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The behaviour of the face-plate component under out-of-plane loading has been previously studied, and analytical formulations characterizing the initial stiffness have been proposed. However, research investigating the response of this component under simultaneous transverse loading is limited. This study examines the influence of in-plane transverse compression on the out-of-plane behaviour of the face-plate component in weak axis and tubular beam-to-column steel joints. An experimental test campaign was conducted, covering five representative joint configurations for connections to both I-section and tubular columns. Finite element models of the tested specimen were generated and validated based on the test results. Subsequently, these results were supplemented by two sets of numerical parametric studies, encompassing a total of 329 connections under different levels of transverse loads. The results indicate the detrimental effect of transverse compression on the stiffness and resistance of the face-plate component. Analytical expressions for the reduction of initial stiffness under compressive in-plane transverse loads were proposed and validated, facilitating easy incorporation into design standards. ● Experimental tests conducted on the face plate component under both out-of-plane and in-plane transverse loading conditions. ● Numerical models validated through test findings, which are then extended through a comprehensive parametric study. ● Influence of flange rotational restraint assessed regarding its effects on the initial stiffness of the face plate component. ● An analytical model proposed to evaluate in-plane transverse compression's impact on the initial stiffness of the face plate. [ABSTRACT FROM AUTHOR]

To address the insufficient collapse resistance of the beam-column welded connection (BWC), this study proposes a strengthening beam-column welded connection with truss elements (BWCTE). A static test on a BWCTE specimen with a composite slab was conducted to investigate its failure pattern, final deflection, and the evolution of axial force, bending moment, and collapse resistance. The results indicate that the addition of truss elements increases the peak load and corresponding deformation of BWCTE by 108.6 % and 27.3 %, respectively, compared to BWC. Moreover, the axial force in the composite beam of the BWCTE specimen achieved the yield axial force, facilitating the complete development of catenary action and optimizing beam performance. Subsequently, primary parameters of the truss element were analyzed using refined numerical models. It is recommended that the projected length of the inside leaning limb is within 0.5 to 0.7 times the height of the steel beam, and the thickness of each limb is within 0.6 to 1.2 times the thickness of the beam flange. Then, the working mechanism of BWCTE was explored through theoretical analysis. The resistance process of BWCTE can be divided into elastic, elastic-plastic, plastic, transition, and catenary stages. The loading and deformation synergies between truss elements and composite beams enable the formation of double plastic zones and double strengthening zones at the beam root, effectively delaying the rupture of the stretched beam flange. Finally, a design method for BWCTE is proposed according to theoretical and numerical analysis. • A strengthening beam-column welded connection with truss elements (BWCTE) is proposed. • Failure pattern, final deflection, and the evolution of axial force, bending moment, and collapse resistance of BWCTE are investigated. • Compared to fully-welded connection, the addition of truss elements increases the peak load and corresponding deformation of BWCTE by 108.6 % and 27.3 %, respectively. • The working mechanism of BWCTE is explored through theoretical analysis. • A collapse resistance design method for BWCTE is given. [ABSTRACT FROM AUTHOR]

Composite structures made of concrete-filled steel tubular (CFST) columns and steel beams have gained widespread usage in high-rise and long-span structures, and beam-to-column joints strengthened by an internal diaphragm (ID) are expected to be efficient joint patterns. However, the thickness ratio (η bc) limit of beam-to-column flanges is not considered sufficiently in current design codes and existing studies. Moreover, the previous tests rarely included specimens with a beam flange thickness reaching 40 mm. Thus, three joint specimens were designed and tested under cyclic loadings to further investigate the mechanical properties of the ID-type joints and guide engineering applications. The effects of the thickness ratio of the beam-to-column flange were mainly considered in this study. All beam flange thicknesses were 40 mm. Two failure modes were observed, including excessive development of beam plasticity and failure of local connections. Specifically, as the thickness of column walls decreased, the seismic behaviour, such as the resistance, stiffness and ductility of the joints, deteriorated obviously. Two out of three joint specimens satisfied the AISC requirements for composite special moment frames (C-SMF). Based on the test results, the limit value of the thickness ratio of beam-to-column flange (η bc) has been proposed for design purposes. [Display omitted] • Cyclic tests were conducted on joints between thick-flange steel beams and CFST columns. • Effect of the ratio of beam-to-column flange thickness (η bc) was investigated. • Local connection failure was observed in the beam-to-column flange connection. • The design suggestion about the upper limit value of η bc was proposed. [ABSTRACT FROM AUTHOR]

In steel-bamboo composite beams, the debonding failure and slip behavior of steel-bamboo pure bonding interfaces at the flanges often lead to premature failure of beams and underutilization of material strengths. Therefore, a novel steel-bamboo composite I-beam with composite connections was presented in this study, in which the pure bonding interfaces at the beam's flanges were reinforced by self-tapping screws (STSs). 13 beams were designed and fabricated with interface type, shear span-to-depth ratio, height-to-thickness ratios of bamboo and steel at the web, and width-to-thickness ratio of steel at the flange as main parameters. Then, shear tests and theoretical analysis were performed to evaluate the beam's shear behavior. The results indicated that the debonding failure and slip behavior of the beams were effectively limited, and the shear resistance, deformation capacity, and ductility were significantly improved. The shear resistance of beams was improved by reducing the shear span-to-depth ratio, height-to-thickness ratios of the bamboo and steel at the web, and steel flange width-to-thickness ratio. Finally, the developed analytical models can be concluded to be used to accurately predict the interfacial shear stress at the beam flanges in the serviceability limit state (SLS) and ultimate shear capacity of the beams. • The shear behavior of a novel steel-bamboo composite I-beam with composite connections was investigated. • The debonding failure and slip behavior of beams were effectively limited. • The analytical models were developed to predict the interfacial shear stress and ultimate shear capacity of beams. [ABSTRACT FROM AUTHOR]

This paper developed a novel bolted connection of prefabricated partially encased composite (PEC) beam to concrete-filled steel tubular (CFST) column by end-plates or π-connectors, and two joints with varying design details were tested subjected to cyclic loading. The seismic performance of the developed connections was investigated by experimental and finite element (FE) analysis. It was observed that both the two type connections exhibited concrete crushing within the PEC beam, accompanied by localized buckling and eventual fracture of the flanges in the main steel component of the beam. At the same time, other components were essentially in the elastic phase, such as end-plates, π-connectors, high-strength bolts, and column steel tubes. The bolted end-plate connections demonstrated excellent hysteretic performance, exhibiting high ductility factors. The stiffness, ductility, and energy dissipation capacity of the bolted π-connector connections were significantly diminished due to the influence of relative slippage between the π-connectors and the beams, in stark contrast to the bolted end-plate connection. According to Eurocode 3, the suggested connection configurations exhibited semi-rigid behavior and full-strength characteristics for non-sway frames. • A novel connection of prefabricated partially encased composite (PEC) beam to CFST column was developed. • The seismic performance of the developed connections was investigated by experimental test and finite element (FE) model. • Bolt slippage has a significant effect on the stiffness, ductility, and energy dissipation capacity of the specimen. • The suggested connection configurations exhibited semi-rigid behavior and full-strength characteristics for non-sway frames. [ABSTRACT FROM AUTHOR]

Shear failure is a brittle type of failures, which should be avoided in any structure as it could cause property loss and human casualties. The shear behavior of thin-walled concrete-filled steel tubular (CFST) columns was hence investigated in this study, involving the tests of 24 thin-walled CFST columns and considering the following parameters: shear span-to-depth ratios = 0.15, 0.3, 0.5, 1, 1.5, and 2; confinement factor = 0.63, 1.27, 1.44, and 1.70; and axial load ratios = 0, 0.2, 0.4, and 0.6. The test results revealed the insights of the initial shear stiffness, failure modes, ultimate bearing capacity, load-deflection curves, load-strain curves, and ductility of the specimens. Based on the failure modes, a method is proposed to evaluate the load resistance, and explain the relationship between the shear span-to-depth ratio and the peak bearing capacity. A compression strut mechanism considering the confinement provided by the steel tube flange is also proposed. The effect of axial load on the shear strength of the concrete core is negligible when the axial load ratio doesn't exceed 0.4. The predicted results from using the proposed simple model agree generally well with the experimental results. • Monotonic tests are conducted to obtain the shear behavior of the thin-walled CFST columns designed with major parameters. • Steel tubes and concrete's contributions to shear capacity are clarified by experimental and analytical results. • The exact effects of some parameters on failure modes and shear capacity are explained based on the experimental data. • The formulas on the shear capacity of the thin-walled CFST columns are proposed based on the compression strut mechanism. [ABSTRACT FROM AUTHOR]

