Study On Torsional Mechanical Performance Of Curved Composite Box Girders With Corrugated Steel Webs

As a new type of structure,composite box girders with corrugated steel webs have a series of advantages,such as lightweight,high efficiency of prestressing force and pretty appearance.In recent years,corrugated steel webs have been applied to curved composite box girders.However,the longitudinal stiffness of corrugated steel webs is small.And the shear stiffness,torsional stiffness and distortion stiffness of its are lower than concrete box girder,so the torsional effect of composite box girder with corrugated steel webs is more prominent.And because of the bending-torsion coupling effect of curved beams,the torsion effect of curved box girder with corrugated steel webs is more significant.In this paper,theoretical research and analysis on torsional mechanical properties of curved box girders with corrugated steel webs are carried out.The main research results are as follows:(1)Based on Umanski's second theory,the differential equations for the restrained-torsion of the curved composite box girder with corrugated steel webs is derived.According to the orthotropic characteristics of corrugated steel webs and the mechanical properties of curved box girders,combined with boundary conditions,the calculation methods of restrained torsional normal stress and shear stress of composite box girders with corrugated steel webs are given.Based on the analysis of restrained torsional shear stress,the formulas for calculating the free torsional shear stress in restrained torsional shear stress and the secondary shear stress caused by the change of warping normal stress along the longitudinal direction are derived.The influence of different curvature radius on the torsional performance of composite box girder is analyzed,and the difference of torsional performance between curved composite box girder with corrugated steel webs and concrete box girder is compared.(2)Based on the mechanical characteristics of composite box girder with corrugated steel webs and the theory of box girder,the strain of composite box girder with corrugated steel webs under distortion is obtained.The distortion control differential equation of curved composite box girder with corrugated steel webs is deduced by the energy method.The calculation methods of distortion angle,distortion double moment and distortion warping stress are obtained when the curved composite box girder with corrugated steel webs is distorted.The influence of curvature radius on its distortion performance is analyzed,and the difference of distortion performance between curved composite box girder with corrugated steel webs and concrete box girder is compared.(3)The relationship between vertical displacement and torsional angular displacement of curved beams under load is obtained by Vlasov equation,and the coupling force characteristics of curved beams under bending and torsion are verified.Combining with the cross-section characteristics of composite box girders with curved corrugated steel webs,the deflection,rotation angle and internal force of curved beams are obtained by using the closed solutions given by Heins and Spates.The influence of curvature radius curve on bending-torsion coupling effect of curved composite box girder with corrugated steel webs and curved concrete box girder is compared.