m W eigh t o f C a b le s = 1 2 .6 2 k g /m

Selected Cable Combination and Parameters from the Table above:

HRC Handrail Cables: nos 2 0 ......mm

WWC Walkway Cables: nos 0 ......mm

Weight of all Cables per meter ...........kg/m

2 Form No. 2: Bridge Design


C. Calculation of Cable Length

Type of Cable Dia (mm) NosBackstay Length *

[m]

Cutting Length**

[m/pc]

Fixation Cable 13 2

Handrail Cable 2

Walkway Cable

* Backstay Length = Cable length between saddle center and center of dead man or drum as per foundation drawing(both banks) + 6.0m. Calculate backstay length after selection of foundation blocks.

**Cutting Length = 1.1 x Span + Backstay Lengths

D. Calculation of ( fmin & fmax )Hoisting SagThis calculation has to be made after tower and foundation work is completed



2. Anchorage Type (Foundation) Design for Suspended Bridge TypeA. Design Data W Fill in the following Design Data from Form No. 1: Survey Form and Checklist

• Walkway Width, WW (70 or 106cm): ................ cm

• Bridge Span: ................ m


Geology: Soil □

If Soil, how is the Ground Surface? Flat(up to 10° slope)

or Hill Slope 1 1 (more than 10° slope)

What is the Soil Type? Gravelly | | Sandy □ Silty □Tower Height from Ground up to H.C.Saddle (data from bridge profile):

2.4m Q 3.4m □ 4.4m □If Rock, what is the Rock Type? Hard Rock | | Hard Rock □ Soft Rock □


Tower Height 2.0m in Case of Rock □Left Bank Condition

Geology Soil | |

If Soil, how is the Ground Surface? Flat(up to 10° slope)

or Hill Slope d H (more than 10° slope)

What is the Soil Type? Gravelly | | Sandy □ Silty □Tower Height from Ground up to H.C.Saddle (data from bridge profile): 2.4m □ 3.4m □ 4.4m □If Rock, what is the Rock Type? Hard Rock 1 1 Hard Rock □ Soft Rock □


Tower Height 2.0m in Case of Rock □B. Selection of Anchorage TypesSelect appropriate anchorage type at Right and Left Bank according to the above design data.

Procedure for Selection:• According to the Soil/Rock type and Slope of the ground, refer to respective tables for selection of

Anchorage Types as per below.for Soil and Flat Ground : Table 1for Soil and Hill Slope : Table 2for Hard Rock : Table 3 or Table 4for Fractured Hard Rock or Soft Rock:Span up to 90m (WW = 70cm) and up to 60m (WW = 106cm) : Table 5 or Table 6 Span Range 91-120m (WW = 70cm), 61-120m (WW = 106cm): Table 7

• In the Table match the Design Data: Selected Walkway Width —> Bridge Span —> Tower Height -» Soil Type —» Select the corresponding Anchor Type and Drawing No. for right bank and for left bank respectively.



Anchor Type Selection Tables

• In Soil and Flat Ground:Ta b le 1: Selection of Gravity Soil Anchor Block in Flat Ground


[ml

Foundation Soil Type Block Type Drawing

No.Walkway:70cm Walkway: 106cm

Up to 45m Up to 30m2.4

AllIF 21Dcon

3.4 2F 22Dcon4.4 3F 23Dcon

46-90 31-602.4

All4F 24Dcon

3.4 5F 25Dcon4.4 6F 26Dcon

91 - 120 61-752.4

All7F 27Dcon

3.4 8F 28Dcon4.4 9F 29Dcon

- 76-902.4

All10F 30Dcon

3.4 8F 28Dcon4.4 1 IF 31Dcon

- 91 - 1052.4

All12F 32Dcon

3.4 8F 28Dcon4.4 13F 33Dcon

- 106-1202.4

Gravely 12F 32DconSandy, Silty 14F 34Dcon

3.4All 15F 35Dcon

4.4 13F 33Dcon

• In Soil and Slope Ground:Ta b le 2: Selection of Gravity Soil Anchor Block in Hill Slope


[ml


BlockType

DrawingNo.Walkway:70cm Walkway: 106cm

Up to 60m Up to 40m 2.4 All IS 41Dcon6 1-90 41-60 2.4 All 2S 42Dcon91 - 120 61-75 2.4 All 3S 43Dcon

- 76-90 2.4Gravely 4S 44DconSandy 5S 45DconSilty 6S 46Dcon

- 91 - 105 2.4Gravely, Sandy 7S 47Dcon

Silty 8S 48Dcon

- 106- 120 2.4Gravely, Sandy 8S 48Dcon

Silty 9S 49Dcon



• In H ard R ock fo r a ll Span R anges:Table 3: Selection of RCC Single Drum Anchor in Hard Rock

Span Range, m Tower Height [m] Block Type Drawing

No.Walkway:70cm Walkway: 106cmup to 90 up to 60 2.0 1HRS 61Dcon91 - 120 61 - 120 2.0 2HRS 62Dcon

When slope is too steep and there is not enough space for single drum anchorage system (Table 3), select the double drum system from following table 4.Table 4: Selection of RCC Double Drum Anchor in Hard Rock


No.Walkway:70cm Walkway:106cmup to 90 up to 60 2.0 1HRD 63Dcon91 - 120 61 - 120 2.0 2HRD 64Dcon

• In Fractured H ard Rock/Soft Rock fo r Span Range up to 90m (W W = 70 cm) and 60m (WW = 106cm):

Table 5: Selection of RCC Single Drum Anchor in Fractured Hard Rock/Soft Rock



up to 90 up to 60 2.0 IFRS 65Dcon

When slope is too steep and there is not enough space for single drum anchorage system (Table 5), select the double drum system from following table 6.Table 6: Selection of RCC Double Drum Anchor in Fractured Hard Rock/Soft Rock



up to 90 up to 60 2.0 1FRD 66Dcon

• In Fractured H ard Rock/Soft Rock fo r Span Rang o f 91 - 120m (W W = 70 cm) and 61-120m (W W = 106cm):

Table 7: Selection of RCC Deadman Anchor in Fractured Hard Rock/Soft Rock


No.Walkway:70cm Walkway: 106cm91-120 61-120 2.0 2FRD 67Dcon

Selected Anchorage Foundation Type and corresponding Drawings from the Table above:

Right Bank: Anchor Type ........................ Drawing No

Left Bank: Anchor Type ........................ Drawing No



Example:

Design Data

Fill in the following Design Data from Form No. 1: Survey Form and Checklist

• Walkway Width, WW (70 or 106cm): ....... 7Q...... cm

• Bridge Span: .......§§...... m


Geology:

If Soil, how is the Ground Surface?

