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The paper conducted 19 partially and 5 fully loaded tests on round-ended concrete-filled steel tubular (CFST) columns. These tests revealed that the ultimate strengths of round-ended CFST columns under partial load declined as the cross-sectional aspect ratio or partial compression area ratio increased. However, the use of a top plate effectively enhanced their ultimate strengths. In addition, a finite element model (FEM) was utilized to generate 487 large-size models to explore the confinement effect, stress distribution, and parametric effects. Since there are no specific design standards available for round-ended CFST columns, the paper has evaluated the applicability of design methods provided in Eurocode 4, AISC 360–16, and Chinese code GB50396 which are intended for circular, square, or elliptical CFST columns for round-ended CFST columns under partial load. However, these existing design techniques showed inaccurate and dispersed resistance predictions for round-ended CFST columns. Therefore, an effective simplified method for forecasting the resistance predictions of round-ended CFST columns under the partial load has been proposed based on the testing results and FEM analysis. • For the first time, partial compression tests of 19 round-ended CFST columns were conducted. • The top endplate can be used to effectively enhance its partial compression resistance. • As the cross-sectional aspect ratio increase, the load-carrying capacity falls. • Exiting design methods are not applicable to partially loaded round-ended CFST columns. • For the first time, a simplified model for their partial compression resistance was proposed. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tube (CFST) columns are widely used in structures where high bearing capacity and ductility are crucial. They offer several advantages over conventional steel or concrete columns, such as a high strength-weight ratio, better ductility, and increased resistance to buckling and compression. Also, seismic damage in CFST columns primarily occurs within the plastic hinge region at their base. Therefore, by improving the ductility specifically in this plastic hinge region, the seismic resilience of CFST columns can be significantly enhanced. In this paper, the use of steel-polypropylene hybrid fiber engineered cementitious composites (HECC) in the plastic hinge region of square CFST columns is proposed to improve their hysteretic performance. This paper presents an experimental study of the hysteretic behavior with three different local HECC-enhanced CFST (LHECFST) columns. Based on the test results, modeling was performed using ABAQUS, and the reliability of the FE model was verified. Following this, FE models with smaller HECC pouring height gradients were developed, and these CFST columns were parametrically analyzed. The results show that the seismic performance of CFST columns is improved by local enhancement with HECC. The pouring of HECC will reduce the slope of the peak load descending stage of the CFST column. In addition, the formulas for calculating the peak load of LHECFST columns with different axial compression ratios and HECC pouring heights were developed and the accuracy was verified by contrasting the data. • Hysteresis tests on concrete-filled steel tube (CFST) columns were performed. • The validation data were established by finite element analysis. • Engineered cementitious composites (ECC) reduce damage in plastic hinge region. • The deterioration of peak loads in CFST columns with ECC localized pouring is slow. • Methods are proposed for calculating the peak load of two-material CFST columns. [ABSTRACT FROM AUTHOR]

Assembled joints are widely recognized and applied because they are green and perfectly fit the current development trend of the construction industry. This paper proposes a composite wall-steel beam joint with crossed U-plate connection. In order to study the influence of the seismic performance of the joint, 2 experimental specimens and 13 finite element models are designed. The thickness of the U-plate, the strength of the steel of the U-plate, and the overlap length with the steel beam are changed so that the low circumferential reciprocating loading test and numerical analysis of the finite element are carried out to determine the main indexes of the seismic performances, such as hysteresis curves, skeleton curves, ductility, energy dissipation capacity, and stiffness degradation. The results show that the wall-beam joints connected with U-plate have satisfactory seismic performance. With the improvement of U-plate thickness and steel strength, the ultimate bearing capacity and ultimate displacement of the joint increase significantly, and the increase of lap length with steel connecting beams improves the ductility performance of the joint. Moreover, M U / M B ≥ 1.41 at the node domain during design can get excellent bearing capacity; the corner at the bending of the U-plate is a weak part, and it is recommended to reduce or eliminate the residual stress in the area in practice. • An experimental investigation and numerical simulations of the combined wall-steel beam joint with cross U-plate connection is presented in this paper. • The combined wall-steel beam joint with cross U-plate connection had different thickness of U-plate, steel strength of plates and lap length with steel beam, including a total of 2 experimental specimens and 13 simulation specimens. • The deformed shapes of the combined wall-steel beam joint with cross U-plate connection and the effects of different parameters on seismic performance have been observed in the tests and discussed in this paper. • Finally, comparing the test and numerical simulation results, and expanding the analysis of the effect of different parameters on the seismic performance, the problems that should be paid attention to when designing are proposed, and the recommendations on the strength and stiffness of the combined wall-steel beam joint with cross U-plate connection are given. [ABSTRACT FROM AUTHOR]

The compressive behavior of steel tube reinforced concrete (STRC) columns under eccentric loads was investigated experimentally and numerically in this paper. Primary parameters included the eccentricity ratio, the concrete-filled steel tube (CFST) area ratio, and the longitudinal rebar ratio. This paper analyzed the impacts of these parameters as well as the failure modes, the full-range compression process, and the strain development. Similar to the reinforced concrete (RC) column, the full-range compression process of STRC column under eccentric loads can be divided into three stages, i.e., elastic stage, elastic-plastic stage (cracking stage), and plastic stage (descent stage). The experimental findings showed that, on the near-load side of the STRC column, the outer concrete crushed, and the longitudinal rebars buckled in compression. Conversely, on the far-load side, the concrete exhibited cracking in tension, and the longitudinal rebars exhibited tension. Finite element (FE) analysis results demonstrated that, similar to a RC column, three distinct failure mechanisms can be identified for STRC columns under eccentric loads, i.e., compression-controlled, balanced, and tension-controlled failures. During the compression process, analyses were conducted on the contact stress between the steel tube and concrete, as well as on the load distribution between the inner CFST and the outer RC. The ultimate load of the STRC column decreased with an increase in the eccentricity ratio, while it increased with larger longitudinal rebar ratio and CFST area ratio. Based on the experimental and FE analysis results, a simplified calculation method was developed to determine the eccentricity reduction coefficient for STRC columns. • The eccentric test result of steel tube reinforced concrete (STRC) column with low CFST area ratio was presented. • The effect of eccentricity ratio, CFST area ratio and rebar ratio on the compressive behavior of STRC column were analyzed. • The failure mechanisms, load distribution and contact stress was analyzed by refined finite element analysis. • The simplified calculation method of eccentricity reduction coefficient was proposed for the ultimate load of STRC column. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental investigation of vertically-placed stiffened corrugated steel walls (VSCSWs). Quasi-static cyclic tests were conducted on three half-scale, one-story, single-bay steel shear walls with unstiffened corrugated plate, and stiffened corrugated plates with one or two pairs of horizontal stiffeners. Based on test observations, this paper elucidated the failure modes of diverse specimens and conducted a comparative analysis of their hysteresis performance. Then, the finite element models of the specimens were constructed, and their accuracy was validated using the test results. Subsequently, a series of parametric analyses were conducted to further investigate the effect of several important geometric parameters on the hysteretic behavior of VSCSWs. Both experimental and numerical results show that adding horizontal stiffeners to vertically-placed corrugated steel plate shear walls is an effective way to improve their lateral load-bearing capacity and energy dissipation performance. • Quasi-static cyclic tests were conducted on three half-scale specimens to investigate the seismic performance of VSCSWs. • The failure modes of VSCSWs were revealed based on the test observations. • The hysteretic performance of the steel shear walls with various type of steel plates was compared. • Finite element models of the specimens were developed, and parametric analyses were further conducted. [ABSTRACT FROM AUTHOR]

Bridge structures are often vulnerable to vehicle collisions, necessitating innovative solutions to enhance safety. This paper introduces a concept employing energy-absorbing crash dampers to safeguard bridge structures. The primary objective is to optimize energy dissipation while ensuring uninterrupted bridge functionality. Utilizing the finite element modeling approach, and incorporating realistic constitutive relationships and boundary conditions, simulations were performed to encompass X-shaped damper impact tests and collisions involving trucks with steel-reinforced concrete columns. The study affirms the effectiveness of the numerical model in simulating the dynamic response of steel dampers and column structures under vehicle impacts. Leveraging this modeling approach, this research compares the anti-collision performance of urban bridge structures, both with and without the proposed bridge pier. The methodology involves two key steps: first, a response surface optimization analysis is conducted for the primary energy-absorbing component, the anti-collision hollow diamond-shaped damper, determining optimal dimensions for the device at varying vehicle collision speeds. Second, a comparative study explores failure modes, collision capabilities, deflection changes, and energy absorption of bridge structures with and without the energy-absorbing crash dampers under vehicle impacts. Subsequently, this study performs an optimization design and calculation for the bridge structures. The outcomes reveal that the bridge with the pier experiences a substantial reduction in impact peak force. The damper effectively absorbs part of impact energy, with the optimized damper demonstrating superior energy absorption. • This paper presents for the first employing energy-absorbing crash dampers to safeguard bridge structures against impact. • The optimal dimensions of anti-collision hollow diamond-shaped damper is determined at varying vehicle collision speeds. • The dynamic responses of bridge structure with energy-absorbing crash dampers under lateral impact were obtained and analyzed. [ABSTRACT FROM AUTHOR]

