Checks one rectangular reinforced concrete slab panel on its four edges, each free, simply supported or fixed, to SIA 262:2025: bending and torsion, shear along the supported edges, detailing, bar stresses, crack width and deflection, and chooses the bars zone by zone. Every step shows its formula and the clause it comes from.

What it checks

Bending resistance of the four layers, m_xRd, m_yRd, m′_xRd and m′_yRd, clause 4.2.1.5, and the ductility x/d ≤ 0.5 · 435/f_yd (4.1.4.2.6).
Minimum reinforcement and detailing: m_cr ≤ m_Rd for each layer (4.3.1.2), the spacing (5.5.3.1) and the weaker direction at least 20 % of the main one (5.5.3.2).
Bending and torsion, clause 4.3.2.6, equations (34a) to (34d): m_xd + |m_xyd| ≤ m_xRd and its three counterparts, at every point of the plate.
Shear at each supported edge, without stirrups: v_d ≤ v_Rd = k_d · τ_cd · d_v, 4.3.3.2.1, equation (35), at d_v/2 from the support, with k_d from equation (36) and ε_v from 4.3.3.2.2, equation (39).
Serviceability: each layer cracked or not against m_cr, the bar stress σ_s against Table 17, the crack width to EN 1992-1-1 §7.3.4, and the long-term deflection w_cφ = w_c · (1 + φ), 4.4.3.2.4, equation (103), against w_adm.
Bars chosen zone by zone: the lightest option of your list that meets every selected criterion, per zone and per layer.

What you enter and what you get

You enter the spans l_x and l_y, the support of each edge, and on a plan any openings and concentrated loads (Q_d, Q and the loaded area), placed by clicking. Then the section and its bars, the materials, the resistance factors, q_d and the service load q. The creep coefficient φ is entered or computed.

You get every check with a pass or fail and where it governs, and the zones coloured by bar option. With the Basic plan, it prints as an A4 calculation note.

Assumptions and limits

Moments come from an uncracked linear elastic plate with the corners held down (4.1.4.1): a statically admissible field, on the safe side. For a uniformly loaded panel without openings or concentrated loads, yield lines (4.1.4.2.3) are offered; they need ductile reinforcement.
v_d is the edge reaction of the plate, averaged over 2 · d each side of its maximum (4.3.3.1.5).
A concentrated load is spread over its loaded area enlarged by h. Punching is not checked here.
The top bars are taken as present wherever they are needed: extend them far enough into the panel.
φ follows equation (13), each factor from EN 1992-1-1 Annex B, which agrees with SIA 262 Table 4 and Figure 2. k₃ and k₄ are nationally determined; you enter them.
Steel masses exclude laps and anchorages.

Worked example

A panel of 6.0 × 4.5 m, simply supported on the left and bottom edges and fixed or continuous on the other two, h = 200 mm, Ø10 bars at 150 to 200 mm, f_ck = 30 N/mm², q_d = 14 kN/m², one opening of 1.0 × 0.6 m, one concentrated load of 45 kN (30 kN in service) on 0.3 × 0.3 m, a quasi-permanent load of 8 kN/m² and w_adm = 13 mm. These are the module's own results for its worked example, computed when this page was built.

