# Beam Reinforcement Limits per ACI 318-19 with ideCAD

**How does ideCAD control beam reinforcement limits according to ACI 318-19?**

Longitudinal and Transverse reinforcement limits are controlled automatically.

**Notation**

* A_{cp }= *area enclosed by outside perimeter of concrete cross section, in.

^{2}

*total area of longitudinal reinforcement to resist torsion, in.*

**A**_{l }=^{2}

*minimum area of longitudinal reinforcement to resist torsion, in.*

**A**_{l,min }=^{2}

**A**_{s}**area of nonprestressed longitudinal tension reinforcement, in**

_{ }=^{2}

*minimum area of flexural reinforcement, in.*

**A**_{s},_{min }=^{2}

*area of one leg of a closed stirrup, hoop, or tie resisting torsion within spacing s, in.*

**A**_{t }=^{2}

*area of shear reinforcement within spacing s, in.*

**A**_{v }=^{2}

*minimum area of shear reinforcement within spacing s, in.*

**A**_{v},_{min }=^{2}

*web width or diameter of circular section, in.*

**b**_{w }=*distance from extreme compression fiber to centroid of longitudinal tension reinforcement, in.*

**d =***specified compressive strength of concrete, psi*

**f**_{c}^{' }_{ }_{ }=

**√f**_{c}‘*square root of specified compressive strength of concrete, psi*

^{ }_{ }=*specified yield strength for nonprestressed reinforcement, psi*

**f**_{y }=*specified yield strength of transverse reinforcement, psi*

**f**_{yt }_{ }=*overall thickness, height, or depth of member, in.*

**h =***center-to-center spacing transverse reinforcement, in*

**s =***cracking torsional moment, in.-lb*

**T**_{cr }_{ }=*threshold torsional moment, in.-lb*

**T**_{th }_{ }=*nominal torsional moment strength, in.-lb*

**T**_{n }_{ }=*factored torsional moment at section, in.-lb*

**T**_{u }_{ }=*nominal shear strength provided by concrete, lb*

**V**_{c }=*nominal shear strength, lb*

**V**_{n }=*nominal shear strength provided by shear reinforcement, lb*

**V**_{s }=*factored shear force at section, lb*

**V**_{u }=*strength reduction factor*

**ϕ =***= modification factor to reflect the reduced mechanical properties of lightweight concrete relative to normalweight concrete of the same compressive strength*

**λ***= ratio of*

**ρ**_{ }*to*

**A**_{s}

**bd****Minimum flexural reinforcement**

According to **ACI 9.6.1.2**, a minimum area of flexural reinforcement, * A_{s},_{min}* is equal to the greater of the following relations;

According to **ACI 9.6.1.3**, if * A_{s} *provided at every section is greater than one-third of

*calculated by analysis,*

**A**_{s}*need not be satisfied.*

**A**_{s},_{min}**Minimum shear reinforcement**

If shear reinforcement is required, minimum shear reinforcement area, * A_{v},_{min}*, should be considered in accordance with

**ACI Table 9.6.3.4.**

For nonprestressed beams, minimum shear reinforcement area, * A_{v},_{min}*, should be provided in all sections where

**V**_{u}**>**

*except for the cases given in*

**ϕλ √fc‘ b**_{w}d,**ACI Table 9.6.3.1.**For the cases given in

**ACI Table 9.6.3.1.,**

*, should be provided where*

**A**_{v,min}

**V**_{u}**>**

**ϕV**_{c}In other words, if **ϕλ√fc‘(b _{w}d) < V_{u} < [ V_{c}**

*the minimum shear reinforcement area,*

**+ 8√fc‘(b**_{w}d) ],*, is calculated given below.*

**A**_{v,min}

**Minimum torsional reinforcement**

If

torsional effects are ignored.**T**_{u }< ϕT_{th,}If

**ϕT**_{cr}**>****T**_{u}**≥**, only minimum torsional reinforcement needs to be provided given below;**ϕT**_{th}

Minimum transverse reinforcement **(A _{v} + 2A_{t})_{min} / s**

the minimum area of longitudinal reinforcement **A _{l,min }**

**Reinforcement Limits for Beams of Earthquake-Resistant Structures**

**Ordinary moment frames**

All the conditions and calculations described above are valid for beams of ordinary moment frames.

**Intermediate moment frames**

All the conditions and calculations described above are valid for beams of intermediate moment frames.

**Special moment frames**

All the conditions and calculations described above are valid for beams of special moment frames.

According to **ACI 18.6.3.1;** Longitudinal reinforcement should be satisfied the conditions given below;

Beams should have a minimum of two continuous bars at the top and bottom faces.

The reinforcement ratio

shall not exceed 0.025 for Grade 60 or S420 reinforcement and 0.02 for Grade 80 reinforcement.**ρ**