Analysis Of Distortion Effect And Diaphragm Settings On Steel Box Girder Of Chongqi Bridge

Steel box girder due to the structure of light weight, high torsional rigidity, the advantages of convenient construction and maintenance has been widely used in today’s large and medium span Bridges. But because of its typical thin-walled structure, the section shape will change and produce distortion stress under eccentric load, and certain distance of diaphragm in the steel box girder can effectively guarantee section shape so as to reduce the influence of distortion. Diaphragm is closely related about steel consumption and torsion of Steel box girder, fatigue of bridge deck. Therefore, Europe, Japan gives the diaphragm stiffness and spacing requirements as well as the calculation method of distortion warping stress by a lot of research of steel box girder. However, according to the specification of Japan or Europe, stiffness of truss type diaphragm is difficult to meet the requirements.Based on Chongqi bridge as the background, this paper studied the relationship of the distortion. the stiffness and spacing about diaphragm in Steel box girder. The specific contents are as follows:(1) Summarize the relevant regulations of steel box girder diaphragm on the foreign and domestic theory of analysis to the distortion of the thin-walled box girder;(2) According to the BS5400and Japanese standards on the main method of controlling steel box girder distortion and the corresponding requirements, analyzes the existing problems in the diaphragm;(3) Setting up the finite element model of different diaphragm spacing and type and the stiffness under the research background of the Chongqi bridge, Obtaining the relationship between distortion and diaphragm in Steel box girder, stress and distortion of eccentric load are analyzed. Calculation shows that, for the Chongqi bridge, the diaphragm stiffness is not meet Japanese standards, but the distortion stress canbe controlled in low level.