10

CHAPTER 2

LITERATURE REVIEW

2.0 PREVIOUS HISTORY OF COMPOSITE CONSTRUCTION

Composite construction as we know it today was first used in both a building and a bridge in

U.S. over a century ago. The first forms of composite structures incorporated the use of steel and

concrete for flexural members, and the issue of longitudinal slip between these elements was

soon identified.

Composite steel–concrete beams are the earliest form of the composite construction method. In

U.S. a patent by an American engineer was developed for the shear connectors at the top flange

of a universal steel section to prevent longitudinal slip. This was the beginning of the

development of fully composite systems in steel and concrete. Concrete-encased steel sections

were initially developed in order to overcome the problem of fire resistance and to ensure that

the stability of the steel section was maintained throughout loading. The steel section and

concrete act compositely to resist axial force and bending moments.

A composite tubular column was developed because they provided permanent and integral

formwork for a compression member and were instrumental in reducing construction time and

consequently costs. They reduce the requirement of lateral reinforcement and costly tying, as

well as provide easier connection to steel beams of a framed structure.

Composite slabs have been introduced recently to consider the increase in strength that can be

achieved if the profiled steel sheeting is taken into account in strength calculations. Composite

slabs provide permanent and integral reinforcement, which eliminates the need for placing and

stripping of plywood and timber formwork. More recently, composite slab and beam systems

have been developed for reinforced concrete framed construction; this provides advantages

similar to those attributed to composite slabs for reinforced concrete slab and beam systems.

These advantages include reduced construction time due to elimination of formwork and

elimination of excessive amounts of reinforcing steel. This subsequently reduces the span-to-

depth ratios of typical beams and also reduces labour costs.

11

Fig. 2.1 Composite Steel–Concrete Beams and Slabs, Car Park, Australia

The application of profiled steel sheeting as both permanent formwork and reinforcement to

concrete slabs was first developed in America in the early 1950s. Following its introduction into

the United Kingdom in the 1970s it has become the most common form of floor system for steel

framed office buildings. In Australia, in the early 1990’s much research was carried out using the

same construction technique in beams also. In this chapter, a thorough review is given of

research into composite construction, including beams, slab with steel decking and profiled

composite beams.

2.1 STUDIES ON COMPOSITE CONSTRUCTION

Tests on steel concrete composite beams were reported since early 19th century itself. Many

aspects of composite structural interaction between steel beams and concrete have been studied

and reported in Canada and elsewhere as early as 1922. These studies relate to the behaviour of

12

conventional concrete slab over steel I – beam. Such tests are not considered here for the review.

The tests reported below include information on the composite beams and slabs which use stay-

in-place form.

Concrete frame construction has until recently been traditionally undertaken using plywood

formwork for all structural elements and so no inherent advantages have been achievable during

the construction phase. This has been overcome by the development of composite profiled

beams which employ a permanent formwork system consisting of profiled sheeting for concrete

framed construction.

Chapman.J.C. and Balakrishnan S. (1964)9 earlier investigations started with well known work

on composite beams by the authors who concerned about the shear connectors in the

overhanging region of the simply supported composite beams. They aimed at the sensitivity of

the overall response of the beams with respect to the material strength.

Chapman.J.C.and Yam.L.C.P. (1968)10

presented an iterative numerical model for the inelastic

analysis of simply supported composite beams. The inelasticity of steel concrete and shear

connectors was taken into account for the analysis.

Johnson R.P (1975)29

the initiative for composite construction started by the extensive research

by Dr Chapman and Professor Johnson R, P led to publish a book with a review of behaviour of

composite structure of steel and concrete. In his book he drafted design methods for composite

structures for both building and bridges

Reinhold M.Schuster (1976)40

Reviewed different papers on composite steel deck reinforced

slabs, which are presented by many authors. After the review, R.M.Schuster, mentioned the

various commercially available steel decks and classified them based on their means of

developing shear resistance and on the pattern of mechanical shear transfer devices into three

categories of the decks namely

Steel deck profiles that provide horizontal shear capacity primarily by virtue of

Mechanical shear devices

Steel deck profiles that have a variable spacing of mechanical devices

Steel deck profiles that have no mechanical shear devices

13

The author also reported the advantages and possible disadvantages. Even though this paper

dealt with the composite slabs, it was considered as a primary literature for steel concrete

composite systems.

Max L. Porter and Carl. E. Ekberg (1976)33

explained cold formed steel deck sections used in

composite floor slabs. During the construction phase, the steel deck serves as the structural load

carrying element. Design procedures were recommended for composite steel deck-reinforced

floor by utilizing the application of the maximum strength concepts. The design capacity

primarily is based upon the computation of shear bond strength. However the equation for

flexural capacities is also developed from the compatibility of strains and the equilibrium of

internal forces. Additional design considerations are given on casting and shoring requirements,

deflections and span/depth relations.

Deflection limitations follow the provisions of Section 9.5 of the ACI building code. The

recommended effective moment of inertia for composite deck deflection limitations is taken as

simply the average of the standard cracked and uncracked sections.

