Research On Shear Lag Effect Of The Composite Box Girder With Corrugated Steel Webs

Since the advent of the composite box girder with corrugated steel webs,this novel composite structure has been widely used in domestic and foreign large span bridge construction,due to its good mechanical performance.However,similar to all ribbed slab structures,there also exists shear lag effect in the composite box girder.In view of this situation,this paper does some research on the shear lag effect of box girder with corrugated steel webs by means of theoretical analysis and finite element numerical simulation.The main contents include:In the first chapter,this paper introduces the history,development,structural style and stress characteristics of box girder with corrugated steel webs and summarizes the research situation about composite box in domestic and foreign.In the second chapter,this paper calculate the longitudinal stiffness ratio of corrugated steel webs and come to a conclusion that when subjected to vertical load the contribution of corrugated steel webs to bending capacity of composite structure can be neglected.Referring to the shear lag analysis theory for general box girder,this paper gives full consideration to the structural characteristics of box girder with corrugated steel webs and selects four parabola as longitudinal displacement functions.Based on the energy-variational method,the paper deduces the formula of the shear lag coefficient and axial stress of any point on the flange.It analyzes the longitudinal and transverse distribution law of shear lag effect about simple supported,cantilever and continuous box girder with corrugated steel webs when subjected to uniform load or concentrated load.The longitudinal law of the additional bending moment and the position of critical point between positive and negative shear lag effect when the cantilever composite box girder is subjected to vertical load are studied.Numerical example is given for verifying the effectiveness and correctness of the algorithm presented in this paper.In the third chapter,in order to analyze the shear lag effect of composite box girder under different lateral loading position,this paper,based on the energy-variational method,by assuming three different longitudinal displacement difference functions for the top,bottom and cantilever plate with the longitudinal displacement adopting four parabolic function to take the influence produced by lateral loading locations on deformation potential energy of the system into account and establishes the governing differential equation of simply supported composite box girder under consideration of lateral load displacement to solve its shear lag effect.By comparing the results obtained from theoretical calculation and ANSYS finite element numerical stimulation to verify the correctness of the method in this paper.The conclusion from the analysis points out that in process of the lateral loading position movingfrom the top of web to the center of roof,the shear lag effect of the roof changing from positive to negative,this phenomenon is particularly prominent when subjected to concentrated loads,But the bottom plate has been kept as the positive shear lag effect.In the fourth chapter,this paper discusses the influence on shear lag effect which produced by the variation of geometric parameters such as width-span ratio,width-height ratio,hanging wing ratio,thickness of flange and the height of the wave.Results show that the influence produced by the width-span ratio is very notable but the influence by other geometric parameters can be ignored.