[GSBN] 7story SB buildings in France

[John Straube]

HAving done some work with CLT, I can tell you that this is a pretty neat product.  But it seems to be used more because it is cool than because it fits the bill.  For high concentrated loads it is great, e.g. the high shear load resistance mentioned by Bob, or as a core for a mid-rise. But is pretty wasteful to use a vertical load bearing element in a 2 or 3 storey building, e.g. 2x6 at 16" can usually deal with those loads just fine.
But I would disagree with Bob's statement "strength of concrete with just 16% of the weight".   Not sure what that means.
Concrete is about 150 pdf density, and CLT is a little under one third of this, say 40 pcf.  The capacity in compression of CLT is well under 1/2 that of decent concrete.
In bending, CLT is obviously pretty darn good, but a solid floor panel of 5"-5.25" is going to weight about 13 psf, whereas a a hollow core concrete plank would be about 55 psd, or 4 times the mass for the same function.
As usual, some materials are better for some purposes than others-- wood is good in bending and concrete is great in compression.

On 2013-05-16, at 5:29 PM, Bob Theis <bob at bobtheis.net> wrote:

> Hi Martin, 
> 
> I can't answer your last two questions, but the structure is Cross Laminated Timber panels  ( CLT ) and it is the Hot New Thing for commercial mid rise construction .The strength of concrete with just 16 % of the weight. 
> 
> First time I saw pictures,  my thought was " Egad, that's a lot of wood! " but I'm warming to it. 
> 

John Straube
www.JohnStraube.com