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This study explores comparative seismic performance of a shape memory alloy (SMA)-only device, a friction damper, and a hybrid self-centering device. The self-centering device considered in this study, named as superelastic friction dampers (SFDs), is a hybrid damper operating on a mechanism where SMA cables and frictional components are arranged in parallel. A detailed description of the device and an experimental characterization of mechanical behavior are presented first. Then, an 8-story archetype steel frame building is designed and modeled with each seismic protection device (SMA-only, hybrid self-centering, and friction only). To enable comparative performance assessment, each device is designed to have similar initial stiffness and the same maximum force at design displacement. Nonlinear time history analyses are conducted using a total of 44 ground motion records. The results are evaluated to compare performance of each frame design at design-basis and maximum considered earthquake hazard levels. Next, a risk-based seismic hazard demand analysis framework that involves comprehensive incremental dynamic analyses is employed for further assessing the performance of each system. The experimental results validate the parallel working mechanism of SMA cables and frictional components in the SFD, with 90% of the damper deformations recovered. Comparative analysis of seismic responses demonstrates the excellent performance of the SFDs in reducing interstory drift ratio, residual interstory drift ratio, and absolute acceleration responses. Furthermore, fragility analysis and risk-based seismic hazard assessment further reveal that the SFDs provide a well-balanced combination of energy dissipation capability and self-centering ability, thereby enhancing the seismic resilience of structures. • The working mechanism and mechanical performance of the superelastic friction damper have been experimentally validated. • Risk-based seismic hazard analyses have been conducted for frames equipped with various dampers. • SFD is capable of enhancing seismic resilience effectively by leveraging energy dissipation and self-centering capabilities. [ABSTRACT FROM AUTHOR]

The present paper investigates the probabilistic assessment of the seismic performance of steel MRFs designed according to Eurocodes. The considered MRFs are three- and five-storey high and are analysed by the multiple stripe method of analysis by means of sets of earthquake ground motions that depend in frequency content, energy and duration on the value of the selected seismic intensity measure. Additional uncertainties are related to the mechanical properties of steel, dead and live loads and equivalent viscous damping ratio. Different criteria are defined to assess the performance at the achievement of different limit states, in terms of interstorey drifts and damage indexes. To reach a synthetic evaluation of the seismic performances, the mean annual frequency of exceedance of the assigned limit state condition is also reported. Based on a Monte Carlo simulation the paper evaluates the effects of the single uncertainties on the seismic performances and suggests proper modifications to the simplified approach included in FEMA documents to mime the results of a full probabilistic approach. • Uncertainties of mechanical properties of steel, loads and viscous damping ratios are added to those of the seismic input. • Additional uncertainties have a minor effect on the fragility curves in terms of global response parameters. • Additional uncertainties mainly affect the median value of the fragility curves in terms of local response parameters. • If the total dispersion of the results is estimated by SRSS, the frequency of exceedance of local response parameters is underestimated. • A simplified approach is proposed to mime the results of a full probabilistic approach. [ABSTRACT FROM AUTHOR]

In previous research, the seismic behavior of linked column frame (LCF) system as a dual structural steel frame system that Consists of the primary linked column (LC) and the secondary moment frame (MF) systems has been evaluated. In this research, based on the high capacity of the linked column system in lateral load resisting, this system has been used as the only lateral load resisting system in the building frame. Studies have shown that this approach not only eliminates the main disadvantages of the LCF system, but also preserves the ability to repair structures after an earthquake. Therefore, the designed models of the linked column system have been evaluated using nonlinear static pushover analysis, nonlinear dynamic time history analysis, incremental dynamic analysis and endurance time method analysis. In the evaluation of the seismic behavior of the linked column system, design approach, structural stability and collapse mechanism, ductility, the seismic performance factors of response modification coefficient (R), overstrength factor (Ω 0) and deflection amplification factor (C d), the values of interstory drift ratio at the DBE and MCE seismic hazard levels, maximum seismic capacity and fragility curves, permanent displacement after the earthquake and the weight of steel used in the structure have been investigated. Each of the analysis results shows that the linked column system has a suitable seismic behavior against earthquakes. Therefore, in a preliminary evaluation, the linked column system is introduced as a steel lateral load resisting system that provides the ability to repair structures after an earthquake. • Evaluation of seismic behavior of linked column system using nonlinear analysis methods. • Quantification of linked column system seismic performance factors. • Comparison of the results of endurance time method with nonlinear time history analysis and incremental dynamic analysis. • Ability to quickly repair steel structures after an earthquake. [ABSTRACT FROM AUTHOR]

