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Re: 1970's Panelized Roof - Question

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Dennis

Glulams usually have a AITC grade stamp someplace on each member.  This
stamp is unfortunately on the top of the member thus indicating the face
of the member to be placed up especially applicable on non-symmetrical
laminated members.  Having the contractor check would be worth the
effort though

Dennis Wish wrote:
>
> Thanks Steve,
> While I agree, I can't get to the jobsite until next weekend since it is
> 90 mile east of here in Blythe. This is a problem with many of these
> small towns out here in the desert, the nearest engineer is a couple
> hours away.
>
> I think I covered some of your comments in my other post - I do,
> however, have to rely upon the contractors measurements unless he can
> wait a week.
>
> Let me ask you this - to the best of your knowledge are there any grade
> stamping used on GLB's used in commercial buildings? How can I identify
> the GLB grade to obtain an appropriate Fb and E value? Where GLB's
> stamped and if so, was the camber indicated anywhere or the manufacturer
> on the member?
>
> Thanks
>
> Dennis S. Wish, PE
> California Professional Engineer
> The Structuralist.Net Information Infrastructure
>
> Website:
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>
> ."The truly educated never graduate"
>
> -----Original Message-----
> From: Steve Privett [mailto:eqretrodr(--nospam--at)earthlink.net]
> Sent: Monday, February 11, 2002 10:27 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: 1970's Panelized Roof - Question
>
> Dennis,
>
> I'd look at the condition personally rather than relying on the
> contractor.  Beam sizes were typically 5 1/8, 6 3/4,  8 3/4, & 10 3/4.
>  Depths were in 1 1/2" increments with depths at 24, 25.5, 27 etc.
>  Weyerhaeuser did list 3/4 inch increments, but they were not the
> common.  Also field verifying may show cantilevers over columns by as
> much as 20% of the span.  And I'm used to seeing panelized roofs with
> 2x4 @ 24, not 16, and purlins of 4x12 (marginal) or 4x14.  I also seem
> to remember designing panelized roofs, that we referred to as
> trampolines, @ 10 psf dl when there was a t-bar clg.  I don't know how
> you can verify the make up of the GLB, but we worked with Bevon-Heron
>  extensively in the mid 70's and everything we did specified combination
>
> 24F lumber with tension lam top and bottom.
>
> I think it's critical that you control the placement as increasing shear
>
> capacity is usually easier than bending. I've used new platforms that
> span between glb lines to not load the purlins or subpurlins.  I've also
>
> used platforms that point load the purlins which are then reinforced by
> bolting members to each side as required, below the subpurlins. I've
> also used the tension cable a couple of times, but found bolting members
>
> to existing was usually easier with regards to dealing with the
> contractor.
>
> The contractor wants to place the units for minimal duct work, but when
> you tell them to figure the additional engineering and structural
> retrofitting costs to handle the units where he wants them, the cost of
> additional duct work is easier to swallow.
>
> Good luck
>
> Steve P
>
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BBFM Engineers, Inc.
Ph (907)274-2236
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