Elastic buckling of web restrained by flanges in I-section members

Elastic buckling of web plates in I-sections under linearly distributed stresses and shear stresses was investigated using finite element method (FEM). A brief review on various formulas for the buckling coefficients of simply supported plates from different codes was presented firstly. Then the formulas for the plates with two unloaded edges fixed were proposed by changing the boundary conditions of two unloaded edges. The difference between the restraint by the flanges and the traditional rotational restraint was pointed out. A simple and accurate formula for the buckling coefficients of the Web plates restrained by flanges was presented using the ratio of flange's free torsional stiffness to the bending stiffness of the Web as a parameter representing the restraint. A series of finite element analyses of Web plates subjected to combined bending and shear stresses were carried out to validate the applicability of the traditional interaction formula for the buckling of plates under bending and shear.