Capacity calculation

[Power Builder Engineer]

Hi guys,
There is a size and location requirement for notching and boring in stud, but does anyone knows the limitation of the number of drills in one single stud?
In below situation, do you treat these drills as one when you calculate compression capacity?

 

[KootK]

Like you, I don't think that I've seen a formal guideline on this. I'd be plenty comfortable with something to the tune of 4xD center to center. In a wall stud application you're really just looking for enough longitudinal shear capacity for it to function as a full depth flexural member to the extend that there's wind/eccentricity. I suppose that you could even calculate something based on VQ/It if you're feeling super ambitious. Treat the solid bits like stitch welds. That said, it would take a pretty high demand situation before I'd bother with something like that.

 

[Power Builder Engineer]

If this is a 2x6, and the holes are 2'' in diameer, do you think it's safe to calculate it as a 2x4?

 

[jayrod12]

Ugh, yes, and at the same time no. So I guess maybe. If I was looking at it after the fact, and the holes were drilled cleanly and perfectly centred, I could get behind that. But giving them blessing in advance, I don't think I'd be keen on it.

 

[dhengr]

Power Builder Engineer:
On the one hand, P/A and net area are pretty well defined with the first hole, and another hole on the same axis, same size or smaller, doesn’t do much more damage. As KootK suggested, with sufficient spacing btwn. the holes, and with some effort an effective bending member can be justified with some engineering thought and judgement. This assumes the holes are cleanly done and properly placed. Given the history of PEM contractors and tradesmen putting holes in structural elements this kind of activity should be managed and inspected much more carefully than has been the case. They don’t follow the notching and hole size and location criteria in the codes now, so we should not offer details which allow them to go crazier. Rather, we should be kicking some a$$. If they had to (were made to) pull out and replace some mech. systems and replace some joists, studs, floor systems, at their cost and lost time, maybe they would get the message. If this was done under controlled conditions it could probably be made to work.

 

[sandman21]

IRC has language on the size of the notches and holes. From WFCM 2.4.1.1.1 Notching and Boring

 

[civeng80]

I would find the capacity of a 2x4 and see how much safety factor there is then judge accordingly.

 

[Power Builder Engineer]

dhengr:
You are absolutely correct, I've seen lots of framing mistakes done by reputable builders, calculating the load capacity on the paper is one thing and putting the wood together is another thing. It's very common to see splits in the studs caused by nails, problems like this would be very hard to predict and estimate. How much margin do you usually put in your calculation?

 

[KootK]

If this is a 2x6, and the holes are 2'' in diameer, do you think it's safe to calculate it as a 2x4?

Safe but probably excessively conservative. You're still going to have almost all of the Ix of a 2x6.

 

[msquared48]

If the hole is at the center of the stud, yes, but not so much so if the hole is closer to one edge than the other, with the extreme case being the edges of the hole and the 2x6 touching.

Mike McCann, PE, SE (WA, HI)

 

[Power Builder Engineer]

I’m surprised that no one actually did some experiments about this, pretty common scenario.