Compression failure of thin concrete walls during 2010 Chile earthquake: lessons for Canadian design practice

Abstract

Numerous thin concrete walls failed in compression during the 2010 Chile earthquake. Experiments on small wall elements indicate that thin concrete walls without tied vertical reinforcement may fail very suddenly at uniform compression strains as low as 0.001 due to the thin layer of concrete between two layers of reinforcement becoming unstable. A test on a wall subjected to axial compression and strong-axis bending demonstrated that unlike a tied column, a thin concrete wall can suddenly lose all axial load-carrying capacity. Nonlinear response history analysis of a typical Chilean high-rise shear wall building indicates small global drift demands and correspondingly small curvature and compression strain demands when subjected to the ground motions measured in Santiago, which explains why most buildings were not damaged. Nonlinear finite element analysis of a typical wall step-back irregularity indicates the increase in maximum compression strains due to a reduction in wall length is much larger than predicted by a sectional analysis. Based on all the results of the current study, a number of significant changes are proposed for the 2014 edition of CSA A23.3 to avoid compression failures of thin concrete walls, including limiting the axial compression force applied to thin bearing walls, accounting for unexpected strong-axis bending of thin bearing walls, and limiting the compression strain demands on thin concrete shear walls.