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In order to promote the application and development of steel–concrete composite beams in bridges, the fatigue performance of corroded studs was investigated. Based on fatigue crack propagation theory and the fatigue failure mechanism of corroded studs, a fatigue life prediction model for corroded studs was proposed. The values of key parameters in the fatigue life prediction model of corroded studs were obtained. Moreover, the fatigue life of corroded studs was analysed. Results show that the error between the calculated value and the test value of the fatigue life of corroded studs is less than 10%, and the fatigue life prediction model for corroded studs is sufficiently accurate. As the corrosion rate of a stud increases, its fatigue life rapidly decreases. When the corrosion rate of the stud increases from 5 to 50%, the fatigue life of the stud decreases from 20 to 90%, respectively; thus corrosion greatly reduces the fatigue life of the stud.

The classical laminate theory is used to create analytic solutions for laminated beams in this study. Several boundary conditions and loads are considered in analytic bending. The boundary conditions taken were hinged-hinged, clamped–clamped and clamped-free and the loading casas taken were center point load and uniformly distributed load. The lamination angles of cross-ply laminated beams were [0 0]s, [90 90]s, [0 9 0]s, and [9 0 0]s. The transverse deflection is maximum for lamination angles [90 90]s, [9 0 0]s, [0 9 0]s, and [0 0]s respectively for both types of loading, center point load and uniform load. The transverse deflection for center point load is higher than that for uniform for all boundary conditions and laminations. The transverse deflection for fixed-free boundary condition is higher than deflection of hinged-hinged, also deflection of hinged-hinged is higher than for clamped–clamped boundary condition. The results obtained were in excellent agreement.

Steel-concrete composite structures are widely adopted in civil engineering attributed to the large span-to-depth ratio, light weight and rapid construction. However, long-term behavior of these structures attacked by environmental agents has not been fully investigated. This study presents an experimental study on monotonic and fatigue behavior of steel-concrete composite beams subjected to corrosion. Ten specimens were prepared using accelerated artificial corrosion and tested under four-point bending with a special focus on the effect of corroded studs. Different failure modes were observed for the specimens tested by static and fatigue loading. Corrosion was demonstrated detrimental effect on both monotonic load-bearing capacity and fatigue life of the specimens. The residual bending stiffness also decreased with corrosion rates.

A computer-aided engineering (CAE) fatigue life prediction technique is developed in this paper to determine the fatigue strength of bolted shear connectors in composite structures. A relatively ne...

In this paper, non-linear finite elements models (FEM) of steel-timber composite (STC) beams have been developed and analyzed using ABAQUS software. In the FEM, the loading conditions of STC beams were simulated, and the nonlinear behaviour of the contact interface between the steel and timber components were incorporated adequately into the FEM. For the yield load, the maximum error between the FE results and the experimental results is 14.85%. The maximum average error of the yield deflection is 12.94%. and of the ultimate load is 16.79%. However, the error of key points was less than 17% (within a reasonable range), which proves that the established finite element model, selected material parameters and contact element model can better simulate the bending performance of STC beams. Finally,a parametric study was carried out by using the verified FEM. It is shown that the FEM developed in this study can replicate adequately the load-deflection response, andthe development of stress and plasticity of the bending experiment.Through the parameter study, it can be seen that thedistribution density and mechanical properties of the connection between the glulam and H-section steel can affect the mechanical behavior of the whole STC beams.

This study investigates the free vibration responses of laminated composite sandwich beam with multi-cores using experimental and numerical methods. The laminated composite face sheets are made by using hand layup method. An experimental modal test has been carried for different configurations of multi-core sandwich beams under different end conditions. The single-core and multi-core sandwich beams has been modeled and the natural frequencies of sandwich beams are determined using ANSYS software. The numerical model is verified by comparing the obtained natural frequencies with experimental results. The numerical and experimental results indicate that the multi-core sandwich beam greatly influences the structural stiffness compared with single-core sandwich beam under different end conditions. Furthermore, the influence of several parameters such as the end conditions, thickness of the core layer, and stacking sequence on the natural frequencies of the various configurations of the multi-core sandwich beams are presented.

