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This study aims to investigate the effect of the ring plate on the mechanical performance of X-type tube-gusset joints. The failure modes, ultimate strengths, and failure mechanisms of X-joints with ring plates were investigated through experiments and finite element analyses. The results indicated that the ring plate and the chord within the effective range of the ring plate constituted the primary bearing structure of the X-joint. Increases in the ring plate thickness and width increased the ultimate strength of the X-joint. By considering the forces of the braces as a superposition of the bending moment and the force acting on the gusset of the X-joint, a simplified calculation method for the ultimate strength of X-joints was established. The derivation process was validated and refined through experiments and finite element analyses. Finally, a safe and reliable formula was derived for evaluating the ultimate strength of X-joints. [ABSTRACT FROM AUTHOR]

In this paper, we present an investigation of the performance of reinforced concrete (RC) columns under combined bending loads and various axial forces using a finite element method (FEM) model developed with the ABAQUS finite element program, verified with actual experimental values. In the experimental study, we applied combined bending loads and various axial forces to four RC members. Two RC members were subjected to vertical cyclic loads using displacement control with 0% axial force, while the other two were tested with vertical cyclic loads, one with 10% axial force, and the other with 20% axial force. The axial force load was applied using a specially designed setup. The experimental results of the RC members include observations of final failure mode, ductility, and axial load–bending moment interaction curves (P–M correlation curves). The experimental study confirmed that as the axial force increased, cracks in the RC columns concentrated at the center of the column. The yield strength increased by 55% when the axial force ratio was 10%, and 106% when the axial force ratio was 20%. The maximum strength increased by 28% with a 10% axial force ratio, and 50% with a 20% axial force ratio. However, ductility tended to decrease as the axial force increased, reducing by 26% with a 10% axial force ratio and 60% with a 20% axial force ratio. The analytical study produced results consistent with the experimental research, showing similar numerical trends. Finally, when comparing theoretical values, experimental results, and analytical results using P–M correlation curves, we found that the experimental value has a safety rate of 18% compared to the theoretical value. The experimental and theoretical result values were similar. Therefore, it has been demonstrated experimentally and analytically that the current design has a safety value of about 18% for the performance of the actual structure. [ABSTRACT FROM AUTHOR]

The complex distribution of synchronous grouting pressure results in excessive tunnel deformation and various structural diseases, especially for ultra-large-diameter shield tunnels. In this study, to reduce the risk of tunnel failure, a three-dimensional refined finite element model was established for the Wuhan Lianghu highway tunnel project, taking into account the non-uniform distribution of synchronous grouting pressure. This study focuses on investigating the development patterns of internal forces, deformations, and damages in segment structures under varying grouting pressure ratios. The results indicate that the primary failure mode of a segment is tensile failure occurring at the outer edge of the arch. Moreover, an increased ratio of grouting pressure between the arch bottom and top leads to a higher positive bending moment value and greater tensile damage at the arch waist. The tunnel ring gradually exhibits distinct "horizontal duck egg" shape deformation. When the grouting pressure ratio is 2.8, there is a risk of tensile cracking at the outer edge of the arch waist. At this time, the segment convergence deformation is 39.71 mm, and the overall floating amount reaches 43.12 mm. This research offers engineering reference for the prediction of internal forces and deformations in ultra-large-diameter shield tunnels during grouting construction, thereby facilitating their application in the development of resilient cities. [ABSTRACT FROM AUTHOR]

This paper focuses on investigating the structural behavior of members and connections that are part of moment frames under the combined effect of bending moment and thermally induced axial force during a compartment-fire event. The finite-element analysis method was employed to conduct this study using models benchmarked against experimental data from several past studies while utilizing temperature-dependent material models. A numerical parametric study on typical floor beams with slender elements for compression were conducted under combined bending and axial loading to develop interaction-capacity curves at temperatures representing fire events. The results were compared against the member-strength equations provided in the AISC Specification. The analysis results demonstrated that the AISC beam-column strength equations including the combined effects of axial-load and bending moment provided reasonable estimates for member-slenderness ratios greater than 60, but overestimated the strength of beams with slender elements for low member-slenderness ratios. Combined-load-strength studies were also conducted on a typical connection used in moment frames. The moment-connection behavior was governed by failure modes exhibited at the ends of floor beams. Therefore, the interaction equations available for beam columns resulted in conservative estimates and are recommended for calculating moment-connection capacity during compartment-fire scenarios. [ABSTRACT FROM AUTHOR]

