Anchor bolts at Cold Formed Steel Shear Walls

[reviest54]

Our firm has a lot of experience with residential wood construction but we are being asked more and more to design with cold formed steel studs and wood sheathing to make up the lateral force resisting system. My questions are about the anchor bolts:

1. Is there a quick reference for designing the track capacities for the anchor bolts similar to the tables in the NDS for wood?
2. Should we provide a washer similar to a plate washer used in wood shear walls?

Thanks.

 

[jayrod12]

Personally for the horizontal shear I think something like concrete screws would work best, for the uplift at the boundary elements, I think you're better off with a hold down fastened directly to the stud pack.

 

[DaveAtkins]

I use power driven fasteners for cold formed steel shear walls, for shear along the base, and a hold down at each end when necessary.

DaveAtkins

 

[reviest54]

Thanks for the responses. Not sure if plan checkers around here will allow the shot pins. I emailed CFSEI the same question and got the response below:

There is no recommendation to use washers. The use of washers would depend upon the need for additional bearing capacity. Section E3.3.1 of AISI S100 provides design equations. The bearing strength may be determined either with or without washers by using the m_sub_f parameter in the equation.

 

[Ceinostuv]

I do work in mostly Seismic Design Catgory D and have been told/researched that PAFs generally aren't acceptable for use as shear wall anchorage in SDC D, E, and F... I'd guess that you're right in avoiding them but I'd honestly take DaveAtkins' word over mine...

DaveAtkins do you have experience with light gauge shear walls in high seismic regions and do you know if there's an "out" that lets us use them as shear wall anchors?

Otherwise, SSMA has allowable shear loads for fasteners up to 1/4" dia. I'm not aware of any quick references beyond that but I've been lucky enough that most of the shearwalls I've designed using light gauge have had pretty low unit shears and I've gotten away without using anything larger than 1/4" dia.... I'm sure I'll need to at some point, so if you find anything, please share

Judgement-In-Training

 

[wannabeSE]

In case you’re interested, AISI has a research report, RP 13-3, testing tracks fastened to concrete wit PAFs

https://cfsei.memberclicks.net/research-reports

 

[DaveAtkins]

No, all of my projects have been in low seismic regions.

DaveAtkins

 

[Ceinostuv]

For anyone interested, I came across an alternative method adopted by the State of Oregon that allows the use of PAFs as shear wall anchorage by reducing published allowable values by 50% for interior walls. I haven't come across anything similar for other states.

Judgement-In-Training