Analysis On Shear Lag Effect Of Simply Supported Box Girder With Corrugated Steel Webs Of Variable Width Section

A new type of composite box girder with corrugated steel webs has been used in practical projects.The composite box girder has light weight and superior structural performance.In this paper,the Mechanical Properties of the simply supported box girder with corrugated steel webs with variable width section in the four-box section of the Steel Lanzhou Zhongchuan International Airport are studied.mainly including:(1)This paper introduces the development history,research status and application of the box girder bridge with corrugated steel webs at home and abroad,expounds the structural requirements and stress characteristics of the improved box girder,and introduces the research methods of the shear lag problem of the box girder.The main contents of this paper are also introduced.(2)Using the energy variational method to solve the corrugated steel web composite box girder shear lag problem,choose quadratic parabola as the warping displacement function.The calculation formul as of normal stress,vertical displacement and shear lag coefficients of roof and floor of he simply supported box girder under concentrated load and uniformly distributed load are derived.The results are verified by numerical examples: under concentrated load,the maximum shear lag coefficient of the roof reaches 1.253,and the maximum shear lag coefficient of the floor is 1.182;under uniformly distributed load,the maximum shear lag coefficient of roof reaches 1.022,and the maximum shear lag coefficient of floor is 1.033.The results show that normal stress is unevenly distributed along the transverse bridge direction of the box girder,and the shear lag effect is obvious in the web.However,the shear lag effect of the box girder under uniformly load is obviously lower than that under concentrated load.(3)The ANSYS solid finite element model of 30 m span widened box girder was established.And the stress and deflection of the key section under concentrated and uniform load are calculated by finite element method,and the results were compared with theoretical values.The results show that normal stress is unevenly distributed along the transverse bridge direction of the box girder,and the shear lag effect is obvious at the web.The Shear lag effect of box girder under concentrated load is larger than that under uniform load,and the finite element value agrees with that of energy variational method.The reliability of the finite element model is verified.(4)The finite element models of A,B and C of four-box single-cell corrugated steel webs with equal width and variable width are established to impose a certain load on the box girder.The reaction force of each box girder,vertical displacement of Longitudinal Bridge,stress of box girder and shear force of web are extracted respectively.The results show thatunder the same load condition,the reaction force,vertical displacement,stress and shear force at the web of the box girder with the same width and with the same width are basically the same,but there are some differences in the distribution of web shear force.(5)The influences of different width-span ratio,thickness of top plate,height of corrugated steel web and Shear lag effect of box girder with cantilever ratio are discussed.The results show that except the width-span ratio has a great influence on the shear lag effect,the other geometric parameters have little influence on the shear lag effect.