Industrial Stack repair

[SKJ25POL]

To people who have dealt with tall industrial stacks, I appreciate your comments.
First is there any handbook or text book or papers kind of explain design loads on the reinforced concrete stacks? I know ACI 307 exists.

Also, I see a reinforced concrete stack with bands around along the height, I am wondering what these bands do if the concrete shell not seeing any direct contact with gases? The stack now has independent liner, well not completely independent since the liner is connected to shell in couple elevations! but I guess there is no internal pressure inside the shell to have the bands protect!

Thank you

 

[Agent666]

Can you provide an example of the bands (photo or sketch?), do you mean construction joints? if so is it possibly due to the concrete stack being originally constructed from precast segments that were somehow stitched together in-situ?

 

[SKJ25POL]

Agent666 (Structural), no they are not construction joints. these were added 10-20 years after construction of stack. I just trying to decipher the reason they put these band. They are literally like a belt around the outer shell in spacings.

Unfortunately, I didn't carry camera to take pictures. I thought is very common and no need for pics.
These are steel bands around outside of concrete shell on the outside of surface of concrete stack.

 

[atrizzy]

Perhaps the bands hold studs or something that the liner is attached to?
It's really very hard to say and requires proper investigation.

 

[Sawbux]

Probably added bands after cracks appeared and someone got worried! Differential temperature on inner and outer wall of a thick walled stack could cause vertical cracks.

 

[SKJ25POL]

Sliiderule,
Any comments?
I was hoping get a lot of comments!
Does these stacks due to internal pressure or because they are open in top there is no internal pressure?

 

[Sawbux]

There is a section in Gaylord & Gaylord Structural Engineering Handbook. I have 1968 edition, don't know if it is in later editions. Chapter 26 is a section on chimneys and has a smaller section on concrete about 5 pages. It refers to ACI 505-54, which may be an earlier version of ACI 307.

The section on radial brick chimneys make reference to steel bands, with max distance of 15 ft. Says they are to counteract temperature stresses.

 

[SKJ25POL]

Sawbux (Structural),
Thank you very much. Can I ask a huge favor? Would it be possible scanning that 5 pages.
I would greatly appreciate it.

Thanks

 

[SlideRuleEra]

SKJ25POL - I have read about steel bands being used on the reinforced concrete shells with brick liners for reasons like Sawbux mentioned or as an attempt to repair poor or damaged concrete. However, all of our concrete shell chimneys use suspended steel or fiberglass liners (instead of brick) because of seismic loading. Our chimneys are in the 300' to 600' tall range; in that class, most were designed, built and maintained as "specialty" work by Pullman.

A suspended liner hangs from supports in the upper portion of the shell (supports located at about 80% of total chimney height) to allow thermal expansion of the liner mostly "down". The shell has to structurally support the weigh to liner and resist wind, seismic, etc. loading but is not intentionally subjected to internal pressure.

I have Gaylord & Gaylord's Third Edition (1990). The article on chimneys was moved to Section 30, but (in a quick look) I don't see reference to steel bands on the shell.

http://www.SlideRuleEra.net

 

[SKJ25POL]

Thank you SlideRuleEra (Structural).