Uplift on single anchor 1

[dgkhan]

When moment is applied on steel column, the base plate resists by axial forces in anchors bolts. Moment is divided by anchor bolt spacing to obtian axail compression and tension (uplift) in bolts. What to do if there is only one bolt under one wooden post?

 

[Lion06]

dividing by the anchor bolt spacing is a quick and easy way to get the tension forces, but it's not completely accurate. You're actually getting bearing on one end of the base plate, not compression in the anchor bolts. You might get compression in them if you have a nut on the underside of the baseplate, but the typical details that I've seen don't have that.

For your situation, I would work out a triangular (or rectangular - depending if you are using ASD or LRFD) compression zone and use the distance from the centroid of that compression zone to the anchor rods in tension as the moment arm.

 

[dgkhan]

thanks,
r u still EIT or done your PE and just no time to change name

 

[Lion06]

Still EIT. I have another 1.5 years until I can take the PE exam.

 

[BAretired]

I suspect you won't have much trouble passing it.

BA

 

[swivel63]

me, neither. streit's right. that's how i've always done it.

 

[rb1957]

it sort of depends how the post is connected to the bolt. if the plate is stiff in bending (has gussets) then, yeah, the moment would come out as tension in the bolt and compression on one edge of the plate. but possibly bending of the bolt comes into play somewhere along the loadpath ?

 

[slickdeals]

For a single anchor, the bolt will never be in compression under moment only. Won't the bolt always be in tension for the moment because one side of the plate will be in bearing depending on the direction of moment?

 

[Lion06]

slickdeals-

That's true. Did anyone above suggest something different?


BA/swivel-

Thank you for your kind words. I have a while to wait, and I'm getting quite ansy to take it.

 

[Ron]

SEIT...I agree with your solution and the fact that you'll not have an issue with the PE or SE. One point to add is that the wood will likely fail in compression before mobilizing pullout of the bolt from the concrete. More likely to pull out of the wood first.