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Prying Forces

Prying Forces

Prying Forces

(OP)
does anyone know where i could get some good information on prying forces in bolted connections?

RE: Prying Forces

AISC Manual - see p9-10 of the 13th edition.  

RE: Prying Forces

VDI 2230 Systematic Calculation of High Duty Bolted Joints, available from Beuth:

http://www.beuth.de

Regards,

Cory

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RE: Prying Forces

AASHTO section 10.32.3.3 refers to prying force limitations for high strength bolts.

RE: Prying Forces

desertfox-
did I miss something?  I didn't see anything about prying on that page.

RE: Prying Forces

Hi StructuralEIT


Scroll down the page till you see the heading:-

Strength of bolt joints withstanding bending forces


Theres a bracket fastened to a wall with formula's for an offset horizontal or vertical loading putting the bolts under a moment loading.

regards

desertfox

RE: Prying Forces

desertfox, it appears that the paper you cite includes bending in terms of moment on the connection.  Prying is not stated as being covered.  I'm assuming that the prying that jmc2000 is concerned with is the force caused by a connection plate that is thin enough to deform under load and therefore bends up on one side, causing more tension on one side under the bolt head.

RE: Prying Forces

desertfox-
That example only covers shear and tension combined.  I still don't see any reference to prying.  As kbarnett says, prying is when the tensile load that is transferred to the bolts is increased from that of the connecting element (usually a WT or angle) as a result of the lack of rigidity of that connecting member.  
I do a ton of prying problems for Flexible Wind Moment Connections.  AISC 13th edition page 9-10 is the best reference.  There are many papers written also, but I have yet to find one that deals with anything other than a WT.

RE: Prying Forces

Hi kbarnet

If you have a bracket fastened to say a vertical wall with
a horizontal projection say a foot or whatever, you then apply a vertical load to that projection either up or down.
The bracket will try to pivot at the wall on one edge.
If the bracket as a vertical line of bolts then the force
in each bolt will be different due to the levering effect and consquently the bolt furthest away from the pivot will see the greatest load in this case.
The link I have posted shows this situation of a line of bolts having to withstand an offset load  on a bracket but assumes that the bracket base is rigid in which case all the load is transfered from the bracket to the bolt.
I can't post the diagram from the site I have tried but its under the previous heading I posted earlier.

Regards

desertfox

RE: Prying Forces

desertfox-
I understand your statement, but that is still NOT prying action.  That is a resolution of the eccentric load into a direct shear and a moment.  Then each bolt takes tension based on its distance from the NA.  
Look at AISC 13th Edition page 9-10 for a discussion of prying.

RE: Prying Forces

Try here, an old reference:

Old Reference

RE: Prying Forces

Hi StructuralEIT

Will study the reference you gave me in detail and comment later thanks!

regards

desertfox

RE: Prying Forces

Hi StructuralEIT

I looked at the reference very kindly posted UcfSE (thankyou).
I agree having read this that prying is accounting for the
increased load due to deflection of mating parts which are bolted together and subject to forces offset from the bolt line.
When I read prying forces in the original post I merely thought of the bolts being levered out by a rigid based bracket as described in my earlier posts.
In addition to my original thinking I looked on the "The Bolt Science" Site which gave a definition of prying as:-

PRYING
The amplification of an external force acting on a bolt by a lever action which can occur when that force is an eccentric tensile load.

regards

desertfox

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