Checks the punching of a flat slab at one interior, edge or corner column to SIA 262:2025: the control section, the slab rotation, the resistance without and with punching reinforcement, its detailing, and the integrity reinforcement against progressive collapse. Every step shows its formula and the clause it comes from.

What it checks

Control section at d_v/2 from the column, d_v = (d_x + d_y)/2, clauses 4.3.6.2.1 and 4.3.6.2.2, with the reductions of clause 4.3.6.2.3 for corners (Figure 23a), an opening (Figure 23d) and radial conduits (Figure 23e).
Design force: V_d = R_d − q_d · A, clause 4.3.6.2.6, and u = k_e · u_red, with k_e from clause 4.3.6.2.5 or equation (57).
Slab rotation ψ, clause 4.3.6.4.1, equation (60), at level 1, 2 or 3 (4.3.6.4.2). At level 2: r_s = 0.22 · l (4.3.6.4.4), b_s by equation (61), m_sd by equation (62) and m_Rd from the top bars (4.3.6.4.5).
Resistance without punching reinforcement: V_Rd,c = k_r · τ_cd · d_v · u, clause 4.3.6.3.1, equation (58), with k_r by equation (59) and k_g by equation (37).
Top bars: spacing ≤ min(1.2 · h ; 300 mm), clause 5.5.3.1, and the anchorage length l_a, clause 5.5.3.7.
Detailing of the punching reinforcement: at least two rows and s₀ < s₁ (5.5.3.8); s₁ and Ø_sw against Table 21; the spacing along the second row below 1.5 · d_v (5.5.3.9); c_v ≤ d_v/6 (5.5.3.11).
Resistance of the punching reinforcement: V_Rd,s = ΣA_sw · k_e · σ_sd · sin β, clause 4.3.6.5.4, equation (68), counting the rows between 0.35 · d_v and d_v, with σ_sd by equation (69).
Deformation capacity, equation (67), clause 4.3.6.5.3; first compression strut, V_Rd,max = min(2 · k_r ; 3.5) · τ_cd · d_v · u, clause 4.3.6.5.8, equation (70); outer control section with d_v,out = d_v − c_v, clause 4.3.6.5.10.
Integrity reinforcement: at least two bars each way (5.5.3.13), V_d,exc ≤ V_Rd,res, clause 4.3.6.7.2, equations (71) and (72), with k_β from Table 12; and at least one measure of clause 4.3.6.1.3.

What you enter and what you get

You enter the column (rectangular or circular, interior, edge or corner), the slab thickness, the cover and the top bars both ways, any opening or conduits, the concrete with D_max, the steel, the resistance factors, R_d and q_d, the moments transferred to the column, the level for ψ and the spans. Then the punching reinforcement in rows (links or studs, Ø_sw, n_sw, n_r, s₀, s₁, c_v) and the integrity bars with V_d,exc.

You get every step from d_v to the residual resistance, each check with its utilisation and clause, and a drawing. With the Basic plan, it prints as an A4 calculation note.

Assumptions and limits

Edge column: a free edge along y on the −x side; corner column: free edges on the −x and −y sides.
The simplified k_e values (0.9, 0.7, 0.65) apply to regular flat slabs on columns not designed for horizontal actions.
Level 3 takes r_s and m_sd from your own uncracked linear elastic plate analysis; the factor 1.5 of equation (60) becomes 1.2.
The reinforcement takes V_d − V_Rd,c at σ_sd (4.3.6.5.2), or all of V_d at f_yd (4.3.6.5.5).
Only integrity bars that cross the column count (4.3.6.7.3). Ductility class A gives no residual resistance.

Worked example

An interior 400 × 400 mm column under a 280 mm slab with Ø16 at 125 mm both ways at the top, f_ck = 30 N/mm², R_d = 650 kN, q_d = 16 kN/m², M_d,x = 40 kNm, spans of 7.5 m at level 2, four rows of 16 Ø14 links, and three Ø16 integrity bars each way with V_d,exc = 350 kN. These are the module's own results for its worked example, computed when this page was built.