What is the Soil Type?

Tower Height from Ground up to H.C.Saddle (data from bridge profile):

Soil LZH Flat l~71(up to 10° slope)

Gravelly 1 ^ 1

2.4m □

or

Sandy

3.4m | J |

Hill Slope 1 1 (more than 10° slope)

Silty 1 1

4.4m [ ^ ]

If Rock, what is the Rock Type?

Tower Height

Hard Rock | [ (only few fractures)

Hard Rock | | (highly fractured)

Soft Rock | |

2.0m in Case of Rock [ 1

L e f t Bank Condition

Geology

If Soil, how is the Ground Surface?

What is the Soil Type?

Tower Height from Ground up to H.C.Saddle (data from bridge profile):

Soil | |

Flat(up to 10° slope)

Gravelly [ |

2.4m Q

or

Sandy

3.4m □

Hill Slope \Z Z \ (more than 10° slope)

Silty

4.4m Q J

If Rock, what is the Rock Type?

Tower Height

Hard Rock | • /

(only few fractures)Hard Rock [ ^ ] (highly fractured)

Soft Rock | |

2.0m in Case of Rock | / |

=> Selected Anchorage Types:

Right Bank: Block Type 5F, Drawing No. 25DconLeft Bank: Drum Type 1HRS, Drawing No.61Dcon



3. Bridge Standard DrawingsSelect the required Steel Drawings and Construction Drawings from the following Drawing List.

3.1 Steel Drawings

Drawing Title Drawing No RequiredDrawing

Walkway Cross Beams02D or 02D4 or 03D or 03D4

Saddle and Reinforcement for RCC Deadman and Gravity Soil Anchor 20D2 or 20D4

RB

LBSaddle and Reinforcement for RCC Deadman Anchor in Soft or Fractured Hard Rock

20D4SRB

LB

Saddle and Reinforcement for Drum Rock Anchor 60D2 or 60D4

RBLB

Steel Deck 08A, 09A and 10A 08A, 09A, 10A

3.2 Construction Drawings

Drawing Title Drawing No RequiredDrawing

Walkway Fitting 19Dcon70 or 19Dconl06Details of Cement Stone Masonry Tower & RCC Core

20Dcon70 or 20Dconl06

RCC Deadman and Gravity Soil Anchor Block for Flat Ground

21Dcon.............35 DconRBLB

RCC Deadman and Gravity Soil Anchor Block for Hill Slope

41Dcon.............49DconRBLB

RCC Single Drum Rock Anchor in Hard Rock

61 Dcon or 62DconRBLB

RCC Double Drum Rock Anchor in Hard Rock

63 Dcon or 64DconRBLB

RCC Single Drum Rock Anchor in Soft or Fractured Hard Rock

65DconRB

LB

RCC Double Drum Rock Anchor in Soft or Fractured Hard Rock 66Dcon

RBLB

RCC Deadman in Soft or Fractured Hard Rock

67DconRBLB

Designed b y : ............................................................... Date:

Cable hoisted b y : ....................................................... Date:



Exam ple:

=> Selected D raw ings

Steel D rawings

D raw ing Title D raw ing NoR equiredD raw ing

W a lk w a y C ro ss B ea m s 0 2 D o r 0 2 D 4 o r 0 3D , o r 0 3 D 4 02D

S a d d le a n d R e in fo rcem en t f o r R C C D ea d m a n a n d G r a v ity S o il A n c h o r

2 0 D 2 o r 2 0 D 4R B : 20D 2

LB: x

S a d d le a n d R e in fo rcem en t f o r R C C D ea d m a n A n c h o r in S oft o r F ra c tu re d H a rd R o ck

2 0 D 4 SR B : x

LB: 60D2

S a d d le a n d R e in fo rcem en t f o r D ru m R o ck A n ch o r

6 0 D 2 o r 6 0 D 4RB: 60D2

LB: x

S te e l D eck 08A , 09A , 10A 08A, 09A,

Construction D rawings

D raw ing Title D raw ing NoR equiredD raw ing

W alkw ay F ittin g 1 9 D c o n 7 0 o r 1 9 D c o n l0 6 19D con70

D e ta ils o f C em en t S to n e M a so n ry T o w e r & R C C C o re 2 0 D c o n 7 0 o r 2 0 D c o n l0 6 20D con70

R C C D ea d m a n a n d G ra v ity S o il A n c h o r2 1 D co n . .......... 3 5 D co n

R B: 25D conB lo ck f o r F la t G ro u n d LB: X

R C C D ea d m a n a n d G ra v ity S o il A n c h o r41 D con . .......... 4 9 D co n

RB: X

B lo ck f o r H ill S lo p e LB : X

R C C S in g le D ru m R o ck A n c h o r6 1 D co n o r 6 2 D c o n

R B : X

in H a rd R o ck LB : 61Dcon

R C C D o u b le D ru m R o ck A n c h o r6 3 D co n o r 6 4 D c o n

R B : X

in H a rd R ock LB : X

R C C S in g le D ru m R o ck A n c h o r6 5 D c o n

RB: X

in S oft o r F ra c tu re d H a r d R o ck LB: X

R C C D o u b le D ru m R o ck A n c h o r6 6 D c o n

RB: X

in S o ft o r F ra c tu re d H a r d R o ck LB: X

R C C D e a d m a n in in S oft o r F ra c tu re d6 7 D co n

RB: X

H a rd R o ck LB: X



Form No. 3 : Quantity & Cost Estimatefor Community Approach

His Majesty’s Government of NepalMinistry of Local Development SDC/Helvetas NepalDepartment of Local Infrastructure Trail Bridge Sub-Sector ProjectDevelopment and Agricultural Roads


