Full-scale Testing Method And Prototype Monitoring Technology For Deep-water Floating Platforms

The floating platform is the key ocean engineering equipment in deep-water oil exploitation. Researches on structural analysis and design verification method of floating platform are the foundations for China to break through the technical bottleneck of deep-water development.Prototype measurement, as a modern experimental method, is the full-scale test carried out on in-service platform. Real time environmental loads and structural responses could be collected without simplification and hypothesis. The measurement results cannot only be used for design verification of the measured platform, but also can be used as reference for new design of similar structures.Due to the uncertainties of analysis condition, significant non-linear response of structure and limitation of laboratory equipment, traditional hydro-mechanical analysis and model test can't satisfy the design requirements of deep-water platform. Full-scale test has become an important method for structural analysis and design verification for deep-water floating platforms. However, due to complex structure and harsh environmental condition, large numbers of regular measurement methods are not applicable to the full-scale test of deep-water floating platforms. Especially, there is lack of measurement method and system for structure underwater. Therefore, it is difficult to obtain the complete measurement information in full-scale test. There are still many methods and technical difficulties to be solved for full-scale test at present.The thesis has carried out the research on the full-scale test method and monitoring technology for the design verification of the deep-water floating platform. The main content and results are obtained as follows:(1) Full-scale test methods for structure analysis and design evaluation of the deep-water floating platform.The reasonable measurement parameters, principles and methods are the premises to effectively application of full-scale test of the deepwater floating platform. According to the statistic results of the design flows of deepwater floating platform and failure incidents of North Sea floating platform in these years, the structural failure modes of the deepwater floating platform have been concluded. And the prototype measurement information is proposed based on fuailure modes. The measurement requirements of the measured information are discussed according to the design specifications of floating platforms. Taking considerations of the application conditions of floating platforms, the measurement method for recording multi-frequency response is designed based on INS/GPS and mclinometer/accelerometer measurement system. In addition, in order to realize the measurement for the deepwater mooring system, a kind of measurement strategy for mooring system based on inclination angle information is proposed based on lumped mass model. Finally, a full-scale test system for floating platforms is developed composed of environmental conditions, floater motions and mooring line dynamic response measurement systems.(2) Monitoring technology for the application of full-scale test.In order to realize the full-scale test on deep-water floating platforms, the monitoring technology is studied by using multi discipline cross technology of electronic, mechanical and computer. In order to solve the problem of the lack of mature measurement equipment at present, an underwater measurement system based on self-contained technology is designed and developed. At the same time, the research on underwater installation technology is carried out. The research results have broken through the bottleneck of underwater measurement for mooring system. Multilayer network integration technology of software and hardware is proposed to meet requirements of massive information acquisition and storage. An Independent Remote Monitoring System (IRMS) is designed and developed based on VPN and independent power supply technology. By using IRMS, collecting complete data during typhoon period is realized.(3) Full-scale test for NanHaiTiaoZhan FPSIn order to improve the feasibility and stability, a full-scale test system is designed and implemented on a semisubmersible platform, NanHaiTiaoZhan FPS, in South China Sea. The full-scale test has been carried out for more than 3 years. A large amount of prototype data is collected including the data during typhoon period.(4) Structure analysis and design verification based on prototype data.In the thesis, the data recorded during typhoon period is selected as the sampling data for time-domain and frequency-domain analysis. The analysis results are used to compare with numerical results analyzed by full-coupled analysis software. Comparison results can be used to investigate operation conditions of floating platfoms. RAO is the key design parameter for floating platform. We fit the RAO by using measured wave spectrum and response spectrum. The comparison results of measured and theoretical RAOs are used to evaluate design. The relationship between dynamic response of mooring line and wave frequency is discussed based on the data measured underwater by self-contained sensors. The contributions of different frequency components of mooring force are studied by using frequency-domain and wallet transform.