They (the people wanting to know if they can use the red iron beams pictured) would have to have some idea of what they want to build, how they want to use those beams whether it be vertically or horizontally, and what that weighs. Pound per foot weights can be found online for all structural steel. Add those up, piece by piece, and whether it be a carport type cover, or a simple weather shed, the overall weight of the structure can be determined. Safety factors such as square feet of surface supporting X feet of wet snow, plus six grandkids on one porch swing, and 37 one gallon hanging flowerpots, and 12 ceiling fans, should also be factored in. That’s where structural engineers come in.
If it wobbles a little bit during a hard rain, chances are you shouldn’t use it to pull the motor and tranny out of your Jeep.