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. 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. Time-history analyzes, using site-specific acceleration records, were conducted for the seismically isolated bridge model and an identical, non-isolated bridge model.
For the bridge under consideration, seismic isolation was found to appreciably reduce forces that the bridge substructure and foundation must resist. Seismic design forces for pier columns were reduced between 43% and 86%. The results of this study clearly show that seismic isolation is an effective means of reducing earthquake forces on bridges.
Digital Object Identifier
Robson, Bradley Neil; Harik, Issam E.; and Allen, David L., "Seismic Isolation of a Highly Skewed, Prestressed Concrete Girder Bridge" (1998). Kentucky Transportation Center Research Report. 347.