Amount of Reinforcement

[FEM4Structures]

While determining the Rho= Rebar Area / b*d at any given section, do we include sum of both tensile and compressive steel areas to calculate Rho or the equation should only consider the reinforcement for either positive or negative moment while satisfying the section for Rho max and Rho min values?

I typically take sum of areas for both tensile and compressive rebar, just trying to think out loud.

Thanks,

FEM4Structures

 

[JAE]

Tension side only if you are designing singly reinforced beams (which is how most engineers do it). Rarely do we use doubly reinforced beam design methods unless we have to.

 

[FEM4Structures]

Case is for the walls with active earth pressure on one side. Have vertical rebar resisting negative moments and at others resisting positive moments following PCA Rectangular Tank Coefficients. All concrete checks are satisfied except Rho check if only to consider tensile steel at any given section.

Thanks,

FEM4Structures

 

[JAE]

ρ = As/bd

As is the area of tension steel. You don't add both the tension and compression steel together.

 

[JedClampett]

I'd put .0033 on both faces, in both directions.
But that's me.

 

[JLNJ]

You might ask for some help from someone in your office to explain this one to you.

Reinforcement ratio is an extrememly basic, yet crucial, concept.

 

[JStephen]

A couple of related threads (the first references the older second one)- evidently various engineers disagree about how some of these provisions should be applied- this in reference to slabs rather than walls-

http://www.eng-tips.com/viewthread.cfm?qid=225434

http://www.eng-tips.com/viewthread.cfm?qid=185223

 

[hokie66]

JStephen,

The threads you referenced were about the commingling of the code requirement for flexural reinforcement vs. direct tension shrinkage and temperature reinforcement. Shrinkage reinforcement is based on the gross area of the concrete, and can be placed throughout the section. It is clear in the current thread that the OP is asking about flexural reinforcement, and JAE has given the correct answer...the required amount of flexural reinforcement must be on the tension side.

 

[Splitrings]

It sounds like two load cases are being designed for; backfill with an empty tank and full tank without backfill. You need to look at both load cases separately to be certain your tension reinforcing meets code requirements.