An iterative multilevel updating scheme for vibration-based damage assessment of a prestressed concrete girder bridge

For vibration-based structural health monitoring, a multilevel optimization scheme is applied to damage assessment of a prestressed concrete bridge. As a linear elastic problem to be addressed, damage was represented by reduction of structural stiffness of the reference model for the elements where the damage occurred. The Finite Element (FE) model updating problem is formulated as a nonlinear least-squares problem, which tries to minimize the differences between the reference model and the real (or simulated) structure with respect to the modal data. Due to the specific structure of the bridge, damage parametrization was introduced both using substructuring and a damage function. Consequently, the optimization variables were divided into global ones and local ones, which leads to the implementation of an iterative multilevel updating scheme. Satisfactory results were obtained for two numerical simulated damage scenarios: one with a single damage and one with multiple damage.