Singh.R.K. and Mallick. S.K. (1977)43

conducted experiments on 8 composite beams. Four of

them were tested for pure torsion and another four tested for the combination of flexure and

torsion. They presented a formula to find the ultimate torsional strength of the composite beams.

The formula presented was:

Tu = Tcu+Tr+Tj where Tcu, Tr and Tj were the torsional strength contribution by concrete,

reinforcement and joist respectively.

Ray, M.B., and Mallick, S.K. (1980)38

the results of tests on five composite beams, tested to

destruction under combined flexure and torsion, are discussed with reference to earlier published

data1'2. In the tests, the ratios between the bending and torsional moments were maintained

constant. Tri ultimate strengths of the reinforced concrete slab and composite beam are assessed

from tests carried out in simple torsion.

Ansourian.P. (1981)1 six continuous composite beams with compact steel section were tested.

Two beams had limited rotation capacity and were tested under severe sagging rotation

conditions; the other 4 were loaded symmetrically and included cases where local buckling

14

contributed to failure. It is proposed that beams having ductility parameter X greater than 1:4 can

be designed using simple plastic theory, without regard to loading and span configuration. An

assessment is made of the vertical shear resistance of the slab at the interior supports. It is

concluded that simple plastic design incorporating full plastic moment values may be confidently

used in continuous composite beams having compact steel section, adequate slab and shear

connection, even under conditions of severe rotation requirement.

George Abdel – Sayed (198219

is one of the earliest investigators who used stay-in-place form

for beam construction. The test specimens utilized cold formed steel stiffened channels as part

of the side formwork as well as reinforcement replacing conventional steel bars. Soffits made in

the form of stiffened channels with embossments, performed very well as integral parts of the

composite beam. The combined action of the embossments and the stiffening lead to excellent

bond characteristics between the soffit and the concrete.

The author concludes that replacing the standard reinforcing bars by a cold formed steel section

the structural performance of the beam is unchanged, while saving is achieved in the cost of

forms and shoring.

As per author’s investigations, the beams suggested used the stay-in form only for some portion

of the depth. He suggested removable formwork for the remaining part. This did not result in

full economy of formwork. Furthermore, no significant analytical work was undertaken.

Max L. Porter (1988)34

proposed design criteria for composite steel deck slabs based on

experiments. The author recommended design procedures by utilizing the maximum strength

concepts. For the slabs failing in shear bond failure mode, A plot was made using the

parameters, Vu / bd√fc’, as ordinates and ρd/L’√fc’ as abscissa. A linear regression is then

performed to determine the slope (m) and the intercept (k), in order to provide an equation for

the expected shear capacity.

''

fckL

dm

bd

Vu

Where Vu = Ultimate shear capacity

ρ = reinforcement ratio (As/bd)

15

d = effective depth from the compression fibre to steel deck centroid

fc’ = design concrete compressive strength

For flexure the author suggested separate computations for under reinforced and over reinforced

sections. An effective composite moment of inertia for deflection is taken as a simple average of

the composite moments of inertia of cracked and uncracked sections.

Richard P. Nguyen (1991)41

studied the feasibility of using cold-formed steel channels as

reinforcement for cast-in-place concrete beams. His experimental investigation included 32

beam specimens made of thin-walled, cold-formed steel stiffened channels and concrete

subjected to shear and bending both individually and combined.

From the test results, the authors concluded that, the composite beams developed the same

ultimate strength in bending and shear as conventional RCC beams in addition to economy and

speedy construction. The author has also suggested empirical formulae for predicting the

ultimate bending capacity, shear bond capacity and the combined bending and shear stresses.

Since the conclusions were based on brief test results the author has suggested further study for

checking the reliability of the conclusions. No analytical model was proposed by the author to

quantify the increasing deflection and ductility characteristics.

Deric John Oehlers (1993)13

proposed significant work using profiled sheeting. He performed

an experimental investigation on the strength of composite profiled beams. The author used the

steel profiled sheets as permanent formwork to the sides and bottom of reinforced concrete

beams. Experimental tests on large scale beams by the author showed that the addition of

profiled steel sheets to the sides of RCC beams substantially increases both their flexural and

shear strengths without loss of ductility and that this system is not prone to shear bond failure at

the profiled sheet - concrete interface. The composite strength of the profiled beams depended

primarily on forces normal to the ribs in the side of profiled steel sheets. These normal forces

are induced by the mechanical actions from flexural and shear displacements. Of secondary

importance are the shear bond forces, which only increased the strength slightly. Furthermore,

from theoretical studies the author suggested that the addition of side – profiled sheets

substantially reduce the long term deflections due to creep and shrinkage of the concrete and the

span/depth ratio is increased by about 20% since the depth of the beam is reduced.

16

The author also concluded that the addition of side profiled sheets to the sides of reinforced

concrete beam increased the shear strength and shear ductility. Profiled beams of the same

flexural strength as reinforced concrete beams have a larger shear capacity, and this may allow

reduction in the amount of stirrups required.

