Moment Connection
Moment Connection
(OP)
Does anyone have information on the moment resistance of a single slip critical high strength bolt in torsion?
The direction of the torsion vector is in line with the axis of the bolt.
I have a small moment that must be resisted by the clamping action of a single bolt.
Dik
The direction of the torsion vector is in line with the axis of the bolt.
I have a small moment that must be resisted by the clamping action of a single bolt.
Dik






RE: Moment Connection
Limit torque = integral in the standing compressed radius length of mu·sigma(r)·2·PI·r·r·dr
the first r accounts for the ring being integrated and the second for its "polar" moment strength.
RE: Moment Connection
RE: Moment Connection
To tension a bolt is approximately
T = 0.2 F D
To undo a bolt is perhaps 70% of that.
As for DESIGN moment resistance, I'd say zero.
RE: Moment Connection
I agree. Keep in mind that slip critical bolts are still checked for bearing, so that if they do slip, you don't have a complete failure. One bolt in bearing has zero moment capacity.
RE: Moment Connection
The moment resistance for any lateral load has been provided by 1/2" dia A307 bolts and the clamping action of these.
It is not easy to add proper bracing and my initial suggestion was to look at using A325 bolts in slip critical mode. There are in excess of 30 fasteners providing the resistance.
Having nothing better to do and the work is interesting, I've decided to take a closer look at it, just to determine what the lateral capacity of it is. To this end, it is necessary to determine the torsional resistance created by the clamping action. It is max at smaller radius and minimal at the larger radius (with the larger moment arm). The distribution is non linear. I don't know what the outer effective radius is or the manner of pressure distribution between the edge of the hole and the outer radius and I didn't want to FEM it. I was thinking that it can't be that unique a problem that someone hasn't already encountered it.
I'm also aware of the problems associated with opinions as well as relying on clamping of a single fastener to provide resistance.
Dik
RE: Moment Connection
There is no other half to the couple. The moment is resisted solely by the clamping effect of the bolt with the axis of the bolt being the torsional or flectural vector. I'm hoping that the moments from my frame model will be small (only a fraction of the bolt torsional moment). There are a lot of fasteners that must fail (slip) for the rack to become a mechanism.
Dik
RE: Moment Connection
RE: Moment Connection
Installing slip critical connections would be a big hassle too.
RE: Moment Connection
RE: Moment Connection
Dik