Checks any steel section described by its properties under a moment, an axial force and a shear force acting together, to SIA 263:2013: the shear, the moment resistance reduced by it, then the interaction with the axial force, on the model the class you enter allows. Every step shows its formula and the clause it comes from.

What it checks

Resistance model, table 4, from the class you enter: class 1 or 2, plastic resistance; class 3, elastic; class 4, elastic on the effective section. The model is named beside the result.
Plastic resistances: M_pl,Rd = f_y,k · W_y,pl/γ_M1 and N_pl,Rd = f_y,k · A/γ_M1.
Shear force, check 1, equation (41): V_Ed ≤ V_Rd = τ_y,k · A_v/γ_M1.
Moment resistance reduced by the shear, equation (43) in a generalised form: M_V,Rd = f_y,k · (W_y,pl − W_v,pl · (V_Ed/V_Rd)²)/γ_M1. The shear-area part of W_y,pl is reduced only above V_Ed/V_Rd = 0.5.
Bending with an axial force and a shear force, check 2: N_Ed/N_pl,Rd + M_y,Ed/M_V,Rd ≤ 1. The moment resistance already reduced by the shear goes into the denominator. The linear interaction is a chord across the true interaction surface, so it is safe but can be conservative.

What you enter and what you get

You enter f_y,k and τ_y,k from table 1 of your copy of SIA 263, for the grade and the plate thickness, the section class (table 4), the gross area A, the plastic section modulus W_y,pl, the shear area A_v (equation (42a)), the plastic modulus of the shear area W_v,pl (equation (43)) and γ_M1 (clause 4.1.3). For a doubly symmetric I, W_v,pl is that of the web, h_w² · t_w/4. You choose whether the axial force is compression or tension, and enter N_Ed, the moment M_y,Ed about the strong axis and V_Ed in the same plane, all as magnitudes.

You get the resistance model, both plastic resistances, the shear utilisation, the moment resistance reduced by the shear, the two terms of the interaction and the utilisation of each check with a pass or fail. With the Basic plan, it prints as an A4 calculation note.

Assumptions and limits

Nothing here knows what section you have, so nothing can check what you enter. Where the rectangle or the rolled I module fits your section, use it: those derive the properties from the dimensions and draw the section.
The class is entered, because section properties carry no information about the slenderness of the plates.
The shear reduction of equation (43) is written for a doubly symmetric I: the flange term is untouched and the web term is reduced by (V_Ed/V_Rd)². Here it is applied in the same way to W_v,pl. For an I with W_v,pl = h_w² · t_w/4 this is equation (43) itself.
τ_y,k is entered from table 1, not derived as f_y,k/√3. Over the eight cells of table 1 the division gives the higher, unconservative value in six.
A section check only. Buckling under a compressive force, lateral-torsional buckling and torsion are not covered.

Worked example

A class 1 section with A = 8,680 mm², W_y,pl = 920,000 mm³, A_v = 2,876 mm² and W_v,pl = 94,922 mm³, in f_y,k = 235 N/mm² and τ_y,k = 135 N/mm², under N_Ed = 400 kN in compression, M_y,Ed = 80 kN·m and V_Ed = 300 kN. These are the module's own results for its worked example, computed when this page was built.

Inputs
Input	Value	Ref.
Characteristic yield strength f_y,k	235 N/mm²	§ t.1
Characteristic shear yield strength τ_y,k	135 N/mm²	§ t.1
Section class	1	§ t.4
Gross area A	8680 mm²
Plastic section modulus W_y,pl	920000 mm³
Shear area A_v	2876 mm²	§ (42a)
Plastic modulus of the shear area W_v,pl	94922 mm³	§ (43)
Resistance factor γ_M1	1.05	§ 4.1.3
The axial force is	Compression
Design axial force N_Ed	400 kN
Design bending moment M_y,Ed	80 kN·m
Design shear force V_Ed	300 kN

Calculation: Common values
Step	Value	Ref.
Characteristic yield strength	f_y,k = 235 N/mm²	§ t.1
Characteristic shear yield strengthEntered from table 1, not derived.	τ_y,k = 135 N/mm²	§ t.1
Resistance factor	γ_M1 = 1.05	§ 4.1.3
Section classEntered. Section properties carry no information about the slenderness of the plates.	– = 1	§ t.4
Resistance model	PLASTIC. Table 4 allows a plastic resistance to a class 1 section.	§ t.4
Area	A = 8,680 mm²
Plastic moment resistancef_y,k·W_y,pl/γ_M1.	M_pl,Rd = 205.90 kN·m	§ 4.1.3
Plastic axial resistancef_y,k·A/γ_M1.	N_pl,Rd = 1,942.7 kN	§ 4.1.3

Calculation: Common values — the moment resistance reduced by the shear
Step	Value	Ref.
Shear utilisationThe shear-area part of W_pl is reduced only above 0,5.	V_Ed/V_Rd = 0.8113
Moment resistance reduced by the shearf_y,k·[W_y,pl − W_v,pl·(V_Ed/V_Rd)²]/γ_M1, with (V_Ed/V_Rd)² = 0.6582.	M_V,Rd = 191.92 kN·m	§ (43)

Calculation: Check 1 — shear force
Step	Value	Ref.
Shear forceV_Ed ≤ V_Rd	η = 0.811 · Pass81 % of the capacity used	§ (41)

Calculation: Check 2 — bending, axial force and shear
Step	Value	Ref.
Axial term	N_Ed/N_pl,Rd = 0.2059
Moment termThe moment resistance already reduced by the shear goes into the denominator.	M_y,Ed/M_V,Rd = 0.4168
Bending with an axial force and a shear forceN_Ed/N_pl,Rd + M_y,Ed/M_V,Rd ≤ 1	η = 0.623 · Pass62 % of the capacity used

How this module is verified

Verified clause by clause against SIA 263:2013 and against independent calculations used on real projects, before release.

Questions

Which class should I enter?

The class of the section under these forces. The sense of the axial force does not change the resistances, but it changes the class: a compressive force puts more of the web in compression. Classify the section with the classification module, with the axial force and the moment acting.

Why is the moment resistance higher than in the rolled I module?

The worked example enters the properties of the rolled section of that module's worked example, under the same forces. Here M_V,Rd = 191.9 kN·m and η = 0.623. The rolled I module applies equation (43) to a plate model without the fillets, which at V_Ed = 0 sits 5.8 % below f_y,k · W_y,pl/γ_M1: there M_V,Rd = 180.0 kN·m and η = 0.650.

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 263:2013 · Page updated: 8 November 2026

Steel section in bending, axial force and shear from its properties to SIA 263

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