What exactly are Timber Frames in the ASCE7 Table 12.2-1?

[LockeBT]

Not sure why Timber Frames are grouped under Cantilevered Column Systems. My understanding is that typical timber frames involve some form of knee-braces, which is in a gray area between a brace frame and moment frame (if you consider the knee brace as part of the moment resisting connection). There's nothing cantilevered about it. Can someone clarify this for me?

Also if I am designing a simple attached patio cover that happens to be in SDC E, according to the ASCE 7 I can't use Timber Frames as my SFRS? What do we use for lateral resistance on the open side then?

 

[Deker]

I've never found any literature on the what a timber frame system is intended to be. Perhaps it's meant to be used for pole barns? In any case, a knee-braced frame with R=1 would be your best bet.

 

[LockeBT]

Deker,

I'm guessing your intention is just go with the most conservative R value just to be safe? I can roll with that.

However if an R of 1.5 for Timber Frames isn't allowed in SDC E I'm not sure how to justify the use of a system with even a lower R.

 

[Deker]

You wouldn't be explicitly detailing for any amount of ductility, hence the R=1. Judgement plays a role here. For a patio cover, I'd use an R=1 knee brace all day, but for a more substantial structure I'd not recommend it. I doubt you'll have an issue getting City approval for a patio cover.