Seismic Vulnerability Assesment of Jacket Type Offshore Platforms

Most of oil and gas offshore platforms are located in the seismic regains. So, Seismic vulnerability evaluation of the offshore platforms is one of the most important and vital issues in the structural systems. In this study, jacket type offshore platforms are studied by incorporating the pushover analyses and nonlinear time history analyses, in such a way that, first some push over analyses are performed to detect the more critical members of the jacket platform according to the range of their plastic deformations. Then, nonlinear time history analyses are performed, concentrating on the critical members, to investigate the vulnerability of the jacket platform under intensive earthquake loads. Based on the numerical results, the combination of the push over analyses and nonlinear time history analyses presents a reliable and swift seismic assessment procedure to estimate the seismic vulnerability of the offshore platforms. Moreover, seismic vulnerability of the offshore structures is dependent on the critical member locations and their load bearing situations in the offshore structures.