| The composite box girder with corrugated steel web has been rapidly developed and applied in bridge construction due to its advantages of light weight,reasonable force,good durability,fast construction speed and beautiful shape.Domestic and foreign scholars have done a lot of research on their mechanical properties,but some problems still need further research.This paper relies on the National Natural Science Foundation-Mechanical performance analysis and experimental study of large-span prestressed concrete composite box girder with corrugate steel webs(51368032),relevant theoretical and experimental research on the flexural mechanical properties of composite box girder with corrugated steel web is carried out.The main contents and results are as follows:(1)Starting from the basic assumption of the composite box girder with corrugated steel web,the vertical displacement of each wall of the composite box girder is the same as the basic conditions.The deflection displacement function of the composite box girder under different conditions such as the shear deformation of the corrugated steel web,the vertical shear deformation of the concrete flange and the shear lag effect of the concrete flange are derived.The energy variational method is used to establish the differential equations of deflection control under different displacement functions and the corresponding boundary conditions,the internal forces are analyzed.The linear independent displacement function is used to calculate the difference,and the element stiffness matrix and the corresponding load array corresponding to different displacement functions are derived.The numerical solution method of combined box girder considering different shearing factors is given,and the corresponding beam segment analysis program was compiled.The research shows that the shear deformation of concrete flanges and steel webs has a greater effect on the deflection of composite box girder,and the influence of the shear deformation of the steel webs on the deflection is greater than the in-plane shear of the concrete flanges.The vertical shear deformation of the concrete flanges has a small effect on the deflection of the corrugated steel web composite box girder,which can be ignored.(2)Tthe additional deflection deformation caused by the shear deformation of corrugated steel web and the shear lag effect of concrete flange are selected separately as independent displacement states.The corresponding deflection control differential equation is established and solved.The method for analyzing the deflection of composite box girder is simplified.The simplified method can clearly reflect the degree of influence of the shear deformation of the steel web and the shear lag effect of the concrete wing on the deflection of the composite box girder,and the calculation expression can correspond to the analysis theory of simple structural mechanics and material mechanics,which is convenient for engineer application.Based on the control differential equations and corresponding boundary conditions of the additional deflection of the composite box girder with corrugated steel web,the beam stiffness element matrix and load array of the additional flexural deformation of the composite box girder are derived,the corresponding beam segment analysis program was compiled.The research shows that for the concrete slabs with variable thickness,when calculating the section parameters,the centroids of the upper and lower wings should be taken as the center of the wing analysis.The stress and deflection increase factor caused by the shear deformation of corrugated steel web is much larger than the shear lag effect of concrete wing,and the stress increase coefficient caused by shear lag is greater than the deflection increase coefficient.(3)Based on the derivation of the flexural displacement function of the composite box girder considering the shear deformation of each plate,combined with the Hamilton principle,the differential equation of the deflection self-vibration frequency of the simply supported composite box girder considering the influence of shear deformation is derived.The analysis process is simplified by assuming a reasonable deflection displacement function that satisfies the boundary conditions.Compared with the deflection self-vibration frequency expression of the simply supported beam of ordinary section in structural dynamics,only one correction factor needs to be added to solve the deflection natural frequency of the composite box girder with corrugated steel web.Based on the expression of the self-vibration frequency of simply supported composite box girder and the three-moment equation,a method for solving the self-vibration frequency of continuous composite box girder is proposed.According to the unit stiffness matrix and mass matrix of the composite box girder section,the corresponding beam segment analysis computer program is compiled.The research shows that the natural vibration frequency calculated by considering the shear deformation of corrugated steel web and the shear lag effect of concrete wing is different from the natural vibration frequency calculated based on the assumption of “planar cross-section assumption”.The natural vibration frequency is too large.The influence of shearing effect of corrugated steel web on the natural frequency of deflection of composite box girder will increase with the increase of natural frequency frequency order,and decrease with the increase of span-height ratio;The shear deformation of the concrete wing has little effect on the natural vibration characteristics of the composite box girder which can be negligible.(4)The two-span cross-section model beam of corrugated steel web composite box girder with a span of 3+3m was designed and fabricated.The strain and deflection of the model beam under load are tested.The natural vibration frequency is collected and analyzed,The test results are compared with the results of ANSYS finite element calculation and the calculation results of method in this paper.The model test results show that the model beam is in the elastic stress stage during the static load test.Both the mid-section and the inner fulcrum section of the model beam show obvious shear lag.The shear lag effect of the concrete wing and the shear deformation of the steel web can not be ignored..(5)In order to more accurately analyze the dynamic response of corrugated steel web composite box girder under live load,the difference between the natural vibration frequency and the power impact coefficient of the composite box girder and concrete box girder is compared and analyzed,the dynamic impact coefficient of composite box girder calculated according to different specifications is analyzed.Based on the theory of vehicle-bridge coupled vibration,the refined finite element model of vehicle-bridge coupled vibration analysis for the composite box girder is established.The refined dynamic response analysis of composite box girder with corrugated steel web and traditional concrete box girder with 30 m single box single chamber and 50 m single box multi-chamber was carried out.The research shows that the natural vibration frequency of the composite box girder with corrugated steel web is lower than that of the corresponding concrete box girder;when the bridge deck condition is poor,the dynamic impact coefficient of the composite box girder is much larger than that of the concrete box girder.The condition of the bridge deck has the most obvious influence on the dynamic response;the local characteristics of the strain dynamic shock coefficient are relatively obvious;the difference of the vehicle and the change of the speed have an influence on the dynamic impact coefficient of the combined box girder. |
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