This paper presents an innovative “collapse prevention” system for seismic resistant design in new construction and existing buildings. The collapse prevention system consists of a collapse inhibiting mechanism, such as a pair of slack cables or loose linkages, working in tandem with the main lateral-force resisting system and engaging the gravity framing to avert collapse. In this holistic design approach, the main lateral-force resisting system and gravity framing are used to provide adequate performance under low to moderate level ground motions, and the collapse inhibiting mechanism is deployed as a back-up to provide life safety under extreme ground motions. The collapse inhibiting mechanism may be augmented with energy dissipation devices (small viscous fluid or visco-elastic solid dampers) to enhance performance under wind or small seismic events. Analytical performance of archetypical 1-story, 2-story, 4-story, and 8-story steel-frame buildings employing collapse prevention systems indicate that collapse prevention systems substantially reduce the probability of collapse during Maximum Considered Earthquake (MCE) ground motions, depending on the building and collapse inhibiting mechanism deployed. Seismic hazard data suggests that collapse prevention systems would provide a 1% or less risk of collapse in 50 years in many locations, mostly in the central and eastern United States. [ABSTRACT FROM AUTHOR]

This study focused on the development and validation of a novel brace design that incorporated a hinged truss member and a set of lever-armed damper (LAD), namely LAD-Brace, for structural performance enhancement. The lever-armed damper was designed with adequate rotation mechanism to generate amplified-deformation and uniform yield zones in the tapered energy dissipation plate for efficient energy dissipation. A series of cyclic loads and constant peak amplitude tests were conducted on LAD-Braces with various geometries in the energy dissipation plates. Analytical expressions for yield strength estimation were derived and effectively validated by the test results. Cyclic load test results showed that adequate strength, effective equivalent viscous damping and significant energy dissipation were simultaneously achieved which justified the design applicability for earthquake-resistant purposes. Investigation through constant peak amplitude tests revealed that LAD-Braces, when designed with adequate geometries, possessed further seismic resilience after experiencing major earthquake excitation, thus validated the proposed design effectiveness and robustness. [Display omitted] • A novel brace design to improve energy dissipation efficiency was proposed and validated. • Important experimental information was presented. • Analytical expressions for yield strength estimation were derived and effectively validated by the test results. • Effective viscous damping and energy dissipation were achieved in the proposed brace design. • Effective seismic performance and post-earthquake resilience of brace member was compared and validated [ABSTRACT FROM AUTHOR]

The based-isolation with tuned mass damper inerter (BI-TMDI) is utilized to enhance the seismic response of steel High-voltage substation switches mounted on frame (SMF). An analytical model with three degree-of-freedom was explored for the optimization analysis and seismic design. Firstly, the displacement variance of this SMF-BI-TMDI system in the whole frequency spectrum was obtained, using statistical Cauchy's residue theorem, which provides an explicit expression of the optimization objective function. Further, a comprehensive parametric analysis was performed, covering a wide spectrum of influential factors. Subsequently, the effectiveness of the proposed analytical model was confirmed by time history response analysis of prototype structures subjected to an ensemble of earthquake motions. The model was also compared with conventional analytical models for structural seismic optimization, showing obviously improved accuracy. This innovative control method and optimization analysis in BI-TMDI enlighten its potential with enhanced vibration control effect for protection of steel substation under earthquake motions. • The exactly theoretical optimization objective function of the 3-DOF BIS-TMDI is obtained. • A parametric study is conducted to illustrate the parametric influence on the optimization results. • The interaction among switches, the base-isolation frame and the TMDI is investigated. • The effectiveness of this optimization method is confirmed with the time history analysis. [ABSTRACT FROM AUTHOR]

Steel dual structures incorporating special concentrically braced frames (SCBFs) and special moment frames (SMFs) are, in general, effective for their high lateral stiffness and ductility. As such, ductile dual CBFs are often treated as a remedy for mitigating permanent drift demands along with the potential drift concentration in isolated stories. However, despite the benefits and interest, the effect of the bracing configuration on the seismic response of the dual concentrically braced systems, designed following the current capacity design approach stipulated in AISC Seismic Provisions, in particular, has not been thoroughly examined to date. The present study aims to shed light on the impact of the bracing scheme on the seismic behavior of dual SCBFs coupled with SMFs as backup frames. For this purpose, 4- and 10-story dual SCBFs with the commonly used chevron, split X, V, and cross X type bracing configurations are designed according to ASCE 7 and AISC 341. Then, the frames are subjected to a suite of ground motions. The nonlinear time-history analysis results are contrasted and discussed in terms of the peak and permanent drift demands, horizontal floor acceleration demands along with brace ductility demands. [Display omitted] • Bracing configuration effect on the seismic response of the steel dual CBFs has not been thoroughly examined to date. • The mean drift demands in the low- and mid-rise dual structures were moderate. • Backup frames dissipated less than 10% of the overall inelastic energy dissipation on average. • The limits on the acceleration demands specified in the current US building code seem to be reasonable. • The median responses in all dual structures were below the recommended permanent drift limits. [ABSTRACT FROM AUTHOR]

