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

土木建筑是人类活动最重要的设施，但对地球环境的影响往往很大。解决这个问题的另一种方法是使用免维护的长寿命纤维增强聚合物（FRP）复合材料，它具有高耐腐蚀性、重量轻和高强度的特点。事实上，近年来已有许多玻璃钢桥梁和玻璃钢框架建筑结构的报道，在新型光纤传感器的应用下，长寿命玻璃钢结构在进行结构健康定期检测和各种自然灾害后的损伤识别方面具有很大的吸引力。加拿大泰勒大桥的主梁采用FRP材料加固，并安装了光纤传感器。在本研究中，光纤布拉格光栅（FBG）传感器嵌入玻璃钢结构构件。首先，对拉伸FRP条进行了纵向拉伸试验，结果表明，安装在构件中的FBG传感器测量的应变响应与粘贴在构件表面的传统应变片测量的应变响应大致相同。其次，对螺栓搭接节点进行了纵向拉伸试验；采用无转矩条件和45 N m转矩，讨论了摩擦阻力的影响。第三，将光纤光栅传感器埋设在螺栓旁，利用螺栓对玻璃钢构件与非构件连接进行横向拉伸试验。结果表明，光功率随负载的增加而减小，且在达到临界负载后，其形状出现两个峰值。当光功率谱出现两个峰值时，由于FRP材料在连接螺栓附近局部较大应力集中的情况下，内部出现小的横向裂纹，导致光纤光栅变成两个不同的光纤光栅。

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.