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To investigate the flexural performance of high-titanium heavy-slag concrete composite beams under loading, this study examined the impact of various factors on deflection development and crack propagation as well as the applicability of empirical formulas for monolithic concrete beams. Seven concrete beams were fabricated with variables such as the reinforcement ratio, prefabrication height, and material composition, and were subjected to two-point concentrated loading. By comparing deflection values and crack widths during loading and analyzing the correlations with empirical formulas from standards, theoretical formulas with significant deviations were modified and compared. The study indicated that the cracking moment and deflection correlated with the reinforcement ratio, material structure combination, and composite height. The empirical formulas for the maximum crack width and deflection of flexural members were applicable to high-titanium heavy-slag concrete composite beams, although some discrepancies existed compared with the experimental values. After modifications, these discrepancies were reduced. This research provides a comprehensive analysis of the deformation characteristics and fracture behavior of high-titanium heavy-slag concrete composite beams. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the bonding strength of aged and other forms of new concrete. Its primary objective is to assess several methodologies for achieving effective bonding behavior. Additionally, the present study examines the impact of varying stiffness and shrinkage rates at the boundary between concrete layers poured at different times. The experiment on bonding strength included examining the effects of several factors, such as surface preparation, bonding agent type, age difference, and the type of concrete used in the new layer. The flexural test results show that the ultimate load decreases by 16.2%, and 13.3% for composite beams with new concrete of Self-Comparing Concrete (SCC), and steel fibers, respectively, compared to the reference beam. However, the ultimate load increases by 6.5% and 9% for composite beams with new concrete of Sika and High-Strength Concrete (HSC), respectively, compared to the reference beam. So, using new concrete with Sika or HSC is the best choice. The composite beam with shear connectors has the highest ultimate load in the test, whereas the beam with SCC as a new layer has the lowest value. [ABSTRACT FROM AUTHOR]

Composite steel‐timber beams – initial ideas for structural design Since the introduction of the Green Deal and the EU Taxonomy Regulation, pressure in construction market has increased to design load‐bearing structures in addition with a view to greater sustainability. Composite beams in steel‐timber construction can contribute to this. However, reliable calculation rules for steel‐timber composite beams do not yet exist. Working Group 6 of TC11 in the European Convention for Constructional Steelwork (ECCS) deals with hybrid steel‐timber structures and this article presents initial ideas for calculation approaches for steel‐timber composite beams. The problems are tackled that, in contrast to concrete, the material timber has a significant tensile strength and the different types of shear connectors between steel and timber can also show a variety of load‐slip curves. Finally, a first comparison between the presented calculation method and a large‐scale test is presented. [ABSTRACT FROM AUTHOR]

This paper investigates the behaviors of different types of prestressed concrete beams utilizing fully encased cold‐ or hot‐formed steel joists. Twelve types divided into two sets of composite beams are assessed. Set 1 is composed of six beams utilizing cold‐formed steel (CFS) joists distinguished by the cross‐sectional steel‐to‐concrete ratios of 1%, 2%, and 3%, and the presence or absence of web openings. Set 2 has the similar composition but utilizes hot‐formed steel joists. Four‐point and three‐point bending tests were conducted at the mid‐span of the composite concrete beams. Key properties, such as strength, stiffness, flexural load capacity, ductility, energy absorption capacity, and failure modes, were used in the analysis. It was found that the specimens with CFS I‐beam joists provided better performance compared to those with hot‐formed steel joists. Also, the existence of web openings in the encased CFS beams enhances the ductility and energy absorption of the composite concrete beams. [ABSTRACT FROM AUTHOR]

This study aims to enhance the ultimate capacity and stiffness of steel–concrete composite beams through external strengthening with prestressed carbon fiber-reinforced polymer (CFRP) plates and post-tensioned CFRP tendons. A 3D finite element model was developed using ANSYS and validated using experiments. The impact of various parameters on the capacity of the beam was investigated, including the level of post-tensioning in the CFRP tendons, tendon profile, degree of shear connection, and beam load level when adding strengthening CFRP tendons. Results indicate that reinforcing composite beams with bonded CFRP plates using post-tensioning tendons with trapezoidal and parabolic profiles can increase maximum load capacity by 37% and 60%, respectively, while maintaining high stiffness. This study also indicates that the optimal strengthening conditions for the composite beam are when the beam is loaded up to 70% of its capacity and has a composite action degree of 100%. [ABSTRACT FROM AUTHOR]

