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RE: Discontinuous Shear walls

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Andrew:

Doug's point (and that of the code provision) is that even _IF_ the
equivalent lateral loads that you calculate for wind are greater than
those for seismic, you must still detail your structural/lateral system
per the appropriate seismic requirements.

If my memory serves correctly, you are in Dublin, OH.  I would assume that
your project is some where near by.  That being the case you are using a
"form" of the IBC code since Ohio adopts the IBC for use.  More than
likely, your project is a Seismic Design category B, but could be as high
as a C or as low as an A.  So, the point is that even if the wind loads
are greater, you must still follow the detailing requirements for SDC B
(assuming your project is a SDC B) or whatever, as well as any other
general seismic detailing requirements in the code that would apply to
your project.

Now, you don't need to use the Omega factors with the wind loads, but if
there are restrictions that would apply for seismic, then they would also
apply for wind.  As a PURELY hypothetical example, let's say that the code
in the seismic provisions said that you could not do discontinuous shear
walls in appartment buidlings (which the code obviously DOES NOT say),
then that would also apply even if wind governs.  The point is that even
though in theory wind loads would cause the problems in a design level
event, there still could be a seismic event and so you need to follow the
requirement for seismic even if may never result in the governing event.
Think of it like this...you have just been shot with a mortal wound (i.e.
you are going to die from it) but are still trying to rush to the hospital
for treatment.  You would say "I am dying...I don't need a seat belt", but
if your state law says the you must where a seat belt, then by law you
would be requirement to wear a seat belt even if you are more likely to
die of the gun shot before you would die from a car accident without a
seat belt on.  The seat belt might be totally unnecessary but it is still
required just a seismic design might be totally uncessary in a wind
governed situation.

HTH,

Scott
Adrian, MI


On Fri, 6 Oct 2006, Andy Heigley wrote:

> Doug,
>
> I know I always have to design for seismic but even with the overstrength
> factor applied to seismic forces, the wind forces still control.
>
> Andrew Heigley, PE
>
>
> -----Original Message-----
> From: Doug Mayer [mailto:dougm(--nospam--at)teterae.com]
> Sent: Friday, October 06, 2006 12:46 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Discontinuous Shear walls
>
> Andy,
>
> Per the 2001 CBC section 1626.3:
>
> Seismic and Wind Design.  When the code-prescribed wind design produces
> greater effects, the wind design shall govern, but detailing requirements
> and limitations prescribed in this section and referenced sections shall be
> followed.
>
> I take this to mean that even if wind loads govern, you still have to design
> and detail based on seismic requirements.  I don't know if there is a
> comparable section in the IBC, but I would assume there is.  Hope that
> helps.
>
> Doug Mayer, S.E.
> Structural Engineer
>
> teter a+e, LLP
> Architects & Engineers
> p: 559.437.0887
> f:  559.438.7554
> e: dougm(--nospam--at)teterae.com <mailto:dougm(--nospam--at)teterae.com>
> w: www.teterae.com <http://www.teterae.com/>
>   _____
>
> From: Andy Heigley [mailto:aheigley(--nospam--at)jgaeng.com]
> Sent: Friday, October 06, 2006 5:50 AM
> To: Seaint
> Subject: Discontinuous Shear walls
>
> Somewhat keeping on topic, I have a multi-story apartment building, where I'
> m losing a lot of shear walls at the 1st floor, but my wind design force is
> significantly more than seismic.  Are there any provisions for
> discontinuities in vertical resisting elements that are controlled by Wind
> forces?  I know that in the seismic chapter, there's the vertical structural
> irregularities table, to which gives you provisions for seismic, but
> obviously, losing the lower level of a 2 or 3 story shear wall has
> significant affects under either wind or seismic loadings.
>
> Also some food for thought.  do you guys feel that the building codes should
> possibly add section in the structural chapter for irregularities, and the
> provisions for both wind and seismic listed in a table.  I think that would
> be helpful.
>
> Andrew Heigley, PE
>
> Dublin, OH
>
>

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