Analysis and Design of mosque

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Anal ysis and Design of mosque I ndustrial Tr ainin g report 2013

Department of Civil Engin eeri ng KM EA Engi neeri ng college1

CHAPTER 1

INTRODUCTION

Reinforced concrete occupies a leading position modern construction along with prestressed concrete and steel construction. Proper construction depends upon through

knowledge of action of structure and on the knowledge of characteristics and limitations of

materials that are used in the construction. The care with work is executed in the site is also

important in construction industry.

Industrial training always helps to have practical exposure to the different methods of

analysis and design in reinforced concrete. it helps to understand theory along with the use of

structural engineering software. The entire spectrum of structural engineering field includes

analysis, design, detailing , and drafting , also site related problems are under stood.

The issue related to soil engineering and the study of soil investigation reports,

interpretation of data and foundation design is also understood. Understanding different

software tools in structural engineering, its limitations. The major project assigned during

training was a multi storied mosque building at Malappuram. Site visits are also conducted

during training.


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CHAPTER 2

ABOUT THE PROJECT

Industrial training was on modeling, analysis, designing and detailing of amultistoried mosque building. The proposed site is at Malappuram. Here basement floor,

ground floor, first floor, second floor are intended for prayer. The height of building is about

16.7m.

The structural system consists of RCC conventional beam slab arrangement. Kerala is

considered in seismic zone III as per IS 1893- 2002. Analysis was carried out using a very

sophisticated software tool STAAD PRO v8i. Detailed analysis and design was carried out

based on architectural drawing available and the results are summarized in the report.


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CHAPTER 3

DESCRIPTION OF STAAD Pro

3.1 GENERAL

STAAD Pro is comprehensive structural engineering software that addresses allaspects of structural engineering – model development, analysis, design, verification andvisualization. This uses finite element method for analysis. One can building model, verify itgraphically, perform analysis and design, review the results, and create report all within thesame graphical base environment.

3.2 THE MODELLING MODE

There are two methods for building a model and assigning the structure data usingSTAAD Pro.

a. Using the command file b. Using the graphical model generation mode or graphical user interface (GUI) as it is

usually referred to.

The command file is a text file, which contains the data for the structure being

modeled. The file consists of simple English language like commands, using a format nativeto STAAD Pro. This command file may be created directly using the editor built into the

program, or for that matter, any editor which saves data in text form, such as Notepad orWordPad available in Microsoft Windows.

The graphical method or creation involves utilizing the Modeling mode of theSTAAD Pro graphical environment to draw the model using the graphical tools, andassigning data such as properties, material constants, loads, etc., using the various menusand dialog boxes of that mode.

If the second method is adopted (using the UGI), the command file gets automaticallycreated behind the scenes


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Fig 3.1 THE PLAN OF THE STRUCTURE PRODUCED USING STAAD Pro


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Fig 3.2 ISOMETRIC VIEW OF THE STRUCTURE FROM STAAD Pro


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Fig 3.3 THE MODEL PROUCED USING STAAD Pro


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The graphical model generation mode and the command file are seamlesslyintegrated. So, at any time, the graphical model generation mode can be temporarily exitedand access the commend file. When changes are made to the command file and saved, theGUI immediately reflects the changes made to the structure through the command file. The

frame of the building after modeling is shown in Fig.

3.3 PERFORMING ANALYSIS AND DESIGN

STAAD offers two analysis engines – the STAAD engine for general purposeStructure Analysis and Design and the STARDYNE engine for advanced analysis options.The modeling mode of the STAAD environment is used to prepare the structural input data.After the input is prepared, the analysis engine can be chosen depending upon the nature ofthe analysis required. Depending on the type of analysis option selected, different types ofoutput files are generated during the analysis process.

The STAAD analysis engine performs analysis and design simultaneously. But, tocarry out the design, the design parameters too must be specified along with geometry,

properties, etc. before performing the analysis. The design code to be followed for design can be selected before performing the analysis/design.

3.4 POST PROCESSING MODE

The Post Processing Mode of STAAD offers facilitates for on – screen visualizationand verification of the analysis and design results. Displacements, forces, stresses, etc. can beviewed – both graphically and numerically in this mode. Most of the menu items in the post

processing mode are the same as in the modeling mode. STAAD also enables preparation ofcomprehensive reports that include numerical and graphical result. Printable reports may begenerated in two ways. Through the STAAD output file and through the report setup facilityfrom the Post Processing Mode. The STAAD output file is a text file containing results,diagrams etc. It is a more versatile facility than the output file in terms of user – level control .


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CHAPTER 4

GENERAL PRINCIPLE OF DESIGN

4.1 OBJECTIVES OF STRUCTURAL DESIGN

The design of the structure must satisfy the following requirements

Stability : To prevent the overturning , sliding or buckling of the structures, or any

part of it under action of loads.

Strength : to resisit safely the stresses induced by the loads in the various structural

members

Serviceability : To ensure satisfactory performance under service load conditionswhich implies providing adequate stiffness and reinforcement to contain deflections,

cracks widths and vibrations with in adequate limits and also providing

impermeability and durability.

There are other considerations that a sensible designer ought to bear in mind , viz..,

Economy and aesthetics. One can always design a massive structure , which has more

than adequate stability, strength and serviceability ,but the ensuing cost of the

structure may be exorbitant and the end product far from aesthetics.

