Loading protocols for experimental seismic qualification of members in conventional and emerging steel frames

Abstract

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.