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The shear performance of fiber-reinforced polymer (FRP)–ultra-high-performance concrete (UHPC) composite beams with FRP shear keys (FSK) was investigated through a four-point loading test and refined finite element (FE) analysis. In total, five test specimens having different concrete strength, concrete slab width and height as well as FSK spacings were experimentally tested. The test specimens were simulated using a refined FE model in ABAQUS. The concrete damaged plasticity model (CDPM) and the Puck failure criterion were adopted to simulate the progressive damage of concrete and FRP profiles, respectively. The mechanical behavior of the interface was captured using a bilinear cohesive zone model (CZM). The comparison between the FE analysis and experimental results demonstrated a good agreement. Based on the validated model, a parametric analysis was conducted on the shear performance of FRP–UHPC composite beams with FSK, focusing on parameters such as concrete slab strength, height and width, FRP web shear strength, shear modulus, height and thickness, and FSK spacing. The results indicate that the maximum local slip beam is less than 4 mm, which verifies that FSK has good interfacial shear resistance. Increasing the strength and section size of the concrete slab can improve the flexural stiffness and the shear capacity of composite beams. The use of UHPC for concrete slabs can also effectively inhibit interface slip. Increasing the shear strength and thickness of FRP web can result in improved load-carrying capacity and reduced deformation of composite beams. This can also lead to a shift in the failure mode from shear failure to bending failure. The reduction of FSK spacing can effectively enhance the shear performance of the interface, thereby improving the composite action and increasing the bearing capacity and deformation resistance of composite beams. [ABSTRACT FROM AUTHOR]

In the present study, the free vibration analysis of piezoelectric composite nanobeams is performed with various boundary conditions. Novel numerical techniques based on quadrature schemes with various test functions are applied with the generalized Caputo kind to solve the boundary value fractional problems. The accuracy and validity of the present analysis are demonstrated by comparing the present results with the previously published ones. Moreover, a parametric analysis is carried out to examine the effect of some material parameters, fractional order derivatives, and geometric dimensions on the vibration attitude of the nanobeam. This parametric study proven the ability of our techniques to provide a solution to most complex fractional differential equations. It is revealed that the fractional differential quadrature methods decrease the time and computational costs. [ABSTRACT FROM AUTHOR]

This manuscript employs a highly efficient artificial intelligence (AI) technique for machine learning (ML) through artificial neural networks (ANNs) and introduces a novel numerical predictive model capable of accurately forecasting the shear capacity of concrete-encased steel (CES) beams. The research begins by conducting shear tests on nine CES beams with high-strength steel, which addresses a significant gap in the shear performance of high-strength steel in CES beams. Subsequently, a comprehensive database of CES beam shear tests is established to train and validate the ANN model. The database consists of 242 sets of test data, compiled from published literature, encompassing a wide range of geometrical and material properties. A sensitivity analysis of the proposed model is then performed using a Pearson chi-square test to determine the relative importance of each input parameter on shear strength. Furthermore, a thorough examination is conducted to assess the impact of each parameter. Finally, the proposed predictive model is compared against current design codes, including ANSI/AISC 360–16 (USA, North America), BS EN 1994-1-1:2004 (Europe), and JGJ 138–2016 (China, Asia). The comparison reveals that ML technology exhibits higher accuracy and robustness in predicting shear bearing capacity. [ABSTRACT FROM AUTHOR]

The aim of crack detection and localization is to minimize sudden failures of rotating machines and static structures while in operation. For this purpose, an impact hammer test is performed in cracked and no crack beams made of steel and composite material to obtain the change in natural frequencies and mode shapes. The impact hammer test is performed with the help of four-channel vibration analyzer, impact hammer and uniaxial accelerometer. A change in natural frequencies is used to detect the crack present in the steel and composite beams. Test data of first three natural frequencies obtained from an impact hammer test on different cracked steel and composite beams are used to train the normalized mode shapes algorithm and plot the mode shapes of first three natural frequencies. The intersection of first three normalized mode shapes is used to estimate the crack location with very high accuracy. From the experimental results, it is confirmed that the change in natural frequencies and intersection of first three normalized mode shapes are used for detection and localization of crack present in the steel and composite beams, respectively. When compared to other methods in the literature for detecting crack location based on mode shape curvature, the methodology used in this paper is more accurate. [ABSTRACT FROM AUTHOR]

