A holistic framework for seismic analysis of extended pile-shaft-supported bridges against different extents of liquefaction and lateral spreading

Abstract

This paper proposes a holistic framework for seismic analysis of extended pile-shaft-supported bridges experiencing different extents of liquefaction and lateral spreading. To this end, an excess-pore-pressure-ratio-based novel liquefaction severity index (LSIru) that explicitly accounts for liquefaction extents over the depth of soil profile is proposed to classify liquefiable ground into three levels, namely minor, moderate, and severe. For the ease of LSIru calculation, a regression function is developed to map LSIru with soil profile and seismic motion properties. Also, the popular Ishihara-inspired liquefaction potential index (LPIISH) is incorporated into the framework, as an alternative option, for the liquefaction level evaluation, where LPIISH thresholds for the three liquefaction levels are proposed in this study. To develop simplified analytical methods for different liquefaction levels, the separate effect of liquefaction and lateral spreading on multiple bridge demand parameters are quantified, including the maximum bearing displacement, column displacement, and pile curvature ductility. Results show that the effect of liquefaction on the examined demand parameters is generally slight regardless of liquefaction levels, whereas the effect of lateral spreading is significant on column displacement and pile curvature responses for the moderate and severe liquefaction levels, but negligible for the bearing displacement at any levels. The developed holistic framework and analytical methods provide an applied solution to seismic analyses of extended pile-shaft-supported bridges against liquefaction and lateral spreading, within the considered scenarios of soil-bridge systems.