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RE: Wood Beam Torsion

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Ray,

I actually resolved this. The model code used required only a calculation for a 200 pound lateral load applied at the top of the railing 42 inches above the deck. In this case it resolved into a reaction in tension of close to 1100 pounds depending on the applied direction of the 200 pounds (in or outward). The torsion issue is small as the aluminum track for the glass rail is bolted through the rim beam at 12-inches on center and the code also says to check for shear based on the application of 50-plf laterally at the top rail (whichever is worse). The assumption is that the glass comes in 48” sections and this is the worst case load when considering the bending arm. The shear is low – 50 pounds between the wood beam and bolted connection.

In short – the beam has a tendency to pull away from the face of the TJI joists when a lateral load is applied at the top of the rail. Therefore, I used a Simpson LTT19 at the top and bottom and spaced it 48 inches on center to resist the tensile reaction. The strap is bolted through the 4x beam and the washer and nut are recessed so that lath and stucco can be used to conceal the connections.

 

Thanks again for your help – I think I have this one back on track (pun intended)

 

Dennis

 

-----Original Message-----
From: Ray Shreenan [mailto:rshreenan(--nospam--at)earthlink.net]
Sent: Tuesday, October 07, 2003 12:14 PM
To: seaint(--nospam--at)seaint.org
Subject: Wood Beam Torsion

 

Dennis:

 

I would like to help but I'm not sure I understand how the glass rail is supported laterally and attached to the wood rim beam.  Is the 600# load the result of the 30' rail span x 20# / ft.?  Is the 24# / sq. ft. a wind or seismic load?  Normally the top rail spans to line posts at 6' +/- that cantilever off from a rim joist or beam. Is the aluminum track a structural member?  Do we finally have structural glass? :>}

 

Thanks for your help with my wood beam repair.

 

Regards

Ray Shreenan