Brian. Uy and M.A. Bradford (1993)5 conducted service load tests on profiled composite and

reinforced concrete beams. Tests are reported on two profiled composite steel-concrete beams

and two reinforced concrete beams of the same flexural strength as the profiled beams under

service loads. The beams were monitored under sustained loading for a period of approximately

250 days. Time-dependent deflections and strains in the beams were measured over this period,

as well as the creep co-efficient and shrinkage strains on companion specimens. The results

showed that the time dependent deformations of the profiled composite steel-concrete beams are

significantly less than those of the reinforced concrete beams. The test results are intended to

provide benchmark data for validating theoretical predictions of the deformations of profiled

composite beams under service-load conditions.

Deric J. Oehlers, Howard D. Wright and J. Burnet (1994)14

reported a construction technique

that uses steel decking as permanent and integral shuttering for the sides and soffits of reinforced

concrete beams. The authors conducted experiments on large-scale profiled beams. The authors

predicted that the behaviour of this form of composite construction can be affected by local

buckling of the steel decking and the strength of the shear bond at the interface between the

decking and concrete. Simple design procedures are developed to prevent local buckling of the

steel decking before the ultimate strength of the beam is reached. A new procedure based on

rigid plastic analysis has been derived for determining the flexural strength of composite profiled

beams.

Brian Uy and Mark Andrew Bradford (1995)6

Conducted experiments on ductility of profiled

composite beams. The authors adopted cold-formed profiled steel sheeting as stay-in-place form

for reinforced concrete beam and referred them as Profiled Composite Beams. The study

includes two profiled composite beams and two reinforced concrete beams. All beams were 6m

in length with their cross sections being 290 x 400 mm for profiled beams and 265 x 400mm for

RCC beams. The beams were tested to failure in flexure. Load strain characteristics were

measured for the beams, from which moment – curvature response was obtained. The test

17

results were used to ascertain the flexural strength of the beams and to validate the hypotheses of

the previously reported service load tests. The measured flexural strength of the two profiled

composite and two reinforced concrete beams has been shown to be of the same magnitude.

Thus the authors demonstrated that profiled composite beams are advantageous over reinforced

concrete beams of the same strength for serviceability and long term effects.

Failure is shown to occur progressively through a combination of bond-slip failure and local

buckling of the steel sheeting. Tests highlighted the improved ductility of profiled beams over

reinforced concrete beams. The test results are then used to calibrate a theoretical model for the

cross sectional behaviour of profiled composite beams. Local buckling predicted by the use of a

finite strip method developed elsewhere was found in agreement with the experiments.

Ductility has been identified from moment – curvature plot. However no analytical model was

proposed to quantify the ductility.

Brian Uy and Mark Andrew Bradford (1995)7 investigated an analytical model which is

developed based on the routine mechanics of the materials to study the moment – curvature

response and hence the ductility of a profiled composite beam. The material nonlinearities of the

cold-formed steel and concrete are used to determine an accurate description of the moment-

curvature response. Parametric studies are made on the influence of material strengths and

various cross-section geometries. A numeric integration approach was adopted for the study.

The beam cross section used for the parametric study was 250 x 450mm. From the parametric

study it is understood that the yield stress of the sheeting, area of tension reinforcement and

interfacial slip affected the ductility. The model was shown to agree well for both the linear and

nonlinear ranges of loading. The authors explained that numerical model was applied to a

specific cross section, but the results are general for any cross section.

Ramajeyam.I and Swamidura.A (1997)39

reported on the behaviour of concrete in filled cold

formed steel tubular columns stiffened with weld-mesh. The aim of the investigation is to study

the effect of confinement of concrete in cold formed steel concrete composite columns with

respect to strength and stiffness by conducting experiments on the different types of concrete in

filled cold formed steel tubular columns and cold formed steel hollow columns.

18

From the experimental results, the authors concluded that concrete in filled cold formed steel

columns stiffened with weld mesh showed large enhancement of load carrying capacity as

compared to cold formed hollow steel column without infill and can sustain large strains and

deformations. This reserve strength and deformation make them as ideal structural elements in

predicting the theoretical ultimate loads of column which agrees fairly well with results. The

provision of weld mesh stiffness in the columns which improved the bond between concrete and

steel shell has resulted in enhanced ultimate load, ductility and stiffness.

Khandaker M. Anwar Hossain (2003)30

utilized cold formed steel elements for his beam

construction and referred the beam as thin walled Composite (TWC) filled beam. The behaviour

of TWC filled beams with normal and light weight volcanic pumice concrete as infill is reported

from a series of experiments. The performance of the beams with various interface connections

was studied. The strength and failure modes of beams are found to depend on the interface

connections. The effect of various modes of interface connections are co-related to the

generation of shear bond between sheeting and concrete using both experimental and theoretical

results. 24 beams were cast and tested to study the performance of different TWC beams.

The author observed from the test results that the strength of the beams is limited by the

compression buckling capacity of the steel plate at the top of the open box cross section. Further

concluded that the enhancement of the strength can be possible by stiffening the compression

steel plates at the open end of box cross section of various modes interface connections.

Analytical models for the design of beams are developed which are based on the models

proposed by Oehler’s.13

. Their performance is validated through experimental results using both

full and partial shear connection. The effect of interface shear bond has been studied by varying

the shear bond stress. The typical effect of this bond stress on strength and the value of concrete

and sheet neutral axis are also presented. Appropriate design recommendations and practical

design charts have been developed by the author so that the designer can check whether the

strength will be governed by buckling or yielding of steel and are able to design the beam

accordingly. For the safe design of TWC beams, guidelines are proposed in using analytical

models.

