Which design resists impact damage better, open or closed roll formed sections?
Closed sections have certain structural advantages, but not in the area of impact resistance. The moment of inertia about the bending axis in a frontal impact situation for a closed section column and an open section column are virtually identical, so their bending resistance levels are equivalent. In fact, if all else is equal, because of the structural advantages of closed sections, a closed section column of a given load-carrying ability will have a thinner wall than will an open column of the same load-carrying ability. This would decrease impact resistance. Only if the capacity of the closed section is greater (or thicker) would a user enjoy any structural advantage in it – but this holds true when comparing almost any two columns. Why don’t we see many manufacturers produce this shape? The problem lies in usability. Attachment of accessories can be difficult with closed sections, because through-bolts would have to be used, and proper tightening without column crushing would be a
