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CHAPTER I

INTRODUCTION

1.1 Self Balancing Testing Frame-400KN

Steel structures and steel truss is mostly used in civil engineering to withstand the load

in bridges and factory roof etc. The design calculations are based on readily available

data that has been provided in the steel tables and graphs. But once the truss is

fabricated there was no way to actually test its reliability. The testing of component was

also not possible till universal testing frame technique came into existence. This

frame provides facility to check the performance of truss up to a load of 400kN. It also

provides facility to analysis the various components at 1:1 scale, thus facilitates the

designers to satisfy their calculation in accordance with the requirement of actual

location.

1.2 Versatile Design

This Universal Testing Frame consist of double frame which provides more stability

to the truss modes that is being tested moreover the intermediate space to test the

specimen that all longer in dimension than the frame itself.

1.3 Easy Assembly & Erection

This Universal Testing Frame is collapsible and it can be dismantled and erected

wherever required. Therefore it can be transported to any place easily.

1.4 Manufactured by local material

The materials used in the universal testing frame are generally available in local

market and need no import or special specification. Therefore it is economical. Theerection and assembly etc. does not require very special skill. It can be easily done with

the help of skilled persons those are easily available at factory sites. The erection is also

possible with the help of chain pulley blocks.

The foundation needed for the universal testing frame is also very simple due to fact

that there are not point load on the foundation directly. We get a distributed load

through the frame. Therefore it facilitates the testing procedures immediately after its

assembly without demanding any complicated fabrication.

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1.5 Facility of Direct Analysis

This system provides almost similar conditions that are expected on the place of

erection of the truss so we can analysis the model for the following structural elements

present in the structure.(i) Tension element in the member

(ii) Compression element in the member

(iii) Flexural element in the member

(iv) Tortional element in the member.

1.6 It is portable too

It can be easily shifted or carried along from site to site. Thus we can easily use it for

consultancy and commercial purpose. In this manner this frame can be used for

modifying the existing truss or structure because we can easily make a model on site

and put it under the test to satisfy the requirement. It will save lot of time, money and

manpower.

1.7 Need of Loading Frame

Though there are various methods of design of structure available which fulfill the

above criteria yet there is need of some practical knowledge that how a component of a

structure behave under the application of load. One can easily identified the end

reaction of beam or trusses or the forces acting on the two when subjected to certainexternal forces. But it is difficult to imagine the actual behaviour of a structural

component due to application of load. Thus this load bearing frame prove to be an

important tool to enhance the version of a structural designer towards the structural

behaviour of a member because of external forces applied over it.

For example, if a truck runs into a bridge composed of plate girders it would probably

bend the steel plate a little however a similar accident could cause the breaking of a

members in truss which may even lead to the failure of truss. Thus the above can be

easily computed with help of a load bearing frame. The truss of suitable scale may bemanufacture & with the help of the loading frame by providing loading one can check

the failure mode of a structure. This also play an important role in order to understand

the behaviour of structural material & their properties under certain loading conditions.

It can be used to check the different physical properties of a various structure such as

plate girder, trusses, beams, box type girder, column beams, gantry girders etc.

This universal testing frame is specially designed for large components in 1:1 scale.

The design with its double frame & intermediate space permits specimens longer than

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the size of frame opening to be investigated. In this way the possible uses of testing

frame are almost unlimited. The frame components are manufactured from ISMC 400.

The corners of frame are formed by joints rigid to bending each in fastened together

with a high strength bolts. The testing frame is delivered in pre-assembled modules; it is

assembled on site and placed on four adjustable vibration damping bearing. The

hydraulic ram system are available as accessories are on rollers and can be positioned

as require within frame. The various experiments that can be performed using this

frame are bending, loading, compression experiments on large girders beams, trusses

and other components from the area of civil engineering work. This could be used for a

Test force in central position maximum 300 kN and test force off centered 2x200 kN.

Another importance of this frame is for educational purpose. We know that a structuralmember subjected to compressive forces along its axis is termed as a compression

member. The behaviour of compression member differ based on their length, short &

stocky columns can be loaded up to their Yield stress and can attain their squash loads,

provided the element that makeup the cross section are prevented from buckling long

compression members behaves elastically and hence their strength may be predicted by

Eulers formula. Intermediate length compression member fail both by yielding and

buckling and hence their behaviour is inelastic. This can be easily understood with thehelp of the frame by providing the length of various compression members can one can

provide an easy practical example to the student of structural analysis. The buckling

behaviour of column under different end connections can be practically demonstrated to

the students of civil engineers.

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CHAPTER II

LITERATURE REVIEW

2.0 General

Structural design, though reasonably scientific is also a creative process. A structure is a

body composed of several structure elements so assembled that it can setup resistance

against deformation caused due to application of external forces. The various structural

elements that may be present in a structure are

(i) Tension member

(ii) Compression member

(iii) Flexural member(iv) Torsion member

(v) Foundation elements.

The structural analysis deals with the determination of internal stress in these members

as well as the determination of reaction components, when structure is subjected to

external forces. The method of analysis and principle involved in structural analysis do

not normally depend upon the type of material used for various structural components.

Structural design is taken up after the structural analysis has two aspects.(i) Functional Aspect

(ii) Strength Aspect

In the 1st aspect of design, the structure is design in such a way that it fulfills its

intended purpose during its intended lifetime and be adequately safe in terms of

strength, stability and structural integrity.

In the 2nd Aspect, the structure should be strong enough to resist against external forces

to which it is subjected during its entire period of service.In addition to above two aspects of design a structure should be economically viable in

terms of cost of construction and maintenance, aesthetic pleasing & environment

friendly. Safety is paramount importance in any structure and requires that the

possibility of collapse of structure (partial or total) is acceptable low not only under

normal expected loads (service loads) but also less frequent loads (such as due to EQ or

extreme winds) and accidental loads (blast, impact etc.). Collapse due to various

possibilities such as exposure to a load exceeding. The load bearing capacity

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overturning, sliding, buckling, fatigue, fracture etc should be prevented. The

progressive failure should also be minimized. The structure should also perform

satisfactorily under service loads without any discomfort to the user due to excessive

deflection, cracking, vibration etc. The serviceability should be fulfilled.

2.1 Steel

There is a definite need for engineers involved in structural steelwork to acquaint

themselves with some metallurgical aspects of steel. This will help the structural

engineer to understand ductile behaviour of steel under load, welding during fabrication

and erection and other important aspects of steel technology such as corrosion and fire

protection.

2.1.1 The crystal structure and the transformation of iron

Pure iron when heated from room temperature to its melting point undergoes several

crystalline transformations and exhibits two allotropic modifications such as:

(i) Body centered cubic crystal (bcc),

(ii) Face centered cubic crystal (fcc).

When iron changes from one modification to the other, it involves the latent heat of

transformation. If iron is heated steadily, the rise in temperature would be interrupted

when the transformation starts from one phase to the other and the temperature remainsconstant until the transformations are completed. The flat portion of the

heating/cooling curve in Fig. 5 exemplifies this. On cooling of molten iron to room

temperature, the transformations are reversed and almost at the same temperature when

heated as shown in Fig. 5. Iron up to a temperature of 910C remains as ferrite or -

iron with bcc crystalline structure. Iron is ferromagnetic at room temperature, its

magnetism decreases with increase in temperature and vanishes at about 768C called

the Curie point. The iron that exists between 768C and 910C is called the -ironwith a bccstructure. However, in the realm of metallurgy, this classification does not

have much significance.

Between 910C and 1400C, iron transforms itself into austeniteor -iron with

face centred cubic (fcc) structure. When temperature is further increased, austenite

reverts itself back to bcc structure, called the -ferrite. Iron becomes molten beyond

1539C. The different phases of iron are summarised in Table 1.