Form No. 3

Quantity & Cost Estimate

for Community Approach

Bridge Name:

River Name:

District Name:

Estimated by:

Date:



COST ESTIMATE: Summary of Estimated Cost

Bridge Number: Bridge Name:

Span in meters: River:

Walkway width: District:

Type of Bridge: Region:

Mode of Execution: Community Approach

Bridge CostDescription Cost (NRs) %

100110

Materials and Road TransportationWire Ropes (Cables)

120 Steel Parts130 Steel Deck140 G.I.Wire150 Cement160 Paints170 Tools180 Road Transportation

Sub-total of Materials and Road Transportation200 Labour210 Transportation from Road Head to Site220 Local Materials Collection (skilled/unskilled labour)230 Construction Works (skilled/unskilled labour)

Sub-total of LabourTotal actual Bridge Cost (Sub-total of Material+Sub-total of Labour)

Contribution

Kind of ContributionLocal Contribution, NRs. Outside Contribution, NRs.

TotalNRs

D D C VD C/M unicipality

LocalInstitution

Individ uals

UsersCometee

Wire Ropes (Cables)Steel PartsSteel DeckG.I.WireCementToolsPaintsCashUnpaid LabourTotal Contribution

Breakdown of the Contribution %Local Contribution, NRs.Outside Contribution, NRs.

Total

Cost Per Meter Span, NRs.

Form No. 3: Quantity and Cost Estimate for Community Approach 1


COST ESTIMATE: Summary of Actual Cost*





Mode of Execution: Community Approach

Bridge CostDescription Cost NRs. %

100 Materials and Road Transportation110 Wire Ropes (Cables)120 Steel Parts130 Steel Deck140 G.I.Wire150 Cement160 Paints170 Tools180 Road Transportation

Sub-total of Materials and Road Transportation200 Labour210 Transportation from Road Head to Site220 Local Materials Collection (skilled/unskilled labour)230 Construction Works (skilled/unskilled labour)

Sub-total of LabourTotal actual Bridge Cost (Sub-total of Material+Sub-total of Labour)

Contribution

Kind of ContributionLocal Contribution, NRs. Outside Contribution, NRs.

TotalNRs.

D D C VDC/M unicipality

LocalInstitution

Individ uals

UsersCometee

Wire Ropes (Cables)Steel PartsSteel DeckG.I.WireCementToolsPaintsCashUnpaid LabourTotal Contribution

Breakdown of the Contribution %Local Contribution, NRs.Outside Contribution, NRs.

Total NRs.

Cost Per Meter Span, NRs.

*Note: This Form to be filled only after completion of the bridge to calculate the actual Bridge Cost



COST ESTIMATE : Abstract of Cost

Description Unit Quantity Rate Cost

100 Materials & Transportation

110 Wire Ropes1 0 13 mm m

0 26 mm m

0 32 mm m

Total 110 W ire Ropes

120 Steel Parts

121 Fabrication2 Steel Parts kg

Reinforcement steel kS122 Supply of Thimbles3 0 13 mm pc

0 26 mm pc

0 32 mm pc

123 Supply of Bulldog GripsJ 0 13 mm pc

0 26 mm pc

0 32 mm pc

124 Miscellaneous Supply2 Bolts, Nuts and Washers kg

Binding Wire

PE Pipes, dia 63mm m125 Rust Prevention2 Hot Dip Galvanization kg

Total 120 Steel Parts


130 Steel Deck

131 Fabrication4 Steel Deck kg132 Rust Prevention4 Hot Dip Galvanization kg

Total 130 Steel Deck


140 G .L W ire 5 141 G.I. Wire kg

Total 140 G .I. W ire


150 Cement5 151 Cement bags

Total 150 Cement


160 Paints5

161 Red Oxide Zinc Chromate ltr

162 Polyurethane Enamel ltr

Total 160 Paints



COST ESTIMATE : Abstract of Cost (Page 2)


170 Tools 171 Tools set 1

Total 170 Tools


180 Road Transportation6 181 Materials & Wire Ropes kg

Total 180 Road Transportation


200 Transportation from road head to site7

210 Transportation 211 Porter (unskilled labour)* mdfrom roadhead to site 212 By Mule kg

Total 210 Transportation from road head to site


220 Local Material Collection 221 Skilled Labour* md

222 Unskilled Labour* md

Total 220 Local M aterial Collection


230 Construction Works 231 Skilled Labour* md

232 Unskilled Labour* md

Total 230 Construction W orks

1 Refer to Sheet Quantity Calculation "110 Wire Rope" (Page 5)2 Refer to Sheet Quantity Calculation "120 Steel Parts" (Page 5)3 Refer to Respective "Steel Drawings"4 Refer to Sheet Quantity Calculation "130 Steel Deck" (Page 5)5 Refer to Sheet "List of Construction Materials" (Page 7)6 Refer to Sheet "Transportation Weight" (Page 8)7 Refer to Sheet "Quantity of Works and Labour" (Page 9)* Apply District rates.



