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Out-of-plane buckling of boundary regions in planar RC structural walls: an approach to prevent instability

Abstract:

Despite the slenderness that usually characterizes planar RC structural walls, these structural elements effectively resist significant in-plane earthquake demands. However, during the 2010 Chile and 2011 New Zealand earthquakes, some medium to high-rise buildings exhibited out-of-plane buckling instability, a failure mode that had only been observed in experiments. This failure mode was first studied in the 1980s; however, it was just after the recent earthquakes that several studies arose to improve design procedures to avoid future damage. Parameters as the height-to-thickness ratio, reinforcement content, material properties, and the hysteretic behavior of the longitudinal steel have been identified as critical for the onset of buckling instability. In this paper, the influence of the concrete cover was studied through a fiber-based element parametric analysis conducted on 120 RC prisms that simulate boundary elements of special RC walls. The prisms were subjected to incremental axial cyclic loading that mimics the effects of in-plane lateral displacements. As a result, a new approach is presented to limit tensile strains developed in the longitudinal reinforcement of boundary zones to prevent the onset of out-of-plane buckling instability.