In general, a steel beam is assembled with a concrete slab by shear connectors. The connection requires high stiffness and strength to secure the composite effect even in the ultimate state. Facing this need, perfobond shear connectors are attracting a great attention by virtue of its outstanding mechanical performance. However, the connector is subjected to the fully reversed cyclic stress between the compression and tension during an earthquake. Therefore, as presented in the earlier research addressing stud shear connectors, the concrete may originate cracks under the tensile stress; and eventually, the expected composite effect is not possibly performed. To address this concern, this research carried out a total of three fully reversed cyclic loading tests using the component model of perfobond shear connection. The parameters are the presence of reinforcing bars and concrete strength. In conclusion, it was found that perfobond shear connectors exhibit more stable mechanical behavior and capacity than stud shear connectors regardless of stress orientation due to a localized stress transfer mechanism that results in smaller cracks in the slab under a fully reversed cyclic loading.

In this study, numerically and experimentally the dynamic characteristics of graphene-reinforced glass fiber–reinforced polymer hybrid uniform and thickness tapered laminated composite beams were investigated. First, the graphene-epoxy nanocomposite solution without and with 0.25, 0.50, and 0.75 wt.% of graphene reinforcement is prepared by the heat shearing technique and then used for the fabrication of glass fiber–reinforced polymer hybrid uniform and thickness tapered composite beams using the hand lay-up method. The elastic properties of the hybrid beams were evaluated using the impulse excitation of vibration technique (ASTM E1876-15) under elevated temperature. Further, the numerical and experimental modal analysis of the hybrid beams with uniform and tapered configurations were conducted with variation in wt.% of graphene particles under fixed-fixed and fixed–free end supports. The results reveal that the natural frequencies of the glass fiber–reinforced polymer hybrid uniform and tapered configurations with 0.25 wt.% of graphene are greater than those of the glass fiber–reinforced polymer beams without graphene reinforcement and observed lesser for 0.5 and 0.75 wt.% of graphene under fixed-fixed and fixed-free end supports, respectively, due to unavoidable agglomeration effects. Furthermore, the parametric study was performed with the influence of weight fraction of graphene and temperature on the transverse response of the tapered composite beam. Hence, it can be concluded that the use of graphene filler in the glass fiber–reinforced polymer composites in the tapered composite beams improves the bending natural frequencies significantly when the weight fraction of the graphene is used lesser as agglomeration is unavoidable in practical condition. Therefore, the comprehensive numerical and experimental work presented in this study will be useful to the designers while using graphene fillers to improve the bending characteristics of the tapered composite beams.

Nowadays, composite beams have found increasing popularity in the structures due to their proper features. Previous studies did not address the effect of structural damping to analyze the vibrations of composite curved beams. Therefore, in this study, semi-analytical and finite element methods are developed to consider the damping effect in vibration analysis. Furthermore, a framework is presented to study the composite curved beams with variable cross-sections considering the effect of different parameters such as geometric parameters, boundary conditions, and fiber orientation which has been compared with commercial software ANSYS. The results show that the present method can well predict the behavior of the beams.

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.

The paper presents the analytical model of a linear two-layer composite beam with partially debonded interlayer contact. The interlayer contact may be also locally fully debonded. The two-dimensional model is materially and geometrically linear, and the governing equations are based on Reissner beam theory. In the partially debonded interlayer contact, only axial slips are allowed. The finger joints are modelled as linear springs. The analytical solution is presented. The kinematic and equilibrium variables are evaluated along the simply supported beam. A parametric study was carried out to analyse the effect of the strength of finger joints and interlayer contact. In addition, different lengths and positions of the fully debonded area of the interlayer contact were analysed, and their effects on selected kinematic and equilibrium variables were observed and commented on. It was shown that the presence of the fully debonded interlayer contact and finger joints significantly affects the behaviour of the beam as well as the stiffness properties of the interlayer contact and finger joints.

