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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]

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]

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 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]

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]

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]

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]

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]

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]

Considering the superior seismic performance of partially-encased composite steel and concrete (PEC) columns, aiming at the issues of poor ductility and out-of-plane stability found in traditional reinforced concrete (RC) short-limb shear walls. A novel approach has been proposed to achieve this goal involving PEC hidden columns and RC composite short-limb shear walls (PECSWs). This paper designed and executed quasistatic tests of two PECSWs and examined the failure mechanism of the specimens. To address the bond-slip failure problem between the PECSWs, the seismically damaged shear walls were restored by adding studs and subsequently underwent quasistatic testing after repair. Based on the seismic damage model of short-limb shear walls, model validation and parameter expansion analysis were carried out using finite element analysis (FEA). The test results indicate that the PECSWs experienced shear-bond failure under seismic action, while the repaired specimens experienced diagonal shear failure. The overall performance of the repaired specimens significantly improved. The parameter analysis indicates that the two measures of increasing the rebar diameter and reducing the rebar spacing were ineffective in improving the overall performance of PEC hidden columns and RC shear walls or reducing the effect of interfacial bond-slip. As the axial compression ratio, concrete strength, steel plate strength, and main steel component plate thickness increased, the lateral stiffness and bearing capacity of the shear wall improved, but the ductility decreased slightly. Based on the force transmission mechanism of the oblique belt-truss mechanism, a calculation formula for the shear bearing capacity of PECSWs is proposed. The theoretical calculations are in good agreement with the tests and FE results. • A new prefabricated PEC hidden columns and RC composite short-limb shear walls (PECSWs) structure was proposed. • The construction method of adding studs is adopted to repair the earthquake-damaged shear wall. • The seismic performance of the shear wall structure is studied through experimental analysis. • The calculation formula of the shear bearing capacity of the shear wall structure has been derived. • The finite element model is in good agreement with the test. [ABSTRACT FROM AUTHOR]

This paper proposes a new steel brace design that leverages the web buckling of low-yield I-section steel sections to achieve early energy dissipation under small story drift angles. The design incorporates a pair of U-channel steel components to restrain complex deformations in the low-yield I-section steel cores during seismic events. The study first introduces the design concept and presents the analytical formulations for the I-section steel optimized for enhanced seismic performance. Energy dissipation is achieved through the flexural yielding of the low-yield I-section steel's web during inelastic cyclic deformation. Finite element analysis of the designed brace reveals its potential for early energy dissipation and a stable load-carrying capacity. The model exhibits well-defined hysteretic behavior starting at low drift levels, with a slight decrease in strength observed under various loading sequences. The experimental test confirms the effectiveness of the designed brace, as evidenced by its stable and consistent hysteretic behavior and resilience. A parametric analysis further investigates the impact of key geometrical factors of the wide-flange steel on the seismic performance of the steel brace, focusing on the parameters including yielding length, length of I-section steel, clear height, and the number of cores. The results indicate that a brace with more I-section steel elements significantly enhances energy dissipation. Notably, the parametric study also highlights the critical role of the length of I-section steel in optimizing energy dissipation, with a longer length of I-section steel leading to reduced tensile forces, which affects the load-carrying capacity of the brace. • Innovative design of steel brace uses low-yield I-section steel and high-strength U-channel steel. • Early energy dissipation is achieved through flexural yielding of web in low-yield I-section steel. • Finite element analysis demonstrates potential for early energy dissipation and stable load-carrying capacity. • Experimental test confirms the effectiveness, stability, and resilience of the designed steel brace. • Parametric analysis explores the impact of key geometrical factors of the wide-flange steel. [ABSTRACT FROM AUTHOR]

This paper presents an innovative two-level shape memory alloy (SMA)-based self-centring (SC) steel column, referred to as TSSSC. The TSSSC is interconnected by two series of SMA bolts, differing in diameters and lengths, to achieve multi-yielding. This is intended to fulfil multiple performance-based design objectives and augment the structural ductility of SMA elements. Utilizing the distinctive material property of phase transformation inherent in SMA, the two-level bolts can accomplish multi-level yielding in a straightforward yet effective manner. This is achieved by employing SMA elements of varying diameters in series and sequentially activating them via the material's inherent stiffness hardening. The behaviours of the TSSSC are meticulously analysed through refined finite element models (FEMs), which are corroborated by previous test results. The TSSSC demonstrates commendable multi-yielding behaviour and SC capacity during cyclic behaviour studies. In comparison to conventional SMA-based SC structures, the TSSSC exhibits markedly superior ductility, exceeding 10, whereas traditional structures typically range between 4 and 6. This enhanced ductility ensures that the TSSSC can comprehensively meet the multiple design objectives stipulated in the current performance-based seismic design. The SC and energy dissipation (ED) capacity of the TSSSC can be activated during frequent seismic events, thereby providing a safety buffer for severe earthquakes due to seismic uncertainty. Furthermore, parametric studies are conducted to identify critical design parameters, including the vertical design load, prestress in SMA bolts, and the linear stiffness ratio between the short and long bolts of the two-level SMA bolts. Design recommendations are subsequently proposed based on the findings of these parametric studies. • An innovative two-level shape memory alloy (SMA)-based self-centring (SC) steel column (TSSSC) was proposed. • The TSSSC exhibits a desirable two-level-yielding flag-shaped hysteric response with minimal residual deformation. • The ductility of the TSSSC surpasses 10, higher than the typical range of 4 to 6 observed in traditional SMA elements. • Parametric numerical simulations were conducted to underscore the impact of crucial design parameters. • Design recommendations were provided for TSSSCs based on the parametric analysis results. [ABSTRACT FROM AUTHOR]