COST ESTIMATE:________________ Quantity Calculation

110 Wire Ropes (Cables)

Type No.Single

Length(m)

0(mm)

Length per Type per 0

0 13mm 0 26mm 0 32mm

Walkway Cable

Handrail Cable

Fixation Cable

Total length per 0 in meter

Total length, m

Weight of cable per m length 0.67 2.57 3.9Total weight of cable per 0 in kg

Total weight, kgNote: Above Quantities are derived from Form No. 2: Cable Design Form

120 SteelpartsDRAWINGS

Uni

ts

StructuralSteel

(kg)

Reinforcement Steel

(kg)

BindingWire

(kg)

Nuts, Bolts & Washers

(kg)

Steel to be galvanized

(kg)

TransportWeight

(kg)No. Name

Cross Beam _ _Saddles and Reinforcement for RCC Dead-man & Gravity Soil AnchorSaddle and Reinforcement for Drum Rock Anchor

Saddles and Reinforcement for RCC Anchor in fractured Rock

Total Steel Parts

130 Steel DecksDRAWINGS

Units Structural Steel(kg)


(kg)

T ransport Weight

(kg)No. Name

08A Standard Panel

09A Half Panel

10A Special PanelTotal

Note: Above Units and Quantities are derived from the respective Steel Drawings.



COST ESTIMATE: Quantity Calculation (Page 2)230 Construction

Location

Foundation ExcavationBackfilling

3mSoil

3m

SoftRock

m3

HardRock

3m

RCC Deadman & Gravity Soil Anchor Block

Right Bank

Left Bank

RCC Drum Rock Anchorage

Right Bank

Left Bank

Other Structures

TotalNote: Above Quantities are to be calculated from General Arrangement Drawing.

Location

Concrete Works Cement Stone Masonry Works Dry Stone Masonry Works

CementPlaster

1:42m

1:3:6

3111

1:2:4

m3

CoursedChisel

Dressed1:4m3

CoursedHammerDressed

1:63m


dry3m

BrokenStone

3m

RCC Deadman & Gravity Soil Anchor Block

Right Bank

Left Bank

RCC Drum Rock Anchorage

Right Bank

Left BankRCC Deadman in Soft or Fractured Hard Rock

Right Bank

Left Bank

CSM Tower & RCC Core

Right Bank

Left BankOther Structures

TotalNote: Above Quantities are derived from respective Construction Drawings.



COST ESTIMATE: List of Construction Materials140/1 Fence Knitting

Item Bridge span (m)

Requirement per meter span

(kg)Total Weight

(kg)12 SWGG.I. Wire 3.9

140/2 Gabion Wires (for maintenance only, if rquired)

Box Size (m) Volume

(mJ)

Mesh Wire 10 SWG Selvege wire 7 SWG Binding Wire 12 SWGRequire

ment per nV

Weight(kg)

Requirement

per rrFWeight

(kg)

Requirement

per rrFWeight

(kg)2.0/1.0/1.0 12.08 1.58 0.483.0/1.0/1.0 11.70 1.37 0.432.0/1.0/0.3 22.33 3.75 1.083.0/1.0/0.3 21.94 3.33 1.00

TotalTotal Weight of Gabion Wire (kg)

160 Paints (For maintenance only)

Item

PaintingArea

(m2)

Requirement

per m2(Itr.)

Quantity

(Itr.)

Weight per Itr.

(kg)

Weight

(kg)Red Oxide Zinc Chromate 0.25 1.8Polyurethane Enamel 0.20 1.8

230 Construction

Item Uni

ts

TotalQuantity

ofWork

Requirementper

Unit

Cement

(Bags)

Sand

(M3)

Gravel

(M3)

ChiselDressed

Stone(M3)

HammerDressed

Stone(M3)

BrokenStone(M3)

Construction of Gabions4.4

Concrete 1:3:6 mJ 0.470.896.4

Concrete 1:2:4 m3 0.450.85

Grouting of Holes nos 0.040.01

Coursed Chisel Stone Masonry 1:4

2.28m3 0.32

1.1

Coursed Hammer Stone Masonry 1:6

1.5m3 0.32

1.1Dry Coursed Hammer Stone Masonry m3 1.1

Dry Broken Stone Masonry m3 1.11:4 Cement Plaster 20 3 0.18mm thick m 0.024

Total Quantity of Construction Materials



COST ESTIMATE: Transportation Weight

180 Transportation

S.N. MaterialsQuantity

kgRemarks

Refer to:1 Steel Parts Refer to Sheet Quantity Calculation "120

Steel Parts" (page 5)

2 Steel DeckRefer to Sheet "130 Steel Deck" (page5)

3 Cement

4 Fencing G.I. Wire

Gabion Wires Refer to Sheet "List of ConstructionD

Materials" (Page 7)

6 Paints

7 Tools 80.0

Sub-Total Materials

8 Wire Ropes (Cables)Refer to Sheet Quantity Calculation "110 Wire Ropes" (Page 5)

Total of Materials & Wire Ropes



COST ESTIMATE: Quantity of Works and Labour

S.N. Description Quantity UnitLabour input

per unit MandaysRemarks

skilled unskilled skilled | unskilledA. Local Material Collection1 Chisel Dressed Stone m3 10.00 3.002 Hammer Dressed Stone in' 5.00 3.003 Broken Stone m3 - 5.004 Gravel m3 - 7.005 Sand nr' - 3.00

A. Total Local Material CollectionB. Construction Works6 Foundation Excavation in Soil m3 - 1.707 Foundation Excavation in Soft rock m3 - 2.508 Foundation Excavation in Hard Rock m3 - 12.009 Hard Rock hole drilling & grouting nos 0.10 2.0010 Coursed Dry stone Masonry m3 1.00 1.0011 Cement Stone Masonry (1:4) m3 1.50 3.0012 Cement Stone Masonry (1:6) m3 1.50 3.0013 Concrete RCC 1:2:4 3m 1.00 4.0014 Concrete RCC 1:3:6 m3 1.00 4.0015 Cement Plaster (1:4) m2 0.22 0.2216 Gabion Works m3 0.35 0.4017 Cable Pulling* m - 0.3018 Walkway Erection** m - 0.6019 Fence Knitting** m - 0.3020 Dismantling of masonry structures 3m - 2.2021 Dismantling of walkway m - 0.2822 Painting m2 0.18 0.33

B. Total Construction Works* Quantity is equal to total length of cables of all 0 . Refer to Sheet Quantity Calculation "110 Wire Ropes" (Page 5) ** Quantities are equal to bridge span

S.N. Description Totalweight

Unit Porterdays

Labour Input per Unit

mdMandaysPorter

Remarks

a b c d e = axcxdC. Portering16 Transport of Materials tons 25.0018 Transport of Wire Rope (Cable) tons 65.00

C. Total Portering

Summery (A+B+C) TotalMandays

RateRs.

