barn loft

[bobwink]

Hello all,

Storage is a mess and I need a loft in the barn. The barn is constructed with 4x4 steel columns (1/4 inch wall). In one direction, the columns are 12 feet on center. In the other - 18 feet. The loft would be 12x18.

I'd like to weld steel beams to the columns in the 12 foot direction and place 16" high trussed joists in the 18 foot direction - 16" on center. The decking would be 1-1/8 plywood. (I already have the joists and plywood from a house project.)

The floor loading would consist of items that I can carry up a ladder, so I'm thinking 40 would do.

My question is:
What size steel beam would be needed? A 4" wide beam would be best as the columns are 4". The only H beam in that size is W4x13. Would that work?

If not, how about a 4x5x1/4 tube? (I have one of these, too.)

Thanks for any help.
bobwink

[Don_P]

If I'm understanding right the steel beam spans 12' and carries half the floor joist spans or 9'. So 12x9 a 50 lbs/square foot (40 live + 10 dead load)= 5400 lbs or 450 lbs/lineal foot of beam.
The AISC manual doesn't have a span table for H shapes that I see, for W shapes a W4x13 is not listed over 10' span. A W5x16 is good for a uniform load of 11,000 lbs in A36 steel.

The I value for a W5x16 is 21.3 in^4 for a 5x4 tube with 1/4" wall its 14.1

I set up this calc with the closest sizes I could find if you want to check it yourself.
http://www.windyhilllogworks.com/Calcs/steelbeamclc.htm This should really be sized by a post frame engineer.

[bobwink]

Thank you, Don for an excellent reply. Your calculator is cool and I learned about "tributary width". Now I'm concerned about the posts! Your suggestion of consulting an engineer is well received.