Primary Beam (ACI) Calculator • SI Units

Inputs — Geometry, Materials, Loads (SI)

Span L (m)

Beam width b (mm)

Overall depth h (mm)

Concrete f'c (MPa)

Steel fy (MPa)

Stirrup steel fyv (MPa)

Clear cover to bars (mm)

Assumed main bar dia (mm) 162022252832

Stirrup dia (mm) 81012

Dead load D (kN/m) (excluding self-weight)

Live load L (kN/m)

Include beam self-weight? Yes No

Moment case Simply supported (wL²/8) One end cont. (≈wL²/9) Interior span (≈wL²/12)

Concrete unit weight (kN/m³)

λ (lightweight factor)

φ_flex=0.90 • φ_shear=0.75

ACI flexure (singly reinforced): \(M_n = A_s f_y \left(d - \dfrac{a}{2}\right)\), \(a=\dfrac{A_s f_y}{0.85 f'_c b}\). ACI min steel (SI): \(A_{s,\min}=\max\!\left(0.25\dfrac{\sqrt{f'_c}}{f_y}bd,\; \dfrac{1.4}{f_y}bd\right)\). Shear (SI): \(V_c=0.17\lambda\sqrt{f'_c} b_w d\).

Results

Bar Selection Suggestions (top 8)

Shear & Stirrups

Step-by-step (calc trail)

Disclaimer: preliminary sizing only; verify per your project’s governing ACI edition, load paths, continuity, deflection, development, and detailing requirements.

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