Iterative constrained optimization scheme for model updating of long-span bridges

This paper presents an iterative constrained optimization scheme for the finite element (FE) model updating of long-span bridges. The objective is to minimize the differences between the calculated and the measured frequencies by changing some selected structural parameters in the FE model. An eigenvalue sensitivity matrix is first obtained from the first-order Taylor series expansion of the eigenvalues with respect to these selected parameters. A set of linear equations relating the perturbation of parameters to the differences between the calculated and the measured frequencies is then established. The selected parameters are assumed to be bounded within some prescribed regions according to the degrees of uncertainty and variation existing in the parameters based on some engineering judgement. The changes of these parameters are found in an iterative fashion by solving a quadratic programming problem. This model updating scheme is applied to both a 1/150 scaled suspension bridge model in the laboratory and an actual cable- stayed bridge in the field. The results show that the natural frequencies calculated from the FE models after this updating process can be quite close to those of the measured values.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.