A new type of precast pile, namely steel strand square piles with reinforcement (PRS), is proposed in present study, which uses steel strand as a prestressed reinforcement and is equipped with hot-rolled reinforcement. Two kinds of full-scale pile specimens with different reinforcement were constructed to study the bending performance by the full-scale tests. The finite element model was also performed to study the differences in bending resistance, deformation capacity, crack resistance, and failure mode because of the reinforcement ratio. The results show that the steel strand in the pile was not pulled off, and the concrete in the compression zone was crushed. The finite element analysis results are close to the results of the full-scale test of the piles, which can simulate the flexural performance of the pile well. The experimental results were closer to the theoretical calculation of the cracking moment. The ultimate bending moment value is about 25% more than the theoretical value. The parametric analysis shows that for the PRS with 0.27% prestressed reinforcement, the best bending performance is achieved with 0.64% non-prestressed reinforcement. For the PRS with 0.64% of non-prestressed reinforcement, the best bending performance is achieved with 0.37% of prestressed reinforcement. [ABSTRACT FROM AUTHOR]

The cantilevered leg joint commonly used in modern wood furniture was studied by numerical and experimental methods. A novel joint was proposed and compared with the typical joint commonly used in the cantilevered leg. Both of them were made of beech wood (Fagus orientalis. Lipsky). The experimental results showed that the bending moment capacity of the novel joint was remarkably higher than the typical joints, which confirmed that the novel structure had a better mechanical performance. The numerical analysis was conducted according to GB/T 10357.3 standard, the results showed that the stresses of the typical joint were mainly concentrated on the wooden components, while the stresses of the novel joint were concentrated on the metal connectors. The stress concentration obtained by the finite element method (FEM) was consistent with the failure modes of the experimental tests, which provides a reliable method for evaluating and optimizing the novel furniture structure. [ABSTRACT FROM AUTHOR]

The bending mechanical properties of FRP-confined square concrete-filled steel tubes (CFST) reinforced with internal latticed steel angles, including the failure modes, characteristic curves and characteristic mechanical parameters of tested specimens, were investigated through experiments in this paper. The bending mechanisms were also analyzed using an established finite element model, including the analysis of the bending moment borne by each component, the distributions of contact pressure between different components at the mid-span section, and the distributions of the neutral axis under the bending capacity. The key influential parameters, including the tensile strength and thickness of the FRP, were also examined. The results indicate that the FRP has almost no influence on bending stiffness, however, it enhances the yield bending moment and bending capacity to a certain extent. It was also found that the enhancement decreases as the width of steel tube increases, and the influence of FRP is more profound before reaching the peak load. The calculation formulas for the bending capacity were developed using the superposition method and numerical fitting method. Analysis of their accuracy shows that the formulation using the superposition method yields relatively accurate and safe prediction results, with the prediction errors of less than 20 %. • The bending behavior of FRP-confined square CFST reinforced with internal latticed steel angles is investigated through experiment; • A method for characterizing the yield bending moment and bending capacity of the tested specimens is proposed; • The bending mechanisms are analyzed using an established finite element model; • The calculation formulas for the bending capacity are proposed based on the superposition method and numerical fitting method. [ABSTRACT FROM AUTHOR]

• Peeling forces in friction stir composite joints are not enough to overcome the binding forces. • Higher stiffness of composite joints resulted in a rigid body rotation due to secondary bending. • The failure mechanism exhibited a brittle behaviour with crack nucleation at the highly strained region. • A relationship between tension, bending and mechanical performance of the joint was obtained. • The development of secondary bending moment acts as main catalyst of the failure mechanism. Friction stir composite joints between an aluminum alloy (AA6082-T6) and reinforced polymer (NorylTM GFN2) were studied regarding their failure characteristics. A comprehensive analysis on the mechanical behaviour of the joints was carried out, assessing the resulting deformed shape, the associated strain field and the observed failure modes using a digital image correlation (DIC) system and comparing with a finite elements method (FEM) model. The numerical model evidenced a good fitness to the experimental results since both the displacements and strain fields were found to be very similar. Both numerical and experimental strain fields in the longitudinal direction exhibited a localized spot of highly strained material, clearly indicating the nucleation site. Since secondary bending occurs in structural elements under tension due to geometrical and stiffness asymmetries, as is the case of overlap composite joints, a bending stress is induced, increasing the local stress compared to the nominal tension stress values. The ultimate tensile stress of the joints was found to range between 60.2 and 70.4 MPa, leading to an average joint efficiency of 82.6 %. The bending factor (k b) at the failure region was found to be 2.0, which means that the bending stress accounts for 2/3 of the total stress, acting as main failure catalyst. [ABSTRACT FROM AUTHOR]

