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Owing to the good ductility of steel and high strength and excellent corrosion resistance of fibre-reinforced polymer (FRP), concrete beams reinforced with hybrid steel and FRP bars exhibit better ductility than FRP-reinforced concrete beams as well as higher load-carrying capacities and better corrosion resistance than steel-reinforced concrete beams. However, the inherent brittleness of concrete in tension results in steel corrosion because of wide cracks and accelerated fracture of FRP reinforcement because of crack-induced stress concentration. This study investigated the effects of ultra-high ductile engineered cementitious composites (ECCs) on the flexural behaviour of hybrid steel and FRP-reinforced beams. Six hybrid-reinforced beams with various reinforcement ratios, matrix types and ECC pouring positions were tested in four-point bending. The flexural behaviours of the beams in terms of failure modes, crack patterns and developments, load versus deformation relationships and ductility are discussed herein in detail. We observed that substituting ECC with concrete results in a higher load-carrying capacity and better ductility of the hybrid reinforced beams owing to the excellent characteristics of ECC materials. When a layer of ECC is poured in the tension zone, the average crack width and crack spacing along the beam decrease; therefore, the longitudinal reinforcements can be adequately protected.

This study aimed to reveal the existence of size effect on the shear connectors used in the steel-concrete composite beams and slabs. The experimental study contains the monotonic tests of nine pushout specimens with the headed studs. Three-dimensional scaling was used for geometrically similar specimens of three sizes. High strength concrete slabs were used on both sides of the steel I-beam. The failure modes of the specimens include both concrete crushing and stud yielding. Finite element (FE) verification of the specimens was conducted using a realistic concrete damage constitutive model, Microplane Model M7. It is shown that there may be a non-negligible size effect based on the fracture patterns of the composite member. Bažant’s size effect law (SEL) can fit the size effect behavior of the shear connectors. The design equations which do not include a size effect term have high correction factors that overestimate the tested specimens. A new design equation can be drawn using the size effect factor for strength reduction of shear connectors.

Although traditional steel-concrete composite beam has excellent structural characteristics, it cannot meet the requirement of quick disassembly and repair in the bridge. This article presents an experimental study on friction performance of damaged steel-concrete interface in recoverable composite beam connected by high-strength frictional bolts. A total of 21 specific split tests were carried out using different concrete strength, steel strength, and surface treatment of steel. The experimental results showed that the demountable high-strength frictional bolt used in composite beam has similar performance as in the bare steel structures. The initial friction coefficient and slip stiffness were measured to be 0.34–0.47 and 52.3–116.1 kN/mm, respectively. Friction performance of damaged interface was obtained, proving that friction coefficient and slip stiffness will not decrease after the first slip damage. It is also confirmed that shot blasted steel and concrete with higher strength were more suitable in the demountable composite beam.

The timber board interlayer is applied as the formwork for the pouring of concrete slab in various practical applications of timber–concrete composite structures, with the rehabilitation of timber buildings, in particular. At present, there are few studies performed to study the shear stiffness of inclined screws in timber–concrete composite beams with timber board interlayer. In this article, eight groups of shear tests were carried out to study the shear stiffness of inclined screws in timber–concrete composite beams with timber board interlayer. The key parameters included the embedment depth of the screw connector into timber, screw diameter, the thickness of concrete slab, and concrete strength. As indicated by the test results, the shear stiffness of the inclined screws was improved as the embedment depth of screw into timber and screw diameter increased. When the embedded depth of screw into concrete remained unchanged, the thickness of concrete slab and concrete strength exhibited no significant impact on the shear stiffness of inclined crossing screws. On the basis of the theory of a beam on a two-dimensional elastic foundation, the calculation method for predicting the shear stiffness of inclined screw in timber–concrete composite beams with interlayer was proposed. The comparisons demonstrated that the shear stiffness of inclined screw can be well predicted using the calculation method.

