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<p>This study investigates the seismic resilience of three-dimensional, 10-storey reinforced concrete setback frames retrofitted with nine concentric bracing configurations (XBF, DBF, IVBF, VBF, TMGBF, SMGBF, KBF, ZBF, and MIVBF) under realistic mainshock–aftershock sequences. Nonlinear time-history analyses were conducted using recorded ground motion pairs from the Mammoth Lakes, Chalfant Valley, and Imperial Valley earthquakes with 40-second inter-shock intervals, following the recommendations of previous studies. Modal analysis revealed that braced frames reduced fundamental periods by 44–80% compared to unbraced moment-resisting frames (MRF), with X-bracing achieving the shortest period (1.304&#xa0;s). Under progressive seismic intensities in Chalfant Valley, Mammoth Lakes, and Imperial Valley, the braced systems demonstrated superior performance across all response parameters. X-bracing consistently exhibited the lowest storey displacements (55–200&#xa0;mm vs. 130–600&#xa0;mm for MRF), inter-storey drift ratios (&lt; 0.014 vs. 0.022), and Roof Drift Ratio while maintaining immediate-occupancy performance levels. Plastification analysis confirmed that the braced systems followed a sacrificial two-stage yielding mechanism, wherein the braces absorbed the initial damage before primary frame engagement, contrasting with the immediate beam-column hinge formation in unbraced frames. The findings provide quantitative evidence that strategically positioned concentric braces, particularly X-type configurations, significantly enhance structural stiffness, energy dissipation capacity, and damage localization, offering practitioners validated design guidance for seismic-resilient setback buildings in high-risk zones.</p>

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Seismic performance enhancement of 3D RC setback buildings through concentric bracing systems under sequential mainshock–aftershock loading

  • 期刊论文

  • 发表日期：

    2025年11月17日

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  • Dhiraj D. Ahiwale,
  • Vaishnavi R. Kadam

摘要

This study investigates the seismic resilience of three-dimensional, 10-storey reinforced concrete setback frames retrofitted with nine concentric bracing configurations (XBF, DBF, IVBF, VBF, TMGBF, SMGBF, KBF, ZBF, and MIVBF) under realistic mainshock–aftershock sequences. Nonlinear time-history analyses were conducted using recorded ground motion pairs from the Mammoth Lakes, Chalfant Valley, and Imperial Valley earthquakes with 40-second inter-shock intervals, following the recommendations of previous studies. Modal analysis revealed that braced frames reduced fundamental periods by 44–80% compared to unbraced moment-resisting frames (MRF), with X-bracing achieving the shortest period (1.304 s). Under progressive seismic intensities in Chalfant Valley, Mammoth Lakes, and Imperial Valley, the braced systems demonstrated superior performance across all response parameters. X-bracing consistently exhibited the lowest storey displacements (55–200 mm vs. 130–600 mm for MRF), inter-storey drift ratios (< 0.014 vs. 0.022), and Roof Drift Ratio while maintaining immediate-occupancy performance levels. Plastification analysis confirmed that the braced systems followed a sacrificial two-stage yielding mechanism, wherein the braces absorbed the initial damage before primary frame engagement, contrasting with the immediate beam-column hinge formation in unbraced frames. The findings provide quantitative evidence that strategically positioned concentric braces, particularly X-type configurations, significantly enhance structural stiffness, energy dissipation capacity, and damage localization, offering practitioners validated design guidance for seismic-resilient setback buildings in high-risk zones.