In order to reveal the mechanism of sleeved stud connectors, 15 push-out specimens were designed, and static loading tests were conducted to evaluate the mechanical performance. The shear performance differences between the novel sleeved studs and conventional welded studs were compared. Referring to the experimental results, an Abaqus nonlinear finite element model was established to study the shear mechanism of sleeved stud connectors. Parametric analysis was conducted to investigate the effects of stud height, sleeve filling material, and sleeve diameter on the mechanical performance of the connectors. The experimental and finite element analysis results indicated that the ultimate shear bearing capacity and shear stiffness of the sleeved stud connectors were higher than those of ordinary welded studs, and the maximum slip was relatively small. Compared to conventional welded studs, the ultimate bearing capacity of sleeved studs increased by 4% to 8%, and the shear stiffness increased by 25% to 35%. Since the shear behavior of sleeved studs mainly occurred at the base of the studs, the influence of stud height on shear performance was relatively small. However, sleeve and stud diameter have a great influence on bearing capacity and stiffness. As the Ultra-High Performance Concrete (UHPC) near the base of the stud effectively enhanced the shear carrying capacity of the sleeved stud connectors, the shear carrying capacity and shear stiffness increased with the increase in the sleeve diameter. [ABSTRACT FROM AUTHOR]

In this study, the structural performance of a new type of lightweight composite cold-formed steel and timber (CFST) flooring system has been investigated by conducting four-point bending tests on 13 specimens. A bare cold-formed steel system without timber sheathing was also tested to provide a benchmark response to which the strength and stiffness of the composite system were compared. This paper presents key findings on the flooring system's structural behavior and performance parameters, such as ultimate bending capacity, load-deflection response, load-slip response, and failure modes, by categorizing 13 specimens into four subgroups based on shear connector types and spacings. In the proposed composite CFST flooring system, 45-mm thick structural plywood panels were connected to the 2.4-mm thick cold-formed steel C-section joist using self-drilling screws, coach screws, and nuts and bolts. The performance of different types of shear connectors on the composite action is experimentally investigated and compared with the theoretical plastic section. Furthermore, the load-carrying capacity, effective bending stiffness, and deflection of composite CFST beams were computed theoretically using elastic theory and compared to experimental results, which showed good agreement. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Composite structures inspired by the suture line in the beak of woodpeckers, which is composed of stiff material (mimicking keratin) and compliant material (mimicking collagen), are proposed in this article. The flexural mechanical properties as well as the deformation and failure modes are investigated combining experiments and simulations, which are also compared with conventional laminated structures. First, three-point bending test is performed to characterize mechanical properties such as flexibility, stiffness, strength, and energy dissipation. Experimental results confirm that the suture structure affects the flexural properties significantly. Then, a finite element (FE) model is established to present the strain and stress fields inside the composite beams. The strain distribution demonstrates a shear mechanism in suture structures to dissipate energy, while the stress distribution reveals that the soft layers act as shock absorbers to release stress transmitted through the structure. At last, the failure mode and toughening mechanism of the composite structures is discussed. The mechanism responsible for the mechanical performance of biological structures can be generalized to design architectures with customized mechanical performances. [ABSTRACT FROM AUTHOR]

AbstractIn the present article, geometrically nonlinear analyses of curved laminated composite beams are carried out using Mixed Finite Element Method (MFEM). Timoshenko beam theory is used to consider shear influence which significantly effects the structural behavior of composite layers. Energy-based functional is generally needed to perform geometric nonlinear analyzes of layered composites. However, obtaining energy-based functional in geometric nonlinear theory is quite challenging due to the difficulty of solving mathematically nonlinear differential equations. In this study, this situation is overcome and a functional suitable for performing geometric nonlinear analyzes of layered composite materials is obtained. Incremental formulation procedure is utilized as a solution method for nonlinear finite element analyzes. This is an innovative application of the non-linear mixed finite element method and has the ability to perform geometric nonlinear analysis of curved laminated composite beams with perfect precision. By obtaining the functional in local coordinates, it is possible to solve special problems in various fields such as construction, machinery, aerospace and biomechanics. [ABSTRACT FROM AUTHOR]

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]

Abstract Shear connectors are essential elements in composite structures of steel and concrete as they ensure the interaction between materials and the transfer of forces. In this research, seven models of shear connectors made from bent CA-50 steel bars were tested. The models varied in bar diameter, reinforcement ratio, and inclination relative to the metal profile’s flange. The results showed that the connector with a 12.5 mm diameter (model A1) exhibited the best performance in terms of strength and ductility. Connectors with a 10.0 mm diameter (models B1 and B2) also showed satisfactory results. The inclination of the connectors did not significantly influence the strength of the models. However, a higher tendency for uplift strain was exhibited in the inclined connectors.