• The impact test results of the scaled model corresponding to the finite element model were used to verify the accuracy of the adopted material models and contact relationships. • Based on the spatial complexity of urban overpasses, the dynamic responses and failure mode of the full-bridge model under non-bottom impact were numerically simulated. • Four comparative models were established to study the effect of the bridge model parameters on impact responses. Urban viaducts are likely to be subjected to non-ground-level vehicle collisions during their service life period. However, current research primarily focus on vehicle impacts on the bottom of bridge piers. In this research, a full-bridge scale model impact test was conducted to validate the accuracy of the finite element (FE) model. Then, LS-DYNA is used to establish refined vehicle-bridge collision FE models. The dynamic responses and failure mode of the pier impacted by the non-bottom vehicle are investigated. Besides, the effects of bridge structure spatial stiffness, superstructure mass, and double-column structure on the impact responses of bridges are analyzed. The results show that vehicle collisions are characterized by a continuous impact action involving multiple components. The damage to the full bridge model is concentrated in the directly impacted double-column pier, where the head-on column sustains three-point bending damage, the indirectly impacted column sustains bending damage at the top and bottom, and the cover beam sustains tensile shear damage. The non-bottom impact significantly increases displacements and bending moments of the pier while causing a substantial decrease in bottom shear. The impact responses of the pier are greatly influenced by the superstructure mass and double-column structure, while the spatial stiffness of the bridge has minimal affection. [ABSTRACT FROM AUTHOR]

Reported studies on T-head Square-neck One-side Bolts (TSOBs) bolted I-beam to Hollow Section Square Column (HSSC) connections demonstrated the potential of TSOB applications in terms of mechanical properties, installation construction, and cost savings [11–14]. However, existing research was limited to the connection tests and lack a systematic and complete design approach. In this paper, the method for predicting the bending moment capacities and failure modes of the connections was proposed based on the existing test researches. Besides, the Finite Element Model (FEM) of the connections was established and validated by the reported test results. A sensitive analysis on the geometric parameters of the plastic hinge line pattern for calculating the bending moment capacity of the HSSC connecting face was carried out by the validated FEM. The proposed method was compared with the numerical simulation method in terms of the predicted results of the connection structural behavior. The results show that the prediction method proposed in this paper for the connection bending moment capacities and failure modes is accurate and reliable. Moreover, the mixed patterns of Type-H bolt holes and Type-V bolt holes are recommended for the TSOBC design because of the higher bending moment capacity than the unitary bolt hole patterns. • Method for predicting the bending moment capacity of TSOBC was proposed. • Failure mode of TSOBC was predicted based on design information. • Mixed patterns of Type-H and Type-V bolt holes are recommended for TSOBC. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and numerically the behaviour of a balcony-to-slab connection made by an H-profile embedded in the concrete slab. A large-scale test was performed on a specimen of the connection system in order to determine the moment-bearing capacity, the deformation behaviour, the cracking patterns, the distribution of the bending moment along the axis of the embedded steel H-profile as well as the failure mode of the connection system. The test results showed that the failure mode was governed by the concrete shear of the slab. In addition, a 3D finite element model of the experimental test was also carried out and successfully validated against the experimental results. For a practical design of the connection system, a model based on Timoshenko beam on elastic foundation (BEF) was investigated and verified against the results obtained from the validated FE model. The Winkler modulus of the BEF model was determined by considering the local deformation of the concrete based on a strut-and-tie model. The results demonstrate that the BEF model with this value of the Winkler modulus provides a conservative estimation of the shear and bending forces applied to both the embedded H-profile and the concrete cross-sections. This method is a first tentative design basis using linear elastic theory for such a system. • Experimental and numerical investigation on the behaviour of embedded H-profile balcony-to-slab connection • A BEF model is proposed to determine the distribution of shear and bending forces on embedded steel profile and concrete. • Winkler modulus is determined by considering the local deformation of the concrete based on a strut-and-tie model. [ABSTRACT FROM AUTHOR]

To study the mechanical properties of stainless-steel-reinforced concrete (SSRC) columns under eccentric compression, one ordinary reinforced concrete column and eight SSRC columns were designed for eccentric compression load tests. The eccentricity and reinforcement ratio were considered as the variation parameters. The cracking and failure modes of the SSRC columns were studied. The effects of the variation parameters on the longitudinal strain, concrete strain, lateral displacement, and ultimate load were analyzed. The test results demonstrated that the failure modes of SSRC columns under eccentric compression are similar to those of ordinary reinforced columns. Eccentricity significantly affected the failure modes of the SSRC columns. Under the same eccentricity, the reinforcement ratio had negligible effect on the lateral displacement corresponding to the ultimate load. The mechanical properties of SSRC columns under small eccentric compression were better than expected; however, the ultimate loads under large eccentric compression were proposed. The ultimate load–bending moment curves obtained were consistent with the results of the test and finite element analysis. Based on the experimental results, the force characteristic coefficient was set as 2.7 for calculating the long-term crack width. [ABSTRACT FROM AUTHOR]

