Performance of Seismically Isolated High-Speed Railway Bridges against Near-Fault Ground Motions

Abstract

The first high-speed rail (HSR) corridor in India, built on viaducts and bridge structures, is currently under construction between Mumbai and Ahmedabad. This corridor passes through seismic Zone III, whereas future corridors are planned to be constructed in Zones IV and V of the Indian seismic codes. It is challenging and uneconomical to achieve the seismic performance goals of HSR bridges through conventional seismic design measures in higher seismic zones. Seismic isolation technology, which has been successfully deployed for seismic safety of highway and railway bridges in the past, may also be utilized for HSR bridges. However, the HSR bridges have stringent serviceability requirements through limits on deck end rotations (in-plane and out-of-plane), mid-span deflection (in-plane), deck acceleration, and rail stresses. These response parameters in seismically isolated HSR bridges are sensitive to near-fault ground shaking with large amplitude velocity pulses and the presence of low-frequency excitations.

This paper investigates the seismic response of a seismically isolated three-span continuous HSR bridge subject to near-fault ground shaking. A three-dimensional nonlinear finite element model, incorporating track-structure interaction, is developed to compare the seismic performance of the seismically isolated bridge to three ground motions such as far-fault, near-fault pulse type, and near-fault non-pulse type. The ground motions were scaled to the target spectra using amplitude and spectrum matching scaling procedures. The ground motions with pulse characteristics resulted in smaller forces and moments in the piers due to higher participation of the isolation mode. The scaling procedure had minor influence on the response quantities, expect for pier forces and isolator displacements under near-fault non-pulse ground shaking.