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### Minimum Reinforcement Steel Area Calculator

Civil Engineering and Design

Strength of Materials Basics and Equations | Mechanics of Materials

Minimum Reinforcement Steel Area per. ACI 318 Equations and Calculator

ACI 318 sets limits on the minimum and maximum areas of tension in steel.

The minimum area of tension steel is

*Eq. 1(a), SI
*

*A*

_{s,min}= f'_{c}^{0.5}· b_{w}· d / ( 4 · f_{y}) ≥ 1.4 · b_{w}· d / f_{y}*Eq. 1(b), US
*

*A*

_{s,min}= 3 · f'_{c}^{0.5}· b_{w}· d / ( f_{y}) ≥ 200 · b_{w}· d / f_{y}When the bending moment produces tension in the
flange of a statically determinate T-beam, the value of A_{s,min} calculated from Eq. 1 must be increased. For
this condition, ACI 318 Sec. 10.5.2 requires that the
minimum steel be taken as the smaller of what is calculated
from either Eq. 1 (with *b _{w}* set equal to the
width of the flange) or Eq. 2.

*Eq. 2(a), SI
*

*A*

_{s,min}= f'_{c}^{0.5}· b_{w}· d / ( 2 · f_{y})*Eq. 2(b), US
*

*A*

_{s,min}= 6 · f'_{c}^{0.5}· b_{w}· d / f_{y}Minimum steel provisions of *Eq. 1* and *Eq. 2* do
not have to be followed if the area of steel provided
exceeds the calculated amount required by at least
33% [ACI 318 Sec. 10.5.3].

Where:

* f ' _{c}* = Compressive strength of concrete, lbf/in

^{2}(MPa)

*b*= Width of web, ft, (m)

_{w}*d*= Beam effective depth (tension to steel centroid), ft, (m)

*f*Tension steel yield strength, lbf/in

_{y}=^{2}(MPa)

Reference

- ACI 318 Building Code Requirements for Structural Steel, paragraph 10.5 Minimum reinforcement of flexural members
- Civil Engineering Reference Manual, Fifteenth Edition, Michael R. Lindeburg, PE

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