The assembling rivet-fastened rectangular hollow flange beam (ARHFB) is a new type of cold-formed steel beam. The ARHFB section has two rectangular hollow flanges formed by U-shaped and C-shaped components that connected by self-locking rivets. A finite element model is developed to simulate 16 four-point bending experiments. Details of the modeling including finite element meshing, loading and boundary conditions, contact and analysis methods are presented. The accuracy of the developed finite element model is verified by comparing the ultimate moment capacity, applied load versus deflection curves, bending moment versus deflection curves, strain versus deflection curves and failure modes obtained from the tests and the finite element analysis. Based on the validated finite element model, a parametric analysis is carried out to discuss the effects of rivet spacing, section depth, flange thickness, and web thickness on the bending performance of ARHFB. The moment capacities of these sections obtained from the parametric study are compared with predictions from Australia and New Zealand, Chinese design standards for cold-rolled sections and the DSM (Direct Strength Method). It is found that GB50018 can conservatively predict the bearing capacity of ARHFB with a large error, while AS / NZS 4600 and DSM (Direct Strength Method) cannot provide reliable prediction results. • A novel assembling rivet-fastened rectangular hollow flange beam (ARHFB) is analyzed in finite element model. • An extensive parametric investigation using a verified finite element model is conducted. • The feasibility of current design codes for ARHFBs is evaluated and judged. [ABSTRACT FROM AUTHOR]

• Impact resistance of RC beam with and without UHPC strengthening was studied. • More ductile failure mode was obtained with UHPC jacketing. • Impact location affects the strengthening effects of UHPC jacket. • Refined FE modelling supplements the data collected from high-speed camera. To enhance the impact resistance of built reinforced concrete (RC) members, the effectiveness of using ultra-high performance concrete (UHPC) for strengthening RC structures was investigated in this study. The mechanical properties of UHPC were evaluated by the uniaxial compression, tension and flexural bending tests. Drop weights with hemispherical and wedge-shaped indenter were adopted to impact the beam specimens with and without UHPC strengthening. A total of six beams, including three control RC beams and three UHPC jacketed RC (RC-UHPC) beams, were tested. The beams were prestressed in the axial direction with a 200 kN force. The test results revealed that the UHPC jackets improved the structural impact resistance. With an impact mass of 411 kg and an impact velocity of 4.95 m/s, the maximum and residual deflection of the RC-UHPC specimen decreased by 15.3 % and 21.1 % as compared to the RC control specimen, and the failure mode shifted from diagonal shear failure to flexural failure. To further investigate the dynamic responses of the beams, a detailed finite element model was established and validated with the test results in terms of the impact force, structural deflection and damage profile. The dynamic shear force and bending moment distribution diagrams were numerically derived to examine the failure mechanism of the test specimens. Finally, a parametric study was conducted to evaluate the effect of different impact locations and UHPC jacket length on the impact resistance of strengthened RC beams. [ABSTRACT FROM AUTHOR]

A new type of inner and outer double-ringed (IODR) flange was introduced in this paper, which can make full use of the inside and outside space of circular tube and reduce the dimensions of connecting bolt and flange plate. Five groups of down-scaled IODR flanges with different flange plate dimensions were designed and tested under bending moment to study the failure mode and force-transferring mechanism. The finite element model was built to further investigate the influence of connection dimensions on the bending performance from different aspects, such as bearing capacity, location of rotation axis and bolt tension ratio. It reveals that the failure of IODR flanges occurred due to the necking of bolt. The bolt tension ratio has an insignificant change when the applied load is smaller than about 80% of bending capacity, then it tends to increase until approaching 1.0. A theoretical method for rotation axis position and bolt force was proposed considering flange geometry parameters and bolt arrangement. It was found that the obtained rotation axis positions are about 0.7 r , which is smaller than 0.8 r recommended in DL/T 5629–2021, meaning that the existing design method is unsafe. Based on the theoretical analyses, the design methods of flange plate, stiffener and bolt were proposed and a corresponding design process was also established. • A new kind of inner and outer double-ringed (IODR) flange was introduced. • Bending experiments of IODR flange were performed. • The FE model was built to investigate the bending performance of IODR flange. • A theoretical method for rotation axis position and bolt force was proposed. [ABSTRACT FROM AUTHOR]

