UCLA

Studies recently conducted by the authors and others have demonstrated that relatively simple equivalent-static analysis (ESA) procedures can adequately predict the response of bridge foundations to lateral spreading for design purposes assuming that the lateral spreading displacement demand is known or can be estimated. However, an important aspect of the analysis that remains to be addressed is how to account for the restraining force provided by foundations when the laterally spreading ground does not have a finite, measurable out-of-plane width. This study addresses this problem in the context of two parallel, adjacent bridges crossing the Colorado River in Mexico that were subjected to a broad field of laterally spreading ground during the 2010 Mw 7.2 El Mayor- Cucapah earthquake. Two-dimensional finite element analyses (FEA) are used to quantify the influence that the presence of each bridge had on the lateral spreading demand for the opposite bridge. The results show that the relatively stiff foundations of the first bridge provided a 'shielding' effect to the second bridge, significantly reducing the demand compared to the magnitude of the free-field lateral spreading observed at the site.