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This paper comprehensively discusses the seismic performance of steel moment-resisting frames with hybrid-self-centring connections (SMRF-HSCC) employing energy dissipation sequences by probabilistic seismic assessment. The hysteretic model of the HSCC was first developed based on experimental results, and a simplified nonlinear-spring-based model to simulate the behaviour of the connection was proposed and verified by physical test data. A series of codified prototype structures were developed, considering the fracture behaviour of post-tensioned (PT) steel strands in the connections. The seismic performance of prototype structures was assessed in terms of nonlinear static analyses and nonlinear dynamic analyses. The results indicated that the hysteretic response of SMRF-HSCC exhibited trilinear hysteretic features with the expected energy dissipation sequences. The influence of the high-mode effects on SMRF-HSCC was mitigated with the increase in energy dissipation and post-yield stiffness of the structure. Finally, the fragility analyses of the prototype structures were further performed, and the risk assessment was also made considering a 50-year service period. The collapse probability and the exceedance probability of target residual drift over a 50-year service period of SMRF with conventional self-centring connections showing flag-shaped hysteresis were higher than that of SMRF-HSCCs. The results also confirmed that the collapse probability and exceedance probability of target residual drift over a 50-year service period of SMRF-HSCC can be adjusted by reasonably modulating the arrangement of the HSCCs. • Hybrid-self-centring connection (HSCC) was proposed. • The trilinear hysteretic model of the HSCC was developed. • Probabilistic seismic assessment of SMRF equipped with HSCCs was performed. [ABSTRACT FROM AUTHOR]

• A demand index quantifying the residual deformation ratio is defined. • Near-fault ground motions are applied as input excitations. • Effects of the damage-control core and its shifting path are studied. • Empirical formulas of residual displacement ratio demand are developed. This research investigates the post-earthquake residual displacement ratio demand of high strength steel frames with energy dissipation bays (HSSF-EDBs) under near-fault earthquake ground motions. The study focuses on the ultimate stage of the structure where the HSS frame develops sufficient inelastic deformations. The nonlinear force-displacement behaviour of a HSSF-EDB is idealised by a classical trilinear kinematic model, and the idealised hysteretic behaviour is assigned to oscillators for representing the novel system. To facilitate performance-based seismic design of HSSF-EDBs, the post-earthquake residual displacement demand is related to the yield displacement characterising yielding of energy dissipation bays using the trilinear oscillator analogy, and a non-dimensional residual displacement ratio is proposed. A large number of inelastic spectral analyses of trilinear oscillators covering a reasonable spectrum of hysteretic parameters are performed to quantify the influence of the essential variables on the residual displacement ratio demand of the systems. The results show that the residual displacement ratio of trilinear oscillators representing HSSF-EDBs subjected to near-fault earthquake ground motions is affected by hysteretic parameters in various yielding stages. To offer a practical tool for estimating the residual displacement demand of HSSF-EDBs in the preliminary design phase, empirical formulas quantifying the post-earthquake residual displacement ratio demand of trilinear oscillators are proposed. Finally, the effectiveness of using trilinear oscillators for quantifying post-earthquake residual displacement demand of HSSF-EDBs is emphasised by a comparative study on seismic responses of a prototype HSSF-EDB system and equivalent oscillators under near-fault ground motion samples. [ABSTRACT FROM AUTHOR]

Highlights • Steel MRFs equipped with steel slit walls may show multi-yielding stages. • A multi-stage-based nonlinear static procedure is proposed. • The applicability of the current nonlinear static procedure is examined. • The proposed method offers a practical tool for modulation of seismic energy balance. Abstract This paper aims to develop a nonlinear static procedure for estimating seismic demands of steel moment resisting frames (MRFs) equipped with steel slit walls (SSWs) exhibiting multi-yielding stages under seismic actions. The hysteretic behaviour of a steel MRF equipped with SSWs was examined. Numerical models were also developed and verified by revisiting a previous full-scale test programme. The applicability of a classical trilinear kinematic model for idealising the hysteretic response of the systems was examined. Then, a multi-stage-based nonlinear static procedure (MNSP) governed by the energy-balance concept was proposed, which enables practitioners to quantify the seismic demands of a steel MRFs equipped with SSWs showing multi-yielding stages. The MNSP was subsequently applied to two prototype steel MRFs equipped with SSWs under design basis earthquakes and maximum considered earthquakes. The predictions by the MNSP were compared with nonlinear response history analysis (NL-RHA) to examine the effectiveness of the method. The lateral load distributions documented in FEMA-356 were also included in the work for comparison. The observations from this study suggests that the proposed MNSP offers a promising tool for estimating the peak seismic response of steel MRFs equipped with SSWs showing multi-yielding stages. [ABSTRACT FROM AUTHOR]

