Effects of Foundation Models on Jack-up Site Assessment

Abstract

In order to investigate effects of different foundation models on jack-up site assessment, numerical simulation of a jack-up is presented based on fix joint, pin joint, linear springs and elastic-plastic model. The hull, leg, hull-leg connection is modelled using equivalent beam, beam element, spring element, respectively. Environmental loads, such as steady current, wind, wave, inertial load and buoyancy, are also included in the numerical model. Static and natural frequency extraction analysis of the jack-up is then performed in elevated condition. Finally, static and natural response rules are proposed for the four foundation models. The results show that, the horizontal hull displacement, maximum leg stress, loads on spudcan B and horizontal moment on spudcan A decrease as the rotational stiffness increases, while the natural frequency, vertical load and horizontal load on spudcan A increase with the increasing rotational stiffness. And the responses for elastic-plastic model are close to the pin joint. The proposed modelling and analyzing method is effective and reliable, which could provide guidance for jack-up development and assessment. Key words: Jack-up; Fix joint; Pin joint; Linear springs; Elastic-plastic model; Numerical simulation