A practical scheme of vibration monitoring and modal analysis for caisson breakwater

作者：Lee So Young; Thanh Canh Huynh; Kim Jeong Tae^*

来源：Coastal Engineering, 2018, 137: 103-119.

DOI：10.1016/j.coastaleng.2018.03.008

• Caisson breakwater
• Vibration monitoring
• Modal analysis
• Dynamic characteristics
• In-situ vibration record
• Stochastic subspace identification
• Frequency domain decomposition

In this study, a practical vibration analysis approach to obtain the dynamic characteristics of an in-situ caisson breakwater under the ambient wave load is presented. Firstly, a scheme of vibration monitoring and modal analysis is designed for the caisson breakwater. The limits of vibration monitoring on the caisson system is examined based on sensor placement and excitation source. An output-only modal analysis approach which combines the time-domain stochastic subspace identification method and the frequency domain decomposition method is designed to estimate modal parameters from wave-induced ambient vibration signals. Secondly, in-situ tests on a real caisson breakwater are described. Acceleration signals recorded under ambient wave-induced excitation are experimentally analyzed for a few caisson units under sea-level variation. Finally, experimental modal analyses are performed on the measured acceleration signals to evaluate the practicality of the proposed scheme. The numerical modal analysis of the caisson-foundation system was also conducted to support the experimental mode identification result. Relative modal responses of three adjacent caisson units are analyzed to estimate relative differences in dynamic characteristics due to their structural conditions. Also, the effect of water-level variation on modal parameters such as natural frequencies, modal damping and mode shapes is analyzed from the in-situ vibration records of a single caisson unit.

• 出版日期2018-7