Finite Elements Modeling And Updating Of The Girder Bridge And Its Applications

Nowadays, there are many prestressed concrete bridge in Chinese transportation lines. In their surviving period, they are inevitable affected by a lot of adverse factors, such as environmental erosions, long term loading and material aging, so as to decrease their loading capacity. And the in-site detections are hardly to assess the damage of bridges precisely. But the combination between the numerical modeling and the undamaged detection for bridges can detect damages, assess and predict functions for the structures of bridge with the development and applications of the finite-element (FE) method, which makes the numerical modeling for bridge structures possible. The combination also raises the scholars’attentions from many countries.It is vital to establish a finite-element model that can guarantee the engineering precision to conduct the analysis. This paper, based on Zhonghua Bridge, uses the general finite-element software Abaqus to establish the refined finite-element model for the bridge. Through the comparison between the FE results and the detected static/dynamic property, this paper explains the boundedness of the engineering FE model and the effectiveness of the refined FE model. The influence of deck, prestress loss and element partition on modal frequencies and mid-span deflections is also argued.There exists, inevitably, the difference between the FE model and the bridge in-site since the FE model is based on the design and the in-site bridge is limited by the construction. So on account of the Respond Surface Method in the Orthogonal test, this paper:1calculates the significance of the design factors with the result of numerical examination;2selects the factors with large significance to modify the model;3establishes the Response Surface model;4assesses the Response Surface model through the determining factors and root-mean-square error(RMSE). The refined FE model is modified by the Response Surface method and the Genetic Algorithm. The detected modal frequencies and the static mid-span deflection are compared with the results from the refined FE model, giving the following conclusions:1the modification efficiency increases with the Response Surface method and the Genetic Algorithm;2the accuracy can meet the demand for engineering applications;3the modified FE model can precisely predict the real static and dynamic properties of the bridge;4the modified model can be used to detect damage, assess function and analyze fatigue for the bridge.Based on the modified model, the ultimate load capacity and the dynamic response under the fatigue vehicle load are analyzed. The remaining load capacity and stress/fissure distributions are given through the ultimate load analysis in order to display the damaged parts or sections and to refine design. Through dynamic response under fatigue vehicle load, the stress in the key parts and the changes of the mid-span deflection are derived for the further fatigue analysis for the bridge.