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Composite structures with prefabricated concrete slabs and bolted shear studs can enhance the effectiveness and sustainability of construction. In this research, non-shrinkage cement grout is proposed to be filled between high-strength fully threaded bolt shear connectors and a prefabricated slab. Six static push-out tests are performed with different bolt dimensions and different pretension forces on the bolts to study the behavior of bolted shear studs. Finite element models for bolted shear connectors using ABAQUS/Explicit solver are developed, and they matched well with experimental results. Moreover, a Parametric study is conducted to investigate the effects of grout strength, bolt diameter, length-to-diameter ratio, bolt preloading, and bolt material type on the performance of shear connectors. Finally, the results of the parametric analysis are compared to the current design codes and previous researches and more precise equations for predicting the capacity and stiffness of bolted shear studs are proposed. [ABSTRACT FROM AUTHOR]

• A state-space-based mixed finite element method is established for dynamic analysis of composite beams. • This method is capable of dealing with both transversely multi-layered and axially jointed composite beams. • Stress singularities near the interfaces are resolved by ensuring both displacement and stress continuities across different materials. • Simultaneous arrangement of displacements and stresses provides reliable simulations of boundary conditions at both ends. A novel mixed finite element method is developed and implemented for analyzing the vibration and buckling behavior of general composite beams which consists both transversely layered and axially jointed materials. The governing state-space equations are derived using the Hamilton's principle, where both displacements and stresses are treated as fundamental variables. This semi-analytical method uses transfer relations in the transverse direction and finite element meshing in the longitudinal direction, overcoming the difficulties for general composite beams analysis and providing computational efficiency and analyzing flexibilities. The developed mixed finite element model ensures continuity of both displacements and stresses across the material interface, thereby resolving interfacial stress singularity issues and offering more reliable simulations of boundary conditions at both ends. The proposed method is formulated and validated for the free vibration and buckling analysis of general composite beams. Additionally, it is observed that material properties such as Young's modulus and density, as well as the stiffness of the interface connecting layers, have significant effects on the free vibration and buckling responses of the composite beams. Analysis of periodically distributed and bi-directional composite beams demonstrates the versatility of this method in handling two types of combination forms. The proposed method serves as a valuable reference for obtaining accurate vibration and buckling results while ensuring stress-compatibility for composite beams in practical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Steel-concrete composite constructions are of particular interest due to their properties such as lightweight, fast construction rate, and higher load carrying capacity, which may be enhanced by utilizing cold-formed steel rather than hot-rolled steel to get lightweight floor system. The structural behavior of hybrid composite beams has been studied through experimental testing and finite element analysis. The beams are made in the form of a single T-beam by joining a concrete slab and a mono-symmetric cold-formed section (CFS). The CFS has two flanges: the upper is shaped like a Y or a T, and the lower is hollow and rectangular in shape. By partially embedding the upper steel flange into the 1000 mm-wide concrete slab, the composite action was established. Sixteen finite element models were used in the finite element models' evaluation process, and eight composite beam specimens underwent a four-point loading flexure tests. Principal characteristics, like the CFS's upper (Y or T) flange with and without vertical web stiffeners, were investigated. The load-carrying capacity and failure mechanisms of each specimen were measured, recorded, and confirmed by the FEA results. The ultimate load-carrying capacity of the composite section was 120 % higher with the Y-beam CFS than with the T-beam CFS. Additionally, adding stiffeners increased the local buckling resistance of the CFS and increased the beam's load-carrying capacity by about 105 %. The FEA results showed that increasing the slab thickness increased the section moment capacity by about 123 % and using a flange thickness bigger than web thickness could increase the section moment capacity than using a flange thickness smaller than web thickness CFS beam thicknesses by about 109 %. • The behavior of Single-T Composite CFS beams under flexure was studied. • The stiffeners provided sufficient restraint for the web of T-WS and Y-WS specimens' behavior against local buckling issues. • Stiffeners increased the section load capacity, also affects the specimens' deflections. • increasing slab thickness is highly effective and could enhance the section load capacity. [ABSTRACT FROM AUTHOR]

In this paper, a novel steel fibre-reinforced concrete (SFRC) dowel connection without traditional steel bar reinforcement is proposed for steel-concrete composite beams. Push-out tests on thirty-six specimens were conducted to investigate the shear strength and ductility of SFRC dowel connections with varying dowel sizes, concrete densities, fibre content and type. Even without the presence of reinforcing bars, the SFRC dowels were able to resist substantial loads and maintained a ductile load-slip behaviour. The shear strength of SFRC dowels increased with an increase in the fibre content, dowel size, and concrete density. Further, dowels with higher steel fibres content exhibited enhanced ductility, displaying a near elastic-plastic load-slip behaviour, with an ability to resist up to 80 % of the ultimate load even at 6 mm slip. A unique analytical model to predict the ultimate load and the load-slip curve is proposed in this study. The model was able to predict the ultimate load to within 6 % of test results, on average, while the mean load at 6 mm slip was predicted to within 3 % of the test results, with standard deviation of 17 % and 13 % respectively. The general shape of the load-slip curve was also well predicted. The study also proposes simplified equations, which predicted the shear strength of SFRC dowels to within 2 % of the test results with a standard deviation of 13 %. • Novel SFRC shear connectors were developed and the performance was compared with traditional dowel connections. • Push-out tests on 36 SFRC dowel connections showed improved shear strength and ductility without traditional rebars. • SFRC dowel connection strength increased linearly with fibre content, dowel size, and concrete density. • An analytical model and simplified equations were developed which accurately predicted SFRC dowel connection behavior. [ABSTRACT FROM AUTHOR]

Steel-concrete composite beams with shear studs providing composite action between the concrete slabs and steel beams are widely used in modern steel-framed building construction. Three-dimensional finite element modelling has been a viable option for investigating the fire behaviour of composite beams. Although many finite element models are available in the open literature, most of them are simplified models verified by limited test data. Meanwhile, early test data often did not have all the required information for finite element simulation, and some assumptions need to be made. But more detailed test data are now available in the open literature for steel-concrete composite beams, which can be used to develop a generalised finite element model. In addition, National Institute of Standards and Technology has proposed new stress-strain models for steels at elevated temperatures, which can be compared with the more widely adopted Eurocode 4 steel material models in simulating composite beams. Accordingly, this paper selected 22 specimens, including two reinforced concrete slabs, 12 composite beams with reinforced concrete slabs, two composite slabs with profiled steel sheeting, two steel-concrete composite push test specimens with profiled steel sheeting, and four composite beams with profiled steel sheeting, from nine references to verify the developed finite element model. The proposed finite element model can capture different failure modes of composite beams, such as steel yielding/local buckling, concrete cracking/crushing, debonding of profiled steel sheeting, and stud fracture, which is crucial to comprehend the composite beam behaviour at elevated temperatures. • A detailed FE model was developed for composite beams exposed to fire. • The constitutive models of steel and concrete materials at elevated temperature were considered. • Different types of failure modes of composite beams exposed to fire can be well predicted by the FE model. [ABSTRACT FROM AUTHOR]