This research paper presents a comprehensive numerical-experimental analysis of the phenomena observed during the compression of small energy absorbers (EAs) with dimensions 23 × 23 mm and a thickness of 0.6 mm. This study uses the direct impact Hopkinson (DIH) method. The locus is the detailed prediction of the strength of laser-welded joints in terms of energy absorption under both quasi-static and dynamic loading conditions. Furthermore, the paper explores the potential utility of the described methodology for modeling and predicting the failure mechanisms of small energy absorbers. This investigation delves into key factors that affect the distribution of cracks in deformed energy absorbers. These include: the detail of the reproduction of the absorber geometry, the impact of finite element formulations and modeling method (2D/3D elements) and the complexity of the material model for propagated cracks. Two material models are considered, the simplified Johnson–Cook model and the tabulated Johnson-Cook with Hockett–Shelby extrapolation model, which incorporate linear damage dependent on the stress triaxiality and Lode angle. The study also highlights the advantages and disadvantages of the DIH test method. Some features cannot be effectively observed through experimental testing alone. The experimental procedure involved initial testing and calibration of the material models for both the parent material and the welded joints at three different strain rates. Subsequently, the validated energy absorber models are subjected to static and dynamic crushing. The results are subsequently compared with the virtual results obtained using the gravity hammer method, which is a more readily accessible testing approach. Remarkably, a very high correlation between the numerical simulation and experimental data is observed, providing a comprehensive understanding of the research problem related to laser-welded absorbers. [Display omitted] • A simple constitutive model cannot predict cracking in thin-walled energy absorbers • The fully optimized material model reliably reproduces the HSS failure in a complex state of stress • The strength and ductility increase with a strain rate >1000 s−1 compared to static conditions. • The reduced number of cracks on the folds is observed in the dynamic crushing of energy absorbers. • The sensitivity of the strain rate of material is secondary to the increase of energy absorbed in dynamic crushing. [ABSTRACT FROM AUTHOR]

This paper investigates concrete-filled dual steel stiffened tubular (CFDSST) slender columns with a cold-formed stiffened outer tube, a square inner tube and concrete infill between the two steel sections and also inside the inner section. To the best of the authors' knowledge, the behaviour of these types of slender column has not previously been studied, although the behaviour of short columns has been previously explored. Accordingly, the details and development of a finite element model are presented, as well as the validation against available test data. The model is employed to conduct an extensive parametric study to examine the behaviour of CFDSST slender columns with different geometric and material properties. Based on an analysis of the strain distributions in the cross-section, a method for defining intermediate-length and long columns is proposed. It is shown that the slenderness ratio is a very important parameter in the behaviour of CFDSST columns, affecting both the capacity and the failure mode. Other important variables for intermediate-length columns are shown to be the yield strength of the outer steel tube, the strength of the sandwiched concrete and the width-to-thickness ratio of the outer tube whilst only former of these is shown to be very influential for long columns. The ultimate strengths are compared with a number of different design methods, which were suitably adapted for the section types, owing a lack of specific guidance currently available. Based on the results it was recommended that the AS/NZS 2327 design standard provides the most accurate reflection of the real behaviour for CFDSST slender columns. • This paper presents, for the first time, analysis on the behaviour of square concrete-filled dual steel-stiffened tubular slender columns. • These members are shown to behave in a efficient manner in terms of the material usage requirements. • The stiffeners improve the overall buckling response compared with members without these elements. • An advanced FE model is presented, and validated, and then used to develop a thorough understanding of the behaviour. • Detailed design guidance is also provided. [ABSTRACT FROM AUTHOR]

Blind bolting technology could access the inside of a closed-section column, which enables to assemble a steel beam to concrete encased CFST (CECFST) column. However, the bulge of steel tube and outer concrete were likely to appear for blind bolted normal CECFST column joints owing to the limited strength of outer concrete. Therefore, this paper adopts UHPC as outer concrete to form a UHPC encased CFST composite column, which aims to avoid the steel tube from being failed for blind bolted joints effectively. Initially, the modular construction process of UHPC encased CFST column blind bolted joints was proposed, in which the assembled joints could be divided into column and beam modular parts during construction. Afterwards, a finite element model was established by ABAQUS considering the complex interactions and material properties to validate the feasible of this modular joint. Detailed failure mechanism and contact behavior between UHPC and steel tube of the joints were discussed, indicating that the UHPC could effectively restrict the bulge of steel tube. Parametric analyses were conducted on typical UHPC encased CFST composite column blind bolted to steel beam joint. Finally, the analytical models of the joint initial stiffness and moment resistance were developed based on the component method considering the dispersal effect of outer UHPC. The comparison results declared that the proposed analytical method provided a reasonable prediction of the initial stiffness and moment resistance. The research results in this paper validated that replacing normal concrete of CECFST by UHPC could avoid column failure when using blind bolted joints and gave a proper design method for the UHPC encased CFST composite column blind bolted to steel beam joint. • Confinement between UHPC and steel tube was analyzed in assembled joints. • Failure mechanism and influence of parameters on the novel joint was discussed. • Design model on initial stiffness and moment resistance was developed. [ABSTRACT FROM AUTHOR]

This study investigates the structural performance of the corner column-to-column connection made of VectorBloc under tensile axial load, which links corner columns between two consecutive floors. Nine full-scale specimens, comprising three distinct connection types one Axial Tension Single Column (ATSC) connection and two Axial Tension Bundle Columns (ATBC-MCC and ATBC-BCC) connections were tested under axial tension load. Failure in all specimens resulted from the rupture of Socket-Head-Cap Screws (SHCSs) connecting the upper and lower blocs of the connector. Despite identical SHCSs across all specimens, variations in their positions led to different outcomes due to differing column geometries and resulting load eccentricities. Notably, the eccentricity induced bloc rotation, leading to separation on the tension face. Axial tension single column exhibited the lowest average tensile capacity, while bundle column connections, despite similar section areas, exhibited contrasting load capacities, attributed to varying load eccentricities. A subsequent parametric study, using finite element analysis, was conducted to identify parameters critical for maximizing the tensile load capacity of this column connection. • This paper presents the performance of Vectorbloc connection subjected to axial tension. • This research was completed using full-scale tests and a detailed FE-based parametric study. • The SHCSs play the most important role in the tensile capacity of the connection. • Both eccentricity and parameter d must be minimized to maximise the tensile capacity. • The parameter d is developed and introduced for the first time in this paper. [ABSTRACT FROM AUTHOR]

This paper investigates the shortcomings of the AISC 360–22 and Eurocode 3–22 provisions for calculating the plateau and lateral-torsional buckling (LTB) flexural resistance of thin-web singly-symmetric steel I-section members with the larger flange in compression. In addition, the paper proposes and evaluates corresponding newly recommended AISC 360 procedures, which eliminate the tension flange yielding (TFY) limit state check and implement a more mechanistically-based solution accounting for the inelastic reserve strength associated with flexural yielding in tension. The recommended procedures incorporate other recently proposed improvements to AISC 360, solving substantive LTB overprediction problems for certain types of built-up I-section members. The results from six large-scale experimental tests, associated finite element analysis (FEA) simulations, and parametric FEA simulation studies are considered. The results demonstrate improved accuracy and substantial gains in the predicted strengths by the recommended procedures relative to the AISC 360–22 and Eurocode 3–22 calculations for a significant range of geometries and loadings. In addition, the recommended methods address LTB overprediction problems exhibited by AISC 360–22 for a limited range of the member types studied. • Experimental evidence shows current flexure design codes can be overly conservative. • Accounting for tensile yield in flexure can result in substantial strength gains. • Codes do not calculate the true stain distribution for larger flanges in compression. • Experimental evidence shows current flexure design codes can overpredict capacity. • Improvements can be made to the design codes through simple modification. [ABSTRACT FROM AUTHOR]

The paper investigates the shear mechanic performance of transformed triangular corrugated steel plates (TT-CSPs) with top stringers applied in the trestle, incorporating a comprehensive analysis of how plate dimensions and corrugation density affect both elastic and inelastic buckling capacities. By proposing and validating formulas for the ultimate shear-bearing capacity through finite element analysis (FEA), this paper advances a capacity prediction approach that accounts for the finite rigidity of top stringers by introducing a reduction factor. The results reveal that corrugation density significantly impacts both elastic buckling load and ultimate strength, with plate width playing a more crucial role than height in determining capacity. Furthermore, the inclusion of top-stringer flexural rigidity is shown to notably enhance the shear-bearing capacity of TT-CSPs, providing a vital consideration for their strength design. [Display omitted] • Proposed formula for global elastic shear buckling load of transformed triangular corrugated steel plates (TT-CSP) • Proposed a comprehensive design method to predict shear-bearing capacity of TT-CSPs, considering top stringer constraints • Study the impact of corrugated plate and corrugation dimensions on elastic and inelastic buckling capacity of TT-CSPs • Reveal the contribution of top stringers to shear resistance of built-up TT-CSPs [ABSTRACT FROM AUTHOR]

