The transverse response of short bridges is often critical to their seismic performance. When
transverse displacements are large, damage to substructure columns may occur, often in the form of
plastic hinges, shear failures, or lap splice failures. A significant component of the transverse response is
due to the dynamic response of the embankment. Current design provisions (ATC-32 1996, Caltrans
1999) neglect this contribution entirely, and other researchers have only investigated linear models of
embankment contribution (Wilson and Tan 1990; Werner et al. 1993; Goel 1997). This report focuses
on the modeling of short bridges to improve estimates of column displacement demands. In particular,
improved approach-embankment models are developed based on seismic response data recorded at
two short bridges in California. The models are nonlinear and can be used in conjunction with software
programs such as DRAIN-2DX and DRAIN-3DX. One model explicitly considers the piles and
embankment soils, while a second, simpler, model considers only the embankment soils. Both models
are calibrated to the recorded California bridge data. The more complex model is used to generate
response data for representative Illinois bridges, and this data is used to calibrate the simpler model for
Illinois bridges.
Furthermore, when transverse demands are excessive, one mitigation technique is the use of
conventional elastomeric bearings to seismically isolate the superstructure. Nonlinear models for
Illinois Type I, II and III elastomeric bearings are developed. The effectiveness of the bearings for
reducing column displacement demands is addressed by analytical studies. These studies consider
potential effects of cold temperatures on bearing stiffness.National Science Foundation EEC-970178
