Abstract: Based on the displacement variational principle, a general semi-discrete method is developed for buclding analysis of thin-walled members with arbitrary cross section under pure compression and pure bending. A transformed B₃ spline function is used to simulate the warping displacements along the cross section of the thin-walled member. By abandoning the assumption of no shear strain along the central line of the cross section the method takes into account the shear lap effect. A large number of numerical examples demonstrate that the present method is accurate, versatile, efficient as well as reliable.