Dynamic investigation of a concrete footbridge using finite element modelling and modal analysis

In this article, the application of a manual updating method for finite element (FE) model updating of a concrete footbridge using modal analysis approach is described in detail. An FE model was developed using DIANA (FEM software package) to estimate the response of structure under free-vibration analysis. Afterwards, ambient vibration test (AVT) was conducted to extract the dynamic properties. The fundamental mode shapes of the structure were successfully identified applying ARTeMIS (modal analysis computer program). The mode shape pairs of initial FE model and a complete set of test results were employed for manual updating. A parametric study was carried out to specify the most sensitive parameters of the model. For this purpose, boundary conditions, mass density and Young's modulus of elasticity were examined as uncertain parameters. Attempts to calibrate the primary FE model revealed that the spring constants of supports were the most effective parameters for updating process. The FE model was calibrated considering three main criteria consisting of combination of natural frequencies/mode shapes and modal assurance criteria (MAC)/mode shapes. The calibration strategy performed in the present study, including parametric study on uncertain parameters of initial FE model, parameter and target response selection and MAC calculation based on modified formulation, has been discussed. The updated FE model and the measured mode shape counterparts exhibited very good correlation.