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The current European Standard (EN 1994-1-1: Eurocode 4) put forth a reduction factor for Solid Composite Beam (SCB) with Class 1 and 2 sections for the design moment of resistance for sagging bending. This paper presents the analytical study on the behavior of Cellular Composite Beam (CCB) and proposes the reduction factor for the ultimate moment capacity of CCB sections. A moment-curvature program based on the strain compatibility method has been developed and used to examine the behavior of CCB made of S355, S460, and hybrid strength steel sections with different geometries. The program involves elastoplastic analysis since it is crucial to explore how the cellularity of the composite sections increases their curvature ductility, flexural resistance, and material utilization under high strain. The developed program has been validated against FE results, available test data, and ACB+ software solutions. A parametric study has been carried out to determine the effect of steel grade, concrete grade, effective width and depth of the slab, and varying sizes of a web opening on CCB sections. The Eurocode 4 design guidelines were used to determine the bending resistance of CCB for S355, S460, and hybrid-strength steel sections. The parametric study showed that high-strength concrete with a wider effective slab and enhanced depth sections with the lowest web opening causes CCB sections to have a higher ultimate moment and ultimate curvature. Comparing the hybrid CCB section to the regular and high-strength sections also showcases a significant enhancement in ductility and moment capacity.

This book provides an introduction to the theory and design of composite structures of steel and concrete. Material applicable to both buildings and bridges is included, with more detailed information relating to structures for buildings. Throughout, the design methods are illustrated by calculations in accordance with the Eurocode for composite structures, EN 1994, Part 1-1, 'General rules and rules for buildings' and Part 1-2, 'Structural fire design', and their cross-references to ENs 1990 to 1993. The methods are stated and explained, so that no reference to Eurocodes is needed. The use of Eurocodes has been required in the UK since 2010 for building and bridge structures that are publicly funded. Their first major revision began in 2015, with the new versions due in the early 2020s. Both authors are involved in the work on Eurocode 4.

The dynamic behavior of three-layer composite beams, consisting of concrete slabs and steel beams, is influenced by the structural configuration of each layer as well as the shear connectors. The interlayer shear stiffness in three-layer composite beams governs their global dynamic behavior, while interlayer slippage-induced localized vibration effects represent a key limiting factor in practical applications. Based on the dynamic test results of steel–concrete double-layer composite beams, the feasibility of a finite element solid model for composite beams, which accounts for interlayer shear connectors and beam body characteristics, has been validated. Utilizing identical modeling parameters, an analytical model for the inherent vibration characteristics of three-layer steel–concrete composite beams has been developed. This study encompasses two types of composite beams: concrete–steel–concrete (CSC) and concrete–concrete–steel (CCS). Numerical simulations and theoretical analysis systematically investigated the effects of interface shear connector arrangements and structural geometric parameters on dynamic performance. Research indicates that the natural frequency of steel–concrete three-layer composite beams exhibits a distinct two-stage increasing trend with the enhancement in interlayer shear stiffness. For CSC-type simply supported composite beams, the fundamental vertical vibration frequency increases by 37.82% when achieving full shear connection at both interfaces compared to the unconnected state, while two-equal-span continuous beams show a 38.06% improvement. However, significant differences remain between the fully shear-connected state and theoretical rigid-bonding condition, with frequency discrepancies of 24.69% for simply supported beams and 24.07% for continuous beams. Notably, CCS-type simply supported beams display a 12.07% frequency increase with full concrete-to-concrete connection, exceeding even the theoretical rigid-bonding frequency value. Longitudinal connector arrangement non-uniformity significantly impacts dynamic characteristics, while the transverse arrangement has minimal influence. Among structural parameters, steel flange plate thickness has the most significant effect, followed by concrete slab width and thickness, with steel web thickness having the least impact. Based on the observation that the first-order vertical vibration frequency of three-layer composite beams exhibits a two-stage decreasing trend with an increase in the span-to-depth ratio, it is recommended that the span-to-depth ratio of three-layer steel–concrete composite beams should not be less than 10.