This paper presents an analytical formula for the second-order normal stresses in flanges of the imperfect I beam-columns with sinusoidal web corrugation. To deduce the analytical expression, the beam is separated into three parts. The flanges are modelled as thin-walled beam-columns and the corrugated web is modelled as a thin equivalent orthotropic plate with uniform thickness. The indispensable elastic critical loads are derived from the total potential strain energy of the imperfect beam-column using an energy method. To assess the accuracy of the proposed analytical formula, full shell finite element models were created in Abaqus software. The result of the benchmark example showed that the derived expression is accurate and applicable for geometrically nonlinear analysis of beam-columns with sinusoidal web corrugation. Based on the proposed analytical expression, the Ayrton-Perry type solutions for corrugated web columns and beams are also presented in this paper. • The proposed analytical expression has a strong mechanical background. • It is applicable for GNIA of imperfect beam-columns with sinusoidal web corrugation. • The Ayrton-Perry type solutions for columns and beams are derived. • The accuracy of the EC3-based imperfection factors is examined. [ABSTRACT FROM AUTHOR]

As a new type of connection methodology, hybrid-bonded/bolted (HBB) connections exhibit potential advantages over mechanical or pure adhesive connections in construction, aerospace, shipbuilding, machinery, and other fields. The key to designing HBB joints is reasonable load sharing between bolts and adhesive layers. An accurate analytical model could effectively and quickly help engineers perform design iterations and arrive at reasonable load-sharing predictions. The existing models usually consider HBB joints as a simple superposition of adhesive and bolted joints. This paper found through experiments that when the HBB joint is subjected to tension, the bolt hole undergoes a certain deformation, resulting in a different bolt-hole contact state than pure bolt joints. Therefore, in the HBB joint, the load transferred by the bolt calculated using the existing model is usually higher than the actual situation. In response to this situation, this paper proposes a new calculation approach for bolt shear stiffness for this particular deformation and develops an analytical model for HBB joints. By comparing with the finite element method (FEM) results, it has been proven that this model can accurately calculate the load-displacement curves of HBB joints of different materials and sizes, as well as the load distribution between bolts and adhesive layers. This provides favorable references for the design of HBB joints. • HBB joints exhibit significant hole deformation under tension, which leads to the special component's contact mode; • The special contact mode leads to the lower load-sharing of bolts in HBB joints; • The new model was derived to account for the effect of the hole deformation; [ABSTRACT FROM AUTHOR]

This paper conducts a comparative study of the tensile performance of plug-pin scaffold joints under different temperatures. The current research objects are mostly for the traditional low carbon steel scaffolding, and lack of research on the tensile performance of scaffolding joints in low temperature conditions. In this paper, based on the temporary seating facilities of the Beijing Winter Olympic Games complex, a new type of sorbite stainless steel was used. The tensile bearing capacity, damage mode and strain distribution patterns of the sorbite stainless steel joints and traditional Q355 joints under different temperature conditions were studied with finite element model and parametric analysis. The results indicated that for traditional Q355 joints, damage primarily occurs in the form of wedge bending deformation, and that decreasing temperature leads to increased tensile bearing and yield capacity. In contrast, for sorbite stainless steel joints, higher tensile bearing capacity was observed at +20 °C, but at −20 °C and − 40 °C conditions, the bend of the C-type card becomes more prone to crack. The accuracy of the ABAQUS finite element model is verified by comparing it with test results. Increasing the thickness of the U-type and C-type cards can slightly increase the tensile bearing capacity of the joint and a minimum wall thickness of 2.7 mm is recommended. Two suggestions are proposed for improving the joint design using sorbite stainless steel. The research provides a premise for further studies on the tensile performance of plug-pin scaffold joints. • A low-temperature loading test device and method for joints are proposed. It offers a test environment of −70 °C ∼ 150 °C. • The material properties of sorbite stainless steel and Q355 at −40 °C, −20 °C and room temperature are studied. • The mechanical properties of plug-pin scaffold joints using sorbite stainless steel and Q355 at low temperatures are studied. • The tensile properties of plug-pin scaffold joints at different low temperatures are investigated. • Theoretical load-displacement modeling of plug-pin scaffold joints is developed. [ABSTRACT FROM AUTHOR]

To enhance the compressive performance of steel plate shear walls, this paper proposed a new type internally stiffened double steel plate shear wall (ISD-SPSW), incorporating two outer steel plates, a number of stiffening ribs and edge members on both sides to form a closed cross-section, which significantly improves the compressive and lateral stiffness of the double steel plate shear wall. To investigate the deformation and failure modes of ISD-SPSW under vertical axial compressive loads, seven specimens were designed and fabricated in this paper, and axial compression experiments were carried out. The effects of the loading regime, number of web stiffening ribs, thickness of outer steel plates, width of edge members, and height of the wall on the compressive performance of shear walls were examined. The load-equivalent vertical strain curves, strain curves, displacement ductility coefficients, and other axial-pressure performance indices of the ISD-SPSW were obtained. The results indicated that the failure modes of ISD-SPSW under axial compressive loads primarily involve strength failure and overall bending instability. Increasing the number of stiffening ribs or the thickness of outer steel plates significantly enhances the compressive load-bearing capacity and ductility of the ISD-SPSW. When the specimen has a larger height to thickness ratio of the specimen, it is prone to overall bending instability failure, leading to lower ductility and load-bearing capacity. • Propose a double-steel plate shear wall using flat steel plate internal stiffening. • Damage under axial pressure is overall instability accompanying local buckling. • Stiffening rib can improve the steel plate's local & specimen's overall stability. • Height and thickness of specimen are important factor in compressive performance. • The finite element model is in good agreement with the test. [ABSTRACT FROM AUTHOR]

Slender webs in welded steel plate I-girders (often used for long spans or load transfer in bridges and buildings) develop initial out-of-flatness imperfections as a result of fabrication (e.g., rolling, forming, welding, and assembly). Previous research has suggested that these imperfections can reduce the shear strength of the web; therefore, various specifications since the 1960s have included out-of-flatness imperfection tolerance limits for webs in steel plate girders. The research presented in this paper (1) provides a comprehensive review of current web out-of-flatness tolerance limits and measurement approaches, (2) introduces an alternative measurement technique for the out-of-flatness of webs (which collects a wide array of equispaced measurements), and (3) presents field measurements of 23 web panels (bounded by transverse stiffeners) across 12 different girders (with depths ranging from 0.914 to 2.08 m) that were commercially fabricated for bridge applications. The peak value for the out-of-flatness of the web, averaged across all measurements for each panel, was d / 170 (where d represents the least panel dimension). However, the location of peak out-of-flatness is seldom at the middle of the panel and has a 'dimpled' shape, meaning that the peak out-of-plane bulge covers only a small portion of the panel. The measurements demonstrated in this paper provide significantly more data resolution, thus enabling a better evaluation of the true impact of realistically irregular imperfection shapes and magnitudes on the shear strength of the plate. Such an evaluation based on the measurements presented in this paper is documented in a companion paper and is performed via numerical finite element analysis. [Display omitted] • Extensive field measurements to capture the initial web out-of-flatness imperfection magnitude and shape of plate girders were conducted. • A comprehensive review of current and past web out-of-flatness tolerance limits and measurement approaches were investigated. • A new measurement technique is introduced as an alternative to improve the accuracy, repeatability, and efficiency of field measurements. • Overall, the post-fabrication magnitudes of the out-of-flatness imperfections in the web do not exceed tolerance limits prescribed by code-based specifications, the location of the peak value of the out-of-flatness in the web has dimpled shapes and is seldom at the center of the web panel. [ABSTRACT FROM AUTHOR]

In recent years, there has been a notable increase in the utilization of multi-celled corrugated-plate CFST (MC-CFST) walls. In this paper, a connection joint between a steel beam and an MC-CFST wall was proposed. The joint consisted of MC-CFST walls, end columns, horizontal diaphragms, vertical plates, and steel beams, with each steel component being interconnected through welding. To investigate its mechanical properties, a refined finite element model was developed, and the accuracy of the modeling method was validated through existing test results. The stiffness and moment capacity of the joints were analyzed, focusing on the effects of various factors, including the insertion depth of the horizontal diaphragm, beam-to-column linear stiffness ratio, width-to-thickness ratio of the end column plate, diameter of the horizontal diaphragm opening, axial compression ratio, and concrete and steel strengths. Based on numerical and theoretical analyses, a calculation method for determining the moment capacity of the joint and establishing the lower limit value for the steel tube thickness of the end columns was proposed by using the yield line analysis. The predicted value of the moment capacity of the joint was found to deviate from the finite element result by no more than 10%, suggesting that the formula exhibited excellent accuracy and applicability. The minimum steel tube thickness of the end columns was determined by considering the yield of the beam flange section. The design method presented in this paper has the potential to offer a valuable reference for practical designs of the proposed connection joint. • A novel connection joint between a steel beam and a multi-celled corrugated-plate CFST wall was proposed. • A validated FE model was established for further investigation. • A parametric analysis was conducted to investigate the influence on the stiffness of the joints. • The effect of various parameters on the moment capacity of the joints was discussed. • Based on numerical and theoretical analyses, a formula for determining the moment capacity of the joint was proposed. [ABSTRACT FROM AUTHOR]

