RELIABILITY OF AN ENGINEERING SYSTEM UNDER A STRONG EARTHQUAKE WITH APPLICATION TO OFFSHORE PLATFORMS

This paper presents a method developed for the performance evaluation of an engineering system during a strong earthquake. The seismic relia bility of the system is evaluated by considering the different possibl e failure modes, and seismic reliability of the components of the syst em. The method is applied to the oil production system at the Statfjor d Field in the North Sea. The objective of the analysis is to document the reliability of oil production from the field in the event of an e xceptionally large earthquake, and to investigate the effect of spatia l variation of earthquake loading parameters on the computed system re liability. It is shown that, with a realistic model of the spatial var iation of earthquake motion, there is very little correlation between the earthquake loading parameters at different platform locations. The main consequence of this lack of correlation is that the computed fai lure probability of the oil production system under the design earthqu ake is about one order of magnitude smaller than the probability of fa ilure of individual platforms at the Statfjord Field.