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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]

This paper investigates the inelastic seismic demands of steel frames equipped with shape memory alloys (SMAs) subjected to mainshock-aftershock earthquake sequences. Based on the multiple nonlinear stages of steel frames equipped with SMAs, a trilinear self-centring hysteretic model is introduced and validated first. Then, inelastic spectral analyses of steel frames equipped with SMAs subjected to mainshock-aftershock earthquake sequences are conducted. In particular, the energy modification factors of the corresponding single-degree-of-freedom (SDOF) under single mainshocks and mainshock-aftershock earthquake sequences are examined and compared. The results show that the energy modification factor of steel frames equipped with SMAs under mainshock-aftershock earthquake sequences is higher than that under single mainshocks, and the energy modification factor shows sensitivity to trilinear self-centring hysteretic parameters. Last, an amplification coefficient is developed and estimated for quantifying the amplification effect of recorded mainshock-aftershock earthquake sequences on the energy modification factor. Specifically, several machine learning (ML) algorithms are implemented and compared for estimation and interpretation. The results indicate that the XGBoost model performs best in predicting the amplification coefficient with the highest coefficient of determination of 0.9845. Besides, the interpretable ML approaches including partial dependence plot (PDP) and shapely additive explanations (SHAP) are proved helpful in explaining the trained ML model. • A trilinear hysteretic model is proposed and verified. • Effects of the influential parameters on energy modification factors are investigated. • Amplification effect of mainshock-aftershock earthquake sequences is quantified. • Prediction model for amplification effect is developed utilising machine learning technologies. • Interpretable machine learning approaches are adopted. [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]

Abstract This work focuses on the seismic performance of high-strength-steel frame equipped with mild-carbon-steel sacrificial beams of non-compact sections in energy dissipation bays, namely the HSSF-NCEDB structure. This work was commenced with a test program of a HSSF-NCEDB system as a feasibility study. The test results indicate that the novel structure exhibits the desirable damage-control behavior with inelastic actions locked in the sacrificial beams with non-compact sections for the expected deformation range. Even though both high-strength-steel members and sacrificial beams with non-compact sections were restricted by the limited energy dissipation, ductile manner was observed. A finite element (FE) model was established, and good agreement between the test results and the FE results was obtained. For practical applications, the concept of the buckling hinge was developed for quantifying the stable energy dissipation stage of sacrificial beams with non-compact sections. Lastly, the effectiveness of the HSSF-NCEDB system for mitigating the post-earthquake residual deformations was demonstrated by preliminary nonlinear dynamic analyses of single-degree-of-freedom oscillators with validated hysteretic models. The research findings from this work indicate that the HSSF-NCEDB structure is a promising option for structures in low-to-moderate seismic regions. Highlights • The concept of HSSF-NCEDB structure is proposed. • HSS frame is equipped with sacrificial links with non-compact sections. • A buckling-hinge model is proposed. • The potential of the structure for residual deformation mitigation is verified. [ABSTRACT FROM AUTHOR]

In current composite floors, the strength of the deck connections restraining the profiled steel decks to the floor beams or to the neighboring steel decks are much weaker compared with the sectional strength of the steel deck, which would limit the load-carrying capacity of the composite floors under progressive collapse scenarios. Given this, this study proposed two novel types of enhanced deck connections for improving the load-carrying behavior of the deck-to-beam connection and deck-to-deck connection. Based on a 5-story steel prototype building, the feasibility of the proposed deck connections in improving the progressive collapse resistance was validated by comparing with the common practice of the deck connections via a reduced-order (RO) modeling approach. The structural robustness of the prototype building in the case of sudden column removal was evaluated and discussed. Compared with the commonly used deck connections, the enhanced deck connections could improve the structural robustness of the prototype building by 27%. • Novel enhanced profiled deck connections are proposed. • The structural configurations are designed using high-fidelity analysis results. • Verified reduced-order models are developed. • Enhanced deck connections can improve the structural robustness of steel frame building. [ABSTRACT FROM AUTHOR]

