Most Ecnomical Grid-Steel Layout

[kaisersoze]

From your expereince, what is the most comman and ecnomical grid layout using steel (beam, columns, joists). I was thinking 24'x24' or 30'x25'.

I know its a silly question, but would still want expereinced folks to share their thoughts.

Thanks,

Kaiser

 

[racookpe1978]

What are you supporting? What application? What loads? (Uniform? Point loads? Dynamic loads? Cars and parking-lot type structure? A simple roof only with live loads from wind and weather and no equipment?)

 

[kaisersoze]

3 story library structure. No point loads, ignore any MEP loads, the floor is probably going to be composite conc and roof to be mtl deck on bar joists. Steel columns, steel girders and shallow footings.


Kaiser

 

[JAE]

You can ask AISC to actually do this for you - they have a preliminary framing service.

Or you can just play around with various sizes and see for yourself.

I think it does depend a lot on the type of loading and also the variations between local labor vs. material costs.

 

[MiketheEngineer]

For typical commercial applications something in the 20x20 to 30x30 and even up to 40x40 range seems to be used quite often.

But then - there are a thousand variations off that for particular reasons - mostly loads, material availability, construction constraints, etc, etc

 

[spats]

I like to limit my composite girder spans to 25', but definitely no more than 30' under normal circumstances. The span on the filler/secondary beams can be a little longer, but generally not more than 35'. I did an office floor once with 35' filler beams, and there were complaints about floor vibration. You definitely need to check floor vibration, although a library would generally have all those bookcases, which would greatly dampen the vibration.

I would consider 25'x25' bays at the floors, and maybe 50'x50' bays at the roof, using joists and joist girders. I wouldn't go 50'x50' if your snow load is greater than 20 psf or so.

 

[msquared48]

You might consider a checkerboard pattern to the framing too, altgernating joist directions every other bay so the supporting Wide flange shapes see half the load - twice the members, but could save steel too. Have seen this in the past work.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[STRE]

Here is sample layout with steel usage for library stackroom application.

lightweight concrete do come with finishing premium and is not preferred around our location. The example assumes normal weight concrete 3.5" on top of 3" composite deck flutes (total 6.5" slab thickness). This configuration generally will afford 1 hour fire rating and with the help of sprinkler, you may be able to get 2 hr. rating preferred for library.

25x25: 4.40 psf steel (filler beam+girder), 28" structural depth
30x25: 4.71 psf steel, 31" structural depth
30x30: 5.57 psf steel, 31" structural depth

Any increase on the structural depth of the floor is translated into the cost for perimeter wall, so limiting structural depth may be another way to minimizing cost.