Total Cost Rs.

Skilled LabourUnskilled LabourPorter (Unskilled Labour)

Total Labour Cost



COST ESTIMATE: List of Tools

S.N. Description Unit Quantity Remarks

A. Tools for Construction1 Shovel pc 22 Pick axe pc 23 Crowbar (1 'A”) pc 24 Large hammer (5 kg) pc 15 Large hammer (3 kg) pc 26 Stone dressing hammer (1 kg) pc 127 Long chisel (2’ x 1") pc 28 Stone breaking chisel pc 29 Stone dressing chisel pc 1510 Square bottom pc 211 Plum bob pc 212 Measuring tape (5 m) pc 113 Seiving wire mesh (1.5 m) (3 mm") pc 114 Level pipe (5 m) pc 115 Mason thread rol 1

B. Tools for Bridge Erection1 Pliers pc 22 Slide wrench 12" pc 13 Ring wrench size 18/19 mm pc 14 Ring wrench size 20/22 mm pc 15 Ring wrench size 30/32 mm pc 16 Masonry trowel pc 47 Headpan pc 68 3/4m suspender bending pipe pc 29 Suspender bending die pc 110 Plastic sheet (15 m) pc 111 Hacksaw Frame pc 112 Hacksaw blade pc 1013 Kerosene tine pc 414 Inexpensive bag pc 115 Tool Box pc 116 Claw Hammer pc 117 Nails (3") ____kg____ 1



COST ESTIMATE: Rate Analysis

Description Unit UnitQuantity Rate Unit Cost

120 Fabrication of Steel Parts and Steel Deck121 Fabrication of Steel Parts per kg

Materials Structural Steel* kg 1.11Labour Skilled md 0.11

Unskilled md 0.11Sub-total

Tools and Plants (7%) Sub-total

Overhead and VAT Total cost per kg

122 Fabrication of Reinforcement Steel per kgMaterials Reinforcement Steel* kg 1.11Labour Skilled md 0.03



130 Fabrication of Steel Deck per kgMaterials Structural Steel* kg 1.11Labour Skilled md 0.11


Tools and Plants (7%) Sub-total


180 Road Transportation181 Transportation of Material, Equipment and Wire Ropes per tone

Transportation by Truck Dist, km Weight, t Rate Unit CostFrom: to :

Metalled Road 1.00Non-Metalled Road 1.00

Transportation by Tractor (only where aplicable)From: to: Earthen Road 1000.00

Sub-totalOverhead and VAT Total cost per tone

Total cost per kg



COST ESTIMATE: Official Rate

Fiscal Year:

Description Unit Rate

Wire Ropes 0 13 mm m

0 26 mm m

0 32 mm m

Supply of Steel Parts Structural Steel kg

Reinforcement Steel kg

Thimbles 0 13 mm pc

0 26 mm pc

0 32 mm pc

Bulldog Grips 0 13 mm pc

0 26 mm pc

0 32 mm pc

Miscellaneous Bolts, Nuts and Washers kg

Binding Wire kg

Rust Prevention

Workshop Labour Rate

Hot Dip Galvanization kg

Skilled md

Unskilled md

Transportation Truck Metalled Road txkm

Truck Non-Metalled Road txkm

Construction Fuel ltr

G.I. Wire 7,10,12 SWG kg

Cement bag

Painting Works Red Oxide Zinc Chromate ltr

Polyurethane Enamel ltr

Miscellaneous Tools 1 set

Note: The above rates are including VAT



Form No. 4

His Majesty’s Government o f Nepal Ministry o f Local Development Department o f Local Infrastructure Development and Agricultural Roads

: Quantity & Cost Estimate for Public Tender & Contracting

SDC/Helvetas Nepal Trail Bridge Sub-Sector Project

Short Span Trail Bridge Standard Suspended Type V olu m e II

Form No. 4

Quantity & Cost Estimate

for Public Tender & Contracting

Bridge Name:

River Name:

District Name:

Estimated by:

Date:



C O S T E S T I M A T E : Summary of Cost





Mode of Execution: Contracting

DESCRIPTION Cost NRs. %


200 Steel Parts

300 Transportation

400 Construction

Total

Cost per meter span

Total Cost in Words:

NAME SIGNATURE DATE

Estimated by

Checked by

Approved by

Form No. 4: Quantity and Cost Estimate for Public Tender & Contracting 1


COST ESTIMATE : Abstract of Cost

100 MATERIALS

Description POS Unit Quantity Rate Cost110 Wire Ropes* 111 0 13 mm m

112 0 26 mm m113 0 32 mm m

Subtotal 1105% ContingenciesTotal 100 Materials

200 STEEL PARTS

Description POS Unit Quantity Rate Cost210 Fabrication** 211 Structural steel kg

212 Reinforcement steel kg220 Supply of Thimbles*** 221 0 13 mm pc

222 0 26 mm pc223 0 32 mm pc

230 Supply of Bulldog 231 0 13 mm pcGrips*** 232 0 26 mm pc

233 0 32 mm pc240 Miscellaneous 241 Bolts, Nuts and Washers kg

Supply** 242 Binding Wire kg250 Rust Prevention** 251 Hot Dip Galvanization k L

Subtotal 210-250 (including VAT)5% ContingenciesTotal 200 Steel Parts

300 TRANSPORTATION

Description POS Unit Quantity Rate Cost310 Transportation**** 311

312Materials kgWire Ropes kgSubtotal 3105% ContingenciesTotal 300 Transportation

* Refer to Quantity Calculation SheetM100 Wire Rope” (Page 4)** Refer to Quantity Calculation Sheet ”200 Steel Parts” (Page 4)*** Refer to Respective "Steel Drawings"**** Refer to Quantity Calculation Sheet "300 Transportation weight" (Page 7)



|Cost Estimate Abstract of Cost (page 2)|

400 CONSTRUCTIONDescription POS Unit Quantity Rate Cost410 Foundation

Excavation*411 Soil m3412 Soft Rock m3413 Hard Rock (quarrying) rn414 Backfilling 3m