Inputs
Input	Value	Ref.
Span in x l_x	6.0 m
Span in y l_y	4.5 m
Left edge (x = 0)	Simply supported
Right edge (x = l_x)	Fixed or continuous
Bottom edge (y = 0)	Simply supported
Top edge (y = l_y)	Fixed or continuous
Plan of the panel	{"o":0.8,3.2,1.0,0.6,"q":4.0,2.0,45,30,0.3,0.3}
Slab thickness h	200 mm
Cover to the bottom bars c	30 mm
Outer bottom layer	Bars along y
Diameter Ø_x	10 mm
Spacing s_x	200 mm
Diameter Ø_y	10 mm
Spacing s_y	150 mm
Top reinforcement	Bars along x and y
Cover to the top bars c′	30 mm
Outer top layer	Bars along x
Diameter along x Ø′_x	10 mm
Spacing along x s′_x	150 mm
Diameter along y Ø′_y	10 mm
Spacing along y s′_y	150 mm
Characteristic compressive strength f_ck	30 N/mm²	§ 3.1.2.2.2
Mean tensile strength f_ctm	2.9 N/mm²	§ 3.1.2.2.4
Modulus of elasticity E_cm	33600 N/mm²	§ 3.1.2.3.3
Poisson's ratio ν	0.2	§ 3.1.2.3.5
Largest aggregate size D_max	32 mm	§ 4.3.3.2.1
Characteristic yield strength 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
Duration factor η_t	1.0 — both conditions of 4.2.1.3 met	§ 4.2.1.3
Design load, uniform q_d	14 kN/m²
Method for the bending moments	Linear elastic plate (4.1.4.1)	§ 4.1.4
Tensile strength for cracking	Mean tensile strength (4.4.1.3)	§ 4.4.1.3
Requirement level	Normal	§ 4.4.2.2.3
Uniform load in the load case q	8 kN/m²
Load case	Quasi-permanent	Table 17
Creep coefficient φ	Computed from the concrete, the exposure and the ages	§ 3.1.2.6.2
Mean compressive strength f_cm	38 N/mm²	§ 3.1.2.2.3
Relative humidity of the surroundings RH	50 %
Faces drying out	Both faces
Cement	Normal hardening (class N)
Age of the concrete at loading t₀	28 days
Age considered t	25000 days
Admissible deflection (optional) w_adm	13 mm
Bond of the bars k₁	High-bond bars (0.8)	EN 1992-1-1 §7.3.4(3)
Duration of the load k_t	Long-term or repeated (0.4)	EN 1992-1-1 §7.3.4(2)
Bar options	[[8,200],[10,200],[10,150],[12,150],[14,150],[16,150],[16,100]]
Size of a design zone a_z	0.75 m
Bending resistance, eq. (34)	Yes	§ 4.3.2.6
Minimum reinforcement and detailing	Yes	§ 4.3.1.2
Bar stress in service, Table 17	Yes	Table 17
Crack width in service	No	EN 1992-1-1 §7.3.4
No cracking in service	No	§ 4.4.1.3
Deflection limit	Yes	§ 4.4.3.2
Admissible deflection w_adm	13 mm	§ 4.4.3.1.1

Calculation: Reinforcement per metre of width
Step	Value	Ref.
Bottom bars along xπ·Ø²/4·1000/sØ10 at 200 mm	a_s,bx = 393 mm²/m
Effective depth, bottom bars along xh − c − (bars below) − Ø/2	d_bx = 155 mm
Bottom bars along yπ·Ø²/4·1000/sØ10 at 150 mm	a_s,by = 524 mm²/m
Effective depth, bottom bars along yh − c − (bars below) − Ø/2	d_by = 165 mm
Top bars along xπ·Ø²/4·1000/sØ10 at 150 mm	a_s,tx = 524 mm²/m
Effective depth, top bars along xh − c′ − (bars above) − Ø/2	d_tx = 165 mm
Top bars along yπ·Ø²/4·1000/sØ10 at 150 mm	a_s,ty = 524 mm²/m
Effective depth, top bars along yh − c′ − (bars above) − Ø/2	d_ty = 155 mm

Calculation: Design strengths
Step	Value	Ref.
Factor for the brittleness of strong concrete(40/f_ck)^(1/3) ≤ 1	η_fc = 1.000	§ 4.2.1.2 (26)
Design compressive strength of the concreteη_fc·η_t·f_ck/γ_c	f_cd = 20.0 N/mm²	§ 2.4.2.3 (2)
Design shear stress limit0.3·√f_ck/γ_c	τ_cd = 1.10 N/mm²	§ 2.4.2.4 (3)
Design yield strength of the steelf_yk/γ_s	f_yd = 434.8 N/mm²	§ 2.4.2.5 (4)

Calculation: Bending resistances per metre
Step	Value	Ref.
Bottom bars along xa_s·f_yd·(d − 0.85·x/2), 0.85·x = a_s·f_yd/f_cdx/d = 0.065	m_xRd = 25.7 kNm/m	§ 4.2.1.5
Bottom bars along ya_s·f_yd·(d − 0.85·x/2), 0.85·x = a_s·f_yd/f_cdx/d = 0.081	m_yRd = 36.3 kNm/m	§ 4.2.1.5
Top bars along xa_s·f_yd·(d − 0.85·x/2), 0.85·x = a_s·f_yd/f_cdx/d = 0.081; tension on top	m′_xRd = 36.3 kNm/m	§ 4.2.1.5
Top bars along ya_s·f_yd·(d − 0.85·x/2), 0.85·x = a_s·f_yd/f_cdx/d = 0.086; tension on top	m′_yRd = 34.0 kNm/m	§ 4.2.1.5

