Torsion Effect Analysis Of Composite Box Girder With Corrugated Steel Webs

Box girders are widely used in bridge structures because of their good mechanical performance.In order to improve the self-gravity of traditional box girders and avoid the cracking of webs,a composite box girder with corrugated steel webs instead of concrete webs appears.Although the torsion performance of composite box girder with corrugated steel webs has been analyzed and studied in existing literatures,the distribution of torsion shear stress calculated in some literatures on the cross section is obviously unreasonable(shear stress also appears at the end of cantilever plate).Therefore,it is of practical significance to study the torsion shear stress calculation method of composite box girder with corrugated steel webs.Based on the theory of restrained torsion of thin-walled box girder and combined with the structural characteristics of composite box girder with corrugated steel webs,the normal stress and shear stress of restrained torsion warping theoretically were deduced,and the formula for calculation of relevant parameters are determined explicitly calculated the fan static moment and generalized the fan static moment when calculate since contour coordinates of point location,combined with a numerical example,the correctness of the method in this paper been verified.The main research work and relevant conclusions are as follows.(1)With small span corrugated steel web composite box girder is taken as an example calculation of cross section in the constraints on torsional stress.Based on A.A.the second Umansikii theory,connecting with the corrugated steel web composite box girder cross section of the mechanical characteristics the stress calculation formula is deduced,using the initial parameter method to solve the differential equation of the constrained torsion,draw on the cross section in the torsion Angle,equivalent double torque,torque,according to has the stress calculation formula is deduced,the theoretical calculation results are obtained.(2)By reasonably selecting the starting point of the circumferential coordinates of the sector static moment,more reasonable and accurate theoretical value of torsional shear stress can be obtained,and compared with the calculated value obtained by using the finite element software ANSYS,the torsional shear stress has the same change rule.The maximum value of the torsional shear stress of the section is found in the corrugated steel webs,which is consistent with the main resistance of shear force of the steel webs,and the variation law of the section stress is basically consistent with the results obtained by the finite element method.(3)By using the finite element software ANSYS to establish the small span corrugated steel web composite box girder geometric model,by changing the section aspect ratio,the cantilever plate width and the corrugated steel web thickness way,studies the warping normal stress and torsion shear stress on the mid-span section under the action of partial load,andobtains the related conclusion.It is found that with the change of section parameters,namely the increase of width to height ratio,both the restrained torsional normal stress and the shear stress change greatly,and the normal stress continuously converges to the left and right edges of the beam.When the aspect ratio reaches 4:1,the stress value of the cantilever end basically reaches twice that of the closed beam body,which indicates that the torsion resistance of the wide beam is very weak.However,the torsional shear stress on the section increases continuously at the corner point of the roof and floor,and the torsion effect is very saliency.For the combined box girder with corrugated steel webs,the change of cantilever plate width has no obvious influence on the stress on the section,and when the thickness of corrugated steel webs remains at about 10 mm,the torsion effect on the section of the beam is reduced appropriately,and the economy of the material can be guaranteed.