ASCE 7-10: 12.3.3.4 - 25% Increase of Diaphragm Connection to Vert Elements/Collectors

[dcvo89]

Per ASCE 7-10 Sect 12.3.3.4 for horizontal irregularity type 4 (offset shear wall from floor to floor), there is a 25% increase in the connection of the diaphragm to the vertical element/collector. I'm looking at this SKGosh article, and it says that you increase the force by 25% for the connection of the diaphragm to the vertical element/collector but don't need to check the diaphragm shear. My question is if I check the connection for the 25%, wouldn't that automatically be applying the 25% to the diaphragm shear since I'd be looking at the shear capacities for a diaphragm from the SDPWS? Or would the diaphragm connection be a different check than just looking at the diaphragm shear capacity?

A question that stems from this would be how the shear capacities are derived for diaphragms per the SDPWS. Do they take the single shear dowel yield equations from the NDS and apply all the factors to get what is shown in the SDPWS?e

Thanks,

 

[KootK]

My question is if I check the connection for the 25%, wouldn't that automatically be applying the 25% to the diaphragm shear since I'd be looking at the shear capacities for a diaphragm from the SDPWS?

In practice, it's likely to just be your fastener spacing that is affected by the 25% increase. And there's no requirement to carry that fastener spacing into the field of your diaphragm. You may choose to in order to reduce the potential for field errors but there is no requirement to.

A question that stems from this would be how the shear capacities are derived for diaphragms per the SDPWS. Do they take the single shear dowel yield equations from the NDS and apply all the factors to get what is shown in the SDPWS?

I've always assumed the values to be derived from testing but, now that I think about it, I'm not so sure. Hopefully one of our wood experts can confirm or deny that. While the fasteners usually seem to be the heart of the matter, there are other potential failure modes such as shear buckling of the diaphragm panels.

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.