Equivalent Static Analysis of Piled Bridge Abutments Affected by Earthquake-Induced Liquefaction

Deformation of bridge approach embankments caused by earthquake-induced liquefaction in the underlying soils can impose large force and displacement demands on the piled abutments. An equivalent static analysis (ESA) procedure that accounts for the beneficial coupling of the embankment displacements with the mobilized bridge/pile restraining forces is evaluated against the results of three centrifuge tests involving three nonpiled embankments and three piled embankments. The centrifuge tests, which showed that the restraining forces from the different pile configurations reduced the embankment displacements by 20-80%, relative to those of the nonpiled embankments, are briefly summarized. The ESA procedure is described and applied to the centrifuge tests using different sets of input parameters to isolate the questions of how well liquefaction-induced displacements are estimated for embankments without piles, and how well the relative pile pinning effects are estimated. The results of nonlinear deformation analyses (NDAs) of the same centrifuge tests are compared with those from the ESAs and are used to illustrate important differences in their capabilities. The relative merits of the ESAs and NDAs for evaluating the performance of pile abutments affected by liquefaction are discussed. (C) 2014 American Society of Civil Engineers.