UCLA

Three bridges supported on deep foundations that exhibited various performance levels in liquefied and laterally spreading ground are analyzed using a beam on nonlinear Winkler foundation method. The performance levels were (1) no measurable foundation deformation, (2) moderate damage, and (3) collapse. Analyses are first performed using the best available information regarding ground motions and free-field lateral spreading surface displacements. Predictions closely match observations when the inputs are well known. The cases are subsequently reanalyzed using a probabilistic forward prediction that incorporates uncertainty in the ground motion, liquefaction triggering evaluation, lateral spreading surface displacement, and structural response. Significant differences in lateral spreading displacements estimated by different methods introduced significant dispersion into predictions of structural response for cases of poor performance in which the piles moved with the spreading soil but had little influence for cases with good performance where the liquefied soil spread around a stiffpile foundation. © 2013 American Society of Civil Engineers.