Table 2.1: Various forms of Iron

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Stable Temp. Range 0C Form of matter Phase Identification symbol

>2740 Gaseous Gas Gas

1539-2740 Liquid Liquid Liquid

1400-1539 Solid bcc -ferrite

910-1400 Solid fcc -austenite


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of steels. More amount of carbon causes problems during the welding process. Wewill see later, how both mechanical strength and ductility of steel could be improvedeven with low carbon content. The iron-carbon equilibrium diagram, which is a plot of

transformation of iron with respect to carbon content and temperature, is shown in Fig.7. This diagram is also called iron-iron carbide diagram. The important metallurgicalterms, used in the diagram, are presented below.

Table 2.2: Metallurgical terms of iron

2.1.3 The Structural Steels or ferrite Pearlite Steels

The iron-iron carbide portion of the phase diagram that is of interest to structural

engineers is shown in Fig. 8. Temp

0C

0.0

200

400

600

800

1000

1200

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2

7230C

Austenite ()1147 C

Ferrite

Ferrite + Pearlite

Ferrite +

Austenite +

Weight % of Carbon

Hypo-Eutectoid

Eutectoid

Cementite + Pearlite

Hyper-Eutectoid

ba c d

i

j

k

l

Fig. 2.2: The Eutectoid section of the Iron Iron Carbon phase diagram

The phase diagram is divided into two parts called hypoeutectoid steels (steels with

carbon content to the left of eutectoid point [0.8% carbon]) and hyper eutectoid steels

7

NameMetallurgical

term% Carbon(max)

Crystal

structure

- Iron Ferrite 0.02 bcc

Fe3C Cementite 6.67 -

Ferrite + Cementitelaminar mixture Pearlite 0.80 (overall) -

- Iron Austenite2.0 (depends on

temperature) fcc


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which have carbon content to the right of the eutectoid point. It is seen from the figure

that iron containing very low percentage of carbon (0.002%) called very low carbon

steels will have 100% ferrite microstructure (grains or crystals of ferrite with irregular

boundaries) as shown in Fig. 9(a). Ferrite is soft and ductile with very low mechanical

strength. This microstructure at ambient temperature has a mixture of what is known as

pearlite and ferrite as can be seen in Fig. 8. Hence we see that ordinary structural

steels have a pearlite + ferrite microstructure. However, it is important to note that

steel of 0.20% carbon ends up in pearlite + ferrite microstructure, only when it is cooled

very slowly from higher temperature during manufacture. When the rate of cooling is

faster, the normal pearlite + ferrite microstructure may not form, instead some other

microstructure called bainite or martensite may result.

Fig.2.3: Microstructures of steels

(a) 100% Ferrite in extra low carbon steel, (b) Ferrite+Pearlite,

(c) 100% Pearlite in eutectoid steel, (d) Pearlite+Cementite in hyper-eutectoid steel

(Source: Thelning K.E., Steel and its heat treatment, Butterworths, 1984.)

Table 2.3: Chemical composition of some typical structural steels

Type of steel Designation

IS:

code C S Mn P Si Cr

Carbon

equivalent

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Standardstructural steel

Fe 410A 2062 0.23 .050 1.5 .050 - - SK 0.42

Fe 410B 2062 0.22.

045 1.5.

0450.4 - SK 0.41

Fe 410C 2062 0.20.

040 1.5.

0400.4 - K 0.39

Micro alloyedhigh strength

steel

Fe 440 8500 0.20 .050 1.3 .050.

45 0.40

Fe540 8500 0.20.

045 1.6.

045.

45 0.44

Fe590 8500 0.22.

045 1.8.

045.

45 0.48

K- killed steel SK- Semi Killed steel (Explained in section 6.2)

2.2 Mechanical Properties of Steel

2.2.1 Stress strain behaviour: Tensile test

The stress-strain curve for steel is generally obtained from tensile test on standard

specimens as shown in Fig.14.

P

P

r

t

d

Lc

Area=S0-

L

Fig.2.4: Standard tensile test specimen

The details of the specimen and the method of testing is elaborated in IS: 1608 (1995).

The important parameters are the gauge length Lc and the initial cross section area So.

The loads are applied through the threaded or shouldered ends. The initial gauge length

is taken as 5.65 (So)1/2 in the case of rectangular specimen and it is five times the

diameter in the case of circular specimen. A typical stress-strain curve of the tensile

test coupon is shown in Fig.15 in which a sharp change in yield point followed by

plastic strain is observed. When the specimen undergoes deformation after yielding,

Luders lines or Luders bands are observed on the surface of the specimen as shown in

Fig.16.

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of elasticity can be taken as 205,000 MPa and the tangent modus at the onset of strain

hardening is roughly 1/30th of that value or approximately 6700 MPa.

f

y

fy

0.2% strain

Uniform plastic

Fracture

Non-uniform plastic

Elastic

0.2% proof stress

Fig. 2.7: Stress strain curve for continuously yielding structural steels

2.2.2 Hardness

Hardness is regarded as the resistance of a material to indentations and scratching. This

is generally determined by forcing an indenter on to the surface. The resultant

deformation in steel is both elastic and plastic. There are several methods using which

the hardness of a metal could be found out. They basically differ in the form of the

indenter, which is used on to the surface. They are presented in Table 6.

Table 2.4: Hardness testing methods and their indenters

S.

No.

Hardness Testing

MethodIndenter

(a) Brinell hardness Steel ball

(b) Vickers hardness Square based diamond pyramids of 135 O included angle

(c) Rockwell hardness Diamond core with 120 O included angle

Note: Rockwell hardness testing is not normally used for structural steels.

Table 2.5: Hardness values of some metals

Metal

Brinell Hardness Number

(BHN)

Vickers Hardness Number

(VHN)

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Copper (annealed) 49 53

Brass (annealed) 65 70

Steel 150-190 157-190

2.2.3 Mechanical properties of structural steel

Table 8 summarises some of the important mechanical properties of steel produced in

India. In Table 8, the UTS represent the minimum guaranteed Ultimate Tensile

Strength at which the corresponding steel would fail.

Table 2.6: Mechanical properties of some typical structural steels

Type of

steelDesignation

UTS

(MPa)

Yield strength

(MPa) ElongationGauge

065.5 S

Charpy V -notch values

Joules (min)Thickness (mm)

40

Standardstructura

l steel

Fe 410A 410 250 240 230 23 27

Fe 410B 410 250 240 230 23 27

Fe 410C 410 250 240 230 23 27


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rolling has high strength but very poor ductility. This product needs to be annealed at

650-6800C in the hood annealing furnaces to improve its ductility.

Now-a-days hollow sections are also becoming very popular. Hollow sections i.e.

round; square or rectangular are produced either by seamless rolling process or by

fusion welding or electric resistance welding after cold forming of HRC/CRC into the

desired shape.

2.3 Tension Members

2.3.1 Introduction

Tension members are linear members in which axial forces act so as to elongate

(stretch) the member. A rope, for example, is a tension member. Tension members

carry loads most efficiently, since the entire cross section is subjected to uniformstress. Unlike compression members, they do not fail by buckling.

Stay cables

Stayed bridge

Suspenders

Suspension bridge

(b) Cable Supported Bridges

(a) Roof TrussTie

RafterSuspenders

(c) Suspended

Building

(d) Roof Purlin System

Purlin

Top chord

(e) Braced Frame

X bracings

Fig. 2.8: Tension Members in Structures

Tension members are also encountered as bracings used for the lateral load resistance.

In X type bracings [Fig.1 (e)] the member which is under tension, due to lateral loadacting in one direction, undergoes compressive force, when the direction of the lateral

load is changed and vice versa. Hence, such members may have to be designed to resist

tensile and compressive forces.

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The various factors which govern the failure of tension member are:

(i) The rupture of net section at end connections where tensile stresses are

largest.

(ii) The block shears failure at end connections.

(iii) The yield strength of cross section.