An innovative self-centring damper equipped with shape memory alloy elements and wedge-shaped friction plates (i.e. SMA-VFSD) characterised by multiple energy-dissipation mechanisms was developed. First, the notion and rationale of the damper was illustrated. Then, an analytical model enabling quantification of the hysteretic behaviour of the proposed SMA-VFSD was derived. A numerical parametric study using validated modelling techniques was subsequently conducted. The good agreement between the hysteretic responses of numerical models and analytical predictions confirmed the promise of the proposition and the adequacy of the analytical design model. Resorting to the analytical model, sensitivity analyses covering a wider spectrum of design parameters were performed, and the influence of essential parameters on the hysteretic behaviour of the damper was examined. Finally, the constant-ductility-based non-linear spectral analyses of an equivalent single-degree-of-freedom (SDOF) system representing steel frames equipped with SMA-VFSDs were performed to quantify the structural seismic demand and examine the effectiveness of the damper in improving the structural seismic performance. Two conventional self-centring systems characterised by flag-shaped hysteretic features were also studied for comparison. The analysis results showed that the multiple energy-dissipation mechanisms of the SMA-VFSDs are beneficial in reducing the structural inelastic seismic demand, highlighting the potential of the damper towards performance advances in self-centring structures. • A self-centring damper with multiple energy-dissipation mechanisms was developed. • An analytical model predicting the damper's behaviour was established. • The sensitivity analysis of damper design parameters was examined. • Non-linear spectral analyses of an equivalent SDOF system were conducted. [ABSTRACT FROM AUTHOR]

This study reported an experimental study of hybrid-self-centering connections (HSCCs) employing energy dissipation sequences. The dual self-centering mechanism of the connection consisting of post-tensioned (PT) steel strands and shape memory alloy (SMA) bolts provided the self-centering driving force, and the energy dissipation sequences can be realized by friction dampers and SMA bolts. An experimental program employing five proof-of-concept connections was tested under the cyclic loading scenarios. The test results including hysteretic responses, strain gauge readings, force evolution in PT steel strands, strength and stiffness, energy dissipation capability, and self-centering ability were examined and discussed. The obvious trilinear hysteretic feature of the test connection accompanied by excellent self-centering ability, moderate energy dissipation capability, and satisfactory ductility was confirmed. In addition, the encouraging repairability of the test connection was verified by retests of repaired specimens. Subsequently, finite element (FE) models verified by the experimental results were developed to further examine the behavior of the proposed connection. A design model was developed enabling the quantification of the multilinear behavior of moment-rotation responses of the proposed connection. The good agreement between the stiffness and strength of the connection from the test data confirmed the rationality of the proposed design model. The analysis results of nonlinear spectral analyses confirmed the effectiveness of structures equipped with the HSCC in reducing acceleration response. [ABSTRACT FROM AUTHOR]

This paper reports on a practical seismic-damage-control evaluation method of a high-strength steel (HSS) system comprising HSS frames with energy dissipation bays (EDBs). First, the design concept and seismic performance of the system are illustrated and verified by an experiment on a large-scale two-storey two-bay HSS frame with EDBs. Critical issues considering quantification of the seismic-damage-control threshold and the performance requirement of HSS members are clarified. A stepwise procedure that accounts for both the peak response of the HSS members and the cumulative effect of EDBs is then constructed by applying the energy balance concept and a micromechanics-based fracture model. Subsequently, the procedure is implemented on a prototype structure. The results indicate that the proposed procedure is effective for evaluating seismic performance of both HSS members and EDBs. Compared with direct application of non-linear history response analysis, which is time consuming, the proposed procedure simultaneously retains conceptual and computational advantages. [ABSTRACT FROM AUTHOR]

