A finite element model updating method using experimental modal parameters applied on a railway bridge

A finite element model updating method using experimental modal para- meters is presented. Such a procedure can be regarded as an optimisation problem. The objective function consists of the (weighted) sum of differ- ences between the experimental modal data (eigenfrequencies and mode- shapes) and the corresponding analytical predictions. The function can be completed with additional orthogonality conditions. The updating para- meters are the uncertainties of the model, which are changed locally until the objective function is minimised. A gradient-based algorithm is used to solve the optimisation problem. As a result a physically more correct model is obtained on which further analysis can be made. The presented proce- dure is applied on a railway bridge at Xntoing. Belgium, on which dynamic measurements have been made. Several variants of objective functions are minimised and the results are compared.