## ACI minimum reinforcement at zero moment

## ACI minimum reinforcement at zero moment

(OP)

Hi all,

I was designing a beam using RSA when w faced a huge minimum area of reinforcement at zero moment (attached screen shot)

I didn't find any clue in ACI mentioning this huge increase of As,min .

the beam dimension is 90x30 cm. Can someone clarify me why Im getting this issue?

I was designing a beam using RSA when w faced a huge minimum area of reinforcement at zero moment (attached screen shot)

I didn't find any clue in ACI mentioning this huge increase of As,min .

the beam dimension is 90x30 cm. Can someone clarify me why Im getting this issue?

## RE: ACI minimum reinforcement at zero moment

## RE: ACI minimum reinforcement at zero moment

section 10.5.3 is under minimum reinforcement of flexural member. In my case, due to axial load and zero moment, the minimum area of reinforcement is taken the same as the column (1% x section) .

my question is:

1-this section can be used in my case?

2-I am using RSA for my analysis, (http://forums.autodesk.com/t5/robot-structural-ana...)

kindly check the forum and especially the sentence "If you consider the axial force as small enough to be neglected just exclude it from the analysis and run reinforcement design for pure bending. "

what part of ACI-318 Talks about this statement?

I really appreciate your help because no one gave me a clear answer about this issue:s

## RE: ACI minimum reinforcement at zero moment

## RE: ACI minimum reinforcement at zero moment

"It is due to applying Amin provisions of ACI for elements under pure tension (it is in the location where bending moment is zero and tension force exists). If you consider the axial force as small enough to be neglected just exclude it from the analysis and run reinforcement design for pure bending. "

My main question is there any ACI provision that we can use to neglect axial load?

ACI318-08 item#10.5.3 can be used in this case?

note: load applied (Self weight -Z direction , LL +Z direction)

## RE: ACI minimum reinforcement at zero moment

ACI 318-14, in reference to the effects of combined axial and moment, says:

I would suggest that there would be need for reinforcement top and bottom in sections subject to significant axial.

## RE: ACI minimum reinforcement at zero moment

the member resist only the loads mentioned before with a one end fixed and other pinned.

as for ACI318-14 provisions the Word "Significant" is defined by who? by what formula? what is the limit of axial load in order to consider it as significant or not?

## RE: ACI minimum reinforcement at zero moment

Obviously, "significant" would not be used in the code, only the commentary.

## RE: ACI minimum reinforcement at zero moment

## RE: ACI minimum reinforcement at zero moment