Stainless steel exhibits strain hardening characteristics under cyclic loading, hence presenting significant potential for application in seismic design. However, the current stainless steel structural design code fails to account for this beneficial effect in the cross-section classification. Given the scarcity of research about the behavior of structural stainless steel members under cyclic stress, this paper establishes the preliminary finite element model for the austenitic stainless steel (EN 1.4301) H-section. Firstly, finite element model validation of the existing cyclic tests on stainless steel members from literature was performed, followed by numerical analyses of a total of 370 beam and beam-columns members with different axial compression ratios and plate width-thickness ratios, and subsequently evaluated the cross-section classifications specified in prEN 1993-1-4, AISC 370 and CECS 410 through extensive parametric studies. The results indicate that the current design codes are conservative in the provisions for cross-section classification because they neglect the influence of plate interactions and material strengthening effects during cyclic loading. In this paper, limit and generalized expressions for austenitic stainless steel H-section with different axial compression ratios and cross-section classes under cyclic loading about major-axis are proposed. Additionally, the effect of material strengthening on cross-section classification under cyclic loading is examined. • Classification criteria for austenitic stainless steel H-section under cyclic loading about major-axis are studies. • Cross-section classification criteria according to EC3, AISC 370 and CECS 410 design codes are evaluated. • A new cross-section classification criterion for H-section under cyclic loading is proposed. • Effect of material strain hardening on cross-section classification under cyclic loading is discussed. [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]

The Elliptical-head one-side bolt (EOB) is a typical representative of the third generation for one-side bolts, relying on its elliptical head and bolt hole to achieve orthogonal anchorage, and the application scenario is mainly the bolted connection of closed-section members. Studies have been reported for the shear performance of EOBs bolted lap connections and the tensile behaviour of concrete-filled steel tubes, but there is still a lack of the tensile performance of EOBs connecting Hollow section columns (HSCs), which is necessary for the application of the component method for the beam-column joints design. Therefore, numerical simulation and theoretical analysis methods were employed in this paper to demonstrate the feasibility of adopting EOBs for this type of connection, including typical failure modes, novel yield line pattern in the HSC wall, comparison with the Conventional high-strength bolt (CHB) connections, analysis of the parameters related to the elliptical bolt head and hole, and the establishment and validation of the methodology for calculating the HSC bearing capacity. The results show that: The novel trapezoidal yield line pattern tended to show in the HSC wall with the smaller bolt pitch distance and larger gauge distance; The yield strength of the EOBs bolted T-stub to HSC connections was reduced by about 15% compared to the CHBs bolted ones; Vertical layout of bolt holes, accuracy of rough assembly, rotation deviation of bolt shank within 20° and avoidance of bolt offsets in bolt hole were recommended for EOB connections; The novel yield line pattern established in this paper predicted the yield strength of the connections, and the accuracy and stability were verified by comparing with finite element modelling (FEM) results. • Tensile performance of EOBs connecting HSC was carried out. • Trapezoidal yield line pattern was found in HSC connecting wall. • Strength of EOBs bolted connections was reduced by 15% compared to CHBs bolted ones. • Equations for predicting the strength of EOBs bolted connections were established. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical investigation into the behaviour of cold-formed concrete-filled dual steel-stiffened tubular (CFDSST) short columns under axial compressive load. This new composite column is fabricated from four cold-formed lipped angles to make the outer steel tube and a concentrically-placed steel tube located inside with concrete filled inside both the inner and outer tubes. The lips in the outer steel section behave as longitudinal stiffeners. To investigate the axial compression behaviour of these columns, fourteen CFDSSTs were designed and fabricated as well as two concrete-filled stiffened steel tubular (CFSST) columns and two concrete-filled double steel stiffened tubular (D-CFSST) columns for comparison. The columns failed due to local buckling of the outer steel tubes. The columns were modelled using finite element analysis and the accuracy and reliability of the numerical data was determined by comparing the numerical and experimental results. The validated model was employed to conduct a parametric analysis to investigate the behaviour of CFDSST columns with different variables and properties. The results show that the ultimate strength of CFDSST columns is most significantly influenced by the presence and strength of the sandwiched concrete between the two steel sections. The paper also presents an analysis of the accuracy and reliability of different international codified methods for predicting the load-carrying capacity of CFDSSTs. • Behaviour of concrete-filled dual steel-stiffened tubular (CFDSST) short columns is provided. • A series of experimental tests are described, assessed and employed to validate FE models. • The results showed that CFDSST columns have high ultimate load and superior ductility. • The accuracy of different codified resistance methods of CFDSSTs has been assessed. [ABSTRACT FROM AUTHOR]

In this paper, a pinned scaffolding node is proposed and studied with Q355 steel and sorbite stainless steel. Twelve sets of forward and reverse bending tests were designed to study the bi-directional bending performance at temperatures of +20 °C, −20 °C, and − 40 °C. The test results show that as the temperature decreases, the initial rotational stiffness and bearing capacity of the QSJ and the SSSJ both increase. Under the same temperature conditions, the yield bearing capacity and maximum bearing capacity of the SSSJ are greater than those of the QSJ. However, the SSSJ is susceptible to cracking in the weak zone of the C-shaped member subjected to forward bending moments in low-temperature environments, which requires attention in design and use. A finite element model can accurately simulate the bi-directional bending performance of the joint. The results show that increasing the thickness of the U-shaped members by 1–1.5 mm significantly increases the maximum load capacity of the joint. The wall thickness of the pipe has no influence on the bending properties of the joint, but the initial stiffness of the joint can be increased by the depth of wedging, a wall thickness of 6 mm is recommended for C-members. The form of damage to the SSSJ can be improved by increasing the curvature of the upper edge of the C-member at the wedge. The results of this paper can provide methods and references for the engineering design of scaffolding as well as for testing in low-temperature environments. • This paper adopts the separated low temperature loading device, which is convenient for the installation and disassembly. • This study presents a low-temperature loading test device and method. It can provide a test environment of −70 °C ∼ 150 °C. • It's innovative to study the material properties of cable body stainless steel and Q355 at −40 °C, −20 °C and room temperature. • The mechanical properties of the pin-type scaffolding nodes using sorbite stainless steel and Q355 at low temperature were investigated. [ABSTRACT FROM AUTHOR]

In this paper, through on-site investigation and monitoring, the characteristics of roadway deformation and the causes of deformation and damage are analyzed. Among them, the unreasonable support system is an external factor, and the nature of rock mass, deterioration degree of surrounding rock, and high ground stress are internal factors. A simulation method of CFST considering initial defects in core concrete is proposed and utilized to analyze the mechanical properties of CFST supports. Building upon numerical simulation results, we introduce an optimized support scheme comprising annular CFST support, segmental fissure surrounding rock grouting, and bolts. Field comparison tests demonstrate that the application of the new repair technology yields remarkable enhancements in the bearing capacity of surrounding rock and supporting structures while ensuring a more uniform stress distribution within the rock mass. • Deep roadways' deformation causes are analyzed from multiple perspectives. • This paper introduces the control technology of high bearing capacity pressure equalizing support. • A simulation method of CFST considering initial defects in core concrete is proposed. • Based on the finite element model, the support scheme is further optimized and applied on site. [ABSTRACT FROM AUTHOR]

High-strength steel (HSS) welded H-section beams are increasingly used in steel structures considering their advantage of high strength, but the stability is a concern especially near the supports, where the beams are prone to buckling under the combined actions of bending and shear. In this paper, finite element method was used to analyze the mechanical performance of HSS welded H-section beams under shear and bending-shear loads. A parametrical analysis for the H-section beams under pure shear loads was conducted, and a new shear buckling coefficient calculation method considering the interaction between plates was proposed. This coefficient was then applied to calculate the shear strength, and a design method for shear buckling strength based on the direct strength method (DSM) was proposed. Finally, a new bending-shear interaction curve was developed to predict the ultimate resistance of HSS welded H-section beams under bending-shear combination, and the reliability analysis results demonstrate the feasibility and safety of the design method proposed in this paper for HSS welded H-section beams. [Display omitted] • Calculation method for elastic shear buckling coefficient of H-section beams under shear. • The Direct Strength Method for high strength steel (HSS) welded H-section beams under shear. • A new bending-shear interaction curve for HSS welded H-section beams under bending-shear combination. • Reliability analysis of the new design proposals. [ABSTRACT FROM AUTHOR]