A model of thermal stress in double-layer optical dielectric films on circular substrates was established based on the theory of double-layer composite beams. Here, considering the boundary conditions including force balance and bending moment balance, the distribution of stress and strain in the double-layer film-substrate system was analyzed following equivalence manipulation to determine a detailed formula for calculating the thermal stress in the equivalent film and substrate. The derived formula was not only effective in analyzing the stress and strain of the double-layer film-substrate system but was also applicable for predicting the distribution of thermal stress in the periodic elastic multilayer film-substrate system. According to the actual radius of curvature of the substrate measured via a profilometer before and after the deposition of the HfO 2 /SiO 2 double-layer films, the obtained residual stress of the film was − 79.33 MPa, whereas the thermal stress of the film was calculated to be −52.59 MPa using the theoretical formula. The calculations of the theoretical model were similar to the experimental results when the smaller intrinsic stresses were neglected and the double-layer film was only of nanometer thickness, thus verifying the effectiveness of the double-layer film-substrate model. [ABSTRACT FROM AUTHOR]

Thermally-induced vibrations of a one-dimensional, bounded isotropic and composite solid insulated on one side and subjected to various types of heat fluxes on the other side are studied by a series-based theoretical approach in this work. The general temperature equation obtained via conduction heat transfer is used to derive equations for the thermal moment and thermally-induced vibrations, which are generated within the solid as a result. The resulting equations for the thermal moment and thermally-induced vibrations are general and can be applied to different types of heat fluxes. Three types of heat fluxes are used as case studies, namely constant, ramp and sinusoidal types. A thin isotropic and composite beam with various boundary conditions is used to analyze the thermally-induced vibrations resulting from these three types of heat fluxes. Finite element results are also obtained for the thermally-induced vibrations of the isotropic beam in order to compare them with the theoretical ones. [ABSTRACT FROM AUTHOR]

Structural steel and reinforced concrete are the main materials used in civil structures, and each has its own advantages and disadvantages. Nonetheless, when they are combined together to form a composite material, they result in tremendous advancements. There exist different devices to attain the composite action between steel and concrete among which is the shear stud connector that represents one of the most commonly used methods in composite construction, and it is the scope of this study. This monograph examines the degree of shear connection in steel–concrete composite beams depending on the properties of the shear connectors, where mild and rigid shear connectors where studied. It has been concluded via a non-linear numerical analysis backed by experimental testing that the capacity and the deformation of composite beams depend on the configuration and the mechanical properties of the shear connectors. Moreover, a simplified model to predict the degree of shear connection and the capacity of the composite beam was proposed. [ABSTRACT FROM AUTHOR]

Steel–concrete–steel (SCS) structural systems have economic and structural advantages over traditional reinforced concrete; thus, they have been widely used. The performance of concrete made from recycled rubber aggregate from scrap tires has been evaluated since the early 1990s. The use of rubberized concrete in structural construction remains necessary because of its high impact resistance, increases ductility, and produces a lightweight concrete; therefore, it adds such important properties to SCS members. In this research, the use of different concrete core materials in SCS was examined. Twelve SCS specimens were subjected to push-out monotonic loading for inspecting their mechanical performance. One specimen was constructed from conventional normal weight concrete core, while the other specimens were constructed with modified core materials by either partial replacement of the coarse aggregate with crumb rubber (CR), the addition of oil palm fibre (OPF) to the concrete as a volume fraction of concrete, or both in the concrete cores. The investigated push-out specimens have a height of 450 mm and constructed from two hollow steel tubes with a square cross section of 100 mm and 5 mm in thickness which fixed to concrete prism using bolt end shear connectors. The detection of the mode of failure, load–slip as well as ductility behaviour, and the energy absorption capacity was investigated. The results revealed an improvement in the energy absorption (EA) capacity averagely by 55% for the specimen with 15% CR and 1.1% addition of OPF as a volume fraction of concrete in comparison with the reference specimens due to the high shear resistance. [ABSTRACT FROM AUTHOR]