This work is related significantly to this thesis work. But the beams cast for the investigation

consists of span 600mm, 990mm and 1500mm, from which a real behaviour cannot be judged.

19

Except the beam series which had welded braces, others had separation of sheet from concrete.

Hence the author commented that “the braces are essential to avoid separation”.

Slobodan Rankovic And Dragoljub Drenic (2002)44

reviewed the most important analytic

expressions, on the basis of the developed industrial countries contemporary literature, for

determination of strength of shear connectors in steel-concrete composite beams the mechanism

of possible failure and the basic criteria used for defining of the shear connector strength at

composite slabs and composite slabs with profiled sheet. Special analysis has been done in the

expressions and the recommendations given by European 4 in the area of shear connector

strength, both elastic and rigid. Along with the comparative review of the regulation, a

commentary on the strength of the shear connectors in composite beams was given.

Shun-Ichi Nakamura, P.E, (2002)42

reported on bending behaviour of composite girders with

cold formed steel U section. A new type of steel and concrete composite bridge with cold

formed steel U-shape girders, filled with concrete has been proposed. This U girder is cold

formed from a single steel sheet, and the amount of welding required is substantially small and

mass production could be possible. The authors carried out bending tests to investigate the static

bending behaviour of three girder models. The girder model at the span center behaved as a

composite beam. The girder model at the intermediate supports behaved as a prestressed beam

and the filled concrete restricted the local buckling of steel plates in compression. A design

calculation method for the girder section has been proposed assuming the Euler-Bernoulli

principle. For the design the stress of concrete (σ) is assumed to have a parabolic function of

concrete strain (εc) up to 0.002 and to be constant for εc over 0.002.

,002.0

2002.0

85.0 cc

kcc for 002.0c

,85.0 ckc for 002.0c

Where ck is compressive strength of concrete obtained from sample test.

The ultimate strain is set at 0.0035 for the slab concrete and 0.007 for the filled concrete

considering the confined effect. This method of design was verified by the test results. It is

20

concluded that the proposed bridge system has sufficient bending strength and good deformation

and rotation capacity and it is practical and feasible.

Baskar K. Shanmugam N.E. (2003)4 Details of an experimental investigation on steel–concrete

composite plate girders subject to the combined action of shear and bending are presented in this

paper. Six composite plate girders have been tested to failure in order to study their ultimate load

behaviour. Two different web-depth to thickness (d/t) ratios and two different moment/shear

ratios have been considered. Attention is focused on the variation in tension field action in web

panels due to composite action between the steel girder and concrete slab. Extensive strain

measurements have been made on the web panels in order to obtain a detailed picture of tension

field action. The ultimate load carrying capacity and the tension field width of composite plate

girders are found to increase significantly compared to the bare steel girders.

Jiansheng Fan Jianguo Nie and. Cai C.S. (2004)26

the behaviour of steel-concrete composite

beams under negative bending with different degrees of shear interaction have been investigated

in this paper. A model for predicting the stiffness behaviour of the composite beam under

negative bending at the serviceability limit state was developed. The model considers the slips at

the steel beam-concrete slab interface and concrete reinforcement interface, which explains the

decrease of structural stiffness compared with that based on the theory of full shear interaction. A

series of analytical equation based on this model were derived to calculate the maximum

deflection of a composite beam at working load and different types of loading cases and

boundary condition were considered. Also, a simplified method for calculating the deflection of

cantilever composite beam was established. To verify the reliability of the structural analytical

model and the equations, three beams was tested meanwhile the general purpose FE software

ANSYS was used to investigate the behaviour of composite beam. The non linear property of the

material, crushing of the concrete and slips at the steel and concrete reinforcement interface was

considered the results from testing and FE analysis show that the prediction of the deflection by

the proposed analytical method was sufficiently accurate in designing a cantilever and the

procedure can be used in further study on continuous composite beams. A three dimensional

non-linear Finite Element Analysis was performed using a commercial Finite Element Package

ANSYS to investigate the general behaviour of tested specimens. In this, the brittle property of

concrete is simulated with a solid element that can change its stiffness with the development of

21

cracking and crushing of concrete. The solid 65 element offered by ANSYS can simulate the

non-linear property of concrete. The deformed reinforcement was simulated using LINK 8

element and the steel was simulated using SHELL 63 element. In this the concrete interface

element is a component that transfers the shear force between reinforcement and steel beam, but

will not contribute to the moment of resistance. The bond slip relationship between concrete and

reinforcement was simulated using COMBIN 14 linear spring element. The shear studs were

modeled by non linear spring element COMBIN 39.The results show that slip always exists for

composite beams under negative bending and the slip effects in an additional curvature of the

beam bending and reduces the section stiffness by 10% to 20% with that of a beam without any

slip in serviceability condition. Moreover the results from the Finite Element Analysis agree with

that from experiments in terms of both stiffness and maximum load capacity.

