Dynamic Response of Submerged Vertical Cylinder with Lumped Mass underSeismic Excitation

An analytical approach is presented to assess the response of offshore structures under seismicexcitation. This paper evaluates the impacts of different fluid field models and the mass of equipmentat the top of offshore structure which is simulated as lumped mass on the responses of offshorestructures. To do this, two and three dimensional fluid field models are developed. In threedimensional models different approximation regarding the free surface boundary condition associatedwith high and low frequency excitations are adopted. Then the alternation of response of structure withchanging in the value of lumped mass is calculated. Finally the impacts of different models on thevalue of maximum displacement for Kobe earthquake are evaluated. It is shown that differentapproximations regarding the fluid field could largely change the value of maximum displacementevaluated by the models.