Simulations on 192 concentrically braced frames with H-section steel (Q355B) are carried out to investigate their low-cycle fatigue performance. The fatigue life of a steel-braced frame is predicted using a multiaxial fatigue damage parametric model. To depict the fatigue failure sequence and the matching relationship of the fatigue life between the two components in the braced frame, the fatigue life ratio (β) is introduced. This ratio represents the gusset plate's fatigue life to the brace's fatigue life. Simulated results are analyzed, and β is found to be positively correlated with four influencing factors, the width-to-thickness ratio of the brace flange, connection coefficient, ratio of the column length to beam length, and slenderness ratio of the gusset plate. Also, β is found to be negatively correlated with the slenderness ratio of the brace. Based on the Bayesian updating method, a probabilistic model is formulated to predict β of a steel-braced frame. Accordingly, a fatigue design method is proposed, which contributes to avoiding the in-coordination of seismic capacity caused by the significant difference between the brace's and gusset plate's fatigue life within the steel braced frame. The proposed fatigue design method has the potential to serve as a reference for improving design specifications. • The low-cycle fatigue behavior of H-shaped steel braced frames is investigated. • The ratio of gusset plate's fatigue life to brace's fatigue life is proposed to represent their matching relationship. • The key influencing factors on the fatigue life ratio are obtained. • A probabilistic model is proposed to predict the fatigue life ratio. • A fatigue design method is proposed to avoid the in-coordination of components' seismic capacity within the braced frame. [ABSTRACT FROM AUTHOR]

This study proposed a novel replaceable ductile Split-T (RDST) component located at the bottom beam flange to enhance the ductility and energy dissipation capacity of steel structures. The proposed RDST aims to effectively control damage and enable rapid recovery of structural functions in the aftermath of earthquakes. A series of cyclic loading tests under large deformation amplitude was conducted to investigate the plastic deformation capacity of this new type of structural component. The influence of shear span ratio on the specimens' hysteretic behaviours was studied experimentally. Meanwhile, experimental phenomena such as the pinching effect and snap-through buckling which compose the complicated deformation behaviour were evaluated quantitatively. Consequently, methods for quantitatively evaluating the mechanical properties of this new type of structural component were established based on the experimental results and previous discussions on T-stub-type structural components. Moreover, a hysteretic model was developed to precisely describe the specimens' complicated hysteretic behaviour. It is expected to be the key element for further research on the structures with this new type of beam-to-column connection. • Proposed a novel replaceable ductile Split-T (RDST) located at the bottom beam flange of steel frames. • Cyclic loading tests under large deformation amplitude were conducted. • The elasto-plastic behavior of RDST components under monotonic loading was precisely evaluated. • A hysteretic model precisely describing the complicated hysteretic behaviour of the specimens was developed. [ABSTRACT FROM AUTHOR]

Despite the economic benefits of using partially grouted reinforced masonry shear walls (PG-RMSWs) as a seismic force resisting system (SFRS) in low-rise buildings, using such a system in mid- and high-rise buildings is still questionable. This is because the literature lacks comprehensive studies investigating different seismic design provisions adopted for rectangular and flanged PG-RMSWs of aspect ratios greater than 2.0 and failing in flexure. Therefore, this study aims to conduct a comprehensive numerical assessment of the seismic design provisions of the North American masonry standards (i.e., TMS 402/602–22 and CSA S304–14) for designing different categories of rectangular and flanged PG-RMSWs failing in flexure. In this regard, 108 PG-RMSWs were designed and modeled using the Extreme Loading for Structures (ELS) software. Afterward, some changes were proposed to the current seismic design provisions in CSA S304–14 and TMS 402/602–22 for rectangular and flanged PG-RMSWs. In addition, a comparison was made between the seismic design provisions for PG-RMSWs and FG-RMSWs, designed according to each RMSW category, to investigate the expected differences in the behavior based on the applied seismic design provisions. Accordingly, additional 36 FG-RMSWs were designed according to CSA S304–14 and TMS 402/602–22. These additional walls were then modeled on the ELS and compared with their PG counterparts. The results show that both standards can be safely used to design rectangular and flanged PG-RMSWs only when using the two proposed provisions for each standard. For CSA S304–14, the possibility of updating clause 16.8.5.2 is concluded, allowing the use of PG-RMSWs without limitations. New seismic force modification factors were also proposed for TMS 402/602–22 for the design of rectangular and flanged PG-RMSWs. Finally, the comparison between rectangular PG and FG-RMSWs failing in flexure and designed according to CSA S304–14 and TMS 402/602–22 shows that the behavior of PG-RMSWs failing in flexure is comparable to FG-RMSWs under certain circumstances. This study is considered a significant step to prove the potential for more economical and safe usage of PG-RMSWs in mid- and high-rise buildings. • FG-RMSWs and PG-RMSWs were modeled using ELS software. • A numerical assessment of the seismic design provisions for slender PG-RMSWs was conducted. • TMS 402/602-22 and CSA S304-14 were considered in the study. • Two new provisions were proposed for each standard. • New R values were proposed for the TMS 402/602-22 for the design of rectangular and flanged PG-RMSWs. [ABSTRACT FROM AUTHOR]

Highlights • Only web contribution to shear is considered in codes for design of T-section concrete beams. • Experimental testing shows that contribution to shear strength of flanges is not negligible. • This effect may drive to considerable cost savings in new structures. • This effect may become decisive when evaluating the shear capacity of existing structures. • An experimental and parametric numerical study of T-Beams failing in shear is presented. Abstract Shear design of reinforced concrete beams with T section considers only the contribution of the web, mainly provided by aggregate interlock. However, as the load increases and large web crack openings take place, aggregate interlock reduces and shear stresses tend to concentrate near the neutral axis, usually located in the flanges of T beams, whose contribution to shear strength may be not negligible, as it has been experimentally observed. Thus, the contribution of flanges may drive to considerable cost savings in new structures and may become decisive when evaluating the shear capacity of existing structures. To quantify such contribution, a nonlinear 3D-FEA model has been developed and calibrated with the results of shear tests performed on RC T-beams by the authors. Once adjusted, the model has been used to analyze the shear response of beams with different geometry and longitudinal reinforcement, usual in practice. It has been found that, up to certain limits, the contribution of the flanges to the shear strength increases as the amount of longitudinal reinforcement decreases, as the flanges width increases and as the flange thickness increases. The maximum contribution of flanges found in the present study is 31.3% of the total shear resisted. Furthermore, the numerical model has been used to visualize and quantify aspects that are not easy to obtain experimentally, such as the distribution of the shear stresses between the web and the flanges. The present study will contribute to derive a design expression for the shear effective flanges width of T beams. [ABSTRACT FROM AUTHOR]

Highlights • Finite element models of BBC joints were established and verified. • The uniaxial compression bearing capacity of the BBC joint was defined. • Influence factors on the ultimate load of BBC joints were studied. • Formulae of the ultimate load of BBC joints were proposed. Abstract Bolted ball-cylinder joint (BBC joint) is an innovative joint system applied in non-purlin spatial truss structures. According to the theoretical analysis, the fitting formulae of the uniaxial compression bearing capacity of the BBC joint were proposed in this paper. Experiments on 5 BBC joints were introduced briefly at first. The finite element (FE) models were established using ABAQUS and verified by the experimental results. The numerical and experimental results agreed well with each other in failure modes and load-displacement curves. Subsequently, parametric study was conducted to investigate the effects of the dimensions of hollow cylinder, rectangular tube and ribbed stiffener on the bearing capacity of the joint. Finally, the formulae to estimate the uniaxial compression bearing capacity of the BBC joint were obtained by means of regression analysis. And the increasing coefficients of bearing capacity were obtained on the basis of parametric study. The calculation results were verified against the experimental and numerical results. It is indicated that the practical calculation formulae can estimate the uniaxial compression bearing capacity accurately. [ABSTRACT FROM AUTHOR]

Highlights • The effect of a seismic retrofit on distortion-induced fatigue cracking is described. • A repair to stiffen the web-gap region is evaluated with load testing and analysis. • Stiffening the web-gap region is effective in reducing web-gap stresses. Abstract Many steel bridges in the United States designed before the mid-1980s are highly susceptible to distortion-induced fatigue cracking. This vulnerability is substantially increased if the out-of-plane driving force caused by differential girder displacement is increased for any reason. This research examines one such case where a double-deck bridge complex, originally built in the 1960s, was retrofitted to improve seismic performance. As part of the retrofit, single angle K-type diaphragms were replaced with stiffer double-angle cross-type diaphragms. This seismic retrofit led to an increase in web-gap stresses, and within approximately one year following the retrofit, inspectors identified numerous fatigue cracks in the web of longitudinal girders where connection plates terminate near top flanges. A repair measure was implemented to provide a positive connection between the connection plate and the girder flange. The purpose was to reduce the high stress concentrations in the web-gap region by restricting the out-of-plane distortion in the web-gap region. Field tests were carried out in addition to developing finite element (FE) models to investigate the efficacy of the repair technique. The results confirmed a significant decrease in the web-gap stress after implementation of the repair, and a subsequent FE analysis showed that the new load path through the repair angle section did not introduce a new fatigue sensitive area. In fact, the repair resulted in stresses well below the constant amplitude fatigue threshold (CAFT) for this type of detail. [ABSTRACT FROM AUTHOR]