A Buckling-restrained brace with gap-supported tendon protection (TP-BRB) is a new buckling-restrained brace with post-onset stiffness. The critical design parameters of the TB-BRB are the values of the initial gap and the additional stiffness. In this paper, 3-, 6-, 9-, and 12-story frame buildings were designed with two types of bracing members: Buckling-restrained braces (BRBs) and TP-BRBs. Nonlinear time-history analyses were conducted to investigate the influences of the initial gap and the additional stiffness. The results illustrate that the TP-BRBFs exhibit smaller maximum story drift (θ max) and residual story drift than BRBFs, and the formers show a more uniform distribution of lateral deformation than the latter. For lower TP-BRBFs, a decrease of the initial gap is an effective way to improve their seismic performances, and the initial gap is recommended to be the difference between the maximum axial deformation of the TP-BRBs under maximum considered earthquake and its yield deformation (u y). For taller TP-BRBFs, the initial gap is suggested to be (8.5–12) u y in the premise of cables remaining elastic under maximum considered earthquake. On the other hand, an excessive additional stiffness would reduce the potentiation of TP-BRB on the seismic performances, and it increases manufacturing costs of the TP-BRB. The additional stiffness of the TP-BRB is recommended to be less than 0.25 k e , where k e is the initial stiffness of the TP-BRB. Moreover, an estimation formula to calculate the minimum value of θ max and an iteration design procedure were proposed for taller TP-BRBFs. [Display omitted] • Effects of the post-onset stiffness on performances of TP-BRBFs was investigated. • Excessively reducing the initial gap and increasing the additional stiffness are irrational. • Recommended values to the initial gap and the additional stiffness of TP-BRBs are provided. [ABSTRACT FROM AUTHOR]

The development of low-damage steel moment resisting connections for seismic applications provides designers with techniques to dissipate energy without relying on plastic deformations of beam sections, thus avoiding connection strength and stiffness deterioration and providing the opportunity of adding a self-centering mechanism to avoid residual displacements. In this paper, the system-level performance of two low-damage connections, the sliding hinge joint (SHJ) connection and the self-centering sliding hinge joint (SCSHJ) connection, is evaluated using analytical models. New component models are developed for each of the connections and validated using available experimental results. The global performance of three steel frames of different heights, using either the SHJ connection or SCSHJ connection, are then compared to otherwise identical frames with either pre-Northridge (PRENORTH) connections or reduced beam section (RBS) connections. The benefits of these new connections for the global performance of the frames are presented through fragility curves for 27 response indices, comprising three engineering demand parameters (maximum inter-story drift, residual drifts, and accelerations) under three earthquake hazard types (shallow crustal, subduction, and main-shock-after-shock combinations) for three performance objectives. The global performance of the frames with the SHJ connection is similar to that of frames with the RBS connection, while avoiding yielding and damage in the connections. The SCSHJ connections further enhance the good performance of the SHJ connection by also reducing residual drifts and peak floor accelerations. This improvement in performance translates directly to reductions in the expected annual loss, particularly for structures exposed to longer duration ground motions or main-shock-after-shock sequences. • Presents models for both the newly developed sliding hinge joint (SHJ) and self-centering sliding hinge joint (SCSHJ) steel moment resisting connections. • Compares the global performance of three different frame heights using either non-ductile, pre-qualified, SHJ, or SCSHJ connections. • Identifies that the SCSHJ connections has the greatest benefit during subduction earthquakes and during main-shock after-shock ground motion sequences. • Demonstrates that the SCSHJ connections has the greatest life-cycle benefits to taller structures more susceptible to longer duration ground motions. [ABSTRACT FROM AUTHOR]