The fire beam element method is a tool for structural fire analyses that simplifies a structure into a skeletal frame consisting of only beam and column elements. It considers a shifting neutral axis of each beam element, which is updated throughout an analysis. This method was implemented in the OpenSees software environment by adding two subclasses: one for the fire beam element added to the element class, and one for the member section, in which the neutral axis is iteratively adjusted for non-uniform temperature profiles. To validate the implemented model, three benchmark case studies were sourced from literature: (1) a heated cantilever beam with an analytical solution, (2) a steel beam in a furnace with high axial and bending forces and (3) a two-dimensional steel frame in a fire with complex behaviour such as non-linear heating, restraint and buckling. For (1) the fire beam element predicts deformations identical to an analytical solution. For (2) the fire beam element method simulates deformations with good accuracy across the entire time domain relative to experimental data, and simulations in the literature using Vulcan, although with experimental deflections typically being underestimated. For (3) fire beam element predictions are compared to experimental data and models developed in CEFICOSS, ABAQUS, SAFIR and LS-DYNA. Trends are typically accurately captured, with percentage differences varying. Runaway failure is predicted with 2 min of experimental data. A sensitivity analysis of the fire beam element model on mesh size of elements and fibres showed the runtime to be more sensitive to the number of elements than the number of fibres per element.

This article proposes a new kind of continuous composite beam that consists of steel box-girder and ultra-high-performance concrete waffle slab. The ultra-high-performance concrete helps increase the ultimate capacity and span of structure while reducing the risk of cracking that occurs with ordinary concrete. In order to investigate the mechanical properties of this new type of composite structure, two scaled specimens were designed and tested. One was a steel–ultra-high-performance concrete continuous composite beam, whereas the other, as a control specimen, was a prestressed steel-concrete continuous composite beam. The test results indicate that the bending capacity of steel–ultra-high-performance concrete continuous composite beam is 1.2 times that of steel-concrete continuous composite beam; the cracking strength of steel–ultra-high-performance concrete continuous composite beam is larger than 20 MPa, much higher than the conventional one; the crack development pattern of steel–ultra-high-performance concrete continuous composite beam has its own characteristics, and the cracks appeared in ultra-high-performance concrete slab dominated by micro-cracks with smaller length are numerous and intensive. A finite element model was developed to predict the behavior of steel–ultra-high-performance concrete continuous composite beam. Comparing the numerical and experimental results indicates that, generally, the numerical model can simulate the structural behavior of steel–ultra-high-performance concrete continuous composite beam reasonably. Based on the numerical model, a series of parameter analyses were performed, which indicate that the strength grade of steel, web, and bottom plate thickness play an important role in improving the bending capacity of steel–ultra-high-performance concrete continuous composite beam; the axial tensile strength of ultra-high-performance concrete, rib, and top plate height of ultra-high-performance concrete slab can enhance the bending capacity to a certain extent.

Ductile shear connectors are often applied in timber-concrete composite beams. The relative interface slip of such kind of composite beams will affect the mechanical performance of the composite beams and result in structural nonlinearity. Gamma method which adopts effective bending stiffness to reflect semi-rigid connection is recommended in Eurocode 5. The effective bending stiffness is irrelevant to external loads and calculation points of the composite beam. However, actual bending stiffness distribution along the beam is variable due to that shear connectors are subjected to different shear force. In order to verify the accuracy of gamma method, four-point bending tests of a total of three glulam-concrete composite beams with lag screw connectors and one pure glulam beam were conducted in this article. The failure mode, bearing capacity, and load–deflection relationship were investigated in the experiment. Meanwhile, push-out tests of composite beams were also conducted for determination of the force–displacement relationship of ductile shear connectors. Then, numerical simulation using beam-truss model was established for investigation on the mechanism of composite beams. Finally, theoretical analysis of composite beams considering the effect of interface slip was also presented. Comparing results from gamma method with the presented method, it is shown that both methods can calculate deflection at serviceability limit state with high precision. However, non-uniform distribution of actual bending stiffness cannot be reflected by gamma method.

This work presents an experimental study on the flexural behavior of steel tube slab composite beams subjected to pure bending. The main design elements considered in the work are the flange thickness, reinforcement ratio of high strength bolts, spacing between the tubes, and transverse patterns of the tube connections. Based on nine flexural experiments on simply supported steel tube slab specimens, the failure process and crack development in steel tube slab specimens, and their load–deflection curves are investigated. The results of the laboratory tests show that the welding of the bottom flange significantly improves the flexural capacity of the steel tube slab structure. In addition, a lower concrete’s compressive strength improves the ductility of the steel tube slab specimens. Moreover, the flexural capacities predicted from the design guidelines are in good agreement with the experimental test results. Finally, based on the numerical simulations using the ABAQUS software, a numerical model is established to further investigate the effect of the additional parameters on the flexural capacity of steel tube slab structures. The numerical results suggested that the diameter of the steel bolts and the reinforcement ratio have a limited effect on the flexural bearing capacity of the steel tube slab beams, and the ultimate bearing capacity increases linearly along with increase in the diameter of the steel bolts and the reinforcement ratio in a certain range.

