PRESENTATION – Seismic Performance of Shear Wall Buildings

When – Monday 11 November 2013

Presentation from Professor Elwood:

Architectural features and other irregularities in the gravity system which apply gravity-induced lateral demands to the seismic force resisting system are being incorporated in new buildings. These gravity-induced demands have raised concerns, due to the perceived potential for a ratcheting effect to occur during seismic loading. 

Such gravity-induced lateral demands existed in the Hotel Grand Chancellor in Christchurch due to the cantilevered gravity system on the east side of the building.

This presentation summarizes the results of a study to identify if there are behavioral trends related to such irregularities in the gravity system not currently recognized within the scope of current building codes. To this end, a nonlinear, parametric study was conducted to investigate the inelastic response of concrete shear wall buildings with a range of design characteristics, including gravity-induced lateral demands. The results demonstrated that a seismic ratcheting effect can develop and amplify inelastic displacement demands. The effect is significantly more prevalent in coupled shear walls compared with cantilevered shear walls. An irregularity class to address buildings with gravity-induced lateral demands on the seismic force resisting system is proposed for the next edition of the National Building Code of Canada.