Autore: Gianluca Panasiti
Prodotto: Midas GEN
A natural disaster on a facility plant, storing or processing dangerous substances, can lead to the release of those hazardous substances with possible severe consequences through toxic-release, fire or explosion scenarios. Accidents triggered by a natural hazard, such as earthquake, involving release of dangerous substances are commonly referred to as Na-Tech events (Natural Hazard Triggering Technological Disasters). Therefore, the evaluation of the seismic risk of an establishment with major-accident hazards under seismic loading is an important task in order to evaluate the most critical components and, if necessary, to intervene with appropriate mitigation systems.
Accordingly, the objective of this study is the risk assessment of the most critical components of a major-hazard plant located in a seismic prone area. Here, the seismic risk is expressed in in terms of the mean annual frequency of exceeding the desired limit state. The mean annual frequency will be calculated with a closed-form equation, based on an analytical representation of the seismic hazard and fragility analysis of the equipment. This expression is derived by considering the seismic hazard, structural response (as a function of the ground motion intensity level) and structural capacity (for the desired performance level).
Regarding the seismic hazard, the parameters of the seismic hazard curve are estimated based on the regional seismicity. Seismic fragility functions are useful tools in order to quantify the seismic vulnerability of structures. These functions give a probability that a seismic demand on a structural component meets or exceeds its capacity and are generally derived by a variety of approaches. In this study, analytical fragility function will be performed using the well-known cloud method in order to evaluate the fragility curves of the components.
Finally, after the calculation of the seismic risk, the frequency of exceeding of each analysed equipment will be compared in order to recognise the most critical components and give a qualitative interpretation of the results.