Log Structures Lateral Design 1

[TimmyH76]

Does anyone know if log walls have been addressed in IBC in reguards to lateral design (Seismic and wind). I don't see anything in table 12.14-1 in the seismic section for logs? Am I missing it?

 

[msquared48]

I assume you mean the table in ASCE 7-05. This deals with the simplified procedure. Does your building qualify for this table?

I have done these structures for years and would conservatively use resisting system A14, "Light framed walls with shear panels of other materials", giving an R of 2, which I believe to be way too low, but than is what is available.

Mike McCann
McCann Engineering

 

[RockEngineer]

Check out this other thread and the articles from Structures Magazine. It was interesting to me that the most argued about and unresolved item from the new draft ICC spec on log homes was the seismic design value R. One of the articles in Structures magazine recommends a R=4.0 to 5.0. I ususally use 4.0. I tried using 2.0 like Mike stated and here in the Pacific Northwest it produced accelleration loads over 0.5 which is unreasonable. Using R=4.0 usually gives accelleration values between 0.24 and 0.35 which is which is workable.

Good Luck.

http://www.eng-tips.com/viewthread.cfm?qid=150444&page=1

 

[JJMT]

This article should get you in the right direction.

http://www.structuremag.org/archives/2006/March-06/C-CS-Log-Structures-Standard-March-06.pdf

 

[TimmyH76]

Thanks everyone!!

 

[msquared48]

I agree fully with Rock Engineer and have found the same to be true as I am in the Psacific Northwest too, at least I hope to be after the river crests (just kidding). I have never used the vlalue of 2.0, but in the 4 to 5 range too. Seems much more logical seismically considering the behaviour of the structure when you really think about it. I have never had a question from any local or out of state jurisdiction on my method of analysis for these structures, and I am licensed in 4 western states.

I analyze these structures as shear resisting structures, relying on the pins and rods to resist the shear in lateral bearing on the logs. Works for me.

Mike McCann
McCann Engineering