Distributed strain measurement method of bridge based on weak FBG sensing array

Abstract

Strain is an important parameter that reflects the safety state of bridge structure, at present, distributed strain measurement is one of the research hotspots in the field of structural health monitoring (SHM). The sensors such as strain gauge, vibrational chord strain gauge and fiber Bragg grating (FBG) strain gauge is difficult to network and realize distributed measurement. The optical fiber sensing technology based on Brillouin scattering can realize distributed strain measurement, but it’s always low in the signal-to-noise ratio (SNR) and measurement accuracy, so the application is limited. In this paper, a distributed strain measurement method for bridge based on weak FBG (WFBG) array is proposed and verified by experiments. The continuous beam test results show that, the good sensing performance is demonstrated by grating array strain cable which can accurately measure the strain distribution of continuous beam, and the load point can be located by the strain cable, and its positioning accuracy is 0.5m, and the sensitivity of the cable is about 1.25με/pm. The test results of real bridge show that strain distribution of the whole bridge under dynamic and static load can be measured, and the maximum deviation of dynamic and static measurements is 6.8% and 5.6%. The temperature compensation method is proposed for the temperature influence in the test process, and the effect is good. In conclusion, the feasibility of the distributed strain measurement method of bridge based on weak FBG sensing has been verified.