420 Construction of Gabions*

421 Box Size 2 x 1 x 1.0 m 3m422 Box Size 3 x 1 x 1.0 m m3423 Box Size 2 x 1 x 0.3 m rn424 Box Size 3 x 1 x 0.3 m m3

430 Concrete Works* 431 Plain Mass Concrete 1:3:6 m3432 Reinforced Cement Concrete 1:2:4 m3433 Hole Drilling & Grouting of Holes m

440 Cement StoneMasonry Works*

441 Chisel dressed in 1:4 c/m 3m442 Hammer dressed in 1:6 c/m 3m443 Cement Plaster 1:4, 20 mm thick 2m

450 Dry StoneMasonry Works*

451 Chisel dressed mJ452 Hammer dressed m3453 Broken stones 3m

460 Erection 461 Hoisting of Cables ** 0 13 mm0 26 mm 0 32 mm

mmm

462 Erection of Walkway & Steel Deck*** m463 Fencing*** m

Subtotal 410-4605% ContingenciesTotal400 Construction

500 MISCELLANEOUS WORKS (For Major Maintenance only)

Description POS Unit Quantity Rate Cost510 Concrete and 511 Dismantling of Masonry Structures mJ

Masonry Works 512 Dismantling of Concrete Structures m3

520Pretensioning of Wire Ropes

521 Walkway & Handrail Cables m

530 Walkway 531 Adjusting of Suspenders mAdjustments 532 Replacing of Crossbeams m

533 Adjusting of Crossbeams m534 Dismantling of Walkway m535 Refixing of Walkway & Steel Deck m536 Dismantling of Fencing m537 Replacing of Fencing m

540 Finishing Works 541 Retightening of Bulldog Grips, Nuts, etc. m542 Coaltar Application m543 Repainting of Steel Parts m2

550 Miscellaneous 551552553

Subtotal 510-5505% ContingenciesTotal 500 Miscellaneous

* Refer to Quantity Calculation Sheet ”400 Construction" (Page 5)** Quantities are equal to cable length. Refer to Quantity Calculation Sheet "100 Wire Ropes" (page 4) *** Quantities are equal to bridge span



COST ESTIMATE: Quantity of Calculation


Type No.SingleLength

(m)0

(mm)

Length per Type per 0

0 13mm 0 26mm 0 32mm

Walkway Cable

Handrail Cable

Fixation Cable

Total length in meter

Weight of cable per m length 0.67 2.57 3.9

Total weight of cable per 0 in kg

Total weight

Position of Cost Estimate 111 112 113

Note: Above Quantities are derived from Form No. 2: Cable Design Form

200 Steel PartsDRAWINGS

UnitStructural

Steel(kg)

Reinforcement Steel

(kg)

BindingWire(kg)

Nuts, Bolts & Washers

(kg)


(kg)

T ransport Weight

(kg)No. Name

Cross Beam _ _

Steel Deck _ _Saddle and Reinforcement for RCC Deadman & Gravity Soil Anchor BlockSaddle and Reinforcement for Drum Rock Anchor Block

Total

Position of Cost Estimate 211 212 242 241 251 311

Note: Above Quantities are derived from the respective Steel Drawings.



COST ESTIMATE: Quantity of Calculation400 Construction

Location

Foundation ExcavationBackfilling

3mSoil

3m

SoftRock

3111

HardRock

3m

Deadman & Gravity Soil Anchor Block

Right Bank

Left BankRCC Drum Rock Anchor Block

Right Bank

Left Bank

Other Structures

TotalNote: Above Quantities are to be calculated from General Arrangement Drawing.

Location

Concrete Works Cement Stone Masonry Works Dry Stone Masonry Works

CementPlaster

1:4m2

1:3:6m3

1:2:43m

CoursedChisel

Dressed1:4

3m


1:63m


3m

BrokenStone

m3

Deadman & Gravity Soil Anchor Block

Right Bank

Left BankRCC Drum Rock Anchor Block

Right Bank

Left BankCement Stone Masonry Tower

Right Bank

Left BankOther Structures

Total

Note: Above Quantities are derived from respective Construction Drawings.



COST ESTIMATE: List of Construction Materials

400 Construction

Item Unit

TotalQuantity

ofWork

Requirementper

Unit

Cement

(Bags)

Sand

(m3)

Gravel

(m3)

ChiselDressed

Stone(m3)

HammerDressed

Stone(m3)

BrokenStone(m3)

Construction of Gabions m3

Concrete 1:3:6 3m

4.40.470.89

Concrete 1:2:4 3m

6.40.450.85

Grouting of holes nos 0.040.01

Coursed Chisel dressed Stone Masonry 1:4

3m

2.280.321.1

Coursed Hammer dressed Stone Masonry 1:6

3m

1.50.321.1

Dry Coursed Hammer Stone Masonry

3m 1.1

Dry Broken Stone Masonry 3m 1.1

Cement Plaster 1:4 20 mm thick

3m0.18

0.024Total Quantity of Construction Materials

463 Fence Knitting

ItemBridge span

(m)Requirement

per meter spanTotal Weight

(kg)

12SWGG.I. Wire 3.9

420 Gabion WiresMesh Wire 10 SWG Selvege wire 7 SWG Binding Wire 12 SWC

Box Size (m) Volume Require Weight Require Weight Require Weightment ment ment

(m3) per m3 (kg) per m3 (kg) per m3 (kg)2.0/1.0/1.0 12.08 1.58 0.483.0/1.0/1.0 11.70 1.37 0.432.0/1.0/0.3 22.33 3.75 1.083.0/1.0/0.3 21.94 3.33 1.00