The conventional challenges of 3D-printed concrete reinforcement have yet to be resolved, and employing Engineered Cementitious Composites (ECC) as a 3D-printed prefabricated formwork seems to be a viable solution. This study conducted experiments on the flexural behavior of composite beams with variations in fabrication processes, fine aggregate replacement ratio, single-layer printing height of side panel, and bottom ECC printing height. Additionally, the finite element analysis which considered the thickness of the side panels and the strength of post-cast core concrete was also performed. The findings indicated that composite beams formed by 3D-printed ECC exhibited superior flexural capacity and peak displacement in bending compared to beams constructed using cast formwork. The 3D-printed composite beams with a ratio of the bottom ECC height to the beam height of 0.2 and the side panel thickness of 30 mm, demonstrated bearing capacities similar to reinforced concrete beams with reinforcement ratios ranging from 0.3% to 0.4%, and exhibited larger peak displacements. Furthermore, the improvement of bearing capacities in composite beams through increased side panel thickness and core concrete strength was limited by the bonding strength at the interface between the ECC formwork and core concrete. • 3D-printed ECC formwork and post-cast core recycled concrete composite beams were designed and verified. • Different printing parameters were assessed for 3D-printed composite beam with prefabricated ECC formwork. • 3D-printed composite beams with ECC formwork exhibited higher load-bearing capacities and displacements. [ABSTRACT FROM AUTHOR]

The steel-concrete-fiber-reinforced polymer (FRP) composite structure was proposed in this paper, where FRP and steel were designed in the tensile region and compression region of concrete-filled steel tube (CFST) beams in the form of sheets, bars, and tubes, respectively, with the expectation of improving the performance of the structure. Epoxy mortar was used to modify the interfacial properties and part of the normal concrete (NC) was replaced by seawater sea sand concrete (SWSSC). A total of 10 FRP-SWSSC-steel composite beams were fabricated and subjected to four-point bending tests, and they exhibited the failure modes of local buckling. Reinforcing the tensile region significantly improved the flexural performance of the composite beams since the steel tube buckling and the concrete cracking were limited, and the flexural capacity of the composite beams was increased by 18.3%− 28.6% by designing FRP sheets or steel bars in the tensile region. Reinforcing the compression region had little effect since the existence of the in-built tube divided the monolithic concrete, and the confinement on the core concrete was not fully utilized. Based on research experience with CFST beams, a flexural strength model for FRP-SWSSC-steel composite beams was established. • The four-point bending test of FRP-SWSSC-steel composite beams was conducted. • Composite beams with FRP sheets showed the best flexural capacity. • Composite beams with steel bars showed the best deformation capacity. • Effects of reinforcing compression region on flexural capacity were limited. • A flexural strength model for FRP-SWSSC-steel composite beams was established [ABSTRACT FROM AUTHOR]

This paper develops a novel class of timber-cardboard sandwich (TCS) panels, consisting of low-cost timber facings and a block-laminated corrugated cardboard core. Experimental and analytical studies are conducted to characterise the flexural performance of TCS beams made from recycled or waste materials. TCS beams made from scrap cardboard cores have the exceptional characteristic of being made mostly from waste, up to 91% by volume or 76% by weight, and are demonstrated to have equivalent performance to beams made with recycled cores. TCS beam flexural behaviour is found to be primarily governed by timber face sheets, with very strong composite action and no observed core shear or debonding failure. The strength, stiffness, and dominant failure mode of TCS beams are thus shown to be accurately predicted using composite sandwich beam theory and cross-sectional analysis. TCS beam bending strength is also found to be significantly higher than conventional foam-core structurally-insulated panels with comparable densities, making them highly viable as a bio-based structural alternative. These research findings enhance the capacity and confidence by which cardboard can be used as a construction feedstock, supporting societal progression toward a greener and more circular economy. • Novel timber-cardboard composite beams formed by bonding timber facings and recycled/waste cardboard cores. • The role of cardboard source, continuity, wall style, and flute profile are explored. • Beams achieve strong composite action with performance governed by timber facings. • Analytical models accurately predict load capacity and bending stiffness. [ABSTRACT FROM AUTHOR]

A redesign was attempted for the concrete-filled double-skin tube subjected to bending, and by adjusting the core tube position and applying carbon fiber-reinforced polymer (CFRP) sheets or steel bars in the tensile region, it was hoped to delay the cracking of the concrete in the tensile region. Epoxy mortar was used to modify the interface. Seawater and sea sand has been successfully applied from reinforced concrete beams to concrete-filled steel tube beams, benefiting from the corrosion-resistant properties of CFRP and epoxy mortar. The four-point bending test parameters included the type of core tube, the number of CFRP layers, and the diameter of the steel bars. The beams with FRP sheets exhibited better flexural capacity and residual stiffness, while the brittle fracture of FRP led to major crack in concrete. The beams with steel bars exhibited better initial stiffness and the cracks in concrete were more uniform in width. When the layers of CFRP or the diameter of the steel bars was increased, the flexural capacity of the composite beams increased by 11.0%-13.6% and 7.0%-9.1%, respectively. The enhancements provided by the core tubes were small, and the design of the composite beams should be considered from various perspectives. The moment-curvature relationships, ultimate states, and flexural stiffness were defined by considering concrete cracking, FRP fracturing, and steel buckling. Several formulas for calculating flexural stiffness in the code were evaluated in combination with the test data. • CFRP-steel composite beams with seawater sea sand concrete core were presented. • Flexural performance, strain and deflection curve distribution were evaluated. • Designing FRP in tensile region is more effective in improving mechanical properties. • A flexural stiffness calculation model for the composite beams was established. [ABSTRACT FROM AUTHOR]

Openings in composite beams can be used to install ducts and utility pipes without increasing the story height. The shear strength of the composite beams is decreased as a result of these openings because the overall cross-sectional area is reduced, which causes the concentration of stresses and the propagation of cracks around the opening corners. This study focuses on restoring the structural characteristics of composite beams cosisting of high-strength self-compacting concrete (HSSCC)-encased steel beams with large web openings utilizing internal steel plates and a steel box. An experimental program consisting of six composite HSSCC beams was prepared to investigate the effects of the length of the strengthening steel plates (320, 500, and 680 mm) on ultimate loads, stiffness, and absorbed energy. All steel plates had a constant thickness of 4.0 mm, while all composite beams have been tested under a four-point loading system. Additionally, a comparison was made between strengthening the HSSCC composite beams with steel plates and a steel box of the same length (320 mm). The installation of steel plates with a thickness of 4.0 mm and a length of 680 mm exhibited the highest ultimate load among all beams with web openings of 158.8 kN, with an improvement ratio of 116% with respect to the un-strengthened specimen with web opening. Moreover, a three-dimensional (3D) finite element model was created using the ABAQUS package to simulate the response of the experimentally tested specimens. Prior to performing a parametric study, the numerical model's results were verified using the experimentally recorded data. The parametric study examined the impact of increasing the thickness of the steel box and strengthening plates from 4.0 mm to 8.0 mm on the shear performance of HSSCC beams with large web openings. • The shear response of HSSCC-encased steel beams with large web openings was investigated. • Effects of the length of the strengthening steel plates (320, 500, and 680 mm) on were considered. • A comparison was made between strengthening the HSSCC beams with steel plates and a steel box. • The installation of steel plates with a length of 680 mm exhibited the highest ultimate load. • Non-linear 3D finite element model (FEM) was constructed using ABAQUS/standard. [ABSTRACT FROM AUTHOR]

