Study On Intrinsic Fbg-based Smart Structures

At present, "structural health monitoring" has become one of the world's research focus, in particular, the field of fiber-optic smart structures monitoring,which is based on the technology of optical fiber sensing, is becoming concerned object of the large number of experts and scholars, not only it is a concentrated expression of modern structural testing technology, but also verifies the structural design of major engineering, construction control, safe operation and damage assessment as an important technology. Fiber-optic smart structures ,which can effectively solve the issues of health monitoring and safety assessment of major engineering structures during in-service by giving the structural characteristics of specific intelligence and life, have a lot of advantages such as anti-electromagnetic interference, durability, absolute distributed measurement, etc.The cable in cable-stayed bridges&arch boom as the force components of the structure during in-service works in the harsh environment in general, the stress state is directly related to the structure of the service functions (such as the deflection is too large) and security (such as cracks , fracture, etc.). Therefore, how to effectively online real-time monitor stress state of the cable, diagnosis injury and estimate life expectancy is a very important work and has broad application prospects.The traditional electric sounding (pull pressure sensors, vibrating wire sensors, etc.) or the magnetic flux sensor for the cable or boom (steel bar) has the difficulty of layout and long-term monitoring,contrary to this problem based on our group's research achievements , a high durability, high stability fiber Bragg grating smart structure:FBG smart cable and FBG smart steel rod , the stress relaxation properties of FRP-OFBG are studied. The main research content of this article as follows:First of all, according to the need of long-term effective means of monitoring internal force of cable or boom for cable-stayed bridge in harsh environments, a intelligent parallel cables was developed by compositing high durability, high tensile strength FRP-OFBG and cable, its sensor characteristics are studied by calibration experiment and expstatistical methods.Secondly, FRP-OFBG are used for long-term SHM testing in civil engineering, some factors such as stress relaxation may cause adverse influence. So FRP-OFBG's long term stress relaxation performance are studied by experiment ,what is more a mathematical model is derived to describe stress relaxation. Based on the experiment results and mathematical model, a quantitative analysis for of the impact of stress relaxation is carried out. All of work above is to provide the basis for amenting the effects of stress relaxation for civil structure health monitoring. Finally, accorded to the constructure condition that current monitoring tools can't meet the needs of long-term internal force load testing of high intensity steel, a high-durability smart steel rod based on the FBG sensor and reinforced plastic packaging tenology is developed, and its sensing properties studied. Smart steel rod, which has the advantages such as anti-electromagnetic interference, long sensing distance, low cost, corrosion resistance, absolute measurement, etc., not only can be given its stress information at any stage, but also can be used as a sensor to monitor adjacent structure, so it is suitable to monitor steel structures in harsh environment.