Super Long Span (Steel Trusses)
Super Long Span (Steel Trusses)
(OP)
I am currently involved in a job that requires a 250' clear span for the roof. I have looked into the possiblity of using steel joists. I am waiting to hear back from a couple joist engineers.
The roof is about 32' to the eave and has a 6 on 12 slope. It is also a open structure. It is a big horse show arena. The location is south florida so earth quake is not an issue.
The architech wants a sloped soffit as well so the joist or trusses will have to be scissor type. i can go about 20' deep at the center.
my question is would steel trusses possibly be more econmical than joists?
what would be a good spacing for the trusses, i was assuming about 30' c/c?
What would be the best type of section for the truss parts (Wide flange, Tees, HSS)?
How much will thermal be an issue?
Any guidance would be a great help
The roof is about 32' to the eave and has a 6 on 12 slope. It is also a open structure. It is a big horse show arena. The location is south florida so earth quake is not an issue.
The architech wants a sloped soffit as well so the joist or trusses will have to be scissor type. i can go about 20' deep at the center.
my question is would steel trusses possibly be more econmical than joists?
what would be a good spacing for the trusses, i was assuming about 30' c/c?
What would be the best type of section for the truss parts (Wide flange, Tees, HSS)?
How much will thermal be an issue?
Any guidance would be a great help






RE: Super Long Span (Steel Trusses)
Sounds to me like you will be using fabricated main trusses with joists spanning between them.
Good Luck!
RE: Super Long Span (Steel Trusses)
What about a metal building? With this type of system you would have massive foundations.
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
I did not see your questions at the bottom of your email:
Steel joists are always cheaper than fabricated steel trusses
25 foot to 30 foot spacing
Keep truss connections as simple as possible, therefore, use angles first, tees second, WF next and tubes last unless there is some architectural consideration
Thermal should be investigated especially if the building has minimal insulation, ventilation or A/C.
RE: Super Long Span (Steel Trusses)
Thanks for the help
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
Why not dust off your old design book and design them yourselves? It's really not that hard. With trusses this deep, the members are not going to be very heavy. You can space them at twenty feet or so, put in light purlins and do a pretty economical design. Note that you can vary the chord and diagonal sizes to optimize the design.
This sounds like a once in a lifetime chance. Why not take the design and do it yourself? It's much more satisfying than writing a specification. And it doesn't cost that much more.
RE: Super Long Span (Steel Trusses)
But does anyone have an idea as to how I can detail the end truss connection to allow about 4" of movement in the horizontal.
I tried to restrain the truss at both ends but the force gets to be about 350 kips, and that is crazy.
If I go with pin and roller I get 4" of horizontal deflection but only a 30 kip reaction (which is doable). If anyone has any ideas it would be a great help
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
RE: Super Long Span (Steel Trusses)
A disadvantage of having these done by a joist supplier is that you don't really know where the conservatism is in their design. When Joe (or Jane) mechanic wants to hang a 500 lb widget from the joist, you're going to have a tough time saying yes or no. The joist supplier calculations are very tough to fight through, if you can at all.