The T-stub bolted to Circular Steel Tube strengthened by Reverse-Channel using Thread-fixed One-side Bolts (TOBs) under tension was studied in this paper. Through welding a reverse channel, the regular bolted flat endplate connection could be employed for the steel beam to circular steel tube column. At the same time, the reverse channel also strengthens the tube wall and extends the hole thread length. Four TOBs bolted T-stub to Circular Steel Tube strengthened by Reverse-Channel (CST-RC) specimens were designed and tested under tension. Critical parameters were determined as the outer diameter of the steel tube, the tube wall thickness, and the bolt gauge distance. Test results revealed three typical failure modes: complete yielding of the whale tube wall, thread shear failure, and complete yielding of the whole tube wall with the thread failure. As well as the tube wall thickness could effectively increase the load-bearing capacity of the connection, a larger bolt gauge distance could reduce the connection deformation. Finite Element Models (FEM) were developed to analyze the load carrying mechanism of TOBs bolted T-stubs to CST-RC. The connection deformation contour, the yield line patterns of tube wall, and the stress distribution on the threads were presented. The behavior of TOBs bolted T-stubs to CST-RC was compared to that of TOBs bolted T-stubs to Circular Steel Tube (CST), and that of TOBs bolted T-stubs to Square Steel Tube (SST). It was found that the reverse channel effectively reduces the circular tube wall deformation and increases connection load-bearing capacity. • Experimental and numerical studies on TOBs bolted T-stubs to steel tube under tension was conducted. • Totally three failure modes for the connections were found in the test results and validated in FEM. • The deformation process of CST-RC is analysed in detail. • Make comparisons between CST-RC, CST and SST to find out the effect of Reverse Channel. [ABSTRACT FROM AUTHOR]

This paper presented the seismic performance of self-centering energy-dissipating link beams that rotate around the vertex. The effects of the connection types of NiTi shape memory alloy (SMA) bar and the material of energy-dissipating steel angle on the self-centering performance, energy-dissipation capacity, bearing capacity, ductility, rotation mode, and strain distribution of link beams were explored through tests. It was verified through theoretical calculation and finite element analysis method, and the specimens were improved in design. The results show that the self-centering link beams have typical flag-shaped hysteretic curves and have excellent self-resetting performances and energy dissipation capabilities. Plastic deformations were concentrated on the steel angles. LY160 steel angle can enable the link beam to obtain better self-centering performance, while the Q235 steel angle can improve the energy dissipation capacity. The full-length SMA bars link beam has better self-centering performance and energy dissipation capacity than the partition SMA bars link beam. The theoretical calculation and finite element analysis results are consistent with the testing results. The self-centering performances of the improved design specimens were improved, but the energy consumption capacities were slightly reduced. The steel angles of the self-centering link beam after an earthquake are easy to replace and can quickly restore the structural function, which effectively solves the post-earthquake large residual deformation and difficulty of repair of traditional link beam. • The self-centering link presented, which solve the large residual deformation and difficult repair of traditional link after earthquakes. • A quasi-static test was conducted, finite element and theoretical calculations verified the test results, an improved design was proposed. • The self-centering performance, energy-dissipation capacity, bearing capacity, ductility, rotation mode, and strain distribution were analyzed. • The connection types of SMA bars and steel angles suitable for self-centering link beams were derived. [ABSTRACT FROM AUTHOR]

This paper proposes a shuttle-shaped buckling restraint brace (SS-BRB) with the uniform core and the peripheral restraint system that consists of uniform cross-section tube at its mid span and tapering sections at its two ends. This type of BRB maned as SS-BRB-UCS adopts circular steel tubes in the core and the peripheral restraint system. An isolation system is strategically positioned between the core and the peripheral restraint system to effectively transmit lateral loads. Obviously, this type of the optimizing peripheral restraint system could reduce material utilization with an economic design and beautiful appearance. First, the finite element (FE) model of the SS-BRB-UCS is established, then the elastic buckling performance investigation is carried out to determine the elastic buckling load formula through fitting techniques of numerical results, so as to obtain the formula of the restraint ratio. Additionally, an elastic-plastic stability bearing capacity analysis is conducted for the SS-BRB-UCS to assess its load-bearing capabilities, and the corresponding relationships between stability coefficient (φ) and the restraint ratio (ζ) is established to determine the lower restraint ratio (namely threshold) for static load-bearing capacity BRB design. Finally, the hysteretic responses of SS-BRB-UCSs subjected to axial compressive-tensile cyclic loads are studied numerically, and the corresponding lower limit of restraining ratio of SS-BRB-UCSs is proposed for their energy-dissipation design. Those two lower limits of restraining ratios of the SS-BRB-UCSs obtained in this study provide fundamentals for preliminary static and seismic designs of SS-BRB-UCSs. • The formula for the elastic buckling load of SS-BRB-UCSs is derived and verified to define its restraining ratio. • SS-BRB-UCS with parameter α = 0.3–0.5 exhibits optimal economic design. • Load resistance and hysteretic responses of the SS-BRB-UCSs are investigated by adopting Finite Element Model (FEM). • Two lower limits of restraining ratios corresponding to load-carrying and energy-dissipating types are proposed. [ABSTRACT FROM AUTHOR]

