Structural damage detection with distributed long-gauge FBG sensors under multi-point excitations

Distributed strain sensing techniques using long-gauge fiber Bragg grating (FBG) sensors have been widely applied in health monitoring of civil engineering structures. Developing an effective damage identification method based on the acquired macro-strain is a crucial issue for real applications. In this paper, based on the previous studies on modal macro-strain vector (MMSV) for damage identification under single-point excitation, the damage detection approach under multi-point excitations is further studied. An effective damage index is further proposed as an indicator of the structural damage and the frequency domain decomposition (FDD) technique is introduced to accurately extract the MMSV. The sensitivity and effectiveness of the proposed method for damage detection of a cantilever beam are verified in detail with both numerical simulations and experiments. Results show that both the single and multi damages with different damage extents can be effectively detected under either single point excitations or the wind load excitations. It shows that the proposed approach can do the work well and could be applied for the structural health monitoring of real structures.