Seismic response of reinforced concrete buildings, considering the effective stiffness in beams, columns and structural walls

Abstract

The Peruvian Technical Standard E.030 for Seismic Resistant Design allows the analysis of the elastic range of buildings, considering gross stiffness. However, Peruvian Standard E060 considers the effects of axial loads, cracked regions in structural elements, and load duration. This research focuses on the impact of incorporating effective stiffness in seismic responses (displacements, drifts, and vibration periods) for six, seven, and eight-story reinforced concrete structures. The study quantifies the increase in seismic responses for design earthquakes and suggests that using effective stiffness in elastic analyses can reduce structural damage. To analyze seismic responses, three buildings of different heights were selected, meeting drift limits established by Standard E.030 using the gross section. Subsequently, twelve structural cases and combinations were created and analyzed in the ETABS program, employing the CQC criterion allowed by Standard E030. Different combinations of effective moment of inertia values for elastic analyses, according to ACI 318 (2014), were used. The study found that the simultaneous reduction of gross inertias of columns, beams, and structural walls led to a 1.2-fold increase in period and a 1.5-fold increase in drift, with variations based on the building's height. In conclusion, it is recommended to consider effective stiffness in elastic structural analyses to minimize displacement damage and ensure better structural performance during severe seismic events.