This study presents a novel hybrid self-centering system aiming to overcome critical shortcomings identified in the existing self-centering solution. Two types of hybrid brace incorporating shape memory alloy elements and integrated viscoelastic dampers are first introduced, followed by a system-level analysis on a series of prototype buildings. The results show that using viscoelastic material to reach a moderate damping ratio is highly effective in peak and residual deformation control.Floor acceleration is also effectively controlled by the hybrid solution. A parametric study is then conducted, and design recommendations are given. A probability-based residual deformation prediction model is finally proposed.

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SummaryQuasi‐static testing is one of the most commonly used experimental methods for examining the seismic performance of structural members. However, consistent loading protocols for experimental seismic qualification of members in emerging steel frames such as self‐centering braced frames (SCBFs) as well as in some conventional ones including buckling‐restrained braced frames (BRBFs) are still lacking. This paper aims to propose standardized loading protocols based on time‐history dynamic analysis on a series of prototype building frames, including steel SCBFs, BRBFs, and moment‐resisting frames (MRFs), where both far‐field and near‐fault earthquakes are considered. The methodology for the development of the loading protocols involves ground motion selection and scaling, design and analysis of prototype buildings, analysis results processing, and rainflow cycle counting, together with extra justification steps. The proposed loading protocols are consistently derived based on the MCE‐level seismic hazard and 84th percentile values of key seismic demand parameters. These parameters are number of damaging cycles Nt, maximum inter‐story drift θmax, inter‐story drift range Δθi, sum of inter‐story drift range ΣΔθi, and residual inter‐story drift θr. The analysis confirms the variations in these seismic demands imposed on the different structural systems under different types of ground motions, highlighting the necessity of developing separate loading protocols for the different cases. The assumptions, decisions, and judgments made during the development of the loading protocols are elaborated, and the conditions and restrictions are outlined. The rationality of the proposed loading protocols is further justified through demonstrating the cumulative distribution function and energy dissipation demand of the systems.

This paper comprehensively discusses the behavior and failure risk of self‐centering braced frames suffering tendon fracture. The fundamental mechanism of tendon failure in self‐centering braces (SCBs) is first introduced, followed by the design and analysis of a series of prototype buildings with different tendon materials and brace configurations. Assuming a normal distribution of tendon fracture strain, the dynamic behavior of the frames is then assessed by a suite of ground motion records, covering both far‐field and near‐fault ones. The collapse and residual deformation fragilities of the frames are further evaluated, and the study ends with a risk assessment considering a 50‐year service period. Among other findings, the study indicates that tendon fracture tends to increase the peak interstory drift, especially for the structure with smaller tendon fracture strains. Tendon fracture also compromises the self‐centering capability significantly, although there is no obvious statistical correlation between tendon fracture and the peak floor acceleration. The probability of collapse and that of exceedance of certain residual drift both increase evidently when tendon fracture is considered. The failure probabilities are closely related to the available deformability of the SCBs, where dual‐core SCBs show less sensitivity to tendon fracture. The probability of collapse of the considered frames over 50 years of service increases from 1.25‐2.12% to 3.58‐6.52% when tendon fracture is considered. Considering a residual drift threshold of 0.5%, the probability of exceedance of the same structures over the same life span increases from 1.78‐3.54% to 5.46‐9.71%.

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