Research And Analysis On Torsional Buckling Performance Of PC Composite Box Girders With Corrugated Steel Webs After Corrosion

Nowadays,domestic and foreign experts and scholars have achieved relatively mature theoretical and experimental results in the research of traditional corrugated steel web composite box beams.However,the research on the torsional performance of corrugated steel web steel bottom plate concrete top plate composite box beams is not yet mature.Especially,research on the restrained torsional mechanical properties of a new type of corrugated steel web steel bottom plate concrete composite box beam before and after corrosion is rare.Therefore,the mechanical characteristics of restrained torsion before and after corrosion of the corrugated steel web steel bottom plate concrete top plate composite box beam are analyzed and studied.The main analysis content is as follows:(1)Based on the Uzbek theory,the relevant formulas for restrained torsion of the composite box girder with corrugated steel webs,steel bottom plates,and concrete top plates are theoretically derived.A finite element model of the composite box girder is established using ANSYS finite element software,and the correctness of the theoretical formulas for restrained torsion before and after corrosion of the composite box girder is verified.(2)Take specimens of equal size for the same type of corrugated steel web steel of the model beam,and conduct accelerated corrosion tests on them using a neutral solution of sodium chloride.Control other variables in the accelerated corrosion test based on the humidity and temperature of a certain coastal area.Then,the weight loss rate of the corroded steel specimen is measured,and finally,the mechanical properties of the corroded steel specimen are tested.The relationship between the weight loss rate of the steel and the converted elastic modulus of the steel after corrosion is established.Finally,by establishing a corrosion time-varying model,the variation pattern of steel corrosion time and converted elastic modulus was obtained.(3)A corrosion aging model was established by conducting accelerated corrosion tests on corrugated steel web steel,and the converted elastic modulus of the steel after corrosion was obtained under different corrosion time limits.Combining the change rule of the reduced elastic modulus with time with the constrained torsion theory of the composite box girder,the theoretical analysis shows that the longitudinal apparent elastic modulus and effective Shear modulus of corrugated steel webs and orthotropic steel baseplates gradually decrease with the increase of corrosion time.Moreover,under the same constrained torsion concentrated torque load,the generalized sectorial moment of the composite box girder after corrosion gradually increases,and the bending torsion characteristic coefficient gradually decreases,The maximum restrained torsion double moment,maximum warping deformation coefficient,and maximum restrained torsion angle within the beam span gradually increase.After the corrosion of composite box girder,the warping normal stress on the concrete top plate of the midspan section gradually increases,while the warping normal stress on the steel bottom plate gradually decreases,and the restrained torsional Shear stress on the corrugated steel web hardly changes.(4)The variation law of the converted elastic modulus of the corrugated steel web after steel corrosion was obtained through accelerated corrosion tests.A finite element model of the corrugated steel web steel bottom plate concrete top plate composite box beam before and after corrosion was established using ANSYS finite element software.As the corrosion time gradually increases,that is,as the reduced elastic modulus gradually decreases,the deflection of the composite box girder gradually increases under concentrated load in the span;Under the same concentrated torque load constraint torsion conditions,the stress and maximum torsion angle of the mid span section of the composite box girder are consistent with the theoretical calculation.