Simpson SDS Screw Issue 1

[XR250]

Need to try to get some additional capacity out of some SDS screws due to an installation issue. This is 1 1/4" solid bar is supporting a cabinet off an LVL. They had to lower it due to an unforeseen soffit. Here are my questions.

1) The hole in the solid bar is 9/32" - or 1 /32" bigger than the shank of the screw. Due to it being solid bar, could I consider this to be a pseudo-dbl. shear situation as it will force the screw shank to remain perp. to the LVL.

2) If they were to drill additional holes in the bar for more screws, can I just use NDS spacing rulee? The literature from Simpson that I found is not clear on the spacing.

Thanks!

 

[jayrod12]

I don't see the second shear plane that would imply double shear, even though the bar will hold the fastener perpendicular.

But yes, most of the simpson and GRK products indicate that NDS (or CSA for us Canadians) spacings and edge distances. I believe however, Simpson uses lag screw provisions and GRK uses wood screw provisions. You'll need to ensure you're using the appropriate provisions for the size of fastener you're using.

 

[XR250]

That's fair. I suppose maybe it changes from a Type II failure mode to a Type III mode. I'll have to run the numbers to see if that makes a difference.

 

[phamENG]

1) Single shear all day long.

2) ESR-2236 - SIMPSON STRONG-DRIVE SDS SCREWS

 

[Eng16080]

1. Considering that there's only one shear plane, I would say no to double shear. The fact that the screw will rotate very little within the thick steel side member should be accounted for in the various yield mode equations of NDS, Chapter 12. I would expect that Modes Is and IIIs would therefore not control considering that they are a function of crushing in the steel side member. Alternatively, a more exact analysis per AWC TR12 can be used (see NDS Appendix I). I don't know if that will result in a higher capacity though, and I'm not sure you want to spend the entire day deciphering that document.

2. Get Evaluation Report ESR-2236. Tables 4A and 4B give spacing requirements. It looks like you're probably limited to a 3" spacing based on testing by Simpson or 1.75" per NDS recommendations.

 

[XR250]

Ahh, did not think to get the ESR report. Thanks for the advice!
I sharpened my pencil on the design loads and it looks like they are OK based on a reduced number of fasteners.

 

[KootK]

By pseudo double shear, I imagine that you meant a half model of the dowel limit state that would be applicable to double shear. And I could get behind that.

 

[bones206]

Since you have the bottom hole available, you could maybe thru-bolt an angle iron as a support bracket below the cabinet.

 

[AaronMcD]

I don't even have the ESR in my files. I just open a tab and type "SDS ICC" and it pops right up every time.

http://www.hellodwell.design

 

[bones206]

Same here. I used to hoard ESR's like a squirrel, then I realized they expire and get revised and renumbered constantly.