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# calculating the required force to break a single rod of a pine wooden dowel?

## calculating the required force to break a single rod of a pine wooden dowel?

(OP)
can the required force for breaking a single rod of a pine wooden dowel be calculated?
Replies continue below

yes

### RE: calculating the required force to break a single rod of a pine wooden dowel?

treat it just like a bolt wood connection only instead of steel its wood

### RE: calculating the required force to break a single rod of a pine wooden dowel?

(OP)
so what is the formula to calculate the force required to break a 10 cm diameter thick with 50 cm long wooden dowel

### RE: calculating the required force to break a single rod of a pine wooden dowel?

The correct formula and material design values, assuming you're designing in the US, would be in the NDS in the fastener area. Specifically dowel fasteners.

### RE: calculating the required force to break a single rod of a pine wooden dowel?

I don't think I've seen yet if this is a shear or bending problem, although the inclusion of the 50 cm length "suggests" bending to me.
No way to know if simply supported, cantilevered, or even if the real question is RE: buckling if loaded as a column.

https://assets.northerntool.com/cdn-cgi/image/fit=...

The poor definition of the problem as posted suggests the OP has some 'splainin' to do, or perhaps a lot of questions to ask.
I'm suspecting perhaps the question was posed to the OP to test their problems solving skills more than to determine if the fictional pine dowel will break.

I think the type of pine ( yellow vs wimpy eastern white), grade of the pine and the orientation of the grain makes a big difference on the "strength" of the dowel used in any calculation.
https://awc.org/publications/2018-manual-for-engin...

### RE: calculating the required force to break a single rod of a pine wooden dowel?

I agree with Tmoose. How can you answer the question if the problem is not sufficiently described? Shear? Bending? Uniform load? Point load? Fixed ends? etc.

### RE: calculating the required force to break a single rod of a pine wooden dowel?

#### Quote (Uralsk)

can the required force for breaking a single rod of a pine wooden dowel be calculated?

I'd say the answer is actually no. You can, however, destructively test it to see the load at which it will break. The coefficient of variability for the strength of wood samples is quite large when compared to other common construction materials. The actual strength of your dowel will depend on variables as obscure as the microclimate surrounding the tree it came from.

The best we can do is assign a reasonable lower bound that, with the use of safety factors, can be used in design to produce a sufficiently reliable structure.

So in addition to the questions others have asked, we also have to ask: is this an academic question trying to determine the actual required breaking load, or are you trying to design a structure that will be used by real people?

One thing to note: wooden dowels in shear connections should be avoided wherever possible. When used in 'old fashioned' joinery, they are typically just there to hold the joint together. All 'design forces' pass from member to member through bearing. When they have to be relied on in shear, they are typically the first thing to fail. Especially if they're made of pine. (Termites love pine.)

### RE: calculating the required force to break a single rod of a pine wooden dowel?

Yeah, all the sources I mentioned really are to figure how to make a part that WON'T break.
Predicting when the dowel WILL break is not quite the same thing. Could require a way higher load.

I wonder if the OP really needs the "force required to break."

OP has been a member for a couple of years, but has not been back since July 7

### RE: calculating the required force to break a single rod of a pine wooden dowel?

#### Quote (pham)

You can, however, destructively test it to see the load at which it will break. The coefficient of variability for the strength of wood samples is quite large when compared to other common construction materials.

Pham is completely correct here. However, one thing that also needs to be considered is the the scenario of the destructive testing. Variability in moisture content of wood, time of development of loading onto test specimen, as well as testing temperature can alter the performance and ultimate failure strength of even identical samples. If you wish to perform destructive testing, a large part of establishing the testing procedures is to account for things like moisture content and load vs time development curve.

### RE: calculating the required force to break a single rod of a pine wooden dowel?

Delete this thread as it is now the third one on the same topic.

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