Dynamic characteristics analysis of an in-service SYMS based on long-term field monitoring

The soft yoke mooring system (SYMS), which is widely used in China Bohai Bay and Gulf of Mexico, is the main mooring structure used by floating production storage and offloading (FPSO) in shallow water. Due to its multi -joint connection mode, the SYMS can realize the weathervane effect and ensure that FPSO vessel is at a position with the minimized ocean environmental loading. However, the complexity of ocean environmental loads and the non-linearity of SYMS structures make it difficult to predict the motion behaviors and force states that will be experienced by in-service SYMS, which can affect estimations of structural health status. Dynamic characteristics analysis of in-service SYMS is capable of addressing this complex problem and providing accurate estimations for improving mooring system design and safety. In this paper, a multi-body dynamic model for long-term service SYMS is established. Based on the data from a field monitoring system, the long-term motion characteristics of an in-service SYMS is analyzed. By combining the multi-body dynamic model with monitoring data, the long-term internal force statuses of each hinge joint is calculated. Then, the distribution of hinge joints load and horizontal restoring force are obtained, which provide effective numerical references for service life predictions of future SYMS and safety analysis of in-service SYMS.