• A type of whole column-section diaphragm RCS joint was proposed. • Seismic behavior of whole column-section diaphragm RCS joints were investigated. • Effects of different joint details were studied. • Shear and bearing capacities of tested joints were evaluated. RC column–steel beam (RCS) frame is one of the most popular hybrid structural systems. Multiple types of RCS joints have been proposed in the last few decades. To avoid undesirable bearing failure, complicated strengthening details were required in RCS joints, which caused difficulties in construction. This study proposed a whole column-section diaphragm type RCS joint with simple details. Compared to most RCS joints, the steel web was cut off at the beam-column interface in the proposed joint, which facilitated the arrangement of stirrups and concrete casting. Moreover, the bearing failure could be avoided since the bearing area of concrete was enlarged and the local bearing stress decreased, requiring no additional strengthening details. To investigate the seismic performance of the proposed RCS joint and the impacts of strengthening configurations, four interior joint specimens were designed, fabricated, and tested under cyclic loading. In addition, joint strengths were calculated using the existing methods. The test results showed that joint shear failure occurred in all specimens. The concrete within the hole in the diaphragm has limited influence on joint behavior. The force in flanges could be fully transferred to concrete through the dowel action of longitudinal reinforcements and friction between the diaphragm and concrete. The ductility of joints was significantly improved due to the confinement provided by face bearing plates (FBPs). The orthogonal FBPs could greatly increase the shear resistance of the joint. The predictions for joint shear strengths following the current calculation methods were significantly conservative. It confirmed that adequate shear capacity could be obtained although the simplified details were used. The conclusions of this research can provide a reference for the engineering application of the RCS hybrid frame. [ABSTRACT FROM AUTHOR]

• Progressive collapse behaviour of composite substructure with fully-welded connections with rectangular web openings (FCRO) was investigated. • FCRO specimen's resistance experiences bending, bending-catenary mixed, and catenary stages. • The specimen with fully-welded connections fractures at the beam root, while the FCRO specimen fractures at the openings. • Expressions for the boundary axial constraint coefficient and attenuation coefficient to FCRO specimen were derived. • A novel construction measure was proposed to enhance anti-collapse capacity of FCRO specimen. This study explores the progressive collapse resistance of composite substructures with the fully-welded connection (FC) and fully-welded connection with rectangular web openings (FCRO). Quasi-static loading tests were conducted to analyze failure modes, internal forces, and resistance mechanisms. The effect of substructure's boundary constraints on its anti-collapse behaviour was investigated through validated numerical models. The results show that the damage mode of the FC specimen involves tensile beam flange fracture at the beam root, while the FCRO specimen experiences fracture of the rectangular web openings. The resistance development of the FCRO specimen includes bending, bending-catenary mixed, and catenary stages, whereas the FC specimen undergoes bending and bending-catenary mixed stages. In the bending-catenary mixed stage, the FCRO specimen exhibits a 69.2% higher maximum resistance and a 15.3% larger displacement compared to the FC specimen. Despite the reduction in flexural capacity, incorporating large rectangular openings in the beam web enables plastic hinge to shift outward at the beam root, promoting the effective evolution of the composite beam's axial force. The study derived expressions for the boundary axial constraint coefficient and attenuation coefficient to the FCRO specimen. Traditional strengthening methods were found to have limited effectiveness in enhancing the collapse resistance of unreinforced composite substructures. Consequently, a novel and effective construction measure was proposed, resulting in a significant enhancement of 78% in maximum resistance and 85% in corresponding deformation of the substructure. [ABSTRACT FROM AUTHOR]

Highlights • A new type of stiffened flange connections is introduced. • Experiments on four types of down-scaled specimens are performed under axial loads. • Results of advanced quasi-static FEA are compared to experimental results. • Failure modes, bolt forces and distribution of stresses are analyzed. • Design approach for the new type flange connection is achieved. Abstract This paper introduces a new type stiffened flange connection called inside and outside double-layered (IODL) flange connection for large circular hollow sections (CHS). This kind of connection not only make full use of the inner space of the circular tubes but also avoid safety problems by using smaller bolts and thinner flange plates. The purpose of the research presented in this paper is to thoroughly analyze the behavior of the connections by an experimental testing program and advanced finite element analysis (FEA) and propose corresponding design method for practical engineering. Experiments on four types of down-scaled specimens were performed. Results of advanced quasi-static FEA, using explicit dynamic solver and ductile damage material model for bolts, are compared to experimental results. Failure modes, bolt forces and distribution of stresses in the upper plates, stiffened plates and end plates are analyzed. Design models for high strength bolts, upper plates, stiffened plates and end plates are proposed. The connections designed according to these models will meet the demand of safety and economy. [ABSTRACT FROM AUTHOR]

Highlights • Contributions of flanges on web shear buckling modes and strengths are evaluated. • FE models of isolated web and visual girder are compared for buckling behaviours. • Buckled mode shape and its influential parameters are examined. • Proposed formula for flange contribution to buckling is shown to be satisfactory. Abstract The present paper deals with the shear buckling response of trapezoidal profiled webs in girders with concrete-filled rectangular hollow section (RHS) flanges. It outlines an experimental work of four girders with shear buckled trapezoidal profiled webs in interactive and global manners. Characteristic strain distributions on the trapezoidal profiled webs are reported. The analysis of load-deformation responses indicates that the trapezoidal profiled web buckled in the global manner suffered greater strength drops at early stage and less strength improvement contributed by the concrete-filled RHS flange in contrast to those buckled in interactive manner with partial local buckling. Finite element models explicitly allowing for isolated trapezoidal profiled webs with varied side boundaries and visual girder models with proposed design ratios are then presented for 572 cases. It is shown that the first eigenmode shape and critical stressing of the trapezoidal profiled webs are most likely influenced when the shear buckling in local manner takes place. Related geometric ratios involved with shear span, web slenderness, trapezoid altitude and subpanel height are examined through a parametric study. Afterwards, an analytical formula incorporating a proposed rigidity ratio as well as a correlated contribution coefficient is proposed for the determining shear buckling strength of trapezoidal profiled webs in the girders with concrete-filled RHS flanges. The proposed formula is verified in contrast to referred ones through a comparative study which can be deemed suitable for the design of trapezoidal profiled webs in girders with concrete-filled rectangular hollow section (RHS) flanges. [ABSTRACT FROM AUTHOR]

A closed form solution for the ultimate tensile resistance of a bolted flange joint is derived considering yield line failure mechanisms developed by Igarashi et al. The position of the prying force is determined based on formulations previously developed by the authors. Under various simplified assumptions and approximations, a design approach similar to that of the Eurocode 3 for T-stubs is proposed. To validate this approach, experimental tests have been performed on six connections of circular hollow sections made of bolted ring flange. A finite element model considering the elastoplastic behaviour of steel and contact conditions has been developed and the results showed a good agreement with experimental results. Based on the FEM model, a parametric study shows that the proposed analytical model is valid for a wide range of connections. [ABSTRACT FROM AUTHOR]

This paper is concerned with the effects of distortion on the lateral buckling of steel beams which have rectangular or square hollow flanges and folded plate webs. The hollow flanges potentially make very large contributions to the torsional stiffness, but flange distortion (in a shear mode) causes a significant reduction in the effective torsional stiffness and in the lateral buckling resistance. In this paper, the shear distortion of the hollow flanges is analysed, and the strain energy stored in a distorted flange is compared with the strain energy stored during uniform torsion of the flange. This comparison allows the development of a suitable parameter for use in the evaluation of the effect of flange distortion on the torsional stiffness of a hollow flange beam. Uniform torsion test results are used to confirm the significance of this parameter. Finite strip analyses of simply supported hollow flange beams in uniform bending show that there is a significant interaction between distortion and uniform torsion during lateral buckling, which may be approximated by combining their flexibilities. More accurate finite element analyses show that the finite strip predictions are conservative. An approximate method of predicting the effects of flange distortion on elastic lateral buckling is presented which shows good agreement with the finite element predictions. [ABSTRACT FROM AUTHOR]