• A closed-form SE formulation for metamaterial beams with the host PICB is proposed. • An approach combined the SE with WFE method is applied to metamaterial beams. • A benchmark test validates the accuracy and efficient of this approach. • Discussing bandgap behaviors covering the position, width and attenuation capacity. • Parameters cover absorber arguments, lattice constant and shear connector stiffness. Elastic metamaterials with local resonant components exhibit unique bandgap behavior that can be utilized to control the vibration and noise of mechanical structures. This study aims to introduce the bandgap characteristics into the vibroacoustic control of partial-interaction composite beams (PICBs) widely adopted in civil engineering, aviation, and marine fields. Vibration absorbers are arranged periodically on the beam to generate a bandgap in PICBs, thereby transforming a conventional PICB into a metamaterial beam. An analytical approach is proposed to establish the spectral element (SE) matrix of a metamaterial beam based on the Timoshenko–Ehrenfest beam theory. Specifically, the governing equations of motion for PICBs follow Hamilton's principle. This model considers the effects of shear slip between two-layer sub-beams, shear deformations, and rotary inertia. The SE matrix of PICBs is then constructed and applied to obtain the SE matrix of the metamaterial beam by assembling the SE matrix of the vibration absorbers. Subsequently, the wave finite element (WFE) method is employed to predict the dispersion curve of the infinite metamaterial beam and the dynamic response of the finite metamaterial beam. In a benchmark example, the complex band structure and transmission indicated by the proposed approach are validated compared to those calculated by evaluation formulas of the literature and the finite element method. Lastly, the bandgap behavior for the vibration absorber parameters, lattice constants, and shear connector stiffness is investigated based on the defined dimensionless parameters. These results are valuable for optimizing vibration and noise reduction in PICBs equipped with attached vibration absorbers. [Display omitted] [ABSTRACT FROM AUTHOR]

To evaluate the behaviour of a single timber-concrete composite (TCC) T-beam, a simplified 2D finite element (FE) model in Abaqus is developed and validated using experimental tests and the Gamma method given in Annex B of EN 1995–1-1. The shear connection used in the beam consist of perfobond connectors, which are adhesively bonded to the timber beam. In the developed model, beam and shell finite elements have been used to simulate/reproduce the timber beam and the concrete slab, respectively. These have then been connected using connector elements which incorporate the mechanical behaviour of the tested shear connections, obtained in a previous research. After the successful validation of the FE model, this is used to further analyse different parameters such as: i) different number of connections (varying from 8 to 20), ii) different types of loading (point load, distributed load and line load), iii) different concrete slab widths and iv) connection models with elastic perfectly plastic behaviour applied to TCC T-beam and a 5 m by 5 m floor system. The results of the conducted study provide an in-depth understanding of the effect and impact of the investigated parameters which can support a future optimisation of the structural solution. Moreover, the results show that the use of a simplified 2D model can support designers to overcome the limitations of analytical approaches, such as the Gamma method, to analyse large spacing and to take benefit of bidirectional effects (load sharing) if analysed as a whole instead of a single T-beam. • Development of a simplified 2D FE model of a timber-concrete composite floor system. • Determination of optimal number of connections for maximum composite action. • Comparison of T beam and floor system. • Presentation of load sharing on full floor system. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of full-scale steel-concrete composite beams using truss-type shear connectors. The connector geometry is original and effective. It is made from traditional steel rebar used in reinforced concrete structures. When compared with the stud-shear connector, the truss-type shear connector has several advantages, including low cost, ease of installation, and high resistance, among others. Previous research on the truss-type shear connector has made use of the popular push-out test, a reduced-scale physical model. However, for a better understanding of the truss-type shear connector behavior and to make it reliable for engineering practice, the truss-type shear connector must be studied under more realistic working conditions. In that sense, this research presents an experimental study in which three full-scale tests of steel-concrete composite beams, using truss-type shear connectors, are carried out. In the experimental program, different shear connection degrees are considered. The experimental results showed that when the shear connection degree is decreased, there is a rise in slippage between the steel beam and the concrete slab and a drop in the ultimate load. In the tests, the measured values of the uplift separation between the steel beam and the concrete slab were in compliance with the Eurocode-4 specifications. The failure modes of the specimens were characterized by excessive yielding of the steel beam or by a combination of this and the failure of the connections. The resistance of the truss-type shear connector was successfully predicted using the equation developed by the authors. • Truss-type shear connectors are evaluated experimentally in full-scale steel-concrete composite beams. • It was experimentally found that the truss-type connector complies with Eurocode-4 specifications. • An equation for the shear resistance strength of the truss-type connector was verified experimentally. • The effectiveness of the truss-type shear connector and its potential to applications were demonstrated in this research. [ABSTRACT FROM AUTHOR]

Bridge structures in cold climates face significant challenges due to freeze-thaw cycles and salt-induced corrosion. This study investigates the degradation mechanisms of the negative bending behavior of steel-concrete composite beams using normal concrete (NC) and ultra-high performance concrete (UHPC) under salt freeze-thaw cycles (SFTC), considering the impact of different stud arrangements. The results indicate that UHPC significantly enhances the cracking performance in the negative bending region of the composite beams and demonstrates high resistance to SFTC. Before undergoing SFTC, the cracking moment of the UHPC beams increased by an average of 210.5%, and stiffness by 37.3%, compared to the NC composite beams. After 150 SFTCs, the NC beams showed a significant decline in performance, with a 62.1% reduction in cracking moment, a 6.2% decrease in load-carrying capacity, and a 5.6% reduction in stiffness. In contrast, the flexural performance of the UHPC beams was almost unaffected, with only a 17.5% reduction in cracking load. Moreover, beams with a double-row stud configuration exhibited better negative bending resistance compared to those with a single-row stud configuration. Based on experimental results and data from reference, a reasonable formula for predicting the composite beams under the effect of SFTCs was proposed and proved to have satisfactory accuracy. • 12 steel-concrete composite beams were tested under salt freeze-thaw cycles. • Subsequent residual flexural performance tests were conducted on deteriorated composite beams. • UHPC flange plates exhibit excellent performance in resisting cracking and salt freeze-thaw damage. • Increasing the number of studs is beneficial in improving negative bending performance. [ABSTRACT FROM AUTHOR]

• Effect of local buckling on the ductility of composite beams. • Plastic rotational capacity of composite beams under hogging moment. • FEM of steel-concrete composite beams. • Definition of a formula for the plastic hinge length. Lumped plasticity is one of the most commonly used approaches for the nonlinear analysis of framed structures, but its effectiveness depends on the reliability of the plastic rotational capacity. In the case of RC or steel structures, this approach is based on well-known and reliable formulations, but no specific rules have been established for steel-concrete composite structures. This paper reports the results of a detailed analysis of the nonlinear behaviour of the section and entire element of a composite beam with the goal of determining its flexural ductility. In particular, the composite beam was examined under a hogging moment that results in its worst performance due to the concrete experiencing tension and the steel compression. An FE model is used to study the element; it was considered all the features of the materials and the geometry of the section to develop a parametric analysis that enabled to study the effect of different parameters on the rotational capacities of the composite beams. This formulation considers the local phenomenon of profile buckling and the global dimensions of the composite section. Finally, the obtained results allowed to define an equivalent plastic hinge length that provides the available plastic rotation when multiplied by the plastic curvature of the cross-section. [ABSTRACT FROM AUTHOR]

