Thread Pitch and Size
Thread Pitch and Size
(OP)
I'm looking at a 10" diameter tower crane tieback with an in line adjuster composed of a 4" diameter threaded rod that screws into 3" thick end plates. So the tieback looks like this:
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The -'s represent the threaded rod
This rod will therefore take all of the 200kip of axial force. How would one specify the thread pitch and type on a connection like this? Is there any way to verify the axial capacity of the threaded connection?
||||||||||||||--|||||
The -'s represent the threaded rod
This rod will therefore take all of the 200kip of axial force. How would one specify the thread pitch and type on a connection like this? Is there any way to verify the axial capacity of the threaded connection?






RE: Thread Pitch and Size
RE: Thread Pitch and Size
RE: Thread Pitch and Size
In the new 13th Ed. LRFD/ASD Manual, Table 7-18 is "Threading Dimensions for High Strength and Non-High-Strength Bolts." It would give you the net area to use in the Ch. D rupture calcs.
RE: Thread Pitch and Size
Do you apply rupture limit states to thread area? I want to determine if the bolt will strip out of the 3" deep tapped hole.
RE: Thread Pitch and Size
I don't know any way to check a shear limit state in which the threads shear off, which I think is what you're envisioning. If I wanted to check that, I would probably figure out the shear plane area. Divide the load by this area and see what kind of stress I come up with. Hopefully it will be very small.
RE: Thread Pitch and Size
RE: Thread Pitch and Size
I dont know why AISC doesnt incorporate this into the book since it would apply to stripping leveling nuts on anchor rods during construction. Doesnt seem to be much info about it out there.
RE: Thread Pitch and Size
3" of threads is a lot! Still worth a calc, though, if you're up for it.
RE: Thread Pitch and Size
RE: Thread Pitch and Size
Yeah, this is one of the reasons for my last post. I've seen plenty of bolts break during destructive tests, but never one that broke by shearing off the threads. From that, and the lack of mention of it in the AISC Spec., I've pretty much written it off as something that won't control for normal conditions with a full nut, etc.
RE: Thread Pitch and Size
My point is, to be safe, I'd like 4 inches minimum of threaded material thickness to carry a 4 inch rod.
RE: Thread Pitch and Size
I don't even know if 4" to carry 4" really proves anything, though because Fy and Fu for the plate are so much less than Fy and Fu for a nut.
RE: Thread Pitch and Size
htt
When using the following site set the input and output to high
http://www.turula.com/bolt.html
RE: Thread Pitch and Size
more practical advice.
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Here is fastener system you may want to consider.
http://www.superbolt.com/index.html
RE: Thread Pitch and Size
In lecture 28 by Dr. Robert Lemaster at UTM (University Tennessee, Martin) there is a very good reference, as we used to say with pictures, to Thread Shear Stress Area on page 21 of this paper.
http://ww