The bolted-flange connection is used to connect rectangular HSS columns in prefabricated multi-story and high-rise steel structures. It may subject to coexisting axial compression, bending moments and shearing under the combination of dead, live, wind loads or earthquake action. The bearing performance is different from that of bolted-flange connections used in pipelines, towers and mast structures. To investigate the bearing performance of a connection subjected to coexisting compression, bending moments and shearing, static tests and a finite element analysis (FEA) were applied to 12 column-to-column bolted-flange connections with different flange thicknesses, bolt edge distances, flange edge widths and bolt hole diameters, as well as one column without connection. The effects of flange thickness, bolt edge distance, flange edge width, and bolt hole diameter on the stiffness and strength of connections, bolt tension levels, and contact forces between flanges were obtained as well as effects on the failure mode and mechanisms of the connections. Flange thickness was found to have a considerable impact on the performance of connections, while the bolt edge distance and flange edge width were found to have a lesser effect. The FEA results agree well with the test results, verifying the finite element model (FEM). Some performance results that could not be obtained through testing were obtained. Based on yield line theory and T-stub analogies, the load transfer mechanism of bolted-flange connections was obtained and formulas for yield-bearing capacity are proposed. The results obtained from the formulas agree well with the test and FEA results. [ABSTRACT FROM AUTHOR]

• Tests and numerical analysis of the steel–concrete composite beams strengthened with NSM CFRP systems. • Effects of the end anchorage and the number of CFRP bars on the flexural performance of strengthened composite beams. • Parametric studies based on the FE model of the composite beams strengthened with NSM CFRP systems. Compared with conventional strengthening methods, the near-surface mounted (NSM) technique is more suitable for strengthening steel–concrete composite beams, especially at the hogging-moment regions. This paper investigates the flexural performance of steel–concrete composite beams strengthened with NSM CFRP systems. Four-point bending tests are carried out on four composite beam specimens, including one control beam without strengthening and three strengthened beams with NSM CFRP systems. The failure mode, ultimate load-carrying capacity, deflection distribution, and material strain distribution of the composite beams are presented, based on which the effects of the anchorage method and the number of CFRP bars are studied. The test results demonstrate that the main failure mode of the strengthened beams is the buckling of the steel beam. Compared with the control beam, the load-carrying capacity of the strengthened composite beams with two and four CFRP bars is increased by 10% and 20%, respectively. The use of end anchorage has a slight effect on the flexural capacity of the strengthened beams, while significantly improves the ductility during the later stage of loading. In addition, a nonlinear finite element (FE) model is proposed and calibrated, based on which a parametric study is performed to investigate the effects of the length and section area of CFRP bars, the spacing of grooves, and the thickness of bottom steel flange on the ultimate load-carrying capacity of the strengthened beams. [ABSTRACT FROM AUTHOR]

• Finite element models were established for analysing the linear elastic behaviour of IGTCWs under uniform bending. • The distribution characteristic and mechanism of normal stresses in flanges of IGTCWs were investigated in detail. • A secondary transverse moment theory was improved. • The formulae were proposed for calculating normal stresses in flanges of different cross-sections of IGTCWs under uniform bending. I-girders with corrugated webs (IGCWs) are a new type of structure that has been increasingly used in engineering. The normal stress distribution in flanges of IGCWs is quite complicated compared with that of conventional I-girders under in-plane loads. This study numerically and theoretically investigates the normal stress distribution rules and mechanisms in flanges of I-girders with trapezoidal corrugated webs (IGTCWs) under uniform bending in the elastic stage. First, finite element (FE) modelling was developed using ABAQUS software and verified by the available experimental results. Based on the verified FE models, a detailed analysis of the normal stress distribution in flanges of IGTCWs was performed. The results show that the normal stresses are nearly uniformly distributed over the flange in cross-sections with inclined web folds. Normal stresses in cross-sections with parallel web folds are approximately linearly distributed along the flange width, with stresses away from the corrugated web side being much larger than those near it. Its mechanism is explored using a secondary transverse moment theory, which is improved and completed by considering the proposed effective cross-section coefficient and equivalent width coefficient for the action of shear flow. The reliability of this theory was verified through comparison with the normal stress difference and distribution results of the supplementary FE models. Finally, the formulae for calculating the normal stresses in flanges of different cross-sections of IGTCWs under uniform bending are presented. These formulae suggest that secondary normal stresses generated by secondary transverse moments in cross-sections with parallel web folds account for 7% to 13% of the total normal stresses and cannot be ignored in the stress analysis. [ABSTRACT FROM AUTHOR]

• Parametric analysis conducted on seven variables with verified finite element model. • Current codes over-estimate the effective flange width of mass timber composites. • Web spacing and shear connection had greatest impact on effective flange width. • Flange thickness and web width also influenced effective flange width. • Flanges' modulus of elasticity did not significantly impact effective flange width. Mass timber composites (MTCs), where the webs are typically spaced 750–2000 mm apart, have shown potential in overcoming span limitations of conventional flat slab mass timber floors. However, fundamental research investigating the non-linear stress distribution (i.e., shear lag) in the flanges is required. While this behaviour has been simplified in design for other materials using the concept of an effective flange width (EFW), no guidance exists in international design codes for mass timber composites. In the current study, a parametric analysis was conducted on a mass timber I-beam under positive bending where the effects of web spacing, beam configuration (edge or interior placement), shear connection stiffness, concentrated versus uniform loading, web depth, web width, flange thickness, and flange modulus of elasticity on the EFW, were investigated. The reference section in the finite element model consisted of a glued-laminated timber (GLT) panel for the flanges, a glulam beam web, and a fully composite glued connection between elements. The results have shown that existing design code provisions, even those meant for light-frame wood members, over-estimate the EFW of GLT-glulam I-beams. The web spacing, shear connection stiffness, loading type, flange thickness, and web width were observed to be the most influential parameters on the EFW of GLT-glulam MTCs. Between the upper and lower boundaries of connection stiffness, a sharp increase in the EFW was observed below the point of full composite action due to the section beginning to behave as three separate elements. Although, the decrease in composite action resulted in an overall decrease in the bending stiffness of the section. For GLT-glulam MTCs, the modulus of elasticity (MOE) of the GLT flange was not observed to significantly affect the EFW for high degree of composite action configurations. A small increase in the EFW was observed when the degree of composite action was relatively low. Ultimately, the development of equations for quantifying the EFW of MTCs is key to their increased adoption but requires the expansion of the current study to include other mass timber elements, as well as experimental data investigating the most significant parameters identified herein. [ABSTRACT FROM AUTHOR]

Eurocode 3 (EC3) states that the shear design resistance of a plate girder is given by the sum of the web resistance and the flanges contribution, being these calculated separately. The accuracy of these provisions is normally assessed by comparison with the results of numerical simulations using numerical models duly validated with experimental tests. However, the web resistance alone cannot be directly obtained by the numerical model. The usual procedure is to calculate the numerical resistance of the web by subtracting the flange contribution, obtained using the EC3 expression, from the ultimate shear strength directly predicted by the numerical model. Consequently, the accuracy of the EC3 expression to predict the flanges contribution may influence this assessment. Hence, the accuracy of the EC3 design expressions to calculate the contribution from the flanges to shear buckling is evaluated here. An improvement on the calculation of the distance c , which defines the position of the plastic hinges that forms in the flanges, is proposed. The ultimate shear strength predicted by EC3 has been compared with numerical results at both ambient and elevated temperatures, considering the original and proposed values for the distance c . [ABSTRACT FROM AUTHOR]

Prefabricated steel structure systems have become a new trend in the development of steel structures. In particular, earthquake-resilient steel structures have become a hot issue in the field of structural seismic research. Based on the idea of damage control and a new kind of energy-saving, material-saving and environmentally friendly sinusoidal corrugated web, this paper put forward a new type of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint (PSCWJ). Then, its constitution, its mechanics mechanism and its seismic design requirements are introduced. After considering the influence of the bolt binding coefficient, the overall bending of the binding section and the overall instability of the flange cover plate, the design theory of the earthquake-resilient PSCWJ is established. Through 55 examples of PSCWJs, the rationality of the design theory proposed in this study is verified, and a reasonable value range of the middle bolt interval on the flange cover plate is determined. During the process of theoretical derivation, the influences of many design parameters are considered, such as the section parameters of the sinusoidal corrugated web beam and cantilever beam, the thickness of the flange cover plate, the material properties of the flange cover plate, the diameter of bolts, the middle bolt interval and the weaken rate of the cover plate. Research shows that the design theory proposed in this paper can predict the yield load of PSCWJ accurately and effectively control the ultimate bearing capacity of PSCWJ. The PSCWJ designed through this theory has good bearing behaviour and ductility, which can make sure the main members, such as the beam and the column, remain in an elastic range and meet the requirements of earthquake resilience. [ABSTRACT FROM AUTHOR]

