Simpson Tables and LVL 1

[BSVBD]

According to ESR-1387 that i obtained from Weyerhauser, the wood used in LVL and PSL material can be any combination of DF-Doug Fir Larch, LP-Lodgepole Pine, WH-Western Hemlock, SP-Southern Pine, YP-Yellow Poplar, RM-Red Maple, and EUC-Eucalyptus.

When considering LVL supporting material, when referring to Simpson Allowable Load Tables, the conservative approach is simple - use the SPF/HF tables rather than DF/SP. However, conservative can mean specifying a hanger(s) that can be significantly more expensive.

If the published, Reference Design Shear Values of the LVL exceed those of DF/SP, is this a justifiable reason to use the DF/SP tables?

Is there more i should consider?

Any thoughts?

 

[jayrod12]

I'm not 100% sure for the allowable side of simpson stuff. However up here simpson publishes specific engineered lumber capacities in their catalogues.

 

[mike20793]

There may be some kind of adjustment factor based on the specific gravity of the overall LVL compared to the assumed specific gravity for the Simpson values. Does the report mention anything about the specific gravity? It may be worth contacting Simpson to find out for sure.

 

[Triangled]

as mike20793 above, i'm pretty sure it's a specific gravity thing, as that's what governs NDS fastener values, and I think the LVL guys publish a specific gravity for use with their products. I seem to recall 0.50 for the one's I have worked with, which of course gets you to the DF values in the simpson catalogue.
I always read all the footnotes in the engineered wood literature as they seem to commonly make the high design values prominent and than bury limiting factors in small footnotes. For example, different brands have differences between face nailing and edge nailing in LVL

 

[BSVBD]

jayrod12 - If i am understanding you, from the Simpson 2015-2016 C-C-2015 catalog, as well as those from the past, although Simpson does provide hangers for "Structural Composite Lumber", the Allowable Load Tables only provide loads to supporting members of DF/SP or SPF/HF. Are you implying that a catalog that you have specifies LVL under the Allowable Load table? If so, what is that Catalog number?

I found the Specific Gravity of 0.50 which meets the better specific gravity of Doug-Fir.

Further, Weyerhauser provides Specifier's Guide #TJ-9000, which provide a limited Allowable Load Table for LSL, LVL & PSL support members with values identical to DF/SP.

Can any of you guide me to documentation in NDS, or elsewhere, stating that specific gravity is what governs NDS fastener values? Using NDS frequently, i understand specific gravity plays a significant role, but, is specific gravity the sole governing physical property for Chapter 11 (2005)?

 

[Signious]

From the Canadain wood connectors catalog notes (LSD) on page 152 (SDW lamination guide):

Note 5:

'Verify the effective specific gravity with structural composite lumber manufacture for selection of tabulated values'

They numbers they quote for SCL specific gravity on the following page are for 0.5 and 0.42. The 0.42 numbers line up as slightly higher than a comparable SPF table and the .50 numbers line up as slightly higher than the d.fir table.

Taking that - I just assume an LVL acts like a D.Fir and something like an LSL that has around a .42 SG works similar to an SPF. Might be a little presumptuous to apply this throughout the entire catalog though.

 

[jayrod12]

BSVBD, you are correct, I misunderstood you. I thought you were talking about the supported member, not the supporting member. However, Signious has answered your question.

 

[Triangled]

BSVBD:
"Can any of you guide me to documentation in NDS, or elsewhere, stating that specific gravity is what governs NDS fastener values? Using NDS frequently, i understand specific gravity plays a significant role, but, is specific gravity the sole governing physical property for Chapter 11 (2005)?"
I was thinking of the varying "G" values across the top of most if not all of the NDS chapter 11 tables. Certainly not the 'sole' factor.

 

[Signious]

@triangled

Not sure about NDS, but OS86 has some great formulas if you want to dive down the fastener hole.

 

[Triangled]

Looking at specific gravities from 3 different LVL manufacturers.....
some have this and some have that
some have this but allow it to be adjusted for that
some have numbers that vary if fasteners in edge or in face
some have values varying for loading parallel to grain or perp to grain
some have values varying between screws and lag screws

enough variation to caution me against just selecting DF/SP or SPF/HF values from the catalogue.