Inputs
Input	Value	Ref.
Shape of the column	Rectangular
Column side along x a	400 mm
Column side along y b	400 mm
Position of the column	Interior column
Slab thickness h	280 mm
Cover to the top bars c	30 mm
Outer top layer	Bars along x
Top bars along x, diameter Ø_x	16 mm
Top bars along x, spacing s_x	125 mm
Top bars along y, diameter Ø_y	16 mm
Top bars along y, spacing s_y	125 mm
Opening near the column	None	§ 4.3.6.2.3
Embedded conduits near the column	None	§ 4.3.6.2.3
Characteristic compressive strength f_ck	30 N/mm²	§ 3.1.2.2.2
Largest aggregate size D_max	32 mm	§ 4.3.3.2.1
Characteristic yield strength of the top bars f_yk	500 N/mm²
Modulus of elasticity E_s	205000 N/mm²
Resistance factor for concrete γ_c	1.5	§ 2.4.2.6
Resistance factor for steel γ_s	1.15	§ 2.4.2.6
Design support force of the column R_d	650 kN
Design load on the slab inside the control section q_d	16 kN/m²	§ 4.3.6.2.6
Reduction for the moment transfer k_e	By the column position (4.3.6.2.5)	§ 4.3.6.2.4
Level of approximation	Level 2 — strip moment estimated	§ 4.3.6.4.2
Span in x l_x	7.5 m	§ 4.3.6.4.4
Span in y l_y	7.5 m	§ 4.3.6.4.4
Moment transferred to the column, x direction M_d,x	40 kNm
Moment transferred to the column, y direction M_d,y	0 kNm
Duration factor, for the bending resistance η_t	1.0 — both conditions of 4.2.1.3 met	§ 4.2.1.3
Punching reinforcement	Vertical links or studs	§ 4.3.6.5
Diameter of the elements Ø_sw	14 mm	§ 5.5.3.12
Number of elements in each row n_sw	16
Number of rows n_r	4	§ 5.5.3.8
Distance from the column face to the first row s₀	100 mm	§ 5.5.3.8
Radial spacing of the rows s₁	160 mm	§ 5.5.3.8
Distance from the bottom face to the lower anchorage c_v	35 mm	§ 5.5.3.11
Characteristic yield strength of the punching reinforcement f_yk,w	500 N/mm²	§ 4.3.6.5.4
Design of the punching reinforcement	With the concrete contribution (4.3.6.5.2)	§ 4.3.6.5.2
Mean tensile strength of the concrete f_ctm	2.9 N/mm²	§ 3.1.2.2.4
Integrity reinforcement	Straight bars at the bottom face	§ 4.3.6.7
Ductility class of the bars	B	Table 12
Bar diameter Ø_int	16 mm
Bars along x passing over the column n_x	3	§ 5.5.3.13
Bars along y passing over the column n_y	3	§ 5.5.3.13
Spacing of these bars s	100 mm
Cover to these bars at the bottom face c_int	30 mm
Design shear force, exceptional situation V_d,exc	350 kN	§ 4.3.6.7.4

Calculation: Effective depth
Step	Value	Ref.
Effective depth of the bars along xh − c − Ø_x/2	d_x = 242 mm
Effective depth of the bars along yh − c − Ø_x − Ø_y/2	d_y = 226 mm
Effective depth for punching(d_x + d_y)/2from the soffit, where the column supports the slab, to the mean level of the two top layers (Figure 21b)	d_v = 234 mm	§ 4.3.6.2.1

Calculation: Control section at d_v/2 from the column
Step	Value	Ref.
Length of the control section2·(a + b) + π·d_vclosed around the column	u₀ = 2,335 mm	§ 4.3.6.2.2
Left out: straight parts beyond 1.5·d_v from a corner1.5·d_v = 351 mmFigure 23a	Δu_23a = 0 mm	§ 4.3.6.2.3
Control section after the reductionsu₀ − the parts left out	u_red = 2,335 mm	§ 4.3.6.2.3
Area inside the control sectioncolumn included	A = 0.390 m²	§ 4.3.6.2.6
Centroid of the control sectioncentroid of the line u_0, from the column centre	x_G ; y_G = 0 ; 0 mm	§ 4.3.6.2.4

Calculation: Design punching force
Step	Value	Ref.
Load inside the control section	q_d·A = 6.2 kN	§ 4.3.6.2.6
Design punching forceR_d − q_d·A	V_d = 643.8 kN	§ 4.3.6.2.6

Calculation: Reduction for the moment transfer
Step	Value	Ref.
Reduction factorinterior columnregular flat slabs, columns not designed for horizontal actions	k_e = 0.90	§ 4.3.6.2.5
Effective control sectionk_e·u_red	u = 2,102 mm	§ 4.3.6.2.3