In previous research on shear panel dampers (SPDs), the assumption that the damper only experiences in-plane loading has been predominant, neglecting the effects of bidirectional loading. This paper aims to provide a comprehensive understanding of the mechanical behavior of SPDs under bidirectional loading. Cyclic quasi-static tests and numerical simulations were conducted on both unstiffened and stiffened SPDs loaded in the in-plane direction and at a 45-degree angle, representing unidirectional and bidirectional loading, respectively. The results demonstrate distinct differences in failure mode, yielding, and stress distribution of SPD under bidirectional loading. To further investigate the influence of different loading angles on the mechanical properties of SPD, parametric studies were conducted. The findings reveal that the in-plane yield force of SPD gradually decreases as the loading angle increases, which raises the concern on the potentially overestimated the performance of bidirectional loaded SPD in the in-plane direction during structural design. • Mechanical behavior of shear panel damper under bidirectional loading was studied. • The stiffeners' impact on SPD in unidirectional and bidirectional cases was studied. • Effect of loading angles on the mechanical properties of SPD was studied. [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]

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]

With the proliferation of large-span structures and super high-rise building structures, further requirements have been placed on the bearing capacity and mechanical performance of special-shaped concrete-filled steel tubular (CFST) columns. In an effort to improve the performance of traditional T-shaped CFST columns, a series of axial compression experiments and numerical simulations were conducted on eight middle-long T-shaped CFST columns with embedded T-shaped steel skeleton, with the studied parameters covering diverse T-shaped steel tube confinement index (θ), embedded T-shaped steel skeleton ratio (ρ) and slenderness ratio (λ). The investigation contents include analysis of failure modes, load-mid span deflection curves, load-longitudinal and transverse strain curves, load-average longitudinal curves and parameter analysis. The experimental failure modes for all columns are a combination of local buckling and overall bending. Results demonstrate that the ultimate bearing capacity (N u) of the columns increases with higher values of θ and ρ while decreases with higher values of λ. As λ increases, the global bending failure of the column becomes increasingly pronounced. Furthermore, finite element analysis (FEA) models were built to simulate the axial compression mechanical performance of middle-long T-shaped CFST columns with embedded T-shaped steel skeleton. The simulation results were then compared with experimental results to validate the feasibility of the FEA models. Finally, simplified calculation formulae for estimating the ultimate load-bearing capacity of middle-long columns were suggested. The calculation results are indicative of notable agreement with the experimental results. • The paper presents an experimental study on T-shaped CFST columns with embedded T-shaped steel skeleton. • The composite columns shows excellent load-bearing capacity, ductility and deformation ability. • T-shaped steel skeleton improves the strength and the ductility capacity of composite columns • A finite element analysis for composite columns is developed. • A simplified calculation formula for composite columns is developed. [ABSTRACT FROM AUTHOR]

This paper aims to assess the influence of geometrical imperfections and residual stresses on the reliability of the stability design rules for steel columns in Eurocode 3 considering a full probabilistic approach and further validate the new buckling curves in the scope of the ongoing revision of the Structural Eurocodes. A reliability assessment of major- and minor-axis flexural buckling of high-strength steel (HSS) welded I-section columns was performed, considering all basic variables as random, including the geometrical and material imperfections, in addition to the material properties of steel and the geometry of the cross-section. An advanced finite element model calibrated with experimental test results is used to perform a very large (290,126 simulations) parametric study covering the majority of practical geometries. Subsequently, Monte Carlo simulation is used to estimate the design values of the buckling resistance that correspond to the target probability of failure of the Eurocodes. Finally, these values are compared to the proposed buckling curves for HSS columns, showing good agreement and supporting their adoption in the revised EN 1993–1-1. It is also concluded that it is on the safe side to carry out a reliability assessment with deterministic reference values for structural imperfections. [ABSTRACT FROM AUTHOR]

