The Application Of Grillage Method Of Analysis For Skew Bridge Structure During Construction Stage

In recent years, with the rapid development of transportation and urban construction in our country, bridge construction has come into a new stage of rapid expansion. Urban construction of the highway departments have fully changed the viewpoint that the road line must submit to the bridges. For this, the skew bridge's proportion of the bridge is increasing, especially on highway bridges,urban viaduct and interchange bridges.The structure and mechanical properties of skew bridges is different from the orthogonal bridges, but now research on skew bridges is not comprehensive, and it is more difficult to design this bridge structures than orthogonal and regular structures. Therefore, it's very important and practically significant to obtain a convenient and accurate analysis for the development of skew bridges.The grillage method is a practical and effective computer-based spatial analysis method for the superstructures of bridges. The method is legible and easy to understand and implement. Its basic principle is to simulate the structure with equivalent beam grids that can be easily handled by computers so that the structural characteristics and internal stress can be obtained. Its main idea is to simulate the superstructure with a equivalent beam grids, and to focus the bending stiffness and torsional stiffness in the plate or box girder segments on the nearest equivalent beam grid.The thesis analyzes skew bridge with grillage method, supported by the construction project of Jia Luhe River Bridge in Zhoukou City in Henan Province. It presents the basic principles of shear-flexible grillage method for analysis of skew multi-cell box girder bridges in details. This thesis also introduces the method that how to divide the grillages. The element stiffness matrix is derived, and then the global stiffness is formed. In this thesis, the finite element models based on grillage and single girder method are both established by software MIDAS/CIVIL, and then Three-dimensional solid model is established by software ANSYS. The analytical results of the three methods mentioned above show that variations of deflection and stress are the same by and large, but Grillage method model is more closer to three-dimensional solid model. In the analysis of the skew bridge with gradient of negative 20 degrees during construction stage, Grillage method model is good at reflecting the mechanical properties and Loading characteristics of skew bridge, and the accuracy meets the need of engineering requirements.