Pullback Testing of Seismically Isolated P/C I-Girder Bridge

Abstract

Dynamic testing was performed on a highly skewed, three-span, seismically isolated, prestressed concrete, slab-on-girder bridge. The pullback, quick-release method of testing was used, a first for this bridge type. Several new developments facilitated the quick-release testing. A simple new quick-release mechanism was employed with relatively low lateral test force. Also, a new method of attaching the pullback cable to the bridge was implemented. After testing, a three-dimensional finite element model of the bridge was created. An optimization program was used to refine, or calibrate, the model to match experimentally determined natural frequencies and mode shapes. This automated, systematic optimization of model parameters produced an accurate analytical representation of the bridge. Mode shapes and frequencies from the experimental and analytical investigations are presented.