To reduce the self-weight of bamboo-concrete composite (BCC) beams and realize rapid industrial production, innovative assembled bamboo-lightweight concrete composite (ABLCC) beams are presented for use in engineering structures. To verify the structural performance of the ABLCC beams, a series of bending tests were performed on the bamboo beams, the cast-in-place bamboo-lightweight concrete composite (PBLCC) beams and the ABLCC beams. The effects of the thickness of the perforated steel plate, the connector spacing, and the construction technology on the BCC beams were investigated. The test results showed that the failure mode of the ABLCC beams was bamboo fiber cracking at the bottom of the mid-span. Compared with the benchmark bamboo beams, the bending capacity and stiffness of the ABLCC beams increased by 1.43–1.94 times and 2.20–4.16 times, respectively. Compared with the cast-in-place bamboo-lightweight concrete composite (PBLCC) beams, the bending capacity of the ABLCC beam was essentially the same, and the flexural stiffness increased by 1.18 times. The bending capacity, flexural stiffness and combination efficiency of the ABLCC beam increased with decreasing connector spacing. The increase in the thickness of the perforated steel plate did not have a substantial effect on the flexural stiffness of the ABLCC beam. Analytical and numerical methods were validated against the experimental results. [ABSTRACT FROM AUTHOR]

Adhesive bonding has recently emerged as an alternative to shear stud connection in steel–concrete composite flexural members. Research on adhesive-bonded steel–concrete composite flexural members is in a preliminary stage, and the behavior of the bond layer in these structures is not well understood yet. A three-dimensional finite element model is developed and used to conduct the parametric investigations. The developed model is validated with experimental results available in the literature. The behavior of the bond layer is defined in terms of normal stress, normal strain, shear stress, and shear strain. Seven different parameters are studied regarding their effect on the behavior of the bond layer. The parameters include load proportion factor, longitudinal distribution of load, transverse distribution of load, width of concrete slab, depth of the concrete slab, Young's modulus of the adhesive and transverse location of the adhesive fiber. Parametric investigations are carried out to establish the relevance of parameters in terms of their effect on the behavior of the bond layer. The most significant parameters are identified as load proportion factor, longitudinal distribution of load, and Young's modulus of adhesive. [ABSTRACT FROM AUTHOR]

Over the past few years, composite steel–concrete beams saw numerous applications in bridge construction because of their competitive cost in comparison with non-composite steel or reinforced concrete structures. Bridges, in particular and industrial structures in general, are commonly subjected to cyclic loading of vehicles or operating machines. This made it important to study and investigate the behavior of composite structures under fatigue. In this study, the cyclic loading behavior of simply supported composite beams was analyzed numerically using ANSYS finite element software. Following analysis validation using the experimental literature load–deformation results, the numerical models were used in a parametric study to investigate the response under cyclic loading to varying degree of shear connection between the beam's concrete slab and steel section. According to finite element simulation results, there was consistent compatibility in terms of stiffness changes with fatigue life, low deflection values, increased fatigue life and a clear delay in reaching the failure under achieving more than 80% of composite action in order to have the optimum performance under fatigue loading. Shear lag phenomenon—which is a good indication of the continuity in strain between concrete slab and steel beam—was also observed, and it had an influence effect on studying the weld region between shear connectors' body as a target element and top flange of the steel beam in order to achieve the required degree of composite action. [ABSTRACT FROM AUTHOR]

