Evaluation of Vibration Characteristics of Caisson-Type Breakwater Using Impact Vibration Tests and Validation of Numerical Analysis Model

摘要

In this study, ambient and forced vibration tests are proposed toevaluate dynamic characteristics of a caisson-type breakwater includingnatural frequencies and modal damping ratios, and the feasibility ofnumerical analysis model with fluid-structure-soil interaction effects,which plays an important role to evaluate structural performance andsafety, is investigated by comparing the numerical results withexperimental results. Oryukdo breakwater in Busan, Korea is utilized asa target structure, and this breakwater was once heightened byinstalling additional parapet structures as amount of about 4 m toimprove the harbor tranquility in 2005. Two times of vibration testswere carried out in 2000 (before heightening) and in 2011 (afterheightening). In the first test, most caissons were tested while onecaisson was tested in 2011. It is found that natural frequencies arereduced as amount of 1.7 – 4.3 % after heightening, and similar resultsare observed from the numerical analysis. It is also found that forcedvibration tests can make more reasonable results than ambient vibrationtests. Even though there is some degree of discrepancy betweenexperimental and numerical results, numerical analysis can be carriedout to analyze dynamic characteristics and evaluate the structuralperformance and safety.