Ansys Of Shear Lag Effect Of W-Shaped Section Beam

The shear lag effect in wide box girder bridges will lead to stress concentration on the top and bottom of the box girder,causing structural cracks and damage.In practical engineering applications,diaphragms are usually added to the main girder to reduce shear lag effect.A concrete single cable plane cable-stayed bridge in Baoding City,Hebei Province,adopted a new type of main beam section—the W-shaped section(the box girder section with two inclined webs),and no diaphragm was installed,only depend on the W-shaped section main beam itself to resist the shear lag effect.At present,the theoretical research and application of the W-shaped section shear lag effect are still few.Based on the background,this paper studies the shear lag effect of W-shaped section,the research contents are as follows:(1)This paper introduced the stress characteristics of box girder structure,the basic concept of shear lag effect and effective width method for dealing with shear lag effect in engineering application.(2)Firstly the classical energy variational method was used to derive the shear lag effect of the straight web box girder,and the corresponding differential equation and natural boundary conditions were obtained.The theoretical analysis of the classical energy variation method and the spatial finite element calculation are carried out with the simple-supported beam of the straight-web box section as an example.The two methods have obtained a more consistent result.Then based on the classical energy variational method,three different longitudinal displacement difference functions were proposed to describe the wing plate displacement,and the classical energy variation method was improved to solve the shear lag effect of the W-shaped section.Taking the W-shaped section simply supported beam as an example,the theoretical analysis of the energy variation method and the space finite element method were carried out.The analysis results showed that for the inclined web box girder such as W-shaped section,the accuracy of the traditional variational method was lower,and the improved variational method should be used for stress calculation.(3)The finite element analysis of shear lag effect of simple support model was carried out by Midas Civil engineering software.The shear lag effect of W-shaped section simply supported beam and straight web section simply supported beam under uniform load and concentrated load was analyzed.The results showed that the shear lag effect in the W-section beam is weaker.And the influence of the diaphragm on the shear lag of the two sections was investigated.The results showed that the diaphragm has a greater influence on the shear lag of the section of the straight web.(4)Midas Civil engineering software was used to calculate the shear lag effect of the W-section cable-stayed bridge in Baoding,Hebei Province,and the main beam section was replaced with the straight web box section for comparative analysis.The results showed that the shear lag effect in the W-section without the diaphragm was not much different from the shear lag effect of the straight web section with the addition of the diaphragm.