| For numerous large-scale bridges in modern construction, cording structure is used extensively, for instance the oblique cable of cable-stay bridge, main cable and sling of the suspension bridge, and the bowstring and steeve in the bowstring arch bridge, etc.. As pivotal bearing strength component in these bridge system, its strain size, variation and disruption reflects the security and health status of large-scale bridges most directly, so it have great meanings to monitor tension statues of these components as well as assess security and health statues based on the monitoring results.Using the strain sensors is the directly main method of measuring the tension of cording component, the three structure forms of the strain sensor are spoke type, ring type and hydraulic pressure type, the ring type strain sensor among them is being called the load cell too. The strain sensor on the basis of traditional measure technology, has different sensing principles, such as differential resistance type, shakes string type, or resistance to meet an emergency mainly one scene of types, etc.. For a short time strain testing, traditional load cell can satisfy the project application basically, but tradition test technological limitation of itself cause long-term strain monitoring unable to realize. So, the new-type load cell that can monitor the strain reliably for a long time becomes the pursuing goal in the field of bridge building.Based on Fiber Bragg Grating sensing technology that has come into being recently, this paper has strived to develop a novel FBG load cell that adapts to civil engineering. Applications show that the FBG sensor has some special characteristics such as high precision, distributed sensing, absolute data testing, good long-term stability and immune to electromagnetic interference, and it can realize real-time and on-line monitoring, in addition to having the same functions as the traditional electric sensors. But FBG has a low sensitivity to pressure, it's necessary to enhance pressure sensitivity and encapsulate FBG availably so that it can satisfy the requirements of practical engineering. The methods of enhancing pressure sensitivity and theencapsulation to FBG load cell have been emphasized in this thesis. The main tasks are as follow:1. Based on the theory of fiber optical Bragg and the structure of bridge, a new design way of the sensor has been put forward. This paper study the principium of FBG load cell. The paper has also analyzed material, structure and error of elastomer, and has confirmed the load cell material and structure, and has deeply probed into the effect of encapsulation structural dimension and encapsulation method of FBG on the performances of the sensor.2. The key technology of the sensor has been effectively solved. Succeeding to jointing FBG sensor on elastomer, which realizes available encapsulation and enhanced pressure sensitivity of FBG, this provides a new scheme for solving the most difficult problem in FBG sensor development. The methods of encapsulation and manufacture technology have been studied to adapt to industrial application.3. Experimental studies to the novel sensor have been developed and the performances of the sensor have been analyzed. Experimental studies to temperature compensation of FBG load cell, this provides a new scheme for solving the temperature compensation problem in FBG load cell.4. Good application effect has been obtained in engineering. New sensor has successfully been applied to civil engineering, the compared tests were made between the new sensor and the common electricity-detecting instrument, and it has obtained good monitoring effect.Studies show that the FBG load cell has good repeatability ^ linearity and sensitivity, it can meet the requirements of practical engineering, and it has an extensive application prospect in the civil engineering.
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