The vortex-induced vibration behavior and mechanism of an asymmetrical composite beam cable-stayed bridge is investigated by means of aerodynamic sectional tests and computational fluid dynamics me...

Externally post-tensioned tendons can cause an initial compressive stress in steel–concrete composite sections at the hogging moment region, and then a part of the tensile stress in the concrete fl...

Steel-concrete composite beams have been extensively used in buildings and bridges in recent years to combine these two construction materials. The behavioral characteristics of steel-concrete comp...

This article proposes a two-stage damage identification method to identify the location and extent of multiple damages at individual layers in laminated composite beams. In the first stage, the dam...

Strengthening of bridge superstructures composite beams with external post-tensioned tendons is a good technique for strengthening the existing structures. In this study, a numerical model is illustrated to study the nonlinear simulation of composite beams stiffened with externally post-tensioned tendons. The accuracy of the developed numerical model is validated using comparisons between the numerical and existing test data. The influence of various strengthening parameters is investigated, which include draped versus straight tendons, tendon length, the effect of post-tensioning on reinstating the flexural behavior of an overloaded beam, tendon eccentricity, and the degree of shear connection. A good agreement between the proposed model and the test data is obtained. The results demonstrate that at the same tendon eccentricity, the trapezoidal profile shows better behavior for the strengthened beams. However, more ductility is obtained when using the straight tendon profile. Applying post-tensioning through the beam of full length helps to reduce the creation of fatigue cracks, which always start at stress raisers, and subsequently increases the fatigue life of the composite beam. Also, the external post-tensioning effectively maintains the flexural behavior of the overloaded strengthened beam after unloading in comparison to the un-strengthened beam. It is observed that 80% degree of shear connection or higher is recommended to obtain the desired performance of the external post-tensioning force for strengthening composite beams.

This article presents an extensive experimental and numerical study aimed at the evaluation of the thermo-structural response of composite beams with composite slabs. Two full-scale fire tests were carried out on simply supported composite steel-concrete beams with steel sheeting perpendicular and parallel to the steel joist, respectively. Both specimens were observed to fail by developing large displacements. Concrete crushing at the mid-span, debonding of the profiled sheeting and spalling of the fire protection were observed during both tests. A three-dimensional finite element model was developed in ABAQUS, and its accuracy was validated against the experimental measurements collected as part of this study. The model was then used to perform a parametric study to determine the influence of the degree of shear connection, load ratio and design fire rate on the structural response of composite beams at elevated temperatures. These results, together with experimental data available in the literature, were used to evaluate the ability of European guidelines to predict the critical temperature of composite beams. It was shown that predictions from Eurocode 4 were safe and provided conservative estimates for most cases.

Composite beams consisting of pultruded glass fibre-reinforced polymer (GFRP) I-beams and ultra-high-strength fibre-reinforced concrete (UFC) slabs have been developed for use in short-span bridges. Fibre-reinforced polymer bolts (fibre-reinforced polymer threaded rods) and epoxy adhesive were used to connect the UFC slab to the GFRP I-beam. The authors conducted material tests and large-scale static bending tests at room and elevated temperatures (less than 90°C) to investigate the flexural behaviour of GFRP-UFC composite beams subjected to elevated temperature. The test results demonstrated that the mechanical properties of the GFRP I-beams, fibre-reinforced polymer bolts and epoxy adhesive were significantly deteriorated at elevated temperatures due to the glass transition of their polymer resin matrices. As a result, the stiffness and ultimate flexural capacity of the GFRP-UFC composite beams under elevated temperatures were significantly reduced. More than 85% of the flexural capacity of the GFRP-UFC composite beams was retained up to 60°C but that was decreased to 50% at 90°C. Fibre model analysis results confirmed that the stiffness of the GFRP-UFC composite beams is not significantly affected by actual hot environments, where there is a moderate temperature gradient across the beam cross-section.