Self-centering beam-to-column connections (SBCs) were widely investigated to enhance conventional steel moment-resisting frame's (MRF's) post-earthquake repairability by reducing residual displacements. The peak displacement-targeted design methodology was adopted to develop the design guidelines for enhancing MRFs with the emerging self-centering members, where the desired post-earthquake repairability of the enhanced MRF needs to be achieved with inevitable iterative dynamic analyses. This paper intends to develop a novel post-earthquake repairability-based methodology for enhancing MRFs with SBCs, where residual and peak displacements are both targets. To this end, artificial neural network (ANN) models were developed to estimate the peak and residual displacements of the enhanced MRFs with SBCs under given seismic intensities. Peak and residual displacement-based design (PRBD) procedures were developed based on the proposed post-earthquake repairability-based methodology and established ANN models. Four design cases were designed through the developed PRBD procedure and analyzed. The design and analysis outcomes demonstrate that the improved MRFs can attain the intended post-earthquake repairability and meet the peak and residual displacement objectives without necessitating iterative design and dynamic analyses. This confirms the effectiveness and precision of the proposed post-earthquake repairability-based approach and PRBD procedure. Moreover, the enhanced MRFs with partially self-centering behavior achieved nearly zero residual displacements (lower than 0.2%) under maximum considered earthquakes. This finding shows that the partially self-centering MRF is a more cost-efficient solution for developing seismic resilient MRF than fully self-centering MRF to achieve excellent post-earthquake repairability with a lower requirement of self-centering capacities. • Post-earthquake repairability-based design methodology was proposed. • PRBD procedures were developed for enhancing MRFs with SBCs. • The enhanced MRFs can achieve the desired post-earthquake repairability without iterative design and dynamic analyses. • The enhanced MRFs with partially self-centering behavior can achieve nearly zero residual displacements under MCE. [ABSTRACT FROM AUTHOR]

• The hysteretic behaviour of shape memory alloy (SMA) plates with superelastic effect under cyclic tension–compression loading was investigated. • We designed and tested 33 SMA plates with buckling-restrained devices to examine the mechanical properties of SMA plates subjected to cyclic tension–compression loading. • The test parameters are the specimen thickness, loading protocols, and test temperatures. • The failure mode, stress–strain responses, strength, and self-centring capability of the specimens were analysed and discussed. Shape memory alloys (SMAs) have garnered significant attention for their potential in earthquake-resistant structures, primarily due to their superelastic effect and exceptional self-centring capabilities. However, the mechanical properties of SMA plates, especially under cyclic tension–compression loading, remain underexplored. This research aims to bridge this gap by designing and testing 33 SMA plates equipped with buckling-restrained devices. The study varied parameters such as specimen thickness (4 mm, 6 mm, and 8 mm), loading protocols (seven in total), and test temperatures (25 °C and 0 °C). The findings reveal that the stress–strain curves under cyclic tension–compression loading exhibited asymmetric characteristics. For instance, at 25℃, a 4 mm thick specimen at 4% strain had a compressive peak stress that was 22.2% higher than its tensile counterpart, and its compressive residual strain exceeded the tensile residual strain by 99.0%. Furthermore, when compared to SMA plates under cyclic tension-release loading, those under cyclic tension–compression loading had reduced tensile residual strains. At 0 °C, the peak stress saw a decrease ranging from 2.4 to 43.1%, while the residual strain surged by 11.9–591.4% compared to the tests at 25℃. This study provides novel insights into the behavior of SMA plates under varied conditions, emphasizing their potential for seismic applications. [ABSTRACT FROM AUTHOR]

