Life-cycle seismic fragility and resilience assessment of aging bridges using the endurance time method

This paper presents a framework based on the endurance time (ET) method to evaluate bridge seismic fragility and resilience in the life-cycle context by considering corrosion effects. The ET method has been widely used for seismic analysis of structures in recent years due to its high precision and low computational effort. However, the traditional ET method does not provide any information about the dispersion of seismic responses and can only predict the median of responses. Therefore, a framework for quantifying the record-to-record (RTR) uncertainty through the ET method is proposed. Firstly, a three-dimensional finite element model of a three span bridge in OpenSees was constructed and subjected to the ET intensifying functions. The proposed methodology was then applied to predict the bridge's probabilistic seismic response distribution. The results were compared with those obtained using incremental dynamic analysis (IDA) as a benchmark method. It was demonstrated that the proposed methodology can significantly reduce computational costs while maintaining acceptable seismic response accuracy (both median and dispersion). Next, the life-cycle fragility and resilience of the bridge were evaluated considering the chloride-induced corrosion effects using the proposed framework, which may be challenging to address using the IDA method due to its time-consuming nature. The results show that the seismic resilience decreases, whereas the uncertainty increases with the increasing seismic intensity and age of the bridge. Therefore, it is of great importance to incorporate aging effects into an accurate evaluation of bridge resilience.