Contribution of coupling elements to the seismic axial load demands in walls of reinforced concrete buildings

Abstract

Studies on resisting planes of reinforced concrete (RC) buildings damaged during recent earthquakes in Chile and New Zealand suggest that the behavior of structural walls was highly influenced by the interaction of the resisting plane with the rest of the structure. High levels of axial load have been identified as one of the principal causes of the observed wall damage on these buildings, and that a significant amount of such load comes from the seismic demands. This paper estimates the seismic axial load demand in walls of three RC buildings. Additionally, the effects of the slab stiffness on the seismic demand of these walls is investigated. The responses of the buildings are obtained from detailed linear finite element models in ETABS using reduced elements stiffness to account for the nonlinear behavior. Two different slab stiffness are used to simulate different cracking levels on these elements. From these analyses, an estimation of the height-wise contributions of coupling elements to the seismic axial load in walls is obtained, identifying the participation of slabs, beams and adjacent walls. The results show that slabs have the largest contribution to the seismic axial load in walls, contributing between 90% and 270% of such load. These findings suggest that the effective stiffness of slabs in RC wall buildings must be revised and that future research on this topic requires modelling the slabs as nonlinear elements.