Research On Structure Optimization Design For Cantilever Beam Of Jack-up Drilling Platform

With the continuous exploitation of hydrocarbon resources, the amount of them are reducing gradually. At the same time, human are paying more and more attention to the exploitation of offshore oil and gas resources. However, the exploitation of sea resources is limited by the offshore operation environment, as a result, it is essential to set up dedicated offshore platforms. Jack-up drilling platform has been widely used in the exploitation of marine resources of oil and gas drilling for the advantages of its flexible operation,positioning ability, wide adaption to water and re-usability. Cantilever jack-up platform is the main type of jack-up drilling platform. Cantilever beam, as the main bearing platform of drilling process, can enhance the capacity and range of platform operation effectively,greatly improving the work efficiency. Therefore, making a numerical analysis of cantilever beam structure of jack-upplatform, provides technical advice and engineering reference for the design of offshore oil equipment as well as the construction for our country.Based on the research object about the structure of a 350 ft jack-up drilling platform in a domestic shipyard, this thesis establishes a model about cantilever beams. At the same time, this thesis makes an analysis of the intensity and dynamic response. In the end, this thesis makes a research on the structure optimization on the basis of the structural analysis and analyzes the optimized structure. Concrete researches of this thesis are summarized as follows:(1) According to the structural characteristics of cantilever beam, operation environment and the research goals of this thesis about the jack-up drilling platform, this thesis makes an in-depth discussion about the Finite Element Theory and the Theory of Structure Optimization design used during the research process, which provides the necessary theoretical basis for the analysis of the cantilever structure and optimization research.(2) According to the operation environment of the jack-up drilling platform and the structural characteristics of the cantilever beam, the test on the load on the cantilever was conducted, and the data analysis was conducted in accordance with the loading scheme of the test to provide basis for the following study on the strength of the structures; Then on the basis of cantilever condition and the analysis of cantilever beam load, this thesis establishes a finite element model about the cantilever beam, making an analysis and acheck for the intensity and stiffness characteristics of cantilever beam in different location and different operation conditions. At the same time, this thesis analyzes the influence of wind on the structural intensity of cantilever beam in different working operation, laying the foundation for subsequent structural optimization design of cantilever beam.(3) Cantilever Beam suffers the large amount of complicate load during the production process. In order to study the dynamic response, this thesis makes modal analysis of a cantilever beam with Lanczos method, getting a few bands before structure of natural frequency and mode shape. Based on the modal analysis, this thesis makes an analysis of frequency response and transient dynamics response, reaching some relevant results and conclusion.(4) According to the results of finite element analysis of a cantilever beam and some relevant verification standard, this thesis selects the appropriate design variables, state variables and objective function through some analysis. Through setting some related parameters and relying on the nastran optimization function, this thesis makes a designation of structure dimension in about the both sides of the cantilever girder, pipe rack deck and cellar deck. By comparing the different structural forms, this thesis results in the best structural form of a cantilever beam, in order to achieve the goal of reducing the weight of a cantilever beam structure. Moreover, this thesis verifies the feasibility of the optimized structure, analyzing the dynamic performances before and after optimized structure comparatively.(5) Based on traditional cantilever beam, double web plate cantilever beam was proposal, and then compare of Structure performance with new and traditional cantilever beam were undertaken.