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RE: Beam unbraced length

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The glass is an "insulating glass unit" with a two-ply laminated glass on the inside and a thick monolithic pane on the outside. Glass thickness is based on windload results from wind tunnel tests, as well as acoustic and temperature criteria. I've learned more about glass in the last weeks and months than I ever thougt possible (or preferable). The requirements are one-piece, motor-driven blinds, made of material that functions as sunglasses, and due to the irregularly trapezoidal shape of the glass panes, the blinds have to be either in top or bottom position. The geometry of the structure means that no two glass panes have the same dimensions, so the blinds have to made specifically for each window pane. There is one vertical symmetry plane in the stucture but the glass panes positioned symmetrically about that plane are mirrored. The horizontal mullion (I had to look that word up in my dictionary), which I use for bracing, can only be connected to the outer flange of the window post, or else the blinds can?t run past them.

Gunnar H. Isleifsson

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)]
Sent: Wednesday, March 19, 2003 17:33
To: seaint(--nospam--at)
Subject: RE: Beam unbraced length

Gunnar Isleifsson wrote:

. > a picture is worth a thousand words

which leaves me speechless <G>.

Sloping glass in aircraft control towers is common, but I don't know if the 
panes commonly used are of comparable size.  Have you contacted glass 
companies to see how they have handled this in other situations?

I noticed that there is a horizontal mullion.  Has it been suggested to the 
architect that separate window blinds be used in different parts of the 
window to give the controllers maximum flexibility in controlling 

There are a couple of "inverted pyramid" buildings in Arizona that have the 
outside surface sloping at 45 deg.  The first one that I was aware of was the 
Tempe (Arizona) City Hall, designed by the architectural firm, Michael and 
Kemper Goodwin and built in the late 1960's, early 1970's.  The intent, IIRC, 
was to reduce cooling costs by limiting the time windows are exposed to 
direct sunlight.  A copycat building was built here in Tucson several years 
later and it seems that the windows are magnets for rocks and/or bullets.  Of 
course, in these buildings, minimizing obstructions was not a primary 
concern.  The City of Tucson keeps microfiche copies of plans indefinitely 
and are public records; the City of Tempe, IIRC, keeps plans only 24 months.

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


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