Novel loading protocols for concentrically braced frames under near-field pulse-like earthquakes
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Researchers |
Elyas Ali Zehi and Mahmoud Ali |
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Published in |
Structures, volume 84, article 111054, February 2026. |
Abstract |
Quasi-static testing remains a cornerstone of seismic performance evaluation for concentrically braced frames (CBFs). However, contemporary loading protocols exhibit substantial divergence in their derivation methodologies, resulting in marked differences in imposed rotational demands, cyclic loading sequences, and cumulative damage potential. This variability creates a pronounced validation gap, obscuring the specific influence of protocol derivation method on the performance assessment of full-scale CBF systems and limiting the comparability of research findings. To address this issue, this study develops a novel, rigorously derived suite of loading protocols for CBFs subjected to near-field, pulse-like ground motions. Through nonlinear time history analysis of four CBF archetypes of varying heights, five new protocols were developed utilizing different methodologies, each calibrated to a consistent maximum inter-story drift ratio of 0.065 radians. The protocols were then numerically validated against established benchmarks using a high-fidelity finite element analysis of a detailed, full-scale chevron-braced frame. Results demonstrated that while all protocols captured progressive damage accumulation, their destructive potential varied drastically. Protocols derived following Fang et al. methodology induced the most severe damage, surpassing those based on SAC alternatives by precipitating both earlier onset and greater magnitude of structural degradation. Notably, even when protocols share a common derivation methodology, substantial variability in damage outcomes was observed, underscoring the critical role of cyclic sequence and the strategic placement of pulse cycles within each protocol. These findings highlight the paramount importance of both the derivation methodology and the internal sequencing of loading protocols in shaping the cyclic response of CBFs. Key words: Near-field earthquakes, Loading protocols, Concentrically braced frames, Seismic performance, Nonlinear time history analysis, Numerical validation. |
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Link to abstract |