Calculation: Check 1 — ductility of the compression zone
Step	Value	Ref.
Deepest compression zone (top bars along y)(x/d)/(0.5·435/f_yd)	η = 0.173 · Pass17 % of the capacity used	§ 4.1.4.2.6

Calculation: Check 2 — minimum reinforcement: resistance above the cracking moment
Step	Value	Ref.
Cracking moment per metrek_t·f_ctm·h²/6, k_t = 1/(1 + 0.5·h/3) (h in m)	m_cr = 18.7 kNm/m	§ 4.4.1.3 (99)
Bottom bars along xm_cr/m_xRd	η = 0.727 · Pass73 % of the capacity used	§ 4.3.1.2
Bottom bars along ym_cr/m_yRd	η = 0.516 · Pass52 % of the capacity used	§ 4.3.1.2
Top bars along xm_cr/m′_xRd	η = 0.516 · Pass52 % of the capacity used	§ 4.3.1.2
Top bars along ym_cr/m′_yRd	η = 0.550 · Pass55 % of the capacity used	§ 4.3.1.2

Calculation: Check 3 — spacing and transverse reinforcement
Step	Value	Ref.
Spacing, bottom bars along xs/s_max	η = 0.833 · Pass83 % of the capacity used	§ 5.5.3.1
Spacing, bottom bars along ys/s_max	η = 0.625 · Pass63 % of the capacity used	§ 5.5.3.1
Spacing, top bars along xs/s_max	η = 0.625 · Pass63 % of the capacity used	§ 5.5.3.1
Spacing, top bars along ys/s_max	η = 0.625 · Pass63 % of the capacity used	§ 5.5.3.1
Bottom: weaker direction against 20 % of the main one0.2·a_s,main/a_s,tr	η = 0.267 · Pass27 % of the capacity used	§ 5.5.3.2
Top: weaker direction against 20 % of the main one0.2·a_s,main/a_s,tr	η = 0.200 · Pass20 % of the capacity used	§ 5.5.3.2

Calculation: Check 4 — bending and torsion, elastic plate: eq. (34)
Step	Value	Ref.
Finite element meshuncracked plate, ν = 0.20, corners held down	20 × 16 plate elements
Positive moments in x — bottom bars along xm_xd+\|m_xyd\|/m_xRd	η = 0.644 · Pass64 % of the capacity used	§ 4.3.2.6 (34a)
Positive moments in y — bottom bars along ym_yd+\|m_xyd\|/m_yRd	η = 0.662 · Pass66 % of the capacity used	§ 4.3.2.6 (34b)
Negative moments in x — top bars along x−m_xd+\|m_xyd\|/m′_xRd	η = 0.845 · Pass84 % of the capacity used	§ 4.3.2.6 (34c)
Negative moments in y — top bars along y−m_yd+\|m_xyd\|/m′_yRd	η = 0.945 · Pass95 % of the capacity used	§ 4.3.2.6 (34d)

Calculation: Check 5 — shear along the supported edges, slab without stirrups
Step	Value	Ref.
Aggregate factor48/(16 + D_max·min(1 ; (60/f_ck)²)) ≥ 1.2	k_g = 1.200	§ 4.3.3.2.1 (37)

Calculation: Shear at the left edge
Step	Value	Ref.
Design shear force per metreedge reaction of the elastic plate, averaged over 2·d each side of its maximumpeak 25.5 kN/m at 1.75 m along the edge	v_d = 25.3 kN/m	§ 4.3.3.1.5
Effective depth for shearbottom bars perpendicular to the edge	d_v = 155 mm
Strain for the shear resistancef_yd/E_s·m_d/m_Rd, m_d ≈ v_d·d/2 at the control section	ε_v = 0.161 ‰	§ 4.3.3.2.2 (39)
Coefficient1/(1 + ε_v·d·k_g)	k_d = 0.971	§ 4.3.3.2.1 (36)
Shear at the left edgev_d/v_Rd	η = 0.153 · Pass15 % of the capacity used	§ 4.3.3.2.1 (35)

Calculation: Shear at the right edge
Step	Value	Ref.
Design shear force per metreedge reaction of the elastic plate, averaged over 2·d each side of its maximumpeak 47.3 kN/m at 1.75 m along the edge	v_d = 46.7 kN/m	§ 4.3.3.1.5
Effective depth for sheartop bars perpendicular to the edge	d_v = 165 mm
Strain for the shear resistancef_yd/E_s·m_d/m_Rd, m_d = support moment	ε_v = 1.791 ‰	§ 4.3.3.2.2 (39)
Coefficient1/(1 + ε_v·d·k_g)	k_d = 0.738	§ 4.3.3.2.1 (36)
Shear at the right edgev_d/v_Rd	η = 0.350 · Pass35 % of the capacity used	§ 4.3.3.2.1 (35)

