JasonPAtkins
Hot Rolled
- Joined
- Sep 30, 2010
- Location
- Guinea-Bissau, West Africa
I have a question. It's probably better suited to WeldingWeb, but in general I think PM answers have more informed math, lol.
About once a year, someone asks my fab students to do a roof. Sometimes it's over a simple school building, sometimes a simple one-story house.
In the past, I've enlisted the help of a volunteer engineer from the States to help me come up with proper truss sizing and spacing.
The roofs we're talking about are custom welded metal trusses (involving some combination of angle and i-beam), then set in place and purlins (usually rectangular tube) welded across them. I'm carefully overseeing the student welding, as obviously something that could fall and kill someone needs to be done right. Lots of work we do here is seat-of-the-pants engineering, but we like to stay away from that for roofs.
Unfortunately, that engineer isn't available to help me anymore, and I have a new project, which is the biggest span we've been asked to do.
This leads me to my question. For manufactured wood trusses like we're used to in the States, the manufacturers obviously provide loading info, and spacing requirements from one truss to the next. Has anyone ever seen such a table for steel trusses? What I was doing with the engineer on previous projects was essentially reinventing the wheel every time, and I have to imagine that after a hundred years of building buildings out of metal, someone has already run these numbers and published them somewhere.
The information I'm looking for would be like: For a standard double cantilever truss where the top and bottom cords are a pair of 2x1/4" angle, with 1.5"x3/16" crosses, you can support X psf of load if spaced every 2', Y psf of load if spaced every 3', Z pfs of load if spaced every 4', etc.
It would be great to have a chart to be able to look that information up, which would let me design a simple roof, but the design be backed by solid engineering. That's the general case.
Specifically for this case, if anyone knows of an engineering firm that would be interested in donating time to help build a training center in West Africa, put me in touch with them, please! In this case, I came late to the party, after the spans and spacing of the reinforced concrete columns had already been formed, so the spacing is (to my uneducated eye) wider than I would have liked, requiring a really heavy truss. That, combined with the spotty supply of strong steel here, adds to a fun little predicament.
About once a year, someone asks my fab students to do a roof. Sometimes it's over a simple school building, sometimes a simple one-story house.
In the past, I've enlisted the help of a volunteer engineer from the States to help me come up with proper truss sizing and spacing.
The roofs we're talking about are custom welded metal trusses (involving some combination of angle and i-beam), then set in place and purlins (usually rectangular tube) welded across them. I'm carefully overseeing the student welding, as obviously something that could fall and kill someone needs to be done right. Lots of work we do here is seat-of-the-pants engineering, but we like to stay away from that for roofs.
Unfortunately, that engineer isn't available to help me anymore, and I have a new project, which is the biggest span we've been asked to do.
This leads me to my question. For manufactured wood trusses like we're used to in the States, the manufacturers obviously provide loading info, and spacing requirements from one truss to the next. Has anyone ever seen such a table for steel trusses? What I was doing with the engineer on previous projects was essentially reinventing the wheel every time, and I have to imagine that after a hundred years of building buildings out of metal, someone has already run these numbers and published them somewhere.
The information I'm looking for would be like: For a standard double cantilever truss where the top and bottom cords are a pair of 2x1/4" angle, with 1.5"x3/16" crosses, you can support X psf of load if spaced every 2', Y psf of load if spaced every 3', Z pfs of load if spaced every 4', etc.
It would be great to have a chart to be able to look that information up, which would let me design a simple roof, but the design be backed by solid engineering. That's the general case.
Specifically for this case, if anyone knows of an engineering firm that would be interested in donating time to help build a training center in West Africa, put me in touch with them, please! In this case, I came late to the party, after the spans and spacing of the reinforced concrete columns had already been formed, so the spacing is (to my uneducated eye) wider than I would have liked, requiring a really heavy truss. That, combined with the spotty supply of strong steel here, adds to a fun little predicament.