Cold Form Steel Roof Joist To Wall Stud Connection???
Cold Form Steel Roof Joist To Wall Stud Connection???
(OP)
I am designing a light gauge steel building. I proposed the below connection to client between roof joist to wall stud however outside wall is going up to parapet level as shown.
So I am confused about the strength of this connection does this scheme will work or not under the 6 KN load (joist is simply supported and carrying the UDL load). i am worried about the bottom flange bending of U profile (how I can check) and screw pullout strength.
Please advise how I can make this connection better and what check do I need to analyze.
So I am confused about the strength of this connection does this scheme will work or not under the 6 KN load (joist is simply supported and carrying the UDL load). i am worried about the bottom flange bending of U profile (how I can check) and screw pullout strength.
Please advise how I can make this connection better and what check do I need to analyze.






RE: Cold Form Steel Roof Joist To Wall Stud Connection???
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: Cold Form Steel Roof Joist To Wall Stud Connection???
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RE: Cold Form Steel Roof Joist To Wall Stud Connection???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
DaveAtkins
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
You might then need to add a small edge angle along the stud-joist interface to help support the floor sheathing/decking/diaphragm.
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RE: Cold Form Steel Roof Joist To Wall Stud Connection???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
As for stud bracing since it is an axial loaded wall and one subjected to wind loads I would make sure both flanges of the studs are braced with blocking or sheathing. I would not rely on the gyp board sheathing for this.
John Southard, M.S., P.E.
https://www.pdhlibrary.com/
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
unfortunately wall studs and joist have already produced, so i cannot connect directly roof joist to stud's web (due to shorter length of joist) as you suggested.
the purpose of using the rim track is to increase the thickness at connection point because my wall stud thickness is just 0.95mm which is not sufficient i think , and rim track will also helpful to control the rotation of roof joist as you can see above i am stitching the roof joist from top and bottom side to the rim track flanges.
I used the Dietrich steel joist design guide tables (page 2.9) to determine the thickness,size of angle and no of screws so i found 1.5mm x 40mm x 40mm angle with 4+4 gauge 10 screws for 6 KN force but these table is only covers the shear force but what about the pullout strength due to tension force in above screws do i need to check the pullout strength of screw with respect to the stud/rim track thickness ???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
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: Cold Form Steel Roof Joist To Wall Stud Connection???
1. I agree with Dave, JAE and others who noted that the joists should be attached to the web of the studs instead of the flange.
2. ....this is not true. It doesn't do this. You still have the screw load going through only one thickness of the flange in the line of action of the shear load. You would need a backing strip on the back of the flange to accomplish what you thought was happening. Using the rim track divides the load (potentially); however, does nothing to increase the flange thickness of the studs.
3. I'm not a fan of light gage framing for low slope roofs, particularly with a parapet. The long term serviceability of the structural framing system can be seriously compromised by water intrusion at the parapet, the roof and the interface between the two. Further, depending on the roof drainage design you might have a water load at the parapet-to-roof interface that's greater than any other location on the roof. If you are in a snow load area....even worse! This will significantly increase the shear load on your fasteners. You should add a qualifying statement to your drawings that makes sure the roofing/waterproofing are given critical review for this application.
4. You have a redundant call-out for your screws. A #10 screw is not 10 gauge. Don't confuse the issue with additional information that is not relevant. Also, a #10 screw is fairly small.
5. The wind load on the parapet will put your screws in tension as well as having a vertical shear load from the roof loading. These fasteners are much better in shear only, which is what you would have for both loadings if you had the joist extending through the wall section.
6. Light gage members are cheap. Even though the joists might have been cut already, change them! That's a lot cheaper than a failure!
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
Ron:
In different parts of the world screw nomenclature gets 'screwed' up. For example, in Australia (Metric country, with some hang-ups with non-metric hardware) "10-16" is referred to as a "10 gauge screw" (with 16 threads per inch). Granted this is NOT the same as a #10 screw (a North American term?), but the OP did not state that, and given that the drawing is detailed in metric units, I think the call out is correct.
Now, if the world was rid of 'gauge' and it was universally metric it would be a better place and we would not be having this conversation
For example: Link
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
Strange how the screws get larger as the "gauge" goes up, but for most other "gauge" designations, the smaller gauge number results in a thicker material (wire gauge, sheet metal gauge, etc.).
Yes...let's dump the "gauge" and use thicknesses and diameters.
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
Absolutely agree.
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
i am using buildex screws which have some resistance against pull out force with respect to the materiel thickness. total 4 screws are enough in my case for each studs against pull out force according to my calculation ( 0.682 KN/Screw pull out strength total force 2.2 KN/stud.
i am slightly changing the connection detail i am providing 2 horizontal members in wall @ top and bottom level of rim track as shown below which can provide more space for screws.
for this structure we are using the rain screen cladding system (outer face of the wall) which mean cladding material will not directly attached with studs , there will be steel omega profile between the wall stud and cement board
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
wall will be braced by 1mm thick double strap (cross bracing)
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
How tall is your parapet?
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
Vertical Pressure is 1 Kn/m^2
Strap bracing will be in 2 parts one will be start from top of parapet to first floor level and 2nd will be start first floor level to foundation level so both story bracing is attached with each other through hold down brackets at first floor level. First floor wall bottom track is directly on ground floor wall top track (in between both track there is 22mm thick floor cement board).
RE: Cold Form Steel Roof Joist To Wall Stud Connection???
That still does not get your roof diaphragm shear into the strapping. The devil is in the details here (and with light gage in general) You might need to add strapping from the backside of the parapet down to the diaphragm and figure out how to make a tension connection for strap at the diaphragm edge member.
The parapet detail works alot better with plywood sheathed walls as getting the load into the shearwall is easy.
You could also consider platform framing this thing and adding diagonal braces from the roof deck to the parapet.