Shear connector (typically shear studs) plays a vital role as a transfer zone between steel and concrete in steel-concrete composite bridge girder. In the previous studies, the connection between steel beam and reinforced concrete slab were considered as continuous joint. However, in practice, this connection is discrete, which allows the slipping and peeling phenomenon between two layers (the influence of peeling is usually very small and could be ignored). To reflect this actual working mechanism, this study proposed a model of shear connection in the form of discrete points at the actual positions of studs for structural analysis. The model was simulated utilizing Timoshenko beam theory considering transverse shear effects. The numerical applications are carried out in order to compare two types of connections. The obtained results indicated that the proposed model properly reflected the actual performance of the structure and in some necessary cases, we should consider discrete connection for more accurate local results.

In this study, a new type of composite beam named flat steel – concrete composite beam is suggested for the rapid development of assembly structures. Experiments were performed on seven flat steel – concrete composite beams and one traditional steel–concrete composite beam to investigate their flexural behaviors. The failure mode of bending-shear fracture for the flat steel – concrete composite beam is found while the traditional steel–concrete composite beam fails by compression-bending fracture. The plane cross-section assumption is applicable to the flat steel – concrete composite beam. Compared with the traditional steel–concrete composite beam, the flat steel – concrete composite beam exhibits higher flexural stiffness, higher moment capacity, and higher ductility capacity. Based on the design theory of the traditional steel–concrete composite beam, simplified models for estimating the flexural stiffness and ultimate moment capacity of the flat steel – concrete composite beam are proposed, and they agree well with the test data.

Post-buckling and dynamic nonlinear stability analyses of a sandwich functionally graded material (FGM) composite beam subject to in-plane compressive static and periodic loading are conducted by implementing a higher-order shear deformation with von Karman kinematics. The dynamic instability region is evaluated using the Mathieu-Hill-type equation in Bolotin’s method. Comparisons of the layered composite beam, FGM sandwich composite beam, shape memory polymer (SMP) composite beam, and SMP-FGM sandwich composite beam with variable in-plane loads $$(N_x^1, N_x^2, N_x^3)$$ are depicted for the first time in the current work. The unstable region of $$N_x^3$$ is lower compared with those of $$N_x^1$$ and $$N_x^2$$ .

In order to provide more accurate suggestions for the restoration of ancient timber buildings, five types of specimens were designed for static loading tests. The tree species used for the specimens was larch. The wooden composite beams were composed of purlins, tie plates, and fangs. The study analyzed the effects of the number and position of dowels on the mechanical behaviors of wooden composite beams in ancient timber buildings. The bending moment, slippage, strain of the wooden composite beams under the deflection of the beam allowed according to code, and the ultimate bearing capacity of the wooden column composite beams under failure conditions were examined. The test results showed that the dowels could improve the bending capacity of the wooden composite beams. The even distribution of the dowels was beneficial in reducing the sliding effect of the wooden composite beams. Under the amount of deflection allowed by the code, the mid-span section strain along the height of the wooden composite beam approximately conformed to the plane section assumption. The wooden composite beam still had bending capacity after each member failed. The results of this study illustrated that dowels improved the overall mechanical properties of the wooden composite beams.

A shear deformable hybrid finite element formulation is developed for the lateral-torsional buckling analysis of fibre-reinforced composite thin-walled members with open cross-section. The method is developed by using the Hellinger–Reissner functional. Comparison to the displacement-based formulations the current hybrid formulation has the advantage of incorporating the shear deformation effects easily by using the strain energy of the shear stress field without modifying the basic kinematic assumptions of the thin-walled beam theory. Numerical results are validated through comparisons with results based on other formulations presented in the literature. Examples illustrate the effects of shear deformations and stacking sequence of the composite layers in predicting bucking loads.

Composite materials are age-old materials used to fulfill different needs in different applications. Polymer matrix composites can be laid layer-wise to fabricate laminated composite beams (LCBs). ...

