Effect of Type of Support on The Responce of Offshore Sructure Under Seismic Load

The seismic force has very important effects in the response of offshore structures and it is considered as applied dynamic forces. The seismic must be taken in consideration in designing stage due to their high effects on the safety of platform under earthquake. In this paper a comparison in response between offshore structures with fixed support at sea bed and with embedded piling support. AL-Basrah oil port (ABOP) is taken in consideration as a case study where   two models are used, in the first model the pile –soil interaction (PSI) is neglected and the fixed support is used in the level of sea bed however in the second model, the effect of pile –soil interaction is considered. For two models the finite element analysis was performed in linear behavior for piles and deck while the soil is treated as nonlinear. The results are shown that the natural frequency for fixed support is more than for structure with piling support and the responses are more influenced by the near in frequency between structure and seismic action