Cold-formed hollow structural sections are widely used in structural applications. Indeed, the high strength-to-weight ratio, the high torsional stiffness and the significant biaxial resistance of such sections make them suitable for columns of moment resisting frames. The interest on these sections is confirmed by the increasing number of studies aimed at developing a deep comprehension of the cyclic response of cold-formed hollow sections. Accurate and computationally effective numerical models are, however, still needed to model strength and stiffness deterioration of such members under cyclic loading. In this paper, the cyclic response of members with either square or rectangular hollow cross-section is simulated by means of a rigid beam with concentrated plastic hinges at the ends. The bending moment-chord rotation relation of these plastic hinges is simulated by means of the modified Ibarra-Krawinkler deterioration model. The values of the parameters of the model are calibrated against results of refined finite element numerical models to simulate both the cyclic and the first-cycle envelope responses of cantilever elements. Finally, predictive equations of the values of the parameters of the modified Ibarra-Krawinkler model are proposed as a function of the cross-section geometry, axial load ratio and shear span ratio. • Equations to predict the parameters of the MIK model for HSS members are formulated. • both the cyclic and the first-cycle envelope responses are considered. • residuals of the parameters are modelled so that Monte Carlo analyses may be performed. • laboratory tests available in the literature are used to validate the proposed equations. [ABSTRACT FROM AUTHOR]

Special-shaped concrete-filled square steel tube (SS-CFSST) columns are a type of prefabricated steel house structural form. They retain the characteristic high load-bearing capacity of the steel and concrete composite structures without protruding from the wall. This paper proposes a new type of connection form by improving the SS-CFSST column-steel beam outer sleeve connection. Cyclic loads were applied to nine specimens differing in terms of steel hoop width, side plate width, side plate length, and overall thickness. The failure modes, hysteresis curves, strength and rigidity degradation, and energy dissipation capacity are analysed in this study. The failure modes include side-plate fracture, beam-flange tear, and beam-plastic hinges. The hysteresis curves exhibit shuttle shapes without pinching. The equivalent viscous damping coefficients of the samples range from 0.16 to 0.26. Based on these results, a finite element model is established, and its accuracy is verified according to a comparison with the test results. A parameter analysis is also described herein. The results indicate that the key factors influencing the load-bearing capacity of these connections include (i) the thickness and height of the steel hoop and the side plate, (ii) the steel tube's width-to-thickness ratio, and (iii) the steel's yield strength. Specifically, the ratio of the height of the side plate on the beam flange's outer (h w) to inner (h n) dimension should not exceed 1.5. Moreover, the load-bearing capacity and stiffness of the connections are not affected when the axial compression ratio (n) is in the range of 0–0.6. • A novel special-shaped concrete-filled square steel tube (SS-CFSST) column to H-beam connection was proposed. • The seismic performance of the new connection was investigated based on nine specimens with different design parameters. • A parameter analysis was conducted on the factors affecting the bearing capacity of the connection. [ABSTRACT FROM AUTHOR]

This paper evaluates experimentally the cyclic response of a novel U-shaped steel plate proposed to dissipate seismic-induced energy through a unique mechanism called scissor bending. The cyclic behaviour of the U-shaped plate, including hysteresis response, plastic mechanism, strength and stiffness, ductility and energy dissipation capacities are examined. Four U-shaped steel plates varying in thickness are tested under cyclic loading. Furthermore, a mechanics-based method is proposed to estimate the stiffness and yielding strength of the fuse. The finite element model of the specimens is developed to reproduce their hysteretic behaviour and verify the stiffness and yielding capacity of the fuse. The results confirm that the proposed U-shaped steel plate demonstrate stable hysteretic behaviour and exhibit appreciable deformation ductility and energy-dissipating capacities. The U-shaped plate can be used as a seismic fuse in the design of frame structures. • A novel experiment investigates the cyclic behaviour of U-shaped steel plates (USP) undergoing scissor bending used as seismic fuses. • Investigation of USP asymmetric behavior under compression and tension, and validation of an analytical model for predicting fuse yielding capacity. • A systematic comparison between measured and calculated results proves insights into their relative conservatism and accuracy. • The numerical modelling underlines the impact of material strain hardening and residual stresses on predicting the cyclic behaviour of USPs. • The scissor bending application in USP specimens exhibits stable ductile behaviour and high seismic energy dissipation capability. [ABSTRACT FROM AUTHOR]