An experiment was performed focusing on the seismic performance of a steel moment resisting frame (MRF) composed of high strength steel (HSS) members and energy dissipation bays (EDBs) with reduced beam section (RBS) beams. The behavior of the system is characterized by a damage-control stage with concentration of inelastic deformation in the energy dissipation bay (EDB), followed by a main-structural-damage stage with distributed plastification. Test results show that the system exhibits damage-control behavior and insignificant increase of residual drift in the damage-control stage. Even though the system is loaded to the stage in which inelastic deformations initiate at the main frame composed of high strength steel members, the system can deform in a ductile manner and the energy dissipation is stable. For further analysis of the system, the applicability of the trilinear kinematic hysteretic model is validated based on a proposed algorithm for idealizing the skeleton curve and the improved accuracy is achieved compared with the universally used bilinear model. Dynamic analyses are also performed based on prototype systems to validate the structural performance. [ABSTRACT FROM AUTHOR]

High strength steel frames with curved knee braces (HSSFs-CKBs) are typical seismic resilient structural systems. Previous experimental research showed that an HSSF-CKBs specimen could be readily repaired after an earthquake by replacing damaged curved knee braces (CKBs) which serve as energy dissipating devices, as long as high strength steel components stay essentially elastic to shake down post-earthquake residual deformations. To provide a practical tool for engineers in seismic resilience design, this paper developed a performance-based damage-control design framework for low-to-medium rise HSSFs-CKBs. A multi-storey HSSF-CKBs was first interlinked with an equivalent bilinear single-degree-of-freedom (SDOF) system. Then, the seismic input energy demand of the HSSF-CKBs was determined based on the seismic energy balance of the equivalent SDOF system, which was further distributed to different storeys to design structural components. To facilitate the design, a stepwise design procedure was proposed. A three-storey low-rise HSSF-CKBs and a six-storey medium-rise HSSF-CKBs were designed following the procedure. The seismic response of the designed structures was examined by pushover analyses and nonlinear time-history analyses using numerical models verified by shaking table test data. The analysis results showed that the designed structures exhibited the expected behaviour, and the maximum interstorey drifts were controlled below the design target, which verified the effectiveness of the proposed design framework. • A subassemblage model of high strength steel frames with curved knee braces was developed. • Numerical modelling techniques were developed and verified by shaking table tests. • A performance-based damage-control design framework was proposed. • The adequacy of the proposed design framework was confirmed. [ABSTRACT FROM AUTHOR]

This study presented reduced-order modeling methods for evaluating the structural robustness of steel frame buildings with different composite floor slabs under ground floor column loss scenarios. The adequacy of the reduced-order modeling technique was justified by relatively high-fidelity models, which were verified by a full-scale composite floor test and detailed material coupon tests. This reduced-order modeling method was applied to the progressive collapse simulation of a five-story prototype building. The effect of floor slabs, slab rebars, and steel decks' longitudinal continuity on its progressive collapse resistance was examined. Composite slabs with four different profiled steel decks were considered in this study, which are trapezoidal deck, dovetail deck, reentrant deck, and rebar-truss deck; in addition, reinforced concrete (RC) slab was also considered for comparative purposes. To account for the possible sudden column failure scenario in practice, an energy-based approach was used to convert the quasi-static response curves to dynamic response curves. The structural robustness was evaluated by comparing each column failure case's dynamic ultimate capacities with corresponding design requirements. The structural robustness of prototype buildings under progressive collapse scenarios was summarized and discussed. The analysis results showed that the structural robustness of the prototype building with rebar-truss composite slab was higher than that with RC slab or other composite slabs. The prototype building with floor slabs using HRB400 rebars had higher structural robustness than that using CRB550 rebars. • Structural robustness of steel frame buildings with different composite slabs is evaluated. • Reduced-order modeling methods are proposed for simulating the progressive collapse response of different composite slabs. • Rebar-truss composite slab has the advantage in improving structural robustness of steel frame building. • The effect of longitudinal continuity of steel deck is investigated. [ABSTRACT FROM AUTHOR]