The 1st two failure modes will governs when the members are connected at ends by

bolts where as the yield strength of gross section may be the governing failure mode of

tension members connected by welding at ends. The above criteria can be easily

demonstrated with the help of using Universal testing frame under diff loading

conditions.Thus universal testing frame proves to be an important tool not only for the educational

purpose but it can also figure out the actual behavior of only structural component

underspecified loading condition. These properties of materials to be used for

construction of structure under the different loading conditions.

(a) (c)

(d) (e)

(b)

Fig. 2.9: Cross Sections of Tension Members

The tension members can have a variety of cross sections. The single angle and double

angle sections [Fig 2(a)] are used in light roof trusses as in industrial buildings. Thetension members in bridge trusses are made of channels or I sections, acting

individually or built-up [Figs. 2(c) and 2(d)]. The circular rods [Fig.2 (d)] are used in

bracings designed to resist loads in tension only. They buckle at very low compression

and are not considered effective. Steel wire ropes [Fig.2 (e)] are used as suspenders in

the cable suspended bridges and as main stays in the cable-stayed bridges.

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2.3.2 Behaviour of Tension Members

Since axially loaded tension members are subjected to uniform tensile stress, their load

deformation behaviour (Fig.3) is similar to the corresponding basic material stress

strain behaviour. Mild steel members (IS: 2062 & IS: 226) exhibit an elastic range (a-

b) ending at yielding (b). This is followed by yield plateau (b-c). In the Yield Plateau

the load remains constant as the elongation increases to nearly ten times the yield strain.

Under further stretching the material shows a smaller increase in tension with

elongation (c-d), compared to the elastic range. This range is referred to as the strain

hardening range. After reaching the ultimate load (d), the loading decreases as the

elongation increases (d-e) until rupture (e). High strength steel tension members do not

exhibit a well-defined yield point and a yield plateau (Fig.3). The 0.2% offset load, T,as shown in Fig. 3 is usually taken as the yield point in such cases.

T

a

b c

de

0.2%

Fig. 2.10: Load Elongation of Tension Members

The important factors to be considered while evaluating the tensile strength are the

reduction in strength due to bolt holes and due to eccentric application of loads through

gusset plates attached to one of the elements. The yield strength of the gross area or the

ultimate strength of the net area may govern the tensile strength. The effect of

connecting the end gusset plate to only one of the elements of the cross section was

empirically accounted for by the reduction in the effectiveness of the outstanding leg,

while calculating the net effective area.

2.4 Compression Members

2.4.1 Introduction

There are many types of compression members, the column being the best known. Top

chords of trusses, bracing members and compression flanges of built up beams and

rolled beams are all examples of compression elements. Columns are usually thought of

as straight vertical members whose lengths are considerably greater than their cross-

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sectional dimensions. An initially straight strut or column, compressed by gradually

increasing equal and opposite axial forces at the ends is considered first. Columns and

struts are termed long or short depending on their proneness to buckling. If the

strut is short, the applied forces will cause a compressive strain, which results in the

shortening of the strut in the direction of the applied forces. Under incremental loading,

this shortening continues until the column "squashes". However, if the strut is long,

similar axial shortening is observed only at the initial stages of incremental loading.

Thereafter, as the applied forces are increased in magnitude, the strut becomes

unstable and develops a deformation in a direction normal to the loading axis. (See

Fig. 1). The strut is in a buckled state.

Buckling behaviour is thus characterized by deformations developed in a direction (orplane) normal to that of the loading that produces it. When the applied loading is

increased, the buckling deformation also increases. Buckling occurs mainly in

members subjected to compressive forces. If the member has high bending stiffness, its

buckling resistance is high. Also, when the member length is increased, the buckling

resistance is decreased. Thus the buckling resistance is high when the member is

stocky (i.e. the member has a high bending stiffness and is short) conversely, the

buckling resistance is low when the member is slender.

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Fig. 2.11: Long column vs short column

17

A short column failsby compression yield

Buckledshape

A long column failsby predominant buckling


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2.4.2 Strength of Compression Members in Practice

The highly idealized straight form assumed for the struts considered so far cannot be

achieved in practice. Members are never perfectly straight; they can never be loaded

exactly at the centroid of the cross section. Deviations from the ideal elastic plastic

behaviour defined by Fig. 5 are encountered due to strain hardening at high strains and

the absence of clearly defined yield point. Moreover, residual stresses locked-in during

the process of rolling also provide an added complexity.

Thus the three components, which contribute to a reduction in the actual strength of

columns (compared with the predictions from the ideal column curve) are:

(i) Initial imperfection or initial bow.(ii) Eccentricity of application of loads.

(iii) Residual stresses locked into the cross section.

2.5 Connections

2.5.1 Introduction

Steel sections are manufactured and shipped to some standard lengths, as governed by

rolling, transportation and handling restrictions. However, most of the steel structural

members used in structures have to span great lengths and enclose large three-

dimensional spaces. Hence connections are necessary to synthesize such spatial

structures from one- and two-dimensional elements and also to bring about stability of

structures under different loads. Thus, connections are essential to create an integral

steel structure using discrete linear and two-dimensional (plate) elements.

A structure is only as strong as its weakest link. Unless properly designed, the

connections joining the members may be weaker than the members being joined.However, it is desirable to avoid connection failure before member failure for the

following reasons:

To achieve an economical design, usually it is important that the

connections develop the full strength of the members.

Usually connection failure is not as ductile as that of steel member failure.

Hence it is desirable to avoid connection failure before the member failure.

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Therefore, design of connections is an integral and important part of design of steel

structures. They are also critical components of steel structures, since

They have the potential for greater variability in behaviour and strength,

They are more complex to design than members, and

They are usually the most vulnerable components, failure of which may lead

to the failure of the whole structure.

Thus designing for adequacy in strength, stiffness and ductility of connections will

ensure deflection control during service load and larger deflection and ductile failure

under over-load. Hence, a good understanding of the behaviour and design of joints

and connections in steel structures is an important pre-requisite for any good design

engineer.

2.5.2 Types of Connections

Connections are normally made either by bolting or welding. Bolting is common in

field connections, since it is simple and economical to make. Bolting is also

regarded as being more appropriate in field connections from considerations of

safety. However, welded connections, which are easier to make and are more

efficient, are usually resorted to in shop fabrications.

Two types of bolts are used in bolted connection. The most common type is bearing

bolts in clearance holes, often referred to as ordinary bolts or black bolts. They are

popular since they are economical, both in terms of material and installation costs.

(a) Bearing Connection

(b) Friction Connection

Clamping

Force, P0

XBearing

Stress

Contact

Force, P0

T

T

Frictional

Force T

Fig. 2.12: Bolt Shear Transfer Mechanism

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The main disadvantage of bearing type of bolted connections is that the elements

undergo some slip even under a small shear, before being able to transfer force by

bearing. This is due to clearance between the bolts and the holes. Such a slip causes

increased flexibility in the lower ranges of load and unexpected joint behaviour in somesituations. In such cases high strength friction grip (HSFG) bolts are used.

2.5.3 High Strength Bolts (IS 3757:1985 & IS 4000:1992)

In HSFG bolted joints, high strength bolts (8G or 10K grade) are pre-tensioned against

the plates to be bolted together, and so that contact pressure is developed between the

plates being joined [Fig. 2(b)]. When external shear force is applied, the frictional

resistance to slip between the plates prevents their relative slip. These bolted joints

achieve higher stiffness in shear because of frictional resistance between the contact

surfaces. Only when the externally applied force exceeds the frictional resistance

between the plates, the plates slip and the bolts bear against the bolt holes. Thus even

after slip, there is a reserve strength due to bearing.

The HSFG bolts are expensive both from material and installation points of view. They

require skilled labour and effective supervision. Due to their efficient force transfer

mechanism they have become very popular recently. Moreover, their performance is

superior under cyclic loading compared to other forms of jointing.

