Comparison of seismic responses of a fixed offshore structure for ground motion records considered near fault effect and fling effect generated using three methods

Offshore platforms, fixed or floaters, are a well-established design concept for oil explorations. It is fundamental to design these structures such that they can resist moderate to severe earthquakes without causing any severe damage to the occupants and to maintain the integrity of the structure. Hence, it is important to examine the behavior of these offshore structures for all kinds of earthquake scenarios to determine the risk levels that may occur in the structure. This paper intents to compare the seismic responses for a fixed offshore structure by employing ground motion records generated using three different methods. The design spectrum determines the seismic hazard of a region. Therefore, it is necessary to use acceleration records compatible with the design spectrum in seismic analyses. In this paper, Scaling, Spectral matching and Stochastic methods were used for comparison. Peerscaled tool was used for scaling in the time domain. RspMatch was used for the Spectral Matching. New acceleration records were generated by QuakeSim. A series of non-linear time histories using acceleration records of scaled ground motions were carried out to compare the damage levels and responses of a fixed offshore structure. Spectral matching method was observed to cause higher displacements than scaling method. The occurrence of inelastic events, such as buckling was observed to be high when the acceleration records considered the near-fault effect. And, permanent deformation was observed when acceleration records considered the fling effect. Ground motion records generated by different methods if adopted while performing seismic assessments of offshore structures will reduce the risk level for the structure.