4.2 SOIL INVESTIGATION REPORT:

The building site is located at Malappuram. The proposed site consists of top layer of

very loose sand followed by soft to medium silty clay followed by Lateritic sandy clay with

pebbles followed by silty clay/clayey sand followed by very dense sand. From the site

observation, the soil condition of the site was medium soil of safe bearing capacity

200 kN/m 2. Hence it is recommended foundation for this is isolated sloped footing


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CHAPTER 5

STRUCTURAL ANALYSIS USING STAAD Pro

5.1 GENERAL

Analysis is done using STAAD Pro, as it is widely used for structural analysis anddesign from Design Engineers International. While doing analysis material and geometric

properties are assumed. Loading considered in analysis are dead load, live load, seismic loadand wind load. Finally on running program output values are obtained, M15 grade and Fe415steel is used.

5.2 LOADS CONSIDERED IN THE DESIGN

Structural analysis of the structure need to be preceded with the calculation of loadimposed on the structure. Various loads taken into account for the analysis of the structureinclude live load, dead load, wind load and seismic load. As the area falls under zone III ofthe earthquake classification as per Indian Standards, seismic design of the structure ismandatory. IS 875 Part I deals with dead loads, IS 875 Part II with imposed load, IS 875 PartIII with wind load and IS 1893 Part I with seismic load. The loading standard not onlyensures structure safety of building but also eliminate wastage caused by assuming

unnecessary heavy loadings without proper assessment.

5.2.1 DEAD LOAD

Dead loads are loads that are constant in magnitude and fixed in position throughout a particular span. It includes self – weight of all structural components in that span. Dead loadshave been determined after assuming both material as well as geometric properties of allelements used in the building. Unit weight of RCC and brickwork are adopted as 25 KN/mand 20KN/m respectively.

5.2.2 IMPOSED LOAD

The load is assumed to be produced due to the intended use or occupancy of a building, load due to impact and vibration, and dust load, but excluding wind, seismic, andother loads due to temperature changes, creep, shrinkage, differential settlement etc.

Imposed loads assumed for an assembly building shall be load that will be

produced by the intended used or occupancy, but shall not be less than the equivalent


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minimum loads specified by table-1 IS 875 Part II. Live loads of all floors are assumed as4 kN/m 2.

5.2.3 WIND LOAD

Wind may be defined as air in motion relative to the surface of the earth. Buildingsshould always be designed with due attention for the effect of wind. In general, wind speed inthe atmospheric boundary layer increases with height from zero at the ground level tomaximum at a height called the gradient height. Slight change in the wind direction at thisheight is neglected in the code. Basic wind speeds (Vb) for different wind zone of India areobtained from IS 875 Part III (Appendix A). From this basic wind speed, the design windspeed (in m/sec) for each storey at height „z‟ is called from

Vz = V b x k 1 x k 2 x k 3

Where, k 1, k 2 ,k 3 = coefficients from IS 875 Part III,

5.2.4 SEISMIC LOAD

For the purpose of determining seismic forces, the country is classified in to fourseismic zones. Location of the structure falls under area of zone III. The seismic effect, i.e.,the intensity and duration of the vibrations, depend on the magnitude of the earthquake, depth

of focus, distance from epicenter, soil strata which hold the structure etc.

As per IS 1893 Part I, clause 6.1.2, the response of a structure to ground vibration is afunction of the nature of foundation soil, materials, from size and mode of construction ofstructures and duration and characteristics of ground motion. This standard specifies designforces for structures standing on rocks or soil which do not settle liquefy or slide due to lossof strength from ground vibration. Also the following assumptions are made for theearthquake resistant design of structures.

Earthquake causes impulsive ground motions, which are complex and irregular in

character, changing in period and amplitude each lasting for a small duration. Thereforeresonance of the type as visualized under steady state sinusoidal excitations will not occuras it would need time to build up such amplitudes.

Earthquake is not likely to occur simultaneously with wind or maximum flood ormaximum sea waves.

The value of elastic modulus of materials, wherever required, may be taken as for staticanalysis unless a more definite value is available for use in such condition.

The seismic weight of each floor for the analysis is to be taken as its full dead load plus appropriate amount of imposed loads. While computing the seismic weight of each floor,


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the weight of columns and walls in any storey shall be equally distributed to the floors aboveand below. Percentage of imposed load as taken from table 8 of IS 1893 – 2002 is 50%.

5.3 LOAD CALCULATIONS

5.3.1 SEISMIC LOAD

Design horizontal seismic coefficient, Ah = ZISa/2Rg(From IS1893 (Part I) – 2002 clause 6.4.2)Where,Z = Zone factor = 0.16 (from IS1893 (Part I) – 2002 clause 6.4.2 Table 2)I = Importance factor = 1.5 (from IS1893 (Part I) – 2002 clause 6.4.2 Table 6)R=response reduction factor (from IS1893 (Part I) – 2002 clause 6.4.2 Table 7)

SS = Rock and soil silt factor = 2 (for medium soil)

5.3.2 DEAD LOAD

Floor load

Dead load of slab = 0.12 x 25 = 3kN/m 2

Finishes = 1kN/m 2

Total = 4 kN/m 2

Brick wall load4.2 m high = 0.23 x 4.2 x 20 = 19.32 kN/m

5.3.3 LIVE LOAD

Live load on floor = 4 kN/m 2

Live load on Roof = 4 kN/m2

5.3.4 WIND LOAD

Basic wind speed in Trivandrum = v b = 39 m/s (from IS 875, Part III)