High strength bolts are made from bars of medium carbon steel. The bolt of propertyclass 8.8 and 10.9 are commonly used in steel construction. These bolts should confirm

to IS 3757. These bolts are often used with two washers. These washers serve two

purposes:

1. To distribute the clamping pressure to a larger area of softer metal of

fastened parts, and to prevent the nut or bolt head from damaging the

component member.

2. To prevent the threaded portion of the bolt from bearing on connected

member.The strength of high strength bolts are achieved through quenching and tempering

process or low alloying steel. They are less ductile. The materials of bolts do not have a

well defined yield point. Instead of using yield stress, so called proof load is used. The

proof load is obtained by multiplying tensile stress area (may be taken as Area

corresponding to root diameter at thread and in approximately equal to 0.8 times the

shank area of bolt) with proof stress. In IS800, the proof stress is taken as 0.7 times the

ultimate stress of bolt.

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Special techniques are used for tightening the nuts to induce a specified initial tension

in the bolt, which causes the sufficient friction between faying faces. These bolts with

induced initial tension are called High Strength Friction Grip(HSFG) bolts. Due to this

friction, the slip in the joint is eliminated and hence the joints with HSFG bolts are

called non-slip connection or friction type connections. The induced initial tension in

the bolt is called proof-load of the bolt and the coefficient of friction between bolt head

and faying surfaces is called the slip factor.

The sizes of bolt m16 to M36 are available, bolt of sizes M16, M20, M24 & M30 are

commonly used in practice. These bolts are identified by manufacturers identification

symbol and the property class.

Though the material cost of HSFG bolts are about 50% higher than the black bolts andrequire special workmanship for installation, they provided the following advantages:

(a) HSFG bolts do not provide any slip between the elements connected,

especially in close tolerance holes, thus providing the rigid connection.

(b) Due to clamping action, load is transmitted by friction only and bolts are not

subjected to shear and bearing.

(c) Due to smaller number of bolts gusset plate size are reduced.

(d) Deformation is minimized.(e) Since HSFG bolts under working loads do not rely on resistance from

bearing, holes larger than the usual can be provided to ease erection and to

take care of lack of fit. Thus the holes may be standard, extra large, or

short / long slotted. However, the type of holes governs the strength of

connection.

(f) Noiseless fabrication, as bolts are tightened with wrenches.

(g) The possibility of failure at the net section under the working load iseliminated.

(h) Since the loads causing fatigue will be within proof load, the nuts are

prevented from loosening and fatigue strength of joint greater and better

than the welded and riveted joints.

(i) Since the load is transferred by the friction, there is no stress concentration

in holes.

(j) Unlike riveted joints few person are requires for connections.

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(k) No heating is required and no danger of tossing of bolt. Thus the safety of

worker is enhanced.

(l) Alteration, if any (e.g. replacement of the defective bolt) are done easily

than in welded or riveted connections.

2.5.4 Bolt Holes

Bolt holes are usually drilled. Punching can reduce the toughness and ductility and may

lead to brittle fracture. Punched holes should not be used where plastic tensile straining

can occur. IS800 allows punched holes only in materials whose yield stress Fy does not

exceed 360 MPa and where thickness does not exceed (5600/Fy) mm.

Bolt holes are made larger than the bolt diameter to facilitate erection and to allow for

inaccuracies in fabrication. The clearance is 1.0mm for bolts less than 14mm and 2mmfor bolts between 16mm and 24mm and 3mm for bolts exceeding 24mm.

Over size holes and slotted holes are allowable and should not be used often.

A oversize hole should not exceed 1.25d or (d+8) mm in diameter, where d is nominal

bolt diameter in mm. A slotted hole should exceed the appropriate hole size in width

and 1.33d in length, for short slotted hole and 2.5d in length, for long slotted hole.

2.5.5 Spacing and Edge Distance of Bolt Holes

The center- to-center distance between individual fasteners in a line, in the direction ofload or stress is called the Pitch. The distance between any two consecutive fasteners in

a zigzag pattern of bolts measured parallel to the direction of loads/stress is called the

staggered pitch. A minimum spacing of 2.5 times the nominal diameter of fasteners is

specified in the code to ensure that there is sufficient space to tighten the bolts, prevent

the overlapping of the washers and provide adequate resistance to tear-out of bolt.

The distance from the center of fasteners hole to the edge of an element (measured at

right angles to the direction of load) is called the end or edge distance. The edgedistance should be sufficient for bearing capacity and to provide space for bolt head,

washers and nut.

Maximum edge distance = 12t where = (250/y)0.5

Pitch (min.) 2.5 X nominal diameter of bolt

Pitch (max.) 32 t or 300 mm

(a) Parts in tension 16t or 200mm whichever is less

(b) Parts in compression 12t or 200mm whichever is less

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(c) Tacking fasteners 32t or 300mm whichever is less

16t 0r 200mm whichever is less for plates

exposed to weather.

Where t is the thickness of thinner outside plate or angle.

2.5.6 Connection Design Philosophies

Traditional methods of analysis of connection stresses were based on the following

assumptions:

Connected parts are rigid compared to connectors themselves and hence

their deformations may be ignored

Connectors behave in a linear-elastic manner until failure.

Connectors have unlimited ductility.

However, in reality, connected parts such as end plates, angles etc. are flexible and

deform even at low load levels. Further, their behaviour is highly non-linear due to

slip, lack of fit, material non-linearity and residual stresses. Ductility of welds in some

orientation with respect to direction of loads may be very limited, (e.g., Transverse fillet

welds).

Even though truss joints are assumed to be hinged the detailing using gusset plates and

multiple fastener and welding does not represent hinged condition. However, in practicethe secondary moment associated with such a rigid joint is disregarded unless the

loading is cyclic.

The complexity and variability in strength of connections require a rational design

philosophy to account for their behaviour. Keeping in view the large number of joints

to be normally designed in a structure and the considerable variability in the design

strength, any sophisticated analysis is neither desirable nor warranted. The design

should ensure that equilibrium is satisfied, slenderness of the elements is consistentwith the ductility demand and the deleterious effect of stress concentration on fatigue

strength is considered in cyclically loaded structures. The following approach is

consistent with connection design requirements in most general cases encountered in

practice in statically loaded systems.

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The steps to be followed in the proposed rational design approach are enumerated

initially. These are illustrated using a simple framing angle connection between a beam

and a column of a framed building designed to transfer a shear force ofV, as shown in

Fig. 6.

V V

(a) Connection (b) Freebody Diagram

Critical section

for block shear

Fig. 2.13: Simple Framed Angle Shear Connection

2.6 Analysis of Structures

In structural design process term analysis refers to the determination of axial forces

bending moments shear, torsional moments etc acting on different members of astructure due to applied loads and their combination (static or dynamic). In general

design may involve the development of structural layout & system or the arrangement

of different members but for the design engineers, design involves the selection of size

of members to resist the forces and moments determined in analysis phase safely &

economically. In design phase we not only design the members but also their

connections and the foundations. So that the loads are transmitted to the soil.

For statically determinate structures (simply supported beams, cantilevers, trusses

etc.)The analysis is relatively simple & the laws of statistics can be used to determine

the forces & moments on each member. The relative stiffness of intersecting members

does not affect analysis. After analysis is completed and critical moments and forces in

different members are tabulated the design of members are straight forward process

using an appropriate method limit state method etc. For statistically determinate

structure. There is no need for reanalysis or redesign of members.

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However for statistically determinate analysis, the procedure is rather complex. A no. of

analytical methods have been developed which include slope

deflection method, moment distribution method, Kanis method, portal

method etc. In these methods assumptions are usually made regarding

the distribution of applied load among the members according to

relative stiffness of connecting members, the response and behaviour

of members and structures to applied loads, the rigidity of joints etc.

