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RE: Hexagonal Foundation Pedestal for Vessels, Stacks, Etc.

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I would think ( I try not too - it hurts my head ) the vertical bars would 
have to be sized to transfer the tension from the anchor bolts to the 
foundation. Not for compression. A foundation that size must have a lot of 
anchor bolts.

Grumpy old man

-----Original Message-----
From: seaint-seaosc(--nospam--at) [mailto:seaint-seaosc(--nospam--at)] On 
Behalf Of Bill Polhemus Sent: Tuesday, September 30, 2014 2:10 PM
To: seaint-seaosc(--nospam--at)
Subject: [SEAINT-SEAOSC] Hexagonal Foundation Pedestal for Vessels, Stacks, 

This is something that has bothered me for years now, and I wonder if anyone 
 here, who might have some experience with design of foundations for process 
 equipment, has an opinion.

Typically, you have a shallow foundation, or pile cap with deep (pile) 
foundations, one which a vessel or stack is situated. The bulk of the concrete 
 is, of course, simply for the purpose of placing the equipment. The foundation 
 or cap is typically octagonal in plan.

Often, you will see an octagonal “pedestal” on top of a largre octagonal 
 (or rarely, square) foundation. The typical way it’s detailed is the 
foundation has mats of rebar as if it were a slab, and the octagonal 
“pedestal” has verticals as if it were a very large column. This always 
 seemed kind of silly to me. What makes the pedestal “know” that it’s 
 supposed to be a compressive element and the foundation underneath “know” 
 it’s supposed to be flexural?

Typically, the “pedestal” will have vertical reinforcement with “hoops” 
 of what are supposed to be ties. It always seems to me to be a case of 
trying to force some sort of paradigm of a compressive column/pedestal onto

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