Missing Factors in Seismic Safety Evaluation of Petrochemical Facilities by Practicing Engineers

Practicing engineers usually use the design codes or standards, such as ASME 08, for seismic evaluation purposes as well. Therefore, there are some common missing factors in such evaluation processes which may lead to inadequate estimation of seismic vulnerability of equipments, and this in turn results in either unsafe or uneconomical retrofit design of the facilities. This paper discusses that some of these shortcomings may cause serious mistakes in dynamic response values of the equipment, which is a key factor in vulnerability evaluation. For this purpose at first, various major equipments of petrochemical plants have been considered and their seismic vulnerability has been evaluated by using the common practice in engineering offices, which is based on seismic design codes or standards. Then, the seismic vulnerability of the same equipments has been evaluated once more by considering their detailed dynamic models and using linear and nonlinear Pseudo Dynamic or spectral as well as Time History Analyses methods. The obtained numerical results have been compared to show the effects of missing factors in engineering practice. Results show that neglecting some details can lead to significant differences in the dynamic response of many types of equipments.