Research On Multi-Scale Finite Element Model Updating And Validation Method Of Cable-Stayed Bridge

The structural health monitoring, damage prognosis and safety prognosis have become active issues of civil engineering in recent years. An accurate finite element (FE) model considering the characteristics of the global structure and the local details is one of the effective ways to achieve the goal of bridge health monitoring. In order to assure that the FE model can well reflect the current conditions of the real bridges, some effective FE model updating techniques should be used to improve the precision of the FE model. In addition, the updated model should be validated to consider the uncertainties of the parameters.In this study, Guanhe Bridge, a steel-concrete beam cable-stayed bridge in Yanhai expressway (G15) of Jiangsu Province, was used as the engineering background to build a multi-scale FE model. And then, the multi-scale FE model was updated and validated. The main work is as follow:1. The basic theory and simulation method of both the material multi-scale and structural multi-scale were compared to provide reference for structural multi-scale simulation.2. Structural multi-scale simulation was employed to implement the connection of different elements, so as to build the initial multi-scale FE model of Guanhe Bridge.3. With the analysis of the characteristics the multi-scale FE model and the error sources, the basic framework of two-phase model updating was established by using polynomial response surface method and support vector regression method, and then the updating of the multi-scale FE model of Guanhe Bridge was carry out.4. Based on the measured data of structural health monitoring system, the multi-scale FE model of Guanhe Bridge was validated from three aspects:correlation analysis of calculated result and test result, analysis of uncertainty quantification and propagation, and evaluation of the model validity.The main conclusion is as follow:1. With reference to the ideas of the multi-scale simulation of materials, the multi-scale FE model of Guanhe Bridge for structural health monitoring was built based on the Arlequin structural multi-scale simulation method.2. A two-phase model updating method of structural multi-scale FE model was proposed. In the first phase, the polynomial response surface method was used to update the FE model with the goal of large-scale model. The polynomial response surface method and the support vector regression method were applied to achieve the second-phase updating with the goal of the measured data, which established the forward and backward delegation models, respectively. After the two-phase model updating, the maximum error between the calculated and measured frequencies was reduced from 21% to under 3%.3. The overall frame of the multi-scale FE model validation was built, and the laws of uncertainty propagation were studied. Without considering the average absolute value of relative errors, the overlap ratio index of each modal frequency was over 75% in propagation forward, and the overlap ratio index of each structure parameter was over 65% in propagation backward. The result of evaluation of the model validity shows that the updated multi-scale FE model of Guanhe Bridge has higher precision in the whole parameters space. So the validated multi-scale FE model of Guanhe Bridge can be used to analyze damage prognosis and safety prognosis.