Calculation: Shear at the bottom edge
Step	Value	Ref.
Design shear force per metreedge reaction of the elastic plate, averaged over 2·d each side of its maximumpeak 28.7 kN/m at 3.10 m along the edge	v_d = 28.5 kN/m	§ 4.3.3.1.5
Effective depth for shearbottom bars perpendicular to the edge	d_v = 165 mm
Strain for the shear resistancef_yd/E_s·m_d/m_Rd, m_d ≈ v_d·d/2 at the control section	ε_v = 0.138 ‰	§ 4.3.3.2.2 (39)
Coefficient1/(1 + ε_v·d·k_g)	k_d = 0.973	§ 4.3.3.2.1 (36)
Shear at the bottom edgev_d/v_Rd	η = 0.162 · Pass16 % of the capacity used	§ 4.3.3.2.1 (35)

Calculation: Shear at the top edge
Step	Value	Ref.
Design shear force per metreedge reaction of the elastic plate, averaged over 2·d each side of its maximumpeak 43.6 kN/m at 3.10 m along the edge	v_d = 43.3 kN/m	§ 4.3.3.1.5
Effective depth for sheartop bars perpendicular to the edge	d_v = 155 mm
Strain for the shear resistancef_yd/E_s·m_d/m_Rd, m_d = support moment	ε_v = 2.005 ‰	§ 4.3.3.2.2 (39)
Coefficient1/(1 + ε_v·d·k_g)	k_d = 0.728	§ 4.3.3.2.1 (36)
Shear at the top edgev_d/v_Rd	η = 0.350 · Pass35 % of the capacity used	§ 4.3.3.2.1 (35)

Calculation: Creep coefficient
Step	Value	Ref.
Notional size2·A_c/uboth faces dry: h₀ = h	h₀ = 200 mm
Humidity and size factor[1 + (1 − RH/100)/(0.1·∛h₀)·α₁]·α₂SIA 262 Figure 2	φ_RH = 1.778	EN 1992-1-1 (B.3)
Strength factor16.8/√f_cmSIA 262 Table 4	β_fc = 2.725	EN 1992-1-1 (B.4)
Age at loading, adjusted for the cementt₀·(9/(2 + t₀^1.2) + 1)^α, α = 0at 20 °C	t_0,eff = 28.0 days	EN 1992-1-1 (B.9)
Age-at-loading factor1/(0.1 + t₀^0.2)SIA 262 Figure 2	β(t₀) = 0.488	EN 1992-1-1 (B.5)
Development with time[(t − t₀)/(β_H + t − t₀)]^0.3, β_H = 540SIA 262 Figure 2	β(t − t₀) = 0.994	EN 1992-1-1 (B.7)
Creep coefficientφ_RH·β_fc·β(t₀)·β(t − t₀)for concrete stresses up to 0.4·f_cm; above, 3.1.2.6.3 increases it	φ(t, t₀) = 2.35	§ 3.1.2.6.2 (13)

Calculation: Moments under the service load
Step	Value	Ref.
Cracking moment per metrek_t·f_ct·h²/6	m_cr = 18.7 kNm/m	§ 4.4.1.3
Modular ratioE_s/E_cm	α_s = 6.10

Calculation: Bottom bars along x (span)
Step	Value	Ref.
Service moment, with the twisting momentlargest at x = 4.00 m, y = 2.00 m	m + \|m_xy\| = 10.4 kNm/m
State	uncracked (m ≤ m_cr)

Calculation: Bottom bars along y (span)
Step	Value	Ref.
Service moment, with the twisting momentlargest at x = 1.80 m, y = 3.20 m	m + \|m_xy\| = 14.0 kNm/m
State	uncracked (m ≤ m_cr)

Calculation: Top bars along x (supports, corners)
Step	Value	Ref.
Service moment, with the twisting momentlargest at x = 6.00 m, y = 2.00 m	m + \|m_xy\| = 18.3 kNm/m
State	uncracked (m ≤ m_cr)

