A wireless sensing system for structural health monitoring (SHM) of harbor caisson structures is presented. To achieve the objective, the following approaches were implemented. First, a wave-induced vibration sensing system was designed for global structural health monitoring. Second, global SHM methods which are suitable for damage monitoring of caisson structures were selected to alarm the occurrence of unwanted behaviors. Third, an SHM scheme was designed for the target structure by implementing the selected SHM methods. Operation logics of the SHM methods were programmed based on the concept of the wireless sensor network. Finally, the performance of the proposed system was globally evaluated for a field harbor caisson structure for which a series of tasks were experimentally performed by the wireless sensing system. 1. Introduction According to a report of the Intergovernmental Panel on Climate Change [1], global warming is unambiguous. As sea surface temperature increases, water vapor in the lower troposphere also increases, and so does the energy of typhoons. The relationship between global warming and increased typhoon activity and intensity has been verified, reported by studies based on analyses of historical records and simulation results [2–4]. It was also reported that typhoons in the western North Pacific (WNP), including Korea, have become more intense as measured by their frequency in hurricane categories 4 and 5 [5] or the power dissipation index [3]. A strong typhoon usually brings strong winds and heavy rains, causes severe surge and floods, and then results in significant loss of life and property. Accordingly, the increase of typhoon intensity and frequency makes severer damages over the Pacific Ocean from the Philippine Islands to Taiwan, Japan, Korea, and the southwestern coast of China. In general, coastlines, interfaces between ocean and land, are facing a severe state of typhoon than inland; thus, the safety of coastal structures becomes more significant under storm waves. The safety can be checked in a regular or irregular time scale, depending on the state of the target coastal structures and occurrence of extreme loading conditions such as typhoons. The safety is usually done by structural health monitoring (SHM) to identify existing damages in the target structures, gravity type or pile type, and finally to make an assessment of their healthy status. In the gravity-type coastal structures, the damages can be classified into settlement, overturning, or sliding. Local defects such as scouring and disturbance in foundation can
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