Detection of Interface Damage of Composite Structure Using FBG Sensing

Fiber Bragg grating (FBG) sensors used for detecting interface damage of steel-concrete composite bridge deck model was tested. The interface damage includes slippage and disengage. The tests cover three stages: dead load tests, fatigue tests(3 × 106 cycles) and destructive tests. In the fatigue test stage, dynamic loads with equal amplitude harmonic wave were added. During the destructive test stage, slippages and disengages occurred one after another and were measured by the FBG sensors. The critical strain values of the two kinds of interface damage were detected. The experimental results and the data obtained in the three stages show that in the first two stages no damage occurs, strain data measured by FBG sensors are consistent with those measured by resistance gauges and the FBG sensors can trace the development processes of the damage. Until the bridge deck model is totally damaged, the FBG sensor system remains proper working status and the data measured are consistent with the result inspected by eye. The results show that interface damage can be detected successfully by the FBG sensing. This work is useful for the structural health monitoring and the optimum design of composite structure.