Structural Deterioration and Time-Dependent Seismic Risk Analysis

Deterioration of built infrastructure is growing into a major cause of concern for countries with a large population of aging structures. Although seismic design standards continue to advance as lessons learned from past events get incorporated, structures designed to older standards are likely to be more vulnerable to damage during earthquakes. The poor seismic performance of older structures is likely to be further exacerbated by advanced levels of structural deterioration, which may be caused due to a variety of processes such as chloride-induced corrosion, alkali-silica reaction, sulfate attack, freeze-thaw cycles, carbonation, and fatigue. However, the effects of long-term structural deterioration have been traditionally neglected in seismic risk assessment.

This report focuses on the development of a comprehensive methodology for the time-dependent seismic risk assessment of structures located in a multi-hazard environment, that can explicitly account for the effects of (1) the time-varying nature of the different hazards, (2) long-term structural deterioration, and (3) cost escalation and the time-value of economic resources on seismic loss and impact estimates.

The methodology for time-dependent seismic risk analysis proposed in this report begins with the PEER framework as a starting point and extends it through the addition of a separate module for time-dependent probabilistic deterioration analysis. Explicitly accounting for deterioration within the proposed framework requires probabilistic models for predicting the time-dependent level of deterioration of struc-tural elements. The steps involved in estimation of the time-dependent degree of deterioration for the case of deterioration in reinforced concrete bridge columns due to chloride-induced corrosion are illustrated in this dissertation, using available empirical models to describe the multi-stage corrosion process.