• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.1001-1019
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• 2016

The connector is the most important part of a composite beam and promotes a composite action between a steel beam and concrete slab. This paper presents the experiment results for three large-scale beams with a newly puzzle shape of crestbond. The behavior of this connector in a composite beam was investigated, and the results were correlated with those obtained from push-out-test specimens. Four-point-bending load testing was carried out on steel-concrete composite beam models to consider the effects of the concrete strength, number of transverse rebars in the crestbond, and width of the concrete slab. Then, the deflection, ultimate load, and strains of the concrete, steel beam, and crestbond; the relative slip between the steel beam and the concrete slab at the end of the beams; and the failure mechanism were observed. The results showed that the general behavior of a steel-concrete composite beam using the newly puzzle shape of crestbond shear connectors was similar to that of a steel-concrete composite beam using conventional shear connectors. These newly puzzle shape of crestbond shear connectors can be used as shear connectors, and should be considered for application in composite bridges, which have a large number of steel beams.

• Steel and Composite Structures
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• v.20 no.6
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• pp.1183-1191
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• 2016

The internal crack propagation, the failure mode and ultimate load bearing capacity of the steel-concrete-steel composite beam under the four-point-bend loading is investigated by the numerical simulation. The results of load - displacement curve and failure mode are in good agreement with experiment. In order to study the failure mechanism, the composite beam has been modeled, which part interface interaction between steel and concrete is considered. The results indicate that there are two failure modes: (a) When the strength of the interface is lower than that of the concrete, failure happens at the interface of steel and concrete; (b) When the strength of the interface is higher than that of the concrete, the failure modes is cohesion failure, i.e., and concrete are stripped because of the shear cracks at concrete edge.

• Computers and Concrete
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• v.29 no.3
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• pp.127-144
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• 2022

To investigate the flexural stiffness of the steel-composite beam, the contributions of the concrete slab and steel beam to the stiffness were considered separately. The method for flexural stiffness of the composite beam, considering the stiffness of the concrete slab and steel beam, was proposed in this paper. In addition, finite element models of the composite beams were established and validated. Parametric analyses were carried out to study the effects of different parameters on the neutral axis distance reduction factors of the concrete slab and steel beam. Afterward, the neutral axis distance reduction factors were fitted, and the stiffness combination coefficients of the two parts were solved. Based on the stiffness combination coefficients, the flexural stiffness of the composite beam can be obtained. The proposed method was validated by the tested and analyzed results. The method has a simple form and high accuracy in predicting the flexural stiffness of the steel-concrete composite beam, even though the degree of shear connection is less than 0.5.

• Steel and Composite Structures
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• v.32 no.5
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• pp.583-594
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• 2019

In recent years, composite concrete-filled steel tubular (CFST) members have been widely utilized in framed building structures like beams, columns, and beam-columns since they have significant advantages such as reducing construction time, improving the seismic performance, and possessing high ductility, strength, and energy absorbing capacity. This paper presents a new composite joint - the composite CFST beam-column joint in which the CFST member is used as the beam. The main components of the proposed composite joint are steel H-beams, CFST beams welded with the steel H-column, and a reinforced concrete slab. The steel H-beams and CFST beams are connected with the concrete slab using shear connectors to ensure composite action between them. The structural performance of the proposed composite joint was evaluated through an experimental investigation. A three-dimensional (3D) finite element (FE) model was developed to simulate this composite joint using the ABAQUS/Explicit software, and the accuracy of the FE model was verified with the relevant experimental results. In addition, a number of parametric studies were made to examine the effects of the steel box beam thickness, concrete compressive strength, steel yield strength, and reinforcement ratio in the concrete slab on the proposed joint performance.

• Steel and Composite Structures
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• v.21 no.3
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• pp.679-688
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• 2016

Structural design of a composite beam is influenced by two main factors, strength and ductility. For the design to be effective for a composite beam, say an RC slab and a steel I beam, the shear strength of the composite beam and ductility have to carefully estimate with the help of displacements between the two members. In this investigation the shear strengths of steel-concrete composite beams was analyzed based on the respective variable parameters. The methodology used by ANFIS (Adaptive Neuro Fuzzy Inference System) has been adopted for this purpose. The detection of the predominant factors affecting the shear strength steel-concrete composite beam was achieved by use of ANFIS process for variable selection. The results show that concrete compression strength has the highest influence on the shear strength capacity of composite beam.

