Super Element Method For Suspension Bridge With Plate-Truss Composite Stiffening Girder

The plate-truss composite structure has broad application prospects in suspension bridges. It can improve the stiffness of the structure, reduce the dead load, thus decrease the engineering cost. However, the plate-truss composite stiffening girder has a lot of components. It leads to large computational work when earring out refined analysis using conventional beam elements and shell elements, due to the increasing of degree of freedom and the large size of global stiffness matrix. As a result, too much memory and time will be cost during the computational process. In this thesis, a super element for the analysis of plate-truss composite stiffening girder is proposed to reduce the size of the global stiffness matrix and save the memory as well as the computation time, while the accuracy can be also guaranteed.The main contents of this thesis can be summarized as follows:Firstly, the shell element was studied based on the finite element method. The shell element was developed by the combination of an 8-node Serendipity element and a 9-node Heterosis element. This element is a quadratic isoparametric element, which has good adaptability to the irregular geometry, and has high precision.Secondly, by taking the stiffening girder segment of Guiweng high way Qingshui River Bridge as the example, the super element was condensed by employing the substructure method. On this basis, the analysis program was developed by C++language, in order to achieve the condensation and calculation of the super element. The correctness was verified by numerical example analysis. Results showed that the super element can significantly reduce the size of the stiffness matrix as well as the memory consumption. It has obvious advantages in the calculation of large-scale structures, especially with repeated cells. Thus the super element is suitable in the analysis of plate-truss composite stiffening girder.Lastly, this thesis proposed an optimal erection scheme, in which the appropriate opportunity for the girder segment rigid connection was determined, according to the variation law of the girder shape during erection process. In this part, the super element program was combined with BNLAS software, and the erection scheme of Qingshui River Bridge was calculated. By this technique, the analysis of suspension bridge with plate-truss composite stiffening girder was implemented, using the proposed super element method. From the results, the significance of super element method was outstandingly revealed.