Jianguo Nie, Yan Xiao and Lin Chen (2004) 27

static loading were conducted on 16 steel-

concrete composite beams and two steel beams to investigate shear resisting mechanism and the

strength of the composite beams. The main experimental parameters were the shear span aspect

ratio of the simply supported beams and the width and thickness of the concrete flanges. Based

on strain measurements, stress in the steel beam was analyzed using theories of elasticity and

plasticity and the vertical shear that the steel beam resisted was calculated. The shear resistance

of the concrete flange was obtained by subtracting the steel shear contribution from the total load

supplied. It was found to the concrete flange could sustain 33-56% of the total ultimate shear

applied to the composite beam specimens. Contrary to the typical assumption of neglecting the

concrete, shear contribution in most design code and specification. A shear strength equation that

considers the shear contributions of both the steel beam and the concrete flange is proposed.

Kottiswaran N. and Sundarajan.R (2005)31

an experimental investigation on the flexural

behaviour of steel concrete composite beam made up of thin walled cold formed steel was done

by the author. The ultimate strength capacity and the deflection characteristic of the beams were

determined. The results are compared with conventional reinforced concrete beams. The area of

tension steel in the conventional RCC beam was computed and replaced by thin walled cold

formed steel which can produce the same tensile force in the composite beam. The cold formed

steel sheet which was used in tension zone of the beam and effectively bonded with concrete

using shear connectors. The cold formed steel sheets of thickness 1mm and 1.5mm with different

22

cross sections, plain rectangular sheet, and channel section without lip (unstiffened channel).

Channel section with lip (stiffened channel) provided at the bottom as the principal

reinforcement. The moment carrying capacities at failure and first crack were reported. The

following points were concluded, the ultimate load carrying capacity of the composite beam of

channel without lip is lesser than that of control beam because of debonding of web portion of

the channel from concrete. Composite beams undergo more deformation than the conventional

reinforced concrete beam, designed for the same tensile force.

Dennis Lam and Ehab El-Lobody (2005)12

in composite beam design, headed stud shear

connectors are commonly used to transfer longitudinal shear forces across the steel Concrete

interface. Present knowledge of the load, slip behaviour and the shear capacity of the shear stud

in the composite beam are limited to data obtained from the experimental push-out tests. For this

purpose, an effective numerical model using the finite element method to simulate the push-out

test was proposed. The model has validated against test results and compared with data given in

the current code of practices, i.e., BS5950, EC4, and AISC. Parametric studies using the model

were performed to investigate variation in concrete strength and shear stud diameter. The finite

element models provided a better understanding to the different modes of failure observed during

experimental testing and hence shear capacity of headed shear studs in solid concrete slabs.

Thenmozhi. R and Sundararajan R. (2005)49

the author investigated the behaviour of Thin

Walled Steel Stiffened Concrete Composite beams with normal concrete as infill. The test

reports were used to ascertain the flexural strength of beams. Specimens of Cold-formed sheeting

coupons and reinforcing steel bars are tested in tension to ascertain their Yield stress and elastic

modulus. Comparison charts for load-deflection, load-strain and moment-curvature were

drawn. Analytical models for the ultimate moment were developed using rigid plastic analysis

and their performance is validated through experimental results.

Their analytical work includes the derivation of equations for determining the neutral axis.

Percentage of Composite action as a representative of degree of shear connection is evaluated.

Results from tests indicated that braces in the pure bending region delayed the separation of

sheet from concrete. Closer spacing of braces in the pure bending region does not show

significant influence in the ultimate moment. Thus the braces at the spacing of least lateral

23

dimension holds good for the confinement. Ultimate load carrying capacity for all the beams is

almost same for both full and partial shear connection.

Hyung-Joon Ahn and Soo-Hyun Ryu (2006)21

this study suggests modular composite beams,

where the prefab concept is applied to existing composite profile beams. The prefab concept

produces a beam a desired size of having two types of profile: side module and bottom module.

Module section found to improve construction efforts because it offers several benefits:

reduction of deflection due to creep and shrinkage, which might be found in existing composite

profile beams; increase in span/depth ratio; and free prefabrication of any required beams. Based

on the established analysis theory of composite profile beams, an analysis theory of modular

composite profile beam was suggested and analysis values were compared with experimental

ones. The behaviour of individual modules with increase of load was measured with a strain

gauge and the shear connection ratio between modules was analyzed by using the measured

values. As a result of experiment, it was found that theoretical flexural strength on condition of

full connection was 57%-80% by connection of modules for each specimen and it is expected

that the flexural strength will approximate the theoretical levels through further module

improvement.

Arivalagan Soundarajan, Kandasamy Shanmugasundaram (2008)3 this paper presented an

experimental study of normal mix, fly ash, quarry waste and low strength concrete (brick-bat

lime concrete) contribution to the ultimate moment capacity of square steel hollow sections.

Fifteen simply supported beams specimens of 1200-mm long steel hollow sections filled with

normal mix, fly ash, quarry waste and low strength concrete and identical dimension of hollow

section were experimented. Extensive measurements of such material properties, strain and

deflection were carried out. Theoretical studies of ultimate moment capacity of a beam specimen

were also calculated in this study for comparisons sake. These experimental investigation results

showed that the normal mix, fly ash, quarry waste and low strength concrete enhance the

moment carrying capacity of steel hollow sections. Furthermore, in these studies it can be found

that normal mix, fly ash and quarry waste concrete can be used in composite construction to

increase the flexural capacity of steel hollow sections.

