? for all of you structural engineers

[tinkerer]

Hello everyone. I have a "structural engineering" question I'm having trouble answering myself. I have a slant wall building that I'm building a "hood" or "overhang", that extends the roofline out past the bottom of the wall.  On one end of this overhang, there is a door. It is 22 ft wide. I have vertical supports that extend from the gound up to "I guess they would be called joists". These vertical supports are 6 inches past the ende of the door frame on each side of the door. I am then laying "stringers" across these joists to attach the roof tin too. Now for my question... What kind, shape, size, etc piece of steel do I use to span 23 feet that will support the tin and I suppose a little snow load, and not buckle or sag in the middle?? Keep in mind that this "stringer can only be 4 inches in width from the bottom surface of the tin downward to keep my door height. "I'm losing a little door height as it is to get my desired slope."
Let me know what you think!

Thanks!
Ben

[fabricator]

4" from the top surface down would be height, you are gonna be hard pressed to find something 4" thick and 23' long that won't sag, something like 4 x 4 square tube with a 1/2" wall might do it.

[mbryner]

Sketch?

[rcavictim]

4"x4"x5/16" steel box tubing ought to do it. Maybe even 1/4" wall. I work a lot with 1/8" wall, 4-1/2 inch steel irrigation pipe in 21 foot lengths.  I can stand on a span and jump my 230 lbs up and down in the middle and it doesn't wince.

[JLMTECH]

HI Tinkerer,

Your door project is interesting.

Consider supporting the loads on the 23 foot opening with a bar joist
that is placed above the roof tin. The tin would be screwed to the bottom
of the bar joist. A protective coating would be needed on the bar joist.
Surplus bar joists are fairly common.

If you give the length of the stringers to determine the load on the bar joist,
I can tell you witch bar joists will work. The answer would be a minimum height
and minimum weight. Any bar joist bigger and heaver would work.

Also you might need to beef up the support for the stringers at the slant wall. It is
unusual for this type of structure to have extra structural capacity.

Your humble structural engineer.
         

[Lloyd]

You could also install the door to a curtain wall, this would provide what ever room you need as well as adding shear strength.

Lloyd