Growing up, my Dad had sitting on his office desk a little device called Newton’s Cradle. It had 5 suspended steel balls hung from a frame. You raised one of the end balls, let it go and when it hit the others, the one on the opposite end would fly up. This device represents Kinetic Energy. I didn’t understand it at the time but for a kid, it was fun to play with!
Now, using that same principal, think about one’s head leaning up against the exterior wall of a concrete or masonry tornado shelter. On the opposite side of the wall, a 15 pound 2×4 traveling at 100 mph strikes right where one’s head is against the wall. Get the picture?
Along those same lines, the ICC-500 states that a maximum of 3” of permanent deformation of an interior surface is allowed. 3”! So, you are sitting in one of these steel shelters where the only thing between you and the tornado debris is a sheet of steel that can deflect up to 3” and the shelter manufacturer has so conveniently put a built-in bench for you, on the exterior wall of the shelter with the interior surface of the shelter as you back rest. A backrest that can have a permanent deformation of 3”! How do you think one’s skull, spine, and/or shoulder blades are going to react to that potential 3” deformation?
The long and short of this is regardless of the shelter or the shelter material, during a tornadic event, shelter occupants should stay at least 3” away from the exterior walls of the shelter.
Be careful out there!