Seismic performance of reinforced concrete structural systems under mainshock–aftershock sequences: insights from the 2023 Türkiye–Syria earthquakes

Abstract

This study investigates the seismic performance of reinforced concrete buildings subjected to realistic mainshock–aftershock earthquake sequences using strong-motion records from the 2023 Türkiye–Syria earthquakes, addressing the limitation of conventional seismic design approaches that primarily consider single-event loading and may not capture cumulative damage effects. Six mid-rise prototype buildings representing moment-resisting frame and dual system were designed in accordance with three generations of Turkish Earthquake Code (TEC-1975, TEC-1998/2007, and TEC-2018). Nonlinear time-history analyses were performed by sequentially applying recorded ground motions while preserving cumulative damage and residual structural states, thus enabling explicit simulation of damage accumulation across successive events. Structural performance was evaluated in terms of global stability, element-level damage, residual displacements, inter-story drifts, the reduction of the system stiffness and standard performance limits. The results show that although code evolution improves overall seismic behavior, modern code compliance does not consistently ensure satisfactory performance under mainshock–aftershock loading. All models maintained global stability; however, several exceeded Collapse prevention (CP) limits, particularly under aftershock-dominant sequences. Residual displacements remained relatively limited under mainshock-dominant loading (generally below approximately 100 mm for MF systems and about 10–12 mm for DS systems), but increased significantly under aftershock-dominant scenarios, reaching approximately 150–260 mm in MF systems and remaining below approximately 30 mm in DS systems. In addition, stiffness degradation exceeded approximately 40–60% in several cases, indicating substantial cumulative structural deformation. Dual systems reduced damage concentration and residual displacements under mainshock-dominant excitation, but their relative advantage diminished when stronger aftershocks followed prior inelastic damage, in some cases resulting in less favorable performance than moment-resisting frames. Significant residual displacements were observed even in TEC-2018-compliant buildings, indicating limitations of current design provisions in controlling post-earthquake functionality. The findings highlight the need for sequence-aware, performance-based seismic design approaches that explicitly account for cumulative damage and residual deformation demands.