Reinforced Concrete Beam Flexure Design
Compute the required area of tension reinforcement (As) for a rectangular reinforced concrete beam to resist a factored moment Mu. Verifies the design moment capacity φMn against the demand, checks minimum and maximum reinforcement limits, and confirms tension-controlled behavior. Uses the Whitney rectangular stress block per ACI 318-19 Chapter 22.
What this calculates
Required steel area (As,req) from the quadratic moment equation, provided design moment capacity (φMn), reinforcement ratio (ρ), minimum reinforcement per ACI 318-19 Section 9.6.1, maximum reinforcement for tension-controlled sections (εt ≥ 0.005), and the depth of the compression block (a = As·fy / (0.85·f'c·b)).
Inputs
Maximum factored bending moment from load combinations
Width of the rectangular beam section
Distance from compression face to centroid of tension steel
Specified compressive strength of concrete
Yield strength of reinforcement (typically 60 ksi for Grade 60)
Outputs
Required area of tension reinforcement
Minimum reinforcement per ACI 318-19 §9.6.1
Depth of Whitney stress block
Design moment capacity with φ = 0.90
As / (b·d) — tensile reinforcement ratio
Net tensile strain in extreme tension steel at nominal strength
Methodology
The nominal moment capacity is Mn = As·fy·(d − a/2) where a = As·fy / (0.85·f'c·b) per ACI 318-19 Section 22.2. Required As is found by solving the quadratic Mu = φ·As·fy·(d − As·fy / (1.7·f'c·b)). Minimum reinforcement: As,min = max(3√f'c / fy, 200/fy)·b·d per Section 9.6.1.2. The section must be tension-controlled (εt ≥ 0.005) for φ = 0.90. Concrete strain at crushing εcu = 0.003.
Code References
Ready to use this template?
Clone it in one click, customize the inputs for your project, and export a professional PDF with your company branding.
Related templates
One-Way Slab Design
Design a one-way reinforced concrete slab for flexure, shear, and deflection control per ACI 318-19.
Concrete Column P-M Interaction Check
Check a rectangular RC column against axial load and moment demands using the P-M interaction diagram per ACI 318-19.
Spread Footing Bearing & Shear Design
Size a spread footing for soil bearing pressure and check one-way shear, two-way punching shear, and flexural reinforcement per ACI 318-19.