This article presents continuous interlaminar shear stress analysis of laminated beams with functionally graded single-walled carbon nanotube reinforced composite (FG-CNTRC) layers based on an exte...

Delamination failure commonly appears in composite structures, especially those with curved regions, where a relatively high through-thickness stress is generally created. This study examined the d...

Composite elements are generally used for special types of structures owing to their high efficiency. This research presents an experimental and theoretical investigation on the flexural behavior of low steel reinforcement ratio steel plate-reinforced concrete composite beams. The experimental program consists of 14 reinforced concrete specimens. Meanwhile, the theoretical study involves the verification of the experimental work and a parametric study on the behavior of the steel plate-reinforced concrete composite beams using nonlinear finite element software (ANSYS 18.1). The theoretical and experimental variables include the shape and thickness of the steel plates, the concrete compressive strength, the number of shear connectors, and the use of epoxy resin. The experimental test results revealed that the use of mild steel plates as a replacement for high-tensile steel reinforcements inversely affects the load-bearing capacity of the steel plate-reinforced concrete composite beams. However, when high-tensile steel plates were used as additional reinforcements, the nonlinear finite element analysis predicted up to a 40% increase in the values of the ultimate loads for the composite beams.

This study presents a mixed finite element formulation for the stress analysis of laminated composite beams based on the refined zigzag theory. The Hellinger–Reissner variational principle is employed to obtain the first variation of the functional that is expressed in terms of displacements and stress resultants. Due to C0 continuity requirements of the formulation, linear shape functions are adopted to discretize the straight beam domain with two-noded finite elements. The proposed formulation is shear locking free from nature since it introduces displacement and stress resultant terms as independent field variables. A monolithic solution of the global finite element equations is preferred, hence the stress resultants are directly obtained from the solution of these equations. The in-plane strain measures of the beam are obtained directly at the nodes over the compliance matrix and stress resultants by avoiding error-prone spatial derivatives. Following, transverse shear stresses are calculated from the equilibrium equations at the post-processing level. This simple but effective finite element formulation is first verified and tested for convergence behavior. The robustness of the approach is shown through some examples and its accuracy in predicting the displacement and stress components is revealed.

In this study, a novel method for determining stresses in the torsion problems of laminated composite trimetallic and bimetallic bars was developed and evaluated via experimental and numerical analyses. The objective of this method is to transform a real transversal section of a model for a laminated composite bar into a hypothetical virtual section that is homogenous and isotropic. An analogy with the transformed-section method for solving composite beams under flexion was conducted. The shear stresses (maximum on external surfaces and interfaces) in laminated composite bars were undergoing torsion. Isotropic symmetric and asymmetric laminated composite bars were examined analytically, and the results of their respective experimental and numerical tests were analyzed. The proposed method exhibits differences between 2 % and 12 % compared with the experimental results and between 2 % and 10 % compared with the results obtained using the finite element method.

This paper proposes a steel-wood composite beam with H-shaped steel beam webs glued to the wood. As a new type of composite beam, it combines the advantages of low energy consumption of wood, high permeability, and less pollution and the advantages of light weight and high strength of steel, high degree of assembly, short construction period, and less construction waste generated. Carrying out research is of great significance to improve the mechanical properties of steel-wood composite beams and promote the development of steel-wood composite structures. In this paper, three hot-rolled H-beam-larch composite beams and one pure steel beam were tested for bending capacity. The composite beams are divided into two different combinations of A and B types. The two sides of the web are connected with larch wood by structural glue to form a composite beam. The type B composite beam is a larch wood glued on both sides of the H-shaped steel web and penetrates the bolts at the same time. Through the three-point monotonic static grading loading of the composite beam, the deflection change, failure phenomenon, and form of the specimen during the experiment were observed. Under the circumstances, the ultimate bearing capacity of the test piece was changed to study the combined effect of larch and hot-rolled H-shaped steel. The results show that the overall performance of the H-shaped steel-larch composite beam is good. Bonding wooden boards on both sides of the steel beam web can improve the bearing capacity, and the form of the member is more reasonable and effective; increasing the cross-sectional size of the H-beam in the steel-wood composite beam can further improve the bearing capacity of the composite beam; adding bolt anchorage on the basis of the structural glue used in the composite beam can further improve the bearing capacity of the composite beam. The superposition principle is used to simplify the calculation of the ultimate bearing capacity of H-shaped steel-larch composite beams. Comparing the calculation results with the test results, the data are in good agreement, which can provide a design reference for the practical application of such composite beams.

