Publication Abstract

Proceedings of the 37th Annual Conference on Deep Foundations, 2012, Houston, TX, USA, (DFI)

Dynamic Analysis of a Base-Isolated Bridge, Seattle, Washington
Jeremy Butkovich, Hollie Ellis, Bill Perkins, Paul Bott, Greg Nutson

Dynamic soil-structure interaction (DSSI) analyses are becoming more common in bridge designs, especially in seismically active areas. Because of its proximity to two active fault zones, the Evergreen Point west approach bridge replacement will be base isolated, and will be designed using DSSI. The project team completed two independent bridge designs to satisfy peer review requirements. The designs required substantial characterization of the soil dynamic behavior using both laboratory and in-situ testing. The analyses made use of earthquake time histories spectrally matched to conditional mean spectra. This led to reduced, and more realistic seismic demands on the structure, compared to conventional uniform hazard spectrum matching. The bridge analyses suggest that the preliminary bridge design is relatively conservative. This will allow the design team to potentially reduce shaft/column diameters and reinforcement. The design team estimates that the dynamic analysis design could represent a net savings of around $60 to $90 million compared to a conventional design.

 article #1863; publication #99 (AM-2012)