Design wind speed = v z = v b x k 1 x k 2 x k 3

k 1 = Probability factor

k 2 = Terrain and size factor


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k 3 = Topography factor

Design wind pressure P z = 0.6 x v z2

TABLE 5.1 WIND LOAD CALCULATIONS

FLOOR HEIGHT m

Vb

m/s K

1 k

2 k

3

VZ (m/s) P

Z(kN/m

2)

GROUND

FLOOR 3.9 39 1 1.05 1 40.95 1.00614515

FIRST FLOOR 8.7 39 1 1.05 1 40.95 1.00614515

SECOND FLOOR 12.9 39 1 1.0732 1 41.8548 1.05109457

ROOF 17.1 39 1 1.1026 1 43.0014 1.10947224


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5.4 LOAD COMBINATIONS

The various load combinations that are adopted in the analysis are shown intable

TABLE 5.2 LOAD COMBINATIONS

DL+LL 1.5 1.5

DL+WLX

1.5 1.5

DL+WLZ 1.5 1.5

DL+ELX

1.5 1.5

DL+ELZ 1.5 1.5

DL+WLX

0.9 1.5

DL+WLZ 0.9 1.5

DL+ELX

0.9 1.5

DL+ELZ 0.9 1.5

DL+LL+WLX

1.2 1.2 1.2

DL+LL+WLZ 1.2 1.2 1.2

DL+LL+ELX

1.2 1.2 1.2

DL+LL+ELZ 1.2 1.2 1.2


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Fig 5.1 WIND LOAD IN X DIRECTION.

Fig 5.2 WIND LOAD IN Z DIRECTION


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Fig 5.3 SEISMIC LOAD in X-Direction

Fig 5.4 SEISMIC LOAD in Z-Direction


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Fig 5.5 BENDING MOMENT DIAGRAM OF GROUND FLOOR

Fig 5.6 SHEAR FORCE DIAGRAM OF GROUND FLOOR


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CHAPTER 6

DESIGN OF RCC BUILDING

6.1 DESIGN OF FOOTING

6.1.1 GENERAL

Footing is the type of foundation in which base of wall or column is sufficiently

enlarged to act as an individual support widened base not only provides stability but is

useful in distributing load on sufficient area of the soil. Foundation is the bottom most

important component of a structure which generally lies below the ground level. The

foundation provided for a RCC beam is called a column footing

The column footing is distributing the load over a large area so that the

intensity of pressure on soil, and not exceeded safe bearing capacity soil and settlement of

structure is kept permissible limit.

Types of footings:

Isolated footing Combined footing

Pile foundation Continuous footing for walls Spread footing Raft or Mat foundation Strap footing Cantilever footing

6.1.2 DESIGN OF ISOLATED SLOPED FOOTING

Design for:

Soil pressure, q = 200 kN/m 2

M20, ie., f ck = 20 N/mm 2

Fe415, ie., f y = 415 N/mm2

Size of column = 600mm x 300mm

Design constants

For M 20 – Fe 415 combination, we have:


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= 0.479 and R u = 2.761

Size of footing

W= 2150 kN

Self weight of footing shall be assumed as 10% of the column load

Total load, P = 2150+215 = 2365 kN

Area of footing needed, A F = = = 11.825m2

Provide a square footing of size 3.5 m x 3.5 m

Net soil pressure acting upward, q 0 =

= 175.5 kN/m 2

Design of footing

Maximum bending moment occurs at the face of column

M = q 0 (B-b w)2 = 784 kNm

Effective depth at the column face, d = = 972 mmLet the effective depth at the column face be„d‟ and that at the edge be 0.2d

D = d + 0.2d = 1165

Using an effective cover of 60mm

Available depth of footing, d = 1165 – 60 = 1105 mm

Effective depth of footing at the edge shall be 0.2d = 195 mm

The overall thickness at the edge shall be 195+60 = 255 mm

Check for shear

(a) For one way shearV = q 0 B [ = 304 kNVu = 1.5V = 456 kN

Effective depth d‟ at that location = 195 + ( ) ]= 476 mm


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Top width of section = 300 + = 2510 mmFor under reinforced section, adopt So that x u = 0.4d‟ = 190 mm

Width b n at N.A = 2510 + = 2890 mmTherefore Ʈ v = V u/bnd‟ = 0.274 N/mm

2

Assume P= 0.3% for an under reinforced section Ʈ c = 0.384 N/mm 2

(From IS 456 table 19)

Ʈv < Ʈ c Hence safe

(b) For two way shear

Perimeter ABCD = 2 [(a+d)+(b+d)] = 2[600+1105+300+1105] = 6220mm

Area of ABCD, A = (a+d)x(b+d) = (600+1105)x(300+1105) = 2.4 m 2

Punching shear, V u = q o [B2-A] = 175.5 [3.5 2-2.4 2] = 1728.67 kN

Ʈv = 1.5 = 1.5x1728.67x103/6220x1105 = 0.377 N/mm 2

Ʈc = 0.25 = 1.118 N/mm 2Ʈv < Ʈ c Hence safe

Steel reinforcement

Ast = [ – ] b1d = 2296 mm 2 Hence provide 12 numbers of 16mm diameter rods uniformly spaced in the width3.5m in each direction


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6.2 DESIGN OF COLUMN

6.2.1 GENERAL

Column forms a very important component of structure. Column support beam which is in turn support walls and slabs. It should be realized that the failure of a column results in a collapse of the structure. The column is defined as the compression member, the effective length of which

exceeds three times the least lateral dimension.