Failure modes and their corresponding tension strengths of thread-fixed one-side bolted T-stub were investigated experimentally and theoretically. The thread resistances of bolts fixed directly to plates were evaluated by experimental analysis. Except for the three failure modes described in the current Eurocode 3, two new failure modes and their corresponding design methods were proposed, which were (a) hole thread failure and (b) T-stub flange yielding with hole thread failure. Influences of the bolt pre-tension force, the thickness of T-stub flange, the existence of the standard nut, the screw depth of the bolt on the failure mode and the ultimate tension strength were studied. The bolt pre-tension force had little influence on the ultimate tension strength; however, it could improve the initial stiffness of the connection. The ultimate tension strength and tension stiffness of the T-stub increased with the increase in flange thickness. For the T-stub with thin flange, the thread hole could also provide sufficient clamping force to ensure the bolted T-stub not fail by thread failure. The existence of the nut did not improve the yield strength of the T-stub; however, it could prevent the separation of two T-stubs after flange yielding, thus the ultimate tension strength was increased. It depended on the screw depth whether the partially screwed bolt was failed by thread failure or bolt failure. Ultimate tension strengths of the T-stub measured from tests were much higher than those calculated by design equations. And under the design load, the bolted T-stub was still in elastic state, which demonstrated the applicable of the thread-fixed one-side bolted T-stub. [ABSTRACT FROM AUTHOR]

Two new concrete bridge superstructure systems for short and medium span bridges are presented. The investigated systems consist of adjacent hollow precast concrete beams with and without concrete topping. The proposed configurations are compared with traditional adjacent box beam and decked bulb tee systems for spans that range from 24.4 m to 45.7 m. It is demonstrated that the proposed system that features concrete topping (PS2) is lighter than the adjacent box beam system, requires fewer strands, provides shallower superstructure depths, and exhibits lower cambers for spans equal to 24.4 m and 30.5 m. PS2 addresses the reflective cracking problems manifested in adjacent box beam systems by shifting the location of the longitudinal connections to the bottom flange and away from traffic loads. The system that features no topping (PS4) is slightly heavier than the decked bulb tee system, but features shallower superstructure depths, requires fewer strands, and exhibits lower live load deflections and camber. Transverse bending moments demand in PS4 are reduced compared to the decked bulb tee system due to the smaller span provided by the two web supports. Live load distribution factors (LLDF) for PS2 and PS4 can be conservatively estimated using AASHTO provisions for adjacent box and decked bulb tee systems, respectively. [ABSTRACT FROM AUTHOR]

• An experimental investigation on cold-formed steel Z-sections was presented. • Test specimens were made of high strength steel undergoing web crippling. • Web crippling test strengths and load–displacement relationships were measured. • A reliability analysis was performed to assess the design rules. • North American Specification and European Code design rules were assessed. This paper presents the results of an experimental investigation comprising 55 tests on cold-formed high strength steel Z-sections having different stiffened flanges undergoing web crippling. The test specimens were brake-pressed from high strength zinc-coated grades G450, G500 and G550 structural steel sheets. The material properties of the cold-formed steel Z-section specimens were obtained by tensile coupon tests. The experimental program consisted of 4 series of Z-sections having different stiffened flanges, web slenderness, material strengths, bearing lengths and subjected to different loading conditions. The loading conditions were End-Two-Flange (ETF), and Interior-Two-Flange (ITF) loadings as specified in the North American Specification for cold-formed steel structures. The web crippling test strengths and load–displacement relationships of the Z-section specimens were obtained from the tests. The loading condition and bearing length had a considerable effect on the web crippling test strengths. The presence of lips of the Z-sections increased the web crippling test strengths of the specimens loaded under ITF loading condition. The web crippling test strengths were compared with the design strengths calculated using the current North American Specification and European Code for cold-formed steel structures. In addition, reliability analysis was performed to assess the reliability of the design rules. Generally, it is found that the predictions obtained from the North American Specification are unconservative for most of the cold-formed high strength steel Z-section specimens, except for the specimens with unstiffened flanges loaded under ITF loading condition, while the European Code conservatively and reliably predicted the web crippling strengths for all the Z-section specimens loaded under ETF and ITF loading conditions. A modification of the constants used in the European Code design equations is proposed in order to provide more accurate and reliable web crippling design strengths. [ABSTRACT FROM AUTHOR]

• 1. Numerical analyses are performed on three types of bolted connections. • 2. The effectiveness of the conventional segment approach is investigated. • 3. Sufficient pretension force is beneficial for all three types of connections. • 4. The C1 wedge connection is rather insensitive to the variation of pretension force. The overall competitiveness of offshore wind turbine towers is significantly influenced by the selection of the connection. The following three types of connections: a conventional bolted ring flange (RF) connection, ring flange connection with defined contact surfaces (RFD), and C1 wedge connection (C1-WC) are considered. A quantitative comparison is made to enhance performance in a specific condition and enable further optimization of these connections in engineering practices. The study compares the tensile behaviour and fatigue performance of these connections by validated finite element (FE) simulation and analysis. The proposed FE modelling is based on a realistic geometry including all contacts present in the connections, steel full-range stress–strain relationship and ductile damage model. The efficiency and accuracy of the FE models are validated through the comparison with the performed tests. Then, a series of parametric FE analyses are carried out to examine the impact of the applied boundary conditions, bolt pretension level, and steel grade on the behaviour of connections. Load-displacement curves, bolt evolution curves, and stress responses are analysed to compare their tensile behaviour. The effectiveness of conventional segment specimen testing is evaluated thoroughly. For the fatigue performance of connections, the results indicate that the segment specimen testing substantially underestimates the fatigue performance of C1-WCs. This discrepancy is essential to be considered in the tower design. It is also noted that C1-WCs are rather insensitive to the variation of pretension force level, which show superiority to avoiding the difficulties associated with typically bolted joints. This research provides in-depth knowledge for the practical application of such connections and further optimization. [ABSTRACT FROM AUTHOR]

• Bolted connections between T-shaped section column and I-section beam with L-stubs were proposed. • Three full-scale specimens were analyzed by cyclic test and FE analysis. • Hysteretic behavior, performance indicator and ductility of the joint were analysed. • The influences of friction coefficient, end-plate thickness or bolt quantity were conducted by FE analysis. • Formulas for the slipping, yield and ultimate resistance were proposed and verified. Bolted beam-to-column connections can reduce the construction period and are proper for prefabricated structures. Based on the traditional bolted connections, a beam-to-column bolted joint with L-stubs was proposed to connect the I-section beam and T-shaped section column using only bolts on site. Changing the parameters of L-stub end plate thickness, stiffener layouts, friction coefficient, column web thickness and the quantity of the beam flange bolts, experimental and numerical investigations were conducted on the cyclic performances of the proposed joint, and the hysteretic curve, skeleton curve, deformation characteristics, ductility and rotational capacity, as well as the slipping, yield and ultimate resistances, were analyzed. According to the results, the proposed joint can perform as a rigid joint without slipping under small earthquakes, and develop considerable ductility and energy dissipation ability under moderate or large earthquakes by slipping and plastic deformations. Increasing the friction coefficient can improve the slipping moment, and the stiffeners can improve the joints stiffness. The joint energy dissipation capacity could be increased by adding bolts. Based on the analysis, recommended parameter values for the joints were provided, and simplified formulas were proposed to calculate the slipping, yield and ultimate moment resistances, providing satisfactory accuracy when compared to the test and finite element results. [ABSTRACT FROM AUTHOR]

• Withstanding local damage and collapse is critical for steel-frame structures. • Tests on a novel connection with flange openings are reported. • Specimens include flange openings with various diameter, number, and distance. • Special fracture and failure modes occurred in the connection types. • Specimens with V-shaped reinforcing plates are studied to resist external load. Improving the ductility of the structure to withstand local damage and prevent progressive collapse is critical for steel-frame structures. In this study, a novel principle of beam-to-column connections was developed, which arranged openings at the beam flange to form a flange-opening section (FO). First, experimental investigations were conducted on two FO substructures, considering their deformation capacity, failure modes, internal force evolution, and resistance mechanism development. Second, numerical simulations verified by experiments were conducted to further investigate the number n , distance l , and diameter d of the flange openings, and the results were compared with those of the case that had no weakening of mechanical properties. Third, because some flange openings weakened the mechanical properties of the structure, specimens with V-shaped reinforcing plates (FOV) were studied. The results indicated that the mechanical properties of the FO specimens increased with n , decreased with an increase in d , and increased with l. The mechanical behavior of the new beam-to-column connections using flange openings and reinforcing plates was studied to relocate the plastic hinge, realize a second path, and successfully improve the progressive collapse resistance of the steel frame structure. [ABSTRACT FROM AUTHOR]

