| As a new type of steel concrete bridge structure,composite box girder with corrugated steel webs(CSW composite box girder)has the advantages of economy,high efficiency and simple construction,which is in rapid promotion and development at home and abroad.For the whole structure,corrugated steel webs and concrete roof slab are connected by the shearing connection,which leads to the reduction of torsion of box girder.The torsion and distortion effect of composite box girder with corrugated steel webs under load are not negligible.In this dissertation,the composite box girder with single box linear corrugated steel webs is taken as the research object,and the box girder is studied mainly from two aspects of constraint torsion and distortion effect.The restrained torsion of composite box girder with CSW is analyzed.Firstly the section shape of composite box girder is assumed to remain unchanged under load,and based on the pure torsion theory,the shearing deformation of section produced by torsion is considered.And then the formulas for calculating the normal stress,the shearing stress and the differential equation of the restrained torsion are derived by using the stress-strain relationship and the warping stress of the thin-walled structure in the section of composite box girder satisfy the self equilibrium condition,and the differential equation is solved by 4 initial parameters: torsion angle,warping displacement,warping moment and torque.At the same time,aiming at the torsional geometric characteristics of composite box girder with CSW section is needed for the constrained torsion problem,the simple formula for torsion center,principal sector coordinate,principal sector moment of inertia and principal sector static moment are derived by selecting auxiliary poles and the correctness of formula is verified through numerical examples in this dissertation.The change of warping moment along the beam length when the central torsional moment of freely supported beam at midspan is analyzed by combining with example,the influence law of the corrugated steel web angle on the torsion geometrical features for section and the change for flange width and higher beam parameters on torsional warping normal stress are revealed.The distortion effect of box girder with CSW is analyzed in this dissertation,and the relationship between the two parts of the steel plate and the concrete floor is established,the calculating formulas of the distortion center and the stress ratio of the angle of the box girder and the intertia moment of the composite box girder are derived,through defining the distortion angle γD of the distortion center in of the concrete top and bottom and the CSW,and the shearing strain due to the distortion of the deformation deformation is neglected.Based on the principle of minimum potential energy,the differential equation is solved by using the distortion angle,distortion warping displacement,distortion warping moment and distortion moment as the initial parameters,and the formula for calculating the distortion normal stress of composite box girder with CSW is derived.The distortion normal stress calculation of the beam is compared with the results of the traditional concrete box girder,which shows that the torsional performance of composite box girder is notable with the decrease of CSW.At the same time,the correctness of the method in the dissertation is verified by the analysis of a numerical example,and the results obtained by this method are in good agreement with the calculated values of Ansys and the calculated results in other literatures. |