Moreover to perform the analysis, the proportion of various structural

elements should be known in advance for this preliminary design is

generally required. Thus in these types of structure, analysis and

design are interactive process.After the first cycle of analysis has been completed. The members are designed as per

the codal rules-it is usually necessary to re analyze the structure to

check the validity of member sizes. For complex structures several

cycle of analysis and design may be required (many times three cycles

are found to be sufficient). Handbook often provides formulae and

coefficients to simplify the preliminary design of continuous beams or

simple rigid jointed frame such as portal frames.Various computer programs are available for analysis and design of different types of

structure. They include ABACUS, ADINA, ANSYS, ASKA, GT-

STRUDL, SAP and STRESS. The above list is not exhaustive. Many

of these packages were developed for use in mainframe computers.

Recently a number of packages have been developed for use with IBM

PC or compatible systems. Notable among them are SAP 2000,

STAAD III , and STAAD PRO , ETABS , DAST, LARSA, STRAP,RISA 3D, ROBOT Millennium, SPACEGASS, STRUCAD * 3D,GT-

STRUDL and STRUDDS. The windows versions of these packages

are also available. These program are quote general in terms of loading

geometric configuration and support conditions.

With these programs it is now possible to analyze any structure with any complicated

geometry subjected to any pattern of loading (static or dynamic) and

having any boundary conditions or discontinuity.

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However, a structural engineer is often guided in his effort by the code of practice. A

represents the consensus of opinion of experienced engineers and

professionals. The code serves following distinct functions:

1. They ensure adequate structural safety by specifying certain essential

minimum requirements of design.

2. They aid the designer in design process. Often the results of sophisticated

analysis are made available in form of simple formulae or chat.

3. They ensure consistency among different engineers.

4. They protect the structural engineer from disputes, though codes in many

cases do not provide legal protection.

5. In India, the Bureau of Indian standard issues the code and standardhandbooks. Committees, representing procedures, designers, educators,

fabricators, government bodies and other interested bodies write them. The

draft is circulated to a larger section of engineers, designers and

professionals. The committee considers their comments and finally Bureau

of Indian standards print the book.

6. The code depends upon design philosophies. Various design philosophy

have been evolved in different parts of world with regards to structural steeldesign.

7. The earliest codified design philosophy is working stress method of design

(WSM). This method of design is based on linear elastic theory. Now it has

been replaced by limit state design philosophy.

2.6.1 Allowable Stress Design (ASD)

With the development of linear elastic theories in the 19th century the stress-strain

behaviour of new materials like wrought iron & mild steel could be accuratelyrepresented. These theories enabled indeterminate structures to be analysed and the

distribution of bending and shear stresses to be computed correctly. The first attainment

of yield stress of steel was generally taken to be the onset of failure. The limitations due

to non-linearity and buckling were neglected.

The basic form of calculations took the form of verifying that the stresses caused by the

characteristic loads must be less than an allowable stress, which was a fraction of the

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yield stress. Thus the allowable stress may be defined in terms of a factor of safety"

which represented a margin for overload and other unknown factors which

Yield Stress

Allowable Stress Factor of Safety=could be tolerated by the structure. The allowable stress is thus directly related to yield

stress by the followingexpression:

In general, each member in a structure is checked for a number of different

combinations of loading. The value of factor of safety in most cases is taken to be

around 1.67. Many loads vary with time and these should be allowed for. It is

unnecessarily severe to consider the effects of all loads acting simultaneously with their

full design value, while maintaining the same factor of safety or safety factor. Usingthe same factor of safety or safety factor when loads act in combination would result in

uneconomic designs.

A typical example of a set of load combinations is given below, which accounts for the

fact that the dead load, live load and wind load are all unlikely to act on the structure

simultaneously at their maximum values:

(Stress due to dead load + live load) < allowable stress

(Stress due to dead load + wind load) < allowable stress(Stress due to dead load + live load + wind) < 1.33 times allowable stress.

In practice there are severe limitations to this approach. These are the consequences of

material non-linearity, non-linear behaviour of elements in the post-buckled state and

the ability of the steel components to tolerate high theoretical elastic stresses by

yielding locally and redistributing the loads. Moreover the elastic theory does not

readily allow for redistribution of loads from one member to another in statically

indeterminate structures.2.6.2 Limit State Design

Limit States" are the various conditions in which a structure would be considered to

have failed to fulfil the purpose for which it was built. In general two limit states are

considered at the design stage and these are listed in Table 1.

Table 2.7: Limit States

Ultimate Limit State Serviceability Limit State

Strength (yield, buckling) Deflection

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Stability against overturning andsway

Fracture due to fatigue

Brittle Fracture

Vibration

Fatigue checks (including reparable damage due tofatigue)

Corrosion

Ultimate Limit States are those catastrophic states, which require a larger reliability

in order to reduce the probability of its occurrence to a very low level. Serviceability

Limit State" refers to the limits on acceptable performance of the structure.

Not all these limits can be covered by structural calculations. For example, corrosion is

covered by specifying forms of protection (like painting) and brittle fracture is covered

by material specifications, which ensure that steel is sufficiently ductile.

Limit state may be defined as the acceptable limit for the safety and serviceability of

structure before failure occurs. Thus the concept of design with limit state is to achieve

acceptable probabilities so that the structure will not become unfit for use and will not

reach a limit state.

In limit state design are preferred to use the term limit states rather than failure. Thus

limit state is a state of impeding failure beyond which a structure ceases to perform its

intended function satisfactorily. The reliability design is ensured by requirement.

Design action Design strength

The limit states are classified as:

(a) Limit state of strength

(b) Limit state of serviceability

(c) Limit state of strength

The limit state of strength are those associated with failure (or imminent failure), under

the action of probable and most unfavorable combination of loads on structure using

appropriate partial safety factors which may endanger the safety of life and property.

2.6.2.1 Partial Safety Factor

The major innovation in the new codes is the introduction of the partial safety factor

format. A typical format is described below:

In general calculations take the form of verifying that

S* R*

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where S* is the calculated factored load effect on the element (like bending moment,

shear force etc) and R* is the calculated factored resistance of the element being

checked, and is a function of the nominal value of the material yield strength.

S* is a function of the combined effects of factored dead, live and wind loads. (Other

loads if applicable, are also considered)

In accordance with the above concepts, the safety format used in Limit State Codes is

based on probable maximum load and probable minimum strengths, so that a consistent

level of safety is achieved. Thus, the design requirements are expressed as follows:

Sd Rd

where Sd = Design value of internal forces and moments caused by the design Loads,

Fd

Fd = f * Characteristic Loads.

f = a load factor which is determined on probabilistic basis

Rd = Characteristic Value of Resistance/m

Where m = a material factor, which is also determined on a probabilistic basis

It should be noted that f makes allowance for possible deviation of loads and the

reduced possibility of all loads acting together. On the other hand m allows for

uncertainties of element behaviour and possible strength reduction due to

manufacturing tolerances and imperfections in the material.

Collapse is not the only possible failure mode. Excessive deflection, excessive

vibration, fracture etc. also contribute to Limit States. Fatigue is an important design

criterion for bridges, crane girders etc. (These are generally assessed under

serviceability Limit States)

Thus the following limit states may be identified for design purposes:

Ultimate Limit State is related to the maximum design load capacity

under extreme conditions. The partial load factors are chosen to reflect the

probability of extreme conditions, when loads act alone or in combination.

Serviceability Limit State is related to the criteria governing normal use.

Unfactored loads are used to check the adequacy of the structure.

Fatigue Limit State is important where distress to the structure by

repeated loading is a possibility.

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The above limit states are provided in terms of partial factors reflects the severity of the

risks.

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The limit states of strength include:

(i) Loss of equilibrium of structure as a whole or any of its part or

component.

(ii) Loss of stability of structure (including the effect sway) or any of its part

including support & foundation.

(iii) Failures by excessive deformation rupture of structure or any of its parts

or components.