In order to investigate the mechanical behavior of the partially concrete encased composite beam under hogging moment, static loading tests were conducted on one conventional composite beam and three partially concrete encased composite beams. The results show that partially concrete encased composite beams have higher stiffness and flexural capacity under hogging moment as compared with conventional composite beams. It is also found that the concrete encasement is able to enhance the local bucking resistance of the steel beam and effectively reduces the propagation speed of crack width under hogging moment. By comparing different partially concrete encased composite beams, it is indicated that the stiffness and flexural capacity of partially concrete encased composite beams increase with the increase in reinforcement ratio of the concrete slab. Also, with the increase in the reinforcement ratio of the concrete slab, the distribution of cracks on the slab is denser and the propagation speed of crack width reduces. In addition, the calculation methods in both European code and Chinese code can well predict the crack width on the concrete slab, and the ultimate flexural capacity predicted from the simplified plastic theory in Eurocode 4 is in good agreement with test results.

This paper presents an investigation on behaviour and design of composite beams with stiffened and unstiffened web openings. The composite beams were simply supported and had profiled steel sheeting oriented transversely to the steel beams. Nonlinear 3-D finite element models were developed to analyse the inelastic behaviour of composite beam components comprising the steel beam, concrete slab, profiled steel sheeting, headed stud shear connectors, reinforcement bars as well as interfaces among these components. In addition, the load-slip characteristic of the headed stud shear connectors in composite slabs with profiled steel sheeting were carefully incorporated into the finite element models. The finite element models of the composite beams have been validated against published experimental results. The composite beams had different moment-to-shear (M/V) ratios at the openings, stiffened and unstiffened web opening sizes, web opening locations, profiled steel sheeting, shear connections, beam lengths, concrete slab strengths and steel beam strengths. The ultimate loads of the composite beams, load-deflection relationships and modes of failure of the beams were predicted from the finite element analysis and compared well against the test results. Furthermore, the variables that influence the composite beam behaviour and ultimate load comprising different stiffened and unstiffened web opening sizes, M/V ratios at openings, web opening locations, beam lengths, concrete strengths and steel beam strengths, were also investigated in an extensive parametric study. It is shown that the ultimate loads of composite beams with stiffened web openings with horizontal stiffeners located above and below the openings, having an opening height equal to 0.6 the steel beam depth, can be considerably increased compared with that of unstiffened openings. It is also shown that the increase in structural steel strength has a remarkable effect on the composite beam ultimate loads. In addition, the ultimate loads of the composite beams with stiffened and unstiffened web openings predicted from the finite element analysis were compared with the design ultimate loads calculated using the Eurocode 4 and technical report SCI P355 published by the Steel Construction Institute for composite beams with profiled steel sheeting and rectangular stiffened and unstiffened web openings. Generally, it is shown that the design ultimate loads accurately predicted the ultimate loads of the composite beams within an average of 6% difference from the ultimate loads predicted using the finite element analysis.

This paper presents the structural response of timber-concrete composite (TCC) beams predicted by finite element models (i.e. continuum-based and 1D frame) and manual calculations. Details of constitutive laws adopted for modelling timber and concrete are provided and application of the Hashin damage model in conjunction with continuum-based FE for capturing failure of timber under bi-axial stress state is discussed. A simplified strategy for modelling the TCC connection is proposed in which the connection is modelled by a nonlinear spring and the full load-slip behaviour of each TCC connection is expressed with a formula that can be directly implemented in the general purpose FE codes and used for nonlinear analysis of TCC beams. The developed FE models are verified by examples taken from the literature. Furthermore, the load-displacement response and ultimate loading capacity of the TCC beams are determined according to Eurocode 5 method and compared with FE model predictions.

The behaviour of composite steel-concrete beams subjected to pure flexure and the presence of flexure and shear is fairly well understood and provisions do exist in international codes of practice for their design, however in most instances the influence of the concrete slab is not included in the strength design of the composite beam in shear. Combined internal actions including the presence of torsion and flexure have also been considered of late. These actions combine to occur in edge beams and curved composite beams and thus are of significant practical interest. Of increasing interest has become the presence of axial force and flexure in composite beams. These internal actions need to be considered in the design of raking beams of stadia, elevated approach spans for bridges and interchanges and in the design of integral abutment bridges and cable stayed bridges. Furthermore, composite beams in floor systems for braced multi-storey buildings are often required to resist axial force, flexure and shear force. This paper considers the effects of the presence of axial force in conventional composite beams. The effects of different forms of axial force and flexure combinations are considered in this paper. An analytical treatment, experiments and design approaches are given in this paper which is useful for structural engineers. Furthermore research in this area is also discussed. This paper will also present the results of an extensive experimental series to study the behaviour of high performance steel sections subjected to transverse impact loads which are able to simulate either a collision or blast. The experimental program has considered both mild structural steel and stainless steel hollow sections both filled and unfilled being tested. The purpose of the tests was to identify the potential advantages of using concrete infill to increase the energy absorption capability of steel hollow sections.

