Foundation Design
Punching shear check — Isolated Footing & Raft Foundation · ACI 318-25 · Eurocode 2 · IS 456:2000
Input Parameters
ACI 318-25 · kN-mRaft foundation: Vu entered directly. Drop panel and edge/corner columns supported.
Slab Properties
m
MPa
m
m
d = h − cv − db = 0.259 m
Column
m
m
Loading
kN
kN·m
kN·m
Shear Reinforcement (optional)
Drop Panel (optional)
📋
Enter values and click Calculate.Input Parameters
EN 1992-1-1 · kN-mRaft foundation: VEd entered directly. Drop panel and edge/corner columns supported.
Slab Properties
m
MPa
m
m
d = h − cv − db = 0.259 m
%
%
Column
m
m
Loading
kN
kN·m
kN·m
Shear Reinforcement (optional)
Drop Panel (optional)
📋
Enter values and click Calculate.Input Parameters
IS 456:2000 · kN-mRaft foundation: Vu entered directly. Drop panel and edge/corner columns supported.
Slab Properties
mm
N/mm²
mm
mm
d = h − cv − db = 259 mm
Column
mm
mm
Loading
kN
Shear Reinforcement (optional)
Drop Panel (optional)
📋
Enter values and click Calculate.📚 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)
Vu,net = Pu − qu × Acritqu = Pu / (B × L) Acrit = (c1+d)(c2+d) [interior rect.]
Net Punching Force (EC2 §6.4.4)
VEd,red = VEd − qEd × AencAenc = c1c2 + 4d(c1+c2) + 4πd² [interior rect. at 2d]
Raft Foundation
For mat/raft slabs, the punching check is equivalent to a flat slab. Vu/VEd 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
bo = 2(c1+d) + 2(c2+d) [interior rectangular]
Capacity — §22.6.5.2 (no λs for footings)
vc = min(vc1, vc2, vc3) · φ = 0.75vc1 = 0.17(1+2/β)λ√f'c · vc2 = 0.083(αsd/bo+2)λ√f'c · vc3 = 0.33λ√f'c
αs: 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: vRd,c,enh = vRd,c × (2d/a)a = min distance from column face to footing edge
Capacity — §6.4.2 (k factor applies to footings)
vRd,c = max(CRd,c·k·(100ρlfck)1/3, vmin)k = 1+√(200/d) ≤ 2.0 · CRd,c = 0.18/γc
IS 456:2000↑ Top
IS 456 Cl 34.2.4 Two-Way Shear in Footings
Net shear — Cl 34.2.4
Vnet = Pu − qu × (c1+d)(c2+d)τv = Vnet/(bo·d) · bo at d/2 from column face
Permissible shear — Cl 31.6.2
τc = 0.25√fck · ks = min(0.5+βc, 1.0)Check: τv ≤ ks·τc
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.
Disclaimer: For educational and preliminary design only. Verify with a licensed structural engineer.