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RE: Joist Seat at Roof

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Ken,

 

Thanks for your responses.

 

I considered all those options.  I have a mix of tube columns and WF columns.  I need a cap plate for the joist anyway.  I was just trying to catch two items at once, a cap plate and a wind moment connection.  I thought about the eccentric seat.  It seemed like a lot of money for just 3/8 inch.  That is why I didn’t use that detail.

 

It’s a good idea to make a note though, like you said, to cut off a potential RFI.

 

Thanks.

 

Rich

 

 


From: Ken Peoples [mailto:kspeoples(--nospam--at)lvta.net]
Sent: Tuesday, November 14, 2006 2:54 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Joist Seat at Roof

 

I don't see any real problem with the concept as long as it is clearly shown so the steel detailer understands that this joist is to be 3/8" higher - otherwise he may RFI it to see what you really want to do.  Another option would be to use angles with the vertical legs down for the top flange wind moment resistance.  Then the cap plate can be at the correct elevation.  Keep in mind that this usually reduces the number of shear bolts that you can get in the connection by one row so you might want to bump the beam depths up by one size to allow that extra row of bolts to fit in.  A third option is to use the cap plates for the beams and put a stiffened seat angle for the joists to bear on.  So many ways to skin the cat.

 

Best regards,

 


Kenneth S. Peoples, P. E.

 

LVTA
Lehigh Valley Technical Associates, Inc.
1584 Weaversville Road
Northampton, PA 18067

 

Phone: 610-262-6345
Fax: 610-262-8188

----- Original Message -----

From: Rich Lewis

Sent: Tuesday, November 14, 2006 3:31 PM

Subject: Joist Seat at Roof

 

I am considering a detail and would like to get some feedback.

 

I am detailing a wind connection at the roof level of a building.  I am using a 3/8” cap plate on top of the column.  The cap plate is the top flange plate of the bolted wind connection to wide flange beams.  I have a steel bar joist sitting on top of the column.  The roof steel is flat.  Tapered insulation is used for drainage.  I’m considering letting the joist sit directly on the cap plate.  This makes the joist 3/8” higher than the joists between columns.  As I see it the deck can flex up 3/8” at the column line.  I think the perimeter chord angle could also flex up at the column line.

 

Does anyone else do this?  I can’t foresee a serious problem caused by this.  Am I forgetting to consider something here?  Has anyone run into problems that would cause me to rethink my options?

 

Thanks for your insight.

 

Rich