Foundation Design

Punching shear check — Isolated Footing & Raft Foundation · ACI 318-25 · Eurocode 2 · IS 456:2000

Input Parameters

ACI 318-25 · kN-m

Units:

Type:

Raft foundation: V_u entered directly. Drop panel and edge/corner columns supported.

Slab Properties

Slab thickness h [m]

Concrete f'c [MPa]

MPa

Clear cover c_v [m]

Bar ⌀ d_b [m]

d = h − c_v − d_b = 0.259 m

Column

Shape:

Type:

c₁ [m]

c₂ [m]

Design shear V_u [kN]

M_ux [kN·m] (opt.)

kN·m

M_uy [kN·m] (opt.)

kN·m

Shear Reinforcement (optional) Enable

Drop Panel (optional) Enable

📋

Enter values — results appear automatically.

Input Parameters

EN 1992-1-1 · kN-m

Units:

Type:

Raft foundation: V_Ed entered directly. Drop panel and edge/corner columns supported.

Slab Properties

Thickness h [m]

f_ck [MPa]

MPa

Cover c_v [m]

Bar ⌀ d_b [m]

d = h − c_v − d_b = 0.259 m

ρ_lx [%]

ρ_ly [%]

Column

Shape:

Type:

c₁ [m]

c₂ [m]

Design shear V_Ed [kN]

M_Ed,x [kN·m] (opt.)

kN·m

M_Ed,y [kN·m] (opt.)

kN·m

Shear Reinforcement (optional) Enable

Drop Panel (optional) Enable

📋

Enter values — results appear automatically.

Input Parameters

IS 456:2000 · kN-m

Units:

Type:

Raft foundation: V_u entered directly. Drop panel and edge/corner columns supported.

Slab Properties

Thickness h [mm]

f_ck [N/mm²]

N/mm²

Cover c_v [mm]

Bar ⌀ d_b [mm]

d = h − c_v − d_b = 259 mm

Column

Shape:

Type:

c₁ [mm]

c₂ [mm]

Design shear V_u [kN]

Shear Reinforcement (optional) Enable

Drop Panel (optional) Enable

📋

Enter values — results appear automatically.

Input Parameters

TS 500:2000 · kN-m

Foundation Type:

Slab / Footing Properties

Total Thickness h [mm]

f_ck [MPa]

Cover c_v [mm]

Bar ∅ d_b [mm]

d = h − c_v − d_b = 444 mm

Column (Rectangular, Interior)

c₁ [mm]

c₂ [mm]

Design Axial Force V_d [kN]

Footing Length L [m]

Footing Width B [m]

Net punching force: V_d,net=V_d−q_u·A_crit (TS 500 §12.2)

📋

Enter values — results appear automatically.

📚 Design Background & Code References

Theory↑ Top

Punching Shear in Foundations

A column punching through its foundation creates a truncated cone failure surface. The critical check is whether the shear stress on the control perimeter exceeds the concrete capacity.

Isolated Footing — Net Force

The upward soil reaction within the critical perimeter partially counteracts the column load. Only the net force outside the critical area contributes to punching:

Net Punching Force (ACI / IS 456)

V_u,net = P_u − q_u × A_crit
q_u = P_u / (B × L) A_crit = (c₁+d)(c₂+d) [interior rect.]

Net Punching Force (EC2 §6.4.4)

V_Ed,red = V_Ed − q_Ed × A_enc
A_enc = c₁c₂ + 4d(c₁+c₂) + 4πd² [interior rect. at 2d]

Raft Foundation

For mat/raft slabs, the punching check is equivalent to a flat slab. V_u/V_Ed is the column reaction from structural analysis. Drop panels may reduce the demand-to-capacity ratio by locally increasing depth.

ACI 318-25↑ Top

ACI 318-25 §13.4.4 Footing Two-Way Shear

Critical perimeter at d/2 — §22.6.4.1

b_o = 2(c₁+d) + 2(c₂+d) [interior rectangular]

Capacity — §22.6.5.2 (no λ_s for footings)

v_c = min(v_c1, v_c2, v_c3) · φ = 0.75
v_c1 = 0.17(1+2/β)λ√f'c · v_c2 = 0.083(α_sd/b_o+2)λ√f'c · v_c3 = 0.33λ√f'c
α_s: 40 interior, 30 edge, 20 corner

Eurocode 2↑ Top

EC2 §6.4.4 Column Bases

Control perimeter at 2d — §6.4.2

u₁ = 2(c₁+c₂) + 2π(2d) [interior rectangular, rounded corners]

Stocky footing enhancement — §6.4.4(2)

If a < 2d: v_Rd,c,enh = v_Rd,c × (2d/a)
a = min distance from column face to footing edge

Capacity — §6.4.2 (k factor applies to footings)

v_Rd,c = max(C_Rd,c·k·(100ρ_lf_ck)^1/3, v_min)
k = 1+√(200/d) ≤ 2.0 · C_Rd,c = 0.18/γ_c

IS 456:2000↑ Top

IS 456 Cl 34.2.4 Two-Way Shear in Footings

Net shear — Cl 34.2.4

V_net = P_u − q_u × (c₁+d)(c₂+d)
τ_v = V_net/(b_o·d) · b_o at d/2 from column face

Permissible shear — Cl 31.6.2

τ_c = 0.25√f_ck · k_s = min(0.5+β_c, 1.0)
Check: τ_v ≤ k_s·τ_c

TS 500:2000↑ Top

TS 500:2000 §12.2 Punching Shear

TS 500 §12.2 checks punching shear on the critical perimeter at a distance d/2 from the column face — similar in position to ACI 318 (also d/2) but different from EC2 (which uses 2d). The resistance is based on the concrete tensile strength only; no reinforcement contribution is credited unless special stirrups or headed studs are used.