A submerged floating tunnel (SFT) is a structure that has been proposed as an innovative solution for waterway crossings around the world. However, to this day, no SFT has been constructed yet. One of the main reasons is that there is an insufficient insight into the structural reliability of the SFT. Here, a method to assess the expected structural response of an SFT under traffic loads and a reliability assessment of the results is presented. To do this, traffic models and structural response and reliability are coupled. The methodology presented herein proposes an innovative way to combine copula-based models and structural models to obtain more a more realistic structural response of the SFT. The focus will be on one failure mechanism, leakage caused by bending failure of the SFT in the longitudinal direction. The method utilizes a copula-based model to characterize the traffic loads and simulate traffic loads on the SFT (axle weight, inter-axle distance, and inter-vehicle distance). Next, a structural model is used to assess the structural response and derive stresses. Using a probabilistic analysis, the design of the cross-section can be adapted so that it meets the requirements for leakage caused by bending moments. For the case study is demonstrated that for a buoyancy weight ratio (BWR) of 1.1 an optimal design can be achieved based on a probabilistic method. This methodology could be extended to other failure modes of an SFT or to other structures. • The structural response of Submerged Floating Tunnels due to traffic loads. • Application of copulas to define a representative load sequence. • Application of low level Finite Elements Method to calculate the structural response. • Design optimization by use of probabilistic tools. [ABSTRACT FROM AUTHOR]

• 1/5 scaled RC double-column RC bridge pier (DCBP) specimens are prepared. • Lateral consecutive impact test on bare and CFRP strengthened DCBPs is carried out. • Dynamic responses and damage evolution of bare and CFRP strengthened piers are analyzed. • CFRP strengthening effect on vehicular impact resistance of prototype bridge is evaluated. As-built reinforced concrete (RC) piers could be subjected to vehicular collisions in their whole service life, resulting in severe shear failure of piers and even catastrophic damage to entire bridges. Considering that the vehicular collision is the lateral consecutive impact process including bumper, engine and cargo impacts, the effectiveness of CFRP shear-strengthening of double-column RC bridge piers (DCBPs) to resist the lateral consecutive impact needs to deeply studied. Firstly, the reduce-scaled vehicle model lateral consecutive impact test is performed on a bare pier, a CFRP shear-strengthened slight-damaged pier and a CFRP shear-strengthened intact pier in DCBP specimens. The influence of CFRP strengthening on the damage evolution, failure mode and transient dynamic responses and energy dissipation are examined. Then, numerical simulations of the present impact tests are conducted to validate the adopted finite element analyses (FEA) approach. Furthermore, based on the validated FEA approach, a local refined finite element (FE) model of a prototype simply-supported two-span double-column RC bridge is established, and six numerical simulations of typical light, medium and heavy trucks colliding with the entire bridge with/without CFRP strengthened pier are performed. Based on the simulated results, the effectiveness of CFRP strengthening on the dynamic shear demand, dynamic bending moment and deformation of the impacted pier, as well as the damage/failure and collapse of the entire bridge are further evaluated and discussed. It is found that: (i) compared with brittle shear failure of the bare pier, the strengthened slight-damaged and intact piers both have the excellent lateral consecutive impact resistance with exhibiting shear-flexural and ductile flexural failure modes, respectively; (ii) suppression of the shear damage evolution is beneficial to both strengthened slight-damaged and intact piers to have the higher damage and defamation tolerance to dissipate more impact energy; (iii) the strengthened intact piers in the prototype bridge model can withstand the higher dynamic shear demand and dynamic bending moment but experience the less deformation and damage; (iv) since the deformation and damage of strengthened intact pier in the prototype bridge model under actual vehicular collision are significantly reduced, the vehicular impact resistance and collapse resistance of entire bridge can be improved. [ABSTRACT FROM AUTHOR]

