Issues in seismic risk assessment of transportation networks

Abstract

Seismic risk assessment of transportation networks has been the subject of several studies over the past two decades. Many advances have been made during this time, however, numerous issues remain. Recent research addressing some of these issues has demonstrated their importance for rational decision making. In this paper an overview is presented of the most commonly used transportation network risk assessment methodology. Important issues that have received limited attention over the years are identified and recent developments to address these issues are presented. The paper draws on research conducted under the Pacific Earthquake Engineering Center with many contributors (Moore et al., 2005; Fan and Nie, 2006; Kiremidjian et al., 2003; Lee and Kiremidjian 2006; Stergiou and Kiremidjian, 2006). Formulations for network functionality loss under a scenario event and for a suite of possible earthquakes that can affect the system are developed first. It is shown that functionality loss is not only an important part of the risk assessment, but is of the same order of magnitude and in some cases is greatly exceeded than the loss from direct physical damage to network components. Liquefaction appears to be the most important hazard in the loss computation for such systems; however, more robust models are needed to determine the degree to which liquefaction dominates the risk. Correlation of ground motion between bridge sites and correlation of damage between bridges with comparable designs are often ignored in transportation risk analysis. It is again demonstrated that these correlations are important contributors to the uncertainty of loss. When the risk from all earthquakes events is considered, network functionality analysis becomes computationally intractable. A simple method based on Monte Carlo simulation with importance sampling is presented for that purpose. The various conclusions are illustrated through an application to a sample network within the San Francisco Bay region. © 2007 Springer.