Southern Pine design values and the IBC

[RWW0002]

I know there have been several posts concerning the reduction in Southern Pine design values over the past year, but varying agencies and sources seem to be at odds on whether NDS Supplement 13 (with an effective date of June 1 2013) has already taken affect for all new IBC-based design or whether local jurisdictions must adopt the change.

The following from Southern Pine Inspection Bureau implies that enforcement varies by jurisdiction (see Q11).

http://www.southernpine.com/media/QA_NDVs_060113.pdf

This "non-mandatory unless approved" sentiment is echoed in several other sources, but I was under the understanding that since ALSC (American Lumber Standards Committee)approved the change per IBC referenced ASLS PS 20, the values take affect June 1, 2013 and should be used for design without specific jurisdictional approval. (Sorry for all the acronyms)


Bottom line, if the local jurisdiction (under IBC 2006 or 2009) has not mandated the use of the new design values and has not approved any amendment to the prescriptive design sections of the IBC, do the updated design values have to be used?

 

[AELLC]

What do you mean , a jerk?

The internet is not like conversing in person.

Sorry for any misunderstanding, English is my second language, altho I live in the USA>

 

[Jerehmy]

"What do you mean , a jerk?

The internet is not like conversing in person.

Sorry for any misunderstanding, English is my second language, altho I live in the USA> "

I've seen your posts numerous times and you have perfect english so now I'm not sure if you're straight up trolling me. Whatever.

 

[AELLC]

OIC, you though I was being sarcastic - when I re-read my own post, it did seem so. No intent of sarcasm at all, I was thinking that the FoS gives me much more confidence in my wood design

 

[AELLC]

It is not trolling, cool your jets. I have lived the USA a long time but French is my preferred language.

 

[AELLC]

Also I am very dyslexic and I leave out words, a few typos.

But I am saying that I was totally not realizing I sounded so sarcastic - I can see that now re-reading my post,

No harm intended.

 

[AELLC]

also, I used to be known in these fora as "SacreBleu"

 

[Jerehmy]

Haha well I'm glad I just misunderstood you. All good

 

[EngineeringEric]

The values for the wood tested are the values for the wood that are being purchased, used, and loaded. It is therefore prudent to design based on what will be used. I would not wait for building code officals to release a statement that they now only accept new NDS values... do you think the lumber suppliers will sell product as pre-Code decreased #2 SYP or post-Code #2 SYP? The wood is what it is and it is our job to state what load to wood can withstand.

Now i will state that when analyzing older SYP i would use the old NDS value (say 2003 construction) but new members for repairs will be for new reduced values.

And Thank you AELLC, I have ended up numerous online conversations coming off as a jerk when i did not intend. Now i do not feel alone anymore

 

[AELLC]

LOL Eric,

I started this online stuff way back on AOL in one of those chat rooms (actually the Architectural chat room)
Have a hundred war stories there - and we baited and tortured rude newbies mercilessly there.

 

[AELLC]

Back on topic, IMO we can take a lot of liberty with stress allowables, but deflection is real and doesn't give you any reserves, if any.

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.

 

[XR250]

@RWW0002

"Why do the strength reductions only seem to affect short spans? The fb values saw a significant reduction (20-25%).
This should affect long spans more than short unless you are saying that these spans are deflection controlled anyway."

Yes, because, in my experience, serviceability seems to control most designs in wood construction.
SYP is rarely used for walls or roof framing (in our area anyhow). Usually only for floors and beams. That is because SPF is lighter and straighter.

 

[EngineeringEric]

Not that i disagree with you all, but i just ran some live roof valleys (they are SYP here, if not LVL) and they actually governed by moment not deflection at a span of 10.5 (true span 15.6). So as with all things, i think all aspects need to be looked at... But we all do that anyways right?!?

 

[EngineeringEric]

Oh the days of AOL and Dial up..... so worth the 90 free minute CD install!

 

[XR250]

I can see that for a hip or valley. I read a HUD design manual once that said you did not need to check deflection of hips and valleys due to folded plate action making them much stiffer than they are alone. I check it anyway.

 

[RWW0002]

It looks like we may be using spf wall studs more often here as well now that we do not get much help from Southern Pine design values. Although, the irony of this is that So Pine values have been reduced due to their rigorous testing protocol. My understanding is that other lumber species are not tested with this frequency, and may exhibit similar loss in design properties (it just has not shown up yet). I predict we will see a reduction across the board (at least with pine species) in the next year or so. In the meantime, it will appear as though So. Pine is weaker in comparison to SPF.

 

[EngineeringEric]

FYI, around my part Mid-Atlantic US:
SPF for 2x4 and 2x6
SYP for 2x6 and up

 

[idecharlotte]

Most framers I've talked with hate using SYP and the few times I framed houses, it was a PITA to work with because it was twisted, knotted, excessively crowned. We never called it out before due to these reasons. We've always used Spruce. The design value changes pretty much reinforce this decision.

http://www.idecharlotte.com

 

[AELLC]

SPF, Hem-Fir, and all their variants.

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.