Chapter 1 - A Risk Index for Mitigating Earthquake Damage in Urban Structures

Abstract

Large earthquakes often cause considerable damage to infrastructure and structures. Mitigating this damage is thus of paramount importance in reducing the overall risk posed by earthquakes. Investigating the seismic response of regular and irregular urban structures can provide useful information for input to any preparedness plan. The level of damage sustained is usually presented via a damage index (DI) and can be expressed qualitatively or quantitatively. While the qualitative-based indices are often easy to use, they might not be sufficiently accurate, and thus, the outcomes cannot be used with certainty when adopting a predisaster mitigation strategy. Quantitative-based indices, by contrast, often provide rigorous results. However, the process is usually very time-consuming and it is necessary to have detailed information at both structural and regional levels, and this information is often difficult to access. Also, quantitative DIs provide neither information regarding the probability of failure nor a graphical illustration of the damage sustained by a building. These limitations can be addressed by the use of fault-tree analysis (FTA) as a functional tool. On the one hand, it can provide a graphical illustration of the extent of damage, and on the other hand, it can also quantify the probability of failure (Ericson, 1999). In addition, FTA allows for the determination of the reliable parameters to improve the safety of a structural system.