Driven by the demand of producing novel seismic resilient structures, this study focused on steel moment resisting frames equipped with superelastic shape memory alloy (SMA) connections in the self-centring energy dissipation bays, and the emphasis was given to a direct-iterative design method for performance-based-plastic-design of the system under earthquake motions. Utilising the equivalent single-degree-of-freedom (SDF) oscillator which may reasonably quantify the dynamic responses of a multi-storey structure, an inelastic structural seismic demand model motivated by nonlinear spectral analyses was developed, and the statistic features were accounted. As the theoretical basis of the design philosophy, the seismic energy equilibrium equation of the structure was correlated with structural arrangement and earthquake motion characteristics. Then, a stepwise plastic design methodology enabling practising engineers to search for a feasible design strategy was proposed. Three prototype structures were developed following the proposed method, and finite element models of the systems were developed. The adequacy of the modelling techniques was verified by the test database, and the sufficiency of the hysteretic model of the structure was also justified. The seismic responses of the prototype structures were estimated by nonlinear static and dynamic analyses. The analysis data pool confirmed that the prototype structures were able to achieve the damage-control objective by limiting the maximum interstorey drifts below the prescribed deformation threshold, and inelastic actions were concentrated in the self-centring energy dissipation bays. [Display omitted] • Probabilistic energy factor demand spectra for self-centring system under near-field earthquake motions was developed. • A performance-based-plastic-design methodology was developed from a statistic perspective. • The sufficiency of the proposed design methodology was confirmed. [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]

Gusset plates are key connection components in steel truss and braced frame structures. To provide a comprehensive insight into the behaviour and design of these components, this paper thoroughly reviews the research studies and design methods of steel gusset plates subjected to various loading conditions. A particular focus is placed on the design of steel gusset plates under tension and compression, including the well-known Whitmore method, block shear and buckling design approaches. Representative design methods are reviewed and evaluated based on available test data. It is concluded that a proper block shear method in conjunction with a proper net section tension check can accurately predict the tension capacity of steel gusset plates. In comparison, the design for compression capacity is subjected to a much greater uncertainty due to the complexity of the compressive behaviour that is largely affected by the boundary condition, plate action and post-buckling effect. Further discussions are made on the frame action, as well as the stiffening and seismic detailing strategies of steel gusset plates. Finally, future research needs are identified in the field of gusset plate research. • Research on steel gusset plates is reviewed. • Early age research and design practice of gusset plates are overviewed. • Whitmore and block shear methods for gusset plates in tension are reviewed and evaluated. • The buckling behaviour and design of gusset plates in compression are overviewed. • Strengthening strategies and seismic detailing of steel gusset plates are briefy discussed. [ABSTRACT FROM AUTHOR]

In this study, the hysteretic behaviour of shape memory alloy (SMA) plates under cyclic tension-release loadings was examined to promote their seismic applications, with an emphasis on large-size SMA plates with different geometries. Based on a series of SMA plate coupons extracted from base plates with different geometries, the thermal characteristics were investigated, and the phase transformation behaviour of the SMA plates was characterised. Subsequently, cyclic tension-release tests were conducted on the SMA plates in the laboratory, and the key mechanical performance indexes including the transformation strength, post-yield behaviour, self-centring capabilities, and energy dissipation abilities were carefully investigated. According to the results, SMA plates have a comparatively encouraging self-centring ability and moderate energy dissipation capabilities within a specified strain range. However, larger SMA plates show less satisfactory self-centring behaviour and are prone to brittle fracture at the edges. Based on the test programme, a numerical investigation was conducted to offer further insight into the potential applications of large-size SMA plates in the seismic field. A practical modelling procedure, namely the hybrid finite element (FE) modelling technique, was proposed and used to reproduce the degradation and cumulative residual deformation in the SMA plates. Moreover, nonlinear response history analyses (NL-RHAs) were performed on a prototype steel frame equipped with SMA plates in the connections to verify the feasibility of using large-size SMA plates in steel structures. • Six large-size SMA plates with various geometric dimensions were fabricated and heat-treated. • The influence of plate size on the cyclic tension-release behaviour of SMA plates was examined. • A practical FE modelling strategy and flowchart procedure for the SMA plates were proposed and verified. • The feasibility of exploiting SMA plates in seismic-resistant steel frames was explored. [ABSTRACT FROM AUTHOR]

