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Minimum reinforcement ratio of thick concrete members

Minimum reinforcement ratio of thick concrete members

Minimum reinforcement ratio of thick concrete members

(OP)
Hi there!
I need to design a thick concrete foundation of a tower crane. It needs to be 1.70 m thick to provide safety factor of overturning moments. Internal forces in the foundation section are not large, that's why even mimimum reinforcement ratio is overdesign. Is there any design rule for this situation? American or Europan codes are possible.

RE: Minimum reinforcement ratio of thick concrete members

You could maybe treat it as unreinforced and design it accordingly, although the rules probably vary a lot depending on what code you’re looking at.

But minimum reinforcement, even in such a thick section, should normally be a pretty small quantity. Considering the cost of pouring a 1.7 m thick footing, erecting by a crane, etc etc, the cost of the reinforcement would be pennies.

RE: Minimum reinforcement ratio of thick concrete members

(OP)
Thank you for your comment. The crane supplier made a proposal for the foundation design and the reinforcements in this proposal are much less than the minimum reinforcement. if this is not based on a design code i will implement minimal reinforcement. The crane vendor cannot be reached. And pennies are calculated in the construction industry.

RE: Minimum reinforcement ratio of thick concrete members

Note that in ACI, minimum tension and shrinkage reinforcement is only calculated based on the top and bottom 12" (300mm) of the section. You can ignore the middle 1.1m. I'd want to say that in some cases, only the top really needs the T&S steel, but I'm not sure if that's in the code anywhere.

(This assumes that the section can be designed as unreinforced for flexure and shear internal forces).

----
just call me Lo.

RE: Minimum reinforcement ratio of thick concrete members

The ACI 318-14 minimum flexural reinforcement for foundations is as follows and is applied on each face (top and bottom) of the foundation mat.


RE: Minimum reinforcement ratio of thick concrete members

What's the downside if it cracks? How large is the foundation? 20'x20' or 200'x200'?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Minimum reinforcement ratio of thick concrete members

You mentioned that “pennies are calculated in the construction industry.” Did you have experience with previous crane tower work where someone balked at the costs? It seems something as critical to the success of the project would be one of those expensive costs that all parties would be willing to live with.

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