During the last decade, simple solutions of thermal breaks have been developed for steel structures that consist in inserting an intermediate insulating layer (composed of PVC, plywood, elastomer, FRP...) between a bolted end-plate and a steel/concrete support. Experimental tests highlighted that failure modes under bending moment are similar to that of conventional bolted connections particularly in the tensile area, whereas the ultimate resistance decreases. For standard bolted connections loaded by a bending moment, the T-stub concept is used to model the tensile area. This model, extensively used in Eurocode 3, assumes that the end-plate is in contact with a rigid foundation or concrete/grout. T-stub can potentially be used to model the tensile area of bolted connections in presence of intermediate insulating layer. However the current model cannot be directly applied as the end-plate rests on a flexible support. In the present paper, a mechanical model is proposed to firstly model the elastic behaviour of T-stubs in contact with a flexible intermediate layer. The model relies on the Timoshenko beam theory in contact with a Winkler foundation modelling respectively the end-plate and the intermediate layer. The contact pressure distribution being almost linear, simplifications are proposed in this sense. It is demonstrated that simplifications can be considered for standard material used as intermediate layer such as PVC or FRP. An analytical model is also given to calculate the ultimate resistance of T-stubs considering yielding of the intermediate layer. These results are validated by comparison to finite element analysis results performed with ANSYS code using solid and contact elements. This FE analysis highlights a clear distinction between the elastic and elasto-plastic behaviors of these T-stubs particularly concerning prying effects. • Elastic and ultimate models for T-stub in contact with an intermediate layer • Linear contact pressure distribution for the elastic range of behaviour • Significant modification of prying effect for flexible layer after yielding [ABSTRACT FROM AUTHOR]

A new semi-rigid pin joint equipped with a simple assembly procedure provides a promising solution for the realization of modular and rapid assembly of steel-reticulated shells. Because the novel joint can adapt to the complex curvature change of the reticulated shell, it can be arranged in the middle of the reticulated shell member. Moreover, this type of arrangement can significantly reduce the number of assembled joints in the reticulated shell. The purpose of this study was to explore the anti-rotation performance of semi-rigid pin joints in the in-plane bending direction of a reticulated shell. First, through static loading experiments, the mechanical properties of the semi-rigid pin joints were investigated. The parameters considered in the experiment included the diameter of the wing plate pin, thickness of the wing plate, and diameter of the screw rod. To evaluate the static performance of the joint, the parameters of the joint, such as the initial stiffness, ultimate bending moment, and failure mode, were analyzed in detail. The results revealed that the semi-rigid pin joint exhibited good bending stiffness under in-plane direction loads. Simultaneously, a finite element model of the semi-rigid pin joint was established using ABAQUS, and several parameters of the joint were analyzed under the premise of agreement between the test and finite element model. Finally, a theoretical analysis model was established based on the power function model to predict the bending moment-rotation angle (M - Φ) curves of the semi-rigid pin joints under different parameter combinations. The results proved that the prediction formula provided accurate results compared with the experimental results. • A new type of modular assembly system for steel reticulated shells is proposed. • A new type of joint is proposed, which has simple assembly steps and can realize the connection of arc-shaped members. • The anti-rotation performance of the new joint in the in-plane direction of the reticulated shell was experimentally studied. • A formula that can well predict the in-plane direction anti-rotation performance of the joint is put forward. [ABSTRACT FROM AUTHOR]

The experimental investigation and numerical analyses are presented in this paper on cold-formed steel built-up open and closed section beams under either uniform or non-uniform minor axis bending. To the best knowledge of the authors, this is the first study devoted to exploring the effect of non-uniform bending on the behaviour of cold-formed steel built-up section flexural members. In the experimental investigation, the built-up section specimens were assembled by fastening two individual channels as press-braked from G500 and G550 steel sheets. Four-point bending tests of eighteen specimens with varying moment distributions were conducted to examine the flexural performance of the built-up section members experiencing uniform bending and moment gradients. In the numerical simulation, the finite element models were established for the built-up section flexural members and calibrated against the experimental results in terms of moment-deflection response, failure mode and moment capacity. Based on the validated finite element models, additional 300 numerical data of the built-up section beams under uniform and non-uniform minor axis bending were generated through a parametric study. Subsequently, the comparison of moment capacities obtained from the 18 tests and 300 numerical predictions with nominal strengths was carried out to evaluate the appropriateness of the current direct strength method as prescribed in the North American Specification for the built-up section flexural members. Aimed to achieve more suitable strength predictions, the modified design rules were recommended in this study and proven to be generally reliable as well as accurate for the design of cold-formed steel built-up section beams. [Display omitted] • Four-point bending tests were conducted on cold-formed steel built-up sections under uniform and non-uniform bending • Finite element models were established and calibrated against experimental results • Numerical investigation was performed on built-up open and closed section flexural members • Current direct strength method was evaluated based on experimental and numerical data • Design rules were proposed for cold-formed steel built-up section beams experiencing uniform bending and moment gradients [ABSTRACT FROM AUTHOR]

