Tall Light Gage Jamb Question
Tall Light Gage Jamb Question
(OP)
I'm designing the light gage steel for an apartment complex renovation. On one floor, the studs span 22'-4" and have a 12' wide window. I am calculating I need (4) 6", 12ga studs with 2 1/2" flanges to make this work. So my jamb ends up being 10" wide. Seems kind of ridiculous and I end up having to worry about torsion etc. due to the window header and sill only framing into one side of the jamb. At what point should the EOR have specified a tube steel jamb for this condition?
I get this all the time and it drive me nuts. It seems it is done out of ignorance for the limitations of light gage steel and the fact that they want to keep their fee low by delegating the designs to the light gage subcontractor.
I get this all the time and it drive me nuts. It seems it is done out of ignorance for the limitations of light gage steel and the fact that they want to keep their fee low by delegating the designs to the light gage subcontractor.






RE: Tall Light Gage Jamb Question
I would stick with your design (don't forget to include the contribution of the nested tracks), and don't worry too much about the torsion--there is sheathing on both faces of the wall, as well as bridging within the wall, to resist the twist.
Also, studs with wider flanges (I think as much as 3.5") are fairly common now--you may want to check into that.
DaveAtkins
RE: Tall Light Gage Jamb Question
Probably, but I have been successful in the past by complaining loudly enough.
I usually do not count the nested tracks unless I really need it due to the fact that they are usually spliced in a jamb of this length. I guess i could specify that they custom order cont. ones.
A piece of HSS6x6x1/4 would work nicely.
The other issue is the use of L/360 for the cladding deflection (composite metal panels). It was originally spec'ed at L/600 and I spoke to the EOR and he changed it to L/360. Seems I should be able to use L/240 for this material.
RE: Tall Light Gage Jamb Question
As EOR's, we struggle with two opposing constraints:
1) Gratuitous use of red iron adds project cost so CFM use should be maximized.
2) Our fees, dictated largely by our competitors, assume that the detailed design of CFM will be delegated.
It's a set up guaranteed to encourage exactly the problem that you've encountered.
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: Tall Light Gage Jamb Question
Exactly and it likely ends up costing the owner more overall or the light gage sub just takes it on the chin. Seems if the EOR included light gage in their fee and subbed it out at least everything could be coordinated prior to the bid set. That way everyone is bidding the same thing and they don't have to excessively pad their bids for engineering or other unknowns that may occur after engineering. Cost saving there for sure overall. Now convince your client of that :>
RE: Tall Light Gage Jamb Question
Part and parcel with the ignorance bit is the fact that most EORs' egos won't allow them to admit to sucking at CFM. It's just sticks, right?
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: Tall Light Gage Jamb Question
Track can be ordered in any reasonable length but is usually stocked in 10' lengths
Most EOR's suck at a lot of things such as Geotechnical engineering but the owner still separately hires a geotech that the EOR coordinates with. I think if EOR's were on the receiving end of what I typically get, they might change.
RE: Tall Light Gage Jamb Question
RE: Tall Light Gage Jamb Question
I think most EOR's don't want to add steel later as it gives the perception that they were negligent.
RE: Tall Light Gage Jamb Question
That would save some width.
RE: Tall Light Gage Jamb Question
RE: Tall Light Gage Jamb Question
I guess the only difference between the jambs and a common stud is that I use a lower wind pressure due to their larger tributary area. Also, I usually do not have to push a common stud to the limit so it generally has more relative stiffness than the jamb. I am going to let the arch worry about water issues.