This paper presents herein pertains the experimental and numerical investigations on axial compressive behavior of square concrete-filled stainless steel tube (CFSST) columns after high-temperature sliding. A total of 117 CFSST specimens were tested under axial compression loading. The design variables included tube thickness, temperature, duration, and concrete compressive strength. Test results indicated that the initial stiffness of square CFSST short columns was degenerated due to high-temperature sliding. CFSST specimens exhibited a 62.7% lowest residual strength at 1000 °C. The influence of high-temperature duration on the residual strength of square CFSST short columns after high-temperature sliding was limited. The residual strength of specimens was positively correlated with the thickness and concrete strength. All square CFSST columns after high-temperature sliding experienced an outward local buckling under axial compression. Finite element models of square CFSST columns after high-temperature sliding are established and validated against the experimental results. In addition, the parameter formulae of residual strength for CFSST columns after high-temperature sliding were proposed, which achieved high accuracy. This research results could provide strengthening reference for the application of CFSST columns after high-temperature sliding. • Axial compressive behavior of square CFSST columns after high-temperature sliding were investigated in this paper. • The effects of tube thickness, temperature, duration, and concrete compressive strength are analyzed. • Finite element model (FEM) of square CFSST columns after high-temperature sliding were established. • Parameter formula was proposed to estimate residual strength for square CFSST columns after high-temperature sliding. [ABSTRACT FROM AUTHOR]

This paper presents the parametric analysis and design method for the concrete-encased hexagonal concrete-filled steel tubular (CFST) column base under combined compression and biaxial bending. The corresponding experimental and numerical investigations on the seismic performance of the concrete-encased hexagonal CFST column base under combined compression and biaxial bending have been presented in the companion paper (Yang et al., 2023). The finite element model established in the companion paper is used to study the influence of key parameters on the load bearing capacity and the distribution of internal force. These parameters include those of the CFST column, the outer RC, the plate-anchor component, the axial load ratio and shear connectors. A total of six failure modes are identified, including three types of flexural failure and three types of shear failure. The ultimate capacity and ductility of the column base with flexural failure at the bottom or top of the plate are higher than that of other four failure modes, which are determined as the reasonable failure modes for practical application in the design and analysis of concrete-encased column bases. A novel design approach for the concrete-encased CFST column base is introduced. A simplified method is proposed to predict the flexural resistance of the concrete-encased CFST column base, following up with the shear strength calculation of outer RC to determine the stirrup arrangement. Some constructional recommendations are also proposed. • A parametric study is presented to investigate the effect of major parameters on the failure mode and internal force distribution of the concrete-encased column base. • A simplified strength model for concrete-encased column base under combined compression and biaxial bending is presented. • Constructional recommendations for the concrete-encased column base under combined compression and biaxial bending are proposed. [ABSTRACT FROM AUTHOR]

The cold-formed steel (CFS) frame has the advantages of high strength, light weight, high construction efficiency, so it has been widely applied in building structures. However, the research on the seismic performance of multistory frames, especially those with braces, is rarely reported, the design method is also incomplete. In view of this, a pseudo static experiment of a three story double leg C-section CFS frame with brace is carried out. The bearing capacity, ductility, stiffness degradation and energy dissipation performance of the specimens are studied. The finite element analysis (FEA) method is used to simulate the failure process of the CFS frame and the design suggestions are proposed. The experiment result show that the failure process of the cold-formed thin-walled frame without braces has satisfactory ductility and energy dissipation performance; For framed CFS frame, the lateral stiffness and bearing capacity of the CFS frame increases, but the ductility decreases. Replacing double angle steel brace by steel plate strip brace can improving the seismic performance of structures, but there is an optimal width thickness ratio of steel plate strip. In this paper, the optimal width thickness ratio of brace is 5.0. When the design suggestions proposed in this paper are met, the CFS frame can achieve "strong structure, weak brace", so as to improve the seismic performance of the frame. • A double leg C-type cold-formed thin-walled steel frame with backing plate is proposed. • The seismic performance of a new cold-formed thin-walled steel frame is tested and the role of bracing is analyzed. • The simplified analysis model of the new frame is given. • Through finite element simulation, the optimization design method and key parameters of the bracing are given. [ABSTRACT FROM AUTHOR]

In this paper, the pure bending tests on six specimens were carried out with the cross-sectional forms (unstiffened, stiffened, and multi-cell) and the loading angles (0° and 45°) as the variable parameters. The failure modes, bending moment-deflection curves, deformation characteristics, flexural strength, and stiffness of the specimens were obtained. The results indicated that the flexural strength and initial flexural stiffness of stiffened and multi-cell cross-shaped CFST members can be improved compared with the unstiffened members. The loading angle has no significant effect on the flexural performance of the cross-shaped members. Finite element models of cross-shaped CFSTs under pure bending were established, considering the residual stress and cold-formed strengthening effect, and the finite element results were in good agreement with the test results. Based on the parametric analysis, the design methods of flexural strength and flexural stiffness of stiffened and multi-cell cross-shaped CFST members were proposed. • Six cross-shaped CFST members were tested under pure bending. • Stiffeners or multi-cell form can improve flexural strength and stiffness. • Finite element models of cross-shaped CFST members were established. • Design methods for flexural strength and stiffness were developed. [ABSTRACT FROM AUTHOR]

Cable clamps are crucial for connecting component and transmitting prestress in cable structures. The anti-slip performance of the cable clamp is an important factor affecting the stability and safety of the structure. This paper introduces a novel test device to evaluate the anti-slip performance of arc groove cable clamps, and anti-slip performance experiments are performed on four arc groove cable clamps and four straight groove cable clamps. Long-term high strength bolt preload loss tests are conducted to investigate the loss pattern. Furthermore, seventeen parametric finite element models are developed to analyze the effects of groove bending angle, bolt length, cable force, and pressure plate stiffness on the anti-slip performance of arc groove cable clamps. It is found that the arc groove cable clamp exhibits a higher anti-slip bearing capacity, with a friction coefficient equivalent to that of the straight groove cable clamp, both exceeding 0.2. The bolt preload stabilizes at a certain value after 96 h of screwing the bolt, while it stabilizes after 24 h of tensioning the cable. The increase in the bolt length and angel of arc groove, as well as the reduction in the stiffness of the pressure plate, have a positive impact on the anti-slip bearing capacity of the arc groove cable clamp. There is a critical cable force that results in the lowest anti-slip bearing capacity of the arc groove cable clamp. These research results provide valuable insights for the design and engineering application of arc groove cable clamps. • A test device for evaluating the anti-slip performance of arc groove cable clamps was designed. • A calculation formula for the anti-slip bearing capacity of arc groove cable clamps was proposed. • The anti-slip performance of straight and arc groove cable clamps was compared through experiments. • Long-term loss law of high-strength bolt preload was investigated. • Numerical simulations were conducted to study the factors influencing the anti-slip performance of arc groove cable clamps. [ABSTRACT FROM AUTHOR]

In this paper, a prefabricated concrete-filled square steel tube (CFSST) fully-bolted exterior diaphragm joint was proposed. To clarify the influence of axial compression ratio, beam-column linear stiffness ratio and steel tube wall thickness on the seismic performance of joints, four 1/2 scaled specimens were designed and fabricated to perform quasi-static tests. The failure characteristics, hysteresis performance, energy dissipation capacity, ductility, bearing capacity degradation, stiffness degradation of each specimen were analyzed comparatively. The findings demonstrate that the failure mode of joints was mainly characterized by significant buckling deformation of the upper flange of the beams. Increasing the axial compression ratio, steel tube wall thickness and beam-column linear stiffness ratio will improve the bearing capacity and energy dissipation capacity of the joint. The effect of axial compression ratios and beam-column linear stiffness were further discussed through finite element analysis (FEA). According to the results, the axial compression ratio and beam-to-column linear stiffness ratio had a significant effect on the bearing capacity and the axial compression ratio of 0.5 had the best seismic performance. • A prefabricated concrete-filled square steel tube (CFSST) fully-bolted exterior diaphragm joint was proposed. • The failure mode, bearing capacity, ductility and energy consumption of the new joints were obtained from the tests. • The joints were connected with full-bolts flanges, which greatly improved on-site assembly efficiency and avoided on-site welding. • The different parameters of the new joint were investigated by numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, the ductile fracture prediction method based on micromechanism of low yield point steel LY225 under cyclic loading is studied based on acoustic emission (AE) entropy. Firstly, the parameters of the cyclic void growth model (CVGM) were calibrated by a series of repeated loading tests of the circumferentially notched specimens, and then the quantitative relationship model between the cumulative AE entropy and the cyclic void growth index (CVGI) of LY225 under low-cycle fatigue load was established through reciprocating loading tests, real-time acoustic emission monitoring and finite element analysis of variable cross-section flat specimens. The cumulative AE entropy was used as the ductile fracture evaluation index to realize the prediction of ductile fracture under low-cycle fatigue load. Different from the monotonic tensile loading situation, when the material undergoes repeated loading, it will accumulate AE entropy according to the changes in VGI during the tensile and compressive cycles. Based on this, the quantitative relationship model between the cumulative AE entropy under cyclic loading and the cyclic void growth index CVGI has been revised. Finally, the micro element method was used to predict the cumulative AE entropy curve of the plastic zone of the variable cross-section flat plate specimen under repeated loading. The predicted curve was in good agreement with the experimental results, verifying the applicability and accuracy of the modified bilinear quantitative relationship model under low cycle fatigue loading. [Display omitted] • CVGM fracture parameters of LY225 steel are calibrated. • A quantitative damage evaluation method of LY225 steel under cyclic load based on AE monitoring technology is proposed. • A modified bilinear model between cumulative AE entropy and cyclic void growth index CVGI is established. • The proposed model can be used in quantitative damage evaluation and ductile fracture prediction. • The effectiveness of the model in more complex stress and strain state is verified by a series of tests. [ABSTRACT FROM AUTHOR]