Column may be cost to any of the following shape – square, circular, hexagonal,

octagonal.

As per IS 456:2000 a reinforced concrete column shall have longitudinal steel

reinforcement shall not be less than 0.80 percentage more than 6 percentage of cross

sectional area of the column required to transmit the all loading.

Longitudinal reinforcement is provided to resist compressive load along with the

concrete.

The design of column therefore receive importance The object of stipulating minimum percentage of steel is to make provision to

prevent buckling of the column due to any accidental essentially of load on it.

The object of stipulating maximum percentage of steel is to provide reinforcement

with such a limit to avoid congestion of reinforcement which would make it very

difficult to place the concrete and consolidate it.

6.2.2DESIGN OF RECTANGULAR COLUMN

Material constants

Use M 20 grade concrete and HYSD steel bars of grade Fe 415 .

For M 20 Concrete, f ck = 20 N/mm2

For Fe 415 Steel, f y = 415 N/mm2

Preliminary dimensioning

Depth of column, D = 600 mm


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Breadth of column, B = 300 mm

Support condition is one end fixed and other hinged

Unsupported length, = 4.3 m

As per IS 456:2000, Table 28

Multiplication factor for effective length =0.65

Type of column

Longitudinal reinforcement

(0.8% is minimum steel area of column as per IS 456:2000)

Assume of steel

=

= 0.1

Uniaxi al moment capacity of section about xx-axis

Assume,

Diameter of bar = 20 mm

Clear cover = 40 mm

d‟ =clear cover +half the bar diameter

= 40+10

=50

Taken = 0.1


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Results from STAAD

Factored axial load , P u = 2262 kN

Factored moment in x-direction, M ux = 61.74 kNm

Factored moment in y-direction, M uxy = 5.89kNm

= 0.628

Assume , reinforcement is equally distributed on four sides

Refer chart 48 of SP 16:1980,for =0.628, and ,weget

=0.06

= 129.6 kNm

Uniaxial moment capacity of section about yy-axis

b =600 mm

D =300 mm

= taken = 0.2

Refer chart 50 of SP 16:1980, for

=0.628, and

, we get

=0.06

= 64.8 kNm


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Calculation of P uz

Refer chart 63 of SP 16:1980, for p t = 2%, f ck = 20 N/mm 2 and ,

Puz = = 2700 kN

Refer chart 64 of SP 16:1980, for &

we get, permissible value of =0.9 So the percentage of steel assumed is correct.

= Provide 12 numbers of 20 mm ϕ bars distributed equally on four sides.

Lateral ties

According to IS 456:2000, clause 26.5.3.2(c)

The diameter of lateral ties shall be not less than1. One fourth of the diameter of the largest longitudinal bar = 6 mmHence adopt of lateral ties as 6 mm

Pitch

According to IS 456:2000,clause 26.5.3.2(c)

The pitch of transverse reinforcement shall be not more than the least of the following

distances:


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i. The least lateral dimension =300 mm

ii. Sixteen times the smallest diameter of the longitudinal reinforcement bar =16

=320 mm

ii. 300 mm

Hence adopt pitch as 300 mm

According to IS 13920:1993 clause 7.4.1

Special confining reinforcement should be provided over a length l o from each joint

face, towards mid span ,where l o shall not be less than

i. Larger lateral dimension of column =600 mm

ii. One-sixth of clear height of column = = 466.67 mmiii. 450 mm

Hence adopt l o as 600 mm

According to IS 13920:1993 clause 7.4.6 spacing of hoops used as special confining

reinforcement:

Hence adopt spacing of hoops =75 mm

So provide 6 mm ϕ bars at 75 mm c/c up to a length of 600 mm from face of the joint

towards mid span and 6 mm ϕ bars at 300 mm c/c at all other places.

Special confining reinforcement for column and joint details (according to IS

13920:1993)


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6.3 DESIGN OF BEAMS

6.3.1 GENERAL

A beam is structural element that is capable of withstanding load primarily

by resisting bending. The bending force induced in to the material of beam as result of

the external loads, own weight, span and external reactions to these loads is called a

bending moment.

Beams generally carry vertical gravitational forces but can also be used to

carry horizontal loads (ie., loads due to an earthquake or wind). The loads carried by

beam are transferred to columns, walls or girders, which then transfer the force to

adjacent structural compression members. In a light frame construction the joists the joists rests on the beam.

Beams are characterized by their profile (the shape of the cross section),

their length and their material. In contemporary construction, beams are typically made

of steel, reinforced concrete, or wood. The common type is I-beam or wide flange

beam. This is commonly used in steel – frame buildings and bridges. Other common

beams profiles are C-channel the hollow structural section beam, the pipe and the

angle.

