Integrated Fiber Optic Sensor for Condition Monitoring of Concrete and FRP Tendons

混凝土和玻璃钢筋的集成光纤传感器状态监测摘要9900338纤维增强塑料(FRP)已被用作混凝土结构中传统钢筋的替代品。玻璃钢筋的主要特性是耐腐蚀、质量轻、抗拉强度高。尽管FRP筋的强度与重量比要高得多，但仍有许多缺点阻碍了它们的广泛使用。与普通钢筋的延性弹塑性行为相比，FRP复合材料的应力-应变响应表现为脆性行为，并且一直是线弹性的直至破坏。这个问题影响到混凝土构件中FRP筋的适用性、设计和安全性。这项研究计划将重点关注用于FRP筋状态监测的集成光纤传感器系统的开发。传感器将由一根光纤组成，光纤沿其长度方向嵌入部分反射器。将使用光时域反射计来询问来自结构不同区域的反射光信号。光纤传感器系统将通过一项全面的研究计划来开发，在此期间将解决以下问题：(1)埋入混凝土结构的传感器配置的实用性和状态监测阶段仪器的简单性。(2)模拟检测纤维断裂的能力、其位置以及沿构件长度以分布方式测量应变梯度的能力。(3)用应变幅值和空间分辨率来描述沿FRP筋长度的损伤区域位置的敏感性。(4)结构在生命周期内长期使用的坚固性。建议的光纤系统的性能将通过一个广泛的实验计划进行评估，该计划涉及后张法FRP梁的准静态和疲劳加载。将研究光纤在检测、定位和评估渐进性损伤方面的有效性。该项目的主要部分将涉及在同时检测梁中不同位置发出的裂缝方面对系统性能的评估。将进行测试，以确定在关联光纤数据以及早检测FRP筋和周围混凝土裂缝方面所能达到的置信度水平。嵌入式光纤传感器将起到双重作用。它将被用于结构的实时状态监测和即将到来的故障警告，并用于建立与材料和结构行为有关的全面数据库，从而促进FRP结构更现实的设计。

INTEGRATED FIBER OPTIC SENSOR CONDITION MONITORING OF CONCRETE AND FRP TENDONS ABSTRACT 9900338 Fiber reinforced plastics (FRP) have been employed as an alternative to conventional steel reinforcement in concrete structures. The primary attributes of FRP tendons are that of corrosion resistance reduced mass, and high tensile strength. Despite the much higher strength to weight ratios exhibited by FRP tendons, there are a number of drawbacks that hinders their widespread usage. In compare to the ductile elasto-plastic behavior of conventional steel reinforcement, the stress-strain response of FRP composites exhibit brittle behavior and are linear-elastic all the way to failure. This issue effects serviceability, design and safety of FRP tendons in concrete elements. This research program will focus attention into the development of an integrated fiber optic sensor system for condition monitoring of FRP bars. The sensor will comprise of an optical fiber with embedded partial reflectors along its length. An Optical Time Domain Reflectometer will be employed for interrogation of reflected optical signal from various regions of the structure. The fiber optic sensor system will be developed through a comprehensive research program during which the following issues will be addressed: (1) Practicality in terms of sensor confriguration for embeddment in concrete structures and simplicity of instrumentation during the condition monitoring stage. (2) Capability for seimulations detection of fiber breakage, its location, and measurement of strain gradients along the length of the member in a distributed manner. (3) Sensitivity in terms of strain amplitude and spatial resolution for characterization of damaged zone locations along the length of the FRP tendon. (4) Ruggedness for long term use during the life cycle of the structure. Performance of the proposed fiber optic system will be evaluated through an extensive experimental program involving quasi-static as well as fatigue loading of post-tensioned FRP beams. The efficacy of optical fibers in detecting, locating and evaluation of progressive damage will be investigated. A major portion of the project will involve evaluation of the system performance in terms of simultaneous detection of cracks emanating from different locations in beams. Tests will be performed to determine the level of confidence that can be achieved in correlating the fiber optic data for early detection of cracks in the FRP tendons as well as the surrounding concrete. The embedded optical fiber sensor will play a dual role. It will be employed for condition monitoring of the structure in real-time and to warn of impending failures, and for establishment of a comprehensive database pertaining to the material and structural behavior and therefore facilitate development of more realistic designs of FRP structures.