Presented are the results from a finite element model of steel–concrete composite beams with deep decks and a comparison with various analytical/design methods. Using a deck deeper than 80 mm are becoming popular with a desire for longer spanning capability and lower concrete volume. However, there are no design rules in either American or European design codes for using a deck deeper than 80 mm, as both codes limit the deck rib height to 75 and 85 mm, respectively for using the stud's capacity formula. Therefore, research is needed to establish the design stud capacity in beams with decks deeper than 80 mm. After extensive validation, the 3-D FE model is used for a parametric study with tests having decks deeper than 80 mm. The parameters include rib geometries, studs' layout and concrete slab reinforcements. The FE results showed that stud capacity with narrow and deep decks (100–150 mm) is about 70% of the conventional decking (60–80 mm deep). The stud capacities from the numerical results were compared to the predicted strengths from the design/theoretical models. While the equations from the concrete pull-out failure mode by Johnson and Yuan (Proc Inst Civ Eng Struct Build 128(3):252–263, 1998) gave reasonable predictions with a coefficient of variation as 11%, both EC4 and ANSI/AISC rules provided inaccurate and inconsistent predicted strengths. A generalised stud capacity formula should be developed in the design codes for decks deeper than 80 mm. [ABSTRACT FROM AUTHOR]

Experimental and theoretical investigations on the flexural performance of steel reinforced ECC-concrete composite beams subjected to freeze–thaw cycles are presented in this paper. Four groups of reinforced composite beams with different ECC height replacement ratios subject to 0, 50, 100 and 150 cycles of freeze–thaw were physically tested to failure. Experimental results show that the bending capacity decreases with the increase of freeze–thaw cycles regardless of ECC height replacement ratios. However, the ultimate moment, stiffness and durability of ECC specimens and ECC-concrete composite specimens are greater than those of traditional concrete specimens, owing to the excellent tensile performance of ECC materials. With the increase of ECC height, the crack width and average crack spacing gradually decrease. According to materials' constitutive models, compatibility and equilibrium conditions, three failure modes with two boundary failure conditions are proposed. Simplified formulas for the moment capacity are also developed. The results predicted by the simplified formulas show good agreement with the experimental moment capacity and failure modes. A parametric analysis is conducted to study the influence of strength and height of ECC, amount of reinforcement, concrete strength and cycles of freeze–thaw on moment capacity and curvature ductility of ECC-concrete composite beams. [ABSTRACT FROM AUTHOR]

An almost exact solution is derived for the forced vibration of a composite beam with periodically varying non-smooth interface through a moderate weak-form formulation. The material property of a non-uniform beam is characterized by its flexural rigidity function R(x). In the novel method, R(x) is relaxed to be an integrable function rather than a C 2 smooth function in the usual approach. The R(x)-orthogonal bases in the linear span of all boundary functions are derived such that the second-order derivatives of the bases elements are orthogonal with respect to the weight function R(x). When the deflection of the beam is expressed in terms of the bases, the expansion coefficients can be determined exactly in closed form owing to the R(x)-orthogonality of the bases. The solution obtained is almost exact, since its accuracy can be up to the order 10 - 15 . This powerful method is used to analyze the forced vibration behavior of composite beams with three different periodic interfaces. [ABSTRACT FROM AUTHOR]

This paper reports the flexural behaviour of conventional reinforced concrete beams with Slurry Infiltrated Fibrous Concrete (SIFCON) at various locations in the beam. Composite beams are cast with a layer of SIFCON at various locations of the conventional RC beam. Beams made entirely with RC, Fibre Reinforced Concrete (FRC) and SIFCON are also investigated for comparison. A total number of twenty one specimens corresponding to seven test series are cast and tested under two point flexural forward cyclic loading system. The parameters like load carrying capacity, stiffness degradation, ductility and energy absorption capacity are assessed. The concrete mix for RC beams are designed to obtain a concrete grade of M30. For SIFCON, the fibre volume fraction is 9%. The steel fibers used in the study are round crimped fibers having 0.5 mm diameter and aspect ratio of 60. Results indicate that the use of SIFCON in conventional RC beams have enhanced the cracking behavior in terms of considerable increase in the first crack load and in the formation of larger number of finer cracks. The ultimate load carrying capacity, stiffness, ductility and energy absorption capacity are increased to a greater extent for composite beams compared with that of conventional RC beams. [ABSTRACT FROM AUTHOR]

