Vibration-based Damage Localization in a Cable-stayed Bridge

In this work the numerical model of an existent cable-stayed bridge, subject of an international benchmark, is adopted as a case study. The original benchmark finite element model is modified implementing new issues in the simulation of the bridge dynamics. First, the seismic motion has been improved accounting for its space correlation and for its three-dimensionality. Secondly, the cables-deck dynamic interaction is improved by refining the cable modeling. Finally, the finite element formulation of the bridge deck, which is composite concrete-steel, is improved to accounts for a complete correspondence between structural and finite elements. The model is used to simulate the structural response of the structure in the undamaged state, and in several different damaged ones, under a seismic excitation having the intensity of after-shock events. Several locations of the damage have been considered to highlight the performance of the adopted damage localization method, namely the Interpolation Damage Detection Method (IDDM). This belongs to the so called “Level 2” family, since is able to detect both existence of damage and its location. The efficacy of the proposed method is assessed with respect to several scenarios of damage ranging form single to multiple damaged location with increasing severity of damage. The reliability of the Interpolation Damage Detection Method has been numerically verified by simulating damage through a reduction of stiffness in one or more elements of the deck, that is the steel members of the mixed concrete-steel deck of the bridge. Results show that, with reference to the numerical examples herein proposed, the IDDM can provide the correct localization of damages.