Shear Wall with Opening Detail

[chamokinawan]

The NDS SDPWS Section 4.3.5.2 says that "Collectors for shear transfer shall be provided through the full length of force transfer." My understanding is that the collector would be the top plates. However, it was mentioned that the collector are the straps around the opening in the wall. So my straps would have to run throughout the entire wall length? Am I misinterpreting the term "collector" incorrectly?

 

[KootK]

I agree, the wording of that is pretty ambiguous. My take is that the collectors mentioned in that clause are the horizontal boundary elements above and below the opening. Rationally, using standard shear panel assumptions, your pier elements either side of the opening can only extend as far as those horizontal boundary elements run. FTAO walls make sense when the pier elements are rather narrow. Once they get wide, running the boundary elements all the way out to the sides gets silly and the perforated wall method starts to make sense.

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.

 

[chamokinawan]

@KootK : What confuses me about this note is that it also appears verbatim on the criteria for Perforated Shear Walls. For perf. walls, they don't require force transfer straps around openings, so how could they have a "collector". This is why I feel like the collector would be the top plates. And my force transfer straps only need to develop into my piers. Thanks for your input, even on my other thread.

 

[mike20793]

You need a collector or drag strut to get the force to every portion of the perforated wall. The force doesn't just get into part of the wall and the sheathing distributes it appropriately. Perforated shear walls are advantageous due to the fact that you don't have to detail force transfer above or below the opening; instead, you take a penalty by amplifying the shear to design the full height segments. You still need a collector/drag strut to get the load to the entire wall. In most cases, it is the top plate (usually just account for a single 2x), but there have been other cases where it is not. FTAO does not amplify the shear and, instead takes a penalty requiring detailing to transfer the force around the openings.

 

[KootK]

You're quite welcome chamokinawan. This is a worthwhile discussion.

Frankly, I think that it's confusing enough to warrant a clarification from AWC. Regardless, the mechanics of what you actually need to do is clear in my opinion:

1) For both FTAO and perforated shear wall systems, the top plates serve as a collector element.

2) For an FTAO wall, the horizontal boundary elements above and below the openings need to run out to meet the vertical boundary elements at the far sides of piers adjacent to the openings.

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.

 

[chamokinawan]

Thanks mike20793 and KootK. It was a plan check correction, but I decided to give the plan checker what he wants instead of arguing my point. I just wanted to verify that my interpretation of the code was correct.