Assessment of embedding ZnO nanorods in a composite beam on the nonlinear response of a beam-mass system is performed. Structural and mechanical characterization of two configured composite beam-mass systems with and without embedded nanorods is conducted. The nanorods were grown on the surface of the carbon fibers by chemical and hydrothermal techniques to form an interface boundary layer between the rods and the fiber/epoxy matrix. Parameters including stiffness, modulus of elasticity, natural frequency, damping coefficient and effective nonlinearities of the two composite beam-mass systems are identified. For the nonlinear parameter identification, the beams were excited parametrically. The results show that embedding ZnO increases the linear damping and modulus of elasticity. The effects of these variations and roles of other identified parameters that impact the parametric response are discussed. [ABSTRACT FROM AUTHOR]

Thermal effects on vibration and buckling behaviors of generally layered composite beams with arbitrary boundary conditions are dealt with in this paper. The composite beam is modeled using third-order shear deformation beam theory in which the Poisson effect is incorporated. A constant temperature change through the beam thickness is assumed. An exact dynamic stiffness matrix is formulated by directly solving the differential equations of motion governing the natural vibration of the composite beams subjected to uniform temperature changes along the beam thickness. Application of the derived dynamic stiffness matrix together with the Wittrick-Williams algorithm to compute the natural frequencies and buckling temperature changes of two particular composite beams is discussed. The correctness and accuracy of the derived dynamic stiffness matrix is evaluated by comparing the present results with the available solutions in literature. The influences of Poisson effect, boundary condition, temperature change, thermal expansion coefficient and material anisotropy on the natural frequencies of the composite beams are studied. [ABSTRACT FROM AUTHOR]

This paper presents the development of an analytical model of steel-concrete partially composite beams subjected to fire. The model includes consideration of temperature dependent material properties, temperature dependent interface slip between concrete and steel, non-uniform temperature distributions throughout the cross-section and the effect of different rates of thermal expansion at the concrete-steel interface. Model predictions showed good agreement with the results of fire tests on two composite beams reported in an earlier companion paper as well as with limited experimental data published in literature. An extensive parametric study was undertaken by using the proposed model. Parameters considered in this study included geometric dimensions of the composite beam, material grades of steel and concrete, shear connection ratio, reinforcing steel ratio in the concrete slab, and load level on the beam. The parametric study clearly shows that shear connection ratio and load level significantly influence the fire performance of partially composite beams. The critical temperatures with shear connection ratio of 50%, 75% and 100% are 645°C, 602°C and 548°C, respectively, under load level of 0.6. The critical temperatures under load ratio of 0.5, 0.6 and 0.7 are 468°C, 553°C and 633°C respectively, with a shear connection ratio of 50%. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and modelling investigation into modular web-flange fibre-reinforced polymer (FRP)-steel composite systems for use in building floor construction. The modular FRP slabs are formed from adhesively bonding pultruded box profiles sandwiched between two flat panels. They are then connected via adhesive or novel bolted connections to steel beams to form a composite system. Two different fibre (pultrusion) configurations are investigated in this paper: flat panel pultrusion with direction either parallel or perpendicular to the box profiles. Composite beams were tested under four-point bending and evaluated for bending stiffness, load-carrying capacity, and the degree of composite action within the FRP web-flange sandwich slab and that provided by the shear connections. All the composite beams showed ductile load-deflection responses, with yielding of the composite beam commencing prior to failure of the FRP slabs. Furthermore, adhesive bonding provided full composite action, but the novel bolted connections with a certain spacing provided either full or partial composite action, dependent on the pultrusion configuration of the FRP slab. Finally, an analytical procedure is presented to evaluate the bending stiffness and load-carrying capacity of the composite beams. Finite element analysis was also employed in this study, showing good comparisons to the experimental results. [ABSTRACT FROM AUTHOR]