24

Jianguo Nie, Liang Tang, and Cai C.S (2009)28

Eleven steel-concrete composite beams, four

under pure torsion, and seven under combined bending and torsion were tested to study their

torsional behaviours. Torsion-dominated and bending-dominated failure modes were observed,

depending on the ratio between the applied bending and torsional moments. Testing

results also

showed that the reinforced concrete slab contributes mainly to the torsional resistance of

composite beams and the contribution of steel joists to torsion is negligible. However, the steel

joist plays a vital role in restraining the concrete slab from deforming longitudinally, which

enhances the torsional strength of the concrete slab. Based on the experimental observations, a

three-dimensional behavioural truss model capable of analyzing composite beam sections

subjected to the combined bending and torsion was presented. In this model,

the section is

subjected to one- and two-dimensional stresses separately. The former resists the longitudinal

stresses due to bending and torsion while the latter resists the shear stresses due to

torsion. These

two systems are related based on the compatibility of strains and the equilibrium of stresses in

the longitudinal direction. The results predicted with this method are in good

agreement with

those obtained from the tests. Additionally, the interaction between bending and torsional

strengths was discussed.

Szilvia Erdélyi and László Dunai 48

The Authors performed an experimental study on a special

type of composite connection of a thin-walled beam to concrete deck. The behaviour of the shear

connectors are tested by standard push-out tests, considering several parameters such as

– fastening mode

– type and the geometry of screw

– the arrangement of trapezoidal sheeting

– the geometry of steel components and the effect of the reinforcement

The failure modes are observed and classified, according to the specialties of the behaviour of

thin-walled structures. From the measured data, the load-displacement relationships are

determined and the design values of the stiffness, resistance and ductility are calculated.

2.2 STUDIES ON CONFINEMENT

This thesis uses a beam system which has cold formed sheet as both formwork and

reinforcement. As the sheet encloses the concrete in all three sides, the sheet gives partial

25

confinement which is expected to enhance the compressive strength of concrete. Hence the

works related to confined concrete are discussed in this section.

Soliman M.T.M. and .Yu C.W. (1967)45

presented an extensive experimental study on confined

concrete. They have developed the flexural stress-strain relationship of concrete confined by

rectangular transverse reinforcement. To understand the plastic deformation capacity of critical

regions reinforced with longitudinal and transverse reinforcement, it was felt that the stress-strain

relationship of bound concrete in flexure must first be established. 16 specimens were tested by

the authors in a specially constructed testing frame under the action of a major and minor load.

The stress-strain relationship for the concrete was obtained by an approach similar to that used

by Hognestad, Hanson and McHenry in conjunction with a special graphical interpolation

technique. A generalized relationship was finally reported as a function of the spacing of binder,

the ratio of the bound area to the total are under compression, the size of the binders, and the

shape of the concrete cross section. The authors suggested a parameter (q”) which refers to the

effectiveness of the transverse reinforcement given as

20028.0"

"4.1

"BSSA

SSAA

A

qs

os

c

b

where Ab – area of bound concrete under compression

Ac – area of concrete under compression

As” – sectional area of transverse reinforcement

S0 – longitudinal spacing at which transverse reinforcement is not effective

in confining the concrete

S – Longitudinal spacing of transverse reinforcement

B – b1 or 0.7d1, whichever is the greater

Sundara Raja Iyengar K.T., Prakash Desayi , and Nagi Reddy (1970) 47

reported on stress-

strain characteristics of concrete confined by steel binder. In this investigation, the authors

reported that the ductility of concrete can be increased by confinement. The author presented the

results of axial compression tests on the specimens in whom the variables were: the strength of

the concrete, the size and shape of the test specimen and diameter and the type of spiral wire are

26

different. A new factor called the confinement index is introduced to define the confinement

quantitatively as follows:

Confinement index = bb

c

y

f

f'

Here fy - yield strength of steel binder

f’c - ultimate strength of plain concrete specimen

b - Particular volumetric ratio, i.e. value of b when the pitch of the binder is equal

to the least lateral dimension.

b - Volumetric ratio, i.e. ratio of the volume of binder to the volume of

the confined concrete

The authors concluded that ultimate strengths and strains increase with confinement and linearly

with the confinement index. Confinement is found to be effective only when the pitch of

binders is less than the least lateral dimension of the confined specimen. Of the three types of

binders studied – circular spirals, square spirals and stirrups – the first was the most effective

while the last was least effective. The mechanics of the action of steel binders and a similarity

between the confining effects of steel binders and of hydrostatic pressure are discussed.

Mander J.B...Priestley M.J.N and Park R (1988)32

developed a theoretical stress-strain model

for confined concrete. Tests have shown that strength enhancement from confinement and the

slope of the descending branch of the concrete stress strain curve have a considerable influence

on the flexural strength and ductility of reinforced concrete columns. In this, a stress-strain

model was developed for concrete confined by transverse reinforcement subjected to uniaxial

compressive loading. They concluded that the form of stress-strain curve for confined concrete is

expressed in terms of simple uniaxial relation suggested only requires three control parameters.

