Structural Sections
The symmetry of pipe gives it the same bending strength, in any direction, which makes it an excellent product for the resistance of buckling. The stress required to buckle an axial member decreases with length. The radius of gyration has the opposite effect and increases the ability of a section to resist buckling. The W and HP sections have differnt radii of gyration (rx and ry) for the X and Y axes, while remaining constant for a pipe. The end result is that a pipe can take much higher loads for long, unsupported lengths.