Structural engineers, in particular, face the ongoing challenge of ensuring the durability and safety of critical infrastructure components, such as composite beams in bridges and buildings. With aging infrastructure and increasing demands for sustainability and longevity, innovative solutions are essential. The safety and longevity of structures, such as composite beams in buildings and bridges, are paramount concerns. As our infrastructure ages and environmental sustainability becomes increasingly important, innovation in materials and methods is crucial. In this context, we explore a transformative solution the development of advanced crack-filling materials. These materials hold the promise of revolutionizing civil engineering by addressing structural challenges and extending the lifespan of critical infrastructure components. This exploration will delve into the significance of infrastructure, the challenges faced by structural engineers, and the potential impact of advanced crack-filling materials on the field. In this paper we are highlighting the development of a crack filling material for the composite section using Multi Walled Carbon Nanotubes (MWCNTs) and Car-bon fibers (CFs). The use of these two nano materials will subsequently be able to reduce the cracks and heal the composite section wherever necessary. The flexural strength of the beams is significantly increased 15% by the addition of MWCNTs and 67% by the addition of MWCNTs and CFs. The cracked MWCNTs beam coated with MWCNTs, epoxy, CFs gained strength and failed at 1100 N. This is because the coating helped to distribute the load across the crack and prevented the crack from propagating further. The cracked carbon fibers beams coated with MWCNTs, Epoxy and CFs gained strength and failed at 1760 N. This is because the MWCNTs + CFs helped to bridge the crack and transfer the load across the crack. Cement mortar with MWCNTs + CFs after coating increased by 400% This suggests that the coating is effective at restoring the strength of the cracked beams.

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fatigue in steel–concrete composite beams can result from cyclic loading, causing stress fluctuations that may lead to cumulative damage and eventual failure over an extended period. In this paper, the experimental findings from fatigue loading tests on composite beams with various arrangements are presented. Fatigue tests were performed up to 1,000,000 cycles using four-point loading, encompassing various ranges of shear stress at a consistent amplitude. Additionally, the effects of external post-tensioning and the strength of the shear connection were investigated. Static tests were run until failure to assess the enduring strength of the specimens subjected to fatigue. The cyclic mid-span deflections, slippages, and strains were measured during the testing. Based on the experimental findings, it was found that the damage region that the shear studs caused in the concrete slab, which resulted in a reduction in stiffness within the shear connection, grew as the loading cycles increased, leading to an increase in residual deflections and plastic slippages. Controlling the longitudinal fatigue cracks in the concrete slab was largely dependent on the strength of the shear connection between the steel beams and concrete slabs. Moreover, the applied fatigue loading range affected the propagation and distribution of fatigue cracks in the concrete slab. The strains in different parts of the composite specimens were significantly reduced by applying the external post-tensioning. With no signs of distress at the anchors, the tendons displayed excellent fatigue performance. [ABSTRACT FROM AUTHOR]

It is known that steel–concrete composite systems are very efficient. However, such steel–concrete composite systems can be optimised using cold-formed steel elements and innovative shear connections. In other words, by considering demountability and reusability, the negative impact of the built environment on the whole ecosystem can ultimately be reduced. This paper, therefore, presents a numerical study of an innovative solution for a composite floor system consisting of built-up cold-formed sections and concrete slabs. Through parametric numerical analysis, parameters such as the diameter and quality of bolts, the concrete class, the type of concrete slab, and the steel quality of sections and bolts were varied. The numerical analysis results show that the system with a solid concrete slab had a higher shear resistance and ductility than the system with a concrete slab made with profiled sheeting and showed different failure modes. The presented results form the basis for push-out tests for the proposed shear connection types. [ABSTRACT FROM AUTHOR]

