Effect of Foundation Modeling on Extreme Response of Offshore Jack-up Unit
The demand for operation of mobile jack-up drilling rigs in offshore industry is increasing. Extreme response of jack-up platforms in sea environment requires improving the understanding of their nonlinear behavior. A sample jack-up platform located in Persian Gulf is modeled using three dimensional capabilities of USFOS considering both geometric and material nonlinearity. USFOS is a numerical tool for ultimate strength and progressive collapse analysis at frame structures such as jack-up platforms. Results of the analysis for the sample jack-up subjected to storm load pattern are compared for three different foundation modeling cases (pinned, fixed and spudcan modeling of foundation). Static pushover analysis is performed to determined jack-up behavior assuming different cases for fixity of foundation. It is observed that modeling of exact foundation by a simplified pinned model underestimates ultimate lateral strength of jack-up. A fixed based modeling overestimates lateral ultimate strength of the platform.