• The hysteretic response curves of the fuse connections subjected to cyclic loading were plump. • The fuse angles can concentrate the inelasticity effectively in a wide deformation range. • The retest with replaced angles exhibited a similar performance to the initial test. • The fuse connection achieved an initial stiffness close to that of a typical welded beam-to-column connection. In this study, an innovative replaceable fuse connection for beam members in moment resisting steel frames was proposed. Steel angles are designed as fuse elements for energy dissipation and post-earthquake replacement. The load carrying mechanism of the connection was explored. In order to examine the feasibility of the notion, a total of six full-scale subassemblies of beam-to-column connections were tested. The test parameters that affect the performance of the fuse connection were studied, and the repairability was validated by a retest specimen with replaced fuse angles. Test results demonstrated that the hysteretic response curves of the test connections subjected to cyclic loading were plump, and the fuse angles can concentrate the inelasticity effectively in a wide deformation range. The novel connections equipped with fuse angles can achieve an initial elastic stiffness close to that of a conventional welded beam-to-column connection. In addition, theoretical equations for predicting the elastic stiffness and resistance of the connection were developed, and their sufficiency was validated by test results. [ABSTRACT FROM AUTHOR]

Duplex stainless steel (DSS) is an emerging construction material for structural engineering, which is featured with high mechanical strength and superior corrosion resistance. Compared with considerable research on DSS structural members, available research is relatively limited for structural joints/connections between these members. In line with this concern, this paper presents a comprehensive experimental and numerical study of duplex stainless steel bolted connections (DSSBCs), focusing on the behaviour and design related to block shear failure. Eleven specimens are tested to investigate the effect of different bolt arrangements on the block shear behaviour. Furthermore, a detailed numerical study was performed as a supplement to the experimental tests, where the anisotropic mechanical properties of DSS are considered in the finite element modelling. Based on the test and analysis results, it is found that the block shear failure mode of DSSBCs resembles that of carbon steel bolted connections, which can be characterised as necking of the tensile section and yielding of the shear sections. Using the experimental and numerical data obtained in this and previous studies, the applicability of various block shear design methods to stainless steel bolted connections is assessed. An updated design method is proposed for predicting the block shear capacity of duplex and austenitic stainless steel bolted connections. A proper partial safety factor/resistance factor is suggested for the proposed method based on the results of reliability analyses. • Block shear of duplex stainless steel bolted connections (DSSBCs) are studied. • DSSBCs exhibit similar block shear mode to carbon steel bolted connections. • Existing design methods are evaluated for stainless steel bolted connections. • A modified method is proposed for stainless steel bolted connections. • A reliability analysis is performed to provide suggestion of partial factor. [ABSTRACT FROM AUTHOR]

• The novel structure showing the partially self-centring behaviour was proposed. • A spectral energy factor model for the system was developed based on the lognormal distribution assumption. • The sufficiency of the energy factor model was justified. To achieve a delicate balance between self-centring behaviour and energy dissipation, it was proposed to develop the damage-control steel frame equipped with shape memory alloy (SMA) connections and ductile links showing the partially self-centring behaviour. This paper examined the inelastic seismic demand of the novel structure, and the emphasis was given to the spectral energy factor of the system subjected to near-field earthquake motions. Based on single-degree-of-freedom (SDF) systems representing the novel structure and a near-field earthquake database, nonlinear spectral analyses were performed considering a wide range of structural period and hysteretic parameters, and more than 25 million energy factors were obtained. The probabilistic characteristics of the energy factors were examined in detail. The analysis database confirmed that the energy factors were sensitive to structural period and hysteretic parameters. In addition, a right-skewed distribution feature of the energy factors was observed. Thus, a spectral energy factor model for damage-control steel frames equipped with SMA connections and ductile links was developed using the lognormal distribution model. Nonlinear regression analyses were conducted to develop a series of prediction equations. The good agreement between the histograms of the energy factor and predictions by the regression equations confirmed the adequacy of the proposed model. The proposed model was eventually applied to evaluating the damage-control behaviour of a prototype structure under near-field earthquake motions, and the sufficiency of the model for assessing the structural damage-control behaviour from a statistic perspective was confirmed. [ABSTRACT FROM AUTHOR]

