Shear Value for Drift Pin in 8x8 column
Shear Value for Drift Pin in 8x8 column
(OP)
I have done a fair bit of timber engineering, but I am not quite sure how to ACCURATELY calculate the shear value of an 8x8 HF2 p.t. post that has been spliced with a 7/8" diameter x 24" long threaded rod, embedded 12" into the center end of each abutting post.
My task is basically to develop a splice that will be as strong as the 8x8 post was unspliced. I have the moment connection taken care of with straps on all sides.
The post already has this 7/8" rod in the center, so I need to know what the shear value of it is.
If you cannot help me do this, please do not suggest other ways of making the connection. That is out of the question at the moment.
Thanks,
My task is basically to develop a splice that will be as strong as the 8x8 post was unspliced. I have the moment connection taken care of with straps on all sides.
The post already has this 7/8" rod in the center, so I need to know what the shear value of it is.
If you cannot help me do this, please do not suggest other ways of making the connection. That is out of the question at the moment.
Thanks,





RE: Shear Value for Drift Pin in 8x8 column
http://www.awc.org/pdf/tr12.pdf
www.SlideRuleEra.net![[idea] idea](https://www.tipmaster.com/images/idea.gif)
www.VacuumTubeEra.net
RE: Shear Value for Drift Pin in 8x8 column
RE: Shear Value for Drift Pin in 8x8 column
I'm making a spreadsheet for these equations (and the ones you provided above). If anyone knows of such a thing existing already, please let me know.
thanks
RE: Shear Value for Drift Pin in 8x8 column
RE: Shear Value for Drift Pin in 8x8 column
So...I went through those god-awful General Dowel Equations and came up with a controlling Yield Mode IV, P = 4087 lb. After dividing by the Reduction Term, I got a Z = 1022 lb.
Can anyone verify that with a program, etc? That seems pretty low to me for the connection I described above. The shear capacity of an 8x8 HF2 post is about 6118 lb before duration factors.
I'm looking at a funky custom fab'd steel collar or something to develop the full shear capacity, unless I can get more value out of the dowel.
Thanks in advance.
RE: Shear Value for Drift Pin in 8x8 column
Just to make sure that I understand your situation, you have an 8x8 post that needs to be spliced butt end to butt end and that post splice has a shear and moment at the splice. Is that correct?
I don't think that the Yield Mode equations were intended to cover a dowel oriented parallel to the height of the post (column). I suppose that one could resolve the shear & moment at the splice into a couple and design connections to carry those loads. But, it is similar to splicing a laterally loaded beam in the middle of the span; it's just not a good idea.
You might want to check the Product Support Help Desk at www.apawood.org (253-620-7400) or AF&PA at www.awc.org to see if they have any suggestions.
By the way, I get the Fv from Table 4D of the NDS Supplement for Hem-Fir Post & Timbers as 140 psi. I think that gives an allowable shear of 5250 LBS before any Cd factors.
RE: Shear Value for Drift Pin in 8x8 column
In the 2001 NDS, check out 11.3.2.4 and Table 11.3.2 which addresses a dowel inserted into end grain.
I got my shear value from the WoodWorks Sizer program output. I think it may have included some duration factors in the determination of the max shear capacity.
RE: Shear Value for Drift Pin in 8x8 column
Mike McCann
MMC Engineering
RE: Shear Value for Drift Pin in 8x8 column
I did consider that, but what then would you calculate to be the shear value of that dowel? I had to show numbers to the City.
RE: Shear Value for Drift Pin in 8x8 column
I might consider using the P and Q values though for the shear in the longitudinal and transverse direction though with the banding in lieu of other research info. Maybe back off a little.
I would have to think about that one though as you obviously have.
Mike McCann
MMC Engineering