Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Building Frame Shearwall Height Limit on UBC Table 16-N

[Subject Prev][Subject Next][Thread Prev][Thread Next]
	The best thing to do would be to set up a meeting with the building
department and see what their view is on the matter.  Structurally, I don't
think 240' is a "magic" number aside from it being in the code.  You could
make a strong argument for fitting the 240' criteria if you only had a
parapet or a even a lightly framed machine room extending above the limit,
but having substantial rigid extensions that affect the behavior of the
walls may be too much for them.  Even then, there are some west coast cities
that have set aside the 240' limit for shear walls where non-linear,
performance based design is done.  

Paul Crocker, P.E.

-----Original Message-----
From: John Diebold [mailto:Jdiebold(--nospam--at)SanDiego.gov]
Sent: Tuesday, October 01, 2002 10:33 AM
To: seaint(--nospam--at)seaint.org
Subject: Building Frame Shearwall Height Limit on UBC Table 16-N


When referencing the height limits for structural systems in UBC Table 16-N,
what does the height limit mean? For instance for a building frame shearwall
system where the typical framing is a coupled shearwall system extending to
a "roof" level of 240'-4" above grade, but has a parapet extending an
additional 4'-0" and elevator machine room and architectural concrete fin
extending to 272' above grade. Would the height limit of 240' for the
building frame shearwall system permit such a structure by being interpreted
as the height limit for the particular structural system, with the extended
machine room walls and architectural fin above the 240' level being
considered additional masses to be lumped at the 240' level? Or, should the
limit be interpreted to mean the highest point of the structure, or highest
roof diaphragm level? 

The elevator machine room and fin are not small items for this particular
project. They are both cast in place concrete and connect to the major
lateral force resisting elements for the building. It is possible that these
"stiff" shearwall type elements extending approximately 30 feet above the
building frame shearwall height limit could have a stiffening effect on the
coupled walls that comprise the main lateral load resistance for the
building. (I.e. the so-called "top-hat" effect where stiff elements at the
top of the building control the deflections of the softer coupled walls
below.) In such a case, these elements may not be so "minor" in nature.



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********