Validated Lateral Seismic Force-Displacement Backbone Curves for High-Speed Rail Bridge Abutments

Abstract

California’s high-speed rail (HSR) system is slated to traverse nearly the entire length of the state, and thus it will be exposed to seismic risks from almost every known major tectonic fault there. The present study deals with the seismic responses of bridge-abutment transition backfills (BATBs), which are essential components of HSR bridges. BATBs provide a gradual variation of vertical stiffness between the bridge deck and nominal engineered backfill, enabling smooth operations for trains traveling at high speeds. All prior investigations focused on this vertical stiffness in order to better characterize the localized vertical differential movements around BATBs under periodic high axial loads from train sets. Lateral behavior of BATBs, which would be important under seismic loads, has not previously been investigated. The present study offers a parametric nonlinear lateral force-displacement backbone curve for BATBs that is verified against three-dimensional finite-element models and validated against data from large-scale tests conducted at Brigham Young University. The parametric curve takes backwall height as well as abutment skew angle into account.