Visualization of Damage Detection for Circular Arch Based on Stochastic Subspace Identification

When performing vibration tests on civil engineering structures, it is often unpractical and expensive to use artificial excitation (shakers, drop weights). Ambient excitation on the contrary is freely available (traffic, wind), but it causes other challenges. The ambient input remains unknown and the system identification algorithms have to deal with output-only measurements. The empirical mode decomposition (EMD) based stochastic subspace identification procedure utilizing operational vibration measurements is presented in this paper. The SSI method is then applied to the decomposed signals to yield the modal parameters of the hinged circular arch which is divided into sixteen elements, and then the strain mode shapes are obtained. In order to let the non-specialist to understand the message of the damages, the strain modes of the arch are presented with visual images. Visualization of damage detection has great potential for development of On-line structure health monitoring.