Attached Deck Seismic Analysis 1

[dgengineering]

Hi everyone,

I have a deck addition project and it's gonna be attached to an existing 2 story house. The plan checker is asking to check existing house for additional seismic load from deck. It says, "please justify (E) lateral force resisting system of house subject to additional lateral load for flexible diaphragm is structurally sound".
The problem is I don't have existing framing plans, I don't know which walls are shear walls etc. Is there another way to do this? Maybe ASCE 7-16 has some requirements for it. Can you please give me some advice?

Thank you very much

 

[driftLimiter]

You can try checking the provisions for alterations in the IEBC.

It would look something like, estimating the lateral load existing on the exterior wall.
And comparing the new lateral load against that. If it doesn't exceed a threshold indicated in IEBC you can argue that no upgrade is required.

 

[dgengineering]

Very helpful, thank you

 

[lexpatrie]

The IEBC is generally not for residential, it's outside the scope but it might be "deemed to comply" if you went that route.

Usually residential structures are "designed" as braced wall systems, though it would depend where you are, and if you are in D[sub]0[/sub], D[sub]1[/sub], or D[sub]2[/sub] it's fairly challenging.

I don't think you need to prove the existing structure, it's the changes in the loads due to the deck addition, but the existing condition would be useful in finding just how much the deck changes things. Generally the deck is pretty light, and I'd be surprised if you develop more than the prescriptive 1,800 1.500 lb attachment at the ends of the deck, the braced wall system is another question, though.

The FAQ entry has a link to the 2013 article in Wood Design Focus on seismic load determination, that may be of some use. Let us know, I haven't read it.

ETA: Finally found that thread where I had the required load wrong. Corrected to 1,500 lbs now.