Seismic fragility assessment of equipment and support structure in a unit of a petrochemical plant

Petrochemical plants and industrial facilities have shown high vulnerability during the past earthquakes like Kobe (Japan, 1995), Izmit (Turkey, 1999), Gujarat (India, 2001), Tokachi-Oki (Japan, 2003) and other earthquakes. As more than 50% of the petrochemical and refineries in Iran are located on hazardous areas, it is absolutely essential to allocate a great deal of attention to such places. Apart from economic impacts, damage to such facilities may have considerable effects on peoples’ lives. Therefore, it is extremely vital to try to prevent natural disasters from damaging these highly regarded sites. For this reason, this research aims to investigate the seismic fragility of equipment and support structure in a unit that is located in Shiraz-Iran. In so doing, their impact on the overall vulnerability of petrochemical plant will be evaluated. As one of the common methods for this aim seismic risk assessment should be done, and IDA (incremental dynamic analysis) method_a probability method_is utilized. Seismic risk assessment in petrochemical plants plays a key role in making decisions for risk management strategies such as retrofit, etc. For this purpose, seismic risk assessment of equipment and support structure as a section of a petrochemical plant are evaluated. To fulfil the main goal of the research, in this project fragility curves are used to explain the seismic vulnerability of structure. In this method, failure modes are selected based on damages caused by past earthquakes. Shear failure of bolts have been considered as a failure mode of equipment and inter story drift ratio have been considered as failure mode of support structure. Peak ground acceleration is chosen as an earthquake intensity measure. In order to develop seismic fragility curves, created models are subjected to 40 ground motion records, each scaled to multiple levels of intensity to perform incremental dynamic analysis using Seismostruct software. Numerical results represent the significant influence of essential and hazardous equipment on the seismic fragility of the under-study unit of petrochemical plant. Final results show that the equipment that is located on fifth story is the most vulnerable component of the unit.