Originally Posted by MichaelW
It sounds counter-intuitive to remove metal, yet increase strength, but structures usually fail at the joins, and butted profile tubing helps to distribute stress away from the joins.
well, in members, there is a part where there is a stress concentration on a specific area, which means the area where this occurs will stressed more which makes it vulnerable to fracture.. This usually occurs at the joints. Removing material from the center actually decreases the stress concentration factor in the joints, which means a relatively stronger frame.