Ultra-high-performance concrete (UHPC), a new cement-based material that offers high mechanical strength and good durability, has been widely applied in construction and rehabilitation projects in recent years. An optimum bending system is achieved by positioning the UHPC layer at the bottom tensile zone of the composite beam and placing the normal-strength concrete (NC) layer at the upper compression zone, which is described as the UHPC-NC composite beam. The fatigue behavior of reinforced UHPC-NC composite beams was described in this study, with an emphasis on the effects of UHPC layer thickness and fatigue load level on the fatigue life of the beam, deformation of the interface between UHPC and NC layers, as well as the bending stiffness of the beam. A total of 9 reinforced UHPC-NC composite beams were tested under cyclic loading. The test variables include UHPC layer thicknesses (zero, 200, and 360 mm), reinforcement ratios (1.184% and 1.786%), and the upper load levels (0.39~0.65). The results showed that good bonding had been achieved without delamination between UHPC and NC layers prior to the final fatigue failure of the beam, and the bending stiffness of the composite beam experienced a three-stage reduction under cyclic loading. Furthermore, an equation was proposed to predict the stiffness reduction coefficient of UHPC-NC composite beams under cyclic loading.

This study develops a finite element solution to analyze the vibration response of multi-layer shape memory alloy (SMA) composite beams. Using Euler–Bernoulli beam motion equations with tension–compression asymmetry, based on Poorasadion’s model, the Newmark method and Newton–Raphson technique are employed. Validating the model against ABAQUS/Standard results for a homogeneous SMA beam shows good agreement. This research explores the dynamic characteristics of bi-layer and tri-layer SMA beams, presenting deflection–time, stress–strain, and velocity–deflection profiles. SMAs’ hysteresis property effectively reduces early-stage vibration amplitudes, and their energy-dissipating feature during phase transformations makes them promising for controlling dynamic performance in engineering applications.

The presence of unavoidable defects in the form of atom vacancies in graphene sheets considerably deteriorates the thermo-elastic properties of graphene-reinforced nanocomposites. Since none of the existing micromechanics models is capable of capturing the effect of vacancy defect, accurate prediction of the mechanical properties of these nanocomposites poses a great challenge. Based on molecular dynamics (MD) databases and genetic programming (GP) algorithm, this paper addresses this key issue by developing a data-driven modeling approach which is then used to modify the existing Halpin–Tsai model and rule of mixtures by taking vacancy defects into account. The data-driven micromechanics models can provide accurate and efficient predictions of thermo-elastic properties of defective graphene-reinforced Cu nanocomposites at various temperatures with high coefficients of determination (R2 > 0.9). Furthermore, these well-trained data-driven micromechanics models are employed in the thermal buckling, elastic buckling, free vibration, and static bending analyses of functionally graded defective graphene reinforced composite beams, followed by a detailed parametric study with a particular focus on the effects of defect percentage, content, and distribution pattern of graphene as well as temperature on the structural behaviors.

This paper reviews the applications and performance advantages of ultra-high-performance concrete (UHPC), engineered cementitious composite (ECC), and recycled aggregate concrete (RAC) in composite flexural members. UHPC is characterized by its ultra-high strength, high toughness, excellent durability, and microcrack self-healing capability, albeit with high costs and complex production processes. ECC demonstrates superior tensile, flexural, and compressive strength and durability, yet it exhibits a lower elastic modulus and greater drying shrinkage strain. RAC, as an eco-friendly concrete, offers cost-effectiveness and environmental benefits, although it poses certain performance challenges. The focus of this review is on how to enhance the load-bearing capacity of composite beams or slabs by modifying the interface roughness, adjusting the thickness of the ECC or UHPC layer, and altering the cross-sectional form. The integration of diverse concrete materials improves the performance of beam and slab elements while managing costs. For instance, increasing the thickness of the UHPC or ECC layer typically enhances the load-bearing capacity of composite beams or plates by approximately 10% to 40%. Increasing the roughness of the interface can significantly improve the interfacial bond strength and further augment the ultimate load-bearing capacity of composite components. Moreover, the optimized design of material mix proportions and cross-sectional shapes can also contribute to enhancing the load-bearing capacity, crack resistance, and ductility of composite components. Nevertheless, challenges persist in engineering applications, such as the scarcity of long-term monitoring data on durability, fatigue performance, and creep effects. Additionally, existing design codes inadequately address the nonlinear behavior of multi-material composite structures, necessitating further refinement of design theories.