6.3.1 DESIGN OF DOUBLY REINFORCED BEAM

Fig6.1: Bending moment diagram


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Fig.6.2 : Shear force diagram

Material constants


For M 15 Concrete, f ck = 15 N/mm2

For Fe 415 Steel, f y = 415 N/mm 2


Width of the beam =230 mm

Depth of the beam =600 mm

Assume 25 mm clear cover and 20 mm ϕ bars

Effective depth =600-25-10 = 565 mm

Ultimate moments and shear force (Left end)

Ultimate bending moment, M u = 177.18kNmUltimate shear force, V u =134.9 kN

Limiting moment of resistance

( ) = 0.138 = 0.138 = 151.98 kNm

Mu () , Hence design as doubly reinforced section


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2.413

p t(from SP16:1980)

0.818

Pc(from SP16:1980)

0.106

(required), mm 2

1062.99

( provided), mm 2

1256

(#4,20 ɸ)

(required), mm 2 137.75

( provided), mm 2

226.08

(#2,12 ɸ)

Ultimate moments and shear force (Mid span)

Ultimate bending moment, M u = 101.53 kNm

Ultimate shear force, V u =14.021kN


( ) = 0.138 = 0.138 = 151.98 kNm

Mu () , Hence design as single reinforced section

1.33

p t(from SP16:1980)

0.417

(required), mm 2

542

( provided), mm2

628

(#2,20 ɸ)


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Ultimate moments and shear force (Right end)

Ultimate bending moment, M u = 96.91 kNm

Ultimate shear force, V u =109.171kN


( ) = 0.138 = 0.138 = 151.98 kNm

Mu () , Hence design as single reinforced section 1.32

p t(from SP16:1980)

0.413

(required), mm 2

536.7

( provided), mm 2

628

(#2,20 ɸ)

Table 6.1: Reinforcement details of beam

Details Left end Mid span Right end

Moment

KNm

177.18 101.53 96.91

Shear

KN

134.9 14.021 109.17

2.413 1.33 1.32

p t(from SP16:1980)

0.818 0.72 0.72

Pc(from SP16:1980)

0.106 0.003 0.003

(required), mm2

1062.99 935.64 935.64


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( provided), mm 2

1256

(#4,20 ɸ,)

942

(#3,20)

942

(#3,20)

(required), mm 2 137.75 - -

( provided), mm 2

226.08

(#2,12 ɸ)

226.08

(#2,12 ɸ)

226.08

(#2,12 ɸ)

Check for shear stress

As per IS 456:2000 clause 40.1

=

= 1.038 N/mm 2

( ) = = 0.966

As per IS 456:2000 ,table 19

Permissible stress , =0.59 N/mm 2

As per IS 456:2000 clause 40.4,

Strength of shear reinforcement, V us = V u (τc b d)

= (134,9 ) – (0.59 )

=58.23 KN


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= 1.03 kN/cm

As per SP 16:1980, table 62

Provided = 1.037 kN/cm

Use 8mm ϕ 2 legged stirrups @ 250 mm c/c

According to IS 456:2000, clause 26.5.1.5,

The spacing of stirrups in beams should not exceed the least of

a) 0.75d =0.75 =423.75 mm

b) 300 mm

Maximum spacing of shear reinforcement = 300 mm

Therefore provide 8 mm Φ 2 legged stirrups @ 250 mm c/c up to a distance of 0.25 L ef fromthe face of the support and provide 8 mm Φ 2 legged stirrups @ 300 mm c/c in all other

places.


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6.4 DESIGN OF STAIRCASE

6.4.1 GENERAL

Staircase in a building, facilitate easy vertical movement of person from one

floor to another.

Stairway, staircase, stairwell, flight of stairs or simply stairs are names for

construction design to bridge a large vertical distance by dividing in to smaller vertical

distance called steps. Stairways may be straight around or may consist of two or more

straight piece connected at angles.

Special stairways include escalators and ladders. Alternative to stairways are

elevators, stair lifts and inclined moving sidewalks as well as sanitary inclined sidewalks.

TYPES OF STAIRCASE

Dog legged staircase Open well staircase

Spiral staircase Quarter turn staircase

6.4.2 DESIGN OF DOGLEGGED STAIRCASE

Material Constants:-

Concrete, f ck = 15 N/mm 2

Steel, f y

= 415 N/mm 2

Span, tread & rise of the stair are taken from the architectural drawings provided.


Effective span l eff = 5465 mm

Thickness of slab =

= 200 mm


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Provide 10 mm diameter bars

Clear cover = 25 mm

Effective depth, d = 170 mm

Rise of stair = 170 mm

Tread of stair = 300 mm

Thickness of the waist slab = 200 mm

Load calculation

Dead load of waist slab = √ √ The self-weight of the steps is calculated by treating the step to be equivalent horizontal

slab of thickness equal to half the rise

Self-weight of step =0.5

=0.5

Floor finish = 1 As per IS: 875(Part 2)-1987 Table-1

Live load = 4 Total service load = 12.875 Consider 1 m width of waist slab

Total service load / m run =12.875

= 12.875

Total ultimate load = w u =


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Ultimate design moment

Maximum B.M at the center of span is given by;

Mu = =

= 71.85 kNm

Check for depth of waist slab

= =

=186 mm

Hence the effective depth selected is sufficient to resist the ultimate moment.

Reinforcements

From sp16, table 22

⁄

( )=1256 mm 2

Check for spacing

As per IS 456:2000 clause 26.3.3(b)

Maximum spacing = { }

= { }


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= 300 mm

Check for area of steel

As per IS 456:2000 clause 26.5.2.1

( ) =

= 240 mm 2

( ) ()

Distribution Steel

Distribution reinforcement = 0.12 of cross – sectional area

= 240 mm 2

Use 8 mm bars

= = 210 mm

Provide 8 mm bars at 200 mm c/c.