• Nonlinear behavior of continuous prestressed composite beams is evaluated. • Secondary moments in continuous prestressed composite beams are significant. • External prestressing improves moment redistribution ability of composite beams. This paper evaluates the flexural performance and quantifies the secondary moments in two-span prestressed steel-concrete composite beams. A nonlinear model capable of simulating the full-range nonlinear behavior of continuous prestressed composite beams is validated against experimental results. A parametric numerical investigation is then conducted to examine the effectiveness of strengthening a continuous steel-concrete composite beam with external tendons of different cross section areas. In addition, secondary moments in continuous prestressed composite beams having different tendon layouts under symmetrical and unsymmetrical loads are investigated. The results indicate that external prestressing not only increases significantly the ultimate load-carrying capacity but also improves the moment redistribution ability of continuous steel-concrete composite beams. Moreover, the analysis shows that significant secondary moments are present in continuous prestressed composite beams throughout the loading history. It is therefore necessary to consider secondary moments in the strength design of this structural typology. [ABSTRACT FROM AUTHOR]

Abstract In this study, stress analysis of laminated composite beams is carried out by using Refined Zigzag Theory (RZT) and Peridynamic Differential Operator (PDDO). The PDDO replaces local differentiation with nonlocal integration. This makes the PDDO capable of solving the local differential equations accurately. RZT is suitable for both thin and thick beams eliminating the use of the shear correction factors. Also, RZT ensures a constant number of kinematic variables regardless of the number of layers in the beam. The governing equations of the RZT beam and the boundary conditions were derived by employing the principle of virtual work. The capability of the present approach was assessed by considering various beams for different boundary conditions and aspect ratios. It provides robust and accurate predictions for the displacement and stress components in the analysis of highly heterogeneous laminates. [ABSTRACT FROM AUTHOR]

Abstract This study presents a highly accurate, computationally efficient, and novel isogeometric beam element, named as IG - RZT (m) , whose formulation is derived by using the kinematic assumptions and " a priori " transverse-shear stress continuity conditions of mixed form of the refined zigzag theory, known as RZT (m) . Both the displacement field and geometry of the beam is approximated by using non-rational B-spline (NURBS) basis functions and the IG - RZT (m) element accommodates only four degrees-of-freedom at each control point. Since the present formulation incorporates isogeometric analysis into the RZT (m) theory, it provides various advantages for displacement and stress analysis of thin/thick composite beams such as high-order continuity representation and simple mesh refinement. Furthermore, the utilization of RZT (m) theory within the current beam formulation enables the calculation of nonlinear transverse-shear stress variations through the thickness of highly anisotropic beams without any post-processing. Various numerical analysis are performed to validate the accuracy of the IG - RZT (m) element and its wide range of applicability including beams with a resin-rich damage zone. Comparisons with analytic solutions and high-fidelity finite element models demonstrate the superior accuracy and practical applicability of the present formulation, especially making the IG - RZT (m) element as an attractive candidate for modelling delamination initiation and propagation in composite structures. [ABSTRACT FROM AUTHOR]

Highlights • Efficient FE models were developed to study the stud shear connector behavior. • The results obtained from FE analysis were verified against experimental results. • The influence of different parameters on the stud shear resistance was analyzed. • In this study an extensive experimental database of several researchers was used. • The accuracy of the AISC and EC-4 to estimate stud shear resistance was verified. Abstract In composite beam design, headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface. This paper describes the structural performance of shear connection in composite beams with profiled steel sheeting. An accurate and efficient nonlinear Finite Element (FE) model was developed to study the behavior of headed stud shear connectors welded through the deck. The concrete slab considered in this article uses profiled steel sheeting with ribs perpendicular to the longitudinal axis of the steel beam. The material nonlinearities were included in the FE model. The concrete was modeled considering a damaged plasticity model available in ABAQUS software. The results obtained from FE analysis were verified against experimental results. A parametric study was conducted to observe the effects of changing of both the stud position inside the rib of profiled steel sheeting and the concrete strength on the resistance of the stud shear connector. The shear resistance of stud connectors obtained from the FE analysis and many experimental push-out tests whose results are available in the literature were used as a database to compare with design shear resistance calculated using AISC-LRFD and Eurocode 4. It is found that the shear resistance of stud connectors, obtained from the design rules specified in these codes, in some cases is greatly underestimated, and in other cases significantly overestimated. [ABSTRACT FROM AUTHOR]

Abstract Highly flexible laminated composite structures, prone to suffering large-deflection and post-buckling, have been successfully employed in a number of scenarios. Therefore, accurate predictions of their stress distributions in the geometrically nonlinear analysis are of paramount importance for their design and failure evaluation. In this paper, for composite beams subjected to large-deflection and post-buckling, we investigate the effectiveness of different geometrically nonlinear strain approximations for the description of their nonlinear static response and for the determination of stress distributions. For this purpose, a unified formulation of geometrically nonlinear refined beam theory based on the Carrera Unified Formulation (CUF) and a total Lagrangian approach constitutes the basis of our analysis. Accordingly, various kinematics of one-dimensional structures are formulated via an appropriate index notation and an arbitrary cross-section expansion of the generalized variables, leading to lower- to higher-order beam models with only pure displacement variables for laminated composite beams. In view of the intrinsic scalable nature of CUF and by exploiting the principle of virtual work and a finite element approximation, nonlinear governing equations corresponding to various nonlinear strain assumptions can be straightforwardly and easily formulated in terms of fundamental nuclei, which are independent of the theory approximation order. Several numerical assessments are conducted, including large-deflection and post-buckling analyses of asymmetric and symmetric laminated beams under compression loadings. The numerical solutions are solved by using a Newton–Raphson linearization scheme along with a path-following method based on the arc-length constraint. Our numerical findings demonstrate the capabilities of the CUF model to calculate the large-deflection and post-buckling equilibrium curves as well as the stress distributions with high accuracy, which could be a basis to assess the validation ranges of various kinematics and different nonlinear strain approximations. Highlights • This paper investigates interlaminar stresses in composite flexible structures. • The Carrera unified formulation is used to implement refined and layer-wise models. • Different geometrically nonlinear strain approximations are investigated. • Attention is focused on carbon fiber-reinforced laminated beams in post-buckling regime. [ABSTRACT FROM AUTHOR]

Abstract We report a novel approach to control flexural waves in thin plates using metasurfaces constituted of an array of parallel arranged composite beams with their neutral planes the same as that of the host plate. The composite beams are composed of two connecting parts made of different materials, and have a thickness identical to that of the host plate. To steer flexural waves in thin plates, a rectangular zone is subtracted from the thin plate and is then filled with the designed metasurface. The time delay of flexural waves in each composite beam of the metasurface is tuned through the varying length of the two connecting components, while keeping the total length fixed. To quantitatively evaluate the time delay in each composite beam, a theoretical model for analyzing the phase of the transmitted flexural waves is developed based on both Mindlin plate theory and Timoshenko beam theory. To control the flexural waves at will, each composite beam in the metasurface is delicately designed according to the proposed theoretical model. For illustrative purposes, the refracted and focusing metasurfaces are designed and numerically validated. [ABSTRACT FROM AUTHOR]

