Existing Glu-Lam Beam size question
Existing Glu-Lam Beam size question
(OP)
I have a set of existing plans from a renovation done in '93. I do not have the original building design drawings. The renovation drawings indicate the main beams are 9 x 35-14 glu-lam beams. Field measurements on the beam confirm the size, but due to inaccessibility of the beam or the beam being painted there are no stamps visible. Has anyone come across a glu-lam beam of this size before? I am also wondering what grade to use, I have tried estimating the grade based on building being in Maryland and the roof load stated on the renovation drawings and what is coming working is a SP-SP 24F-V5. The beam has a span of 52.375' with a stated roof live load of 30psf (which I am putting as a snow load) with a tributary width of 17.708'. the problem I am having is that I do not know if SP-SP glu-lam beams are ones to use for that area or should I be using a different species for this glu-lam beam.
Thanks for your time
Thanks for your time





RE: Existing Glu-Lam Beam size question
Dik
RE: Existing Glu-Lam Beam size question
Extreme Fiber in Bending 2400 psi tension, 1600 psi compression pp25 Table A1
5V stands for number lumber laminates in the outer zones that were visually graded.
AITC 117-2004
https://law.resource.org/pub/us/code/bsc.ca.gov/si...
RE: Existing Glu-Lam Beam size question
Thanks for the response. From my understanding of glulam beams, the size I stated is not a common size for either Western species or Southern pine species of glu-lam beams. The grade I determined is for southern pine - southern pine with an fb of 2400psi (24F). The V5 I believe indicates the laminations are using visually graded lumber vs mechanically graded. The big issue I have is trying to figure out what grade to use so that I can determine if the beam will be acceptable with the new load I will be putting on it. As for species of lumber for glu-lam, I do not know what is common in Maryland.
RE: Existing Glu-Lam Beam size question
RE: Existing Glu-Lam Beam size question
Dik
RE: Existing Glu-Lam Beam size question
Thanks for the replies. We do have all the drawings available, but they do not include original building drawings just a facade renovation drawings from 1993.
I fear may have not asked my question correctly based on the replies you gave. What I am trying to find out is if the size of the beam was a standard size of glu-lam produced back before '93 and if so are the grades of glu-lams used today similar to those back then or was this beam a proprietary size which may or may not conform to American Wood Council/AITC grades.
RE: Existing Glu-Lam Beam size question
RE: Existing Glu-Lam Beam size question
RE: Existing Glu-Lam Beam size question
The size does not seem to me to be a standard size. But the fact that it isn't standard is not bad, it's just not helpful to you to determine the species. Whereas 5-1/8" width is standard for DF today, they can be obtained in 5" 5-18" 5-1/4" and 5-1/2". I have a research paper from the 60s in my file which tested 9" thick DF glulams, and this is definitely not a standard size today. Thickness of laminations can be a clue, but it also is not infallible. SYP lams are typically 1 3/8" (from memory on this one, perhaps it's 1 5/8") and DF is typically 1-1/2". But I recently inspected an older structure with 10 DF laminations in 9". As I understand it, the "5" in V5 does not refer to number of laminations but rather it is simply a number, but it refers to a specific combination regulated by AITC etcetera. The laminator building a beam to V5 combination must utilize specific grades of lumber varied through the depth of the beam to produce the design values advertised, such as "the outer 15% must be high tension capacity lumber ft = x, the next 15% must be such and such, the inner 40% must be such and such... etc". The "V" as noted above indicates Visually graded lumber.
A piece of wood from the beam can be sent to a lab for accurate species determination if desired. I believe the Univ of Wisconsin still offers this service, likely others too.
Glulams have been around a long time and if it's a standard beam in a standard building and not older than the 60s, I think AITC started around 1952ish) I'd be pretty comfortable assuming it corresponds to the AITC.
Good luck!
RE: Existing Glu-Lam Beam size question
The 9" width was probably made from 2x10 lams, which are planed down to give an architectural side finish. I've seen 7" and 9" widths commonly called out in older glulam framing drawings.
RE: Existing Glu-Lam Beam size question
Mike McCann
MMC Engineering
RE: Existing Glu-Lam Beam size question
RE: Existing Glu-Lam Beam size question
Mike McCann
MMC Engineering
RE: Existing Glu-Lam Beam size question
Sided and molded dimensions vary depending upon when it was made. Also, virtually ANY size glued laminated timber can be manufactured as non-standard size.
And most likely "SP" indicates Southern Pine, NOT spruce.
1993 was not all that long ago. It should be simple to track down who manufactured it.
In your new work, allow any lumber species readily available. Southern Pine and Douglas fir/larch are two dominate softwood species utilized in glued laminated timber. Many other species are utilized as well. Specify the loading condition and building code to be met and let the supplier determine which species to furnish. The manufacturers of custom made glued laminated timber know how to design and make the stuff.