Elastic overstrength of reinforced concrete shear wall buildings in Chile

Abstract

The overstrength is a key property of engineered building structures, and its beneficial effects have been recognized in several studies. When ground accelerations are higher than those specified in seismic design codes, the overstrength helps prevent the collapse of buildings but not necessarily the occurrence of some structural damage. However, during the 2010 Chile earthquake (MW 8.8), 90% of buildings in the affected regions showed no damage at all, despite recorded ground accelerations higher than those required by the Chilean seismic code. Many studies about damaged structures have been performed, and some of them have pointed out the need for research on undamaged buildings as well. Besides, no study has focused on the overstrength of Chilean buildings considering their particular design conditions and seismic hazard. In order to fill these gaps, this study defines the elastic overstrength and evaluates such quantity in actual reinforced concrete shear wall buildings that suffered no damage in the 2010 earthquake even though they were subjected to seismic demands greater than those specified by the seismic design code. Three buildings of 5, 17 and 26 are evaluated based on nominal, linearly elastic analysis. Possible influence of issues such as material strength and modeling assumptions were evaluated. Results show that the 5-story building is able to stand undamaged ground accelerations that are up to 3 times larger than those required by the Chilean seismic code, which explains the lack of damage in this building. On the other hand, however, results also indicate that the other, higher buildings should have suffered important damage, i.e., the elastic overstrength was not found to be large enough to explain the lack of damage in these buildings.