Fiber Bragg Grating In The Measurement Of Cable Structures

A cable and the anchor cable which are with cable-structure are mainly used for civil protection works. The cable, which is a part of cable barrier, is set up at the side of highway to prevent vehicles from crossing the way causing a secondary accident. And the anchor cable, which is for rock and concrete anchoring, makes those constructions in a compressed state to prevent them from landslide or displacement. Those cable-structure devices are in high stress state and are affected by natural factors, human factors and the creep material itself after be set up. In this situation, the anchor head may be loose, disengage under great force (such as impacted by a high-speed vehicle, strong wing, earthquakes, etc.), and its original protection fails, even lead the secondary accidents happen. The monitoring on cable-structure devices not only can provide a evaluation on the construction, but also can track the health status.In this paper, fiber Bragg grating is used as the sensing element, theoretical analysis and experimental research of t he cable and the anchor cable were carried out. Hydraulic jack and pressure testing machine are used to simulate the stress in those servicing state cable-structure devices. The main completed work as follows:1. Under the action of the load, the anchor head, cable and anchor cable will deform to cause the wavelength of Fiber Bragg Gratings shift.Through this theory, a mathematical model of sensor was established.2. The Measuring points are in the in the slot of the anchor, on the surface of a single wire of the cable and on the surface of a single wire of the cable anchor separately, the theoretical response sensitivity, respectively:3.6 pm/KN,5.9 pm/KN,26.6 pm/KN; theory of resolution, respectively:0.278 KN/pm,0.169 KN/pm,0.376 KN/pm.3. Tensile experimental shows that the response sensitivity of Fiber Bragg Grating in the anchor head is 2 pm/KN, and on the cable is 6 pm/KN, on the anchor cable is 26.6 pm/KN; Compression experiment indicates that the sensitivity of Fiber Bragg Grating in the terminal anchor is 4 pm/KN.