Elastic buckling load of continuous braced h-shaped beams with fork restraint

In Japan, most of H-shaped beams are rigidly connected to the box sectional columns which have high torsional rigidity, and the boundary condition is corresponding to warping fixed support. Our previous papers clarified that the lateral buckling load of beams with the warping restraint becomes higher than that with pinned support. Furthermore, it was shown that the continuous braces such as roof purlins or concrete slabs connected to the beams also prevent the lateral buckling deformation. This paper evaluates the restraint effect of continuous braces on the lateral buckling load for H-shaped beams with fork restraint under the uniform flexural moment. The lateral buckling load of beams with warping and fully fixed supports is estimated by formulating energy conservation equations. Next, this paper derives the equations of elastic lateral buckling load of beams with fork restraint, which is corresponding to the rotational restraint between warping and fully fixed supports by torsional resistance of column. By comparing the equations with the numerical analyses results, the restraint effect of the continuous braces and column on the lateral buckling is verified. It is shown that the lateral buckling stress becomes higher, as the rigidity of the continuous braces or fork restraint increases.