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RE: Three Hinge Glulam Arch

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Chris-
One area where I've seen difficulties with glu-lam arches is at the base.
Some designers don't design the support shoe to drain water and consequently
create the perfect environment for dry rot to occur.  Be sure to pay close
attention to the details in this area.  Treated wood only slows down the
deterioration by a little.  Keeping the water from collecting seems to be
the trick.

Regards,
Bill Cain, S.E.
Oakland  CA

 -----Original Message-----
From: 	Bruce Pooley [mailto:bdpooley(--nospam--at)home.com] 
Sent:	Tuesday, May 01, 2001 1:11 PM
To:	seaint(--nospam--at)seaint.org
Subject:	Re: Three Hinge Glulam Arch

Chris

Since your arch is being designed for wet-use conditions (EMC of the wood
16% and greater) both the Modulus of Elasticity and radial stress design
values  would be affected by the wet-use factor. Csub D (wet-use factor) for
MOE is 0.833 and 0.875 for radial stress.

Methods and equations in the AITC Timber Construction Manual can be used
(for the 4th Edition, see pages 5-294 through 5-306).

Bruce Pooley
Timber Design
3448 South Newland Court
Lakewood, CO 80227
----- Original Message -----
From: "CDaniels" <ced(--nospam--at)larsondesigngroup.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, May 01, 2001 12:52 PM
Subject: Three Hinge Glulam Arch


I am currently designing a 3-hinge glulam arch roof (r=31.33', span=59') for
a roadway sand and salt shed.  I am using STAAD to model the arches (I
divided the arch into 20 equal straight line segments).  I did this for more
or less the convenience of manipulating the different load combinations
required.  My question is there any criteria I should be looking at for
deflection due to seasoning (i.e. shrinkage or swelling).  I know AITC has a
method for computing the seasoning effects on deflection and radial stress
for haunched or tudor arches but I have a true circular, constant section
arch and I expect the equilibrium moisture content inside the building to be
18 to 25%.  I don't any experience with glulam arch design.  Any input would
be appreciated.

Thanks,

Chris Daniels
Larson Design Group
ced(--nospam--at)larsondesigngroup.com

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