Unloading and reloading curves can be developed for the cyclic loading response. Reinforced

27

concrete members with axial compression forces are confined by using transverse steel to

enhance the member strength in ductility.

Mohd..M.Ziara, Haldane D and Kuttab A.S (1993)35

presented a paper on shear and flexural

strengths resulting from confinement of the compression region in circular section structural

concrete beams, The program of experimental work included eight 200mm diameter beams

traditionally designed to resist shear; however, the stirrups configuration in several of the beams

were determined by the shapes of the compressive force path. It was concluded that the

enhancement of the concrete strength in the compression regions due to the confining influence

of the stirrups offsets the reduction in the flexural capacity of the beams due to shear effects.

The flexural capacity and ductility of the beams resulting from confinement were found to be

higher than the corresponding traditionally detailed beams. The experimental results indicated

that the ductility and strength of these beams were more than 50% and up to 32% (depending on

the level of confinement) greater than found in beams detailed according to current code

provisions.

Mohamed M.ziara, David Haldane and Atallah S.Kuttab (1993)36

presented a paper on flexural

behaviour of beams with confinement. The principal aim of the paper is to examine both

theoretically and experimentally, the flexural behaviour of concrete beams in which confinement

stirrups were introduced in the compression zone.

The experimental investigation included 12 under reinforced beams, eight of which had concrete

compression regions, as defined by the compression force path (CFP) concept, confined with

rectangular closed stirrups. The remaining beams were traditionally detailed beams. The

presence of confinement was shown to increase the ductility of the beam, however no

comparable increase was found in their respective flexural capacities. A method for the

evaluation of the flexural capacity of beams in which confinement of the compression regions is

present has been proposed. A method for the design of over reinforced beams utilizing the

ductility resulting from confinement has also been outlined and investigated experimentally

using four types of over reinforced beams selected from another extensive test program.

Ferhun.C.Caner, and Zdenek P.Bazant (2002)18

reported on lateral confinement needed to

suppress softening of concrete in compression. This is proposed to avoid brittle character of

28

collapse. To this end the recently developed “tube squash” tests, in which a short concrete filled

steel tube is squashed to about a half of its original length and allowed to bulge are conducted

with cubes of different wall thicknesses. The purpose of enhancing concrete columns in tubes is

to ensure ductility. A finite strain finite element computer code with a micro plane constitutive

model is used to stimulate the tests. After its verification and calibration of tests the code is used

to analyze non-buckling concrete filled tubular columns and spirally reinforced columns. It is

found that softening in the load deflection diagram can be fully suppressed only if the

reinforcement ratio (ratio of the tube volume or spiral volume to the total volume of column)

exceeds about 14%. If mild softening is allowed, the reinforcement ratio must still exceed about

8%. The ratios are surprisingly high. If they are not used in design, one need to pay attention to

the localization of softening damage, accept the (deterministic) size effect engendered by it, and

ensure safety margins appropriate for protecting against sudden explosive brittle collapse. This is

of particular concern for the design of very large columns.

Wu Y.F., M.C.Griffith and D.J.Oehlers (2003)50

conducted experiments to improve the strength

and ductility of rectangular reinforced concrete columns through composite partial interaction.

By increasing the compressive strength of concrete columns, through composite partial

interaction such as by bolting a steel plate to the compression face of a column, this new

composite action approach is shown to successfully delay concrete crushing in the plastic hinge

zone. The experimental results confirm theoretical predictions that composite partial interaction

can be used to increase either the strength or ductility (or both) of concrete columns. This

technique in its current form would be applicable primarily to columns subject to one-way

bending. The author also commented that “further research is under two-way bending.

2.3. STUDIES ON FINITE ELEMENT ANALYSIS OF STRUCTURES

Sreekanta Das and Muhamed. Hadi N.S., (1996)46

analysed R.C.C. members using

MSC/NASTRAN. They found out that the difficulty in modelling the concrete behaviour was

due to the strain-softening behaviour of concrete once it was yielded. They discussed briefly the

modelling procedures for R.C.C. Shallow beams in MSC/NASTRAN.

Antonio F. Barbosa and Gabriel O. Ribeiro (1998) 2

investigated the possibilities of performing

non-linear finite element models in the analysis of R.C.C. structures. The authors used finite

29

element code ANSYS, version 5.3. Solid elements have been used in beam modelling to support

concrete. Each mesh has been analysed four times, according to four different materials models

namely, linear elastic and crushing capability, elastic perfectly plastic, multilinear work

hardening along with crushing capability. The results of the analysis performed have been

compared to a load – deflection curve derived from an analytically determined moment –

curvature relationship. The authors concluded that only nonlinear stress strain relations for

concrete in compression have made it possible to reach the ultimate load and determine the entire

load – deflection diagram.

