Single Box Double Chamber Equal-section Corrugated Steel WEB Composite Box Girder Analysis Of Torsional Mechanical Properties

According to the existing research contents and methods of traditional corrugated steel web composite box girders,the torsional performance and vibration characteristics of a new type of corrugated steel web combined box girder with steel bottom plate are investigated in this paper.Based on the second theory of Umansky,the torsional control differential equation of the composite box girder with single box and double chamber corrugated steel webs with steel bottom plate is derived,and the stress distribution of the box girder section is solved by the method of initial parameter solution.The finite element simulation analysis model is established to verify the applicability of the theoretical value,and the results of the finite element simulation analysis model are compared with the experimental results of the traditional single box and double chamber corrugated steel webs box girder and concrete box girder.The influence of geometric parameters on the longitudinal warpage stress of the new composite box girder is analyzed.Finally,by using the second theory of Umansky and dynamic kinematics of box girder,the formula for calculating the natural vibration frequency of restrained torsional vibration of single box and double chamber composite box girder is derived,and the layout of transverse diaphragm which affects the natural vibration frequency is also analyzed.The main conclusions are as follows:1)The restrained torsion effect of single box and double chamber steel web-bottom composite box girder is mainly composed of shear stress and normal stress,and the torsional effect is more obvious than that of traditional corrugated steel web composite box girder.2)Under eccentric load,the torsional and distortion effects of composite box girder are often coupled together and are not easily separated.The twisting and distortion effects of traditional single box and double chamber steel web composite box girder account for 40% of the symmetrical bending effect,while the proportion of the new type box girder reaches 50%,and the coupling effect increases obviously.3)Through the study of the geometric parameters of the bottom plate of box girder in this paper,the thickness of the bottom plate should be set in the range of 25mm~30mm,the height of the longitudinal stiffener should be 200 mm,and the thickness of the stiffener should be about 14 mm.The arrangement spacing of the stiffened ribs in the transverse direction of the bridge is 0.75m~1.00 m,and 2~4 channels are arranged in each box room,which can make the optimum size ratio of the bottom plate.4)The torsional vibration performance of the composite box girder can be improved by setting the transverse diaphragm in the span of the composite box girder,and the basic frequency of the single box and double chamber composite box girder is not affected by the installation of the transverse diaphragm at the two ends of the beam.It is more beneficial to improve the torsional vibration performance of the composite box girder by setting the transverse diaphragm in the middle span area.Therefore,the transverse division plate in the middle span area should be more dense,the two ends should be loosely arranged.Based on the existing research results of traditional corrugated steel web composite box girder,this paper puts forward the equivalent simplification of the new type of bottom plate for the new waveform steel web composite box girder.At the same time,a new method to optimize the parameters of the floor plate by using the finite element simulation analysis is put forward,and a new train of thought is put forward to compare the calculation results of the new structure theory with the results of similar structural tests,and then prove the applicability of the theoretical results.It is hoped that it can be used as a reference for engineering researchers.