Risk assessment of a typical petrochemical plant with ageing effects subjected to seismic sequences

Ensuring the safety and functionality of petrochemical plants after a strong earthquake is critical, particularly due to the presence of hazardous chemical materials stored in pressurized vessels and reaction tanks that can be flammable or toxic. Strong earthquakes in chemical units can cause severe structural damage, leading to adverse consequences like human injuries and economic losses. In harsh atmospheric environments, existing steel structures that have not been maintained adequately throughout their lifetime become even more vulnerable to ground motions due to corrosion-induced capacity loss. This study focuses on the vulnerability assessment of an existing aging petrochemical plant located in a high-corrosive atmospheric condition, used as a case study. The risk assessment employs probabilistic approaches to estimate the damage level and associated repair costs at different intensities of ground motion, corresponding to each state of damage (loss). Moreover, the study investigates the effect of non-structural components and their interaction with the primary structure by employing advanced finite element modelling of reaction tanks. The results indicate that aftershock motions can slightly alter the performance of the structure, whereas the effect of corrosion is more significant. Particularly, for the corroded structure, the seismic risk is significantly affected by the demand imposed by aftershocks. These results underscore the importance of comprehensive risk assessments to ensure the safety and integrity of existing petrochemical plants with aging effects and located in seismic zones.