Fanning.P. (2001)17

discussed about the numerical models adopted in ANSYS to find out non-

linear response of concrete under loading and recommended appropriate numerical modeling

strategy for Reinforced Cement Concrete and post-tensioned Concrete beams. Finite element

models of 3m ordinary reinforced concrete beams and 9m post-tensioned concrete beams

constructed in ANSYS V5.5.The dedicated concrete element have accurately captured the

nonlinear response of these systems up to failure. The dedicated element employs a smeared

crack model to allow for concrete cracking with the option of modeling the reinforcement in a

distributed or discrete manner. The author used the typical concrete element in ANSYS, Solid

65 for the analysis.

In conclusion the dedicated smeared crack model is an appropriate numerical model for

capturing the flexural modes of failure of reinforced concrete systems. Comparisons with

experimental load-deflection responses are discussed for ordinary reinforced concrete beams and

Post-tensioned concrete beams.

Damian Kachlakev, Thomas Miller and Solomon Yim (2001) 11

In their thesis ‘Finite Element

Modeling of Concrete Structures Strengthened with FRP Laminates’ to simulate the behaviour of

four full-size beams from linear through nonlinear response and up to failure, using the ANSYS

program was done. An eight-node solid element solid 65 was used to model the concrete. A

layered solid element, Solid46 was used to model the FRP composites. An eight-node solid

element, Solid45 was used for the steel plates at the supports in the beam models. Link8 – 3-D

span element was used to model the steel reinforcement. By taking advantage of the symmetry of

the beams, a quarter of the full beam was used for modeling. Ideally, the bond strength between

the concrete and steel reinforcement should be considered. However, in this study perfect bond

30

between materials was assumed. To provide the perfect bond the link element for the steel

reinforcing was connected between nodes of each adjacent concrete solid element so that the two

materials shared the same nodes. The same approach was adopted for FRP composites.

The general behaviour of the finite element models represented by the load-deflection plots at

midspan show good agreement with the test data from the full-scale beam tests. However the

finite element models show slightly more stiffness than the test data in both the linear and

nonlinear ranges. The effects of bond- slip (between the concrete and steel reinforcing) and

micro cracks occurring in the actual beams were excluded in the finite element models,

contributing to the higher stiffness of the finite element models. Comparisons between the

experimental data and the results from finite element models showed good agreement and the

different failure mechanisms from ductile to brittle were simulated.

Dennis Lam, Ehab Ellobody A, (2005)15

the authors investigated the structural performance of

shear connection in composite beams with profiled steel sheeting. An accurate and efficient

nonlinear finite element model was developed to study the behaviour of headed stud shear

connectors welded through-deck. The profiled steel sheeting had transverse ribs perpendicular to

the steel beam. The material nonlinearities of concrete, headed stud, profiled steel sheeting,

reinforcement and steel beam were included in the finite element model. The capacity of shear

connection, load–slip behaviour of the headed stud and failure modes were predicted. The results

obtained from the finite element analysis were verified against experimental results. An

extensive parametric study was conducted to study the effects on the capacity and behaviour of

shear connection by changing the profiled steel sheeting, geometries, the diameter and height of

the headed stud as well as the strength of concrete.

Queiroz F.D. Vellasco. P. (2006)37

the authors investigated on the evaluation of full and partial

shear connection in composite beams using the commercial finite element (FE) software

ANSYS. The proposed three-dimensional FE model was able to simulate the overall flexural

behaviour of simply supported composite beams subjected to either concentrated or uniformly

distributed loads. Load deflection behaviour, longitudinal slip at the steel–concrete interface,

distribution of stud shear force and failure modes are studied with ANSYS software. The

reliability of the model is demonstrated by comparisons with experiments and with alternative

numerical analysis. The authors performed parametric study using the calibrated FE model.

31

Elastic-plastic shell (SHELL43) for steel, solid (SOLID65) elements for the concrete slab and

nonlinear springs (COMBIN39) to represent the shear connectors were used in the analysis. The

authors concluded that the continuation of the shear connection beyond the beam supports of

simply supported beams can affect not only the overall system response, but also the slip and the

stud force distributions along the beam.

2.4 CRITICAL REVIEW

The earlier investigations indicates the advantages of cold formed steel decks sections and

development of steel stiffened channel as part of side formwork as well reinforcement replacing

conventional steel bars. Then came into picture profiled composite beam where steel profiled

sheets as permanent form work to the sides and bottom of RCC beams. It was seen that the

flexural and shear strength increases in this beams without loss of ductility and is not prone to

shear bond failure at the profiled steel concrete interfaces. In Hossain’s30

work he studied the

flexural strength and failure modes of TWC filled beams. In Thenmozhi’s48

work in addition to

flexural strength of composite beams with plain cold formed sheet elements subjected to pure

bending and deflection ductility aspects are studied.

However no specific work has been done so far for the composite beam shuttered with plain cold

formed steel sheeting subjected to pure torsion and combined bending and torsion. Experimental

studies dealing with above characteristics are scant. And also no specific guidance for the design

of confined steel concrete composite beams is available in Bureau of Indian Standards (BIS).

Before a design procedure can be formulated, it is essential to obtain a better understanding for

the behaviour of composite beam under pure bending, pure torsion, and combined bending and

torsion. Hence an extensive experimental programme on the behaviour under combined loading

is considered as research gap and it is hoped that this investigation will make a contribution to

that end.