This study examined the hysteretic behaviour of Square Hollow Section (SHS) T- and X-joints subjected to cyclic in-plane bending moments. A nonlinear finite element software, Abaqus, was used to investigate SHS T- and X-joint seismic performance. Prior to the parametric study, the numerical model was validated based on the available test results in the literature. A comprehensive parametric study employed validated finite element models to evaluate the influence of critical geometric parameters, including the brace-to-chord width ratio (β) and the chord width-to-thickness ratio (γ). The results of the finite element analyses regarding ductility, flexural strength, and energy dissipation behaviour of SHS T- and X-joints under quasi-static cyclic in-plane bending were evaluated. Based on the hysteretic curves, increasing β generally leaded to higher initial stiffness and moment capacity in SHS joints, considerably reducing joint rotation. Conversely, the joints with larger γ exhibited reduced initial stiffness and moment capacity. Besides, the Eurocode 3 EN1993-1-8 predictions for the ultimate flexural strength of the joints are found to be conservative compared to finite element results. The results also revealed that the SHS T- and X-joints showed satisfactory ductility levels under in-plane bending load. It was observed that the SHS T- and X-joints with high β and low γ are advantageous for absorbing energy under seismic loads. These findings offered valuable insights for the seismic-resistant design of structures incorporating SHS joints, aiding in selecting optimal configurations based on specific performance requirements. • This paper presents a numerical study of hysteretic behaviour of SHS T- and X-joints with IPBM. • An increase in β ratio generally corresponded to higher initial stiffness, moment capacity, ductility. • The joints with large γ ratio exhibited reduced initial stiffness, moment capacity and ductility. • Eurocode 3 predictions were conservative in estimating the ultimate flexural strength of the SHS T- and X-joints under IPBM. • SHS T- and X-joints with high β and low γ were advantageous for absorbing energy under seismic loads. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and numerically the axial loading behaviour of Ultra-high performance concrete (UHPC) (135 MPa)-filled double skin steel tubular columns. A total of 37 stub columns (450 mm long x 152 mm diameter) were tested, including totally filled control tubes and tubes filled with normal- and high-strength (NSC and HSC) concrete. The study examined the effects of outer tube diameter-to-thickness (D o / t o) ratio and inner-to-outer tube dimeter ratio, which reflects UHPC wall thickness, on axial strength. A nonlinear finite element model using computer program LS-DYNA was also developed and verified. The study showed that the stubs with the thinnest outer tube (D o / t o = 72) and largest inner void ratio (0.7) achieved equivalent strength to the NSC (41 MPa) totally filled thickest tube (D o / t o = 32). Failure occurred by outwards local buckling of the outer tube and inwards buckling of the inner tube, along with UHPC diagonal shear failure. The peak load reduced nonlinearly as D o / t o increased due to a transition from a class 1 to class 2 section, and the post-peak load drop increased with increasing concrete strength (f c ′) and (D o / t o) ratio. As UHPC thickness reduced to a 50% volume reduction, axial strength reduced by 20–28%. The Canadian CSA S16:19 code provisions overestimated axial strength by 12–56%. A modification factor was developed and is recommended to be introduced in the code equation. • Double-skin tubes uses thin ultra-high performance concrete (UHPC) fill in between. • Outer tube thickness and concrete wall thickness were varied in short columns. • Superior strength-to-weight ratio to normal strength concrete totally filled tubes. • A 3D nonlinear finite element model was developed and verified to assess behaviour. • A modification to CAN/CSA S16 is proposed based on multiple regression analysis. [ABSTRACT FROM AUTHOR]

This paper presents a series of validated finite element (FE) models geared to parametrically examine the effects of initial web out-of-flatness imperfections on the shear strength and behavior of steel plate girders under pure shear. The prototype girder models are based on field measured imperfection shapes and magnitudes, with variations in web slenderness (93, 109, and 118) and panel aspect ratio (0.89, 2.02, 2.22, and 2.29). Additional model cases are analyzed by incorporating idealized eigenmode shapes and scaled to web out-of-flatness tolerance limits per AASHTO/AWS D1.5. The FE strength results are compared against various code-based nominal shear strength predictions. The following key findings are derived: (1) field measured and eigenmode imperfections exhibit similar shear behavior and deformation response throughout all shear mechanism stages; (2) the yield mechanism of a stiffened web panel in shear is negligibly impacted by the initial imperfections of the web and is triggered by second-order flexural bending from in-plane shear-induced compression; (3) an initial imperfection with an eigenmode shape and a maximum magnitude ranging from d/300 to d/600 (where d equals to the least panel dimension) can suitably approximate the shear strength of plate girders when compared with field measured imperfections; and (4) code-based nominal shear strength predictions demonstrate to be conservative for web panel aspect ratios ≥2.0. [Display omitted] • Effects of initial web out-of-flatness imperfections on shear strength are studied. • Finite element modeling based on panel extension models was utilized. • Effects of field-measured imperfections are similar to those of eigenmode shapes. • First positive eigenmode with a peak magnitude of d / 300 to d / 600 is recommended. • Code-based predictions are unconservative for a / D =0.89 but conservative for a / D ≥2.0. [ABSTRACT FROM AUTHOR]

This paper deals with the face plate component in steel joints and addresses the full characterization of the nonlinear behaviour of the face plate component. An equivalent beam strip model is proposed that tackles the connection of a beam to the column web of open I-sections in a minor axis joint or the face of tubular columns, covering endplate or fin plate joint typologies. Closed-form analytical solutions are obtained for the elastic large displacement and the elastic-plastic large displacement behaviour of the equivalent beam strip. Criteria for the establishment of the design resistance using the continuous strength method are also proposed. It was concluded that the model is easy to apply, was validated against a large parametric study using finite element beam models, leads to accurate solutions and demonstrates the need to consider membrane effects in design. • Elastic large displacement exact solution for beam strip subject to patch load. • Elastic-plastic large displacement solution for beam strip subject to patch load. • Application of CSM (Continuous Strength Method) to establish design resistance. • Model applicable to component face plate not yet covered by design standards. [ABSTRACT FROM AUTHOR]

Composite shear walls are usually employed at the bottom of super high-rise structures to resist large axial forces, bending moments, and shear forces. A lot of investigations have been carried out on composite shear walls, but there are fewer comparative studies on composite shear walls with different steel layouts. In this paper, low cyclic horizontal loading tests were carried out on conventional reinforcement concrete shear walls and composite shear walls with different steel layouts (H-section steel in boundary members and the steel plate in the shear wall web, H-section steel in boundary members and the slotted steel plate in the shear wall web, evenly arranged H-shaped steel in the wall). Comparative analyses of load-carrying capacity, failure modes, and seismic performance were conducted. The effects of different steel layouts on the seismic performance of composite shear walls were investigated. Based on the tests, the finite element method is used to further analyze the influence of the shear span ratio of the shear wall and the opening rate of the built-in slotted steel plate. • Low cyclic horizontal loading tests were carried out on conventional reinforcement concrete shear walls and composite shear walls with different steel layouts. • The effects of different steel layouts on the seismic performance of composite shear walls were investigated. • The parametric analysis of the composite shear walls with different steel layouts was conducted based on numerical simulation. [ABSTRACT FROM AUTHOR]

Shear truss steel panels are the main constituents in the construction of modular steel Bailey bridges. Buckling characteristics, and ultimate capacity of the panels are the main design parameters to be rationally predicted. The present paper presents full-scale tests on two types of typical shear panels. In addition, two distinctive three-dimensional finite element models were developed to analyze the response of the tested shear panels using beam-column elements and shell elements, which represent the simplified macro and micro modeling techniques, respectively. Both the eigenvalues (buckling) analysis and the nonlinear response analysis were conducted to predict both the buckling characteristic, and ultimate capacities, respectively. Correlation between predicted buckling loads from different modeling techniques revealed that to introduce an adjustment length factor K in the AASHTO-LRFD standards to accommodate rational end conditions and lengths of the compression members. Furthermore, the study revealed that the conservative prediction of buckling load stemmed from the method employed to calculate the buckling length, which leads to a conservative estimate of the compressive strength. • Experimental and analytical investigation for shear panels of Bailey bridges. • Buckling analysis of the shear panels using beam-column element and shell elements FE modeling. • Evaluation of the effective length used in AASHTOO code provision according to the experimental and the numerical results. • Introducing correction factors for the buckling effective length. • Validating the response and load-carrying capacity of the shear panels using 3D FE modeling. [ABSTRACT FROM AUTHOR]

