Investigation of the Axial Load Capacity for Lightly Reinforced Wall Piers

A large number of reinforced concrete buildings constructed prior to the mid-1970s in western North America rely on lightly reinforced, perforated, perimeter shear walls to resist earthquake-induced lateral forces. Although a substantial number of piers may exist, deformation demands can significantly exceed acceptable levels for plastic deformations published in common acceptance criteria such as FEMA 356. A shear-friction model is used to establish the ability of wall piers to support vertical loads after substantial loss of pier lateral-load capacity. The model results indicate that typical wall piers are capable of sustaining relatively large lateral drift ratios prior to loss of vertical load-carrying capacity, which is consistent with postearthquake observations. However, preliminary test results indicate that the drift capacity may be substantially less for poorly detailed walls, where axial failure occurred at a lateral drift ratio of approximately one percent.