Effectiveness of Seismic Isolation of Highly Skewed P/C I-Girder Bridge

Abstract

Experimental and analytical investigations were conducted to evaluate the effectiveness of isolating the superstructure from the substructure of a highly skewed prestressed concrete slab on a girder bridge. Dynamic testing of the bridge was performed using the pullback, quick-release method. A 3D finite elemental model of the bridge was calibrated and refined to match experimentally determined natural frequencies and mode shapes. Time-history analyses, using site-specific acceleration records, were conducted for the seismically isolated bridge model and an identical nonisolated bridge model. Seismic isolation was found to appreciably reduce forces that the bridge substructure and foundation must resist. When compared to the nonisolated bridge for the design earthquake (or 50-year event), the maximum pier moments were reduced between 32% and 62%, and the maximum shears were reduced between 30% and 66%.