Prototype Measurements And Analysis Of Deepwater Floating Structures

Floating offshore structures have been used since the1950s for drilling, and they have become increasingly popular for production, particularly in deep water. Design of floating offshore structures is often based on published industry standards and classification rules. As the industry moves into ever deeper water and newer environment, it becomes even more important to question the standards developed for shallow water or mobile facilities. The other important point to make here is that as the industry moves to deeper water, the tools available for global response analysis including numerical simulation and model testing couldn’t meet the design requirements of reliability and economy. The prototype measurement can reflect the real loads and response of the structures, which could be used to verify the previously predicted response by physical model testing and analytical tools and also provide early warning information on the structural risk. Therefore the prototype measurements of floating offshore structures have attracted more attention especially when a new concept was designed and installed.This dissertation conducts research on prototype measurements of floating offshore structures to solve the problems in the design and operation process of the floating structures. By collecting and analyzing the floating structures accidents, it is summarized that the main failure models of these structures are stability failure, strength failure and positioning failure. From the point of failure analysis, a prototype measurement system in filed was presented and installed on a floating production system in South China Sea. Besides a mooring line posture measurement method is put forward according to the multi-component catenary equation and boundary conditions, in order to make up for the deficiencies of mooring system in-site measurement. Through the field measurement data statistics and analysis, the applicability of JONSWAP spectrum in the South China Sea is discussed that the structures would be designed conservatively by use of the JONSWAP average spectrum. Also a coupled numerical model of the floating structure and the mooring system is established to predict the platform motion response under the measured environmental loads.