FUNDAMENTAL STUDY ON REMOTE MONITORING OF SHIP STRUCTURES BY USING FIBER-OPTIC SENSORS

船只和近海建筑偶尔会被巨浪和强风损坏。由于海洋现象的统计特性，海浪和风对海洋结构的荷载不容易估计。船舶的着陆和碰撞可能造成严重的海洋污染。通过对海洋结构的受力状态进行监测和结构完整性检测，可以预防海洋结构的严重破坏。基于光纤传感器网络的智能结构概念可以应用于海洋结构。大型海上构造物大量存在，如超大型原油运输船（VLCC）总长度超过200米。长量规长度的位移传感器适用于对船舶结构性能的全局了解。针对智能船舶结构，应开发传感器头简单、灵敏度高的新型长规长度传感器。本研究提出了一种光纤激光多普勒测振仪（FLDV）传感器作为备选传感器。本文讨论了光纤激光多普勒传感器在舰船结构中的适用性。采用光纤布拉格光栅（FBG）作为准分布式应变传感器，研究了传感功能的精度和稳定性，并将其应用于受弯曲载荷作用的模型试样。国际美洲杯级（IACC）游艇是一种特殊的船只，其大部分部件由碳纤维增强塑料（CFRP）制成，并受IACC规则监管。布里渊光时域反射计（BOTDR）是一种能够沿光纤测量应变和温度的光纤分布式传感器。我们为日本参加2000年美洲杯的IACC游艇配备了这些传感器。使用BOTDR测量的游艇应变分布用于结构健康监测，并在比赛期间继续评估结构完整性。

Ships and offshore structures are occasionally damaged by rough waves and strong winds. It is not easy to estimate loads of waves and winds to the marine structure because of the statistical feature of oceanographic phenomena. Landing and collision of ships might result in severe marine pollution. Prevention of serious damage of the marine structures might be achieved by monitoring the loading condition and by inspecting the structural integrity. The concept of smart structures with fiber-optic sensor network can be applied to the marine structures.There are plenty of marine structures in huge dimensions, for example, overall length of very large crude carrier (VLCC) exceeds 200 m. Displacement sensor with long gauge length is suitable for global uderstanding of structural ship behavior. New long gauge length sensor, which has simple sensor head and achieves high sensitivity, should be developed for smart marine structure. A fiber-optic Laser-Doppler vibrometer (FLDV) sensor has been proposed as the alternative sensor in the present study. In the present study, applicability of the fiber-optic Laser-Doppler sensor to ship structures is discussed.Fiber Bragg Grating (FBG) was applied as quasi-distributed strain sensor and accuracy and stability of sensing function was investigated and applied to model specimen subjected to flexural load. International America's Cup Class (IACC) yachts are specific boats whose most components made of carbon fiber reinforced plastic (CFRP) and that are regulated by the IACC rule. A Brillouin optical time domain reflectometer (BOTDR) is a fiber optic distributed sensor that can measure strain and temperature along an optical fiber. We equipped IACC yachts that were the Japanese entry in America's Cup 2000 with these sensors. Strain distributions of the yachts measured with BOTDR were used for structural health monitoring and assessments of the structural integrity were continued during races.