Singly Reinforced Beam Designer

Rectangular Beam Inputs

Enter factored moment and material properties, then choose which dimensions are given. Specified b and d are kept exactly; only calculated dimensions are rounded. d is the effective depth to the steel centroid, not overall depth h.

Design mode Specified width b (mm) Specified effective depth d (mm) Mu (kN-m) f'c (MPa) fy (MPa) Bar diameter, db (mm) Cover / covering (mm) Cover is measured Aggregate diameter, dagg (mm) b ratio, d / b Spacing rule

Flexure Assumptions

The steel ceiling is written as a compression block a = k·β·d. The default k = 3/8 is the tension-controlled limit (c = 3d/8 puts the steel strain at exactly 0.005); a worksheet capping steel at 0.75ρ_b instead wants k = 0.75(600/(600+fy)). Set ρ/ρ_max = 1 for a problem that states ρ_act = ρ_max.

φ, strength reduction k in a = k·β·d at ρmax ρ used / ρmax Round calculated dimensions up to (mm)

Bar Distribution

When one layer does not fit, choose the number of layers and enter the bars per layer from bottom to top.

Number of layers Bars per layer, bottom to top Vertical clear spacing between layers (mm)

Solution

Waiting for input

Illustration

Run the design to show the beam section.

Horizontal clear spacing checks use max(25 mm, db), or max(25 mm, db, 4/3 dagg) when aggregate diameter is included.