Concrete Beam Design Check (ACI)

civil

Checks a reinforced concrete beam for flexural capacity, shear capacity, and reinforcement limits per ACI 318-19. Looks up rebar areas from reference tables and applies phi factors for strength reduction.

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B In*

Beam width (bw) in inches. This is the web width for rectangular or T-beams. Typical: 10-18 in for beams, 12 in increments for columns.

H In*

Total beam depth (h) in inches. Effective depth (d) is computed as h minus cover, stirrup diameter, and half the main bar diameter unless d_in is specified directly. Typical: 12-36 in for beams. Rule of thumb: h ≈ L/12 to L/20.

D In

Effective depth (d) in inches, measured from compression face to centroid of tension steel. If omitted, calculated from h, cover, stirrup, and bar geometry.

Cover In

Clear concrete cover in inches from the tension face to the nearest stirrup surface. ACI 318-19 Table 20.6.1.3.1: 1.5 in. typical for beams not exposed to weather. If omitted, defaults to 1.5 in.

Fc Psi

Specified 28-day compressive strength of concrete (f'c) in psi. Common values: 3000, 4000, 5000, 6000 psi. Controls beta_1 and shear/flexural capacity. If omitted, defaults to 4000 psi.

Rebar Grade

ASTM rebar grade indicating yield strength in ksi. Available: '40' (40 ksi), '60' (60 ksi), '80' (80 ksi), '100' (100 ksi). Grade 60 is standard for most construction. If omitted, defaults to Grade 60.

Tension Bars

Tension reinforcement specification as 'NxBar' (e.g. '4#8' = four #8 bars, '6#5' = six #5 bars). Bar area is looked up from the rebar reference table. If omitted, defaults to '4#8'.

Stirrup Bar

Stirrup bar size (e.g. '#3', '#4'). Used to compute Vs (shear reinforcement contribution) and effective depth. #3 and #4 are most common for beams. If omitted, defaults to #3.

Stirrup Spacing In

Center-to-center spacing of stirrups in inches. If omitted, shear reinforcement contribution (Vs) is zero. ACI 318-19 max spacing: d/2 or 24 in. for typical beams.

Span Ft

Simply-supported beam span in feet. Used to compute Mu and Vu from the applied loading. Typical: 15-40 ft for concrete beams. Longer spans may need prestressing. If omitted, defaults to 20 ft.

Load Type

Loading configuration. 'uniform' = uniformly distributed load (wu). 'point_center' = single concentrated load at midspan (Pu). Determines moment and shear demand formulas. If omitted, defaults to uniform loading.

Wu Klf

Factored uniformly distributed load (wu) in kips per linear foot. This should be the LRFD factored load (e.g. 1.2D + 1.6L). Only required when load_type is 'uniform'.

Pu Kip

Factored concentrated load at midspan (Pu) in kips. This should be the LRFD factored load. Only required when load_type is 'point_center'.

Reference data

This calculator pulls live values from the following engineering reference tables in the database.

rebar

About this calculator

Concrete Beam Design Check (ACI) is part of the Engineering Database calculator suite. Each tool runs deterministic calculations against authoritative reference data and code-compliant methods, so results are reproducible and traceable to source standards.

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Reference data

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