About RC Beam & Column Design Calculator
The RC design calculator sizes the reinforcement for a rectangular reinforced concrete beam in flexure and shear per Eurocode 2, ACI 318, and AS 3600. It is used by structural engineers to find the required tensile steel area, check it against code minimum and maximum limits, and verify moment and shear capacity.
Enter the section width and depth, cover, span, concrete and rebar grades, and the ultimate design moment and shear. The tool returns the required steel area, a suggested bar arrangement, the moment and shear capacities, stirrup spacing where needed, and moment/shear utilization ratios that update as you type.
How It Works
- Compute the effective depth d from the overall depth, cover, and assumed link and main-bar diameters.
- For flexure, find the moment ratio K, the lever arm z (capped at 0.95d), and the required steel area As, then compare against the code minimum and maximum.
- For shear, compute the concrete shear capacity (VRd,c per EC2 or phi*Vc per ACI) and decide whether shear reinforcement is required.
- Where stirrups are needed, size the spacing for two-leg T10 links, suggest a bar arrangement, and report moment and shear utilization with a pass/fail verdict.
Worked Example
A 300 x 500 mm beam with 30 mm cover, C30/37 concrete (fck = 30 MPa) and B500B steel (fy = 500 MPa) under M_Ed = 200 kN.m gives d = 450 mm, K = 200e6 / (300 * 450^2 * 30) = 0.110 (below the 0.167 balanced limit), z = 401 mm, and As = 200e6 / (434.8 * 401) = 1147 mm2, suggesting 4T20 with a moment capacity of about 202 kN.m.
Formulas
- Moment ratio (EC2)
K = M / (b * d^2 * fck)- Lever arm (EC2)
z = min(d * (0.5 + sqrt(0.25 - K / 1.134)), 0.95 * d)- Required tensile steel (EC2)
As = M / (0.87 * fy * z)- Reinforcement ratio (ACI 318)
rho = (0.85 * fc / fy) * (1 - sqrt(1 - 2 * Rn / (0.85 * fc)))- Concrete shear capacity (ACI 318)
phi_Vc = 0.75 * (sqrt(fc) / 6) * b * d
Standards & References
- Eurocode 2 (EN 1992-1-1)
- ACI 318
- AS 3600
Frequently Asked Questions
Which design codes does the RC design calculator support?
It supports Eurocode 2 (EN 1992-1-1), ACI 318, and AS 3600. AS 3600 uses the Eurocode 2 flexure and shear engine, while ACI 318 applies its own strength-reduction (phi) factors and stress-block method.
How is the minimum reinforcement determined?
Under Eurocode 2 the minimum tensile steel is the greater of 0.26 * (fctm / fy) * b * d and 0.0013 * b * d; under ACI 318 it is the greater of (0.25 * sqrt(fc) / fy) and (1.4 / fy) times b * d. The tool reports both the required and minimum areas.
When does the beam need shear reinforcement?
When the design shear exceeds the concrete shear capacity (VRd,c in Eurocode 2 or phi*Vc in ACI 318), the tool flags that stirrups are required and sizes the spacing for two-leg T10 links based on the truss model.
What does the utilization percentage mean?
It is the ratio of the applied action to the design capacity, so moment utilization is M_Ed divided by the moment capacity. Values at or below 100% pass; the bar turns green below 70%, amber up to 90%, and red above that.