Research On The Mechanism Of Bending And Torsion Of Composite Girders With Corrugated Steel Webs

Compared with the traditional prestressed box girder with concrete webs,the prestressed composite girder with corrugated steel webs has the advantages of small dead load,high prestressing efficiency,high shear strength and convenient construction,etc.,and it has been widely used in practical engineering.This paper is based on the project of the National Natural Science Foundation of China: Research on the project of the Natural Science Foundation of Hebei Province: Research on the Mechanism of Bending and Torsion of Prestressed Concrete Composite Beams with Corrugated Steel Webs(E2018210149).The mechanism of bending and torsion of composite beams with corrugated steel webs is studied and analyzed from three aspects of experimental research,finite element analysis and theoretical derivation.The work done and the main conclusions are as follows:(1)The properties of bending and torsion of composite beams with corrugated steel webs were studied experimentally.Different ratios of loads of bending and torsion were applied to three beams with identical parameters,and the test beam under each condition is loaded to failure.The experimental results show that: The larger the torsion-bending moment ratio is,the smaller the cracking load and ultimate load are.With the increase of torsion-bending moment ratio,the failure characteristics of the test beam also change.When the torsion-bending moment ratio is relatively small,the failure characteristic of the test beam is that the steel bars in the tensile zone yield a large area and some of them enter the hardening stage.The concrete in the compression zone reached its ultimate compressive strain and was crushed.The cracks in the bottom plate of the beam body are approximately perpendicular to the beam axis,and there are few oblique cracks.Obvious bending deformation occurred in the test beam.When the torsion-bending moment ratio is large,the failure characteristic of the test beam is that the main tensile crack of concrete slab is too large and shear failure occurs,and the torsional deformation of the beam body is obvious.Under the action of bending and torsion,the angle between the oblique crack in the pure bending section of the floor and the beam axis is between 45° and 90°.The angle between the oblique crack and the beam axis decreases with the increase of the torsion-bending moment ratio.(2)The finite element model of composite beam with corrugated steel webs is established and the nonlinear analysis is carried out.By comparing the finite element results with the experimental data,it is found that the two values are close.Based on the finite element model,the ultimate load under different torsion-bending moment ratios is obtained by adding different working conditions.(3)The mechanism of bending and torsion of composite beams with corrugated steel webs is theoretically deduced.The bending effect,torsion effect and distortion effect of composite beams with corrugated steel webs under bending and torsion were solved by the elementary beam theory,the Utterson’s second theory and the elastic foundation beam method respectively.The theoretical cracking load of composite beams with corrugated steel webs under bending and torsion was deduced by superposition of the calculated stresses respectively,and the results were compared with the experimental and finite element values.Parametric analysis shows that the bending-torsion stiffness ratio has the greatest influence on the cracking load.According to the finite element model,the ultimate load is extracted by adding different torsion-bending moment ratios.The relation curve between the ultimate bending moment and the ultimate torsional moment is obtained,and the correlation equation between the ultimate torsional moment and the ultimate bending moment is given.It is concluded that when the torsion-bending moment ratio is between 0.15 and 0.6,the torsional moment has the most obvious weakening effect on the bending strength and the bending moment has the most obvious weakening effect on the torsional strength.