In order to facilitate floor assembly and pipeline paving, this paper puts forward a new kind of prefabricated opening-web steel channel beam-column joint with double flange cover plates (POWSCBCJ) which is based on the design concept of plastic damage concentration and replaceable damage components. Six quasi-static reciprocating loading tests were carried out on four joints, and the hysteretic curves, skeleton curves, slip curves and strain curves of each specimen were obtained. The effects of thickness of flange cover plate (FCP), the quantity of connecting bolts and the bolts spacing of FCP and other parameters on the seismic performance and post-earthquake repairable performance of the joint are mainly investigated, and the post-earthquake repairable function, and fatigue performance of the joint under low-cycle reciprocating load are evaluated. Experimental study shows that this kind of joint has good bearing capacity, seismic performance and low-cycle fatigue performance. The joint can transfer the plastic hinge to the replaced FCP by strengthening the flange of the cantilever beam and weakening the FCP, so as to protect the major components such as beams and columns, and the joint function can be quickly repaired by replacing the energy dissipation components after earthquake; the repaired joint also has good bearing capacity and seismic capacity. Each design parameter has great influence on the bearing capacity and energy dissipation capacity of the joint. Unlabelled Image • A new prefabricated opening-web steel channel beam-column joint was proposed. • Four specimens were designed and six low cyclic loading tests were conducted. • Influence of design parameters on seismic performance of POWSCBCJs was studied. • Several performance curves and failure modes of POWSCBCJs were obtained. • The repair program of replacing the connection device is feasible. [ABSTRACT FROM AUTHOR]

This study addresses the nonlinear seismic responses of ordinary moment frame building upgraded with a series of passive protective systems. To this, friction damper (FD) as an energy dissipation device and lead rubber bearing (LRB), friction pendulum bearing (FPB), and high damping rubber bearing (HDRB) as base isolators were considered. The effectiveness of the isolation systems together with the dampers was investigated comparatively. For this purpose, eight different cases were taken into account. The first case contains a five storey steel ordinary moment frame considered as fixed-base (FB), the other four cases are the single use of FD, LRB, FPB, and HDRB in such frame, and the last three cases include the upgrading of the frame with the combination of FD with each of the base isolation systems. They are modelled using a finite element program, and evaluated by the nonlinear time history analyses in which seven ground motion records were adopted. The seismic performance of the passive protective systems was evaluated by the engineering demand parameters such as storey displacement, bearing displacement, relative displacement, roof drift ratio, interstorey-drift ratio, absolute acceleration, base shear, base moment, hysteretic curve, and energy dissipation. One of the main outcomes of this study was that single protective system could not always satisfy fully operational performance level, while the combined systems of the base isolation with friction damper effectively achieved for the case study frame. Furthermore, the results showed that the combined systems were capable of limiting the inter-storey drift without increasing the absolute accelerations. Graphical abstract Unlabelled Image • This study proposes several models of the seismic protective systems to upgrade ordinary moment frame (OMF). • Single use of FD, LRB, FPB and HDRB, and their combinations are implemented. • Seismic response of OMF with the protective devices is significantly enhanced. • Fully operational damage state could be provided in the case of combined systems. [ABSTRACT FROM AUTHOR]

Built-up battened columns are lightweight and have a larger moment of inertia when compared with columns made by a single profile. However, these columns have shown poor seismic performance during past earthquakes. In this study, experimental and numerical investigations were focused on the seismic performance of these columns. A full-scale built-up battened column was subjected to quasi-static cyclic loading and its response was recorded. Furthermore, 81 built-up battened columns were simulated in ABAQUS software. The effects of batten spacing, batten thickness, chord distance, and axial force on the cyclic response of simulated columns were investigated. The obtained results indicated that the bulging of chord webs together with the local buckling of chord flanges were the main reason for the failure of columns. Besides, in all columns, the maximum stress in chords was almost twice larger than the maximum stress in battens. Furthermore, an increase in the batten thickness or a decrease in the batten spacing slightly increased the ultimate load of columns. Columns with a thicker batten exhibited a slightly smaller plastic deformation. The displacement ductility ratios of the built-up battened columns were all less than two even when they were subjected to an axial compression ratio smaller than 0.2. It was also observed that, in all columns, the ratio of ultimate load to the effective yield strength was less than 1.4. Unlabelled Image • The bulging of the web and the local buckling of the flange were observed in all columns. • The displacement ductility ratio of all columns was less than two. • The batten thickness and spacing had an insignificant effect on the strength degradation and reserved strength. • The ratio of the ultimate load to the effective yield load of all columns was less than 1.4. • An increase in the batten thickness or a decrease in the batten spacing slightly increased the ultimate loads of columns. [ABSTRACT FROM AUTHOR]