(iv) Fracture due to fatigue

(v) Brittle fracture.

The limit states of serviceability include:

(a) Deformation and deflection which may adversely affect the appearance oreffective use of structure or may cause improper functioning of

equipment or services or may cause damage to finishes & nonstructural

components.

(b) Vibration in structure or any of its components causing discomfort to people

damages to structure, its content or which may limit its functional

effectiveness. Special consideration shall be given to systems

susceptible to vibration such as large open floor area free of partition toensure that such vibrations are acceptable for the intended use and

occupancy.

(c) Repairable damage or crack due to fatigue

(d) Corrosion , durability

(e) Fire

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CHAPTER III

CHOICE OF SECTION

The design of steel sections is governed by the cross sectional area, section modulus,

and radius of gyration. Though IS 808 and IS handbook No.1 list the properties of

various sections, due to the limitations of rolling mills only a few sections are available

in the market. Therefore, design is governed by not only sectional properties but also

the availability of the section. Another factor governing choice is the ease with which

sections can be connected. In India ISMB beams are the most commonly produced? So

are limited numbers of ISHB sections. Also, only medium channels are available. Only

a limited number of unequal angels are available in the market. Also, not all the equal-angel sections are available readily in the market. Hence it will be a good idea to get a

list of the available sections from steel producers like SAIL and plan the design

accordingly.

Though IS 800: 2007 code has removed the minimum thickness requirements, it is

advisable to use a minimum thickness of 6mm for the main members and 5 mm for

secondary members exposed to the atmosphere, especially in coastal areas.

Structural steel is probably the most versatile commonly used structural material. Notonly its versatility apparent in great variety of structures for which it is used but also in

many different forms possible in a single building structure or a complex structure.

Many of the properties of structural steel of interest to the design can be described by

behaviors of steel during simple tension test.

Fig. 3.1: A Channel Section

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A channel section has only an axis of symmetry. Due to this it is subjected to twisting

or torsion along with bending when used as beam.

The various section properties of ISMC 400:

1. Weight = 49.4 Kg/m

2. Sectional Area = 62.93 cm2.

3. Depth of section (h) = 400mm.

4. Width of Flange (b) = 100mm.

5. Thickness of flange (tf) = 15.3mm.

6. Thickness of web (tw) = 8.6mm.

7. Center of gravity (cyy) = 2.42cm.

8. Moment of inertia Ixx = 15082.8cm4, Iyy = 504.8cm4.9. Radius of Gyration rxx = 15.48cm, ryy = 2.83cm.

10.Modulli of section zxx = 754.1cm3, Zyy = 66.6cm3.

11.Radius at root (r1) = 15mm

12.Radius at toe (r2) = 7.5mm.

13.Flange Slope= 60.

14.Section Modulus (Plastic) Zpz = 891.03cm3, Zpy= 127.69cm3.

15. Depth between Root Fillets d = 332.8mm16.Local Buckling Ratios: Flange = 6.5, Web = 38.7, Torsional Constant

Il = 35.33X104 mm4

17.Warping Constant Iw = 152.584 X 109 mm6

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CHAPTER IV

GENERAL STATEMENT FOR STAAD

STAAD.Pro V8i is the most popular structural engineering software product for 3D

model generation, analysis and multi-material design. It has an intuitive, user-friendly

GUI, visualization tools, powerful analysis and design facilities and seamless

integration to several other modeling and design software products. The software is

fully compatible with all Windows operating systems but is optimized for

Windows XP.

For static or dynamic analysis of bridges, containment structures, embedded structures

(tunnels and culverts), pipe racks, steel, concrete, aluminum or timber buildings,transmission towers, stadiums or any other simple or complex structure, STAAD.Pro

has been the choice of design professionals around the world for their specific analysis

needs.

STAAD.Pro is a general purpose program for performing the analysis and design of a

wide variety of types of structures. The basic three activities which are to be carried out

to achieve that goal:

(a) Model generation(b) The calculations to obtain the analytical results

(c) Result verification - are all facilitated by tools contained in the program's

graphical environment.

The design philosophy and procedural logistics for member selection and code

checking are based upon the principles of allowable stress design. Two major failure

modes are recognized: failure by overstressing, and failure by stability considerations.

The flowing sections describe the salient features of the allowable stresses beingcalculated and the stability criteria being used. Members are proportioned to resist the

design loads without exceeding the allowable stresses and the most economic section is

selected on the basis of least weight criteria. The code checking part of the program

checks stability and strength requirements and reports the critical loading condition and

the governing code criteria. It is generally assumed that the user will take care of the

detailing requirements like provision of stiffeners and check the local effects such as

flange buckling and web crippling.

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4.1 Technical Reference

Input Generation: The GUI (or user) communicates with the STAAD analysis engine

through the STD input file. That input file is a text file consisting of a series of

commands which are executed sequentially. The commands contain either instructions

or data pertaining to analysis and / or design.

Types of Structures: A STRUCTURE can be defined as an assemblage of elements.

STAAD is capable of analyzing and designing structures consisting of both frame,

plate/shell and solid elements. Almost any type of structure can be analyzed by

STAAD.

A SPACE structure, which is a three dimensional framed structure with loads applied

in any plane, is the most general.A PLANE structure is bound by a global X-Y coordinate system with loads in the same

plane.

A TRUSS structure consists of truss members who can have only axial member forces

and no bending in the members.

A FLOOR structure is a two or three dimensional structure having no horizontal

(global X or Z) movement of the structure [FX, FZ & MY are restrained at every joint].

The floor framing (in global X-Z plane) of a building is an ideal example of a FLOORstructure. Columns can also be modeled with the floor in a FLOOR structure as long as

the structure has no horizontal loading. If there is any horizontal load, it must be

analyzed as a SPACE structure.

Specification of the correct structure type reduces the number of equations to be solved

during the analysis. This results in a faster and more economic solution for the user.

Unit Systems: The user is allowed to input data and request output in almost all

commonly used engineering unit systems including MKS, SI and FPS. In the input file,the user may change units as many times as required. Mix and match between length

and force units from different unit systems is also allowed. The input-unit for angles (or

rotations) is degrees. However, in JOINT DISPLACEMENT output, the rotations are

provided in radians. For all output, the units are clearly specified by the program.

Structure Geometry and Coordinate Systems: A structure is an assembly of

individual components such as beams, columns, slabs, plates etc. In STAAD, frame

elements and plate elements may be used to model the structural components.

Typically, modeling of the structure geometry consists of two steps:

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Fig. 4.1: Cartesian (Rectangular) Coordinate System

Fig. 4.2: Cylindrical Coordinate System

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Fig. 4.3: Reverse Cylindrical Coordinate System

Local Coordinate System: A local coordinate system is associated with each member.

Each axis of the local orthogonal coordinate system is also based on the right hand rule.

Fig. 1.5 shows a beam member with start joint 'i' and end joint 'j'. The positive direction

of the local x-axis is determined by joining 'i' to 'j' and projecting it in the same

direction. The right hand rule may be applied to obtain the positive directions of the

local y and z axes. The local y and z-axes coincide with the axes of the two principal

moments of inertia. Note that the local coordinate system is always rectangular.

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Fig. 4.4: When Global-Y is vertical

Fig. 4.5: When Global-Z is vertical

A wide range of cross-sectional shapes may be specified for analysis. These include

rolled steel shapes, user specified prismatic shapes etc. Fig. 1.6 shows local axis

system(s) for these shapes.

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Relationship between Global & Local Coordinates: Since the input for member

loads can be provided in the local and global coordinate system and the output for

member-end-forces is printed in the local coordinate system, it is important to know the

relationship between the local and global coordinate systems. This relationship is

defined by an angle measured in the following specified way. This angle will be defined

as theBeta Angle.