Abstract This paper presents test results of fifteen reinforced engineered cementitious composite (ECC)-concrete beams. The main parameters investigated were the amount and type of reinforcement, and ECC thickness. All reinforced ECC-concrete composite beams tested were classified into four groups according to the amount and type of main longitudinal reinforcement used; three groups were reinforced with FRP, steel and hybrid FRP/steel bars, respectively, having similar tensile capacity, whereas the fourth group had a larger amount of only FRP reinforcement. In each group, four height replacement ratios of ECC to concrete were studied. The test results showed that the moment capacity and stiffness of concrete beams are improved and the crack width can be well controlled when a concrete layer in the tension zone is replaced with an ECC layer of the same thickness. However, the improvement level of ECC-concrete composite beams was controlled by the type and amount of reinforcement used. Based on the simplified constitutive relationships of materials and plane section assumption, three failure modes and their discriminate formulas are developed. Furthermore, simplified formulas for moment capacity calculations are proposed, predicting good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The details of a new steel-concrete composite beams with TALHGs are presented. • A series of test results are presented to demonstrate the flexural behaviour of the beam. • The impact of four key parameters is discussed. • The importance of the top concrete slab thickness is analysed. Abstract Traditional composite beams have the problem of large self-weights and require a considerable number of structural materials. In order to address these problems, this paper focuses on a new type of steel-concrete composite beam with transverse and longitudinal hidden girders (TALHGs). To investigate the flexural performance of such beams, five specimens with TALHGs were examined. The results indicate that the composite beams exhibit high flexural strength, good flexural rigidity and desirable ductility under monotonic load. Based on the test results, the influence of some key design parameters (e.g., concrete top slab thickness, concrete bottom slab thickness, the existence of a concrete bottom floor and H-shaped steel sizes) on the flexural performance of the composite beams were also evaluated. It is worth highlighting that this new design leads to significant savings in structural material demands (such as shear connectors, steel reinforcement, and concrete), which in turn saves the resource and construction cost. [ABSTRACT FROM AUTHOR]

Abstract Stainless steel is increasingly popular in construction projects owing to its corrosion-resistance, excellent mechanical and physical properties and its aesthetic appearance. The current paper is concerned with the use of these materials in steel-concrete composite beams, which is an entirely new application. Current design codes for steel-concrete composite beams are based on elastic-perfectly plastic steel material behaviour neglecting strain hardening. Whilst this is a reasonable assumption for carbon steel, stainless steel is a very ductile material which offers significant levels of strain hardening prior to failure. Therefore, current design provisions typically result in inaccurate and overly-conservative strength predictions when applied to stainless steel composite beams. The current study presents for the first time, an analytical solution for predicting the plastic bending capacity of stainless steel–concrete composite beams with either full or partial shear connection. This method is a development of the continuous strength method (CSM). Since the analytical analysis requires complex mathematical solution, a simplified analytical solution is also proposed, utilising some of the assumptions in Eurocode 4. There are no tests currently available in the literature for stainless steel-concrete composite beams. Therefore, a finite-element model is developed and validated against a number of experimental results for composite beams made from normal or high strength carbon steel. The validated numerical model is then used to investigate the accuracy of the proposed analytical solution. It is concluded that both the full and simplified analytical solutions are reliable and the simplified analytical method provides a straight forward design tool for practical engineers. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a Finite-Element (FE) numerical investigation on timber-to-timber joints and composite beams with inclined self-tapping screws (STSs) is presented. Based on past experimental data and numerical literature efforts, full 3D solid FE models of selected geometrical and mechanical configurations of technical interest are implemented in ABAQUS software package and analysed under static loading conditions. The typical push-out samples include GL24h timber members with several types (WT-T-8.2, 190 mm and 220 mm their length), layouts (2 + 2, 4 + 4, 2 + 2 X-shaped) and inclination of screws (up to ±45°). For the full-scale beam samples in bending (8 m their span), composite systems consisting of GL24h timber beam, wooden plank, spruce floorboards and STSs are investigated. There, the STS joints take the form of two-rows or X-shaped connections, respectively (45° or 90° their inclination), including four screw types and different spacing. In both the push-out and full-scale cases, simple modelling approaches are taken from the ABAQUS library and adapted to the timber-to-timber structural system under investigation, so as to explore their structural performance in the elastic and post-damage phases, up to failure. A key role in the typical FE models is assigned to input material properties and mechanical contacts, including damage constitutive laws so as to reproduce possible local failure phenomena in the timber or steel components, as well as cohesive damage interactions for the joints. The presented FE models are calibrated in accordance with past research studies, and validated – for the examined structural typology – against experimental results available in literature. Comparative calculations are hence presented, based on the collected numerical, experimental and analytical estimations for the selected samples. As shown, the examined modelling approach can reasonably capture the expected performance of timber-to-timber joints and composite systems. [ABSTRACT FROM AUTHOR]

Highlights • The fully composite beam exhibits the ductile flexural behavior. • Residual stresses do not affect the ultimate strength of the fully composite beam. • Depth of the steel girder sensitively affects strength of the fully composite beam. • The simplified models capture the moment-curvature curve of the fully composite beam. Abstract This paper focuses on the fully composite beam consisting of the U-shaped steel girder and angle connectors. Through the four-point bending tests of six full-scale specimens, the authors experimentally evaluated the flexural behavior of the fully composite beams. The specimens were intentionally varied to have different shear transfer capacities along the interfaces between the concrete slabs and the U-shaped girders and different geometries of the U-shaped girders. Test results show that all the specimens were fully composite and exhibited the favorable ductile flexural behavior. Computer models were then developed for the experimental specimens. It was found that the computer models were able to replicate the nonlinear behavior of the experimental specimens observed during the tests. Based on the computer models, parametric analyses were performed to investigate the influences of the residual stresses in the U-shaped girder, the strengths of construction materials, the geometries of the U-shaped girder and concrete slab on the strength of the fully composite beam. Beyond the computer models, simplified analysis models that are based on the assumed strain and stress diagrams and can be implemented through hand calculations were developed to capture the nonlinear moment-curvature responses of the composite beams. It is found that the results from the simplified analysis models agree well with the computer models. The simplified analysis models are thus recommended for future practice. [ABSTRACT FROM AUTHOR]

Highlights • Possible failure modes are analyzed for modular GFRP-steel composite beams. • Theoretical formulation of bearing capacity is developed for each failure mode. • Flexural failure can be the critical mode for bidirectional composite beams. • Vertical shear failure can be the critical mode for unidirectional composite beam. • Ductile failure can be achieved with ultimate capacity larger than yield load. Abstract This paper analytically formulates the ultimate capacities for various failure modes of composite beams consisting of a modular fiber reinforced polymer (FRP) web-flange sandwich deck supported by a steel girder. Pultruded FRP box sections are incorporated between two flat panels to form the web-flange sandwich deck, in which the pultrusion direction of box sections can be either parallel or perpendicular to the span direction. Such a deck can then be assembled via adhesive bonding or blind bolt connections to a supporting steel girder to form a composite beam system. On the basis of theoretical analysis of critical sections for such composite beams at ultimate states, potential failure modes are identified, including flexural failure of the steel girder yielding in tension and GFRP deck failure in compression, vertical shear failure, and horizontal shear failure at adhesive bonding at bolted connections and at webs of FRP box sections. For each failure mode, the corresponding ultimate capacity is analytically formulated; thereby, the critical failure mode and ultimate load capacity can be determined. The developed ultimate limit design approaches are validated by experimental results from the literature for such FRP-steel composite beams. [ABSTRACT FROM AUTHOR]

