cbsq lateral design

[allcad1]

Hello all,

I would like to ask of the considerable knowledge base here about a design problem.

I have a 15' high 8'8X20' deck on 8-6X6 df#1 posts. I calculated the seismic shear at the base at 230 lbs. The issue I have is that the column is in a cbsq66 in 14"sqX24" dp. footing.

Simpson has not included any lateral design loads in the data. However, there is the pbs66 data that is sufficient for the job. The contractor wanted the cbsq in the design.

Can I infer that since a pbs66 is adequate for the job that the cbsq66 would have at least as much lateral capacity?

Thanks for your consideration.

allcad1

 

[BAretired]

Check with Simpson for confirmation. Don't assume anything.

BA

 

[msquared48]

I would seriously question taking any lateral force through the columns with that connector, let alone the other one, without the use of knee braces. Depending on the layout of your deck, to develop any shear at the column base parallel to the edge of the deck, you must have some fixity at the top connection of the post. Otherwise, you are just kidding yourself.

Mike McCann
MMC Engineering

 

[allcad1]

Hello all,

Yes, of course consulting Simpson would be ideal.

msquared48, the column is indeed knee-braced at the top in both directions.

Here is the pdf of the section views...they are a work in progress. Perhaps they will be more descript of the problem.

allcad

 

[msquared48]

As a side note, the engineer of record specifies the connectors, not the contractor. He can ask, but the engineer makes the call.

I cannot believe that Simpson would not put in the lateral values if it was tested and rated for those loads. Do what BA said and call Simpson, and be ready to tell the contractor what to use.

Mike McCann
MMC Engineering

 

[XR250]

I run into this all the time on decks. Very few of Simpson's bases are rated for lateral load. I most cases, such as yours, the shear is so low, I tend not to worry about it. By inspection, that connector would take a 230lb lateral load - it just has not been tested for it. It is 10ga and has a bunch of SDS screws.
It seems Simpson would make a lot more money if they had lateral load capacity in more of their bases.

 

[allcad1]

Hello all,

I received word back from Simpson on the cbsq matter. Here is the text:

Joseph,

I’m sorry, but that is not something that we can support. The published PBS loads are based on tests and calculation, whereas the CBSQ has not been tested in lateral loading.

Thank you,
Dustin Muhn, M.S.
Simpson Strong-Tie

However, I would have to agree that for the design load applied that, by inspection, one can see that cbsq is at least as adequate as the pbs66. This is not an assumption I take lightly.

Thank you all for your time and consideration.

Joseph

 

[RFreund]

Simpson, Decks, Code requirements and money. I think there is a serious love rectangle their. That may or may not be justified. #justsayin

EIT

http://www.HowToEngineer.com

 

[msquared48]

"However, I would have to agree that for the design load applied that, by inspection, one can see that cbsq is at least as adequate as the pbs66. This is not an assumption I take lightly."

You will not be able to prove that to the local building department if they question it. It's your call though. Personally, I wouldn't.

Mike McCann
MMC Engineering