This paper summarises the investigations carried out by the authors on traditional and member-rotated T- and X-joints made of cold-formed S900 and S960 steel grades tubular members with nominal 0.2% proof stresses (equivalent to yield strengths) of 900 MPa and 960 MPa, respectively. Static structural performance of two traditional and three member-rotated configurations of tubular T- and X-joints undergoing axial compression load through brace members was investigated. The experimental investigations included 165 tests and targeted different failure modes in the chord members of the investigated joints. In addition, 32 tensile and compression coupon tests were also carried out by the authors to determine the tensile mechanical properties of these tubular members. Finite element (FE) models were developed and verified against the test results by duly showing the capability of reciprocating experimental joint strengths, failure modes, and load-deformation curves. Upon validations of the developed FE models, comprehensive parametric studies comprising 2254 finite element models were performed. In order to examine the applicability of existing design rules for the investigated high strength steel tubular joints, static strengths obtained from tests and numerical studies were compared with nominal strengths calculated from design equations given in Eurocode 3, CIDECT, and literature. Generally, it has been demonstrated that the existing design rules cannot provide accurate strengths for the investigated joints. Therefore, the authors have proposed user-friendly, accurate, and reliable design rules to predict the static strengths of cold-formed S900 and S960 steel grades traditional and member-rotated tubular T- and X-joints. • Investigations carried out by the authors on CFHSS traditional and member-rotated T- and X-joints have ben summarised. • Experimental and numerical studies comprised five configurations of tubular T- and X-joints, including 2419 specimens. • New concept and definition of weld heat affected region and strength reduction model have been proposed. • Current design rules are generally found inaccurate and unreliable for the range of investigated joints. • User-friendly, economical, and reliable design rules have been proposed to predict static strengths of investigated joints. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) has recently been applied as an alternative to normal concrete in steel-concrete composite structures. In this paper, a novel compact steel-concrete joint with UHPC grout, which utilizes shear connectors, a bearing plate and a simple I-shaped steel girder, is proposed for long-span railway hybrid girder bridges. To investigate the mechanical behavior and force transfer characteristics of the proposed compact steel-UHPC joint (CSUJ), a model test with reduced scale and push-out tests of its main force transfer components were conducted. The specimens' failure model, load-interface slip, and strain development were compared and discussed in detail. Furthermore, a finite element model of the CSUJ was established to investigate the internal damage evolution and the load transfer path. The test results indicated that the steel-UHPC joint possessed excellent axial stiffness and cracking resistance. The axial stiffness before cracking is 2.6 times that of the steel-concrete joint prototype with C60 concrete grout. Upon loading, the filled-in UHPC of the CSUJ was in elastic compression. In the ultimate limit state, the steel-UHPC joint exhibited great integrity, and the ultimate failure mode of the CSUJ was controlled by the adjacent axially loaded steel beam segment. Results of push-out tests showed that the force transfer component with perfobond leiste (PBL) connectors demonstrated greater ductility than other transfer components. In terms of the force transfer rate and uniformity, the proposed CSUJ provides desired stress distribution and force transfer behavior. The shear connectors, bearing plate, and end face of the I-girder transferred 49%, 35%, and 16% of the total axial force, respectively. • A novel compact steel-concrete joint with UHPC grout was proposed for long-span railway hybrid girder bridges. • A model test with reduced scale and push-out tests of its main force transfer components were conducted. • A finite element model was established to investigate the internal damage evolution and the load transfer path. [ABSTRACT FROM AUTHOR]

Stainless steel materials are high ductility and strain hardening under cyclic loading, which is promising in seismic design. However, the current European stainless steel structure design code prEN 1993-1-4(EC3) ignores this favorable effect in the cross-section classification, as well as the lack of prediction formulas for the ultimate capacity of H-section under cyclic loading. In this paper, parametric analysis was carried out for H-section to extend the database based on the existing test results after calibration of the finite element model. The cross-section classification criteria of duplex stainless steel beams and beam-columns around major-axis under cyclic loading were investigated, and the EC3 classification of stainless steel H-section was evaluated. The predicted results for EC3 are conservative due to not considering the constraints of the cross-section component plates and the favorable conditions for the material strengthening of stainless steel under cyclic loading. Based on this, classification criteria for stainless steel H-section under cyclic loading were proposed and summarized. Subsequently, the method of calculating the ultimate capacity methods under cyclic loading suggested by EC3, Chen and Zhou et al. were evaluated. The results show that EC3 is on the conservative side, with actual results being generally 1.5 times higher than the predictions. In contrast, Chen and Zhou et al.'s method is on the unsafe side of the prediction. Finally, improvement suggestions are given for EC3 and the continuous strength method by considering the over-strength factor under cyclic loading, respectively, with results exhibiting high accuracy. • Classification criteria for duplex stainless steel H-section around major-axis under cyclic loading was studies. • Evaluated the cross-section classification criteria and ultimate capacity according to EC3 design codes. • New cross-section classification criterion for H-section under cyclic loading was proposed and summarized. • Two methods of ultimate capacity were modified and shown to offer improved design accuracy. [ABSTRACT FROM AUTHOR]

This research introduces the recentering energy dissipation bracing with a pendulum in prefabricated steel frame (REBP-PSF) structures. The primary objective of this study is to mitigate potential severe damage to steel frames during seismic events and to expedite postearthquake rehabilitation. This innovative system harnesses energy dissipation through friction between structural members and facilitates recentering through the cable pretensioning force. Consequently, this may make postearthquake repairs minimal or even unnecessary. Three REBP-PSF structures and a prefabricated steel frame with cantilever beam splices (PSF-CBS) were meticulously modeled using the ABAQUS finite element method to evaluate the seismic performance of this novel system. The study investigated the effects of pretensioning parameters and varied structural morphologies on seismic performance metrics, including failure modes, hysteresis performance, energy dissipation capacity, and residual displacements. This paper introduced a simplified method to simulate the restoring force model of REBP using the connection element method. Subsequently, a model for the REBP-RSF overall structure was established, enabling nonlinear dynamic time-history analysis, which was then compared with the rigid steel frame (RSF) structure. The results showed that the REBP-PSF structure outperformed the PSF-CBS in terms of initial stiffness, yield load, ultimate load, and energy dissipation capability. The bearing and energy dissipation capacities of the REBP-PSF structure were enhanced by augmenting the cable pretensioning force within this structure. The proposed connection element method could accurately simulate the hysteretic behavior of REBP. Compared with the RSF structure, the REBP-RSF demonstrated superior seismic performance, characterized by small story drift and residual displacements during seismic activities. Furthermore, a notable augmentation was observed in the lateral stiffness and torsional rigidity of the proposed structure. • The REBP-PSF structure is proposed and its seismic performance is analyzed. • The REBP-PSF structure dissipates energy through friction between REBP. • The connection element method is proposed and verified. • The REBP-RSF structure based on the connection element method is established. [ABSTRACT FROM AUTHOR]

An innovative cold-formed steel center-sheathed shear walls (CFSCSSWs) was proposed in this paper to improve the horizontal load-carrying capacity of conventional cold-formed steel walls. However, the fire behavior of this wall configuration was particularly worthy of attention because it was designed to be used in multi-story buildings, and there is still a lack of in-depth exploration of the fire performance and high-temperature horizontal load-bearing capacity of CFSCSSWs under combined loads. In this study, a compression test was first carried out to obtain the vertical load-carrying capacity of a full-scale CFSCSSW, followed by a fire test on a similar CFSCSSW subjected to combined vertical and horizontal loads to investigate the fire behavior of walls. Then, a finite element model was established and validated by test results to investigate the influence of various critical factors, including vertical and horizontal load ratios, height-width ratio, and sheathing thickness, on the fire behavior of the CFSCSSW. The results showed that the vertical load ratio presented a larger influence on the fire behavior of CFSCSSWs compared to the horizontal load ratio. The increasing aspect ratio can slightly improve the fire resistance of the wall under the same load ratio. The wall with a 0.8 mm thick sheathing exhibits better fire behavior under the same load ratio. A high-temperature horizontal load-carrying capacity calculation method for CFSCSSWs was proposed, and its good accuracy was found. • Load capacity of cold-formed steel center-sheathed shear wall was investigated experimentally and numerically. • Parametric analysis was conducted to investigate the influence of key parameters on the fire behavior of the wall. • A method for predicting high-temperature horizontal load capacity of the wall was proposed. [ABSTRACT FROM AUTHOR]