• Shear forces are nonuniform around special-shaped slab-column connections (SS-SCCs) • Impact of slab openings is dependent on their size and location around the column. • If needed, slab openings should be located between the flanges of SS-SCCs. • The ACI 318–19 punching shear design provisions require revisions for SS-SCCs. • ACI 421.1R-20 can be used to estimate the concentric punching capacity of SS-SCCs. Punching shear of special-shaped columns supporting reinforced concrete two-way slabs has been addressed in design codes since the late 1970s. While these provisions have existed for over 40 years their basis is unclear as previous studies related to the punching shear behaviour of irregular column geometries, such as L, T, and cruciform shapes, are limited. In this paper, the punching shear behaviour of L, T and cruciform slab-column connections, with or without slab openings near the connection, under concentric vertical loading is studied using a three-dimensional nonlinear finite element model (FEM) implemented in Abaqus/Explicit. The nonlinear FEM, based on the concrete damaged plasticity model, is used to study the influence of both the opening size and location on the punching shear behaviour of special-shaped (irregular) slab-column connections of various sizes. Based on the FEA results, the ideal location for openings around special-shaped slab-column connections (SS-SCCs) is between the column flanges. This location minimizes their negative influence on concentric punching capacity and is also beneficial architecturally. Finally, the accuracy of the ACI 318–19 punching shear provisions is evaluated. Based on the FEA results modifications to the existing provisions are necessary, particularly to account for the location of openings around special-shaped slab-column connections. [ABSTRACT FROM AUTHOR]

• Combining with strain hardening cementitious composites (SHCC) material and honeycombed columns, a novel composite column is proposed, and simulation analysis for axial compression behavior of the columns is conducted. • The most vertical load is borne by SHCC, and the steel web basically does not undertake the load. • The holes on the web leads to stress concentration, and a predicted model of yield zone of steel is proposed. • The role of honeycombed web on the composite columns is equivalent to that of lattice plate on the lattice special concrete filled steel tubular columns, and the formula for axial compression bearing capacity of novel columns is derived. Strain hardening cementitious composites (SHCC) as a newly emerging material has bright application prospect with good ductility and multiple microcracking behaviors. Combining with SHCC new material and new honeycombed steel structures, novel composite columns with steel tube SHCC flanges and honeycombed steel web (STHSC) is proposed in this research. To study the axial compression behavior of STHSC, the finite element model of STHSC is established by ABAQUS. The effects of different parameters on the bearing capacity, ductility and stiffness of STHSC are explored, and the results show that the constraint effect of steel tube has a significant role in ultimate bearing capacity of STHSC. The ductility of STHSC is mainly above 3.50, and STHSC has great initial stiffness. The observed failure mode is categorized into shear failure with local bulging at the middle section. Steel tube has Ludels slip lines and SHCC presents multiple microcracks that lie at an angle of 45 degrees to the edge. The range of expansion displacement for SHCC is from 0.009 to 0.012 times as the length of STHSC. The reasonable model for the yield zone of steel under four stages is described. Moreover, the honeycombed steel web has an excellent role in connecting both flanges, which is equivalent to the effect of lattice plate on the lattice special concrete filled steel tubular columns. Finally, a calculated formula for axial compression bearing capacity of STHSC has been derived with high precision. [ABSTRACT FROM AUTHOR]

• Flexural performance of CWFBs with CHCSs was verified by out-of-plane flexural tests. • The CWFBs with CHCSs had shear lag effects in both the tension and compression zones. • The effect of loading method and slab width on CWFB effective width was analyzed. • The equation to calculate the effective width of the CWFB was deduced theoretically. To investigate the flexural performance and effective flange width of composite wide flat beams (CWFBs) with composite hollow core slabs (CHCSs), four CWFB specimens with double-sided CHCSs were tested and analyzed. The test results indicated that all specimens showed typical flexural damage. The CWFB with CHCSs had shear lag effect in both tension and compression zones. Increasing the width of the CHCSs resulted in a greater effective width, stiffness, and load carrying capacity of CWFB with CHCSs. Compared with the three-point loading method, the effective width of CWFB with CHCSs was larger for the four-point loading method and the uniform loading method. In addition, finite element models (FEMs) of the tested specimens in MSC. Marc software were validated by the test results, and 30 FEMs were further analyzed. Finally, the equations for calculating the effective width were obtained for the CWFB with CHCSs under uniform, four-point and three-point loads. [ABSTRACT FROM AUTHOR]

The prying action as a vital phenomenon in the bolted connections plays a major part in the behavior of steel connections. It is worth mentioning that prying force location has been considered to be at the edge of the flange in the T-stub model. Present research aims to investigate the prying force magnitude and location in the T-stub connection based on the energy method. Therefore, analytical formulas for the ratio of the prying force to the applied load and prying force location with and without considering shear deformation effect were proposed based on the energy method for bolted connections with no pretension. Results obtained from the formulas were compared with the results of the experimental and numerical models. Based on the obtained results, it was understood that despite previous assumptions that the location of the prying force is at the edge of the flange for all the cases, the prying force location depends on the thickness of the flange and the bolt distance from the web of the T-stub. Hence, considering prying force location at the edge of the flange underestimates the real value of the prying force resulting in premature failure of the bolt and connection. [Display omitted] • The ratio of the prying force to the applied load is obtained by the energy method. • Prying force location can be obtained based on the energy method. • The shear deformation effect is considered on the prying action. • Considering the prying force location at the edge of the flange is unconservative. [ABSTRACT FROM AUTHOR]

• Test on Thread-fixed One-side Bolts (TOB) bolted T-stubs with arc-shaped flange to steel tube under tension was conducted. • Three failure modes were found in the test and analysed. • A comparison between square tube and circular tube in TOB bolted connection was conducted. • The Finite Element Model (FEM) wan established and verified. • A simple design model of tube wall with the straight yield line pattern to estimate the tensile yield strength was proposed. Tensile tests and Finite Element (FE) analysis were conducted on the Thread-fixed One-side Bolts (TOBs) bolted T-stub with arc-shaped flange to steel tube in this paper. Critical parameters were determined as the thickness of tube wall, the outer diameter of steel tube, the thickness of arc-shaped flange, and the center angle between bolts. Test results revealed that the connection would encounter three typical failure modes, which were: failure mode 1, thread shear failure with yielding of tube wall; failure mode 2, complete yielding failure of tube wall; failure mode 3, thread shear failure with yielding of T-stub arc-shaped flange. Developed FE models are verified and used to analyze the yield line pattern of tube wall, the hoop stress distribution of cross-section of tube wall, and the shear acting on bolt shank. Based on the experimental and numerical results, preliminary analytical models and design methods are proposed to estimate the tensile yield strength of specimens under different failure modes. [ABSTRACT FROM AUTHOR]

• Study of the behavior of two-way concrete floor system reinforced with FRP stay-in-place structural forms. • A three-dimensional FE model was developed and verified with experimental results. • The FE model evaluated different key parameters in the two orthogonal directions. • Modeling of adhesively bonded and mechanically fastened connections between FRP sections. A novel concrete floor design, featuring embedded glass fiber-reinforced polymer (GFRP) stay-in-place (SIP) forms adhesively bonded to the bottom flanges of GFRP I-beams has been developed. The paper presents a comprehensive finite element analysis (FEA) of this system with emphasis on the two orthogonal directions, namely perpendicular and parallel to the I-beam. The former incorporates the critical adhesively bonded connection which governs failure. The model incorporates material and geometric nonlinearities, appropriate interfacial and contact relations, robust failure criteria of the constituents, and was successfully verified using experimental results. The study showed that increasing the I-beam size by 33 % resulted in increasing the ultimate load (P max) by 25 %, mainly due to increasing the area of the adhesively bonded joint between the I-beam and SIP form. When mechanical fasteners were added to the connection, failure shifted to transverse rupture of the I-beam along its web-to-flange junction at a P max 1.8 to 2.8 times higher than that of adhesively bonded joint. A noticeable increase in cracking load occurred when the concrete strength varied 20 to 40 MPa, although led to slight change in P max due to failure still remaining by debonding. Increasing the slab thickness by 11 and 22 %, increased P max by 10 and 14 %, respectively, where debonding also governed. The floor behavior parallel to the I-beam was studied under different loadings and boundary conditions. [ABSTRACT FROM AUTHOR]