• The flexural behavior of steel-UHPC composite beams and the connector's shear capacity were reviewed. • Two databases of flexural tests of steel-UHPC composite beams and push-out tests were generated. • The accuracy of shear capacity prediction models of connectors embedded in UHPC was analyzed. • The failure modes of studs embedded in UHPC and steel-UHPC composite beams were discussed. Steel-Ultra-High Performance Concrete (UHPC) composite structures are a recent and innovative system with several applications. Steel-UHPC composite beams, for example, enable Accelerated Bridge Construction (ABC) due to the speed with which their components can be precast in the factory and practically installed on-site. Likewise, the improved properties of UHPC in terms of high compressive strength, ductility, toughness, and durability compared to Normal-Strength Concrete (NSC) allow for designing optimized slender cross-sections and, consequently, lower weight. Despite all the advantages offered by steel-UHPC composite beams, the study of their structural behavior began a few years ago, so there still need to be recommendations in the principal construction codes that regulate their use. In addition, review studies need to discuss the current state-of-the-art topic. This paper reviews the flexural behavior of steel-UHPC composite beams and the interaction of shear connectors at the interface through push-out tests. Two databases of push-out and flexural tests were built and discussed to address the main aspects that influence the behavior and performance of the composite system. [ABSTRACT FROM AUTHOR]

Abstract For composite cellular beams, additional deflections occur due to the loss of bending and shear stiffness at the opening positions and also due to slip in the shear connectors caused by partial shear connection. Design formulae are presented for the additional deflection of composite beams with circular openings or for cellular beams as a function of the proportionate depth of the openings. The simplified formulae are calibrated against finite element results for both cellular and solid web beams and also against measured deflections of a 15.3 m composite cellular beam test. This additional deflection is presented as a function of flexural and shear terms that are a function of the span:depth ratio. For modelling of cellular beams to determine deflections, the circular opening may be represented by an equivalent rectangular opening of length equal to 70% of the opening diameter. Highlights • Simple formulae have been developed for the additional deflection of composite beams due to circular web openings. • The method has been compared to results of a 15 m span cellular beam test • Finite element modelling is used to calibrate a simple formula for the additional deflection due to the openings • Finite element modelling included both symmetric and asymmetric cellular beam sections. • The effect of flexible shear connectors is included in a formula for the effective stiffness of a composite cellular beam [ABSTRACT FROM AUTHOR]

Dynamic instability analysis of doubly-tapered cantilever composite beams rotating with periodic rotational velocity is conducted in the present work for out-of-plane bending (flap), in-plane bending (lag) and axial vibrations. Rayleigh-Ritz method and classical lamination theory are used along with an energy formulation. Bolotin’s method is applied to obtain the instability regions. To verify the dynamic instability analysis results, time responses are investigated at different locations of the instability region by using the Runge-Kutta method. A comprehensive parametric study is conducted in order to understand the effects of taper configurations and various system parameters including mean rotational velocity, hub radius, double-tapering angles and stacking sequences, on the dynamic instability characteristics of the composite beam. The composite material considered in the present work in numerical results is NCT-301 graphite-epoxy prepreg. [ABSTRACT FROM AUTHOR]

This study evaluates the performance of the design equations given in the Australian/New Zealand bridge and steel structures design standards AS 5100.6, AS 4100 and NZS 3404.1 based on reliability analysis. For this evaluation, the following two methods were utilised: (i) a capacity factor calibration method to meet the target reliability level when there are a limited number of steel yield strength tests; and (ii) an inverse reliability analysis method to calculate the required minimum number of steel yield strength tests to achieve the target reliability level when using capacity factors provided in the design standards. The methods were applied to steel and composite members including I-beams, hollow section columns, CFST columns, and composite beams. To ensure the adoptability of imported steel for these members, structural steel that conforms to European, Korean, Japanese, American, Chinese and Australasian manufacturing standards were considered in the analyses. The results showed that, for an infinite range of manufacturing data, the capacity factors were insensitive to the different manufacturing tolerances. Furthermore, when a limited number of mechanical tests were available, a much larger number of results were needed to achieve the target capacity factor for composite members in comparison with non-composite members. Finally, when considering hollow sections used as columns, the current design equations were unable to deliver the target reliability levels for any of the manufacturing standards used internationally. [ABSTRACT FROM AUTHOR]

Steel-concrete composite beams have been widely used in modern construction industry, where headed shear stud connectors are commonly welded through profiled steel sheeting to ensure full/partial composite action between the beam and the composite slab. For such composite beams, there are complex interactions between different components, leading to different failure modes. Finite element (FE) analysis could be used to understand the fundamental behaviour of such beams. But previous FE models have adopted various assumptions to simplify the modelling of some complex interactions such as the interaction between the shear studs and concrete. Accordingly, those FE models have limitations to capture certain types of failure modes. Meanwhile, the actual forces carried by the studs and profiled steel sheeting have not been quantitatively determined. In this context, this paper aims to develop a detailed FE model for composite beams with profiled steel sheeting by considering realistic interaction between different components, fracture of the shear studs and profiled steel sheeting, as well as tensile and compressive damage in concrete. The developed FE model can satisfactorily predict the full-range load–deformation curves of the composite beams and the shear force–slip relationship of the embedded shear studs. The predictions agree very well with a wide range of test data reported in the literature. [ABSTRACT FROM AUTHOR]

In this paper, we develop a new and efficient finite element for the linear static analysis of composite beams with deformable shear connection. We adopt a 3-field mixed approach, based on the Hu-Washizu principle, combined with the enhanced strain concept. Our proposal includes the possibility of systematically choosing interpolating functions of increasing order for certain generalized stresses and for the enhanced strains. Another distinctive feature of our approach is the fact that only three generalized stresses are directly approximated. As in many mixed formulations, the degrees of freedom associated with the approximation of generalized stresses and enhanced strains can be condensed out at the element level at negligible cost, leading to discrete systems involving only the displacement degrees of freedom. For benchmarking purposes, a conventional displacement-based conforming finite element is also briefly derived. Several illustrative examples demonstrate the mixed element’s ability to perform very well on the coarsest of meshes – often consisting of a single finite element –, even when the material data exhibits a jump discontinuity in its interior, in sharp contrast with the displacement-based conforming element. This is particularly true when it comes to the estimation of generalized stresses, often the variables of most interest to designers. [ABSTRACT FROM AUTHOR]

The Refined Zigzag Theory (RZT), developed by Tessler/Di Sciuva/Gherlone is among the most promising approaches for analyzing shear-elastic composite structures today. Since its appearance many contributions have been published dealing with finite elements for laminated structures based on the efficient kinematic of RZT. For composite beam-columns C 0 -elements of different orders as well as p-type approximations are formulated and assessed. In this work a different approach is given. After establishing the governing equations in a first order differential equation system, the transfer matrix is obtained by a matrix series solution and by similarity transformation. The transfer matrix approach, in principle suited for 1D-structural elements such as beams, disks, circular plates and rotational shells, has been successfully applied in the past. Sometimes this approach exhibits numerical instabilities. The well-known relations between the transfer- and stiffness matrix are invoked to circumvent this drawback. The dynamic stiffness matrix and the load vector are obtained by reordering and partially inverting the submatrices of the transfer matrix. The results, which are obtained by one finite element only, are in agreement with available analytical and numerical solutions. [ABSTRACT FROM AUTHOR]

