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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]

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

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

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

The 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]

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

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

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

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

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

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

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

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

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

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

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

To promote the analysis/design of high-strength steel (HSS) Q690E/Q960E structures, this paper firstly developed stress-strain (σ-ε) constitutive models of HSS Q690E/Q960E at different low temperatures (T) of −80, −60, −30, and 20 °C. The prediction equations on key parameters in the σ-ε constitutive models (e.g., yield/ultimate/fracture strength and their corresponding strains, and elastic modulus) of HSS Q690E/Q960E at varying low temperatures were developed. Validations against 39 test results confirmed that proposed constitutive models offered reasonable estimations on the low-temperature σ-ε constitutive models of HSS Q690E/Q960E. Finite element models (FEMs) with the continuum damage plasticity model (CDPM) and proposed σ-ε models were developed for HSS Q690E/Q960E materials at ambient/low temperatures. Validations of FEM simulations against 39 tensile tests on HSS coupons proved that the FEMs with CDPM predict well σ-ε behaviours of HSS Q690E/Q960E at −80–20 °C. This paper also developed FEMs with CDPM to simulate the low-temperature compression behaviour of HSS Q690E/Q960E tubular columns. Validations against six compression tests confirmed that the FEMs with the CDPM and proposed σ-ε constitutive models were capable of simulating the HSS Q690E/Q960E structural members. • Stress-strain (σ-ε) constitutive models of HSS Q690E and Q960E at low temperatures (T) are developed. • FEMs with proposed σ-ε models are developed for HSS Q690E and Q960E materials at low temperatures. • FEMs with CDPM predict well σ-ε behaviours of HSS Q690E and Q960E at −80–20 °C. • FEMs with the CDPM and proposed σ-ε constitutive models predict well behaviours of HSS Q690E and Q960E structural members. [ABSTRACT FROM AUTHOR]

Concrete-filled double skin steel tubular columns with large hollow ratio (LHR-CFDST) have been commonly used in recent years. With the increasing size of the engineering structures, one efficient way to decrease the consumption of steel is to increase the diameter-to-thickness ratio. Few studies have been conducted to report on thin-walled LHR-CFDST columns. At the same time, local buckling may occur in these structures in the absence of stiffening measures. Based on this, an experimental and numerical analysis was carried out for the stiffened thin-walled LHR-CFDST columns under axial compression in this paper. Five thin-walled LHR-CFDST columns with different stiffening measures (ribs, studs) were tested. The failure modes, load versus shortening curves, local buckling behaviours and ductility were investigated. The test results indicates that the stiffened measures effectively delayed the appearance of local buckling and increased the peak load. Besides, the finite element models validated by the test results were applied to the subsequent mechanical mechanism analysis of the stiffened thin-walled LHR-CFDST. It can be seen that the stiffened measures enhance the confinement of the inner and outer steel tubes on the concrete and greatly improve the ultimate strength of the concrete. Finally, the predicted peak load formulae in the existing design specifications were modified by combining the characteristics of the specimens in this paper. The peak load values obtained by the improved formulae agreed well with the test results. • Five thin-walled CFDST columns with different stiffening forms (ribs, studs) were tested under axial compression. • The effects of stiffeners on the local buckling and peak load of specimens were revealed. • The validated finite element model was developed to further analyze the structural mechanisms. • The interaction between steel tubes and concrete were investigated. • The predicted peak load formulae in the existing design specifications were modified. [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]

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]

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 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]

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]

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]

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]

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]

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

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

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

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

Abstract This paper reports a detailed numerical (FE) study on planar stainless steel beam-to-column joints. A nonlinear FE model is developed and validated against the first set on full-scale tests on stainless steel beam-to-column joints reported in the companion paper. The FE model is shown to accurately replicate the experimentally determined, initial stiffness, ultimate resistance, overall moment-rotation response and observed failure modes. Parametric studies are conducted to obtain the moment-rotation characteristics of a wide range of beam-to-column joints classified as semi-rigid and/or partial strength. Due to the low ductility of the bolts compared to the high ductility exhibited by all other stainless steel joint components, in all cases the strength and ductility of the simulated joints is limited by the failure of the connecting bolts. The design rules for stainless steel connections, which are based on the specifications of EN 1993-1-8 for carbon steel joints, are reviewed and are found to be overly conservative in terms of strength and inaccurate in terms of stiffness thus necessitating the development of novel design guidance in line with the observed structural response. These conclusions are in agreement with the ones reported in the companion paper. Highlights • The papers reports a comprehensive FE study on stainless steel beam-to-column joints • Modelled joints possess excellent rotation capacity and significant over strength • Current design standards do not accurately predict the observed failure mode • Current design standards are assessed and found overly conservative in the strength prediction of stainless steel joints • The development of new design rules in accordance with the observed response is warranted [ABSTRACT FROM AUTHOR]

Arched beams with cellular openings (referred to here as arched cellular beams) are used as roof beams with several practical advantages and architectural-appearance requirements. This paper presents a discussion regarding the performance of arched cellular beams. An experimental program comprising four full-scale specimens was performed. The perforated cellular arched I-sections with hinged-hinged supports under a mid-span vertical concentrated load were tested. Manufacturing, material properties, boundary conditions, and the test setup are discussed in detail in this paper. The experimental investigation was carried out to study the effects of cellular web openings, subtended angles, and radii of curvature. The failure modes and key parameters were investigated. The web buckling resistance of the experimental specimens was calculated using two models from the literature. The analytical model for straight cellular beams proposed by Lawson et al. [1] yielded feasible conservative values for the critical buckling resistance of web posts for arched cellular beams. Finally, a finite element (FE) model is proposed to analyse the behaviour of arched cellular beams. It was validated by experimental results. The FE model accurately predicted the ultimate loads, the critical buckling loads and the failure modes of the tested specimens. It can be used for similar future studies. [ABSTRACT FROM AUTHOR]

