FE model updating used for damage assessment - Application to a highway bridge

In Finite Element (FE) model updating the val- ues of the uncertain physical properties of an engineering structure are adapted in the FE model such that the dif- ferences between the numerical and experimental vibration data are minimized. In civil engineering the discrepancies in the modal data, i.e. the eigenfrequencies and mode shapes, are minimized, which are mostly identified from ambient vi- brations. Since the modal data are nonlinear functions of the uncertain properties, an iterative sensitivity-based min- imization method is used to solve this inverse problem. The technique can be used for parameter identification in general; in the paper it is used for damage identification of civil structures, such as dams, bridges, monuments, etc. In particular, the damage pattern existing in the girder of a highway bridge is identified by updating the Young's and the shear modulus in the FE model of the bridge. In order to reduce the number of unknowns, damage functions are used, in the way that the updated stiffness distribution is approximated by a piecewise linear function.