A new shear key for rocking timber shear walls

Abstract

Allowing shear walls to rock is one way of protecting structures from earthquake damage, or at least minimising this damage. Walls allowed to rock must have the ability to resist both overturning moment, and lateral forces. While resistance to overturning is typically provided by self-weight, post-tensioned cables, and/or damping devices acting as hold-downs, a particular challenge is to provide adequate resistance to lateral forces, which will not interfere with, nor disturb the function of the devices chosen to resist overturning. During an earthquake, there will typically be high contact forces between the shear keys and shear walls. Friction induced by these contact forces can add to the moment resistance against overturning – often in an unpredictable way.

While supplemental moment resistance could be considered a desirable outcome in the case of non-rocking walls; in the case of rocking walls, their load limiting ability could be compromised. A new shear key concept, that is both simple and economical, is proposed and implemented at the bottom centre of an experimental timber wall that is allowed to rock. Under loading, the shear key performed as intended, providing adequate lateral resistance, while at the same time allowing the wall to rock in the intended manner.