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Steel joist economics when no two are identical
2

Steel joist economics when no two are identical

Steel joist economics when no two are identical

(OP)
I've got a building that I need to roof that looks like this:

1) 80' in length
2) 40' in width at one end and 25' in width at the other (trapezoid).

Because of the spans, and conventional economic wisdom, we're wanting to use open webbed steel joists. There is some concern, however, that the joists might be unduly expensive because no two will be the same length. I'm interested to hear comments speaking to that. Some things that I've considered:

1) I could get the job done with some large W-beams with the overall steel weight being much greater than the OWSJ.

2) With modern fabrication and jigging procedures, perhaps it's not such a big deal. In my wood truss days, we'd make a common jig and make 80% of the webbing identical from truss to truss to allow for continuous chases. Not so bad.

3) I've got a 60' x 60' gymnasium on the same property that will have some nice, repeating OWSJ. So it's not as though the oddballs would make up the only steel joists in the contract.

I'm leaning pretty strongly towards OWSJ. I'll be contacting local OWSJ suppliers for their advice as well. I find suppliers to often be overly optimistic about the range of applicability of their products however.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Steel joist economics when no two are identical

2
With the degree of automation by plants like Canam or Nucor I doubt you will see a difference if all the joists are the same or not. Many times what we think is the same joist is not in their world due to spacings, load requirements, bracing, or end bearing details. It is all about the pounds of steel in their world. Many times we send preliminary designs to the Canam guy we deal with and they send us a quote. They never charge us for that and we always make sure to forward the information to the GC's.

The SS option will be far more expensive due to the pounds of steel.

RE: Steel joist economics when no two are identical

Have you considered a Girder at the halfway point of the 80' length?

RE: Steel joist economics when no two are identical

(OP)

Quote (EZ)

Have you considered a Girder at the halfway point of the 80' length?

I hadn't. It's a clever idea though that I'll consider.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Steel joist economics when no two are identical

I would use 40 foot long joists at 5 or 6 foot spacing with a WF beam or joist girder (at midpoint of the 80 foot length of building) spanning 32.5 feet.

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