• Tests and numerical analysis of specimens with large width-thickness ratios. • Elastic-plastic local buckling and its effects on hysteretic behaviour of beam-columns. • Design formula for bearing capacity of Q690 high strength beam-columns. To evaluate local buckling and its effect on the hysteretic performance of high-strength Q690 thin-walled H-section beam-columns, cyclic testing was carried out on four H-section columns composed of plates with a nominal yield strength of 690 MPa. Based on China's standard for the design of steel structures (GB 50010-2017), the four H-section columns are categorized as S4 and S5 sections, and the axial load ratio of the columns is 0.2 and 0.35. After the test, the failure mode, second-order effect of bending moment, hysteresis curve, bearing capacity, backbone curve, energy dissipation, ductility and stiffness degradation of the specimens were investigated. The failure mode of the specimens is elastic–plastic local buckling of the column bottom flange and web. The ductility coefficient of the specimens is 2.08–3.04, and they have certain specific deformation and energy dissipation capacities. Following this, a finite element model was established to simulate the hysteretic performance of the Q690 thin-walled H-section beam-columns. The failure mode and hysteresis curve obtained by the finite element simulation corresponded well with the tests. Based on this agreement, a parametric study was carried out to investigate the influence of the flange width-thickness ratio, web width-thickness ratio, and axial load ratio on the local buckling and hysteretic performance of H-section beam-columns. The variation trend of the backbone curve and the bearing capacity were further investigated by the finite element parametric analysis. Finally, a prediction formula for the beam-column bearing capacity was proposed based on the finite element results. The comparison with the test results shows that the proposed formula has sufficient accuracy and can be used in engineering design. [ABSTRACT FROM AUTHOR]

• Validation of a finite element, for moment-axial-shear interaction of RC frames is presented. • Nonlinear force-based finite element formulation is used. • The Disturbed Stress Field Model is used as the constitutive relationship. • Load-deformation responses and failure modes of RC elements are accurately predicted. This paper focuses on a novel finite element formulation which can predict the bending moment-shear force-axial force interaction of reinforced concrete frames and walls, and validate it against 170 experiments available in literature. This distributed plasticity element is established on force-based finite element method, where the relationship between element nodal forces and section forces are exactly known. Hence, element discretization is nonessential when modelling frames using this formulation, reducing the number of degrees of freedom in the numerical model compared to displacement-based formulations. The computations are carried out at four hierarchical levels, namely structure, element, section and fibre. There are two nested iterative procedures at the structure level and the section level. In the existing formulation, these iterative procedures are computationally demanding due to use of initial stiffness matrices. Furthermore, it uses Modified Compression Field Theory at the fibre level, which has inherent drawbacks compared to its more evolved version, the Disturbed stress Field Model. The current study refines the iterative procedures at structure and section levels to fully operate with tangent stiffness matrices to improve the speed of convergence. In addition, the Modified Compression Field Theory is replaced with the Disturbed stress Field Model at the fibre level to compute fibre resisting force for a given fibre deformation, accounting for both averaged behaviour and local crack slip. The novel element is validated by comparing the predicted results with experimental results of 170 tests found in the literature. It is shown that the novel element predicts the load carrying capacity well with an average experimental-to-predicted load carrying capacity ratio of 0.99 and a coefficient of variation of 12.8%. Furthermore, the element can be used to discuss the different failure mechanisms of reinforced concrete frame elements. [ABSTRACT FROM AUTHOR]

Very little guidance exists on the design of steel column base connections subjected to axial compression and biaxial bending moment. In order to develop a design method, an experimental program of 32 tests to failure was carried out to determine the effects of various factors that affect the failure modes, strength and behaviour of unstiffened column base connections under biaxial bending moment. Plate thickness, bolt diameter and axial compression force were set to low and high values in a full factorial experimental design chosen to bring about different failure modes. The program was completed with detailed finite element analyses calibrated with the experimental results. The investigations provide a clearer understanding of the failure modes, strength and behaviour of baseplates under biaxial bending moment. Increases in plate thickness, holding-down bolt diameter and axial force were found to increase the connection strength. The welds at the flange tips of corner bolted base connections under biaxial bending were shown to be vulnerable to premature failure, and the work showed that existing design codes are conservative for the uniaxial bending case. [Display omitted] • 32 experiments were performed on column base connections under biaxial bending moment. • Moment angle, plate thickness, bolt diameter and axial compression were varied. • Increased plate thickness, bolt diameter and compression force increase the strength. • The welds at the flange tips were vulnerable under biaxial bending moment. [ABSTRACT FROM AUTHOR]

