Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
(OP)
In the design of conveyor box trusses, it is common practice to provide a slotted connection on one end of the truss to allow for thermal expansion & contraction. Typically, this detail consists of a long slot in the plate attached to the truss. (This allows the slot to be aligned with the truss.)
Basically, it's a 2.4375" C1045 pin, a 3" x 7.5" slot, and a 1.5" thick plate. The maximum reaction (ASD) is likely around 100k.
Here's the question - what's the best way to check the bearing capacity of the pin on the slotted hole? I've done some research on my own in regards to Hertzian contact stress and have come to the conclusion that there is no consensus. So.....now what?
AISC J7(b) doesn't apply to this situation (as confirmed by AISC themselves) since it deals with a wide flat surface. This should be fairly similar to Roarke's Chapter 14. I also came across a paper written by Dekker "You Can't Trust Your Lift Ears" (June 1996, Chemical Engineering Magazine) that includes a similar check for lifting lugs. However, if you use any of these methods, the allowable bearing stress is GREATLY exceeded.
So how is this handled? Is a bearing failure (dishing) just assumed to be acceptable in this situation? This connection detail is used widely in the industry, so there's certainly plenty of empirical evidence showing that it "works". So, most likely, the calculation shortfall is likely due to a misunderstanding in what is actually happening.
Any thoughts?
Basically, it's a 2.4375" C1045 pin, a 3" x 7.5" slot, and a 1.5" thick plate. The maximum reaction (ASD) is likely around 100k.
Here's the question - what's the best way to check the bearing capacity of the pin on the slotted hole? I've done some research on my own in regards to Hertzian contact stress and have come to the conclusion that there is no consensus. So.....now what?
AISC J7(b) doesn't apply to this situation (as confirmed by AISC themselves) since it deals with a wide flat surface. This should be fairly similar to Roarke's Chapter 14. I also came across a paper written by Dekker "You Can't Trust Your Lift Ears" (June 1996, Chemical Engineering Magazine) that includes a similar check for lifting lugs. However, if you use any of these methods, the allowable bearing stress is GREATLY exceeded.
So how is this handled? Is a bearing failure (dishing) just assumed to be acceptable in this situation? This connection detail is used widely in the industry, so there's certainly plenty of empirical evidence showing that it "works". So, most likely, the calculation shortfall is likely due to a misunderstanding in what is actually happening.
Any thoughts?






RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
As far as the guided slide bearings......any details for something like this?
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
http://www.granor.com.au/products/structural-beari...
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
Personally, I let it happen on industrial structures as long as it keeps within drift limits and the rotations at member connections aren't crazy. Heck, it's pretty standard practice as far as I know to build outdoor racks and things with a braced anchor bay and just let everything deflect out away from it.
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
TLHS - I've worked in the material handling (coal) industry for 11 years now as an engineer and I don't think I've ever seen a conveyor system that DIDN'T implement some type of slotted hole corbel for each & every truss. I'm not saying it can't be done.....it's just what the industry has typically demanded. Heck, it's standard to provide expansion joints for handrail & conduit as well. In addition, the main supporting buildings at the end of these conveyors typically support the internal belt tension from the conveyor system. Due to this high lateral load, these buildings are subjected to a reasonable amount of drift. If the conveyor truss are somewhat rigidly attached then that load is then partial resisted longitudinally by the trusses, which isn't desirable.
Interesting discussion guys......thanks for your input so far!
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity
RE: Conveyor Truss Corbel Pin - Expansion Slot & Bearing Capacity