• Steel and Composite Structures
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• v.28 no.1
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• pp.39-49
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• 2018

The concrete bridge decks are usually precast and in-situ assembled with steel girders with post-pouring joint in the construction practice of super-wide steel-concrete composite beam. But the difference of concrete age between the precast slabs and the post-pouring joint has been not yet considered for the long-term performance analysis of this kind composite beam. A simply supported precast-assembled T-shaped beam was taken as an example to analyze the long-term performance of steel-concrete composite beam with post-pouring joint. Based on the deformation coordination conditions of the old-new concrete deck and steel girder, a theoretical model for the long-term behavior of precast-assembled composite beam is proposed in this paper according to age-adjusted effective modulus method. Then, the feasibility of the proposed model is verified by the available test data from the Gilbert's composite beams. Parametric studies were preformed to evaluate the influences of the cross-sectional area ratio of the post-pouring joint to the whole bridge deck, as well as the difference of concrete age between the precast slabs and the post-pouring joint, on the long-term performance of the composite beam. The results indicate that the traditional method without considering the age difference would seriously underestimate the effect of creep and shrinkage of concrete bridge decks. The concrete age difference between the precast slabs and the post-pouring joint should be demonstrated for the life cycle design and long-term performance analysis of precast-assembled steel-concrete composite beams.

• Steel and Composite Structures
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• v.45 no.6
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• pp.895-905
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• 2022

Composite flooring systems consisting of cold-formed steel joists and reinforced concrete slabs offer an efficient, lightweight solution. However, utilisation of composite action to achieve enhanced strength and economical design has been limited. In this study, finite element modelling was utilised to create a three-dimensional model which was then validated against experimental results for a composite flooring system consisting of cold-formed steel joists, reinforced concrete slab and steel bolt shear connectors. This validated numerical model was then utilised to perform parametric studies on the performance of the structural system. The results from the parametric study demonstrate that increased thickness of the concrete slab and increased thickness of the cold formed steel beam resulted in higher moment capacity and stiffness of the composite flooring system. In addition, reducing the spacing of bolts and spacing of the cold formed steel beams both resulted in enhanced load capacity of the composite system. Increasing the concrete grade was also found to increase the moment capacity of the composite flooring system. Overall, the results show that an efficient, lightweight composite flooring system can be achieved and optimised by selecting suitable concrete slab thickness, cold formed beam thickness, bolt spacing, cold formed beam spacing and concrete grade.

• Steel and Composite Structures
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• v.4 no.3
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• pp.169-188
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• 2004

A mechanics model is developed in this paper for concrete-filled steel CHS (circular hollow section) beam-columns. A unified theory is described where a confinement factor (${\xi}$) is introduced to describe the composite action between the steel tube and the filled concrete. The predicted load versus deformation relationship is in good agreement with test results. The theoretical model was used to investigate the influence of important parameters that determine the ultimate strength of concrete-filled steel CHS beam-columns. The parametric and experimental studies provide information for the development of formulas for the calculation of the ultimate strength of the composite beam-columns. Comparisons are made with predicted beam-columns strengths using the existing codes, such as LRFD-AISC-1999, AIJ-1997, BS5400-1979 and EC4-1994.

• Steel and Composite Structures
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• v.33 no.1
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• pp.143-162
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• 2019

A number of desirable characteristics concerning excellent durability, aesthetics, recyclability, high ductility and fire resistance have made stainless steel a preferred option in engineering practice. However, the relatively high initial cost has greatly restricted the application of stainless steel as a major structural material in general construction. This drawback can be partially overcome by introducing composite stainless steel-concrete structures, which provides a cost-efficient and sustainable solution for future stainless steel construction. This paper presents a preliminary numerical study on stainless steel-concrete composite beam-to-column joints with bolted flush endplates. In order to ensure a consistent corrosion resistance within the whole structural system, all structural steel components were designed with austenitic stainless steel, including beams, columns, endplates, bolts, reinforcing bars and shear connectors. A finite element model was developed using ABAQUS software for composite beam-to-column joints under monotonic and symmetric hogging moments, while validation was performed based on independent test results. A parametric study was subsequently conducted to investigate the effects of several critical factors on the behaviour of composite stainless steel joints. Finally, comparisons were made between the numerical results and the predictions by current design codes regarding the plastic moment capacity and the rotational stiffness of the joints. It was concluded that the present codes of practice generally overestimate the rotational stiffness and underestimate the plastic moment resistance of stainless steel-concrete composite joints.

• Steel and Composite Structures
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• v.14 no.3
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• pp.243-265
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• 2013

Distortional and local buckling are important factors that influences the bearing capacity of steel-concrete composite box-beam. Through theoretical analysis of distortional buckling forms, a stability analysis calculation model of composite box beam considering rotation of steel beam top flange is presented. The critical bending moment calculation formula of distortional buckling is established. In addition, mechanical behaviors of a steel beam web in the negative moment zone subjected separately to bending stress, shear stress and combined stress are investigated. Elastic buckling factors of steel web under different stress conditions are calculated. On the basis of local buckling analysis results, a limiting value for height-to thickness ratio of a steel web in the elastic stage is proposed. Numerical examples are presented to verify the proposed models.