Health monitoring of a smart base isolated benchmark cable-stayed bridge using symptom approach

This paper presents a smart base isolation system for cable-stayed bridges, which consists of passive hysteretic devices between the deck and the piers. The ASCE benchmark cable-stayed bridge is used as case study and a more accurate model in ANSYS with nonlinear geometries, cables refinement and soilstructure interaction capabilities is used for comparison purpose. The monitoring of the bridge is approached in the symptom space, assuming that the bridge degrades and deteriorates with time. The damage to the longitudinal isolators between the deck and the pier is considered. It consists in 42 observations throughout the life span of the bridge. Excitation is applied in the time domain in the form of traffic load. This is simulated as translating white-noise load intensity fields. The symptoms considered in the case studies are vibration related parameters and displacement measures at selected position along the deck. Symptoms are ordered in a rectangular symptom observation matrix (SOM) opportunely normalized. By successive application of single value decomposition, it is possible to pass from multidimensional non-orthogonal symptom space to orthogonal generalized fault space, of much reduced dimensions. These information are useful for redesign of conditional monitoring systems.