NZS 3101 Concrete Section Shear Capacity

Based on NZS 3101:2006 Clauses 7.5 and 9.3.9, this tool estimates nominal shear capacity V_n. Adjust inputs to match your section and reinforcement.

Geometry & Materials

Concrete strength f'c (MPa)

Maximum aggregate size (mm)

Section width b_w (mm)

Section depth h (mm)

Effective cover c (mm)

Total longitudinal steel area A_s (mm²)

Shear Reinforcement

Stirrup diameter d_s (mm)

Number of legs n

Stirrup spacing s (mm)

Stirrup yield strength f_y (MPa)

Effective cover c is taken to the longitudinal steel centroid, so d_v = h - c.

Results

Nominal shear capacity V_n

Effective depth d_v -

Effective shear area A_cv -

Concrete contribution V_c -

Shear reinforcement V_s -

Nominal shear capacity V_n -

v_n ≤ v_max

Shear stress v_n -

Max shear stress v_max -

k_a / k_d -

v_b / v_c -

Formula Summary

V_n = V_c + V_s
V_c = v_c · A_cv
v_c = k_a k_d v_b
v_b = min[(0.07 + 10ρ_w)√f'c , 0.2√f'c], and ≥ 0.08√f'c
V_s = A_v f_y d_v / s
A_v = n · (π d_s²/4)

Notes

This page assumes normal-weight concrete and uses v_max = min(0.2 f'c, 10 MPa). k_a is linearly interpolated for aggregate sizes 10–19 mm. For d_v > 400 mm, k_d = (400/d_v)^0.25 with 0.9 ≤ k_d ≤ 1.0. For d_v ≤ 200 mm, v_c is the larger of 0.17k_a√f'c and k_a v_b. Results are for quick checks; confirm with the full code and design conditions.