Drift-based risk-oriented method for the explicit consideration of ground motion duration in seismic design

This study proposes a method to explicitly account for ground motion duration in seismic design by modifying structural deformation capacity. An equation is presented to adjust the design drift limit prescribed in the New Zealand standard NZS 1170.5, based on the anticipated reduction in structural deformation capacity for ground motion durations longer than a critical value. The proposed relationship is used to derive designs corresponding to three duration targets each for two case-study steel moment frame buildings - a 4-storey and a 12-storey, located on a site in Nelson, New Zealand. Hazard-consistent collapse risk assessment of the design versions is conducted using a structural reliability framework employing incremental dynamic analysis. Results indicate that buildings designed for lower drift limits have a lower mean annual frequency of collapse. The application of the proposed method is found to reduce the variation in the collapse risk of steel frame buildings designed for different duration targets, compared to the existing approach. The method proposed in this study is simple and easy for practical applications and can be modified for other design codes and a range of structural typologies.

Automated summary

This study proposes a method to explicitly consider ground motion duration in seismic design by modifying structural deformation capacity. An equation is presented to adjust the design drift limit prescribed in the New Zealand standard based on the anticipated reduction in structural deformation capacity for longer ground motion durations. The proposed method reduces the variation in collapse risk for different duration targets and can be easily applied to other design codes and structural typologies.