Seismic fragility analysis of medium-rise reinforced concrete wall buildings

Abstract

This paper presents a seismic fragility assessment of medium-rise reinforced concrete (RC) wall buildings, focusing on buildings with thin unconfined RC walls subjected to high axial loads that are representative of typical residential buildings in Chile and other seismic countries. Finite element models of three index buildings with different levels of axial load were developed using the software DIANA. Nonlinear time-history analyses were performed to estimate the engineering demand parameters (EDPs) for each index building through a multiple stripe analysis. Finding that existing fragility models did not well capture the damage in these buildings, global and local EDPs were examined, proposing simple relationships between the two, and recommending new damage limit states better aligned with the expected and previously observed damage of this typology. The proposed damage limit states are lower than those available in the literature for global EDPs and larger than those available for local EDPs. Due to the characteristics of the buildings examined, i.e., buildings with flag-shaped walls, high axial loads, and brittle behavior, damage can occur at lower global EDPs but larger local responses such as total hinge rotations at the critical sections. This study additionally shows seismic fragility curves for the three index buildings using the global and local EDPs and the proposed damage limit states. The fragility curves display the same probability of exceeding a damage limit state for the same building, whether developed using local or global EDPs. On this basis, it can be concluded that the damage limit states proposed can be used to reliably obtain analytical fragility curves for medium-rise RC wall buildings with configurations similar to the one considered in this paper.