To satisfy the interfacial shear force continuity conditions, a new model is proposed for the two-layer composite beam with partial interaction by modifying Reddy's higher order beam theory. The governing differential equations for free vibration and buckling are formulated using the Hamilton's principle, the natural frequencies and axial forces are thus analytically obtained by Laplace transform technique. The analytical results are verified through the comparison with those of several other models common in use; and the presented model is found to be a finer one than the Reddy's. A parametric study is also performed to investigate the effects of geometry and material parameters. [ABSTRACT FROM AUTHOR]

A highly accurate and computationally attractive shear-deformation theory for homogeneous, laminated composite, and sandwich laminates is developed for the linearly elastic analysis of planar beams. The theory is derived using the kinematic assumptions of Refined Zigzag Theory (RZT) and a two-step procedure that implements Reissner's Mixed Variational Theorem (RMVT). The basic expression for the transverse-shear stress that satisfies a priori the equlibrium conditions along the layer interfaces is obtained from Cauchy's equilibrium equations. The resulting transverse-shear stress consists of second-order derivatives of the two rotation variables of the theory, which subsequently are restated as the unknown stress functions. As the first step in fulfilling RMVT, the Lagrange-multiplier functional is minimized with respect to the unknown stress functions, resulting in the stress functions consisting of first-order derivatives of the kinematic variables. Subsequently, the second term of RMVT is minimized, producing four beam equilibrium equations and consistent boundary conditions. For any number of material layers the new theory maintains only four kinematic variables. The theory is labeled RZT, where the superscript (m) stands for mixed formulation. The RZT can accurately model the axial stretch, bending, and transverse-shear deformations, without shear-correction factors. Analytic solutions are derived for simply supported beams subjected to transverse-normal and transverse-shear tractions on the top and bottom surfaces. It is demonstrated that RZT has a wide range of applicability which includes sandwich construction and the laminates with embedded thin compliant layers that can potentially model progression of delaminations. The main advantage of RZT over RZT is in the superior predictions of transverse-shear stresses that are obtained directly from the low-order transverse-shear strain measures of the theory without resorting to a post-processing integration procedure. Importantly, the methodology can be readily extended to plate theory, and it can be applied effectively for developing simple and efficient C-continuous finite elements. [ABSTRACT FROM AUTHOR]

This study was conducted to explore physical and mechanical properties of composite beams constructed from slats of Tali and Hitam bamboo. The beams (6 × 12 × 120 cm) were assembled with PF adhesive to make six types of composite beams as follow : an array of bamboo sheet without woven, a construction of sheets of woven bamboo, and the other four types were made from variation of 2 and 4 cm thick of woven and non-woven of bamboo's sheets. The results showed that average of moisture content, specific gravity, thickness swelling, and internal bonding were 9.01, 0.71, 6.70, and 1.56 %, respectively. The MOE, MOR, and hardness were 7.9 GPa, 41, and 34 MPa, respectively. Those results suggested that these composite beams are suitable for flooring, wall construction, and a substitute for wood beam which applied by light loads. [ABSTRACT FROM AUTHOR]

