A Study On Nonlinear Mechanical Behavior Of Composite Box Girder With Corrugated Steel Webs

Composite box girder with corrugated steel webs has a broad application prospect and has become a hot research topic in bridge engineering field in recent years.The stress of composite box girder bridge with corrugated steel webs is more complicated in comparison with ordinary concrete box girder bridge.Lots of engineers,experts as well as scholars at home and abroad have carried out rich and in-depth theoretical,experimental and engineering research on the shear,bending,shear lag,torsion,distortion and dynamic behavior of composite box girder with corrugated steel webs,and have achieved abundant research results,but relatively few researches have been done on the nonlinear mechanical behavior of composite box girder with corrugated steel webs.In this paper,based on the finite element method and applying the large-scale finite element software Abaqus,the simulation is conducted on the whole process of stress of the composite box girder with corrugated steel webs of variable cross-section.The mechanical response of composite box girder with corrugated steel webs is studied when the nonlinear factors of the structure are considered.Firstly,this paper studies how to use Abaqus for nonlinear analysis.Through comparing the differences between the concrete constitutive model and the concrete damage plasticity model(CDP)in Abaqus in the "Code for Design of Concrete Structures"(GB50010-2010),and modifying the formula of constitutive relation in the "Code for Design of Concrete Structures",a material parameter calculation method suitable for the CDP model in Abaqus is proposed,and the results of the finite element model are compared with the experimental results in the literature,and moreover,the accuracy of the relevant formula is verified.Moreover,the features of implicit algorithm and explicit algorithm are compared from two aspects of the results,namely,the accuracy and computational efficiency.It is shown that the explicit dynamic analysis which is supplied by Abaqus is more advantageous for solving the composite box girder with corrugated steel webs based on CDP model.Secondly,the finite element model of 27.9 m variable cross-section composite box girder with corrugated steel webs of Qianshanhe Specially Long Span Bridge is established by using the verified and feasible modeling process and analysis method,and the effect of nonlinear factors on the mechanical behavior of the variable cross-section composite box girder with corrugated steel webs is studied after conducting the static analysis on structure by applying different load types.The main conclusions are as follows:(1)The longitudinal normal stress of corrugated steel webs is greatly increased by the damage and cracking of concrete.The bending normal stress,which is mainly borne by the roof and the floor,is assumed by the web and the floor together,and the roof loses most of its flexural capacity at the crack site of concrete.(2)The shear force of the variable cross-section box girder bottom plate cannot be ignored.The closer to the support,the greater the shear ratio of the bottom plate,and it even undertakes more than 50% of the shear force of the whole cross-section;(3)Tensile cracking may occur at the thickness change places of the roof due to lateral bending in a certain range near the load action under eccentric loading.In the end,by discussing the main engineering measures for improving the mechanical performance of composite box girder with corrugated steel webs,the influence of lining concrete on the stability of steel webs and the influence of diaphragm plate on the torsional performance of box girder are analyzed.The study results showed that:(1)There was significant influence of setting range of lining concrete on the critical buckling load of corrugated steel webs.Nonetheless,the range of the lining should ensure that the position where the web is most vulnerable to buckling instability is strengthened by the lining,if the initial defect and the plasticity of steel webs are taken into account,otherwise the lining has no obvious effect on the nonlinear stability of corrugated steel webs.(2)The deformation and stress of composite box girder with corrugated steel webs are reduced under torsion after setting the diaphragm plate,and the closer the diaphragm plate to the load position is,the more obvious the anti-torsion effect of the box girder will be.In addition,the transverse bending normal stress of the structure under torsion can be effectively reduced by diaphragm plate.Therefore,the longitudinal tensile cracking of the roof concrete caused by eccentric load can be prevented by setting the diaphragm plate.