Calculation: Slab rotation ψ — level 2
Step	Value	Ref.
Distance to zero moment, x0.22·l_x	r_sx = 1.65 m	§ 4.3.6.4.4
Distance to zero moment, y0.22·l_y	r_sy = 1.65 m	§ 4.3.6.4.4
Design yield strength of the top barsf_yk/γ_s	f_yd = 434.8 N/mm²	§ 2.4.2.5 (4)
Design compressive strength of the concreteη_fc·η_t·f_ck/γ_c, η_fc = (40/f_ck)^(1/3) ≤ 1	f_cd = 20.0 N/mm²	§ 2.4.2.3 (2)
Width of the support strip1.5·√(r_sx·r_sy) ≤ l_min	b_s = 2.47 m	§ 4.3.6.4.6 (61)
Eccentricity components from the centroidM_d/R_d − centroid of the control section	e_u,x ; e_u,y = 62 ; 0 mm	§ 4.3.6.4.7
Mean moment in the strip, bars along xV_d·(1/8 + \|e_u,x\|/(2·b_s))	m_sd,x = 88.5 kNm/m	§ 4.3.6.4.7 (62)
Mean moment in the strip, bars along yV_d·(1/8 + \|e_u,y\|/(2·b_s))	m_sd,y = 80.5 kNm/m	§ 4.3.6.4.7 (62)
Bending resistance of the strip, bars along xa_s·f_yd·(d_x − 0.85·x/2), a_s = 1,608 mm²/mcompression block f_cd over 0.85·x, x = 41 mm	m_Rd,x = 157.0 kNm/m	§ 4.3.6.4.5
Bending resistance of the strip, bars along ya_s·f_yd·(d_y − 0.85·x/2), a_s = 1,608 mm²/mx = 41 mm	m_Rd,y = 145.8 kNm/m	§ 4.3.6.4.5
Slab rotation, x1.5·(r_sx/d)·(f_yd/E_s)·(m_sd,x/m_Rd,x)^1.5	ψ_x = 0.0095	§ 4.3.6.4.1 (60)
Slab rotation, y1.5·(r_sy/d)·(f_yd/E_s)·(m_sd,y/m_Rd,y)^1.5	ψ_y = 0.0092	§ 4.3.6.4.1 (60)
Slab rotation, governingmax(ψ_x ; ψ_y)d = d_v = 234 mm	ψ = 0.0095	§ 4.3.6.4.1

Calculation: Check — punching resistance without punching reinforcement
Step	Value	Ref.
Design shear stress limit0.3·√f_ck/γ_c	τ_cd = 1.095 N/mm²	§ 2.4.2.4 (3)
Aggregate factor48/(16 + D_max·min(1 ; (60/f_ck)²)) ≥ 1.2	k_g = 1.200	§ 4.3.3.2.1 (37)
Factor for size, rotation and aggregate1/(0.45 + 0.18·ψ·d·k_g) ≤ 2, d in mm	k_r = 1.076	§ 4.3.6.3.2 (59)
Punching resistancek_r·τ_cd·d_v·u	V_Rd,c = 579.5 kN	§ 4.3.6.3.1 (58)
Utilisation without the punching reinforcementfor information	V_d/V_Rd,c = 1.11	§ 4.3.6.3.1 (58)

Calculation: Detailing of the top bars
Step	Value	Ref.
Spacing of the top bars along xs_x/s_max	η = 0.417 · Pass42 % of the capacity used	§ 5.5.3.1
Spacing of the top bars along ys_y/s_max	η = 0.417 · Pass42 % of the capacity used	§ 5.5.3.1
Full anchorage of the top bars, from the column faced_v/2 + 2.5·d_v: 2.5·d_v beyond the control section, at most from the point of zero moment	l_a = 702 mm	§ 5.5.3.7

Calculation: Detailing of the punching reinforcement
Step	Value	Ref.
At least two rowsn_r	η = 0.500 · Pass50 % of the capacity used	§ 5.5.3.8
First row closer to the column than the row spacings₀/s₁	η = 0.625 · Pass63 % of the capacity used	§ 5.5.3.8
Radial spacing of the rowss₁/s_1,max	η = 0.912 · Pass91 % of the capacity used	Table 21
Diameter of the elementsØ_sw/Ø_sw,max	η = 0.778 · Pass78 % of the capacity used	Table 21
Spacing of the elements along the second rows_t/(1.5·d_v)	η = 0.608 · Pass61 % of the capacity used	§ 5.5.3.9
Lower anchorage of the elementsc_v ≤ d_v/6 = 39 mmmet	c_v = 35 mm	§ 5.5.3.11

Calculation: Check — resistance of the punching reinforcement
Step	Value	Ref.
Rows between 0.35·d_v and d_v from the column face82 mm to 234 mm	n_r,eff = 1	§ 4.3.6.5.4
Area of the counted elementsn_r,eff·n_sw·π·Ø_sw²/4	ΣA_sw = 2,463 mm²	§ 4.3.6.5.4
Design yield strength of the punching reinforcementf_yk,w/γ_s	f_yd,w = 434.8 N/mm²	§ 2.4.2.5 (4)
Stress in the punching reinforcement(E_s·ψ/6)·(1 + (f_ctm/f_yd,w)·(d/Ø_sw)) ≤ f_yd,w	σ_sd = 360.3 N/mm²	§ 4.3.6.5.4 (69)
Force for the punching reinforcementV_d − V_Rd,c	V_d,s = 64.2 kN	§ 4.3.6.5.2 (66)
Resistance of the punching reinforcementΣA_sw·k_e·σ_sd·sin β, β = 90°	V_Rd,s = 798.7 kN	§ 4.3.6.5.4 (68)
Resistance of the punching reinforcementV_d,s/V_Rd,s	η = 0.080 · Pass8 % of the capacity used	§ 4.3.6.5.4 (68)