Post-buckling analysis of composite beams with axially immovable ends is investigated using an Intuitive formulation. Intuitive formulation uses two parameters namely critical buckling load and axial stretching force developed in the post-buckled domain of composite beam. Geometric nonlinearity of von-Karman type is taken into consideration which accounts for membrane stretching action of the beam. Axial stretching force developed in post-buckled domain of composite beam is evaluated by using an axial governing equation and is expressed either in terms of lateral displacement function as an integrated value, or as a function of both axial and lateral displacement functions at any discrete location of the beam. The available expressions of critical buckling load and derived expressions of axial stretching force developed in the beam are used for obtaining an approximate closed-form expressions for the post-buckling loads of various beam boundary conditions. Numerical accuracy of the proposed analytical closed-form expressions obtained from the intuitive formulation are compared to the available finite element solutions for symmetric and asymmetric lay-up schemes of laminated composite beam. Effect of central amplitude ratio and lay-up orientation on post-buckling load variation is briefly discussed for various beam boundary conditions considered in this study. [ABSTRACT FROM AUTHOR]

A finite element model based on sinusoidal shear deformation theory is developed to study vibration and buckling analysis of composite beams with arbitrary lay-ups. This theory satisfies the zero traction boundary conditions on the top and bottom surfaces of beam without using shear correction factors. Besides, it has strong similarity with Euler-Bernoulli beam theory in some aspects such as governing equations, boundary conditions, and stress resultant expressions. By using Hamilton's principle, governing equations of motion are derived. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results for cross-ply and angle-ply composite beams are obtained as special cases and are compared with other solutions available in the literature. A variety of parametric studies are conducted to demonstrate the effect of fiber orientation and modulus ratio on the natural frequencies, critical buckling loads, and load-frequency curves as well as corresponding mode shapes of composite beams. [ABSTRACT FROM AUTHOR]

Ultra high toughness cementitious composites (UHTCC), which has metal-like deformation and crack width restricting ability, is expected to be utilized as retrofit materials. For this application, much attention needs to be paid to the working performance of structure members composed of UHTCC and existing concrete. This paper presents an investigation on the flexural behavior of plain concrete beams strengthened with UHTCC layer in tension face. The effect of UHTCC layer thicknesses on first crack load, ultimate flexural load, crack width, and load-deflection relationship is examined. The experimental results indicate that the use of UHTCC layer significantly increases the first crack load and ultimate flexural load. The first crack load and ultimate flexural load of composites beams increased with the increase of the UHTCC layer thickness. Considerable reduction in crack width was observed for composite specimens, as UHTCC layer restricted the cracks in upper concrete and dispersed them into multiple fine cracks effectively. Moreover, in comparison to plain concrete beam, composite beams could sustain the loading at a larger deflection without failure. Based on the plane section assumption, etc., a calculation method to predict the flexural capacity of composite beam was proposed. Good agreement between predictions and experiments had been obtained. [ABSTRACT FROM AUTHOR]

Composite laminates that consist of two or more layers find widespread applications in a variety of engineering structures. In the computational modelling of composite laminates, the layers can be stacked together and connected conveniently at the nodes by using multiple-point constraints (MPCs). However, this type of modelling leads to weakening of the kinematic constraint conditions imposed by the bond between the juxtaposed layers and as a consequence, MPCs application at the nodes produces behaviour that is softer than the perfectly bonded composite beam behaviour. The work herein shows that when kinematic conditions for composite action are weakly imposed in the variational form, they can be enforced in the point-wise sense by proper selection of the interpolation field or otherwise reinforced by using variational multiscale approach without modifying the kinematic model. The originality of the approach presented herein is in the interpretation of the MPCs application as the solution in a superfluously extended space because of the weakening in the kinematic constraints. It is shown that the perfect bond between the composite beam layers can be recovered by excluding the identified fine-scale effect from the solution of the multiple point constraint application. The convergence characteristic of the finite element formulation is also improved by using the variational multi-scale approach. It is also shown that the fine-scale effects can be represented by using extra fictitious elements and springs, which offers a direct correction technique in modelling of composite beams that is especially useful when access to the numerical procedure is limited. [ABSTRACT FROM AUTHOR]

