Study On Shear Lag Effect Of Typical Section Of Large-cantilever Wide Steel Main Girder Of Cable-stayed Bridge

The large cantilever wide steel box girder cable-stayed bridge is relatively rare in the current cable-stayed bridge structure.The structure is composed of a box-shaped main girder and a large cantilever welded on the outer web.It has many advantages such as light weight and large cross-sectional width,which can meet the current social demand for traffic.Due to the relatively large cross-sectional width and height of this structure,the shear lag effect is also particularly prominent.At present,this type of complex cross-section is difficult to calculate with theoretical formulas.In view of the fact that the width of the main girder section of the example project in this article is 49.60 m and the section structure is extremely complex,it is particularly important to analyze the shear lag effect of the main girder section under the action of multiple load mechanisms.This thesis briefly introduces the development history of cable-stayed bridges and the structural characteristics of the large cantilever steel box girder,summarizes the research methods and influencing factors of the shear lag effect,and proposes a method of combining finite element method and model test to study the shear lag effect of large cantilever wide steel box girder.The main research contents and conclusions are as follows:(1)The finite element model of the prototype structure segment was established by ANSYS,and the force status of the main beam of the prototype structure was analyzed.Five beam segments in the middle span with a larger cable force value of 60 m were selected for model test design.Considering the various factors of the testing site and the actual plate production size,the scale is scaled according to the ratio of 1:4.5.At the same time,a scaled finite element model was established,and compared with the stress results of the prototype bridge,it was found that the design of the experiment was more reasonable,the position of the maximum value of the cross-section normal stress was consistent and the value was equivalent.(2)A number of measuring points are arranged on the test model to test the normal stress of a typical section under various working conditions of dead load and live load.By comparing the test results with the theoretical calculation results,the following conclusions can be drawn.The theoretical method of using the spatial finite element method to refine the modeling and analysis of the shear lag effect of the steel main girder is correct.The maximum value of the normal stress of the roof is located at the position of the outer web,and the normal stress distribution of the roof shows a certain regularity.The value of the normal stress at the I-rib position of the floor is larger,and the maximum value of the normal stress of the floor is located at the position of the outer web.Compared with the normal load condition,the shear lag effect under the eccentric load condition is particularly prominent.The number of train lanes has a significant impact on the shear lag effect of the roof and floor.