Seismic isolation of a highly skewed, prestressed concrete girder bridge.

摘要

A relatively new approach for designing or retrofitting highway bridges in seismic zones involves isolating the superstructure from the substructure. Through experimental and analytical investigations, this study evaluates the effectiveness of isolating one particular bridge: a highly skewed, prestressed concrete, slab-on-girder bridge.;Dynamic testing of the bridge was performed using the pullback, quick-release method. Several new developments facilitated the quick-release testing. A simple, new quick-release mechanism was designed, constructed, and tested at the University of Kentucky. Also, a new method of attaching the pullback cable to the bridge was developed. This research represents the first use of pullback, quick-release testing of a highly-skewed, prestressed concrete, slab-on girder bridge.;A three dimensional finite element model of the bridge was created. It was refined, or calibrated, to match experimentally determined natural frequencies and mode shapes. An optimization program was written to adjust specific model variables within pre-defined limits. This automated, systematic, optimization of model parameters produced an accurate analytical representation of the bridge.;Time-history analyses were conducted for the seismically isolated bridge model and an identical, non-isolated bridge model. Site-specific acceleration records were used in the time-history analyses. These theoretically sophisticated earthquake simulations coupled with a model calibrated to experimental evidence, yield reliable results. For the bridge considered, seismic isolation was found to appreciably reduce forces that the bridge substructure and foundation must resist.