Check


Maximum spacing = { } = {

}

= 450 mm


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Check for shear

=

= 52.68 kN


τ =

= 0.301 N/mm 2

= τ


Maximum shear stress, (τ ) τ τ (τ )


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6.5 SLAB DESIGN

6.5.1 GENERAL

Reinforced concrete slabs consists the most common type of structuralelements used to cover roofs and floors of buildings. One way slabs are supported on

opposite sides and the loads are transmitted in one direction. The reinforced concrete

slab supported on all the four edges with the two way slabs ratio of long to short span

not exceeding 2 are referred to as two way slabs. Slabs projecting from supports or

beams are termed as cantilever slabs. Reinforced concrete slabs supported only on

columns without beams are called as flat slabs sloping slabs are adopted in the case of

shell roof etc. In general the main reinforcement in slabs is provided in the principle

bending direction of the slab.

Most of slab used in building have an overall thickness in the range of 100

mm to 200 mm while thicker slabs in the range of 200 mm to 500 mm is required in the

case of bridge decks to resist heavy loads of vehicles the slabs are designed as beams of

unit width for a given type of loading and support conditions. The percentage of

reinforcement in slab is generally low in the range of 0.30 to 0.50 percent.

TYPES OF SLAB

Slabs are classified according to the system of support used as under.

Two way spanning slab Circular and other shapes Cantilever slabs Flat slab supported directly on column without beams.

6.5.2 DESIGN OF TWO WAY SLAB

Material constants


For M20 Concrete, f ck = 15 N/mm2

For Fe 415 Steel, fy = 415 N/mm 2


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Type of slab

Centre to Centre distance of longer span, = 6 m

Centre to Centre distance of shorter span, = 4 m

Two way slab

Type of slab: two adjacent edges discontinuous


As per IS456:2000, clause 24.1,

Thickness of slab =

=

=114 mm

Provide a 120 mm thick slab.

Assume 20 mm clear cover and 10 mm ϕ bars

Effective depth along shorter direction, d x = 95mm

Effective depth along longer direction, d y = 85mm

Effective span

As per IS 456:2000, clause 22(a)

Effective span along short and long spans are computed as:

=clear span +effective depth =4 +.095 = 4.095 m

=clear span +effective depth =6 +.085 = 6.085 m

Load calculation

Dead load of waist slab = Floor finish = 1 As per IS: 875(Part 2)-1987 Table-1

Live load = 4


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Total service load = 8

Design ultimate load, =1.5 8 = 12 Ultimate design moment

Refer table 26 of IS 456:2000 and read out the moment coefficients for

Short span moment coefficients:

a) – ve moment coefficient = =0.075 b) + ve moment coefficient = =0.056

Long span moment coefficients:

a) – ve moment coefficient = =0.047 b) + ve moment coefficient = =0.035( ) = = = 15.092 kNm( ) = = 11.268 kNm( ) = = 9.45 kNm

( ) = = 7.043 kNmCheck for depth( ) = 0.138

= ( ) =

=85.38mm

(95 mm)

Hence the effective depth selected is sufficient to resist the design ultimate moment.


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d) Reinforcements along short and long span directions

The area of reinforcement is calculated Referring sp16, table 17, for slab thickness

120mm with 8mm and 10mm ɸ bars

Table 6.2 reinforcement details in two way slab

Table 6.1: Reinforcement details of slab

Check for spacing


Maximum spacing = { } = { } = 285 mm

Check for area of steel

As per IS 456:2000 clause 26.5.2.1

( )

Location (required) (provided)

1)short span

Edge section

Mid span section

10mm ɸ@ 160mm c/c

10mm ɸ@ 220mm c/c

10mm ɸ@ 150mm c/c

10mm ɸ@ 210mm c/c

2)long span

Edge sectionMid span section

8mm ɸ@ 170mm c/c

8mm ɸ@ 240mm c/c 8mmɸ@ 160mm c/c

8mmɸ@ 230mm c/c


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=

= 144 mm 2

( ) = 373 mm 2( ) ()

Check for deflection:

( ) = 373 mm²( ) = 356 mm²

f s = ( )( ) =

= 208.06

P t = = 0.39

As per IS 456:2000, fig 4, page 38

Modification factor = 1.7

As per IS 456:2000, clause 23.2.1

= 26

=26

= = 43

So deflection is safe with provided depth.


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Check for shear

=

= 24.57 kN


τ = = 0.388 N/mm 2

= τ = 0.41 N/mm 2


Design shear strength of concrete = τ = 1.3 = 0.53 N/mm 2


Maximum shear stress, (τ ) τ τ (τ )

Check for cracking

As per IS 456:2000, clause 43.1:

1. Steel provided is more than 0.12 percent

2. Spacing of main steel 3. Diameter of reinforcement

Hence cracks will be within the permissible limits


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6.6 DESIGN OF RCC DOME

6.6.1 GENERAL

Concrete domes are generally preferred to cover circular tanks and for roofsof large span structures which are circular in shape such as sports area, mosques , and

churches where un interrupted floor space is desirable. The spherical domes supported by

ring beam at the base.

The thickness of reinforced concrete spherical dome is generally not less

than of the diameter with the values of 50 mm-100 mm for domes in the range of

25m-50m respectively. The reinforcement in the dome is made up of wire mesh and

concrete is placed in concentric rings over preformed framework or the dome can be

formed by gunniting using micro concrete.