A novel method for nonlinear parameter identification of partially composite beams using long-gauge strain responses is proposed in this paper. Firstly, theoretical analysis shows that neutral axis position of timber beam and concrete slab can be estimated by measured long-gauge strain and material properties. Then, distribution of curvature, bending stiffness, deflection and interface slip can be determined by identified neutral axis position. Secondly, timber-concrete composite beams connected by ductile connectors with different degree of composite action are designed to verify the presented method. Experimental results show that the estimated parameters (neutral axis position, bending stiffness and interface slip) can clearly reflect and quantify the deterioration process of partially composite beams. Meanwhile, both global and local responses can be predicted by long-gauge strain sensors. The predicted responses (deflection at mid-span and strain along the beam height) agree well with the test results when partially composite action is considered, the errors will be unacceptable without considering partially composite action. Hence, the presented method can be utilized for better understanding of mechanical properties of partially composite beams and performance assessment of existing composite structures. [ABSTRACT FROM AUTHOR]

In this paper, based on Von Kármán’s nonlinear theory and the classical lamination theory, a closed form expression is derived for the tangent stiffness matrix of a laminated composite beam element undergoing large deformation and rotation under mechanical and hygrothermal loads. Stretching, bending and torsion have been considered. A co-rotational element reference frame is used as the Updated Lagrangian (UL) formulation. The model has been verified in different problems by comparison with the results of Nastran and ANSYS composite laminate tools, and the difference in the resulting large deformations is less than 5%. The major advantage of the proposed approach is that the composite structure is modeled using 1D beam elements rather than 2D shell or 3D solid elements as in the case of Nastran and ANSYS where laminates are defined over surfaces or 3D solids. The availability of an explicit expression for the tangent stiffness matrix makes the proposed model highly efficient specially when dealing with large composite space frame structures. The saving in computational time could reach 93% compared to regular FE software packages. The developed model is very useful for modeling and designing flexible composites used in new applications such as morphing aerospace structures and flexible robots. [ABSTRACT FROM AUTHOR]

The concept of strengthening reinforced concrete beams using epoxy-bonded steel plates (EBSP) is a well-known solution in structural engineering, however, there is little information about the effect of the width-to-thickness ratio of steel plates on the behaviour of steel–concrete composite beams. This paper presents an experimental study of the flexural behaviour of under-reinforced concrete beams, strengthened in flexure by externally-bonded steel plates (EBSP) of varying width-to-thickness ratios. A total of 23 reinforced concrete beams were tested; 6 beams in Series 1 tests and 17 beams in Series 2 tests. One beam in Series 1 tests and two beams in Series 2 tests were regarded as control specimens, whilst the remaining beams were strengthened with steel plates of different width-to-thickness ratios. In each group, the width of the bonded steel plate varied from 75 mm to 175 mm, in increments of 25 mm. The beams were tested as simply supported, under two-point static loadings until failure. From the experimental results, it was observed that the externally bonded steel plates led to substantial increase in flexural stiffness, which resulted in an increase in the capacity and cracking load of the strengthened beams and a decrease in vertical deflections and crack-widths, compared to the control beams. It was also found that the width-to-thickness ratio of steel plates as low as 12.5 can promote flexural yielding and extensive ductility in strengthened beams. [ABSTRACT FROM AUTHOR]

An attempt has been made here for the isogeometric static analysis of the laminated composite plane beams by using refined zigzag theory. In this study; instead of the standart finite elements, which use polynomial shape functions, an isogeometric refined zigzag finite element (IGRZF) has been developed, that gives the opportunity to get the exact beam geometries directly from a computer aided design (CAD) software, Rhinoceros. To provide less computational effort, the refined zigzag theory has been introduced, that make IGRZF independent from the number of layers considered. The aforementioned finite element has been implemented in an in-house Mathematica code, which can handle both thin and thick beams without the problem of shear locking and does not require shear correction factors. Using this approach, various sandwich beams have been analyzed and the obtained results are compared with other reliable published results for various aspect ratios and support types. [ABSTRACT FROM AUTHOR]

This paper outlines an experiment on a 12 m long composite beam subjected to uniformly distributed loading. Although composite beams are widely used, current Eurocode design guidelines for these types of members can be over-conservative, particularly in relation to the required degree of shear connection. The tested beam comprised a concrete slab supported by profiled metal decking, connected to an asymmetric fabricated steel I-beam using welded shear studs. The specimen was assembled using unpropped construction methods and had a degree of shear connection equal to 33%, significantly lower than the minimum required amount specified in Eurocode 4. A uniformly distributed load was applied to the specimen, which was increased until the failure occurred characterized by yielding of the steel beam. The maximum bending moment of the composite beam obtained from the test was close to the plastic bending resistance according to the Eurocode 4. No concrete crushing or shear stud failure was observed and the end slips exceeded 6 mm, the limit for ductile behaviour in Eurocode 4. The test demonstrated the merits of unpropped construction, which are currently not fully exploited in Eurocode 4. The comparison and analysis suggest that the design limits governing the minimum degree of shear connection might be revised. [ABSTRACT FROM AUTHOR]

This paper presents analytical technique and simplified formulas for the calculations of cracking, yield and ultimate moments of different cases as well as deflections of ECC-concrete composite beams reinforced with steel bars. The technique is based on the simplified constitutive models of materials, strain compatibility, perforce bond of materials and equilibrium of internal forces and moment. Experimental testing of eleven ECC-concrete composite beams reinforced with steel bars is also presented. All beams tested had the same geometrical dimensions but different steel reinforcement strength and ECC thickness. The proposed formulas showed good agreement with the experimental results of various moment values and deflections. A parametric analysis shows that yield and ultimate moments increase with the increase of concrete strength in case of compression failure but, essentially, remain unchanged in case of tensile failure. With increasing the tensile resistance, for example by increasing ECC height replacement ratio, reinforcement ratio, strength of steel reinforcement and ECC, ultimate curvature and energy dissipation increase in case of tensile failure and decrease in case of compressive failure. On the other hand, ductility and energy dissipation ratio decrease with the increase of reinforcement ratio and strength, but, essentially, remain unchanged with increasing the height replacement ratio and strength of ECC. [ABSTRACT FROM AUTHOR]

An exact analytical model based on a higher-order beam theory (HBT) is developed for an accurate prediction of the flexural response of two layered composite beams with partial shear interactions. This is achieved by taking a third order variation of the longitudinal displacement over the beam depth for the two layers separately. The deformable shear connectors joining the two different material layers are modelled as distributed shear springs along the beam length at their interface. The principle of virtual work is used to derive the governing equations which are solved analytically using a Navier type solution technique. To assess the performance of the proposed model, numerical examples of composite beams are solved using the model. The results predicted by the model are compared with published results and the numerical results produced by a one dimensional finite element model based on HBT as well as a detailed two-dimensional finite element modelling of composite beams. [ABSTRACT FROM AUTHOR]

