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I think of it this way: If I took a sheet of aluminum foil and folded it in half making a 17 degree wedge and then subjected that edge to impact with some object, the edge would sustain an amount of damage. If I somehow fashioned that same edge in a sheet of foil but added peaks and valleys (striations), in effect creating an appearance similar to an accordion bellows running perpendicular to the edge, I believe the striations would add rigidity to that edge. Again, I could be completely off base with these thoughts but that's they way I have visualized this for some time.
The only reason that holds for Al foil is because the foil is essentially 2D, and the striations add thickness. I beams are more rigid than thin flat beams, but much less rigid than the thick block that would encompass the I beam.