• New joint for connecting aluminum rectangular hollow section members is proposed. • Six different full-scale ARH joints are tested under an out-of-plane bending moment. • The M-Φ curves, stress variation, and failure modes of the ARH joint are obtained. • A bilinear model is proposed to summarize the M-Φ curves of the joint. • The influence of different factors on mechanical behavior of ARH joints is analyzed. A new joint system for connecting aluminum alloy rectangular hollow section (ARH) members is proposed to overcome the problem of connecting rectangular tubes using the traditional Temcor joint. The structural performance of the ARH joint system under an out-of-plane bending moment is studied experimentally. The moment-rotation (M-Φ) curves, stress variation, and failure modes of the ARH joint obtained from the tests are discussed. A bilinear model is proposed to summarize the M-Φ curves of the joint. The influence of the key parameters, gusset thickness and bolt quantity on the mechanical behavior of the ARH joint is analyzed. Subsequently, finite element analysis is conducted to investigate the moment rotational behavior of the ARH joint. The comparison between the experimental and numerical results proves that the proposed finite element model is accurate enough and can be used to study the moment resistance behavior of the ARH joint system. The results show that the proposed ARH joint, for connecting rectangular hollow section members, can be considered as a semi-rigid connection. This study provides a reference for the practical application of the ARH joint in reticulated structures made of aluminum rectangular members. [ABSTRACT FROM AUTHOR]

Five Reinforced Concrete (RC) beams strengthened with Basalt Fiber Reinforced Polymer (BFRP) grid in conjunction with Engineered Cementitious Composite (ECC) were tested along with one conventional RC beam for reference to investigate their performance improvement, particularly in shear capacity, due to strengthening. The test results highlighted that the failure modes of the tested beams were dominated with shear-compression failure in the shear/bending moment regions and concrete crushing in the compression part of the pure bending zone. A good bonding performance between the BFRP-ECC composite and concrete substrate was exhibited during the testing process, which can effectively suppress the propagation of diagonal cracks in the shear/bending moment regions. The shear capacity of strengthened RC beams was greatly improved with the increase of BFRP grid reinforcement ratio. Moreover, the reinforcement effect of this strengthening technique was much more effective with the increase of shear-span ratio of the tested RC beams. Furthermore, finite element analyses based on ABAQUS/Standard software were conducted to provide analytical estimations of the shear capacity of the strengthened RC beams. The analytical results revealed that the predicted values agree very well with the test data, which can effectively predict the shear capacity of RC beams strengthened with BFRP-ECC composite. [ABSTRACT FROM AUTHOR]

A composite slab comprised of self-compacting rubber lightweight aggregate concrete (SCRLC) and profiled steel sheeting is a new type of structural element with a series of superior properties. This paper presents an experimental research and finite element analysis (FEA) of the flexural behavior of composite slabs consisting of SCRLC to develop a new floor system. Four composite slabs specimens with different shear spans (450 mm and 800 mm) and SCRLC (0% and 30% in rubber particles substitution ratio) are prepared, and the flexural properties including failure modes, deflection at mid-span, profiled steel sheeting, and concrete surface stain at mid-span and end slippage are investigated by four-point bending tests. The experimental results indicate that applying SCRLC30 in composites slabs will improve the anti-cracking ability under the loading of composite slabs compared with composite slabs consisting of self-compacting lightweight aggregate concrete (SCLC). FEM on the flexural properties of SCRLC composites slabs show that the yield load, ultimate load, and deflection corresponding to the yield load and the ultimate load of composite slabs drop as the rubber particles content increases in SCRLC. The variation of SCRLC strength has less impact on the flexural bearing capacity of corresponding composite slabs. Based on the traditional calculated method of the ultimate bending moment of normal concrete (NC) composite slabs, a modified calculated method for the ultimate bending moment of SCRLC composite slabs is proposed. [ABSTRACT FROM AUTHOR]

A systematic finite element based approach is presented to characterize the interaction between the bending moments and axial forces coming from the connected beams in 2D welded steel joints. The modelling technique is described in the paper, as well as the description of the interaction diagrams between axial forces and bending moments for a series of commercial steel sections. An initial imperfection is included in the finite element model to capture the possible buckling failure modes in the column web and the beam flanges. The approach predicts moment capacities that are very similar to those predicted by Eurocode 3 in the absence of axial forces. Interaction diagrams and moment rotation curves are shown for different levels of axial forces, as well as axial force versus displacements for different levels of bending moments. An investigation is also carried out that shows that the approach leads to axial-bending interaction curves that are path independent. Finally, a nonlinear exponential curve fitting is proposed for the axial-moment interaction diagram. • Finite element method to accurately model the resistance of 2D welded joints with axial force and bending moment interaction • Initial imperfection to capture the possible buckling failure modes in the column web and the beam flanges • Generation of axial force versus bending moment interaction diagrams • Path independent limit surfaces [ABSTRACT FROM AUTHOR]