Concrete-encased concrete-filled double-skin steel tubular (CFDST) stub columns serve as structural members, encompassing an exterior reinforced concrete (RC) component alongside an internal CFDST component. In this paper, the eccentric compressive behavior of such stub columns was investigated. To this end, specimens with varying diameter-to-width ratios d o / w and eccentricity ratios e / w were examined; their failure process, failure modes, strain distributions, and representative mechanical performance were recorded and analyzed. Based on the experimental results, the specimens' failure process transitions through four stages: elastic, elastic-plastic, descending, and stabilizing. With d o / w escalating from 0.5 to 0.7, the eccentric compressive strength, flexural stiffness, and displacement ductility index improved by 16.1%, 15.2%, and 37.2%, respectively. Subsequently, a detailed finite element model (FEM) was established to analyze the eccentric performance of the concrete-encased CFDST stub columns. Following the FEM reliability validation, the working characteristics of such stub columns in the balanced failure mode were elucidated. The full-range analyses were carried out under failure modes controlled by compression and tension to unveil the loading distribution mechanisms. Moreover, the impacts of parameters like concrete compressive strength, diameter-to-width ratio, and steel tube yield strength on the N u – M u relation curves were quantified, ascertaining the key influencing factors. Finally, a formula was suggested to predict the corresponding eccentric compressive strength. Following the superposition principle and limit equilibrium theory, the simplified design equations put forth yielded satisfactory predictions based on the experimental and numerical results. • The CECFDST stub columns were subjected to an eccentric load examination. • The mechanisms of CECFDST stub columns under different failure modes were proposed. • The design method for CECFDST stub columns under eccentric load was developed. [ABSTRACT FROM AUTHOR]

Achieving favorable seismic performance in joints while maintaining flush alignment on the upper and lower surfaces of the beam flanges remains a current challenge. To address this issue, this paper introduces an innovative stepped beam-column joint. To study the seismic performance of the joint, four beam-column joint specimens with different configurations were tested under cyclic loading. The plastic development process, failure modes, hysteresis loops, skeleton curves, stiffness degradation, ductility, load-bearing capacity, and energy dissipation capacity of the joint specimens were carefully investigated. All joint specimens exhibited superior seismic performance and load-bearing capacity. Moreover, variations in plate configurations led to discrepancies in the final failure modes among different joint specimens. Finally, finite element models were established and verified for each joint specimen, and analyses of the tensile forces on outer bolts were conducted. Through the experimental and numerical analysis results, it was concluded that the proposed innovative stepped joint could exhibit excellent seismic performance, and could be recommended for practical application in engineering. • The cyclic performance of 4 beam-column joint specimens with stepped segment was studied. • The innovative stepped joints exhibit favorable load bearing capacity and seismic behavior. • The difference of joint configurations leads to different final failure modes of the specimens. • The FE models were established and verified with the experimental results. • The crucial role played by the outer bolts on the end plate surface was proved. [ABSTRACT FROM AUTHOR]

A novel point-supported rotational semi-rigid energy-dissipation connection for precast cladding panels (PRSEC) is proposed in this paper. The PRSEC, utilizing combined mechanical mechanisms involving friction and bending parts, could transform from a rigid connection into a flexible energy-dissipative connection as the seismic action increased. Theoretical predictions of PRSEC are presented, followed by a coordinated design method with the precast cladding panels. Subsequently, monotonic and cyclic loading tests are conducted to investigate the semi-rigid characteristic of PRSEC. Two distinctive working stages, the static friction stage and the sliding friction stage, are clearly captured in the monotonic test results. Additionally, the cyclic tests reveal that the PRSEC specimens exhibit favorable hysteretic performance, characterized by a stable load capacity, favorable deformation ability, and efficient energy dissipation capacity. The NAO friction pads exhibit a fragmented damage pattern, while the brass friction pads demonstrate a linear scratch damage pattern. No cracks or tears are observed on the surface of the bending part, which demonstrated a track-like deformation mode. Both PRSEC specimens with NAO and brass friction pads show satisfactory low-cycle fatigue performance. Furthermore, finite element analyses are conducted using Abaqus to reveal the working mechanism of the friction and bending parts. The influence of the relative parameters is also summarized based on both experimental and numerical analyses. Subsequent research would be conducted to analyze the interaction between PRSEC and precast cladding panels at the structural level to provide a reference for the design of structures employing PRSEC. • A novel point-supported rotational semi-rigid energy-dissipative connection (PRSEC) is proposed. • The semi-rigid mechanism and impact of parameters of the friction part and the bending part are analyzed and summarized. • The coordination design recommendation between the precast cladding panels and the primary structure is proposed. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of high-strength steel beams with web openings (HSSBWOs) under impact by methods of tests and finite element. Based on the experimental data of 10 specimens, which were made of high-strength steel Q550D, and the effects of impact energy and web opening forms on the impact behavior of HSSBWOs are investigated emphatically. In particular, two specimens made of steel Q235D were used to study the differences in impact behavior from HSSBWOs. The test results reveal that the high-strength steel beams with circular web openings (HSSBCWOs) have better impact resistance than the high-strength steel beams with hexagonal web openings (HSSBHWOs), and the HSSBWOs have better impact resistance than the normal-strength steel beams with web openings (NSSBWOs). Moreover, HSSBWOs has excellent abilities to absorb energy, the average energy absorption rate of HSSBHWOs and HSSBCWOs is 95.78% and 93.55%, respectively. In addition, finite element models that can accurately predict the dynamic responses of HSSBWOs under impact load are established to analyze the shear force evolutions, as well as investigate the differences of impact behavior between steel beams with a variety of web openings forms. The results show that the shear force distribution ranges of HSSBCWOs are larger than that of HSSBHWOs at the time when impact force reached peak value. The HSSBWOs can sustain more impact load with the web opening shape that closer to the circle. The solid webbed steel beam (SWSB) has better impact resistance than the steel beams with web opening (SBWO). • This study conducted drop hammer tests and finite element methods to investigate the dynamic response of Q550 high-strength steel beams with web openings (HSSBWOs) subjected to impact loads. • The effects of impact energy and the web opening form on the dynamic responses of HSSBWOs were analyzed. • A finite element model was developed to analyze the post-impact internal forces of HSSBWOs and the differences of impact behavior between steel beams with a variety of web openings forms. [ABSTRACT FROM AUTHOR]