6.6.2 DESIGN OF RCC DOME -central portion above the 2 ND floor of Mosque

Data:

Span of dome, D = 4.23 m

Thickness of dome, t = 120 mm

Central rise, r = 2 m

M15, ie., f ck = 15 N/mm 2

Fe415, ie., f y = 415 N/mm2

Compressive strength of steel = 100 N/mm 2

Load calculation:

The self-weight of the slab = (0.12*1*1)25 = 3.00 kN/m 2

Floor finishes = 1 kN/m 2

The total load, = 4 kN/m 2

Factored load W= 6 kN/m 2

Determination of stresses:

1) Meridianal thrust, M T =

MT = ( ) ( ) (R= = = 2.118 m)


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MT = 8.85 kN/m (sin = , = 64.15 )

Meridianal stress,

MS =

=

( ) = 0.07375 N/mm 2

MS = 0.07375 N/mm 2 cc = 4 N/mm 2 (IS 456 : 2000 p.no:81 ) Hence, it is safe

2) Hoop thrust, H T = WR(cos )

HT = 6*2.118*(cos64.15 )

HT = -3.308 kN/m

Hoop stress,

HS = = ( ) = -0.027 N/mm2

HS = -0.003 N/mm 2 cc = 4 N/mm 2 Hence, it is safe

But these stresses are very low. Therefore minimum of 0.30% of the dome area will be

adopted as the reinforcement.

ie., minimum reinforcement, A st = 0.30%(bD)

Ast = *(1000*120)

Ast = 360 mm2

Spacing, s = ( )*1000 = ( )*1000 (assume, diameter = 12

mm)

s = 314.16 mm ≈ 300mm c/c

Provide main reinforcement of 12 mm diameter @ 300 mm c/c spacing.

Therefore, actual area, A st = = 377 mm 2

Design of ring beam:

Hoop tension,

Ft = = ( ) Ft = 20.14 kN


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The reinforcement required,

Ast = Ast =

mm 2

Number of bars, n = = = 1.78 4 numbers (assume 12 mm diameter

bars)

Provide 4 numbers of 12 mm diameter rods as ring beam reinforcement.

Therefore, actual area, A st = 4*113.10 = 452.40 mm 2

Determination of the size of ring beam:

The c/s area of the ring beam, ( ) = 1.20

( ) = 1.20 (m = = 13.33)

Ac = 11205.36 mm2 (assume square

beam)

So, the size of ring beam is given as 150 mm*150 mm.


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6.7 DESIGN OF WATER TANK

6.7.1 GENERAL

The large container in which the water is made to occupy is popularly known as

water tank. The main factors want to consider while constructing a water tank is its resistance

against crack, corrosion, permeability. Water tightness is also an important criterion in water

tanks. Usually richer mixes with M20, M30 concrete are used. The tensile stresses permitted

in concrete are restricted to control cracking. In concrete as per IS: 3370, part II, 1965.

TYPES OF WATER TANK

Water tank resting on the ground Underground tanks Elevated water tanks on staging

6.7.2 DESIGN OF UNDERGROUND WATER TANK (rectangular)

Data:

Length = 3.60m

Breadth = 1.60m

Depth, H = 0.70m

Weight of soil, w = 20 kN/m 3

M20, ie., f ck = 20 N/mm2

Fe415, ie., f y = 415 N/mm 2

Check for design:

2.25 > 2.00

The long walls are designed as vertical cantilevers and the short walls are designed as thehorizontal slabs spanning between long walls.

Design of long walls:

Vertical reinforcement:


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The coefficient of earth pressure, k a = (assume wet soil, = 6 )

k a = = 0.81

When tank is full:

The maximum pressure developed by wet soil,

Ps = kawH

Ps = 0.81*20*0.70

Ps = 11.34 kN/m2

The maximum water pressure developed,

Pw = W w*HPw = 10*0.70 = 7.00 kN/m

2 Therefore, the net pressure,

Pn = 11.34 – 7.00 = 4.34 kN/m 2 The maximum bending moment near the water surface,

= = 0.06 kNm

And the maximum bending moment away from the water surface

= = 0.14 kNmWhen the tank is empty:

There is no water pressure, hence P w = 0 kN/m2

Therefore, the net pressure,Pn = 11.34 – 0.00 = 11.34 kN/m 2

The maximum bending moment near the water surface,

= = 0.16 kNm

And the maximum bending moment away from the water surface

= = 0.37 kNmThe depth of the slab,

M = 0.28*bD 2 0.37*10 6 = 0.28*1000*D 2 D = 36.35 mm 60 m

d = 60 – (15) – ( ) (assume 10 mm diameter) d = 40 mm


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for away,

Ast = = = 93.53 mm2

Spacing, s = ( )*1000 = ( )1000 = 840 mm (assume 10 mm diameter)

Maximum spacing, s 1 = 3d = 5*60 = 180 mm

s2 = 300 mm

Provide 10 mm diameter bars @ 180 mm c/c spacing (for 2 faces)

Therefore, actual area, A st = = 436.33 mm2

for near,

Ast = = = 40.44 mm 2



s2 = 300 mm

Provide 8 mm diameter bars @ 180 mm c/c spacing (for 2 faces).

