The lifetime of an offshore platform is typically governed by accumulated fatigue damage. Thus, the load time history is an essential parameter for prediction of the lifetime of the structure and its components. Consequently, monitoring of structural loads is of special importance in relation to re-assessment of offshore platforms. Structural monitoring systems (SMSs) on offshore structures typically consist of a set of sensors such as strain gauges, accelerometers, wave radars and GPSs, however direct measuring of the actual loading is usually not feasible. One approach is to measure the loads indirectly by monitoring of the available dynamic responses of the structure. This work investigates the possibility for using an economically beneficial, model-based load estimation algorithm for indirect measuring of the loading forces acting on the offshore structure. The algorithm is based on the reduced order model of the structure and the discrete Kalman filter which recursively estimates unknown states of the system in real time. As a test-case, the algorithm is designed to estimate the equivalent total loading forces of the structure. The loads are estimated from noised displacement measurements of a single location on the topside of the offshore structure. The method is validated using simulated data for two wave loading cases: regular and irregular wave loadings.
Conference Proceedings of the Society for Experimental Mechanics Series: Proceedings of the 32nd Imac, a Conference and Expos Ition on Structura L Dynamics, 2014, 2014, p. 99-109