Seismic performance of CFST piers in two-span continuous girder bridge under multiple earthquakes using endurance time analysis

Abstract

Existing research on the seismic performance of bridge structures predominantly focuses on the effects of the single earthquake, often neglecting the impact of multiple earthquakes. This study aims to address this gap by analyzing the dynamic response characteristics of a two-span continuous girder bridge with concrete-filled steel tube (CFST) piers subjected to multiple earthquakes. A detailed finite element (FE) model of the bridge is developed using solid-shell elements, incorporating a combined hardening–ductile damage model for steel and a confined concrete triaxial plasticity–damage model. Following the principles of the Endurance Time Analysis (ETA) method, two seismic time-history curves are derived from the response spectrum design and used to generate twelve seismic wave inputs. The study investigates the lateral deformation characteristics and damage failure patterns of the CFST piers in the two-span continuous girder bridge under sequential earthquake loading. The findings indicate that: (1) The ETA method provides a novel and efficient approach for studying the seismic performance of structures subjected to multiple earthquakes. (2) For structures already damaged by earlier earthquakes, lateral deformation analysis must account for the peak intensity ratio (β) between successive earthquakes. (3) As earthquake intensity and associated structural damage increase, the threshold value of β required to initiate further damage from subsequent earthquakes decreases, thereby increasing the likelihood of more severe damage.