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

A novel bamboo-concrete composite structure with threaded reinforcement connections is presented. Experimental investigations on the shear behavior of the connectors and the flexural performance of the bamboo-concrete composite beams were carried out. The results indicate that the load-slip behavior of the shear connection with threaded reinforcement exhibits good ductility and that its failure mode is ductile failure. The threaded reinforcement provides an efficient connection before the initial shear failure. The load-displacement curves of the bamboo-concrete composite beams are close to those of the full composite structure, and the midspan displacement is greatly reduced under the same load compared with that of the contrast bamboo beams. The loads PL/250and PL/300, corresponding to the midspan deflections of L/250 and L/300 ( L is the span of the beams) of the composite beams, increase by averages of 3.36 times and 3.71 times, respectively, compared to those of the contrast bamboo beams. The load-bearing performance of the beams in the service state is greatly improved. Based on the equivalent cross-sectional stiffness calculated using the γ-method with a reduction of 0.80, the calculated results of the displacement are in good agreement with the test results.

Shape memory alloys are used in composite structures due to their shape memory effect and phase transformation. The recovery force of the shape memory alloy improves the post-buckling behavior of the structure. In this study, the thermal buckling and post-buckling of Shape Memory Alloy (SMA) hybrid composite laminated beam subjected to uniform temperature distribution is investigated. To this purpose, considering Von-Karman non-linear strain terms for large deformation, the non-linear equations of SMA reinforced beam based on Reddy Bickford theory have been derived. Besides, the recovery stress of the restrained SMA wires during martensitic transformation was calculated based on the one-dimensional constitutive law of the Brinson’s model. A numerical solution using Galerkin’s method has been presented for solving the nonlinear partial differential equations to obtain the critical buckling temperature and transverse deformation of the beam in the post-buckling region in both symmetric and anti-symmetric layups. The effect of SMA volume fraction, pre-strain, the boundary condition of the beam, stacking sequence, and its geometric properties have been studied. The results show that even by adding a small amount of SMA to the composite, the critical buckling temperature increases significantly, and the beam deflection decreases. Besides, using this theory has an evident effect on the anti-symmetric layup, especially for the thick beams.

The present paper investigates the 3 D free vibration behavior of curved metallic and composite beams via a novel beam theory. The refined beam theory is constructed within the framework of the Car...

The forms of U-shaped UHPFRC beams have not been investigated for the highway footbridge. Compared with the traditional section forms, the U-shaped UHPFRC beams can reduce the material consumption under the condition of providing the same bearing capacity. Furthermore, prestressed U-shaped UHPFRC beams are rarely reported in the existing research. This paper explores the flexural behavior of prestressed ultrahigh-performance fiber-reinforced concrete (UHPFRC) beam bridge having unique design and the material properties of prestressed reinforcement combined with UHPFRC. Based on the unique shape of the U beam, the flexural performance test of the full-scale model of the prestressed UHPFRC U beam is conducted. Then, the finite element model considering material nonlinearity and structural ductility is established using Midas FEA software. Finally, the failure mode, failure process, cracking moment, ultimate moment, and strain of the full-scale model are studied. The calculation formulas of the flexural capacity of UHPFRC U beam considering ductile failure are derived. The comparative analysis results show that the prestressed UHPFRC U beam has an excellent flexural performance. The bending failure of a U-shaped beam belongs to the group of ductile failures, which is characterized by the main crack along the central rib and the loading center, which is accompanied by multiple microcracks. The failure process can be divided into four stages: linear deformation, microcracks development, main cracks development, and bearing capacity decline. The incorporation of steel fiber and the interaction between UHPFRC and reinforcement can effectively reduce the development of cracks. The U-beam bending moment is 50–55% of the ultimate bending moment. In the UHPFRC bridge design, the deformation can be used as a control index, and material advantages of the UHPFRC can be used to a certain extent. The strain-hardening characteristics of the UHPFRC are obvious in the loading process. The finite element analysis results show that the maximum strain value appears at the central rib, followed by the transverse strain value of the bottom plate, while the minimum strain is the longitudinal strain value of the bottom plate. The deformation of the rib plate is the largest, and the strain of the other measuring points changes slowly. The farther away from the center the measurement point is, the slower its strain changes. Therefore, the load is mainly caused by the central rib and the loading center plate. With the increase in the deformation, the load on both sides continuously moves to the central rib along the plate surface. This study can provide a useful reference for theoretical analysis and design of prestressed U-UHPFRC bridges.