Compared to tubular joints formed by hollow steel sections, concrete-filled steel tubular (CFST) joints exhibit more complicated failure modes and mechanism under fatigue load due to the nonlinear material confinement and the associated stress redistribution. For a reliable fatigue design of such composite tubular joints, these complexities need to be fully addressed and reasonably quantified, which necessitates an accurate approach for assessing their fatigue performance. The effective notch stress approach is widely recognized in fatigue design for its applicability and efficiency in evaluating the fatigue strength since it can rationally account for the effects of geometric configurations and welding defects on the fatigue performance. However, it has not been widely adopted in the assessment of CFST joints due to the high costs involved in modelling and computing. In this paper, a refined nonlinear finite element model is established, which facilitates the acquisition of reliable notch stress values. Subsequently, a statistical analysis is conducted on the available fatigue data of CFST joints, employing the computed notch stress to yield an S – N curve. A comparative evaluation on the results obtained from the nominal stress approach, the hot-spot stress approach and the effective notch stress approach testifies the superior accuracy of the last in assessing the fatigue strength of CFST joints. • The effective notch stress approach is employed to evaluate the fatigue performance of CFST tubular joints. • Refined FE models are established considering nonlinear material confinement and welding geometry discontinuity. • A fatigue test database is established for CFST joints to enable statistical analysis of S–N curves and scatter indices. • Effective notch stress outperforms the nominal stress and hot-spot stress approaches in prediction accuracy. [ABSTRACT FROM AUTHOR]

This paper examines the influence of perforations on the buckling instability and load-bearing capacity of advanced high-strength steel channel section (C-section) columns. Experimental tests were first conducted on 19 column specimens made of complex phrase steel HC700CP980 under axial compression, followed by finite element (FE) analysis. Two section types, the flat web C-section and the web-stiffened C-section, were considered, with perforations categorised as web-only or both web and flanges. Material tests and initial imperfection measurements were conducted and reported. Using test results, finite element models were established and parameter analysis was carried out. Analysis of test results and finite element data revealed that perforations had a noticeable impact on the buckling deformation of flat web C-sections but had a minor effect on load-bearing capacity. In contrast, web-stiffened C-sections exhibited intensified deformation post-perforation, significantly reducing their axial stiffness and load-bearing capacity. The Direct Strength Method (DSM) was assessed based on combined test and FE data. It revealed that the DSM resulted in a high level of inaccuracy and scatter in the load-bearing capacity predictions of high-strength steel C-sections after perforation. To address this, a modified method incorporating a perforation strength reduction factor was proposed, offering straightforward and intuitive calculations with improved design accuracy and consistency. • Tests and numerical analysis conducted on advanced high-strength steel channel section columns with perforations. • Influence of perforations on the buckling instability of columns examined. • Applicability of the Direct Strength Method (DSM) assessed. • Modified DSM with a perforation strength reduction factor proposed for improved design accuracy. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical investigation on the stability behaviour of cold-formed thick-walled steel tubes. Axial compression tests were conducted on 15 steel tubes with square and rectangle cross-sections to investigate their structural behaviours. The primary test parameters were slenderness and width-to-thickness ratios. Material properties, failure modes, load-deflection curves, and load-strain curves of the specimens are discussed. Furthermore, a numerical simulation was conducted to further investigate the effects of the slenderness ratio, width-to-thickness ratio, and initial geometric imperfection on the axial compression behaviour of cold-formed thick-walled tubes. Based on the experimental and numerical results, the applicability of the design codes, GB50018–2002, AISI S100–16, and EN 1993-1-1 was assessed. Results revealed that all three codes predicted the yield strength well after considering the cold-formed effect. With an increase in the slenderness ratio, GB50018–2002 and AISI S100–16 yielded increasingly unsafe predictions for overall stability, whereas EN 1993-1-1 yielded safe predictions. Finally, a modified design method for the overall buckling resistance of cold-formed thick-walled rectangular tubes under axial compression was proposed based on EN 1993-1-1 and verified using test and FEM results. • Axial compression behaviour of cold-formed thick-walled steel tubes is studied. • Cold-formed thick-walled steel tubes with square and rectangle sections were tested. • A nonlinear finite element model was developed and verified using tests results. • Eurocode 3 well predicted axial resistances of cold-formed thick-walled steel tubes. • A modified method for predicting axial overall buckling resistances was proposed. [ABSTRACT FROM AUTHOR]

