Damage Monitoring Using Fiber Optic Sensors For The Joints Of Fiber Reinforced Polymer Structures

土建结构是人类活动最重要的设施，但它往往会对地球环境产生强烈的影响。解决这一问题的另一种方法是使用免维护、长寿命、纤维增强聚合物(FRP)复合材料，这种复合材料具有高耐腐蚀性、轻质和高强度的特点。事实上，许多FRP桥梁和FRP框架建筑结构最近都报告说，在使用一种创新的光纤传感器的情况下，长寿命FRP结构非常适合于在各种自然灾害后进行结构健康的定期检测和损伤识别。采用FRP材料对加拿大泰勒桥主梁进行加固，并安装光纤传感器，将光纤布拉格光栅(FBG)传感器埋入FRP结构构件中。首先，进行了玻璃钢拉挤带的纵向拉伸试验，结果表明，安装在构件内部的FBG传感器测得的应变响应与粘贴在构件表面的常规应变片的应变响应基本相同。其次，对螺栓搭接接头进行了纵向拉伸试验，采用无扭矩或扭矩为45N m的条件，讨论了摩擦阻力的影响。第三，利用螺栓对FRP结构构件与非结构构件之间的节点进行横向拉伸试验，将FBG传感器埋设在螺栓旁。结果表明，光功率随载荷的增加而减小，在达到临界载荷后，其形状出现两个峰值。当光纤功率谱有两个峰值时，由于连接螺栓附近局部大应力集中，FRP材料内部出现小的横向裂纹，FBG变成了两个不同的FBG。

Civil structures are the most important facilities for human activity, however, they usually have strong impacts to the environment of the earth. An alternative solution for this problem would be to use the maintenance-free long-lived, fiber reinforced polymer(FRP) composites which have high corrosion resistant, light weight and high strength characteristics. Actually, many FRP bridges and FRP framed architectural structures have recently reported The long-lived FRP structure is very attractive to do the periodical inspection of structural health and the damage identification after various natural disasters under the use of an innovative optical fiber sensors. The girders of Taylor Bridge in Canada have been reinforced with FRP material and installed fiber optic sensors.In this study, fiber Bragg grating(FBG) sensors were embedded in FRP structural members. First, the longitudinal tensile test of pultruded FRP strips have been performed and shown that the strain response measured with FBG sensors installed into the members is approximately the same as that with conventional strain gauges pasted on the surface of the members. Second, the longitudinal tensile tests of the bolted lap joints have been carried out ; the no-torque condition or a 45 N m torque has been adopted and the effects of frictional resistance have been discussed. Third, the FBG sensors were embedded beside the bolt on the transverse direction tension tests of the joints between a FRP structural member and a non-structural member using bolts. It is shown that the optical power decreases as the load increases, and its shape has two peaks after reaching at a critical load. When optical power spectrum has two peaks, the FBG becomes two different FBGs due to the occurrences of small transverse cracks inside the FRP material under locally large stress concentration beside the joint bolt.