Calculation: Check — deformation capacity
Step	Value	Ref.
Deformation capacity of the punching reinforcement(V_d/2)/(ΣA_sw·k_e·f_yd,w)	η = 0.334 · Pass33 % of the capacity used	§ 4.3.6.5.3 (67)

Calculation: Check — crushing of the first compression strut
Step	Value	Ref.
Upper limit of the punching resistancemin(2·k_r ; 3.5)·τ_cd·d_v·u	V_Rd,max = 1,159.1 kN	§ 4.3.6.5.8 (70)
First compression strut next to the columnV_d/V_Rd,max	η = 0.555 · Pass56 % of the capacity used	§ 4.3.6.5.8 (70)

Calculation: Check — outside the zone with punching reinforcement
Step	Value	Ref.
Distance from the column face to the last rows₀ + (n_r − 1)·s₁	r_out = 580 mm	§ 4.3.6.5.10
Effective depth outside the reinforced zoned_v − c_vFigure 26	d_v,out = 199 mm	§ 4.3.6.5.10
Length of the outer control sectionat r_out + d_v,out/2 from the column faceclosed	u_out,0 = 5,869 mm	§ 4.3.6.5.10
Largest gap between the outermost elementsalong the last row; each gap counts at most 3·d_v,out = 597 mmevery gap within 3·d_v,out (Figure 26)	s_t,out = 360 mm	§ 4.3.6.5.10
Outer control section after the reductionsu_out,0 − parts left out	u_out = 5,869 mm	§ 4.3.6.2.3
Design punching force at the outer sectionR_d − q_d·A_out, A_out = 2.698 m²	V_d,out = 606.8 kN	§ 4.3.6.2.6
Punching resistance outside the reinforced zonek_r·τ_cd·d_v,out·k_e·u_out	V_Rd,c,out = 1,238.8 kN	§ 4.3.6.5.10
Punching outside the reinforced zoneV_d,out/V_Rd,c,out	η = 0.490 · Pass49 % of the capacity used	§ 4.3.6.5.10

Calculation: Integrity reinforcement
Step	Value	Ref.
At least two bars in each directionn_min	η = 0.667 · Pass67 % of the capacity used	§ 5.5.3.13
Efficiency factorclass B, β = 0°	k_β = 0.37	Table 12
Distance between the top bars and the integrity barsd_v − c_int − Ø_int/2Figure 27a	d_int = 196 mm	§ 4.3.6.7.2
Groups of bars leaving the column2 along x, 2 along yeach bar leaves the column on two sides	n_g = 4	§ 4.3.6.7.3
Area of the bars leaving the columnΣ over the groups of n·π·Ø_int²/4	ΣA_s = 2,413 mm²	§ 4.3.6.7.2
Control section after punchingΣ(s_int + π/2·d_int), s_int = (n − 1)·sFigure 27c	u_int = 2,032 mm	§ 4.3.6.7.2 (72)
Residual resistanceΣ(A_s·f_yd·k_β) = 388.1 kN ≤ 1.7·τ_cd·d_int·u_int = 741.5 kN	V_Rd,res = 388.1 kN	§ 4.3.6.7.2 (71)
Residual resistance after punchingV_d,exc/V_Rd,res	η = 0.902 · Pass90 % of the capacity used	§ 4.3.6.7.2 (71)

Calculation: Check — measure against progressive collapse
Step	Value	Ref.
At least one measure of 4.3.6.1.3η	η = 0.334 · Pass33 % of the capacity used	§ 4.3.6.1.3

How this module is verified

Verified clause by clause against SIA 262:2025 and against independent calculations used on real projects, before release.

Questions

Why is the resistance without reinforcement shown if the links are counted?

For information: in the worked example V_d/V_Rd,c = 1.11, so the slab needs the links. With punching reinforcement, equations (68), (67), (70) and clause 4.3.6.5.10 replace equation (58).

Is the integrity reinforcement always needed?

Clause 4.3.6.1.3 asks for it, or for punching reinforcement meeting equation (67), at every support. The module reports the better of the two.

Which plan includes this module?

The Basic plan, with its calculation note.

Norm: SIA 262:2025 · Page updated: 29 October 2026

Punching of a flat slab at a column to SIA 262

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