Optimal intensity measures for seismic fragility assessment of corrosion-damaged RC bridge piers

This study aims to determine probabilistic seismic demand-based optimal intensity measures (IMs) for seismic fragility evaluation of corrosion-damaged reinforced concrete (RC) bridge piers. Toward this goal, a methodology is presented to select optimal IMs based on four criteria: efficiency, practicality, proficiency and sufficiency. Thirty-eight intensity measures in five categories of (i) acceleration-related, (ii) velocity-related, (iii) displacement-related, (iv) hybrid, and (v) general IMs are studied. The methodology is demonstrated in a case study of an RC bridge with various corrosion levels. The finite element model of a reference bridge pier is developed and verified by experimental results. Incremental dynamic analyses (IDAs) are carried out on the studied corrosion-damaged bridge piers using 22 ground motion records selected employing the conditional mean spectrum (CMS) methodology. The outcomes of IDAs are then used to develop linear probabilistic seismic demand models (PSDMs) for each bridge pier with varying corrosion damage. The obtained results show the high sensitivity of optimal IMs on the corrosion level of RC bridge piers. For instance, while the optimal IMs for the pristine bridge pier are sustained maximum acceleration (SMA) and effective peak acceleration (EPA), for the severely corroded pier peak ground acceleration (PGA) and acceleration level containing up to 95% of the Arias intensity (A95) are the most optimal IMs.