Therefore, actual area, A st = = 280 mm2

Horizontal reinforcement:

The horizontal reinforcement area, A st = 0.30%(bD)

Ast = *(1000*60)

Ast = 180 mm2/2 = 90 mm 2

Spacing, s = ( )*1000 = ( )1000 = 558.55 mm (assume 8 mm

diameter)


s2 = 300 mm




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Design of short walls:

Horizontal reinforcement:

The maximum pressure developed by wet soil = 11.34 kN/m 2

The bending moment @ corners for short walls,

M = = = 0.46 kNm

Therefore, the area of reinforcement,

Ast = = = 116.28 mm2


Maximum spacing, s 1 = 3d = 3*60 = 180 mms2 = 300 mm



Vertical reinforcement:

The horizontal reinforcement area, A st = 0.30%(bD)

Ast = *(1000*60)

Ast = 180 mm2



s2 = 450 mm



Design of slab:

Assume, the overall depth of slab, D = 100 mm

Therefore, the effective depth, d = 100 – (15) – ( ) (assume 12 mm diameter)

d = 80 mm


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The dead load of the slab = (0.08*1*1)25 = 2.00 kN/m 2

Assume, live load = 1.50 kN/m 2 Assume, floor finish = 0.60 kN/m 2 Therefore, total load W = 4.10 kN/m 2

The maximum bending moment, M = = = 2.48 kNm

Check for depth,

M = Qbd 2

2.48*10 6 = 1.21*1000*d 2

d = 45.27 mm < 80 mm hence, it is safe

Area of main reinforcement:

Ast = = = 313.45 mm2

Spacing, s = ( )*1000 = ( )1000 = 360.82 mm (assumed diameter is 12 mm)


s2 = 300 mm

Provide 12 mm diameter bars @ 240 mm c/c spacing.


Area of distribution reinforcement:

The distribution reinforcement area, A st = 0.30%(bD)

Ast = *(1000*100)

Ast = 300 mm2



s2 = 300 mm




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CHAPTER 7

SITE VISITS

17.1. SITE VISIT TO APOLLO BUILDERS MANJERI

As part of this training, a site visit was conducted to the construction site of apollo builders,

Manjeri. It is R.C.C framed structure having two towers. The tower 1 has G+15 floors and the

tower 2 has G+ 14 floors. The construction techniques adopted for boring and concreting of

Direct Mud Circulation (D.M.C) pile were observed. The hard rock available at the site was

at a depth of 10m.

The diameters of the piles are 600, 700 and 800 mm. The piles are driven up to a depth of 10

m were hard strata was available. The process of pile driving and concreting of piles were

clearly observed and understood.

D.M.C pile is Direct Mud Circulation pile where water jet is let through the piling chisel

which comes out from bottom with mud. In D.M.C pile foundation the bentonite suspension

is pumped into the bottom of the hole through the drill rods and it overflows at the top of the

casing. The mud pump should have the capacity to maintain a velocity of 0.41 to 0.76m/s to

float the cuttings.

Fig 7.1. D.M.C piling


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Fig 7.2. Reinforcement in retaining wall

Fig 7.3. Reinforcement in column


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7.2. SITE VISIT TO APOLLO BUILDERS, CALICUT.

The second site visit was to the construction site of apollo builders, Calicut. It has got

both the villa and the apartment. The apartment has 2 basement floor and the ground floor for

car parking and 6 floors.

Fig.7.4. Reinforcement in beam


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Fig 7.5. Sunken slab

In villas, foundation and reinforcement of roof slab construction was completed. For two way

slabs, the spacing for top and bottom reinforcement is different while for one way slab, the

top and bottom spacing are same. Framed section of beam columns were completed for villas.

Fig.7.6 Concealed beam


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CHAPTER 8

CONCLUSION

The industrial training, taken through a period of three months allowed me to gain

ample exposure to various field practices in the analysis and design of multi- storied

buildings and also in various construction techniques used in the industry. The analysis was

done using the software package STAAD Pro v8i and the drawing details in Auto CAD 2010.

All the structural components were designed manually. The use of the software offers saving

in time, It takes value on safer side than manual work. Hence manual design was adopted.

The analysis and design was done according to standard specifications to the possible extend.

The various difficulties encountered in the design process and the various constraints faced

by the structural engineer in designing up to the architectural drawing were also well

understood. This training helped to understand and analyse the structural problem faced by

the construction industry. Site visits also gave me an exposure to the industry.


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REFERENCES

1. S.Unnikrishna Pillai & Devadas Menon “Reinforced Concrete Design”. Tata

McGraw-Hill Publishing Company Limited, New Delhi, 2003.

2. N Krishna Raju, “Advanced Reinforced Concrete Design”, C.B.S Publishers and

Distributers, New Delhi,2004

3. P.C. Varghese, “Advanced Reinforced Concrete Design” , Prentice-Hall of India

Private Limited, New Delhi, 2008.

4. Pankaj Agarwal & Manish Shrikhande “Earthquake Resistant Design of Structures”,

Prentice-Hall of India Private Limited, New Delhi, 2007.

5. IS: 456- 2000, “ Indian Standard Plain and Reinforced Concrete-Code of Practice ” ,

Bureau of Indian Standards, New Delhi.

6. IS: 875 (Part I)- 1987, “ Indian Standard Code of Practice for Design Loads

(Other than earthquake) for Building and Structures” , Bureau of Indian Standards,

New Delhi.

7. IS: 875 (Part II)- 1987, “ Indian Standard Code of Practice for Design Loads


New Delhi.

8. IS: 875 (Part III)- 1987, “ Indian Standard Code of Practice for Design Loads


New Delhi

9. IS: 1893 (Part I)-2002, “ Indian Standard Criteria for earthquake Resistant Design of

Structures”, Bureau of Indian Standards, New Delhi.

10. IS: 3370 (Part II)- 1965, “ Indian Standard Code of Practice for Concrete Structures for

the Storage of Liquids”, Bureau of Indian Standards, New Delhi.


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