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tower crane punching shear

tower crane punching shear

tower crane punching shear

(OP)


I have a tower crane that will be supported on a mat foundation by the anchor above. I am wonder others thoughts on the punching shear check for this. I can see it two ways - assume bearing at the top of the mat slab due to the plate and stiffeners, or bearing at the bottom, 2'-5-5/8" into the concrete. This will obviously make a large difference in how thick I need to make the mat slab. Any thoughts / opinions?

RE: tower crane punching shear

When I see this, I imagine a punching shear failure starting from the bottom plate and propogating out at 45 degrees.
Once this failure plan fails, the assembly still can't go anywhere because of the top plate.
I vote for punching shear checks based on the top plate.
The bottom plate is likely there for uplift resistance, or "negative punching shear"

RE: tower crane punching shear

Agreed with Once. Though if you got this rocking back and forth (compression-uplift-compression-uplift-etc) then I imagine you could have some weird hybrid punching shear failure.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: tower crane punching shear

Not to tell you to pass the buck, but when I design TCF's, the crane manufacturer always provided the anchors that the base section attaches to. Along with providing the anchors, they also provided the minimum thickness of slab needed.

If you've got the time to look at this, great. But if you need an answer PDQ, you may be better off contacting the anchor manufacturer.

RE: tower crane punching shear

(OP)
Thanks, that was my initial thought too. Wanted to make sure it sounded reasonable to others as well.

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