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RE: Tall CMU Core Divider Wall

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William,
 
You can't look at a divider wall like this as an 85 foot wall, as you indicate the h/t would be absurd.
 
The wall should be designed to span horizontally for out of plane, and the entire core designed as the vertical element.  Just as the load over a window is really a triangle due to arching action in the masonry, the vertical load in the wall web will arch to the stiffening flanges (perpendicular walls).  You are basically designing a really tall tube.
 
The next hurdle is dealing with any lateral load.  A tube section like this is quite stiff.  You must include this in your lateral analysis, in which case the jambs will likely fail in compression, or you need to detail the wall specifically not to take lateral load (slip the slab connections with rubatex or a similar approach) and design for compatibility of deflection relative to the story drift.
 
The other question is why do you require this interior wall separator at all?  The entire elevator bank can be viewed as a single shaft, and steel beams at the floor lines can provide adequate lateral support for the elevator guide rails between cabs.
 
Paul Feather PE, SE
pfeather(--nospam--at)SE-Solutions.net
www.SE-Solutions.net
 
 


From: William Haynes [mailto:gtg740p(--nospam--at)gmail.com]
Sent: Thursday, November 20, 2008 9:12 AM
To: seaint(--nospam--at)seaint.org
Subject: Tall CMU Core Divider Wall

 
I have an 8" cmu elevator divider wall full height on the building. It is 85 feet tall (continuous) separating the 2 main cmu elevator shaft cores. It is about 8 feet in length and it ties into the cmu shaft walls at each end, and these end walls are tied into the concrete diaphragm.
 
Obviously, this wall does not have any horizontal diaphragm member coming in for support. I have it tied into the perpendicular cmu walls at each end with bond beams at 4'-0". There is the self weight on this wall and a 10 kip point load on the top from the elevator motor. SDC=C.
 
Does tieing it in this way only sound reasonable? The h/t for this wall is ridiculous. But, I can kind of see it just behaving as a series of bond beams (spaced 4'-0" vertically) spanning the 8 feet to the end walls, thereby carrying its own weight as a series of beams.
 
It just looks crazy in the architectural section shown as 85 feet freestanding. But this must be a common situation for a cmu or concrete divider wall in a high rise elevator shaft.
 
WH