Integrated approach between seismic resilience and vulnerability indexes with regularity index for vertical irregularity planar frames risk assessment

Most international design standards prohibit or necessitate alternative seismic analysis and design for building frames having vertical irregularities. Nevertheless, the irregularity quantifiers provided by design guidelines and research studies do not appear to be strongly correlated with seismic impact risk. It is universally believed that regular buildings have a strong fundamental mode contribution to their seismic behaviour, and as the irregularity of the structure increases, the participation of higher modes increases. Four types of vertically irregularity buildings have been chosen in this study; Geometric Irregularity (GI), In-Plane Discontinuity (ID), Stiffness Irregularity (SI), and Mass Irregularity (MI). This study attempts to investigate the correlation between the regularity index (RI) with respect to seismic resilience index (SRI), seismic vulnerability index (SVI), and fragility functions for the selected buildings using non-linear dynamic and static analysis. The results of seismic risk analysis including (SVI, SRI, and fragility function) shows building frame with in-plane discontinuity (ID) to be more vulnerable and the highest risk among the selected structures. However, the outcomes of the regularity index clarifies that the geometric irregularity (GI) is the most irregular structure, followed by in-plan discontinuity (ID) frame structure. On the other hand, the geometric irregularity building performs even better than the regular building. Eventually, the framing sequence of the structural types in terms of their seismic resilience and their ability to withstand seismic movement are consistent with the seismic vulnerability index and the fragility functions (ID < SI < MI < R < GI). Accordingly, to regularity measures, the SRI does not correlate with the regularity index, as well as with SVI, and lastly with the Vulnerability Index obtained from the Nonlinear-Static Analysis (NL-SA), VINLSA.

Automated summary

Most international design standards have restrictions or requirements for seismic analysis and design of building frames with vertical irregularities. However, the existing irregularity quantifiers do not show a strong correlation with seismic impact risk. This study investigates the correlation between regularity index and seismic resilience index, seismic vulnerability index, and fragility functions for four types of vertically irregular buildings. The results show that building frames with in-plane discontinuity are the most vulnerable and have the highest risk among the selected structures.