Critical perimeter — §12.2 (rectangular column)

u₀ = 2·(c₁ + d) + 2·(c₂ + d)

c₁, c₂ = column dimensions. d = effective depth. The critical area A_crit = (c₁+d)·(c₂+d) is used to compute the net force for isolated footings.

Net punching force (isolated footing) — §12.2

q_u = V_d / (L·B) (net upward soil pressure)
V_d,net = V_d − q_u·A_crit

Punching shear stress and capacity — §12.2.1 & §12.2.2

τ_s = V_d,net / (u₀·d)
τ_c = 0.65·f_ctd (concrete capacity; f_ctd = 0.35√f_ck/1.5)
Section limit: τ_s ≤ 0.22·f_cd (§12.2.2 — crushing limit)
Design: τ_s ≤ τ_c (no reinforcement needed if satisfied)

If τ_s > τ_c but ≤ 0.22f_cd: shear reinforcement (stirrups or headed studs) is required — §12.2.3. If τ_s > 0.22f_cd: section must be enlarged.

Worked Example↑ Top

Example — ACI 318-25 Square Spread Footing: Punching Shear Check

Given: Square tied column 450×450 mm. Square footing L = B = 2.2 m, depth h = 500 mm. Concrete f'c = 25 MPa (λ = 1.0), cover 75 mm, main bar Ø16 → effective depth d = 500 − 75 − 8 = 417 mm. Factored column load P_u = 1,500 kN.

Critical perimeter b_o — ACI §22.6.4.1 (at d/2 from column face)
b_o = 4×(c + d) = 4×(450 + 417) = 4×867 = 3,468 mm
Net factored soil pressure q_u
Footing self-weight W_sw = 2.2×2.2×0.5×24 = 58.1 kN
q_u = (P_u−1.2×W_sw) / (B×L) = (1,500−69.7) / (2.2×2.2) = 1,430.3 / 4.84 = 295.5 kN/m²
Net shear force V_u at critical section
Area outside critical perimeter = B×L − (c+d)² = 4.84 − 0.867² = 4.84 − 0.751 = 3.089 m²
V_u = q_u × 3.089 = 295.5 × 3.089 = 912.8 kN
Punching shear stress v_u
v_u = V_u / (b_o×d) = 912,800 / (3,468×417) = 912,800 / 1,446,156 = 0.631 MPa
Concrete punching shear capacity v_c — ACI §22.6.5.2 (minimum of three)
β_c = long/short = 450/450 = 1.0 · α_s = 40 (interior column)
v_c1 = 0.33·λ·√f'c = 0.33×1.0×5.0 = 1.65 MPa
v_c2 = 0.083·(2 + 4/β_c)·λ·√f'c = 0.083×6.0×1.0×5.0 = 2.49 MPa
v_c3 = 0.083·(α_s·d/b_o + 2)·λ·√f'c = 0.083×(40×417/3,468 + 2)×5.0 = 0.083×6.81×5.0 = 2.82 MPa
Governing: v_c = min(1.65, 2.49, 2.82) = 1.65 MPa
φv_c = 0.75×1.65 = 1.24 MPa > v_u = 0.631 MPa ✓
DCR = v_u / φv_c = 0.631 / 1.24 = 0.51 < 1.0 ✓

Result: 2.2×2.2×0.5 m footing with f'c=25 MPa is adequate for punching shear. v_u = 0.63 MPa vs φv_c = 1.24 MPa (DCR = 0.51). Flexural reinforcement and one-way shear must also be verified separately.

References↑ Top

[1]
ACI 318-25 — §13.4.4 (Footing two-way shear), §22.6 (Two-way shear strength). ACI, 2025.
[2]
EN 1992-1-1:2004 — §6.4.4 (Column bases), §6.4.2 (Punching in slabs). CEN, Brussels.
[3]
IS 456:2000 — Cl 31.6 (Flat slab shear), Cl 34.2.4 (Footing two-way shear). BIS, New Delhi.
[4]
Wight & MacGregor — Reinforced Concrete, 7th Ed. Chapter 15. Pearson, 2016.
[5]
TS 500:2000 — Design and Construction Rules for Reinforced Concrete Structures. Turkish Standards Institution (TSE), Ankara. §12.2 (Punching shear: critical perimeter at d/2, τ_c=0.65f_ctd, section limit 0.22f_cd).

Disclaimer: For educational and preliminary design only. Verify with a licensed structural engineer.

Foundation Design

Input Parameters

Punching Design Report

Input Parameters

Punching Design Report

Input Parameters

Punching Design Report

Input Parameters

Punching Shear Report

📚 Design Background & Code References

Punching Shear in Foundations

Isolated Footing — Net Force

Raft Foundation

ACI 318-25 §13.4.4 Footing Two-Way Shear

EC2 §6.4.4 Column Bases

IS 456 Cl 34.2.4 Two-Way Shear in Footings

TS 500:2000 §12.2 Punching Shear

Example — ACI 318-25 Square Spread Footing: Punching Shear Check

Foundation Design

Input Parameters

Punching Design Report

Input Parameters

Punching Design Report

Input Parameters

Punching Design Report

Input Parameters

Punching Shear Report

📚 Design Background & Code References

Punching Shear in Foundations

Isolated Footing — Net Force

Raft Foundation

ACI 318-25 §13.4.4 Footing Two-Way Shear

EC2 §6.4.4 Column Bases

IS 456 Cl 34.2.4 Two-Way Shear in Footings

TS 500:2000 §12.2 Punching Shear

Example — ACI 318-25 Square Spread Footing: Punching Shear Check

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