caisson reinforcement

[walteraz]

I am looking at a design of a caisson (two in total) supporting a sign. The caisson is 4 feet in diameter and is embeded 14 feet. The column for the sign is a W shape and extends to the bottom depth of this caisson. There is no reinforment in this caisson. Is it required? What guides the design of this reinforment if it is? Thanks for any help.

 

[Bagman2524]

Try ACI-318. Chapter 22 is a section for structural plain concrete.

 

[denoid]

I'm not sure if they still show it, but the older CRSI manuals used to show the caisson reinforced to a depth of 3 x caisson diameter, or 10 feet, whichever was more. The reinforcing was temperature only, and caisson was designed as plain concrete. Reinforcement ratio was 0.005 x area.

 

[damstructural]

For a sign with this depth footing, I would expect the critical loads to be lateral due to wind. You might consider dropping in a spiral cage or WWF for good measure, depending on the the size of the W section and soil.