This study analysed the strengthening process of a classical steel–concrete composite beam. The beam consisted of a reinforced concrete slab connected by shear studs to an IPE steel profile. The key idea was that the composite beam was strengthened under load. This process simulated an actual reinforced structure that is always subjected to dead loads, with possible service loads. This study assumed that strengthening was implemented to increase the load-carrying capacity and stiffness, not as a way for simulation a repair. The strengthening consisted of expanding the steel part of the beam by welding an additional plate to the bottom flange of the IPE profile. This study included the results of numerical analyses conducted in Abaqus software and lab results. A three-dimensional numerical model was created, taking into account the non-linear behaviour of concrete and steel, the susceptibility of the composite at the joint plane, and the residual stresses created during welding. A full-scale strengthening of the composite beams under load was carried out. Comparison of the results obtained in the experimental tests and numerical analyses showed a very high convergence of the results, as well as in terms of the non-linear operation of steel and concrete. This confirmed the validity of the created numerical model, which can be the basis for further research into the process of optimal strengthening of composite elements.

Steel fiber-reinforced concrete (SFRC) exhibits superior tensile and flexural strengths, crack resistance, compressive toughness, and ductility. These characteristics make SFRC attractive for precast beam joints, shear-critical regions without stirrups, and retrofitted overlays, thereby enabling composite members. However, the shear and flexural responses of such members often differ from monolithically cast elements. To clarify these effects, nine composite specimens and one cast-in-place control were tested under four-point bending. Key parameters, including load-bearing capacity, failure evolution, and failure modes, were documented, together with load–deformation behavior, reinforcement strains, and concrete deformations. Results showed that horizontal joints reduced shear resistance and altered crack propagation compared to monolithic beams. Incorporating 1.0% hooked-end steel fibers improved both shear and flexural performance. SFRC above the joint was more effective for shear, while SFRC in both zones improved flexure. The fully SFRC specimen without stirrups achieved 63% higher shear capacity than its NC counterpart, with ductility rising from 2.2 to 3.1. A 1.0% fiber dosage provided shear resistance equivalent to D8@200 stirrups, confirming the potential of SFRC to reduce transverse reinforcement. Analytical models, including a fiber beam–column element and strut-and-tie approach, showed reasonable agreement with experiments.

A cold-formed, thin-walled steel/fast-growing timber composite system has recently been presented for low-rise buildings. It aims to increase the use of fast-growing wood as a green building material in structures, thus contributing to the transformation of traditional buildings. This study proposed a composite I-beam combined with fast-growing radiata pine and cold-formed thin-walled U-shaped steel. A four-point bending test was used to measure the bending properties of steel–timber composite I-beams under various connection methods. Based on experimental results, this study examined the specimen’s failure mechanism, mechanical properties, and strain development. In addition, a method for calculating flexural bearing capacity based on the superposition principle and transformed section method was suggested. It is evident from the results that fast-growing timber and cold-formed thin-walled steel can have significant composite effects. Different connecting methods significantly impact beams’ failure mode, stiffness, and bearing capacity. Furthermore, the theoretical method for calculating the flexural bearing capacity of composite beams differs from the test value by less than 10%. This paper’s research encourages the applications of fast-growing wood as light residential components, and it serves as a reference for the development, production, and engineering of steel–timber composite structural systems.