• An innovative connection with the core tube and self-tapping bolts was proposed. • The quasi-static tests and finite element analyses were conducted on the test specimens. • The formulas for calculating the bearing capacity of the new connection were proposed based on the yield-line theory. • The design criteria for the novel connection were further proposed. This study proposes a column-column connection with self-tapping bolts, a core tube, flange plates, and high-strength bolts for a prefabricated steel structure, which can avoid on-site welding of traditional steel structure closed section columns and realize efficient assembly of vertical steel structure components. To determine the mechanical characteristics of the self-tapping bolt core tube flange column connection (SCFC) and the effect of the core tube and self-tapping bolts on SCFC, quasi-static tests were performed. According to the test results, altering the core tube thickness within a specific range had no discernible impact on the SCFC's seismic performance metrics, including hysteresis performance, skeleton curve, and stiffness degradation. The failure modes of test specimens were all steel fractures at the column foot, proving that SCFC can realize the seismic design goal of "strong joint, weak member." The force mechanism of the SCFC and slip mechanism of the self-tapping bolt were explored. A finite element model (FEM) was established, and the results agreed well with the test results, confirming the accuracy of the FEM. Finite element parametric analyses were performed to further clarify the impact of the thickness of the core tube on the connection performance. Combined with the test and FEM results analyses, the bearing capacity calculation formulas of the SCFC were proposed based on the yield-line theory and verified by the results of the test and FEM. The design criteria for the SCFC were further proposed. [ABSTRACT FROM AUTHOR]

This paper presents a research on two types of beam-to-tubular column connections for progressive collapse prevention. Two specimens, each comprising a central column stub and half of the beam span on both sides, were constructed to represent these two types of connections. One specimen (ST-WB), had a conventional welded flange-bolted web connection, and the other (ST-WBR), which was modified by a special reinforcing technique based on the connection detail of ST-WB, had a reinforced welded flange-bolted web connection. The specimens were subjected to a monotonically increasing vertical displacement of the central column to observe their behaviors under a central-column-removal scenario. Computational simulations of the tests were carried out using detailed finite element models. The analyses provided insights into the behaviors and failure modes of the connections, including their capacities to carry the tensile forces that developed in the beams. Both the experimental and computational results demonstrate that the reinforced welded flange-bolted web connection can make the bottom flange continue to transfer force effectively after the weld failure, which is beneficial to the continuous development of axial tensile forces in the beams. As a result, the assembly with the reinforced welded flange-bolted web connection can provide a greater vertical resistance under a column removal scenario. Based on above observations, the reinforced welded flange-bolted web connection is proved to have a better performance in terms of strength and deformability than the conventional welded flange-bolted web connection, and the special reinforcing technique can be used to enhance structural robustness for progressive collapse prevention. [ABSTRACT FROM AUTHOR]

Despite the increasing usage of thin and high strength steel roof battens in the roof structures of low-rise buildings, recent cyclones and storms have shown that they prematurely fail at their screw fastener connections to the rafters or trusses due to the screw heads pulling through the batten bottom flanges. Such pull-through failures can lead to catastrophic failures of the entire roofing systems as observed during recent high wind events. Therefore a detailed experimental study consisting of both small scale and full scale tests was undertaken to investigate the pull-through failures of roof battens under wind uplift loading in relation to many critical parameters such as screw fastener tightening, roof batten geometry, batten thickness, steel grade, screw fastener head size and screw fastener location. Effects of underside surface and edge details of the screw fastener head, and screw fastener types were also considered. This paper presents the details of the tests conducted in this study and the pull-through failure load results obtained from them. Finally it presents the details of suitable design rules and capacity reduction factors developed in this study that can be used to accurately determine the design pull-through capacities of steel roof battens under wind uplift loads. [ABSTRACT FROM AUTHOR]

This paper deals with an experimental and theoretical assessment of the shear strength of reinforced concrete beams with and without a minimum amount of transverse reinforcement. Various shear transfer mechanisms contribute to the shear strength. The contributions of aggregate interlock, residual tensile stresses at the crack tip, dowel action, and shear strength of the shear reinforcement depend mainly on the opening and sliding behavior of the critical shear crack, which is directly linked to its shape. In this paper, the kinematics of the diagonal crack is investigated in 20 test specimens by using three-dimensional digital image correlation. In this test series the influences of the member depth, the cross section, the type of concrete, and a minimum amount of transverse shear reinforcement on the shear behavior are investigated. Based on the full-field optical measurements and the use of different constitutive laws from literature an estimation of the contributions of the various shear transfer mechanisms is performed. Further, an evaluation of their impact on the shear strength at failure including the influences of the investigated parameters is carried out. An explanation for the pronounced size effect for beams without any transverse reinforcement is given. Moreover, the importance of aggregate interlock as well as the effect of the presence of flanges for beams with and without stirrups is shown. A comparison of the experimental results with the sum of the contributions to the shear strength by each mechanism (based on the measured crack kinematics) yields reasonable agreement. [ABSTRACT FROM AUTHOR]

A series of six one-third scaled reinforced concrete (RC) structural walls with irregular or regular openings were tested to investigate the effects of size, arrangement, and irregularities of the openings on the seismic behaviour of RC walls. The crack pattern development, failure mechanism, and hysteretic responses of tested specimens are presented. The stiffness deterioration and equivalent hysteretic damping (energy absorption capacity) of tested specimens are compared and discussed. Another series of six rectangular walls with openings, which are tested by Yanez et al., are also introduced for quantification of the flange effects on seismic behaviour of RC walls with openings. It is found that flanges could significantly increase ultimate strength but reduce deformation capacities. Moreover, flanges may change the failure mode of rectangular walls from ductile flexural failure to brittle sliding shear failure. Flanges may aggravate the concrete crushing, spalling as well as buckling and fracture of vertical reinforcements. However, concrete crushing and rebar fracture is mainly concentrated in the flanges. [ABSTRACT FROM AUTHOR]

• Two novel design strategies for composite connections were proposed. • Three half-scale composite connection specimens were tested. • Nonlinear finite-element modeling of the composite connection was performed. • Design parameters for practical design applications were recommended. To reduce the negative effects of composite action, this study proposes two novel design strategies for composite connections with a uniaxial symmetric steel-beam section. This work experimentally and numerically elucidates the behavior of composite connections proposed by widening or reducing beam bottom flanges. Cyclic testing of three half-scale specimens is conducted to verify the proposed connection details. Detailed test observations and results are reported. Cyclic curves and strain development at key positions are experimentally obtained. Results show that a composite connection with only widened beam bottom flanges performs considerably better than that with only reduced beam bottom flanges. Nonlinear finite-element modeling of the composite connection with only widened beam bottom flanges is performed as a supplement to the experimental study. Results show that good workmanship and sound welding quality are required to provide a reliable composite connection. The concrete slab slightly affects the neutral axis of the composite beam under negative bending, while the neutral axis shifts significantly toward the beam top flange under positive bending. The proposed composite connection with only widened beam bottom flanges can effectively move the plastic hinge away from the column face and thus achieve more reliable structural characteristics. Based on the parametric study and experimental results, the design parameters for practical design applications were recommended. [ABSTRACT FROM AUTHOR]

• 15 hybrid welded T-section stub columns were tested under axial compression. • Material properties and residual stresses were measured. • Numerical models were developed. • Extensive parametric studies were carried out. • Design codes and design approaches of DSM and CSM were evaluated and compared. Comprehensive experimental and numerical investigations on hybrid T-section stub columns under compressive load were performed and are presented in this paper. The hybrid welded T-section stub columns comprise high strength steel Q690 flange and normal strength steel Q355 web. Material property studies were implemented through tensile coupon tests. Residual stress in membrane type was measured and recorded and its impact on structural performance was also assessed. Initial local geometric imperfection measurements were conducted for all the specimens. In conjunction with experimental studies, numerical investigation was performed to generate more test specimens extending the range of cross-section dimensions by which test data pool can be supplemented. The Eurocode of EN 1993-1-1, EN 1993-1-5 and EN 1993-1-12, the North American code of ANSI/AISC 360-16 and the Australian code of AS 4100 together with design approaches of Direct Strength Method and Continuous Strength Method were examined for its applicability for cross-section classification and compression resistance predictions of hybrid T-sections. Overall, the current specified limits were applicable for hybrid welded T-section and strength predictions from design codes were comparatively consistent and reliable. Strength predictions from Direct Strength Method and Continuous Strength Method were relatively appropriate though overly conservative predictions were provided for cross-section with large slenderness. In this study, modifications on the Direct Strength Method and Continuous Strength Method are proposed, which is shown to provide accurate predictions at cross-sectional level in a reliable manner. [ABSTRACT FROM AUTHOR]