Calculation: Top bars along y (supports, corners)
Step	Value	Ref.
Service moment, with the twisting momentlargest at x = 3.10 m, y = 4.50 m	m + \|m_xy\| = 18.9 kNm/m
State	cracked (m > m_cr)
Neutral axis depth, cracked	x_II = 28.4 mm	§ 4.1.4.2.1
Concrete stress−2·m/(x_II·z)compression negative	σ_c = -9.14 N/mm²
Bar stressm/(a_s·(d − x_II/3))	σ_s = 248.2 N/mm²

Calculation: Check 1 — bar stress under the quasi-permanent load, top bars along y (supports, corners)
Step	Value	Ref.
Bar stress against the crack limit, top bars along y (supports, corners)σ_s/f_yk	η = 0.496 · Pass50 % of the capacity used	Table 17

Calculation: Deflection
Step	Value	Ref.
Plate stiffnessE_cm·h³/(12·(1 − ν²))	D = 23,333 kNm
Elastic deflection, uncrackedelastic plate under q and the loads Qlargest at x = 3.10 m, y = 2.00 m	w_c = 0.65 mm
Long-term deflection, uncrackedw_c·(1 + φ)	w_cφ = 2.18 mm	§ 4.4.3.2.4 (103)

Calculation: Check 2 — deflection
Step	Value	Ref.
Deflection against the admissible valuew/w_adm	η = 0.167 · Pass17 % of the capacity used	§ 4.4.3.2

Calculation: Bar options
Step	Value	Ref.
Cracking moment per metrek_t·f_ctm·h²/6	m_cr = 18.7 kNm/m	§ 4.4.1.3
Largest spacing allowedmin(1.2·h ; 300 mm)	s_max = 240 mm	§ 5.5.3.1

Calculation: Bottom bars along x — chosen zone by zone
Step	Value	Ref.
Zones with these barsof 48 zones of 0.75 × 0.75 m — Ø10@200: 48	n_z = 48
Steel mass of this layerwithout laps and anchorages	G = 83 kg
Bending in every zone, bottom bars along xmax(m_d/m_Rd)	η = 0.644 · Pass64 % of the capacity used	§ 4.3.2.6

Calculation: Bottom bars along y — chosen zone by zone
Step	Value	Ref.
Zones with these barsof 48 zones of 0.75 × 0.75 m — Ø10@200: 48	n_z = 48
Steel mass of this layerwithout laps and anchorages	G = 83 kg
Bending in every zone, bottom bars along ymax(m_d/m_Rd)	η = 0.875 · Pass87 % of the capacity used	§ 4.3.2.6

Calculation: Top bars along x — chosen zone by zone
Step	Value	Ref.
Zones with these barsof 48 zones of 0.75 × 0.75 m — Ø8@200: 2, Ø10@200: 30, Ø10@150: 3	n_z = 35
Steel mass of this layerwithout laps and anchorages	G = 61 kg
Bending in every zone, top bars along xmax(m_d/m_Rd)	η = 0.845 · Pass84 % of the capacity used	§ 4.3.2.6

Calculation: Top bars along y — chosen zone by zone
Step	Value	Ref.
Zones with these barsof 48 zones of 0.75 × 0.75 m — Ø8@200: 2, Ø10@200: 29, Ø10@150: 4	n_z = 35
Steel mass of this layerwithout laps and anchorages	G = 62 kg
Bending in every zone, top bars along ymax(m_d/m_Rd)	η = 0.945 · Pass95 % of the capacity used	§ 4.3.2.6
Total steel mass of the panel10.7 kg/m², without laps and anchorages	ΣG = 289 kg

Calculation: Deflection with the chosen bars
Step	Value	Ref.
Long-term deflection, uncracked	w_cφ = 2.18 mm	§ 4.4.3.2.4 (103)
Deflection against the admissible valuew/w_adm	η = 0.167 · Pass17 % of the capacity used	§ 4.4.3.2

How this module is verified

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

Questions

How is the moment for ε_v taken at each edge?

At a simply supported edge, m_d ≈ v_d · d/2 at the control section; at a fixed or continuous edge, m_d is the support moment. It enters ε_v = f_yd/E_s · m_d/m_Rd, equation (39).

Why does a corner need holding down?

A corner between two simply supported edges tends to lift and needs a holding-down force, given by the elastic analysis, and top and bottom corner reinforcement for the twisting moments m_xy.

Can I print the calculation?

The full calculation is shown on screen, free and without an account. A print-ready A4 calculation note is part of the Basic plan.

Norm: SIA 262:2025 · Page updated: 24 October 2026

Two-way slab on edge supports to SIA 262

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