The traditional cold-formed thin-walled (CFTW) steel sheathed walls are prone to have misalignment at the joints of wall panels and the damage of self-tapping screw connections under earthquake, resulting in obvious pinching of the hysteretic curves. In order to improve the energy dissipation and shear bearing capacity of the lateral resisting member in CFTW steel structures, an innovative structure called CFTW steel structure with braced ductile shear panel (CFTW-BSP) was proposed in this paper. Four full-scale one-story one-bay CFTW-BSP specimens containing two X-shaped and two K-shaped brace specimens were designed and tested under horizontal cyclic loads. The effects of configuration types, shear panel aspect ratios and slotted holes were investigated by comparing the lateral performance. In addition, the replaceability of the shear panel damper was analyzed. In general, the specimens performed well with a stable and plump energy dissipation capacity. The plastic deformation concentrated on the shear panel before 2% interstory drift, and then the end stud bases yielded and cracks propagated near the hold-downs at the ultimate stage. The braces always remained elastic during the tests. For X-shaped brace specimens, the slotted holes on shear panel can improve the ductility but decrease the energy dissipation capacity of the structure. For K-shaped brace specimens, the lateral resistance of the structure can be improved by decreasing the shear panel aspect ratio. • An innovative CFTW steel structure with braced shear panel (CFTW-BSP) is proposed. • Seismic performance of CFTW-BSP is studied by experimental research. • The influences of slotted holes on shear panels and shear panel aspect ratios are investigated. • The replaceability of the shear panel damper is investigated. • The proposed structures show excellent lateral resistance and the shear panel damper can be replaced at 1% interstory drift. [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]

• 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 tension-only concentrically braced steel beam-through frames are compelling options for low-to-medium rise buildings in low to moderate seismic regions. This paper quantifies the seismic demand of damage-control TCBSBFs under near-fault ground motions. Firstly, the hysteretic model of TCBSBFs in the damage-control stage is validated based on the test database of a prototype structure. Subsequently, representative single-degree-of-freedom (SDOF) systems with the verified hysteretic law are subjected to 320 near-fault seismic records. A parametric study including more than 8,208,000 nonlinear spectral analyses is carried out. The effect of the hysteretic parameters (i.e. the post-yield stiffness ratio and the ductility in the damage-control stage) and the damping ratio on the energy factor is examined in detail. The results revealed that the energy factor demand of bilinear slip kinematic SDOF systems representing the TCBSBFs under near-fault ground motions is sensitive to the hysteretic parameters in the damage-control stage. On the basis of 8,208,000 computed values of the energy factor, the probabilistic distribution of the energy factor exhibits a certain degree of positive skewness. In order to ensure the seismic reliability of TCBSBFs, a probabilistic model of the energy factor governed by the lognormal distribution is developed to facilitate the performance-based seismic design of TCBSBFs. Based on regression analysis of the database, two empirical formulas are proposed for two key parameters. The design model may offer practical guidelines for the design of TCBSBFs. • The SDOF systems were used to represent the TCBSBFs in damage-control stage. • More than 8,208,000 nonlinear SDOF time-history analyses are carried out. • The seismic demand of damage-control TCBSBFs is quantified based on the energy factor. • A probabilistic model of the energy factor is proposed. [ABSTRACT FROM AUTHOR]

