> ## Documentation Index
> Fetch the complete documentation index at: https://calcs.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Design a Rectangular Concrete Column to ACI 318-14

> Design rectangular concrete columns to ACI 318-14. An earlier code edition, kept for existing projects.

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    <div className="calc-details-head"><span className="calc-card-icon"><Icon icon="calculator" size={20} color="#0076d6" /></span><p className="calc-details-name">Rectangular Concrete Column (ACI 318-14)</p><a className="calc-details-run" href="https://app.calcs.com/new/sheet/concreteColumnUSA">Run the calc</a></div>
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  Design rectangular concrete columns to ACI 318-14 with customizable longitudinal bar layout. Checks include pure axial capacity, X- and Y-axis P-M interaction, biaxial bending via the Bresler method, and moment magnification for slender columns. Axial reactions from beams above link automatically.
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<Note>
  This calculator uses an earlier code edition (ACI 318-14). It stays available for existing projects. For new designs, check the [Calculator Library](/docs/calculators/us) for the current edition.
</Note>

## Method & scope

| Property         | Detail                                                                              |
| ---------------- | ----------------------------------------------------------------------------------- |
| Design standards | ACI 318-14                                                                          |
| Regions          | United States                                                                       |
| What it checks   | Interaction diagram, Slenderness (non-sway frame), Biaxial bending (Bresler method) |

#### Calculation method

The Rectangular Concrete Column (ACI 318-14) calculator designs columns in non-sway frames per ACI 318-14. LRFD load combinations determine the governing factored axial load Pu and biaxial moments Mu,x and Mu,y.

##### Interaction diagram

The P-M interaction diagram is generated from the ACI rectangular stress block with ultimate concrete strain εcu = 0.003. At each point on the diagram, the neutral axis depth c is varied from zero (pure tension) to infinity (pure compression), and equilibrium between the concrete stress block and the reinforcement forces gives the corresponding Pn-Mn pair.

The strength reduction factor φ transitions from 0.65 (compression-controlled, εt ≤ εy) to 0.90 (tension-controlled, εt ≥ 0.005) per ACI 318-14 Section 21.2. Failure mode (compression-controlled or tension-controlled) is reported for each axis check.

##### Slenderness (non-sway frame)

For slender columns (**klu/r > 22** for non-sway), design moments are amplified via the ACI moment magnification method:

**Mc = δs × Mu** where **δs = Cm / (1, Pu / 0.75Pc)**

Cm = 0.6 + 0.4 × (M1/M2) is derived from the user-entered end moment ratio. Pc is the Euler critical load based on the effective EI.

##### Biaxial bending (Bresler method)

For combined biaxial bending and compression, the Bresler reciprocal load method is applied:

**1/φPn,biaxial = 1/φPnx + 1/φPny, 1/φPo**

where φPnx and φPny are uniaxial capacities at the acting moment magnitudes about each axis, and φPo is the pure axial capacity. The biaxial utilization **Pu / φPn,biaxial ≤ 1.0** must be satisfied for the column to pass.

## How to use it

<Steps>
  <Step title="Open the calculator">
    Open it from **Run calc** in the About this calculator panel above.
  </Step>

  <Step title="Enter your inputs">
    Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See [Checks, References, Conditions and Assumptions](/docs/running-calculations/checking-results/checks-references-conditions-assumptions).
  </Step>

  <Step title="Review the results and export">
    Check the utilization of each governing check in the summary, then export a PDF report. See [Views and Export](/docs/running-calculations/exporting-reports/views-and-export).
  </Step>
</Steps>

## Common questions

<AccordionGroup>
  <Accordion title="What design method and standard does this calculator follow?">
    Strength Design Method (LRFD) per ACI 318-14. LRFD load combinations from ASCE 7 determine the governing factored axial load Pu and biaxial moments Mu,x and Mu,y. ACI 318-14 Chapter 22 provisions govern the interaction diagram.
  </Accordion>

  <Accordion title="What are the key inputs?">
    Column cross-section dimensions (h and b, in inches), concrete strength f'c (psi), lightweight concrete factor λ, column height L (ft), effective length factors K for X and Y axes, end moment ratio Cm, longitudinal bar size and count (corner bars plus optional additional top/bottom and left/right bars), reinforcement yield strength fy (40-80 ksi), clear cover to ties, optional default load eccentricities, and axial plus biaxial moment loads by load type.
  </Accordion>

  <Accordion title="How is biaxial bending handled?">
    The Bresler reciprocal load method is used: 1/φPn,biaxial = 1/φPnx + 1/φPny, 1/φPo, where φPnx and φPny are the uniaxial capacities at the acting moments about each axis and φPo is the pure axial capacity. The biaxial utilization Pu / φPn,biaxial ≤ 1.0 must be satisfied.
  </Accordion>

  <Accordion title="How does slenderness affect the design?">
    Slenderness is assessed using KL and radius of gyration r. For slender columns in non-sway frames (the assumed condition), moment magnification is applied via the Cm/δ method: design moments are amplified by the magnification factor δ = Cm / (1, Pu/0.75Pc). The ratio of end moments M1/M2 (entered as Cm) and bracing condition are user inputs.
  </Accordion>

  <Accordion title="Does the calculator check shear?">
    Shear is flagged as a warning, it is not numerically checked. For columns carrying significant lateral loads, shear capacity should be verified separately per ACI 318-14 Chapter 22.
  </Accordion>

  <Accordion title="Does this calculator support load linking with beam calculations?">
    Yes, axial load reactions from connected beam calculations link directly to this column. When loads change in any upstream beam calculation, this column's axial demand updates automatically.
  </Accordion>
</AccordionGroup>

## Next steps

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  <Card title="Calculator Library" icon="list" href="/docs/calculators/us">
    Complete list of Calcs.com design calculators available for United States projects (AISC, ACI, NDS, ASCE 7, IBC, and related standards).
  </Card>

  <Card title="Design a Concrete Beam to ACI 318-14" icon="calculator" href="/docs/calculators/us/beams/concreteBeamRectangularUSA">
    Design rectangular concrete beams to ACI 318-14 across unlimited spans. An earlier code edition, kept for existing projects.
  </Card>

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    Design rectangular concrete beams and T-beams to ACI 318-19 across unlimited spans. Checks flexure, shear, and short- and long-term deflection.
  </Card>

  <Card title="Concrete Column Calculator to ACI 318-19 - Overview" icon="calculator" href="/docs/calculators/us/columns/concreteColumnUSAACI318-19">
    Design rectangular concrete columns to ACI 318-19. Checks axial capacity, P-M interaction, biaxial bending and slender column moment magnification.
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