Variational Method of Shear Lag Effect of Box Beams with Adding Generalized Displacement Assumptions

Abstract:

The top plate and bottom plate of box beams behave different shear lag effects when the symmetric load moves along the cross section.The web shear’s work on the shearing deformation is taken.Based on the previous research and conclusion on the shear lag effect experiment,cubic parabola displacement function is adopted.Considering the top and bottom plate’s different longitudinal displacements,four independent generalized displacements are taken to analysis the shear lag of box beams.Based on the principle of minimum potential energy,displacement differential equations and natural boundary conditions are formed respectively.Formula derivation process shows that shear lag effect and web shear deformation work independently.The computation results indicate that the derivation formulas can improve calculation accuracy.

Key words:box beams; variational method; shear deformation; shear lag effect; generalized displacements