NZS 3101 Min/Max Reinforcement

Based on NZS 3101:2006 Clauses 7.6.1 (minimum), 7.6.2 (maximum), 9.3.2. Check reinforcement limits for beams and slabs.

Materials & Geometry

Concrete strength f'c (MPa)

Steel yield strength fy (MPa)

Web width bw (mm)

Total depth h (mm)

Effective cover c (mm)

Reinforcement

Tension steel area As (mm²)

Compression steel As' (mm²)

Tension-controlled section?

Results

Reinforcement limits check

Effective depth d-

Min As (Clause 7.6.1)-

Current As-

Min check-

Max As (Clause 7.6.2)-

Max check-

Current ρ-

Min ρ-

Max ρ-

Enter values and compute

Formulas

Minimum (Clause 7.6.1):
As,min = (0.25√f'c / fy) · bw · d
≥ 1.33·As,req or 1.4·bw·d/fy (for f'c < 30 MPa)

Maximum (Clause 7.6.2):
ρmax = 0.75 ρb (tension-controlled)
ρb = β1·0.85·f'c/fy · (600/(600+fy))
β1 = 0.85 - 0.05(f'c-30)/7 (≥ 0.65)

Notes

Minimum applies to beams and one-way slabs.
For two-way slabs, use 0.002bw·d minimum.
Maximum 75% of balance for tension-controlled.
Results are for quick checks; verify with full design.