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Re: Wood - Radiused GLB Roof beams - outward thrust deflection question

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The AITC Timber Construction Manual 3rd Edition is very similar to the 4th
edition regarding the design of curved glued laminated timber beams. The 4th
Edition is available from bookstores for AITC at 303-792-9559.

What is the span of the radiused GLB. Generally for shorter spans, say up to
30 feet, the amount of horizontal movement is typically less than 1/2 inch for
the dead loads you described. The AITC Timber Construction Manual (TCM), 4th
Edition, recommends that the horizontal movement of the curved beam (under the
section for pitched and curved beams) be detemined using equation 5-72. That
is, delta horizontal = (2*h*Delta center) divided by span. It also recommends
that the horizontal movement be allowed for in the connection using slotted
holes and bearing on an "antifriction pad". A detail of this type of
connection is shown in AITC 104, Typical Construction Details. This standard
is included in the reference section of the TCM. However, it does caution that
this connection may not be suitable in seismic zones.
You may want to consider the curved beam as a two hinged arch. Design methods
and examples are also included in the TCM.

On another subject, Lurking -- I have been on the list serve for approximately
one year and have participated only once or twice. I am primarily interested
in wood designs and have found may of the topics regarding shear walls, hold
downs etc. for conventional wood framing very interesting. Since I am in
Colorado, much of the seismic design discussion is very informative, but I do
have quite a time in picking up on the terminology and thought processes. One
suggestion to the group is to define what an acronym stands for (at least once
in the email) and then feel free to use it throughout the remainder of the

I am a CE registered in Nebraska and Colorado, currently living in Lakewood,
Colorado. Much of my professional experience is with Glued Laminated Timber,
"glulam" or GLB. I was the Technical Director for the AITC (American Institute
of  Timber Construction) and am currently working for Wood Composites
Engineering (WCE). At WCE, I am Senior Engineer and QC Director of the
Inspection Department. We are working with glulam manufacturers and the new
fiber reinforced glulam.   

Bruce Pooley, P.E.
Wood Composites Engineering
303-989-9693 (fax)