Seismic Collapse Risk Assessment of Low-Aspect-Ratio Reinforced Concrete Structures

Recent research studies have demonstrated that the seismic performance of low-aspect-ratio reinforced concrete shear walls has not been yet adequately quantified to enable robust risk assessment. This is mainly due to the complex nonlinear behavior of such walls (mainly dominated by shear mechanisms) and the wide range of possible wall design characteristics that result in significant discrepancies in their seismic performance. In addition, such walls in industrial and nuclear structures are uniquely designed to have relatively large thicknesses in order to enhance blast and fire protection. Despite such unique configurations and even though an earthquake-related disaster can cause devastation to a country, most North American building codes and design standards do not provide distinctive seismic performance factors for such reinforced concrete shear walls. The objective of the current study is to propose seismic performance factors for low-aspect-ratio reinforced concrete shear walls that mitigate the risk of collapse under the maximum considered earthquake. In this respect, OpenSees was used to develop numerical models to simulate the seismic response of different walls, designed with several configurations under different gravity load levels. The developed models were experimentally validated and subsequently utilized to perform nonlinear static and dynamic analyses following the FEMA P695 methodology, Quantification of Building Seismic Performance Factors. The methodology was used through collapse analyses to assess the adequacy of the proposed seismic performance factors by evaluating the ratio between their median collapse intensity and intensity of the maximum considered earthquake.