I need to come up with a beam (two of them, actually) that will hold a large steel box suspended over a hole in which it will ultimately be buried. The box is 9 feet long by 5'6" wide and weighs 1600 pounds. The box will not rest across the length of the beam, it has to rest on two supports on either side. The hole will be just over 6 feet wide, so my beams will rest on the edge of the hole, and the box on the supports on the beam. A rough diagram: ==|=====||=================||====|== Beam Hole Support Support Hole edge edge The hole will be 73 inches wide, the bar 85 inches, and the support rails 18 inches inside the edge of the hole. I added 25% to the weight of the box for safety and I think 2-inch square tubing with 1/8 inch walls will work - I found formulas to calculate the stress on the beam in this scenario and then some more to calculate the stuff the formulas need: section modulus came out to 0.5517, weight on the support 500 lbs (2000 / 4 supports), so a bar that long with the stress 18" from the end should be feeling 16,311 lbs/sq. inch. (right? I assumed the part of the bar outside the hole would not factor into the calculation...) The challenge I had was finding out the yield strength (I hope that's correct - I'm looking for how much stress it can take without being ruined) of that material...came up with nothing beyond a vague post that 36000 psi is as far as you want to go for 'steel'. So, it looks like my 2" tube will work, but I'm not an engineer and am skeptical of both my calculations and the information I found. So I'm asking professionals...what do you think?