在就位过程中，桁架桩腿自升式平台会产生齿条相位差，在桩腿与平台主船体接触位置产生极大的附加弯矩，导致平台主体下导向位置的桩腿撑管发生屈曲失效。本文以某平台为研究对象，采用ANSYS软件建立平台三维时域有限元模型，并通过生死单元技术实现自升式平台升船过程实时模拟与RPD值预测；根据RPD值的变化情况将升船过程划分为4个主要阶段。在此基础上，对3种风速工况下平台RPD变化特性进行分析，从而判断升船阶段风速对RPD的影响。依据掌握的RPD与桩腿应力的变化规律及许用RPD值，提出一套RPD控制方法，为确保平台就位升船作业安全提供依据。

Rack phase difference may be produced in the process of positioning of truss-type Jack-up unit， which will cause a significant additional bending moment at the contact position between the legs and the main hull of the unit， resulting in buckling failure of the leg support pipe at the low guiding position of the hull. In the paper, a jack-up unit is taken as the research object， ANSYS software and birth-death element technology is used to forecast RPD value of jack-up unit in the process of lifting hull by 3-D time-domain numerical simulation analysis， which is divided into four main stages according to changes of RPD value. On this basis， the RPD variation characteristics under three wind speed conditions are analyzed， which is helpful to determine the impact of wind speed on RPD in the process of lifting hull. Finally， a set of RPD control method is proposed based on the law of the change of RPD and the stress of the leg in order to monitor RPD of platform leg.