In today's construction industry, the use of composite beams is becoming more and more important, particularly for longspan bridges that must withstand repeated loads from moving automobiles. This work investigates the behavior of composite beams through experimentation. Six push-out steel-concrete specimens are made and tested with various levels of static and repetitive loading applied. The specimens are made of rolled steel sections that are joined to concrete decks on both sides by stud shear connectors. Two approaches—one static and the other repeating—applied a push-out load to two sets of samples. One has a stud shear connector measuring 16 mm, and the other measures 25 mm. Three specimens were made for each group. To determine the final load, one specimen from each group underwent a static push-out test in the first stage. In the subsequent phase, repeated loads of 0-80% and 25-80% of the maximum static load were applied to the remaining ones. The analysis process measured the variation in slip between the concrete decks and the steel section over several load cycles. It was found that the recorded slip values at the ultimate load increased about four times just before the failure. The recorded values of the residual slip at the end of each load cycle decreased with the increase in load cycle numbers. Also, it was found that the values of the residual slip depend on the values of the lower and upper limits of the load level. [ABSTRACT FROM AUTHOR]

The utilization and incorporation of glass fiber-reinforced plastics (GFRP) in structural applications and architectural constructions are progressively gaining prominence. Therefore, this paper experimentally and numerically investigates the use of GFRP I-beams in conjunction with concrete slabs to form composite beams. The experimental design incorporated 2600 mm long GFRP I-beams which were connected compositely to concrete slabs with a 500 mm width and 80 mm thickness. The concrete slabs are categorized into two groups: concrete slabs cast using normal-strength concrete (NSC), and concrete slabs prepared using high-strength concrete (HSC). Various parameters like the type of concrete (normal and high-strength concrete), type of stiffeners bonded to the composite section (bolt–epoxy or bolt only), and inclusion of corrugated metal sheets were investigated. To obtain the full shear connection between the GFRP I-sections and concrete slabs, two rows of shear connectors in the form of bolts were utilized. These shear connectors were erected to the top flange of the GFRP I-sections to compositely connect between the GFRP I-beams and the concrete slabs as well as the corrugated metal sheets. The strengthening of the shear webs of GFRP I-beams with GFRP T-section stiffeners resulted in an enhancement in the flexural and shear strength. The failure loads in the case of the bolt–epoxy connection for the stiffeners were 8.2% and 10.0% higher than those in the case of bolt only when the concrete compressive strengths were 20.1 MPa and 52.3 MPa, respectively. Moreover, the effect of the concrete compressive strength was vital where the failure loads increased by 79.9% and 77.1% when HSC was used instead of NSC for the cases of bolt–epoxy and bolt only, respectively. The epoxy adhesive used in conjunction with mechanical connectors, specifically bolts, resulted in sufficient composite action and delayed shear failure within the web of the GFRP beam. For the specimens with bolt–epoxy connection, strain levels in the concrete slabs were consistently higher than in the other specimens with bolts alone at the same loading level. The concrete slabs integrated with HSC registered strain levels that were 20.0% and 21.8% greater for bolt–epoxy and bolt-only connections, respectively, when compared to those using normal-strength concrete (NSC). This discrepancy can likely be credited to the enhanced composite interaction between the concrete slabs and the GFRP I-beams. In addition, ABAQUS software (version 6.2) was used to develop FE models to analyze the tested composite beams and provide a parametric study using the verified models. [ABSTRACT FROM AUTHOR]

Current numerical research was devoted to investigating the effect of castellated steel beams without and with strengthening. The composite concrete asymmetrical double hot rolled steel channels bolted back to back to obtain a built-up I-shape form are used in this study. The top half part of the steel is smaller than the bottom half part, and the two parts were connected by bolting and welding. The ABAQUS/2019 program employed the same length and conditions of loading for four models: The first model is the reference without castellated and strengthening; the second model was castellated without strengthened; the third model was castellated and strengthened with reactive powder concrete encased in the steel web, and the fourth model was castellated and strengthened with reactive powder concrete and lacing steel rebar's welded diagonally on two sides of the steel web. According to the Numerical results, there was an increase in ultimate load capacity compared to the reference model of about 22.74%, 51.65%, and 77.98% in the second, third, and fourth models, respectively; also, there is a reduction in deflection of 55.52%, 58.74, and 60.55% in the second, third, and fourth models, respectively, compared to the level deflection at ultimate load for the reference model, with an increase in stiffness and ductility. In comparison to the I section, the fabrication of a castellated steel beam from the double channel is more cost-effective in terms of cutting steel loss at the ends of the castellated beam, this is due to the feature of rotation and reflection of the steel channel section during cutting and forming to castellated shape.

