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The damage identification method based on macro-strain modality has shown good results for large-span flexible bridges. However, medium- and small-span bridges have a high stiffness, and the axle system is embodied. The strong time-varying vibration characteristics, coupled with the non-stationary characteristics of vehicle loads, make it difficult to accurately determine the stable strain modes of such bridges. To solve this problem, a damage localization index in the form of an amplitude vector matrix of the mutual energy density spectrum based on macro-strain was constructed using wavelet transform de-noising and reconstruction technology and cross-correlation function. The macro-static strain and macro-dynamic strain data obtained from a vehicle–bridge coupling experiment were reconstructed through wavelet transform, and the factors influencing the damage indices were analyzed. The results showed that the proposed indicators could help realize an accurate damage localization for medium- and small-span bridge systems with different damage degrees under the action of vehicle–bridge coupling.

A comprehensive comparison of macro-strain mode and displacement mode obtained from distributed macro-strain sensing and high-density point sensing (such as accelerometers) technologies is presented in this paper. Theoretical derivation reveals that displacement mode shape from accelerometers and modal macro-strain from distributed macro-strain sensors can be converted into each other. However, it is realized that displacement mode shape as global behavior of a structure can still be calculated with high-precision from modal macro-strain considering measurement errors in practical monitoring, whereas modal macro-strain can hardly be accurately achieved from displacement mode shape when signals are corrupted with noise in practical monitoring. Simulation and experiment results show that the calculated displacement mode shapes are very close to the actual ones even if the noise level reaches 5%. Meanwhile, damage index using measured modal macro-strain is still effective when the measurements are corrupted with 5% noise which is reliable for damage detection in practical monitoring. Calculating modal macro-strain from noise-polluted displacement mode shape will cause an unacceptable error if the noise level reaches only 0.5%, which has been verified in the simulation. [ABSTRACT FROM AUTHOR]

The damage identification method based on macro-strain modality has shown good results for large-span flexible bridges. However, medium- and small-span bridges have a high stiffness, and the axle system is embodied. The strong time-varying vibration characteristics, coupled with the non-stationary characteristics of vehicle loads, make it difficult to accurately determine the stable strain modes of such bridges. To solve this problem, a damage localization index in the form of an amplitude vector matrix of the mutual energy density spectrum based on macro-strain was constructed using wavelet transform de-noising and reconstruction technology and cross-correlation function. The macro-static strain and macro-dynamic strain data obtained from a vehicle–bridge coupling experiment were reconstructed through wavelet transform, and the factors influencing the damage indices were analyzed. The results showed that the proposed indicators could help realize an accurate damage localization for medium- and small-span bridge systems with different damage degrees under the action of vehicle–bridge coupling. [ABSTRACT FROM AUTHOR]