Study on warping displacement function and generalized internal force in shear lag effect analysis of box girder
Received:October 07, 2011  Revised:March 19, 2012
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DOI:10.7511/jslx20126010
KeyWord:thin-walled box girder  shear lag effect  warping displacement function  generalized internal force  additional deflection
        
AuthorInstitution
张元海 兰州交通大学 土木工程学院,兰州
康喜东 兰州交通大学 土木工程学院,兰州
林丽霞 兰州交通大学 土木工程学院,兰州
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Abstract:
      Based on the flexural theory of thin-walled box girder,the curve of quadratic parabola is proved to be the reasonable form of the warping displacement function in the shear lag effect analysis of a box girder through investigating the in-plane shear deformation and the bending shear flow distribution in the flanges.The additional deflection induced by shear lag effect is adopted as the generalized displacement.The governing differential equations and the corresponding boundary conditions for shear lag effect of box girder are established by the energy calculus of variations based on the principle of minimum potential energy.The new generalized internal force is defined rigorously,and a simple and convenient formula of stress for shear lag warping is presented which has the same form as the bending stress of elementary beam.A simply supported box girder model is analyzed and the calculated results are in good agreement with the test results,validating the method and formula presented.The generalized moment for shear lag differs from the bending moment in distribution and attenuates quickly.For the simply supported box girder example under concentrated load,shear lag effect increases the mid-span deflection by 12%,which should be treated carefully in practice.