Analysis On Shear-lag Effects On Multi-cell Box Girders Of Bending-torsional Coupling

Thin-walled single-box multi-chamber box girder is widely used in bridge construction due to its excellent structural performance and good cross-sectional form,as well as the convenience of modern construction and large traffic flow,especially in the construction of wide deck bridges.Greatly promoted the development of China's transportation industry.However,due to the web,the normal stress distribution of the cross section of the flange and bottom plate of the single-box multi-chamber box beam is different from that of the single-box single-chamber box girder.The problem of lag effects is not properly considered,and the results often endanger the health of the structure and cause serious irreversible consequences.Therefore,this paper analyzes the bending-torsional coupling and the shear lag effects of single-box multi-closed box girder.This paper abandons the assumption of flat section during bending and Courbruna-Harding correction theory for revising longitudinal warping displacements during torsion.A linear interpolation function is used to simulate the longitudinal warping of the box beam section under bending or bending-torsional coupling.The tangential displacement adopts the rigid perimeter assumption.The bending shear stress is considered,the shear lag effect of the box beam under longitudinal bending is analyzed,and the bending shear stress and the restrained torsional warpage shear stress are taken into account.A multi-closed thin-walled box-girder bending-torsional coupling analysis Hamiltonian dual solution system is established,and the system is analyzed based on the precise integration method of the boundary value problem at both ends.Solve the longitudinal displacement and normal stress of the structure under the condition of longitudinal bending or bending-torsional coupling and fully consider the shear lag effect through MATLAB software programming,the change law of shear lag effect with height-span ratio,section size and Poisson's ratio is summarized and analyzed in this thesis,so as to provide a certain design basis for bridge engineering designers.