Structural safety assessment oriented modal experiments on Renyihe Bridge using vehicle excitations

Abstract

High order modal parameters which are sensitive to local damages can be employed as useful structural health indicators for effective structural safety assessments of in-service long-span bridges. As a promising method to measure high order modal parameters of the full-scale bridge, the modal experiment using vehicle excitations draws the attention of engineering circle recently. However, this experimental method is currently subjected to a drawback which limits its usage, i.e., the weight and the location of the running vehicles adversely affect the accuracy of modal test results. To this end, a practical approach relying on finite-element (FE) model updating is proposed in this article to compensate for the deviation of the test results due to the adverse effects of running vehicles. The proposed method first uses the measurement change in the low order modal frequency to identify the equivalent vehicle weight on the bridge and updates the FE model, and then uses the updated FE model to predict the measurement change in the high order modal frequency and compensates for the measured high order modal frequency for use. Under the engineering background of Renyihe Bridge, a long-span concrete rigid-frame continuous highway bridge, the new approach to improve the accuracy of modal experiments using vehicle excitations has been presented. The results suggest that the bridge’s compensated 11th order modal frequencies measured on location for different cases are very close to each other, and they vary in the small range [3.80 Hz, 4.05 Hz]. The accuracies of these compensated modal experimental results are therefore validated by each other, and the method proposed for the improvement of the modal experiment using vehicle excitations based on FE model updating is thereby validated.