Fiber-reinforced composites are used in many weight critical applications owing to their high strength-to-weight and stiffness-to-weight ratios. In certain applications, fiber-reinforced composites are subjected to broadband excitation sources that act over a significant portion of the audible frequency range leading to the response of a large number of higher order structural modes. In predicting the response levels of such systems, regardless of whether it is modeled in isolation or using a statistical energy analysis framework, it becomes necessary to quantify the number of resonant modes available to receive and store energy within a frequency band. Conventionally, the mode count and modal density are two parameters used for this purpose. Generally, the analysis of the mode count and modal density of anisotropic fiber-reinforced composite structures have received considerably less attention compared to their isotropic metallic counterparts, and as a result a number of key analytical formulations are yet to be derived and investigated. In this work, the modal distribution and density of nonsymmetric cross-ply laminated composite beams coupled in bending and longitudinal extension are analyzed. A wave approach is used to derive an expression for the mode count of the beam having generalized boundary conditions. Using numerical examples and nonlinear regression analysis, simplified expressions are then obtained for the average mode count function of the beam for different boundary conditions. An analytical expression for the modal density is obtained by taking the differential of the average mode count function with respect to frequency. The wave approach employed in this study is validated based on comparison with results from past literature in addition to finite element simulations. The expression for the modal density is also validated using a finite element model and is shown to be independent of boundary conditions.

Delamination between any two plies is an important damage commonly seen in composite structures. It may initiate and grow in the composite laminates for different loading conditions, and it may finally lead to failure of the component under the cyclic loading. Therefore, fatigue life prediction in these structures is important to avoid the effects of delaminations in economic and safety considerations. The usage of artificial neural network (ANN) in estimating fatigue failure in composites with delaminations would be high. In this work, experimental fatigue data were obtained for glass fiber-reinforced composite beams with and without delaminations. The experimental results were used to train and test the neural network. Finally, ANN was found to be accurate tool for fatigue life estimation for composite materials with delaminations as it produces reasonably good fatigue life prediction for delaminated composites.

The use of composite beams made with traditional concrete and bio-based materials (such as timber and bamboo) is a valuable solution to reduce the environmental impact of the building sector. Timber-Concrete Composite (TCC) beams have been used for decades in structural applications such as new buildings, refurbishment of old timber structures, and bridges. Recently, different researchers suggested composite beams based on engineered bamboo, commonly named Bamboo-Concrete Composite (BCC) beams. This study presents a systematic comparison of structural performances and connection behavior of TCC and BCC beams under short-term static load. TCCs beams are compared to BCC ones using similar shear connectors. The most important aspects of the two composite systems are compared: mechanical behavior of connectors and structural behaviors of full-scale composite beams (e.g., failure modes, connection stiffness, connection shear strength, ultimate load-carrying capacity, maximum deflection and composite efficiency). This comprehensive review indicates that BCC beams have similar or even better structural performances compared with TCC.