This paper proposes an assembled flange core-tube column connection with self-tapping bolt (AFCS), with high assembly efficiency, low pollution and high joint. Two different core tube thicknesses were set and static low circumferential reciprocation tests were performed. It was found that the core tube thickness has a small effect on the mechanical properties, and the hysteresis curves of the two members are basically the same. The two members in the tests were torn at the foot of the column, and it was concluded that the AFCS possesses good mechanical properties and can satisfy the design criteria of "strong joint, weak member". At the same time, the self-tapping bolts performed well, and the slip did not increase after 0.03 rad, which can proof that the overall safety and reliability requirements were met. The finite element model (FEM) was established by ABAQUS, and the reliability was verified by changing the gap between the core tube and the column wall, the number and diameter of the self-tapping bolts. It was also concluded that the gap should not exceed 1/100 of the column wall width and the influence of each parameter on the mechanical properties of the connection from the largest to the smallest was the number of self-tapping bolts, the diameter of self-tapping bolts, and the gap between the core tube and the column wall. Finally, a theoretical analysis was conducted to derive the strength equations of the core tube and self-tapping bolt as well as the design method of the flange plate. • An innovative assembled steel column-column connection with self-tapping bolts (AFCS) is proposed. • The new connection utilizes both inner sleeve and flange. • Detailed experimental procedures and analysis are presented. • Accurate finite element model is created. • Reasonable theoretical analysis and formula derivation of the key parts are carried out. [ABSTRACT FROM AUTHOR]

This paper presented a numerical investigation into the dynamic responses and residual axial bearing capacity of square concrete-filled double-skin steel tube (CFDST) columns under lateral impact using ABAQUS. The finite element analysis (FEA) model for lateral impact and post-impact axial compression of square CFDST members was established, where the material nonlinearity and strain rate of steel tubes and concrete were considered and validated by existing experiments and studies. Based on the verified FEA model, the failure mechanism of the impact response process of the square CFDST member was revealed. To further explore the behavior of CFDST under axial compression after lateral impact, the typical axial load-axial displacement curves, axial strains of the steel tube, failure mode, and stress development of different components of the members were analyzed in depth. Parametric studies were conducted to clarify the influence of each parameter (including hollow ratio, slenderness ratio, concrete strength, and steel strength) on the residual capacity of post-impact axial compression in square CFDST members at different impact energies. Results demonstrated a linear correlation between residual axial bearing capacity coefficient and mid-span residual deflection after impact. Finally, a simplified formula for calculating the residual axial bearing capacity of square CFDST columns after lateral impact was proposed, which provided a reference for practical engineering applications. • The FEA model for lateral impact and post-impact axial compression of square CFDST members was established. • The dynamic behavior of impact and residual behavior after impact for square CFDST columns were analyzed. • A simplified formula to predict the strength of square CFDST columns after lateral impact was proposed. [ABSTRACT FROM AUTHOR]

The present study examined the axial resistance of welded elliptical hollow section (EHS) K-joints made of high-strength steel (HSS). The axial resistance of EHS K-joints was affected by a range of factors, including the geometrical parameters, orientations, chord pre-stress levels, and the mechanical properties of the high-strength steel grades. This research aimed to investigate the performance of welded EHS K-joints made of HSS under axial loading conditions with or without chord pre-stresses. Finite element analysis was employed for numerical simulations to analyze the nonlinear behaviour of EHS K-joints with HSS. It was observed from the numerical results that the orientation types significantly affected normalised resistance ratios. In contrast, β , γ , θ, and chord pre-stress levels had minimal impact, as comparisons were based on normalised resistance ratios. However, non-dimensional geometric parameters and chord pre-stress levels notably influenced the axial joint resistance of the HSS K-joints. As for predicting the axial resistances of EHS K-joints with HSS, the numerical results indicated that the existing reduction factor might be unsafe for the equivalent RHS method to be applied in the current design guides. Therefore, a new reduction factor was proposed for EHS K-joints with HSS that yield unsafe results. • This paper presents a numerical study completed on axial resistance of EHS K-joints made of HSS. • A range of geometrical parameters and chord pre-stress levels were examined. • The orientation types significantly affected the behaviour of EHS K-joint with HSS. • The β , γ , θ and chord pre-stress levels had minimal impact on the joint normalised joint resistance. • A new design method is proposed to predict the capacity of the EHSK-joints with HSS. [ABSTRACT FROM AUTHOR]

