Comparing of System Identification and Spectral Analysis Capability in Modeling and Predicting of the Sea Wave Hydrodynamic Forces on Cylindrical Pile

Evaluating criteria of nature of forces on structures is an important step in design, construction and utility. In a stochastic phenomenon, the process of the force exerting, are more complicated. Sea waves have such characteristics, where hydrodynamic forces act on hydraulic, offshore and coastal structures. In this paper, the cylinder structure is considered as a system with incoming water wave inputs and the time series of the resultant forces are system’s responses. The experimental data used in this study were collected at a hydraulics laboratory on a full-scale rough vertical cylinders and the capability of system identification and spectral analysis to modeling and prediction of these forces were evaluated and compared. For this purpose, first, a transfer function has been estimated, and then an ARMAX model has been used to capture the dynamics of the process relating in-line forces provided by water waves. Finally, the comparisons between two methods and conclusion have been made.