Vibration-based structural identification of caisson-foundation system via in situ measurement and simplified model

In this study, a structural identification is performed for a real caisson breakwater by using in situ vibration measurement and a simplified analytical model allowing a few degrees of freedom. First, a vibration-based method is designed to identify the dynamic characteristics of the caisson-foundation system that has the limited in situ measurement condition. Second, a few in situ vibration measurements performed on a real caisson breakwater are described. Wave-induced acceleration responses recorded from a single caisson are experimentally analyzed to acquire dynamic modal parameters under water-level variation. Third, the structural identification is performed to obtain the simplified mass–spring–dashpot model that represents the measured dynamic characteristics. The structural parameters of the caisson-foundation system are estimated from the model fine-tuning process based on the theory of modal sensitivity. Finally, the simplified model is utilized to predict the vibration responses of the target caisson system under several events such as foundation damage, interlocking damage, and water-level variation. The feasibility of the wave force inference from vibration measurements by using the simplified is also investigated for a finite element model of caisson breakwater.