This article summarizes the results of 13 push-out specimens under the effect of different loading combinations including shear, torsion and negative bending moment. The objective of the project is to record the reductions in the capacity of the stud shear connector and the change in the behaviour of the composite section when torsion is applied. An equation is presented to calculate the produced axial force in the stud shear connector for sections subject to any loading combination. Modifications are performed to the well-known exponential formula representing the load-slip relation of the studs. Finite element application is conducted to simulate the behaviour of the composite section and the stud shear connector as well. The simulation shows a very good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents the accurate prediction of static behavior of composite beams with arbitrary cross-sections. The asymptotic recursive formulation is reviewed first, where the initial three-dimensional problems are split into the macroscopic 1D problems and the microscopic 2D problems. The finite element formulation for the microscopic 2D problems is then presented in order to find the crosssectional warping solutions. The warping solutions obtained contribute the cross-sectional properties to the macroscopic 1D problems. The end effect of the 1D beam problem is also considered via the kinematic correction for a displacement prescribed boundary. The approach presented is applied to the beams with relatively complicated material distributions and cross-sectional geometry. As numerical test-beds, a three-layered sandwich beam and a composite beam with the multi-cell cross-section are taken to analyze the local deformation. A parametric study is also carried out to investigate the significance of shear deformation due to the cross-sectional orthotropic characteristics. The cross-sectional deformation is predicted based on the asymptotic framework. The accuracy of the present approach is assessed by comparing the results obtained with the 3D FEM solutions obtained by ANSYS. [ABSTRACT FROM AUTHOR]

Timber–concrete composite beams and slabs require interlayer connectors, which provide composite action in the cross-section. A range of mechanical connectors is available on the market with an extensive variety of stiffness and strength properties, which are fundamental design parameters for the composite structure. Another crucial parameter is the cost of the connector, including the labour cost, that if too high may prevent the use of the composite system. In order to reduce the construction cost and make timber–concrete structures more widespread on the market, it is believed that a high degree of prefabrication should be achieved. For a simple and cost effective construction process, the use of “dry” connections, which do not require the pouring and curing of concrete on site, may represent a possible solution. This paper reports the outcomes of an experimental programme aimed to investigate a number of different mechanical “dry–dry” connectors previously embedded into a prefabricated concrete slab. Direct shear tests on small blocks made of a glulam segment connected with a prefabricated concrete slab were performed. The shear force-relative slip relationships were measured and all the relevant mechanical properties such as slip moduli and shear strengths were calculated. It was found that some of the new developed connection systems for prefabricated concrete slab can perform as satisfactorily as those for cast-in-situ slabs, with the additional benefit of being relatively inexpensive. [ABSTRACT FROM AUTHOR]

Results of an experimental and theoretical investigation of composite beams as elements of bridge superstructure are presented. Experiments on beams of two types — made of wood and the same beams with a composite sheath — were carried out. The rigidity of the beams of the second type was about twice as high as that of the first ones. The classical bending model of composite beams gave deflections smaller than experimental ones. To reconcile these results, the model is refined by including the effect of shear. The deflections are represented as classical ones multiplied by a shear factor which depends on the bending and shear stiffnesses and the span length of the beams. As a result, a good agreement between calculations and experiments is achieved. [ABSTRACT FROM AUTHOR]

A nonclassical analytical model for the stress-strain state of composite beams with account of shear strains is suggested. It is assumed that the beam is piecewise heterogeneous across its height. Normal and tangential loads operate on its upper and lower surfaces and on interfaces. The model describes the distribution of tangential displacements across the thickness of plies by a third-degree polynomial. The corresponding system of differential equations is obtained by the variational method and contains two equations. The first one is an analog of the equation of classical theory of beams for deflections, and the second one is an analog of the equation of the theory for the bending moment from the generalized load. The solutions to test problems are compared with three-dimensional solutions and with experimental results for simply supported and clamped beams of different composite structure. An applied engineering problem is solved for a multispan statically indeterminate beam. [ABSTRACT FROM AUTHOR]