A localized vibration response technique for damage detection in bridges

Traditional techniques for damage detection in civil infrastructures that are based on the global vibration response of the system are limited in their capabilities to detect damage. Because damage detection based on the global vibration response relies on global parameters to describe the dynamic behavior of local structural elements, it suffers from limiting factors such as poorly-formed aggregate system models, very low signal to noise ratio, unrealistic boundary conditions. An alternative to the use of global detection techniques is the use of an adaptive local analysis technique based on the local response of the structure. This is achieved using wavelet packet decomposition at the sensor outputs and interpreting this decomposition as a subband framework for a bank of adaptive beamformers. The beamformer adaptive processors guaranties the maximization of the output SNR and in the same time allows for spatial selectivity and a highly directive vibration response in the structure. Scanning the structure over time produces a detailed vibration signature of the structure. The structural damage can be localized with high probability by comparing two vibration signatures before and after the damage occurs.