• Excellent bending capacity and material utilization can be achieved in the novel hollow steel-UHPC composite deck. • The effects of the embedded steel tubes, steel bars, UHPC material, and flange thickness on the mechanical properties of hollow steel-UHPC composite decks are discussed. • There is a great composite effect between the embedded steel pipe and the UHPC without any additional shear connection. • A theoretical formula is proposed to predict the flexural capacity of the hollow steel-UHPC composite deck. The application of UHPC might reduce the weight of the bridge deck and improve its crack resistance and durability. This study proposes a hollow steel-UHPC composite deck composed of the hollow steel tube and UHPC without shear connectors. The flexural test was performed on the hollow steel-UHPC composite deck to evaluate the effects of the embedded steel tubes, steel bars, UHPC material, and flange thickness. In addition, the mechanical properties of hollow steel-UHPC composite decks were compared with waffle decks and solid concrete decks. Results indicated that the hollow steel-UHPC composite deck had excellent bending capacity and material utilization. The load-deflection curve of the composite decks could be divided into four stages: elastic stage, working stage with cracks, nonlinear stage, and fully plastic stage. Without any additional shear connection, the steel-UHPC interface slip did not occur until the load reached 0.89 P u. In the ultimate limit state, the strains at the mid-span cross-section of steel and UHPC were almost the same, suggesting that there was a good composite effect between the embedded steel tube and the outer UHPC. The embedded steel tube had a significant influence on improving the original stiffness (K 0), the stiffness at the working stage with cracks (K 1), and the flexural capacity (P u) of composite decks. The flexural failure of the hollow steel-UHPC composite deck was controlled by the tensile zone. Finally, a theoretical formula was proposed to predict the flexural capacity of the hollow steel-UHPC composite deck. [ABSTRACT FROM AUTHOR]

In unreinforced masonry buildings, load bearing walls are not of only rectangular shape in the plan, but the cross walls connected to them make the walls of either I shape, T shape, C shape, etc. The presence of the cross walls can significantly change the behavior of the masonry walls in terms of strength and the failure modes of the walls. In this paper, a parametric study has been performed to investigate the effect of different parameters, namely pre-compressions, material properties, aspect ratios, and boundary conditions on the in-plane behavior of the masonry walls. The masonry walls have been modeled using the simplified micro-modeling approach in the standard finite element software Abaqus without any user-defined subroutine. It has been found that the strength and damage pattern of the flanged walls are different from the rectangular walls, which needs to be considered in the analysis of masonry walls using a numerical approach or while conducting experiments. • The effect of flanges on the in-plane behavior of the masonry walls using the FEM. • Effect of various aspect ratios and pre-compressions on the behavior of the URM walls. • Effect of various material properties and boundary conditions on the behavior of the URM walls. • The crucial difference between the behavior of the rectangular and the flanged walls. [ABSTRACT FROM AUTHOR]

• Unplanned chases made for the passage of pipes compromise the structural security. • Disregarding the chase thickness to determine slenderness wall is inadequate. • Disregarding the chase thickness to determine strength reduction factor is inadequate. • Strength prediction for walls is established using the chase thickness percentage. • Strength prediction for walls with flanges and chases considers height/length ratios. Unplanned chases made in structural masonry for the passage of pipes can compromise the overall strength of the structure. This interference does not have clearly established and uniform criteria in Brazilian and international standards for assessing the deformability and consequent safety reduction of the walls. The present study evaluates numerically, by using the Finite Element Method (FEM) and fitting procedures, the effect of chases in masonry walls elements, proposing a method to preview walls strength reductions with the presence of chases. Thus, an additional criterion for the reduction factor (R) due to the masonry slenderness is presented. The contribution of the flanges is also evaluated for different height/length ratios. The simplified approach of disregarding the chase thickness of the wall determine its slenderness (λ), and consequently the strength reduction factor (R), was invalidated in the present study, considering that the numerical models provided lower reduction coefficients for any wall group studied. The slenderness of the walls considering the residual wall thickness in the chase region must be limited to 33. [ABSTRACT FROM AUTHOR]

Tubular steel towers are the most commonly used structures to support wind converters. Towers are fabricated in welded segments, complying with the traffic requirements for transportation, and in-situ assembled. Ring flange connections are used to connect two segments. Fatigue endurance of the ring flange to the shell weld, class 71, is often the design criterion and imposes a limit on the shell thickness. Recently studied friction connections with long opened slotted holes, in HISTWIN and HISTWIN2 projects, provides a remedy for this limitation. The main purpose of this paper is to compare performance of the ring flange connection and the novel friction considering connection of a real tubular tower segment 3.37 m in diameter and 24 mm shell thickness. This cross-section is designed for the ultimate load M Ed = 45.8 MNm and the steel grade S355. Finite Element Method is used to investigate possible failure modes of the connection. Advanced FEA comprise the realistic geometry of the connection, ductile damage material model and element removal using explicit dynamic solver. This allows sophisticated analysis of the behaviour and direct comparison of the results for both connection alternatives. The FEA is validated by down-scaled experiments performed previously within the HISTWIN project. The friction connection is thoroughly examined: geometry of the connection, influence of the shell imperfection in the vicinity of the connection and possible use of higher resistance steel grades. By focusing on key issues of the friction connection recommendations for the design are provided together with a numerical example. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bending tests on the timber-concrete composite beams with wide slab. • Shear lag effect of timber-concrete composite beams. • Effective flange width of timber-concrete composite beams. To support the design and application of timber-concrete composite (TCC) floor systems, the effective width of the TCC beams with crossed inclined coach screw connections at the serviceability state was evaluated in this study. The bending tests on the TCC beams with different slab widths were conducted to assess the shear lag effect in concrete slab and discuss the influence of slab width on the bending performance of TCC beams. A nonlinear finite element (FE) model for TCC beams was established in ABAQUS 6.14 and validated by the experimental results. Based on the experimental and FE studies, an extensive parametrical analysis was performed to evaluate the effect of various factors on the effective width of TCC beams. The presence of shear lag effect was proved by the experimental strain distributions in the concrete slab, and the shear lag effect was found more apparent for the tension strain at the bottom of concrete slab than the compression strain at the upper surface of slab. The FE numerical results showed high agreement with the test results in terms of the macro and micro bending performances of the TCC beams. In addition, the parametrical studies indicated that the effective width of TCC beams mainly depends on the load type, slab width-to-span ratio, slab thickness, and connection stiffness. Finally, for practical use, a general formula was proposed to calculate the effective width of the TCC beams. [ABSTRACT FROM AUTHOR]

• A stiffened bolted-flange column splice joints with connecting plates and rebar hooks of CFST. • Four full-scale specimens were analyzed via cyclic test and finite element analysis. • Hysteretic behavior, performance indicator and ductility of the joint were analyzed. • The influences of connecting plate or rebar hook parameters was conducted by FEA. • Formulas for the yield moments of the stiffened joints were proposed and verified. A stiffened bolted flange splice joint configuration with connecting plates and rebar hooks for concrete-filled steel tubular columns is proposed for high-rise prefabricated steel structures. Four full-scale specimens with different flange thickness or different stiffener layouts were tested under cyclic loads, and the hysteretic behaviors, performance indicators, ductility and stiffness were analyzed. Compared with conventional joints, the bolted flange splice joints with connecting plates and rebar hooks show higher yield moments and stiffness. Finite element models that were verified by test results were established and adopted to further analyze the seismic performance of these proposed joints. The rotation capacity and stress distribution were analyzed, and the stiffened joints with connecting plates and rebar hooks could be regarded as rigid for high-rise structures based on the stiffness. Parametric analysis was conducted to analyze the influences of connecting plate or rebar hook parameters, proposing design recommendations accordingly. Formulas of the yield moments for these stiffened joints were proposed, and the calculated results have good agreements with that of tests and the FE analysis, indicating that the formulas could be used in the practical design. [ABSTRACT FROM AUTHOR]

In order to investigate seismic behavior of bolted extended end-plate connections, a phenomenological component-based model with several separated springs is presented where the constitutive relationships for individual components are determined using material and geometric properties. Analytical results using the developed model were compared with experimental data from full-scale moment connection tests including global load versus displacement and local response of beam hinge, panel zone and other components. The effectiveness of the model was demonstrated by these comparisons. The model is then leveraged to study the influence of design decisions such as weak columns and bolt pretension. The analytical results indicate that bolt pretension and related connection slip can significantly affect the seismic behavior of the end-plate and column flange and thus their inclusion in the proposed model is validated. [ABSTRACT FROM AUTHOR]