# Column Reinforcement Limits

Longitudinal and Transverse reinforcement limits are controlled automatically.

**A _{ch}**

**cross-sectional area of a member measured to the outside edges of transverse reinforcement, in.**

_{ }=^{2}

**A**_{g }**gross area of concrete section, in**

_{ }=^{2}

**A**_{sh}**total cross-sectional area of transverse reinforcement, including crossties, within spacing**

_{ }=*and perpendicular to dimension*

**s***, in.*

**b**_{c}^{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}

*cross-sectional dimension of member core measured to the outside edges of the transverse reinforcement composing area*

**b**_{c }=*, in.*

**A**_{sh}*width of compression face of member, in.*

**b**_{w }=*nominal diameter of bar, wire, or prestressing strand, in.*

**d**_{b }=*specified compressive strength of concrete, psi*

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

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

**f**_{yt }=*maximum center-to-center spacing of longitudinal bars laterally supported by corners of crossties or hoop legs around the perimeter of a column or wall boundary element, in.*

**h**_{x }=*concrete strength factor*

**k**_{f }=*confinement effectiveness factor*

**k**_{n }=*length, measured from joint face along axis of member, over which special transverse reinforcement must be provided, in.*

**l**_{o }=*unsupported length of column or wall, in.*

**l**_{u }=*length of entire wall, or length of wall segment or wall pier considered in direction of shear force, in.*

**l**_{w }=*number of longitudinal bars around the perimeter of a column core with rectilinear hoops that are laterally supported by the corner of hoops or by seismic hooks.*

**n**_{l }=

**P**_{u}**factored axial force; to be taken as positive for compression and negative for tension, lb**

_{ }=*center-to-center spacing of items, such as longitudinal reinforcement, transverse reinforcement, tendons, or anchors, in.*

**s**_{ }=*center-to-center spacing of transverse reinforcement within the length*

**s**_{o}_{ }=*, in.*

**l**_{o}*nominal shear strength provided by concrete, lb*

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

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

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

**ϕ =***= ratio of volume of spiral reinforcement to total volume of core confined by the spiral, measured out-to-out of spirals*

**ρ**_{s}The transverse reinforcement area is applied in a way to provide the equation * ϕV_{n} ≥ V_{u}*, which is described in Column Shear Design title for all columns.

**Minimum and maximum longitudinal reinforcement**

For nonprestressed columns,

minimum longitudinal reinforcement area is

**0.01****A**_{g}maximum longitudinal reinforcement area is

**0.08****A**_{g.}

**Minimum shear reinforcement**

A minimum area of shear reinforcement, * (A_{v})_{min}* should be provided in all sections where

*>*

**V**_{u}*.*

**0.5ϕV**_{c}According to **ACI 10.6.2.2; **If shear reinforcement is required, * A_{v,min}* is equal to the greater of the following relations;

**Columns of Earthquake Reistant Structures**

**Ordinary moment frames**

All of the reinforcement limits, described above are valid for columns of ordinary moment frames.

**Intermediate moment frames**

All of the reinforcement limits, described above are valid for columns of ordinary moment frames.

**Special moment frames**

For columns of special moment frames,

minimum longitudinal reinforcement area is

**0.01****A**_{g}maximum longitudinal reinforcement area is

**0.06****A**_{g.}

Over column clear height, longitudinal reinforcement shall be selected such that **1.25l _{d}≤l_{u}/2.**

Spacing of transverse reinforcement shall not exceed the least of conditions give below;

One-fourth of the minimum column dimension

For Grade 60 or S420,

of the smallest longitudinal bar**6d**_{b}For Grade 80,

of the smallest longitudinal bar**5d**_{b}, as calculated by: (The value of**s**_{o}shall not exceed 6 in. and need not be taken less than 4 in.)**s**_{o}

Amount of transverse reinforcement is in accordance with **ACI Table 18.7.5.4.**

The concrete strength factor * k_{f} *and confinement effectiveness factor

*are calculated as given below;*

**k**_{n}**Next Topic**