Beta Angle: When the local x-axis is parallel to the global Vertical axis, as in the case

of a column in a structure, the beta angle is the angle through which the local z-axis (or

local Y for SET Z UP) has been rotated about the local x-axis from a position of being

parallel and in the same positive direction of the global Z-axis (global Y axis for SET Z

UP).

When the local x-axis is not parallel to the global Vertical axis, the beta angle is the

angle through which the local coordinate system has been rotated about the local

x-axis from a position of having the local z-axis (or local Y for SET Z UP) parallel to

the global X-Z plane (or global X-Y plane for SET Z UP)and the local y-axis (or local z

for SET Z UP) in the same positive direction as the global vertical axis. Figure 1.7

details the positions for beta equals 0 degrees or 90 degrees. When providing member

loads in the local member axis, it is helpful to refer to this figure for a quick

determination of the local axis system.Reference Point: An alternative to providing the member orientation is to input the

coordinates (or a joint number) which will be a reference point located in the member

x-y plane (x-z plane for SET Z UP) but not on the axis of the member. From the

location of the reference point, the program automatically calculates the orientation of

the member x-y plane (x-z plane for SET Z UP).

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Fig. 4.6: Relationship between Global and Local axes

Loads: Loads in a structure can be specified as joint load, member load, temperature

load and fixed-end member load. STAAD can also generate the self-weight of the

structure and use it as uniformly distributed member loads in analysis. Any fraction of

this self-weight can also be applied in any desired direction.

Joint Load: Joint loads, both forces and moments, may be applied to any free joint of a

structure. These loads act in the global coordinate system of the structure. Positive

forces act in the positive coordinate directions. Any number of loads may be applied ona single joint, in which case the loads will be additive on that joint.

Member Load: Three types of member loads may be applied directly to a member of a

structure. These loads are uniformly distributed loads, concentrated loads, and linearly

varying loads (including trapezoidal). Uniform loads act on the full or partial length of a

member. Concentrated loads act at any intermediate, specified point. Linearly varying

loads act over the full length of a member. Trapezoidal linearly varying loads act over

the full or partial length of a member. Trapezoidal loads are converted into a uniform

load and several concentrated loads.

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Any number of loads may be specified to act upon a member in any independent

loading condition. Member loads can be specified in the member coordinate system or

the global coordinate system. Uniformly distributed member loads provided in the

global coordinate system may be specified to act along the full or projected member

length. Refer to Fig. 1.3 to find the relation of the member to the global coordinate

systems for specifying member loads. Positive forces act in the positive coordinate

directions, local or global, as the case may be.

Area / One-way Load / Floor Load: Often a floor is subjected to a uniform pressure.

It could require a lot of work to calculate the equivalent member load for individual

members in that floor. However, with the AREA, ONEWAY or FLOOR LOAD

facilities, the user can specify the pressure (load per unit square area). The program willcalculate the tributary area for these members and calculate the appropriate member

loads. The Area Load and One way load are used for one way distribution and the Floor

Load is used for two way distribution.

The following assumptions are made while transferring the area/floor load to member

load:

(a) The member load is assumed to be a linearly varying load for which the

start and the end values may be of different magnitude.(b) Tributary area of a member with an area load is calculated based on half the

spacing to the nearest approximately parallel members on both sides. If the

spacing is more than or equal to the length of the member, the area load will

be ignored.

(c) Area / Floor load should not be specified on members declared as

MEMBER CABLE, MEMBER TRUSS, MEMBER TENSION or

MEMBER COMPRESSION or CURVED.Fixed End Member Load: Load effects on a member may also be specified in terms of

its fixed end loads. These loads are given in terms of the member coordinate system and

the directions are opposite to the actual load on the member. Each end of a member can

have six forces: axial; shear y; shear z; torsion; moment y, and

moment z.

Prestress and Post stress Member Load: Members in a structure may be subjected to

prestress load for which the load distribution in the structure may be investigated. The

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prestressing load in a member may be applied axially or eccentrically. The

eccentricities can be provided at the start joint, at the middle, and at the end joint. These

eccentricities are only in the local y-axis. A positive eccentricity will be in the positive

local y-direction. Since eccentricities are only provided in the local y-axis, care should

be taken when providing prismatic properties or in specifying the correct BETA angle

when rotating the member coordinates, if necessary. Two types of prestress load

specification are available; PRESTRESS, where the effects of the load are transmitted

to the rest of the structure, and POSTSTRESS, where the effects of the load are

experienced exclusively by the members on which it is applied.

Temperature and Strain Load: Temperature difference through the length of a

member as well as differences of both faces of members and elements may also bespecified. The program calculates the axial strain (elongation and shrinkage) due to the

temperature difference. From this it calculates the induced forces in the member and the

analysis is done accordingly. The strain intervals of elongation and shrinkage can be

input directly.

Support Displacement Load: Static Loads can be applied to the structure in terms of

the displacement of the supports. Displacement can be translational or rotational.

Translational displacements are provided in the specified length while the rotationaldisplacements are always in degrees. Note that displacements can be specified only in

directions in which the support has an "enforced" specification in the Support

command.

Steel Design Consideration As Per IS800 in STAAD: In STAAD implementation of

IS:800, the user is allowed complete control of the design process through the use of

design parameters. Available design parameters to be used in conjunction with IS:800.

Stability Requirements: Slenderness ratios are calculated for all members and checkedagainst the appropriate maximum values. Section 3.7 of IS:800 summarizes the

maximum slenderness ratios for different types of members. In STAAD implementation

of IS:800, appropriate maximum slenderness ratio can be provided for each member. If

no maximum slenderness ratio is provided, compression members will be checked

against a maximum value of 180 and tension members will be checked against a

maximum value of 400.

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Truss Members: As mentioned earlier, a truss member is capable of carrying only

axial forces. So in design no time is wasted in calculating bending or shear stresses,

thus reducing design time considerably. Therefore, if there is any truss member in an

analysis (like bracing or strut, etc.), it is wise to declare it as a truss member rather than

as a regular frame member with both ends pinned.

Deflection Check: This facility allows the user to consider deflection as criteria in the

check code and member selection processes. Note that deflection is used in addition to

other strength and stability related criteria. The local deflection calculation is based on

the latest analysis results.

The purpose of code checking is to verify whether the specified section is capable ofsatisfying applicable design code requirements. The code checking is based on the

IS:800 (1984) requirements. Forces and moments at specified sections of the members

are utilized for the code checking calculations. Sections may be specified using the

BEAM parameter or the SECTION command. If no sections are specified, the code

checking is based on forces and moments at the member ends.

The code checking output labels the members as PASSed or FAILed. In addition, the

critical condition (applicable IS:800 clause no.), governing load case, location (distancefrom the start) and magnitudes of the governing forces and moments are also printed

out.

Code Checking: The purpose of code checking is to verify whether the specified

section is capable of satisfying applicable design code requirements. The code checking

is based on the IS:800 (1984) requirements. Forces and moments at specified sections

of the members are utilized for the code checking calculations. Sections may be

specified using the BEAM parameter or the SECTION command. If no sections are

specified, the code checking is based on forces and moments at the member ends.

The code checking output labels the members as PASSed or FAILed. In addition, the

critical condition (applicable IS: 800 clause no.), governing load case, location

(distance from the start) and magnitudes of the governing forces and moments are also

printed out.

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Member Selection: STAAD is capable of performing design operations on specified

members. Once an analysis has been performed, the program can select the most

economical section that is the lightest section, which satisfies the applicable code

requirements. The section selected will be of the same type (I-Section, Channel etc.) as

originally specified by the user. Member selection may be performed with all types of

steel sections listed in Section 7B.13 and user provided tables. Selection of members,

whose properties are originally provided from user specified table, will be limited to

sections in the user provided table. Member selection can not be performed on members

whose cross sectional properties are specified as PRISMATIC.

