Mechanical Characteristics Analysis Of Beam Of Nuer River Cable-stayed Bridge In Jinzhou

Cable-stayed bridge is a main style of long span bridge, and is widely applied in practice. Bearing the weight loading of cars, the beam and its connected attaching items is one of the main stress bearing components for the cable-stayed bridge. The box girder has been used widely in modern cable-stayed bridges due to its excellent structural performance. The stress distribution of section in wide and thin box grider subjected to simultaneous bending and axial force doesn't conform to the assumption of the plane section, and the transverse stress distribution is uneven; with the increasing of bridges' span and the lowering of security repertory, to consider the uneven of stress distribution in calculation of design and construction control, and to analyses the shear lag effect are bound to have important engineering value and theorical significances.Nuer River Bridge in Jinzhou City is taken as an engineering example in this paper. It is a concrete cable-stayed bridge with single taper tower and double sloped cable planes, which is 120 meter. Section of beam is double-boxed with three cells. With lots of prestress cable built in the sterna and cross slab, the beam is designed uniquely and stress-bearing complicatedly. So the spatial stress analyzing of beam is significant, especially the shear lag effect of beam.After systematically expatiating on the previous analytical theories and methods of calculation of shear lag effect, the thesis selects spatial finite element method to study the shear lag effect of main grider with double boxes and three-celled used in cable-stayed bridge. This thesis presents "illustration method" which describes the shear lag effect of main grider with double boxes three-celled by the transverse distribution chart of longitudinal stress and shear lag coefficient. The main research work covers the following aspects:(1) Based on the spatial finite element method, the thesis adopts the program-ANSYS to analyze the shear lag effect of main girder with three-celled double boxes in the finished state. Considering the characteristic of the shear lag effect of main girder the thesis presents "illustration method" which is a method describes the shear lag effect of main girder. As a result, under consistent loading, the roof and the base plate of the beam are both get stress within the specification. The shear lag has effect is not obvious and the max shear lag coefficient for each base plate section is below 1.04. While the shear lag effect is noticeable near to both ends of roof plate with its coefficient above 1.2. Observing from the ends to midspan, the stress is leveling and it is not obvious for the shear lag effect.(2) Based on spatial finite element method, parameters analysis of affecting factor to shear lag effect is performed in the main structural dimension, design of longitudinal and transverse pre-stress etc. As a result, the stress of roof plate is not level for the section near to the fixing tips after they are applied with vertical prestressing force. But the stress of base plate is far more obvious. Contrasting with fixing tips, for section near to the freely supported tips, the stress of roof plate is more level, but not level for base plate. As the same time, it is always level on roof and base plate for other sections. Applied with lateral prestressing force, the roof stress on each section is level while base plate not.The laws in this paper can be used as the basis of design of main girder for this bridge, and is useful for directing research and analysis of such kind main girder.