lumber decking connection to steel joists 4

[sponcyv]

I'm using a diaphragm of 3" lumber decking oriented at 45 degrees and bearing directly on steel roof joists. Has anyone done this before and how did you connect the decking to the joists? I was thinking I could bold a nailer down to the top chords and nail the deck to this.

Thanks

 

[SteelPE]

Never done it before but make sure you connection complies with the SJI requirements. I believe they require the connection of the TC of the joist to be capable of resisting a 300# load at a maximum of 3'-0" o.c.

 

[sbisteel]

On the west coast it's a somewhat common practice on larger warehouses to attach plywood diaphragms to steel joist & girder systems.
The joist manufacturers attach a 2x wood nailer to the top chord of the joists themselves. The attachment uses tek screws spaced evenly on each side of the chord.

Depending on where you are located, it might be worth giving a joist manufacturer a call and find out what their capabilities are.

 

[msquared48]

I agree with the above. It's a nono to drill the flanges of these joists yourself. If it is done at all, it must be by the manufacturer to maintain the warranty.

Mike McCann
MMC Engineering

 

[SteelPE]

I can't believe I have ever seen any diaphragm values for decking at 45 degrees. Is this something that you are calculating yourself or something you have numbers on?

 

[OldPaperMaker]

SteelPE,
The 2009 IBC, Section 2306.2.2 points one to the AF&PA Special Design Provisions for Wind & Seismic for design values. I think that it is Table 4.2C. The allowable shear for diagonal lumber sheathing (1 or 2x sheathing) is 300 plf for seismic & 420 plf for wind loads.

 

[sponcyv]

Great responses guys - I like the idea of getting the joist fabricator to attach the nailer.

SteelPE - the link below is an old posting in this forum. Taro (about half way down) references the ANSI/AF&PA SDPWS-2005 for values. Horizontal orientation gets you 50 lb/ft seismic, 70 lb/ft wind. Diagonal orientation gets you 300 lb/ft seismic, 420 lb/ft wind.

file:///S:/2011/2011-100%20Woodstock%20Park%20Expansion%20&%20Amphitheatre/Research/Structural%20engineering%20other%20technical%20topics%20-%20T&G%20Decking%20as%20diaphragm.htm

 

[SteelPE]

sponcyv

I don't think you link works but thanks for the effort.

Thanks for the information. This is something I have never come across but if I do in the future now I know.

 

[sponcyv]

yeah, for some reason it didn't show up as a link, but if you copy it and paste it in your address bar, it will take you to the right page

 

[Brad805]

I think Hilti would be a good one to talk to also. Nailing the plate to the joists is not much different than nailing down a steel deck diaphragm. Once you have that connection, everything else is standard timber framing engineering.

I can't see a big joist manuf. like Vulcraft or Canam installing wood in the factory, but you can always ask. I can hear the response if I asked our contacts at those two. You want us to do what? Followed by, sorry, we are not in the wood business.

I have looked at a number of these from the 70's, and I sure do not like the connections they used, but those seemed to be largely the architects doing since they did not seem to think they needed any assistance other than what they could find in 2nd year engineering texts.

Brad

 

[OHIOMatt]

I toured the Vulcraft (now Nucor) site in Utah about five years ago. They had railroad car loads of 3x and 6x lumber on site to connect to joists and joist girders. At the time, they said that about 50% of the joists fabricated had nailers on them. As stated above this is common on the west coast.

I do not know of any manufacturer's that install the nailers east of the Rockies. Location and shipping costs will determine availibility.

As far as the warrenty issue goes, I cannot see how they can make the justification that nails or screws will void it. Metal decks are fastened to joists with pins all of the time (the deck catalog produced by Nucor show this as an acceptable installation).

 

[dhengr]

I wonder if this wood nailers on steel joist, affixed at the plant, won’t come around fairly quickly, whether east or west of the Rockies. Given that we are all dealing with larger lateral loads, and larger shear/roof diaphragms all the time. The building codes are forcing this, not surprisingly west of the Rockies first. Have your east of the Rockies plant talk to a few of their west coast brothers if they want your joist order.