Geometry Nonlinear Static Analysis For A Hybrid Girder Cable-stayed Bridge At Construction Stage

Steel and concrete composite structure is a new structure system which is better than steel structure and reinforced concrete structure, it can give full play to advantages of the steel and concrete and overcome the disadvantages of both. Hybrid girder cable-stayed bridge have gradually become the future development direction of the large span bridge with its unique structure and technical features. Because of flexible structure and component with internal force and deformation characteristics of the compound, after imposing static load, structure and axis of the main parts and the configuration of hybrid girder cable stayed bridge will change a lot. At this time, the analysis of hybrid girder cable stayed bridge has different situation from a linear analysis:There is not linear proportion relationship between force and deformation; It express the deformation of the structure by high times equation; the effect of increase or decrease of load can not simply added together. Therefore, We need to geometrically nonlinear analysis on the hybrid girder cable-stayed bridge.The main content of this article is geometry nonlinear static analysis for a hybrid girder cable-stayed bridge at construction stage.Firstly, as the foundation of the research results by previous people, the author analyzes the general situation of the development and the status quo of the theory of Hybrid girder cable-stayed bridge Theory of Calculation.Secondly, the authors studied the basic theory of the geometrically nonlinear analysis of cable-stayed bridge and described the three main factors affecting geometric nonlinearity of the cable-stayed bridge:large displacements, cable sag effect and beam-column effect, describes the finite element analysis method of these three factors and solving method of geometric non-linear equations.Thirdly, the authors studied hybrid girder cable-stayed bridge’s unique construction characteristics of Guang Fu River Bridge, established a simulation model using the finite element program the Midas/civil2010, and carried out linear and nonlinear calculations of the typical construction process of the bridge. The focus of the nonlinear calculation is the effect of cable sag and structure of the large displacement effect. Combined with the calculation of full-bridge construction process, analyzing the influence of geometric nonlinear for the main beam vertical displacement, the construction phase of structural deformation, the influence of internal forces and stress, during construction of hybrid girder cable-stayed bridge, and got the following conclusions by analying an comparing the results:①In the nonlinear factors the greatest impact to the Primary beam moment is the cable sag effect, followed by a large displacement effects.And influence in the various stages of construction is not the same degree.②Under constant loads, cable sag effect is the main source of geometric nonlinear, beam-column effects and the large deformation effect is relatively small. If only for linear analysis, the error of the calculated results will be large.The final research projects:On the basis of summing up the present common methods, using dress-Flip iterations, with the aim of smallest maximum deflection of tower and beam as well as smooth internal forces stress, to determine the initial tensile force of the cable-stayed. Adopted the cable force got by dress calculation, constantly calculating to determine the initial tensile force of the construction phase of cables.