Previous research focused on the development of guidelines to load rate highway bridges constructed out of repurposed railroad flatcars (RRFCs). Those guidelines were based on field testing and finite element analysis conducted on existing RRFC bridges both in the field and in the lab. However, load rating is only one of the issues related to RRFCs as the main components are often classified as fracture critical members (FCMs) since there are only two flatcars in the cross section in most instances. Classifying the individual RRFCs as FCMs requires a rigorous hands-on inspection as per the Code of Federal Regulations, which greatly increases the long-term costs associated with these structures. Hence, while they are attractive to many owners due to their low initial costs and considerable strength, long-term costs due to inspection have deterred some owners from utilizing this viable and renewable alternative for low-volume applications. This paper presents the results of laboratory testing and non-linear finite element analysis of a railroad flatcar bridge specimen constructed with a composite reinforced concrete deck. The results confirm that RRFCs have considerable reserve strength and adequate load redundancy in a severely faulted state and need not be classified as FCMs if certain requirements are met. The paper also presents recommendations for load redistribution factors between primary members of RRFCs obtained through the experimental and verified by numerical studies. • RRFCs as the main components are classified as fracture critical members (FCMs) per codes. • Experimental behavior of fractured RRFC bridge specimens were investigated. • Benchmark finite element models were developed based on the experimental results. • Results confirm that RRFCs have considerable reserve strength and adequate load redundancy. • Recommendations for load redistribution factors between primary members are presented. [ABSTRACT FROM AUTHOR]

The companion paper Part I [ 1 ] deals with the experimental campaign of longitudinally stiffened plate girders subjected exclusively to patch loading. The current paper focuses on the numerical research and parametric study of the influence of patch load length and initial geometrical imperfections on the ultimate strength of longitudinally stiffened plate girders. In order to assess the patch load resistance, a geometrically and materially nonlinear finite element analysis has been performed. For a better verification with the experimental results, the finite element model includes the experimentally measured initial geometrical imperfections and material properties based on laboratory tests. The verification of the numerical model has been obtained through the comparison of the numerically and experimentally attained results for the ultimate loads and elastoplastic behavior of the girders. It has been shown that the numerical and experimental results are in perfect agreement, which enabled a fruitful background for parametric analysis, in which different initial geometrical imperfections have been used to ameliorate understandings about their influence on the ultimate strength under different patch load lengths. Conclusively, it may be stated that initial geometrical imperfections can play a decisive role, especially for longitudinally stiffened girders. Initial geometrical imperfections of stiffened girders that correspond to deformed shape at the collapse (collapse-affine imperfections), especially in the zone where the load is applied, will give the most unfavorable ultimate strengths. For the considered geometry in the present paper, the third buckling mode of longitudinally stiffened girders corresponds to the deformed shape and the lowest ultimate strengths are obtained. • Initial geometrical imperfections can play a decisive role for both longitudinally stiffened and unstiffened girders. • Unfavorable initial geometrical imperfections correspond to deformed shape at the collapse. • Increasing the patch load length increases the strengthening effect. • The strengthening effect is highly influenced by the shape of initial geometrical imperfections and patch load length. • The lowest patch load resistance of longitudinally stiffened girders is obtained for the third buckling mode. [ABSTRACT FROM AUTHOR]

The paper is focused on a design approach to a T-stub component, which is key part in an analytical/numerical prediction of behaviour of the bolted end plate connections, by the Component Based Finite Element Method (CBFEM). The method combines the analytical Component Method and the numerical Finite Element Method (FEM). The distribution of internal forces is solved by the FEM. The connectors' behaviour is modelled by analytical models implemented into FEM as components. The method is developed for design of generally loaded complex joints with end plated where the distribution of internal forces is not clear. The resistance of the joint is controlled by limiting the plastic strain of plates and the strength of connectors, e.g. welds, bolts, and anchor bolts. The prediction of the initial stiffness and the deformation capacity is included natively. The T-stub in tension is investigated in this paper. CBFEM is verified on the research oriented model, which is validated against the authors' own experiments and the results from literature, and on the Component Method. • Design approach to a T-stub component by the Component Based Finite Element Method. • Validated against experimental results and verified against analytical models. • The method combines the analytical Component Method and the numerical FEM. • For design of generally loaded complex joints. • The prediction of the initial stiffness and the deformation capacity is natively. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an experimental study on a bolted joint for connecting H-section steel beams to square hollow structural steel (HSS) columns and connecting upper and lower HSS columns in a multi-storey prefabricated steel structure. The components within a module are welded together in the factory, and the modules are assembled on site using high-strength bolts. A rigid connection or a semi-rigid connection can be achieved by adjusting the number and size of bolts. The stiffness of semi-rigid bolted connection changes with the load. The connection is rigid during minor and moderate earthquakes, whereas during major earthquakes, the cover plate slips relative to the beam flange to dissipate energy. In this paper, model tests and finite element analysis (FEA) of the seismic performance under cyclic loads are conducted on six full-scale connections, and the results are compared with the results of a welded connection. The failure mode, slip behaviour, variation and distribution of the bolt tensions, and seismic performance of the connections, including the hysteretic behaviour, skeleton curve, ductility, rotational capacity and stiffness degradation, are obtained. The influences of the number of bolts and the thickness of cover plate on the mechanical and seismic properties are studied. The results show that a reasonable larger bolt hole can facilitate the installation and improve the ductility and energy dissipation capability without significantly affecting the load-carrying capacity of the connection. The results show that the proposed bolted connection has good hysteresis behaviour, energy dissipation and ductility. It is suitable for earthquake-resistant structures. Graphical abstract Unlabelled Image Highlights • A new type of bolted beam-column joint for high-rise steel structures is presented. • Cover plate slips relative to beam flange to dissipate energy during an earthquake. • Connection stiffness can be controlled by adjusting the number or size of the bolts. • Bolted slip connection raises the joint's ductility and energy dissipation capacity. • Tests and FEA of seismic performance are conducted on 6 joints under cyclic loads. [ABSTRACT FROM AUTHOR]

Abstract Spiral welded stainless steel tubes are produced by helical welding of a continuous stainless steel strip. Recently, spiral welded stainless steel tubes have found increasing application in the construction industry due to their ease of fabrication and aesthetic appeal. However, an in-depth understanding of the behaviour of these types of structural elements is still needed due to the insufficient experimental evidence and lack of rational design guidance. In the present paper, an extensive experimental program was carried out to investigate the behaviour of axially loaded hollow and concrete-filled spiral welded stainless steel tubes. The effects of various design parameters were investigated throughout the test program. In addition to the experiments, this paper presents a finite element model for the prediction of these columns. Specifically, the proposed finite element models take into account the effects of material and geometric nonlinearities. The helical welding is modelled as an independent part that is further tied to the stainless steel tube. Moreover, the initial imperfections of the stainless steel tube and the residual stresses resulting from helical welding are included. Enhancement of the understanding of the experimental results can be achieved by extending the parametric studies based on the developed finite element model. Furthermore, a comparison of the ultimate strength between the experimental results and those obtained from existing codes of practice is conducted. Highlights • Tests were carried out on hollow and concrete-filled spiral welded stainless steel tubes. • The effects of various design parameters were investigated. • FEM was proposed to carry out the additional parametric study was carried out. • Ultimate strength was compared with the current design provisions. • New design equation was proposed for this type of columns. [ABSTRACT FROM AUTHOR]

Abstract The local cross-section behaviour of stainless steel channel sections under the combined actions of axial compression and minor axis bending moment is investigated in the present paper and its companion paper, based on a comprehensive experimental and numerical study. Two channel section sizes were considered in the experimental programme, with the test specimens laser-welded at the two flange-to-web junctions from hot-rolled EN 1.4307 and EN 1.4404 austenitic stainless steel plates. The experiments involved initial local geometric imperfection measurements and 15 eccentrically loaded stub column (combined loading) tests. The loading eccentricity was varied to achieve a range of ratios of axial compression to minor axis bending moment; both orientations of bending (web in compression and web in tension) were considered. The test setup and procedures, together with the key experimental observations, including the load-carrying and deformation capacities, load-end rotation histories and failure modes, are fully reported. A finite element simulation study is then presented, in which the models were first validated against the obtained test results and then employed, in the companion paper, for parametric investigations and the assessment of design provisions. Highlights • Laser-welded stainless steel channel sections under combined compression and minor axis bending moment has been studied. • An experimental programme including 15 combined loading tests has been carried out. • Finite element models have been developed and validated against experimental results. [ABSTRACT FROM AUTHOR]

Abstract Concrete filled stainless steel tubular (CFSST) columns have attracted increasing research interests in the last decade. This paper briefly introduces the material properties of stainless steel and reviews recent research on behaviour of CFSST columns and joints at both ambient and elevated temperatures. The reviewed studies include tests of bond behaviour between the stainless steel tube and core concrete, and the static behaviour of CFSST stub columns, slender columns, beams, stainless steel-concrete-carbon steel double-skin tubular columns, and concrete filled bimetallic tubular columns. The cyclic behaviour of CFSST beam-columns under combined axial and lateral cyclic loading as well as the impact behaviour of CFSST columns is also introduced. Fire test results of full-scale CFSST columns are presented along with finite element analysis results. The behaviour of composite joints with CFSST columns is also briefly reviewed in this paper. Based on the previous research, future research directions on CFSST are summarised and discussed. Highlights • Behaviour of CFSST columns under various conditions • Behavior of composite joints with CFSST members • Further research needs of CFSST columns and structures. [ABSTRACT FROM AUTHOR]