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RE: Beam unbraced length

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I tried the plates but, as you guessed, then the beam was too deep. I can, although just intermittently, weld short, tiny L-shaped stiffeners between the web and the inner side of the outer flange, but the free distance between the flanges, not counting the space occupied by the blinds, is just 2-1/8 in. I´ve tried to sketch the beam (see below), although not showing that the window post (mullion) actually sits at the apex of two glass panes, i.e. the glass is inclined both in plan and elevation.
Wind suction plus internal pressure is much higher than wind pressure on the panes, so the critical flange is the inner (smaller!) flange. As has been mentioned on this list recently, stiffeners like those mentioned above are not effective, or at least it is extremely complicated to quantify the increased lateral-torsional buckling strength.

	 _+_		Anchorage & thermal insulation
 _______=________	Glass-
 -------|--------	panes
	=====		Outer flange 2-1/2x1 in.
	  |		Web 2-1/8x3/4 in.
 ------]|[-------	Blinds
	 ===		Inner flange 2x1 in.

Well, I guess I could go on forever. It´s not like I´m pressed for time. The foundation is already casted, the gliding forms for the tower are being assembled and production of the main structural steel is started.
Gunnar H. Isleifsson

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)]
Sent: Thursday, March 20, 2003 00:45
To: seaint(--nospam--at)
Subject: RE: Beam unbraced length

Well, you *do* have an interesting structural problem, Gunnar.

I have one more thought, then I will shut up.

Have you looked at welding plates in a triangular shape to the compression 
flange(s), thus:

         \       /
           \   /

or would that add too much depth to the W-beam?  Thick cover plates could 
also accomplish the same thing.

Good luck!

A. Roger Turk, P.E.(Structural)
Tucson, Arizona


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