structural / reinforced concrete

Reinforced concrete beam flexural-capacity calculator.

Estimate the nominal and factored bending resistance of a singly reinforced rectangular beam with a visible stress-block basis.

read the result

Make the internal force couple visible.

A rectangular beam flexural screen can be kept transparent by showing the tension force in the reinforcement and the compression-block depth that balances it. The lever arm then connects those forces to moment resistance.

Governing relationships

With tension steel assumed to reach its entered yield strength, T = Asfy. The equivalent block depth is a = T / (α1fc'b), and the neutral-axis depth is c = a / β1. The nominal resistance is Mn = T(d - a/2), followed by the entered resistance factor φ to obtain φMn.

What still needs a full design

  • Use the project code to select α1, β1, φ, concrete stress limits, and the applicable load combination.
  • Check minimum and maximum reinforcement, strain domain, compression steel, shear, torsion, anchorage, development, laps, cover, spacing, crack control, and serviceability separately.
  • Confirm the effective depth, material strengths, bar arrangement, and design moment from the project drawings and analysis model.