Paradigm shift to resilience based design for improved seismic behaviour – State-of-the-Art

Abstract

Seismic design codes have evolved over time, with a significant shift from the existing force-based design (FBD) to the performance-based design (PBD) approach. This shift was predicated on the improved understanding from recent research and observation of building damage after earthquakes. Currently, code requirements and design recommendations are set considering life safety criteria. Consequently, they do not limit damage to the structure and its components (structural/non-structural parts). This may lead to higher repair costs in the event of strong shaking. Experiences from past earthquakes demonstrate that buildings built using the existing FBD sustain severe damage, although most buildings did not collapse, thereby ensuring life safety. The substantial economic loss following earthquakes led to the development of a new design philosophy based on target performances called PBD. Like the FBD, the PBD ensures life safety (based on strength and ductility). In addition, the PBD can address the need for immediate damage assessment and limiting economic losses. However, PBD may not prevent damage to primary structural/non-structural parts (serviceability). This, in turn, leads to higher repair costs and operational downtime and may lead to abandoning the building. Several attempts were made to minimize the functionality loss of structural and non-structural elements following earthquakes. These efforts culminated in the emergence of a resilience-based design (RBD), which aims to mitigate the economic damages due to (a) severe building damage, (b) functionality loss, and (c) business downtime. RBD is a holistic design approach that defines building’s performance points considering immediate occupancy criteria and building functionality. Moreover, the RBD considers the total cost of the building as one of the design parameters. The RBD is expected to surpass code-intended performance targets and typical performance-based design practices in the near future. Given the importance of RBD, the paper explores the following: (a) implications of damage and the importance of the built environment, (b) evolution of seismic design of buildings, (c) the need to shift from PBD to RBD, (d) quantification of resilience, and (d) the necessity for resilient systems based on the real-time scenario.