Wide Dwarf Tower Cable-stayed Structure Parameters And Wide Box Girder Shear Lag Effect In Research

Extradosed cable-stayed bridge is one of new bridge structures,which has been developing in recent twenty years. It has the structural characteristics of both continuous girder (continuous rigid frame) bridge and cable-stayed bridge. The structure possesses the very strong competitive advantage for bridges with span of 100～300 meters. So the structure is growing at a very fast rate, it has become a popular bridge structure. Taking the sifang which is located in Suijiang county, Yunnan province as the project background, Main works of the thesis are shown as follows.(1) Summarizing the design theory of wide box girders. Specially introducing the development of shear lag effect and the common solving method. According to the boundary conditions and the load conditions of sifang bridge, the formulas of cable/beam live-load ratio is deduced three bar stimulation analysis method are also deduced.(2) The three-dimensional beam element model of sifang bridge is builded up by using a finite element software called MIDAS/CIVIL. Analyzing the sifang bridge live-load effect, discussing the influence of live-load effect of Extradosed cable-stayed bridge when tower high, sectional area of cable and inertia moment of girder are changed respectively. Using feature parameters ato conclude the complex impact of Extradosed cable-stayed bridge, going for cable/beam live-load ratioη,and a,ηcan be critical value between Extradosed cable-stayed bridge and cable-stayed bridge. Discussing the rational value of the Length of Non-cable Area and the tower high of extradosed cable-stayed bridge.(3) The three-dimensional spatial solid element model of sifang bridge is builded up by using a finite element software called MIDAS/FEA. The shear lag effect of main girder of the sifang bridge' typical section is analyzd when the Material is elastic and nolinear.The results of elastic material compare with the three bar stimulation analysis method'results. The former value is greater than the latter,but it is very close between the two method. This means that three bar stimulation analysis method is conservative. At the same time, the results of the elastic'methods and the nolinear methods are compared,and the results show that a part of the concrete has entered the plastic stage,under the the most unfavorable load case of sifang bridge. stress distribution in plastic is More uniform. Finally, the local stress of the cable pylon anchorage zone is researched.