Log Beams 2

[medeek]

I've never had to run the numbers on a round log beam before. Looking through all of my software that I use for beam calcs I don't think any of them has the ability to check a DF 11" Dia. Log. Any suggestions?

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[JAE]

"Software! Software? We don't need no stinking software".

Can't you do it by hand? σ = My/I



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[rdubs]

NDS chapter 6 provides design information for round timber poles.

 

[medeek]

I suppose I can but before I go down that route (ie. build my own spreadsheet calculator) I wanted to check in and see if anyone else has a tool out there already available for this sort of thing, or there might be some gotchas that a beginner like myself might make. Typically a quick post to this forum usually helps me identify potential pitfalls.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[KootK]

Look up ICC 400-2007. Excerpt below. It's the different grading that might trip you up.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[msquared48]

The Log Home Builders Association has a lot of good information too, in addition to basic equations.

I believe they are based out of Canada...

Mike McCann, PE, SE (WA)

 

[medeek]

International Log Builders Association:

http://www.logassociation.org/resources/publications.php

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[medeek]

I just remembered I purchased the ICC 400-2012 about 2 years ago, just found it buried beneath a stack of books.

When I compare this standard to the NDS (Ch. 6), the only real difference that I note is that the NDS has a condition treatment factor C[sub]ct[/sub] whereas there is no mention of this in the 400-2012.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[oldestguy]

My "Standard handbook for civil engineers" shows the section modulus as:

pi*R^3/4 or pi*d^3 all divided by 32

Get out that old slide rule and compute.

 

[DaveAtkins]

"Slide rule! Slide rule? We don't need no stinkin' slide rule."

Get out that abacus and compute

DaveAtkins

 

[medeek]

I've spent some time reading the ICC 400-2012 yesterday and some notes by another engineer on log beams. I'm now working up the calculator, once I get it done I'll let everyone know who wants to test it out and tell me what I've got right or wrong. I'm still a little undecided how best to deal with shear stress of a coped log beam at the bearing point.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[dik]

OG... the thought of using a sliderule again, brought tears to my eyes, and I was unable to read the numbers... thanks for the reminder.

Dik

 

[KootK]

Tension side notch? Percentage of depth?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[medeek]

It appears that common practice is to cope the log that is the beam and leave the bearing log mostly un-notched. In some cases the coped log could be notched as much as half the diameter basically leaving a semi-circular cross section at the bearing point.

For a circular cross section the shear stress is 4V/3A, with a semi-circular cross section the other notes I have show a shear stress of approximately double this value, in reality though I think it may be higher due to the oddly shaped cross section and stress concentrations from the cope.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[medeek]

Then there is the SRTB and USRTB. The SRTB can have the compression side sawn off up to 3/10 of the radius of the log. So worst case scenario is a coped log at half the diameter with the full 3/10 sawn off the top for the floor board above, see image below:

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[oldestguy]

For that cross section, isn't this something that we once learned calculus for? By the way my old slide rule is being saved in that some day that antique will be worth a lot to collectors. How'd did the tables of moment of inertia come up for sections such as I beams?

Take a look here. It seems this guy has some info along this line

https://skyciv.com/free-moment-of-inertia-calculator/