Tensile Concrete Design

[GSEngineer]

I am evaluating an existing foundation that may or may not have tensile loads throughout the section. The section has both tension and compression steel. My thought on evaluating the tensile load was to determine if the tensile steel can carry the entire load. If it can carry the entire load, I was going to assume my tensile force was 0 and evaluate the section in pure bending.

Is this a proper method of evaluation? Or should I always assume the compression steel may carry some tensile load?

 

[ash060]

What it the foundation doing that it is in direct tension?

If the whole section is in tension than all the reinforcing present should carry some of the load.

And are there ties around the "compression" reinforcing? If there are not any ties than it cannot be considered to add compression capacity.

 

[SteelPE]

I'm not quite sure what you are talking about.

If I have a footing that has 2 mats of reinforcing and I have a stress reversal, I ignore what would be described as the compression reinforcing. This has to do with what asho60 says about compression reinforcing requiring ties (which I do not use in footings).

 

[GSEngineer]

This is a circular foundation for a cryogenic tank. It incurs hoop and radial stresses, some of which due to thermal changes. The thermal changes may cause combined bending and tensile stresses in the foundation.

Let's assume the section I am looking at has a positive moment and tensile load. There is rebar on the top and bottom of my section. The positive moment would cause the bottom rebar to take on tensile stress. Is it wise to allow the top rebar only to take on the applied tensile load?

In the real case, the tensile load might be carried by both the top and bottom rebar, causing the bottom rebar to not have enough capacity to carry the additional tensile load due to bending. Or is it safe to assume the top rebar will indeed carry the entirety of the applied tensile load?

I'm sorry I am not very clear in explaining this. Please let me know if you need more information. Thanks.