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Calcs.com
United States
ACI 318-19ACI 318-14

Concrete Beam

Beam reactions link to connected column and footing calculations automatically - change a load once and everything downstream updates. Design rectangular concrete beams to the current ACI 318-19 standard with customisable top and bottom reinforcement across unlimited spans; checks include flexural strength, shear capacity, and short- and long-term deflection. T-beam effective flange width per ACI 318-19 Cl 6.3.2.1 is supported.

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What it calculates

Design rectangular concrete beams to ACI 318-19 with customisable top and bottom reinforcement across unlimited spans. Checks include flexural strength, shear capacity, and short- and long-term deflection. Supports T-beams. Beam reactions link to connected column and footing calculations so changes propagate automatically.

Code standards

  • ACI 318-19

How it calculates

The Concrete Beam (ACI 318-19) calculator designs rectangular and T-beam sections per ACI 318-19 using LRFD. The same fundamental approach as the ACI 318-14 version applies, with updated shear provisions.

Flexural capacity

Positive and negative moment capacities φMn use the ACI rectangular stress block at εcu = 0.003. For T-beams, the effective flange width per ACI 318-19 Cl 6.3.2.1 engages the slab in compression for positive moments, increasing Mn relative to a rectangular section of the same web width.

Mn = A_s × fy × (d - a/2) for singly reinforced rectangular sections

φ = 0.90 for tension-controlled sections (net strain εt ≥ 0.005).

Shear capacity (ACI 318-19 update)

ACI 318-19 introduced a table-based Vc (Table 22.5.5.1) that depends on three parameters: longitudinal reinforcement ratio ρw, the ratio of factored moment to shear at the critical section (Mu/Vud), and axial load Nu/Ag. This replaces the simpler simplified formula of 318-14 and can give different (higher or lower) Vc depending on the beam's reinforcement and loading.

φVn = φ(Vc + Vs) where Vs = Av × fy × d / s, and φ = 0.75.

The lightweight concrete modification factor λ is applied to Vc per ACI 318-19 Table 19.2.4.2.

Deflection

Cracked-section effective moment of inertia Ie = Ig × (Mcr/Ma)³ + Icr × [1 - (Mcr/Ma)³] is used for all three deflection checks: short-term, long-term (with creep/shrinkage multiplier), and simplified DL+(LL or SL). Results are checked against user-defined L/n deflection limits.

Related calculators

Rectangular Concrete Column→Concrete Beam→Rectangular Concrete Column→

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Frequently asked questions

What design method and standard does this calculator follow?
Strength Design Method (LRFD) per ACI 318-19. Factored loads from ASCE 7 LRFD combinations are compared to reduced nominal capacities using ACI 318-19 strength reduction factors.
What are the key inputs?
Cross-section dimensions (bw and h, in inches), section type (rectangular or T-beam), flange width for T-beams, concrete compressive strength f'c (psi, minimum 2500 psi), concrete weight class (normalweight or lightweight), reinforcement yield strength fy (40-80 ksi), clear cover, positive and negative longitudinal reinforcement (bar size and count), stirrup size and spacing, span geometry, supports, and factored loads by type.
What checks does it perform?
Positive flexural capacity φMn+ ≥ Mu+, negative flexural capacity φMn- ≥ Mu-, shear capacity φVn ≥ Vu (ACI 318-19 table-based Vc plus stirrup Vs), short-term deflection, long-term deflection, and simplified DL+(LL or SL) deflection. Minimum cover and bar spacing requirements are also flagged.
How does ACI 318-19 shear differ from ACI 318-14?
ACI 318-19 introduced a more precise table-based Vc formula (Table 22.5.5.1) that is a function of the longitudinal reinforcement ratio, axial load, and the moment-to-shear ratio at the critical section. The 318-14 simplified Vc formula is more conservative for lightly reinforced sections; 318-19 can give higher or lower Vc depending on the section properties.
Does it support T-beams?
Yes - a T-beam option is available. When selected, the effective flange width is computed per ACI 318-19 Cl 6.3.2.1 based on span length and slab thickness, increasing the positive moment capacity by engaging the compression flange.
Does this calculator support load linking with column and footing calculations?
Yes - beam support reactions link directly to connected column and footing calculations in the same project. When any load or geometry changes, all linked calculations update automatically.

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