Seismic performance and functional recovery of dual lateral load resisting system comprising of coupled structural walls and moment resisting frames

The Coupling Ratio (CR) is one of the critical parameters for the design of coupled structural wall (CSW) systems. CR is defined as the proportion of lateral load resisted by the coupling beams relative to the total overturning moment resisted by CSW system. Previous studies recommend an optimal CR range of 30–70%, but these findings are largely based on isolated CSW systems. Consequently, the recommendation is not applicable for dual lateral load-resisting systems wherein the lateral loads are shared between moment resisting frames (MRFs) and CSW systems. For such dual lateral load-resisting systems, the CSW and MRFs are designed to resist the fraction of lateral load demand imposed on them. The demand, estimated during the analysis and design stage, depends on the initial elastic lateral stiffness of the system. However, during earthquakes, significant redistribution of lateral load may occur depending on the location and mode of damage to structural elements. This redistribution of forces may lead to undesirable performance during an earthquake. This underscores the need to establish optimal CR values for dual systems to ensure reliable seismic performance considering seismic performance at the building level. Again, with growing emphasis on post-earthquake functionality and resilience, it is equally important to understand how CR influences not only strength and ductility but also repairability, downtime, and economic loss. Thus, this study examines the effect of CR on the seismic performance of reinforced concrete CSW buildings designed as per Indian Standards. Three building configurations (10-, 12-, and 16-storey) are analyzed with CR values of 40%, 50%, and 60% using nonlinear static analyses. Performance metrics include fundamental period, base shear–drift capacity, inter-storey drift distribution, and ductility demand. Further, damage and loss assessments are undertaken across multiple peak ground acceleration (PGA) levels to quantify resilience. The results provide key insights into the role of coupling ratio in enhancing both seismic performance and resilience, offering practical guidance for the design of dual lateral load-resisting systems.