In this research, the seismic performance of a half-scaled three-storey high strength steel frame with curved knee braces (HSSF-CKB) under extreme earthquakes was investigated through shaking table tests. The test results demonstrated that the test structure maintained an encouraging recentring capacity under extreme earthquakes. By replacing the damaged curved knee braces, the structural stiffness was recovered to a certain extent. The failure mode of the test structure was governed by fracture of high strength steel beams, buckling of curved knee braces, and concrete crushing. Furthermore, a previously proposed analytical model for HSSF-CKBs was further validated by the test data. • A half-scaled, three-storey HSSF-CKB was subjected to simulated extreme earthquakes. • Encouraging recentring capacity of the test structure was observed. • Structural repair was achieved through CKB replacement. • The failure mode of the test structure was identified. • A previously proposed analytical model was further validated. [ABSTRACT FROM AUTHOR]

This study investigates the seismic behavior of an innovative cold-formed thin-walled (CFTW) steel frame with a K-shaped braced shear panel (BSPK). This new structural system is expected to improve the energy dissipation capacity of traditional CFTW steel structures. Eight full-scale one-story one-bay CFTW steel frames with BSPKs (CFTW-BSPKs) were subjected to lateral cyclic loads to examine the influence of the shear panel width-to-thickness ratio, aspect ratio, stiffening ribs, and slotted holes. The damage evolution, yield sequence, hysteresis curve, skeleton curve, load-carrying capacity, ductility, energy dissipation capacity, and stiffness degradation were analyzed. The test results demonstrated that all specimens exhibited stable hysteretic performance as well as a high load-carrying capacity. The seismic behavior consisting of energy dissipation and load-carrying capacity can be improved by increasing the shear panel width-to-thickness ratio or decreasing the aspect ratio. The stiffening ribs can significantly improve the load-carrying capacity and stiffness degradation of the specimens, while the slotted holes have a negative effect on the seismic behavior of the specimen. • Experimental studies on eight full-scale one-story one-bay CFTW steel structures with K-shaped braced shear panels (CFTW-BSP) are carried out. • The effects of shear panel dimensions, stiffening ribs, and slotted holes are investigated. • The applicability of shear stiffness equation for the shear panel are discussed. • The damage evolution processes of the structures are investigated. [ABSTRACT FROM AUTHOR]

A composite wall is the primary lateral force-resisting system in a cold-formed thin-walled steel structural system. The shear force between the upper and lower walls is transmitted through an inter-story connection in the cold-formed thin-walled steel platform framing system. In this study, the 16 platform framing inter-story connection specimens were subjected to cyclic loading to study the shear resistance, the failure modes, deformation, and the influence of stiffeners, lateral rigid blocking, X-shaped straps, and vertical. Hysteretic curves, skeleton curves, shear bearing capacity, and lateral stiffness values were obtained from the testing. The results showed that the specimens with only stiffeners had a lower shear capacity and lateral stiffness, which were significantly affected by the vertical force. Further, short stiffeners were not fully effective. The highest shear capacity and lateral stiffness values were characterized for the specimens with rigid blocking. Increasing the rigid blocking improved the shear resistance of the specimens, and rigid blocking with the same height as the floor joists contributed to excellent shear capacity and lateral stiffness of the specimens under vertical loading. The lateral stiffness of the inter-story connection was also significantly increased by using X-shaped straps, and the vertical force resulted in substantial decrease of the lateral stiffness. Based on the test results and a comparison of the nominal shear strength values required by current specifications, this study proposed improvements to the design of cold-formed thin-walled steel platform framing inter-story connections. [Display omitted] • Low cyclic loading tests were performed on 16 inter-story connection specimens. • Hysteretic curves, skeleton curves, shear bearing capacity, and lateral stiffness values were obtained. • It deals with the impacts of stiffeners, lateral rigid blocking, X-shaped straps, vertical forces, amount and height. • It provides improvements to the design of cold-formed thin-walled steel inter-story connections. [ABSTRACT FROM AUTHOR]