Fatigue in steel–concrete composite beams can result from cyclic loading, causing stress fluctuations that may lead to cumulative damage and eventual failure over an extended period. In this paper, the experimental findings from fatigue loading tests on composite beams with various arrangements are presented. Fatigue tests were performed up to 1,000,000 cycles using four-point loading, encompassing various ranges of shear stress at a consistent amplitude. Additionally, the effects of external post-tensioning and the strength of the shear connection were investigated. Static tests were run until failure to assess the enduring strength of the specimens subjected to fatigue. The cyclic mid-span deflections, slippages, and strains were measured during the testing. Based on the experimental findings, it was found that the damage region that the shear studs caused in the concrete slab, which resulted in a reduction in stiffness within the shear connection, grew as the loading cycles increased, leading to an increase in residual deflections and plastic slippages. Controlling the longitudinal fatigue cracks in the concrete slab was largely dependent on the strength of the shear connection between the steel beams and concrete slabs. Moreover, the applied fatigue loading range affected the propagation and distribution of fatigue cracks in the concrete slab. The strains in different parts of the composite specimens were significantly reduced by applying the external post-tensioning. With no signs of distress at the anchors, the tendons displayed excellent fatigue performance.

It is known that steel–concrete composite systems are very efficient. However, such steel–concrete composite systems can be optimised using cold-formed steel elements and innovative shear connections. In other words, by considering demountability and reusability, the negative impact of the built environment on the whole ecosystem can ultimately be reduced. This paper, therefore, presents a numerical study of an innovative solution for a composite floor system consisting of built-up cold-formed sections and concrete slabs. Through parametric numerical analysis, parameters such as the diameter and quality of bolts, the concrete class, the type of concrete slab, and the steel quality of sections and bolts were varied. The numerical analysis results show that the system with a solid concrete slab had a higher shear resistance and ductility than the system with a concrete slab made with profiled sheeting and showed different failure modes. The presented results form the basis for push-out tests for the proposed shear connection types.

The utilization and incorporation of glass fiber-reinforced plastics (GFRP) in structural applications and architectural constructions are progressively gaining prominence. Therefore, this paper experimentally and numerically investigates the use of GFRP I-beams in conjunction with concrete slabs to form composite beams. The experimental design incorporated 2600 mm long GFRP I-beams which were connected compositely to concrete slabs with a 500 mm width and 80 mm thickness. The concrete slabs are categorized into two groups: concrete slabs cast using normal-strength concrete (NSC), and concrete slabs prepared using high-strength concrete (HSC). Various parameters like the type of concrete (normal and high-strength concrete), type of stiffeners bonded to the composite section (bolt–epoxy or bolt only), and inclusion of corrugated metal sheets were investigated. To obtain the full shear connection between the GFRP I-sections and concrete slabs, two rows of shear connectors in the form of bolts were utilized. These shear connectors were erected to the top flange of the GFRP I-sections to compositely connect between the GFRP I-beams and the concrete slabs as well as the corrugated metal sheets. The strengthening of the shear webs of GFRP I-beams with GFRP T-section stiffeners resulted in an enhancement in the flexural and shear strength. The failure loads in the case of the bolt–epoxy connection for the stiffeners were 8.2% and 10.0% higher than those in the case of bolt only when the concrete compressive strengths were 20.1 MPa and 52.3 MPa, respectively. Moreover, the effect of the concrete compressive strength was vital where the failure loads increased by 79.9% and 77.1% when HSC was used instead of NSC for the cases of bolt–epoxy and bolt only, respectively. The epoxy adhesive used in conjunction with mechanical connectors, specifically bolts, resulted in sufficient composite action and delayed shear failure within the web of the GFRP beam. For the specimens with bolt–epoxy connection, strain levels in the concrete slabs were consistently higher than in the other specimens with bolts alone at the same loading level. The concrete slabs integrated with HSC registered strain levels that were 20.0% and 21.8% greater for bolt–epoxy and bolt-only connections, respectively, when compared to those using normal-strength concrete (NSC). This discrepancy can likely be credited to the enhanced composite interaction between the concrete slabs and the GFRP I-beams. In addition, ABAQUS software (version 6.2) was used to develop FE models to analyze the tested composite beams and provide a parametric study using the verified models.

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

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

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

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

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

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

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

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

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

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

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

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

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