Brief Recommendations Addressing RC Buildings Affected by Earthquakes

Abstract

Because of the past experience in Christchurch, New Zealand, where many reinforced concrete (RC) buildings without critical damage have been demolished after earthquakes, and similar events elsewhere, FEMA and ATC are preparing comprehensive guidelines on how to address an RC building after it undergoes strong ground motion. Those guidelines should be the primary resource for practicing engineers wherever building authorities adopt them. The guidelines are being designed to fit well within the regulatory seismic assessment framework used in the United States and are based on terms and methods defined by ASCE (ASCE, 2017). The recommendations presented here are intended to be a simpler alternative that could help engineers elsewhere and expedite the assessment of RC buildings after a strong earthquake. These are the opinions of the writers. Previous research by Cecen (1979), FEMA 307 (1998), Shah (2021), Monical (2021), and ATC (2021) has shown that well-detailed RC buildings can survive repeated earthquakes without negative changes in performance as long as the effects of the initial motion(s) are limited to flexural cracking, shear cracking controlled by transverse reinforcement, and flexural yielding. These phenomena a) tend not to cause reductions in structural resistance and, consequently, b) tend not to cause increases in earthquake deformation demands either. Nevertheless, after every strong earthquake, scores of RC buildings are questioned throughout the world, even in the absence of critical structural damage. At the same time, too many RC buildings around the world end up being demolished because of earthquake damage to facades, partitions, finishes, and other non-structural building components. These recommendations are presented here as a simplified approach and an alternative to address both of these problems. The recommendations include building interventions of different natures and extents to address both brittle and ductile existing buildings and consider the implications of initial damage on the future performance of both the structure and non-structural components. © 2024, International Association for Earthquake Engineering. All rights reserved.