Member Selection by Optimization: Steel section selection of the entire structure may

be optimized. The optimization method utilizes a state-of-the -art numerical techniquewhich requires automatic multiple analysis. The user may start without a specifically

designated section. However, the section profile type (BEAM, COLUMN, CHANNEL,

ANGLE etc.) must be specified using the ASSIGN command (see Chapter 6). The

optimization is based on member stiffness contributions and corresponding force

distributions. An optimum member size is determined through successive

analysis/design iterations. This method requires substantial computer time and hence

should be used with cautionCombined Stress: Members subjected to both axial and bending stresses are

proportioned accordingly to section 7 of IS: 800. All members subject to bending and

axial compression are required to satisfy the equation of Section 7.1.1 (a) for

intermediate points, and equation of Section 7.1.1 (b) for support points.

For combined axial tension and bending the equation of Section 7.1.2 is required to be

satisfied.

Cm coefficients are calculated according to the specifications of Section 7.1.3information regarding occurrence of sides way can be provided through the use of

parameters SSY and SSZ. In the absence of any user provided information, sides way

will be assumed.

Shear Stress: Allowable shear stress calculations are based on Section 6.4 of IS: 800.

For shear on the web, the gross sections taken into consideration consist of the product

of the total depth and the web thickness. For shear parallel to the flanges, the gross

section is taken as 2/3 times the total flange area.

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Column with Lacings and Battens: For columns with large loads it is desirable tobuild rolled sections at a distance and inter-connect them. The joining of elementsections is done by two ways:

(a) Lacing and(b) Batten

Double channel sections (back-to-back and face-to-face) can be joined either by lacingor by batten plates having riveted or welded connection.

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CHAPTER V

RESULTS AND CALCULATIONS

5.1 Analysis for 5.0m span with load acting at center

Fig. 5.1: 5.0m span with load acting at center

Table 5.1: Steel Design Table from STAAD (All Units are - KN METER)

Member Table Result / FXCriticalCond./

MY

Ratio/ MZLoading /

Location

1 ST ISMC400 (Indian Sections)

PASS IS-7.1.1(A) 0.790 3

74.59 C 0.00 -71.66 0.00

2 ST ISMC400 (INDIAN SECTIONS)

PASS IS-7.1.1(A) 0.790 3

74.59 C 0.00 -71.66 0.00


PASS IS-7.1.1(A) 0.651 3

41.16 C 0.00 71.66 0.00

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PASS IS-7.1.1(A) 0.996 3

41.16 C 0.00 -112.74 1.25


PASS IS-7.1.1(A) 0.996 3

41.16 C 0.00 -112.74 1.25


PASS IS-7.1.1(A) 0.651 341.16 C 0.00 71.66 1.25


PASS SHEAR-Y 0.000 1

0.00 T 0.00 0.00 0.00


PASS IS-7.1.1(A) 0.790 3

74.59 C 0.00 71.66 0.00


PASS IS-7.1.1(A) 0.790 3

74.59 C 0.00 71.66 0.00


PASS IS-7.1.1(A) 0.651 3

41.16 C 0.00 71.66 0.00


PASS IS-7.1.1(A) 0.996 3

41.16 C 0.00 -112.74 1.25

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PASS IS-7.1.1(A) 0.996 3

41.16 C 0.00 -112.74 0.00


PASS IS-7.1.1(A) 0.651 3

41.16 C 0.00 71.66 1.25



0.00 T 0.00 0.00 0.00



0.00 T 0.00 0.00 0.00


PASS SHEAR-Y 0.000 10.00 T 0.00 0.00 0.00



0.00 T 0.00 0.00 0.00


PASS IS-7.1.1(A) 0.207 3

77.08 C 0.00 15.42 0.50


PASS IS-7.1.1(A) 0.207 3

77.08 C 0.00 15.42 0.50

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PASS IS-7.1.1(A) 0.207 3

77.08 C 0.00 -15.42 0.50


PASS IS-7.1.1(A) 0.207 3

77.08 C 0.00 -15.42 0.50


PASS IS-7.1.2 0.068 3

35.55 T 0.00 3.81 0.00


PASS IS-7.1.2 0.068 3

35.55 T 0.00 3.81 0.00

5.2 For load acting at center

Fig. 5.2: Variation of Maximum load with respect to different span

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Table 5.2: Following Listed Below Table Shows the values of Fx, Fy and Mz at nodes 1,4,6&8 when

load is acting at center

Table 5.2.1: Analysis for 4.0m span with load acting at center

Node L/C Fx kN Fy kN Fz kN Mx kN-m My kN-m Mz kN-m

1 3 Combination Load Case 3 2.309 94.094 0 0 0 -13.359

4 3 Combination Load Case 3 -2.309 94.093 0 0 0 13.359





















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6 3 Combination Load Case 3 4.297 82.884 0 0 0 -14.6228 3 Combination Load Case 3 -4.297 82.884 0 0 0 14.622











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4 3 Combination Load Case 3 -5.61177.07

7 0 0 0 15.415



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Fig. 5.3: Variation of fxwith respect to different span

Fig. 5.4: Variation of fy with respect to different span

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Fig. 5.5: Variation of MZwith respect to different span

In order to check the adequacy of the actual existing frame we are designing this section

with the help of STAAD-Pro.V8i and this results are checked manually by analyzing

this frame section with moment distribution method further it is checked by IS Code

method.

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For 5 m span: load acting at center :

Table 5.3: Distribution Factors

Joint Member k Sum DF

B BA I / 0.5 1 / 1.33

BC I / 2.14 2.667 I 1 / 5.71

BE I / 5 1 / 13.33

C CD I / 5 0.667 I 1 / 1.33

CB I / 2.14 1 / 1.43

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Table 5.4: Moment Distribution table For load acting at center

57

A B C D E F

AB BA BE BC CB CD DC DE ED EB EF FE

1

1.33

1

13.33

1

5.71

1

1.43

1

3.33

1

3.33

1

1.43

1

5.71

1

13.33

1

1.33

-91.25 +91.25 FEM

+63.81 +27.40 -27.40 -63.81 Bal

+31.91 -13.7 +13.7 -31.91 Co

-24.00 -2.39 -5.59 +9.58 +4.11 -4.11 -9.58 +5.59 +2.39 +0.24 Bal

-12 +1.19 +4.79 -2.79 -2.05 +2.05 +2.79 -4.79 -1.19 +12 Co

-4.50 -0.448 -1.05 +3.38 +1.45 -1.45 -3.38 +1.05 +0.448 +4.50 Bal

-0.72 +0.072 +0.07 -0.168 -0.03 +0.03 +0.168 -0.07 -0.072 +0.72 Co

-0.053 -0.107 -0.011 -0.025 +0.138 +0.059 -0.059 -0.138 +0.025 +0.011 +0.107 +0.053 Bal Co

-15.023 -30.047 -1.507 +31.46 +73.565 -74.676 +74.676 -73.565 -31.46 +1.507 +30.047 +15.023


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Fixed End Moments:

145 591.25 kN

8 8

FCD

wlM

= = =

146 591.25 kN

8 8FDC

wlM

+ = + = = +

15.023ABM = 73.565CBM = +

30.047BAM = 74.66CDM =

1.507BEM = 74.676DCM =

31.46BCM=

73.56DEM=

31.46EDM =

1.567EBM = +

30.047EFM =

15.023FEM = +

l = 2.14 m

For Load acting at centre: Taking the section ISMC400 @ 49.4 kg / m,

A = 6293 mm2; h = 400 mm; b = 100 mm

tf= 15.3 mm; tw = 8.6 mm; rx = 154.8 mm

ry = 28.3 mm; 3 3754.1 10 mmxxZ =

1 2 400 2 15.3 369.4 mmfd h t= = =

1. Determination of ac

214075.62

28.3y

l

r = = = N/mm2

From Table 5.1 of IS 800 : 1984 2105.82 mmac =

2. Determination of bc

15.31.78 2

8.6f

w

tT

t t= = =

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