740 research outputs found
Nonlinear Finite Element Analysis and Design of Composite Beams Subjected to Shear and Bending
No full textThe shear strength and the moment-shear interaction in steel-concrete composite beams was previously evaluated by the authors through an experimental program comprised of fourteen tests on simply-supported composite beams. In this paper, a nonlinear finite element model is developed to simulate the behavior of the experimental section. The model was assessed in terms of the ultimate strength and the failure modes of the composite beams under shear and bending and found to be accurate in capturing the nonlinear response of the specimens. The numerical model was then used to carry out an extensive parametric study on the various factors that influence the shear strength of a composite beam. These factors include the slab thickness, the slab width, and the reinforcement ratio. Based on the results of the numerical study, design models are proposed for the calculation of the shear strength and the shear-moment interaction in composite beams.</p
Behaviour of composite beams under combined bending and tension
No full textThe results of an experimental programme on composite beams under combined bending and tension are presented in this paper. Results from this study extend previous work to form a completed interaction diagram for composite beams subjected to combined bending and tension. The experimental series detailed in this paper was conducted on six beams under combined positive bending and testing. The results compared well with the results from a rigid plastic analysis
Time dependent analysis for composite steel-concrete beams with innovative deep trapezoidal decks
No full textComposite steel concrete beams are formed by connecting concrete slabs to a supporting structural steel beam. In the early 1900’s, composite beams were considered favourable for bridge design but in recent decades, composite steel and concrete structures are employed extensively in modern high rise buildings. The flexural strength of composite beams is greatly influenced by the strength and ductility of the shear connectors between the structural steel beam and the concrete slab. The behaviour of the shear connectors is important in understanding the shear force transmitted and the degree of slip which occurs at the interface of the steel and concrete.
Composite steel-concrete beams are becoming increasingly popular in multistorey buildings due to their higher span/depth ratio, reduced deflections and increased stiffness value. However, their performance is highly dependent on the load-slip characteristics of the shear connectors. More recently, trapezoidal profiled slabs are becoming increasingly more popular for high-rise buildings when compared with solid slabs because they can achieve large spans with little or no propping and they require less concrete and plywood formwork. However, the profiles used to achieve these savings can have a detrimental effect on the shear connector behaviour.
For composite steel-concrete structures, concrete not only provides the compressive strength, but also the fire resistance to the floor surface, whilst the steel predominantly provides the tensile strength. When acting compositely through a shear stud, the composite steel-concrete member is stiffer and stronger. When concrete creep and shrinkage are considered, the deformation will increase with time. When the creep and shrinkage behaviour of the concrete is considered, the factors affecting the shear connection are the stiffness and strength of shear connectors and the stiffness and strength of the surrounding concrete. The strength of concrete is reduced according to time due to creep and shrinkage.
It has been found that the flexural strength of composite beam is greatly controlled by the ductility and strength of headed stud shear connectors. In addition, the ductility and strength of headed stud shear connectors are also influenced by time-dependent characteristics of composite concrete-steel beam members which herein mainly related to creep and shrinkage of concrete. However, this long-term behaviour is often treated in an oversimplified manner in most of standard codes. Therefore, this paper herein investigated the behaviour of headed stud shear connectors in the composite beam which takes consideration of creep and shrinkage of concrete.
This paper conducted two series of push test experimental studies and they were compared with Finite Element Analysis using commercial software known as ABAQUS. The experimental studies consisted the testing of eight push test specimens. The first series of experiment were the short-term behaviour of headed stud shear connectors in solid and profile steel sheeting slab. The second series of experiments were similar to first series but long-term behaviours were taking into account for both solid and profiled steel sheeting slab. In order to prove that an accurate finite element model has been developed to investigate the behaviour of the shear connection in composite steel-concrete beams for both solid and profiled slabs when creep is taken into account, the finite element models were compared with existing push test experimental studies.
In general, there are three differences in behaviours between solid slab and profiled steel sheeting. The first difference is the failure mode. For solid slab, the failure mode is related to shear connector failure. For profiled steel sheeting slab, the failure mode is related to concrete failure. Secondly, the increasing rate of strain in headed stud shear connectors of solid slab are higher than in profiled steel sheeting slab. The strain is directly proportional with stress. Therefore, in other word, stresses in headed stud shear connectors in solid slab are higher than the headed studs in profiled steel sheeting slab. After 100 days, the slip of headed studs for solid slab increased by 50% compared with only 10% in profiled steel sheeting slab.
Finally, the ultimate load of headed stud in solid slab is generally higher than in profiled slab. It can be concluded that the interface between steel and concrete plays a major role in the strength of the headed stud shear connectors. If profiled steel sheeting is placed between the steel and concrete, the strength of headed stud shear connectors is about 54% of the strength of studs in a solid slab specimen without profiled steel sheeting. This decrease in strength can explained due to the reduction of friction at the interface of steel and concrete.
The results from experiments are also compared with Australian, Eurocode 4 and American Standards. It can be seen that the Australian and Eurocode 4 Standards have good agreements with the experimental results and finite element results while American Standard seems to be overestimate for strength of headed studs in solid slabs. Therefore, the designer should consider this issue carefully to prevent from exceeding the failure mode.