Acoustic Black Hole (ABH) is a wedged taper in thin-walled structures that allows for a smooth and progressive retarding of bending wave speed. However, the application of ABH structures is mainly restricted by its inherent flaw, that is the impaired structural strength by digging holes. To this end, we reinvestigate the ABH concept to propose a compound layout conducive to both wave attenuation and load-bearing capacity. First, the void created by two ABH branches in a periodic double-leaf beam is filled with acoustically soft materials to retain the structural topology continuity. Based on the Rayleigh–Ritz method, a semi-analytical model considering the shear strain of the soft filler is then presented for bandgap computation and validated against finite element simulations. It is shown that the soft filler in the filled-ABH lattice could not only widen bandgaps below the characteristic frequency of ABH, but also preserve the structural bearing ability. Transmission spectra further indicate that reducing the ABH spacing will benefit to the local resonance of composite area, and the shape of ABH profile can be used to improve the broadband attenuation. We expect that this research promotes the engineering application of ABHs in vibration suppression dealing with the sub-wavelength frequencies. • Sub-wavelength bandgaps are opened by the local resonance of the tapered laminates. • A semi-analytical model considering the shear strain in the soft filler is proposed to recover the dynamic response. • The ABH geometry as well as the filling material are used to improve the bandwidths for wave attenuation. • The load-bearing capacity shows greater improvement compared to the increase of the residual displacement caused by the filling material. [ABSTRACT FROM AUTHOR]

A spectral element model is presented for analyzing thermal effect on free vibration and buckling behaviors of generally laminated composite beams subjected to uniform temperature distribution. Coupled differential equations of motion for the generally layered composite beams are derived on the basis of trigonometric shear deformation theory, in which temperature-dependent material properties, temperature change and Poisson effect are incorporated in the mathematical formulation. A spectral element matrix is formulated from the exact analytical solutions of the governing differential equations of the composite beams in free vibration. The spectral element method together with the Wittrick–Williams algorithm is employed to obtain the natural frequencies and buckling temperature change of the generally layered composite beams with various boundary conditions. Comparison of the natural frequencies and/or buckling temperature changes with the ANSYS solutions and/or corresponding results in literature validates the derived spectral element formulation. The effects of temperature change, Poisson effect, boundary condition, material anisotropy and thermal expansion coefficient on the natural frequencies and/or buckling temperature changes of the composite beams are investigated. [ABSTRACT FROM AUTHOR]

This paper presents free vibration of composite beams under axial load using a four-unknown shear and normal deformation theory. The constitutive equation is reduced from the 3D stress-strain relations of orthotropic lamina. The governing differential equations of motion are derived using the Hamilton’s principle. A two-node C 1 beam element is developed by using a mixed interpolation with linear and Hermite-cubic polynomials for unknown variables. Numerical results are computed and compared with those available in the literature and commercial finite element software (ANSYS and ABAQUS). The comparison study illustrates the effects of normal strain, lay-ups and Poisson’s ratio on the natural frequencies and load-frequency curves of composite beams. [ABSTRACT FROM AUTHOR]

The elastic analysis of composite concrete-steel beams and beams retrofitted with FRP laminates is presented in detail. The proposed method and corresponding equations allow the analysis of these beams with generalized end conditions subjected to any transversal loads (concentrated and distributed forces and moments) including the simultaneous effects of shear, bending and axial deformations of each component and connecting material along its span. Three comprehensive examples are presented and the calculated results are compared with those obtained and reported by other researchers showing the efficiency and accuracy of the proposed method and corresponding equations. [ABSTRACT FROM AUTHOR]

This paper presents results of an experimental study on the flexural behaviour of a composite beam, which is reinforced with longitudinal tensile steel bars as well as glass fibre reinforced polymer (GFRP) pultruded I-beam encased in concrete. Five beam specimens, including one traditional reinforced concrete (RC) beam and four composite beams, were cast and tested under four-point bending. The variables involved in the composite beams include the type of longitudinal tensile bars (steel bars and GFRP bars) and the location of the I-beam in the cross-section (middle and a shift of 30 mm towards the tension region). The test results presented in this study show that the proposed composite beams have a very ductile response due to the existence of the tensile steel bars, and the yield point of the composite beam is controlled by the tensile steel bars. The ultimate load of the proposed composite beam in this study is higher than the traditional RC beam in this study, and the ultimate load is governed by the encased I-beam. When GFRP bars were used to replace the tensile steel bars to reinforce the composite beams, the brittle failure of GFRP bars caused lack of ductility of the beam members, and both the stiffness and ultimate load were reduced significantly. Compared with steel bars, the slip between the concrete and the I-beam was also increased when GFRP bars were used. The different location of the I-beam has little effect on the flexural response. [ABSTRACT FROM AUTHOR]

This paper reports testing results of various connections for composite beams made of concrete slab and glue-laminated bamboo (glubam) beam. Six types of composite connectors, commonly used in timber-concrete composite (TCC) beams, were tested under direct shear condition. The shear force-slip relationships were measured and all the relevant mechanical properties such as slip moduli and shear capacities were obtained. Compared with typical TCC beam connections, the Glubam-concrete composite (BCC) systems present several different characteristics. The shear failure along the notch, typical in TCC notched connectors was not observed for BCC system, however, the delamination cracking along the lamination layers occurred in some types of BCC connections. Based on the test results and analysis, six types of connectors can be classified into two categories, one with higher strength and stiffness but low ductility, and the other with lower strength and stiffness but higher ductility. A set of regression equation with a bilinear descent segment is also provided for simulating the shear-slip behaviors of each type connector. It is found that some of the connection systems including the notched connector, steel mesh connector, screw connector and pre-tightening notched connector, are more suitable and recommended for constructing BCC structures. [ABSTRACT FROM AUTHOR]

The Carrera Unified Formulation (CUF) was recently extended to deal with the geometric nonlinear analysis of solid cross-section and thin-walled metallic beams (Pagani and Carrera, 2017). The promising results provided enough confidence for exploring the capabilities of that methodology when dealing with large displacements and post-buckling response of composite laminated beams, which is the subject of the present work. Accordingly, by employing CUF, governing nonlinear equations of low- to higher-order beam theories for laminated beams are expressed in this paper as degenerated cases of the three-dimensional elasticity equilibrium via an appropriate index notation. In detail, although the provided equations are valid for any one-dimensional structural theory in a unified sense, layer-wise kinematics are employed in this paper through the use of Lagrange polynomial expansions of the primary mechanical variables. The principle of virtual work and a finite element approximation are used to formulate the governing equations in a total Lagrangian manner, whereas a Newton–Raphson linearization scheme along with a path-following method based on the arc-length constraint is employed to solve the geometrically nonlinear problem. Several numerical assessments are proposed, including post-buckling of symmetric cross-ply beams and large displacement analysis of asymmetric laminates under flexural and compression loadings. [ABSTRACT FROM AUTHOR]

Blind bolts can be used to connect steel beams to concrete filled steel tubular (CFST) columns, and the obtained composite joints have relatively high initial stiffness, flexural resistance, and ductility at ambient temperature. However, very limited research has been conducted on the fire performance of the blind bolted composite joints. In this paper, eight full-scale blind bolted joints were tested to study their fire performance. The test parameters include: (a) whether fire protection is applied to the steel beam or not; (b) beam load ratio (0.25 and 0.5); (c) type of steel used for the column (stainless or carbon steel); and (d) with or without binding bars in the connection region. The test results indicated that the joint failure was mainly dominated by flexural failure of the steel beam near the panel zone. In general, the blind bolted joints demonstrated very good performance in fire, and no bolt shank fracture or bolt pull-out failure was observed in any joint test. The beam protection or reduction of the beam load significantly increased the fire resistance of the joint, whereas the presence of the binding bars or the type of the steel tube had only moderate influence on the fire resistance. [ABSTRACT FROM AUTHOR]