Investigation of the behavior of composite beams with different types of shear connectors (spirals and bent bars) extends to include the comparison between the theoretical study and the experimental results of such types of beams. In this paper, a proposed technique for predicting the shear resistance of the spirals as shear connectors in the composite beams is presented. In this- technique, the behavior of the connectors in the elastic and the plastic ranges is analyzed. Hence, a proposed formula to predict the design shear resistance of the spirals is suggested. The comparison between the suggested formula and the experimental results showed a good agreement between them. Moreover, a comparison between the theoretical and the experimental results for the tested composite beams with spirals and bent bars as shear connectors is carried out with respect to ultimate loads. ultimate moment and deflections. The common type of shear connectors as bent bars is compared with spiral connectors as well. A discussion for the given formulae of die beat bar shear resistance in both Egyptian and European (EC4) codes together with the experimental results is conducted which may lead to the modification of the Egyptian formula. The comparison between the present theoretical work and the experimental results has shown good agreement.

Purpose This paper aims to focus on calculating the number of layers of composite laminates required to take the applied load made up of graphite/epoxy (AS4/3501-6) which can be used in many industrial applications. Optimization for minimization of weight by variation in the mechanical properties is possible by using different combinations of fiber angle, number of plies and their stacking sequence. Design/methodology/approach Lots of research studies have been put forth by aerospace industry experts to improve the performance of aircraft wings with weight constraints. The orthotropic nature of the laminated composites and their ability to characterize as per various performance requirements of aerospace industry make them the most suitable material. This leads to necessity of implementing most appropriate optimization technique for selecting appropriate parameter sets and material configurations. Findings In this work, exhaustive enumeration algorithm has been applied for weight minimization of fiber laminated composite beam subjected to two different loading conditions by computing overall possible stacking sequences and material properties using classical laminate theory. This combinatorial type optimization technique enumerates all possible solutions with an assurance of getting global optimum solution. Stacking sequences are filtered through Tsai-Wu failure criteria. Originality/value Finally, through the outcome of this optimization framework, eight different combinations of stacking sequences and 24-ply symmetric layup have been obtained. Furthermore, this 24-ply layup weighing 0.468 kg has been validated using finite element solver for given boundary conditions. Interlaminar stresses at top and bottom of the optimized ply layup were validated with Autodesk’s Helius composites solver.

The bending test is one of the most important tests that demonstrates the advantages of functional gradient (FGM) materials, thanks to the stress gradient across the specimen depth. In this research, the flexural response of functionally graded polymeric composite material (FGM) is investigated both experimentally and numerically. Fabricated by a hand lay-up manufacturing technique, the unidirectional glass fiber reinforced epoxy composite composed of ten layers is used in the present investigation. A 3-D finite element simulation is used to predict the flexural strength based on Hashin’s failure criterion. To produce ten layers of FGM beams with different patterns, the fiber volume fraction ( Vf%) ranges from 10% to 50%. A comparison between FGM beams and conventional composite beams having the same average Vf% is made. The experimental results show that the failure of the FGM beams under three points bending loading (3PB) test is initiated from the tensioned layers, and spread to the upper layer. The spreading is followed by delamination accompanied by shear failures. Finally, the FGM beams fail due to crushing in the compression zone. Furthermore, the delamination failure between the layers has a major effect on the rapidity of the final failure of the FGM beams. The present numerical results show that the gradient pattern of FGM beams is a critical parameter for improving their flexural behavior. Otherwise, Vf% of the outer layers of the FGM beams, i.e. Vf% = 30, 40, or 50%, is responsible for improving their flexural strength.

This paper presents a comparative analysis of shear resistance in the interface between two concrete parts of concrete composite beam. The construction joint was performed as indented one in accordance with Eurocode 2 and fib Model Code 2010. The numerical calculation results were confronted with the actual results of tests of a composite beam subjected to 4-point bending. The displacement values of tested element were obtained using dial sensors and the digital image correlation method (DIC). The analysis shows that the recommendations of Eurocode 2-1-1 and fib Model Code 2010 do not reflect the actual behavior of concrete composite beam with indented surface.