Superelement-coupled Virtual Distortion Method Oriented To Finite Element Model Updating Of Bridges

For practical bridge structures, the features like complex scale and enormous degrees of freedom(DOF) would undoubtedly lower down the calculation efficiency of structural finite element model(FEM) updating. In order to solve this problem, a new FEM updating algorithm based on superelement-coupled virtual distortion method(SVDM) has been proposed in this paper, moreover, its application in both FEM updating of damaged bridges and precise modeling of bridge structures.The algorithm theory of superelement static condensation has been thoroughly discussed, also the core conception of VDM on link and beam elements analyzed. Especially, the construction and selection of main virtual distortion on superelement substructure has been elaborated, contributing to the proposal of SVDM-based bridge structural FEM updating algorithm. Therefore, the calculation efficiency of FEM updating would be improved by reducing the structural DOFs and avoiding the reconstruction of stiffness matrices under given accuracy requirements.Based on the theory of this algorithm, two kinds of practical application of SVDM have been focused both on FEM updating of damaged bridges and precise modeling of bridge structures. Aiming at the structural and mechanical features of different practical bridge structures, the main structural DOFs would be selected and the primary characteristic deformation reserved. The rational settings of initial value and threshold of the updating parameters should be arranged considering the specific items of the subsequent model updating objectives. Additionally, the sensitivity of structural response is calculated by complex perturbation theory, and the SVDM meta-models have been respectively constructed on both solid elements of a damaged bridge and composite-section elements of a precise bridge model.According to two practical bridge engineering projects, the above SVDM meta-models would be applied in model updating, and the algorithm validity has been verified through the measured data of the damaged Wohong Bridge in Shuang Yashan and a viaduct in Changchun. The results have showed superior calculation efficiency of SVDM meta-model and satisfactory updating performance. Updated FEM could not only present the mechanical state of practical bridge structures precisely, also offer theoretical support to the following structural security diagnosis and pre-warning. The SVDM-based FEM updating algorithm is suitable for the model updating problems in solid elements and composite-section elements.