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RE: Wood interior wall studs

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

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

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


----- Original Message -----
From: "Andy Heigley" <aheigley(--nospam--at)jgaeng.com>
To: <seaint(--nospam--at)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(--nospam--at)poa02.usace.army.mil]
> Sent: Friday, July 13, 2007 4:25 PM
> To: seaint(--nospam--at)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(--nospam--at)cableone.net]
> Sent: Friday, July 13, 2007 12:16 PM
> To: seaint(--nospam--at)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(--nospam--at)truesdellengineering.com>
>
>        To: seaint(--nospam--at)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:
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                Thanks for your responses...
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                Here are my responses to some of your questions back:
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                *       I would design for LL and LLr if the wall were
> supporting both the floor and roof loads.
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                *       I am designing to ASD.
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                *       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.
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                *       Scott:  I haven't found the rated wall design
> reduction factors you've mentioned.  Can you tell me the code section that
> is
> in?
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                *       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"...
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                Andrew Heigley, PE
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>                <!--[if !supportEmptyParas]--> <!--[endif]-->
>
>
>
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