From the finite element analyses, when creep and shrinkage are considered, the reduction in stiffness, ultimate shear capacity and slip capacity for both the solid and profiled slabs was observed. From the finite element analyses, the solid slab demonstrated that the failure mode is dominated by shear yielding failure, whilst failure in the profiled slabs can be attributed to concrete failure. Stresses in the shear connector and concrete are lower compared with those in the solid slab, due to the addition of the steel profile. It also can be observed that the solid slab generally has a higher ultimate load compared with that of the slab with profiled steel sheeting
Behaviour and Design of Composite Beams Subjected to Combined Bending and Axial Forces
No full textSteel-concrete composite beams can often be subjected to combined bending and high axial forces. However, the moment-axial force interaction in composite beams is not covered by the current codes of practice. An experimental investigation comprising twenty-four full-scale tests was conducted recently in the University of Western Sydney, aiming to investigate the behaviour and ultimate strength of composite beams under bending and axial forces. Nonlinear finite element simulations and parametric studies complemented the tests. It was found that the moment capacity of a composite beam is reduced in most situations under simultaneous axial loading. Partial shear connection does not alter the shape of the interaction curve, but it affects the ductility of the beam and the amount of axial load transferred to the slab. Based on the experimental and numerical results, simplified design rules are proposed to account for the effect of axial loads on the bending capacity of composite beams.</p
Local and post-local buckling of steel-concrete composite panels under combined states of stresses
No full textClosure to "strength analysis of steel-concrete composite beams in combined bending and shear" by Qing Quan Liang, Brian Uy, Mark A. Bradford, and Hamid R. Ronagh
No full textThe strength analysis of steel-concrete composite beams in combined bending and shear is evaluated. The cross-sectional area of the beam element was modified to make it equivalent in both strength and stiffness to the actual stud shear connectors in the composite beam. The 3D beam elements were used in the finite-element model to simulate the discrete behavior of stud shear connectors in composite beams. It was observed that the stiffness of the shear connection modeled using finite elements was almost the same as the stiffness of the shear connection in the real beam. The ultimate strain of 0.25 was assured for structural steel in the analysis and the experimental values of the yield strength and ultimate strength were used in the analysis for the steel. The model can be used to determine the ultimate strengths of supported composite beams under combined bending and shear
A push test study on the behavior of post-tensioned composite steel-concrete slabs
No full textPost-tensioned composite steel-concrete slabs represent an innovative form of building floor application, which combine the structural advantages of the two most popular flooring systems, comprising post-tensioned slabs in the case of concrete structures and profiled composite slabs in the case of steel structures. The complex interaction between the profiled steel sheets and concrete is usually determined through a push test. A significant step toward understanding the bond behaviour is to generate a local bond stress-slip relationship. In this context, this paper presents results from a preliminary push test study using profiled steel sheets to determine the possible influence of prestress on the bond between the profiled steel sheets and concrete. The variables investigated in the study were (1) level of prestress and (2) height of push specimen. The results of this study indicate that prestress has a negative effect on the bond between the profiled steel sheets and concrete in post-tensioned composite slabs. This is an important finding, which needs to be considered in the ultimate strength of post-tensioned profiled composite slabs
Design rules, experimental evaluation, and fracture models for high-strength and stainless-steel hourglass shape energy dissipation devices
No full textSteel yielding hysteretic devices provide a reliable way to increase the energy dissipation capacity of structures under seismic loading. Steel cylindrical pins with hourglass shape bending parts (called web hourglass shape pins - WHPs) have been recently used as the energy dissipation system of posttensioned connections for self-centering steel moment-resisting frames. This work evaluates the cyclic behavior of WHPs made of high-strength steel and two grades of stainless steel, i.e., austenitic grade 304 and duplex. Design rules for WHPs are established using principles of mechanics. Twenty-six tests using different cyclic loading protocols and different WHP geometries were conducted. The tests showed that the WHPs have stable hysteretic behavior and high fracture capacity. WHPs made of duplex stainless steel have the most favorable and predictable performance for seismic applications. Two micromechanics-based fracture models, i.e., the void growth model and the stress-modified critical strain model, were calibrated and their parameters are provided for high-strength steel and the two types of stainless steel. The ability of the cyclic void growth model to predict fracture in WHPs under cyclic loading is also evaluated.</p
Nonlinear analysis of composite steel-concrete beams under combined flexure and torsion incorporating the effects of partial shear connection
No full textThis paper investigates the behaviour of composite steel-concrete beams under combined flexure and torsion incorporating the effects of partial shear connection by using the finite element analysis method. 3-D finite element models have been developed to account for the geometric and nonlinear behaviour of the materials. This model is then verified by experimental test results. It has been shown that there is an increase in torsional capacity in the presence of flexure but the flexural capacity remains the same in the presence of torsion. A parametric study has been carried out and showed similar trends have been seen even with an increase in span length with an increase in the ratio of torsional capacity when the span increases
The effect of carbon nanotubes on the headed stud shear connectors for composite steel-concrete beams under elevated temperatures
No full textThis paper presents a novel experimental and numerical analysis of composite steel-concrete beams at elevated temperatures utilising carbon nanotube. Push tests were conducted as a part of the experimental study to determine the strength of the headed stud shear connectors in both normal concrete and carbon nanotube concrete. The specimens were tested under ambient temperature, 200°C, 400°C, and 600°C, respectively. Results from the experimental study illustrated the reduction of ultimate load and stiffness as temperatures increased. The numerical analysis was in good agreement with the experimental study results. Even though carbon nanotube had no effect on the ultimate load, however, the carbon nanotube reduced concrete spalling and cracking when compared to normal concrete. The carbon nanotube was observed to take effect at temperatures greater than 400°C. As a conclusion, the carbon nanotube concrete material would be an effective choice for reducing concrete spalling and cracking when exposed to elevated temperatures
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