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ACI 318-19 Beam Flexural Design

Required steel area As · Whitney stress block a = As·fy/(0.85f'c·b) · Net tensile strain εt check · φMn capacity · LRFD (φ-based)

Input Parameters

Concrete strength f'c psi

Rebar grade fy psi

Beam width b in.

Effective depth d in.

Factored moment Mu kip-ft

From load combinations per ASCE 7-22 §2.3.1

Design Results

β₁ §22.2.2.4.3—

Required Mn = Mu/φ kip-ft—

ρ (reinforcement ratio)—

As,min §9.6.1.2 in²—

As,required in²—

Stress block depth a in.—

Neutral axis c = a/β₁ in.—

εt (net tensile strain)—

φMn kip-ft—

DCR = Mu/φMn—

Bar selection guide:

Code References

§22.2Mn = As·fy·(d − a/2); a = As·fy/(0.85·f'c·b)

§22.2.2.4.3β₁ = 0.85 for f'c ≤ 4000 psi; reduces by 0.05 per 1000 psi above 4000; min 0.65

§9.6.1.2As,min = max(3√f'c·bw·d/fy, 200·bw·d/fy)

§9.3.3.1εt ≥ 0.005 for tension-controlled (φ = 0.90)

Table 21.2.1φ = 0.90 (tension-controlled); φ = 0.65 (compression-controlled)

Verifyf'c=4000, fy=60000, b=12, d=20, Mu=150 → As=1.78 in², a=2.62 in, εt=0.0164, φMn=150 kip-ft ✓

Engine: us-codes.js · Code pack: US-ACI318-19.v1 ·

ACI Shear Design → ASCE 7 Seismic →

Step-by-Step Solution

Preliminary calculation tool. Results are for preliminary sizing and cross-check only. Final design requires the full official text of ACI 318-19 and review by a licensed Professional Engineer (PE).