Structural Engineering: RE: Wood interior wall studs

Do you design a mosh pit floor with Cd=1.6 or 1.0?

-----Original Message-----
From: Joseph R. Grill [mailto:jrgrill@cableone.net]
Sent: Friday, July 13, 2007 12:50 PM
To: seaint@seaint.org
Subject: Re: Wood interior wall studs

"impact" being an important descriptive word, therefore, 1.6 Cd.

----- Original Message -----
From: "Andy Heigley" <aheigley@jgaeng.com>
To: <seaint@seaint.org>
Sent: Friday, July 13, 2007 1:45 PM
Subject: RE: Wood interior wall studs

> Actually the 5 psf is due to HVAC.
>
> Here's and excerpt from the IBC Handbook:
>
> "According to BOCA/NBC, the requirements of this section, reproduced from
> the 1999 BOCA/NBC section 1606.9, are intended to provide sufficient
> strength and durability of the wall framing and wall finish, so that a
> minimum level of resistance would be available to nominal impact loads
> that
> commonly occur in the use of a facility and to HVAC pressurization."
>
>
>
> Andrew Heigley, PE
>
>
>
> -----Original Message-----
> From: Haan, Scott M POA [mailto:Scott.M.Haan@poa02.usace.army.mil]
> Sent: Friday, July 13, 2007 4:25 PM
> To: seaint@seaint.org
> Subject: RE: Wood interior wall studs
>
> I think the 5 psf is intended for people slam dancing on the walls - not
> for
> pressure from HVAC. The IBC has the 5 psf in the Live Load section. The
> 97
> UBC says the 5 psf is "L" and does not need to be applied with wind or
> seismic.
>
> I would use the 1.15 Cr and 1.0 for Cd for the 5 psf.
>
> -----Original Message-----
> From: Joseph R. Grill [mailto:jrgrill@cableone.net]
> Sent: Friday, July 13, 2007 12:16 PM
> To: seaint@seaint.org
> Subject: Re: Wood interior wall studs
>
> There is also repetitive member increases in bending. 15% usually, but
> the
> code allows 50% if a wind load.
> Joe Grill
>
> ----- Original Message -----
> From: Jordan Truesdell, PE
> <mailto:seaint1@truesdellengineering.com>
>
> To: seaint@seaint.org
> Sent: Friday, July 13, 2007 1:07 PM
> Subject: Re: Wood interior wall studs
>
> I do a lot of wood, and here's my take:
>
> The 5psf should be at a Cd of 1.6. Why? Unless I have an
> intentionally pressurized room (which is not the case here), there is no
> possible way that common construction techniques can _maintain_ that kind
> of
> pressure differential over an extended period of time, and if you have a
> constant load (say, a commercial kitchen with doors that seal
> tight...right...) making the pressure differential then the HVAC engineer
> should already be providing makeup air in that area. The building code
> can
> call it a "live" load all it wants, but the actual duration of load will
> never reach 10 years in the 50 year design life of the building.
>
> Roof live load should be given a Cd of 1.25; snow is 1.15.
>
> I don't recommend a loadbearing wall of 10' in height be made of
> 2x4s. Why? Because the walls will not be sheathed before the floor joists
> are
> set into place. The code limits the L/d ratio to 75 for construction, and
> a
> 10' 2x4 has an L/d of 80. The contractor cannot build the wall unless he
> plans on bracing every stud without violating the code.
>
> And, for the record, I agree with Don that 2x4s 10 feet long look a
> lot like spaghetti. And as a bearing wall they give me the willies. My
> answer
> to such a request is normally to do it as designed, or provide another PE
> to
> seal off on the change with full calculations, and provide me with a full
> release of liability should anything happen. I've never been taken up on
> the
> offer.
>
>
> Jordan
>
>
> Andy Heigley wrote:
>
> Everyone:
>
>  
>
> Thanks for your responses...
>
>  
>
> Here are my responses to some of your questions back:
>
>  
>
> * I would design for LL and LLr if the wall were
> supporting both the floor and roof loads.
>
>  
>
> * I am designing to ASD.
>
>  
>
> * I guess I'm a little leary of using the Cd of 1.6
> for
> this reason. The duration factor is applied to both bending and axial
> capacities. Applying 60% more to the allowable axial stress makes a huge
> difference. And if you have a 4 story building, for example, you are
> going
> to be approaching the capacity of the stud just due to DL and LL... you
> then
> add a "little bit" of short term horizontal loading to the stud and
> increase
> the capacities by 60% seems non-conservative.
>
>  
>
> * Scott: I haven't found the rated wall design
> reduction factors you've mentioned. Can you tell me the code section that
> is
> in?
>
>  
>
> * 10'-0" high 2x4's... exactly why I initially called
> for 2x6 stud walls, but the GC is flipping out about it... I get the old,
> "I've been doing this for 30 years, and never had to do this before"...
>
>  
>
>  
>
> Andrew Heigley, PE
>
>  
>
>  
>
>  
>
>
>
> ******* ****** ******* ******** ******* ******* ******* *** * 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@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@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:
> *
> *

******* ****** ******* ******** ******* ******* ******* ***
* 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@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

******* ****** ****** ****** ******* ****** ****** ********