A refined finite element model of corroded seven-wire steel strand was established based on finite element software. It was then compared and validated against the experimental results, demonstrating the accurate prediction capability of the model for variations in actual loads. To better capture the influence of corrosion on axial load bearing capacity of steel strands, an analysis was conducted using a relationship between axial load reduction coefficient θ and mass loss rate χ. Furthermore, this study investigates the effects of residual diameter d c /d , geometric parameters, and yield strength on the axial load reduction coefficient of steel strands. The research findings indicate that while there is a correlation between axial load reduction coefficient and residual diameter, no significant relationship exists with geometric parameters or yield strength. Based on extensive random finite element analysis, a predictive formula for lower limits of θ-χ curves for corroded steel strands at different levels of corrosion is proposed. By measuring the mass loss rate of steel strands, it becomes possible to more effectively predict their minimum axial load-bearing capacity and ensure operational safety under corrosive conditions. • This paper proposes a new numerical model for corrosion damage in steel strands. • The factors affecting the axial bearing capacity reduction coefficient (θ) of corroded steel strand are revealed. • A lower limit prediction formula for θ-χ curve applicable to different degrees of corrosion of steel strands is proposed. [ABSTRACT FROM AUTHOR]

Cross-shaped concrete-filled steel tube (CFST) can avoid the structural column protruding from walls and save the room space, but the steel tube is prone to local buckling under compression. The use of stiffeners and multi-cell form can effectively improve its mechanical performance. However, limited research studies were conducted on these column forms previously. In this paper, six stub columns were tested under axial compression varying the parameters of cross-section form and concrete strength grade. The failure pattern, ultimate strength, load-strain curve, compressive stiffness and ductility were obtained. The test results show that using longitudinal stiffeners or multi-cell form can improve the axial compressive strength, stiffness and ductility of cross-shaped CFST, and the mechanical performance of multi-cell form is superior. The axial compressive strength of stiffened and multi-cell columns can be enhanced by 4.9%–25.2% and 21.8%–28.4%, respectively, compared with unstiffened columns. The corresponding stiffness can be increased by 14.2%–27.4% and 25.2%–43.2%, respectively, and the corresponding ductility can be increased by about 9% and 120%, respectively. Finite element (FE) models were established for the cross-shaped CFST stub columns and the FE simulation results were in good agreement with the experimental results. 134 stiffened and 134 multi-cell stub column models with different parameters were calculated, and the design methods were suggested for axial compressive strength and stiffness of stiffened and multi-cell cross-shaped CFST stub columns. • Six cross-shaped CFST stub columns were tested under axial compression. • Using stiffeners or multi-cell form can improve ultimate strength, stiffness and ductility. • Finite element models of cross-shaped CFST stub columns were established. • Design methods for stiffened and multi-cell cross-shaped CFST columns were suggested. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of dampers on the seismic performance of steel frames with unequal depth beam-column (UDBC) joints. First of all, the finite element (FE) models of the UDBC joint and steel frame were regenerated by ABAQUS and verified by experimental results. Secondly, the design method for three H-shaped dampers with different web perforation forms (vertical, elliptical, and diamond) was provided. Finally, five steel frames were built using ABAQUS, and pushover analysis and dynamic time-history analysis were performed on them. The results indicated that dampers could decrease the maximum vertex displacement and inter-story shift angle of steel frames with UDBC joints under three seismic waves by 4.47% to 17.17% and 7.71% to 23.88%. The effect of H-shaped dampers was similar to that of T-shaped connectors. Under the action of the Kobe wave and the Qian'an wave, the H-shaped damper exhibited more excellent seismic performance. Compared with frames with T-shaped connectors, the maximum vertex displacement and the maximum inter-story shift angle of frames with H-shaped dampers decreased by 3.44% to 12.39% and 9.55% to 16.15%. The web perforation form of H-shaped dampers somewhat affected the seismic behavior of steel frame structures. Among them, diamond dampers could minimize structural deformation. • The accuracy of the finite element model of the UDBC joint framework is verified. • Pushover analysis is conducted on the UDBC joint frame model. • Dynamic time-history analysis is conducted on the UDBC joint frame model. [ABSTRACT FROM AUTHOR]

This paper investigates the impact resistance and damage mechanism of steel reinforced concrete columns under lateral impact loading using experimental and numerical studies. First, six specimens were subjected to impact testing utilizing a horizontal lateral impact test device. Then, the effects of impact velocity, boundary condition, and impact direction on the impact response of specimens were investigated. The damage development, final damage pattern, impact force-time history, lateral displacement, and concrete strain were obtained to figure out the damage mechanism of steel reinforced concrete columns. The test results show that all specimens exhibit brittle shear damage patterns. As the impact velocity increases, the local brittle shear damage becomes more pronounced. Following experimental investigation, a finite element model was established and validated against the experimental results. The distribution of impact energy among different components and the effect of axial load on the impact resistance of specimens were obtained using finite element models. It was found that concrete dissipates the most energy among different components. However, the percentage of energy dissipated by the profiled steel increases with the increase in impact velocity, meaning that the insertion of profiled steel into concrete elements can effectively enhance the impact resistance of the structure. It was also found that the steel reinforced concrete column is more prone to local shear damage in a large range of axial load. • The impact resistance and damage mechanism of SRC columns were investigated. • The effect of impact velocity, boundary condition, and impact direction was investigated. • The shear force at the base of the SRC column was calculated. • An FE model was established and validated against the experimental results. • This study can be used to optimize design of SRC columns for sustaining the safety in collision. [ABSTRACT FROM AUTHOR]