[Greenbuilding] Advanced framing/OVE / 100 years from now

[Drew A. Gillett P.E.]

you can look at this the other way.  the sheathing (1/2 inch ply or 
whatever) has enough strength to hold up the building and the 2x stuff just 
keeps it from buckling. ( after all 24 inches of 1/2 inch is 12 sq. inches 
which is bigger than the 2x4 , especially the new ones and even bigger than 
a new 2x6.

my mit structures professor had a saying  for this , let the big beam carry 
the load .  in these composite structures the stiffer section takes on more 
of the load.

this is why sips panels which are only foam and sawdust board can be 
structural wall panels supporting a second floor and roof.
----- Original Message ----- 
From: "Rob Tom" <ArchiLogic at yahoo.ca>
To: "GB REPP" <GREENBUILDING at listserv.repp.org>
Sent: Thursday, March 08, 2007 1:48 PM
Subject: Re: [Greenbuilding] Advanced framing/OVE / 100 years from now


> On Wed, 07 Mar 2007 12:48:00 -0500, John Salmen <terrain at shaw.ca> wrote:
>
>> If a 2x4 represents 1/3 less lumber than a 2x6 and is virtually
>> equivalent in load bearing
>
>> Lawrence Lile wrote:
>
>>> 2X4 on 24" centers isn't very good construction, IMHO.
>
> FWIW, for stud-grade SPF dimension lumber "2-bys" 2400mm long (~8 ft),
> laterally-supported (ie by sheathing), using LSD (no Alan, not LSD a la
> "Wavey Gravy",  LSD = Limit States Design) procedure for compression
> members, (ie Pr = phi*Fc*A*Kd*Ksc*Kt*Kh*Kc) and a quickie back-of-the
> envelope calc, then the axial load capacity of:
>
>   a 2x4  = 12.7 KN (~ 2850 lbs)
>   a 2x6  = 22.8 KN ( ~5116 lbs)
>
> Which is to say that literally-speaking, a 2x4 stud is not equivalent to a
> 2x6 stud in loadbearing, obviously.
>
> For a single storey 9m (30 ft) wide building where the stud is just
> supporting the live and dead loads of a simple trussed roof in a locale
> where there is snow loading, say 4.4 KPa combined factored LL + DL, the
> factored axial load on each stud would be 12.2 KN which is to say that 2x4
> studs @24" o/c would be fine .
>
> Make that a 2 storey building so that the lower storey studs are carrying
> the loads from the second storey floor as well as the roof and the
> factored load on each stud goes up to 17.2 KN, beyond the capacity of a
> 2x4 for this example scenario.
>
> The key to OVE I suppose is the "Engineering" part.
> What may seem like cheap insubstantial work may in fact be an elegant,
> efficient use of minimal materials if engineered properly. Improperly, and
> you may create bad situations.
>
>
> === * ===
> Rob Tom
> Kanata, Ontario, Canada
> <A r c h i L o g i c   at  c h a f f y a h o o   dot   c a >
> winnow the chaff from my edress in your reply
>
>
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