TotalTotal Weight of Gabion Wire (kg)



COST ESTIMATE: Transportation Weight

300 Transportation

S.N. 311 Materials Quantitykg

Remarks

1 Steel PartsRefer to Quantity Calculation Sheet ”200 Steel Parts” (page 4)

2

3

4

Cement

Fencing G.I. Wire

Gabion Wires

Refer to Sheet "List of Construction Materials" (page 6)

Sub-Total Materials

5 312 W ire Ropes (Cables)Refer to Quantity Calculation Sheet "100 Wire Ropes" (page 4)

Total of Materials & W ire Ropes



COST ESTIMATE: Rate Analysis

Description U n itU n it

QuantityRate U n it Cost

210 Fabrication211 Fabrication of Structural Steel per kg

MaterialsLabour

Structural Steel* kg l u

Skilled md 0.11Unskilled md 0.11

Sub-totalTools and Plants (7%)Sub-totalOverhead and VATTotal cost per kg structural steel

212 Fabrication of Reinforcement Steel per kgMaterialsLabour

Reinforcement Steel* kg 1.11Skilled md 0.03Unskilled md 0.04

Sub-totalOverhead and VATTotal cost per kg reinforcement steel

310 Transportation311 Transportation of Material and Equipment per kg

Transportation bv Truck Dist, km Weight, t Rate Unit CostFrom :To :Transportation by Porter

Metalled Road 1.00Non-Metalled Road 1.00(Rate=Daily Wage/38) 1000

Sub-total per 1000 kgOverhead and VATTotal cost per kg transportation of materials and equipment

312 Transportation of W ire Ropes per kgTransportation by TruckFrom :To :Transportation by Porter

Metalled Road 1.00Non-Metalled Road 1.00(Rate=Daily Wage/15) 1000

Sub-total per 1000 kgOverhead and VATTotal cost per kg transportation of wire ropes

410 Foundation Excavation411 Foundation Excavation in Soil per m

Labour Unskilled md 1.7Overhead and VATTotal cost per m3 soil excavation

412 Foundation Excavation in Soft Rock per m3Labour Unskilled md 2.5Overhead and VATTotal cost per nT soft rock excavation

* Material rates should be without VAT



COST ESTIMATE: Rate Analysis (page 2)

DescriptionUnit Unit

QuantityRate Unit Cost

413 Foundation Excavation in Hard Rock per m3Material Fuel ltr 4.00Labour Unskilled md 5.50Sub-totalOverhead and VATTotal Cost per m3 hard rock excavation

414 Backfilling per m3Labour Unskilled md 0.85Overhead and VATTotal Cost per m3 backfilling

420 Construction of Gabions421 Box Size 2.0x1.Oxl.O per m3

Materials Mesh Wire 10 SWG* kg 12.08Selvage Wire 7 SWG* kg 1.58Binding Wire 12 SWG* kg 0.48Rubble 1.10

LabourFabrication of Gabions

Construction of Gabions

Skilled md 0.23Unskilled md 0.10Unskilled md 0.20

Sub-totalOverhead and VATTotal cost per m3

422 Box Size 3 .0xl.0xl.0 per m3Materials Mesh Wire 10 SWG* kg 11.7

Selvage Wire 7 SWG* kg 1.37Binding Wire 12 SWG* kg 0.43Rubble mJ 1.10


Construction o f Gabions



423 Box Size 2.0xl.0x0.3 per m3 (matress)Materials Mesh Wire 10 SWG* kg 22.33

Selvage Wire 7 SWG* kg 3.75Binding Wire 12 SWG* kg 1.08Rubble nT 1.10


Construction o f Gabions









424 Box Size 3.0xl.0x0.3 per m3Materials Mesh Wire 10 SWG* kg 21.94

Selvage Wire 7 SWG* kg 3.33Binding Wire 12 SWG* kg 1.00Rubble nT 1.10


Construction of Gabions


Sub-totalOverhead and VATTotal cost per nT

430 Concrete Works431 Cement Concrete 1:3:6 per m3

Materials Cement* bag 4.40Gravel (5-40 mm) . 3m 0.89Sand „ 3m 0.47

Labour Skilled md 1.00Unskilled md 4.00

Sub-totalOverhead and VATTotal cost per nT concrete 1:3:6

432 Cement Concrete 1:2:4 per m3Materials Cement* bag 6.40

Gravel (5-40 mm) m 0.85Sand m 0.45


Sub-totalOverhead and VATTotal cost per nT 1:2:4

433 Hole D rilling & Grouting of HolesLabour Skilled md 0.05

Unskilled md 2.00Materials Cement* bag 0.04

Sand nT 0.01Sub-totalOverhead and VATTotal cost for one hole drilling & grouting







440 Cement Stone Masonry Works441 Coursed Chisel Dressed Stone Masonry in 1:4 c/m per m3

Materials Cement* bag 2.28Sand nT 0.32Dressed Stones m3 1.10


Sub-totalOverhead and VATTotal cost per m3 coursed chisel dressed stone masonry 1:4

442 Coursed Hammer Dressed Stone M asonry in 1:6 c/m per m3Materials Cement* bag t 1.50

Sand 3m 0.32Dressed Stones 3m 1.10


Sub-totalOverhead and VATTotal cost per m3 coursed hammer dressed stone masonry 1:6

443 Cement Plaster 1:4, 20 mm thick per m2Materials Cement* bags 0.18

Sand 3m 0.02Labour Skilled md 0.22

Unskilled md 0.22Sub-totalOverhead and VATTotal cost per m2 cement plaster 1:4, 20 mm thick

450 Dry Stone Masonry Works451 Coursed Chisel Dressed D ry Stone Masonry per m3

Materials Dressed Stones nT 1.10Labour Skilled md 1.00

Unskilled md 1.00Sub-totalOverhead and VATTotal cost per nT coursed chisel dressed d ry stone masonry

