Effect of seismic degradation on the fragility of reinforced concrete bridges

• The paper develops models for seismic degradation of RC bridge columns.
• The degradation in static pushover properties and deformation capacity is modeled.
• The vulnerability of an example RC highway bridge is assessed using the models.
• It is found that seismic degradation can increase the vulnerability of RC bridges.

In seismic regions, structures are likely to experience multiple seismic events during their service lives. As a result, the seismic reliability of structures may degrade from the design standard with each passing earthquake. Therefore, there is a need to investigate the effect of seismic degradation on the reliability of structures in subsequent earthquakes. In the existing literature, performance of RC structures under a sequence of earthquakes has received limited attention. More work is required to understand the effects of seismic degradation mechanisms in different structural systems.This paper investigates the seismic degradation of reinforced concrete (RC) highway bridges and the effect of degradation on the performance and reliability of bridges subject to future seismic events. In particular, the focus is on the degradation of bridge columns that are typically the primary lateral load resisting components in highway bridges. For this purpose, probabilistic models are developed to predict the effect of past earthquakes on the structural properties of RC bridge columns and their steel reinforcement. The proposed models are assessed using seismic degradation data generated through nonlinear time history analyses of RC bridges subject to ground motions obtained using detailed finite element (FE) models. The developed degradation models are then used to assess the effects of seismic degradation on the seismic vulnerability of an example RC highway bridge with one single-column bent. The results show that seismic degradation in RC columns can significantly increase the seismic vulnerability of RC highway bridges.