This paper presents recent advances in the design of steel and composite beams with web openings for full integration with building services. The conventional design approaches, such as ‘ Tee Section Approach’ and ‘ Perforated Section Approach’, are provided as an introduction to the topic. The key findings of a comprehensive finite element investigation into the structural behaviour of steel beams with web openings of various shapes and sizes are presented, and a generalized design rule with a set of moment-shear interaction curves based on the finite element results is also developed for practical applications. It should be noted that based on three structural parameters, namely, the shear utilisation ratio, v, the coupled moment capacity ratio, m̄, and the coupled shear capacity ratio, v̄, the load carrying capacities of steel beams with web openings of various shapes and sizes are obtained readily through the use of the proposed moment-shear interaction curves. Moreover, an advanced finite element study on a composite beam with a pair of large rectangular web openings is also presented, and the structural behaviour of the perforated composite beam with deformable shear connectors of different deformation characteristics is examined. It is found that both the stiffnesses and the resistances of shear connectors are very important to the load carrying capacities of the perforated composite beams. The maximum difference in the load carrying capacities of the perforated composite beams with different types of shear connectors is shown to be around 15%, reflecting the differ1ent deformation states of the composite beams at failure. Moreover, large pull-out forces are also induced in those shear connectors in the vicinity of the web openings which have been neglected in the past. As the values of these pull-out forces are found to be comparable to the shear resistances of the shear connectors adopted in the models in some cases, such forces should be considered properly in design.

An approximate analysis method was presented for the analysis and design of a simply supported composite beam with partial interaction. To solve the governing differential equation in linear elastic partial interaction theory, the internal axial force was approximated by Fourier series. In case studies, the internal axial force, slip and displacement of the beam were obtained for some load cases such as temperature load, end moment, point load and uniformly distributed load. From the study for convergence of the approximate solution, the relative error for the displacement was converged below about 0.1% at more than the fifth order of Fourier series. This method can be applied to arbitrary loading conditions. Also, the results are sufficiently accurate for determining the behavior of the composite beam with partial interaction for the design purpose.

A methodology has been developed for the continuous composite beams to predict the inelastic bending moments (considering the cracking of concrete) from the elastic moments (neglecting the cracking) by using the neural networks. The proposed neural network models predict the inelastic moment ratios (ratio of inelastic moment to elastic moment) at the supports of a span. Nine significant structural parameters have been identified governing the inelastic moment ratios. Six neural networks have been presented to cover the entire practical range of the beams. The proposed neural networks have been validated for a number of beams with different number of spans and the errors are shown to be small for practical purposes. The methodology enables rapid estimation of inelastic moments. The methodology can easily be extended for large composite building frames where a very significant saving in computational effort would result. The feasibility of the methodology for building frames has been demonstrated by considering a single story frame.

Experimental results for eleven continuous composite beams of steel and concrete are presented in this paper, which includes laws of deflection and slip between the concrete and steel. Governing differential equations of slip and deflection for simply supported composite beams with different boundary conditions and different loads are established, and a set of numerical expressions for slip and deflection of continuous composite beams are established by the superposition method as well. The deflection and slip of seventeen continuous composite beams are calculated by the numerical expressions. The calculated results show good agreement with the experimental results. The numerical results show that the slip of continuous composite beams increases and approaches the slip of sandwich panels without shear connectors. At the same time, the degree of shear connection influences deflection to a certain extent. The degree of shear connection influences deflections little at full shear connection and the increment of deflection caused by slip is less than 5% when the degree of shear connection is between 60 to 100%. When the degree of shear connection is between 80 to 140%, the strain in the lower flange of the steel beam at the internal-support is influenced little.

Steel-concrete composite flooring systems using steel sections with tapered webs are very attractive from an economical point of view, combining efficient use of steel, wide spans, rapid erection and easy access for services. However, the full economic exploitation of the composite tapered beam solution is inhibited by the limited understanding of certain aspects of its behaviour. One of the most pressing needs is for a better understanding of the local buckling behaviour of the relatively deep slender web at changes of slope in the lower flange. A design formulation has been developed which produces a very simple test of the need for stiffeners. This paper describes the derivation and behaviour of this design model. After that, a calibration of the model against some experiments and a parametric study is presented.