An experimental and numerical study of hot-rolled steel I-sections under combined compression and bending moment is presented herein. A total of two stub column tests and 12 mono-axial or bi-axial eccentric compression tests on HEB 160 cross-sections with two different material grades (S235 and S355) were carried out. The tested cross-sections were of stocky proportions to enable the influence of material strain hardening on the strength and behaviour of hot-rolled steel I-sections to be investigated. The loading eccentricities for the eccentric compression tests were varied in order to achieve different axial compression-to-bending moment ratios. Measured geometric and material properties, together with the full load-deformation histories from the test specimens, were reported. Finite element (FE) models were developed and validated against the experimentally obtained load-deformation curves, as well as the failure modes. The FE results successfully captured the experimental structural performance of hot-rolled steel I-sections and the validated FE models were then used for parametric studies in the companion paper to generate additional numerical results, considering different cross-section slendernesses, material grades and combinations of loading. The experimental and numerical results are employed in the companion paper for the assessment of the design rules given in EN 1993-1-1 (2005) and AISC-360-16 (2016) and for the extension of the deformation-based continuous strength method to the case of hot-rolled steel I-sections under combined loading. [ABSTRACT FROM AUTHOR]

In this paper, a simple design equation to predict the resisting capacity of circular CFT columns is introduced, and the accompanying design procedure entails two phases: construction of the linearized P-M interaction diagram for a circular CFT column section and its adjustment according to the slenderness ratio. To construct the linearized P-M interaction diagram of circular CFT columns without a rigorous nonlinear analysis, simple equations are proposed in this paper. In advance, on the basis of the numerical results obtained by the use of the analytical model introduced in the previous paper, the ultimate resisting capacity reduction factors are designed through a curvilinear regression, and the use of these reduction factors makes it possible to determine the ultimate resisting capacity of slender CFT columns without any rigorous nonlinear analysis. Finally, the efficiency of the introduced design equation is verified on the basis of the comparison of the ultimate resisting capacities calculated in this paper with those determined by rigorous nonlinear analyses and by the AISC design guideline and the Eurocode. [ABSTRACT FROM AUTHOR]

This paper proposes the web angle connection joint and carries out the relevant theoretical derivation, finds out the design method and the bearing capacity calculation method. The calculation results are verified by simulation results. Finally, the advantages of the web angle connection joint are verified by comparing with the common joint. The results show that the thickness of damage element should not exceed 1.3 t flang in the joint design; Through the analysis of the bearing capacity and energy consumption, it is found that the error between the calculated and simulation results about bearing capacity is within 5%; The development law of the energy consumption of each part is consistent with the theoretical calculation, which reveals the validity of the joint design theory; Through parameter analysis, it is found that under the premise of considering steel damage, the spacing of intermediate bolts will significantly affect the cyclic loading times of joints. In consideration of recoverability, bearing and energy dissipation performance and steel damage, it is recommended that the thickness of flange connecting plate is 1.2t flange , and the spacing between intermediate bolts is 21.5t cov, f. Compared with ordinary earthquake-resilient joints, it is found that the bearing capacity of web angle connection joints can be increased by 50.3%, the energy dissipation capacity can be increased by 35.8%, and it's plastic development of damage elements is more uniform, which is conducive to the replacement after earthquake. The proposed joint in this paper can provide reference for the development of earthquake resilient structures. • First, The damage control theory and design method of high strength steel earthquake-resilient joints are proposed. • Secondly, A method for calculating the bearing capacity of web angle connection joint is proposed, and the validity of the method is verified by the theoretical calculation and the finite element modelling • Thirdly, The joint analysis method considering the damage of flange connecting plate is proposed, and the design suggestions are given aim at joint with and without damage. • Fourth, Excellent load bearing and energy dissipation performance are verified by comparing it with the ordinary earthquake resilient joint. [ABSTRACT FROM AUTHOR]

The fatigue problem of two in-plane cracks in rib-to-deck welded toe of orthotropic steel bridge decks is an important issue. Traditionally, related work focuses on single-crack propagation in these joints; however, many practical observations have shown that the initial weld cracks of structures are characterized by multiple cracks in a small range. Thus, the main goal of this paper is to investigate the mechanism of and guidelines for in-plane double-crack propagation in rib-to-deck welded toe of orthotropic steel bridge decks. In this paper, the rib-to-deck welded toes in the orthotropic steel deck of the Anqing Yangtze River Bridge are taken as the background. Based on extended finite element method theory, single-crack propagation theory and the multiple-crack coalescence law, the stress intensity factors at the crack tip are calculated by the interaction integral method, and the propagation directions are determined using the maximum energy release rate (Merr) criterion. The whole process of in-plane double-crack propagation, coalescence and failure in rib-to-deck welded toe of long-span steel bridge decks and their fatigue life are simulated according to the principle of an equivalent crack front. Meanwhile, the most unfavorable conditions of cracking parameters are determined by changing the spacing and shape ratio of the two cracks. Then, the fatigue loading experiment is carried out on equal proportion specimens under appropriate cracking parameters. The results reveal the whole process of in-plane double-crack propagation in rib-to-deck welded toe of orthotropic steel bridge decks, and the verification shows that experimental results agree well with the simulation results. [Display omitted] • Focusing on initial multiple cracks in the welded toes small range. • Using multiscale FEM models and XFEM model to simulate the process of crack propagation and coalescence. • Finding out the law of in-plane double-crack propagation and coalescence. • Experimental verification of the in-plane propagation and coalescence of two fatigue cracks in OBDs. [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]