Assessment of Seismic Vulnerability

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Chapter 1: Introduction to Seismic Vulnerability Assessment
1. Background

Earthquakes and other natural hazards can create disasters of uncontrollable magnitudes when they hit large metropolitan areas. Earthquake risk assessment is used to quantify potential social and economic losses from earthquakes. Risk assessment is an integral part of disaster mitigation. It provides the critical information about on the characteristics of potential disasters in a region and allows planners to identify and prioritize mitigation opportunities. A loss estimation study or risk assessment for a major metropolitan area could take months, if not years to collect the underlying data and would require the participation of experts from several fields, thus limiting the practical application of this technique. Despite their complexity, risk assessment studies have proven to be a very useful tool for developing emergency preparedness plans and for promoting seismic risk mitigation.

With the advances of information technology, it is now possible to overcome the difficulties in data collection and analysis and to significantly improve the efficiency and accessibility of risk assessment techniques. Efficient software applications can now be developed that provide users with options for exploring outcomes from multiple scenarios, displaying output and query results under an easy to use computing environment. With the use of these tools, urban planners, emergency managers, risk managers, and public policy/ decision makers can understand the impact of earthquakes, study the effect of mitigation techniques and incorporate the results into preparedness programs and urban development plans. The potential of expanding the use of risk assessment techniques using the information technology tools to an audience of urban planners and policy/decision makers is critical to creating a dynamic process for integrating earthquake risk evaluations in the management and development of mega cities. Seismic risk requires inputs of exposure, seismic hazard and seismic vulnerability. Seismic hazard is not directly controlled but evaluated from field condition. Exposure is a non engineering concept and depends on the socio-economic background. Vulnerability is directly defined by the ability of building to withstand earthquakes. The ability to assess vulnerability accurately, while ensuring that the resources of time and funds are least strained is the need of the hour for real-time risk assessment over large areas. Bourgeoning urbanization has put ample pressure on the available infrastructure. The scope of earthquake disasters in terms of loss of life and property damage is increasing worldwide due to population explosion and consequent stress on the infrastructure and critical facilities. As a result, the need arises to estimate or model, future earthquake losses, for planning and risk management purposes. Understanding the behaviour of a bulk of structures under earthquake requires the study of vulnerability functions. In this report hitherto existing vulnerability assessment methods for loss estimation are described to give an overview of the state of the art.

1.2 Objectives of the report

This report is an attempt to describe risk assessment and especially seismic vulnerability in accordance with the presently accepted and approved norms. The methodology adopted for risk assessment / loss evaluation is described with due respect to brevity. Fundamentals of vulnerability assessment are discussed in detail. The primary qualitative aspects of the various procedures adopted for the same are highlighted. The report strives to build a foundation for more thorough and technical treatment of the vulnerability assessment, using non-linear static procedures. Non-linear static analysis is a simplified method to find out the structure behaviour beyond the elastic range. It requires careful modeling of the structure to depict the real life conditions...
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