452 Coursed Hammer Dressed D ry Stone M asonry per m3Materials Dressed Stones m3 1.10Labour Skilled md 1.00

Unskilled md 1.00Sub-totalOverhead and VATTotal cost per nT coursed hammer dressed d ry stone masonry


Form No. 4: Quantity and Cost Estimate for Public Tender & Contracting II





453 Packing with Broken (stratified) Stones per m3Materials Stratified Stones m 1.10Labour Skilled md 1.00

Unskilled md 1.00Sub-totalOverhead and VATTotal cost per m3 for packing with broken stones

460 Erection461 Hoisting Cables 0 13 mm per m cable

Labour Unskilled md 0.08Sub-totalOverhead and VATTotal cost per m cable <J) 13 mmHoisting Cables 0 26 mm per m cableLabour Unskilled md 0.32Sub-totalOverhead and VATTotal cost per m cable <|> 26 mmHoisting Cables 0 32 mm per m cableLabour Unskilled md 0.48Sub-totalOverhead and VATTotal cost per m cable <|> 32 mm

462 Erection of the W alkway & Steel Deck per m spanLabour Unskilled md 0.60Sub-totalOverhead and VATTotal cost per m span

463 Fence Knitting per m span (both sides)Materials 12SWG G.I. Wire* kg 3.90Labour Unskilled md 0.30Sub-totalOverhead and VATTotal cost per m span

470 Local Material Collection471 Chisel Dressed Stones per m3

LabourCollection and Dressing Skilled md 8.00

Unskilled md 3.00Cost per mJ for collecting and chisel dressing stones

472 Hammer Dressed Stone per m3Labour

Collection and Dressing Skilled md 4.00Unskilled md 3.00

Cost per mJ for collecting and hammer dressing stones







473 Broken Stones per m3Labour

Collection and breaking Unskilled md 3.00Cost per m3 for collecting and breaking stones

474 Sand pe m3Labour Collection of sand Unskilled md 1.50

Additional Haulage Distance Unskilled md 0.01Cost per mJ for collecting and hauling sand

475 Gravel (Broken)Labour Breaking of gravel Unskilled md 7.00Cost per mJ for breaking gravel 1

500 Major Maintenance510 Concrete and Masonry W orks511 Dismantling of M asonry Structures per m3

Labour Unskilled md 2.20Overhead and VATTotal cost per m3 for dismanteling of masonry structures

512 Dismantling of Concrete Structures per m3Material Fuel ltr 4.00Labour Unskilled md 26.00Sub-totalOverhead and VATTotal cost per m3 for dismanteling of concrete structures

520 Pretensioning/Hoisting W orks

521 Pretensioning/Hoistingof of Cables per m cable

Cable 0 13 mmLabour Pretensioning Skilled md 0.01

Unskilled md 0.01Sub-totalOverhead and VATTotal cost per m pretensioning/hoisting cables 0 13 mmCable 0 26-40mmLabour Loosening Skilled md 0.01

Unskilled md 0.02Labour Pretensioning Skilled md 0.01

Unskilled md 0.05Sub-totalOverhead and VATTotal cost per m pretensioning/hoisting cables 0 26 - 40 mm






530 Walkway Adjustment531 Adjusting of Suspenders per m span


Sub-totalOverhead and VATTotal cost per m span

532 Replacing of Cross Beams per m spanLabour Skilled md 0.67

Unskilled md 1.42Sub-totalOverhead and VATTotal cost per m span

533 Adjusting of Crossbeams per m spanLabour Skilled md 0.22


534 Dismantling of W alkway per m spanLabour Unskilled md 0.28Sub-totalOverhead and VATTotal cost per m span

535 Refixing of W alkway per m spanLabour Skilled md 0.27


536 Dismantling of Fencing per m spanLabour Skilled md 0.01


537 Replacing of New Fencing per m spanMaterial 12 SWG G.I. Wire* kg 3.90Labour Skilled md 0.02


* Material Rates should be without VAT






540 Finishing Works541 Retightening of Bulldog grips, Nuts, etc. per m span

Labour Unskilled md 0.10Total cost per m span __________

542 Coaltar Application per m spanMaterial Coaltar ltr 0.20

Kerosene ltr 0.20Labour Skilled md 0.02


543 Repainting of Steel Parts per m2Labour Preparation of surface Skilled md 0.01

Unskilled md 0.16Material 1 Base Coat Labour

Red Oxide Zinc Chromate* ltr 0.25Skilled md 0.08Unskilled md 0.07

Material Finishing Coat Labour

Polyurethane Enamel* ltr 0.20Skilled md 0.09Unskilled md 0.10

Sub-totalOverhead and VATTotal cost per m2 steel surface




COST ESTIMATE: Official Rate

Fiscal Year:

Description Unit Rate

110 W ire Ropes 211 0 13 mm m

212 0 26 mm m

213 0 32 mm m

210 Supply of Steel Parts 211 Structural Steel kg

212 Reinforcement Steel kg

220 Thimbles 221 0 13 mm pc

222 0 26 mm pc

223 0 32 mm pc

230 Bulldog G rips 231 0 13 mm pc

232 0 26 mm pc

233 0 32 mm pc

240 Miscellaneous 241 Bolts, Nuts and Washers kg

242 Binding Wire kg

250 Rust Prevention 251 Hot Dip Galvanization kg

Workshop Labour Rate Skilled md

Unskilled md

310 Transportation 311/312 Truck Metalled Road txkm

311/312 Truck Non-Metalled Road txkm

400 Construction 520/530 Fuel ltr

440 G.I. Wire 7,10,12 SWG kg550/560 Cement bag

540 Painting W orks 541 Red Oxide Zinc Chromate ltr

542 Polyurethane Enamel ltr

Note: The above rates are including VAT


Date post:	15-Mar-2023
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