• The life-cycle benefits of full self-centering structures (FSCSs) and partial self-centering structures (PSCSs) were comprehensively investigated. • Compared to the FSCS, the PSCS can achieve better performance in controlling PFAs, lowering base shear demands with comparable performance in controlling RIDs. • The PSCS can achieve better life-cycle benefits than the FSCS. • The life-cycle costs of FSCS and PSCS are highly influenced by the initial costs of self-centering braces. • It is critical to reduce the initial costs of self-centering structural members and control the floor acceleration responses for increasing the life-cycle benefits of self-centering structures. Various self-centering structural systems were developed and investigated for reducing residual inter-story drifts of the traditional aseismic structural system by achieving full or partial self-centering behaviors under earthquakes in the past twenty years. However, limited research was conducted to investigate the life-cycle benefits of the full and partial self-centering structural systems on the life-cycle span, figuring out a more cost-effective solution for enhancing the building's seismic resilience. This paper aims to comprehensively investigate the life-cycle benefits of full and partial self-centering structural systems compared to conventional buckling-restrained braced frames (BRBFs) using the life-cycle cost estimation method. The influences of the residual inter-story drift limit for demolition, the initial cost of emerging self-centering members, the value of building contents, and the discount rate were particularly investigated. To this end, three building structures with BRBFs and full and partial self-centering structural systems were designed to achieve the same capacity for controlling maximum inter-story drifts. Comprehensive dynamic analyses were performed to generate engineering parameters under different seismic intensities and the modeling uncertainties were properly considered through Monte Carlo simulation. The revised HAZUS loss calculation method was adopted to investigate the seismic annual loss (SAL) and life-cycle cost. The analysis results indicate that the partial self-centering behavior would be a better choice than the full self-centering behavior for developing the self-centering structural systems to achieve better life-cycle benefits. Moreover, it is essential and urgent to reduce the initial costs of self-centering structural members and control the floor acceleration responses for increasing the life-cycle benefits of self-centering structural systems and promoting their practical applications. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive numerical study on the strength and behaviour of double-coped beams (DCBs), with the focus on reinforcing strategies against local web buckling. Four reinforcement types, namely, longitudinal web stiffener (Type A), combined longitudinal and vertical web stiffeners (Type B), vertical and double longitudinal web stiffeners (Type C), and full-depth doubler plate (Type D), are considered. Through examining a suite of validated numerical models with a spectrum of cope details, it is found that the considered reinforcement types are in general effective, especially for the models with long or deep copes. Depending on the cope details and stiffener type, a series of failure modes, including local web buckling, web shear yielding, web shear buckling, tensile fracture of the bottom cope corner, and web crippling, are identified, and the effectiveness of the different reinforcement types on preventing or postponing these failure modes is discussed in detail. A preliminary design rule for checking the capacity of the reinforced coped section is also proposed in the paper, and additional analysis is performed to further evaluate the influences of varying reinforcement dimensions and boundary conditions on the ultimate capacity of the DCBs. Based on the numerical analysis, a set of prescriptive recommendations on reinforcement details is finally proposed, offering a simple yet safe guidance for new design or upgrade of DCB members. [ABSTRACT FROM AUTHOR]

• 33 high strength steel and 15 mild steel staggered bolted connections were tested. • The effects of steel grades and connection configuration were investigated. • Test observations were further illustrated by finite element analysis. • The accuracy of the s 2/4 g rule was re-examined. • Current design equation in EN 1993–1-12 was re-evaluated by statistical evaluation. This paper investigates the structural behaviour and ultimate strength of high strength steel (HSS) staggered bolted connections under tension. A total of 33 HSS (Q690 and Q960) and 15 Q345 staggered bolted connection specimens were tested. All specimens failed in net section fracture through the staggered path. The predicted net section resistance based on the s 2/4 g rule was achieved by most of the HSS specimens. For the specimens with a small bolt pitch to gauge (s/g) ratio, the connection efficiency (i.e., the ratio between the test ultimate load and the calculated net section resistance) exceeded 1.0 and decreased gradually with an increasing s/g ratio. Compared with the mild steel (MS) specimens, in general the HSS specimens have lower connection efficiency and overall deformation capability. Subsequently, the structural behaviour of the test specimens was investigated using finite element (FE) analysis to further interpret the test observations. The results of the test and the FE analysis indicated that for the HSS specimens, effective stress redistribution along the staggered net section was observed although the ductility and the ratio of tensile strength to yield strength (f u /f y) of HSS material are relatively lower than those of the MS material. In addition, it was also observed that the biaxial state of stress that existed in the plate area between the staggered bolt holes was influenced by the s/g ratio, which would affect the ultimate strength of the test specimens. A reliability analysis of the HSS specimens test results was carried out to re-evaluate the partial factor adopted in the design equation of the net section resistance of HSS (up to S700) in EN 1993-1-12. The analysis results of the limited test data showed that the net section resistance of HSS staggered bolted connections was predicted conservatively by the current design equation with a partial factor of 1.25. [ABSTRACT FROM AUTHOR]