declared calculation basis
A transparent subset of EN 1993-1-1
This calculator is deliberately limited to doubly symmetric rolled I/H sections (UB, UC and supported joist records), manually entered rolled-section dimensions and properties, or a custom welded sharp-corner I/H whose properties are calculated from entered geometry. Manual section properties are separate inputs, not recalculated from dimensions. Reference records with inconsistent dimensional/elastic-property relationships are excluded; remaining records still require manufacturer verification. It classifies webs and flanges using §5.5 and Table 5.2. Class 4 and plate shear buckling are flagged rather than given a full resistance pass.
Parameter input guide
- Section: choose a listed rolled section in section-catalogue mode; enter rolled-section dimensions and properties separately in manual-section-properties mode; or calculate properties from welded I/H dimensions in custom-geometry mode. Geometry is in mm; area and second moments are in mm² and mm⁴; section moduli are in mm³. Check catalogue and manually entered values against the manufacturer’s section tables. Custom geometry assumes rectangular flanges and web, excluding welds and fillets.
- Material and factors: enter fy, γM0 and γM1. The calculator does not choose a National Annex or infer thickness-dependent grade reductions.
- ULS actions: enter NEd, My,Ed, Mz,Ed, Vy,Ed, Vz,Ed, TEd and warping action where relevant. Major-axis high-shear handling is available for Class 1/2; combined high-shear N/Mz and two-axis shear remain explicit report items.
- Member stability: enter independent y/z buckling lengths and an Mcr supplied by the designer. General and rolled-special LTB use the declared αLT, β and λLT,0 inputs; unknown restraint is not treated as a favourable assumption.
- SLS: the simply-supported full-span UDL and central point-load terms use separate total and variable service inputs. Variable load must not exceed total load. Enter the project L/d limits; these are project screens, not guaranteed code compliance.
Section classification and resistance
Class 1 and 2 plastic bending resistance uses Eq. 6.13; Class 3 uses elastic resistance under Eq. 6.14. Shear resistance uses §6.2.6, Eq. 6.18. The major-axis high-shear branch is restricted to Class 1/2 and uses Eqs. 6.29–6.30. For low shear, a conservative linear section interaction is shown under §6.2.1, Eq. 6.2. Gross axial yield is reported under §§6.2.3–6.2.4. These are section resistances; they do not establish a complete member force envelope or connection design.
Common input mistakes
- Do not confuse vertical Vz,Ed with horizontal Vy,Ed, or an SLS span with a buckling effective length.
- Do not reuse Mcr after changing the section or restraints. The calculator clears that input on section changes; it must be reassessed independently.
- Do not enter warping Iw in cm³: its units here are mm⁶. A torsional modulus is a different property.
- Do not apply ULS factored actions as SLS service loads. Include self-weight in the total service load, and enter project deflection limits explicitly.
- Do not read an independent resistance ratio as a complete member check. Connections, local concentrated forces and omitted interaction/stability modes may govern.
For the related CivilKits explanation of section resistances and National Annex inputs, read the Eurocode calculation scope guide; use the I-section property guide when revising custom dimensions.
Member stability and interaction
Independent y/z flexural-compression screens follow §6.3.1.2. Lateral-torsional buckling follows the general method in §6.3.2.2 or the rolled special case in §6.3.2.3 using the user-supplied Mcr. N+M interaction is reported as a screen; it is not a substitute for every applicable interaction branch. Torsion and warping actions are retained as nonzero inputs and are not discarded, but no complete torsion/warping member design is claimed.
Worked example: UB 305×102×28
For orientation only, a Class 1 UB 305×102×28 with fy = 275 MPa, γM0 = 1.0, γM1 = 1.1, A = 3,590 mm², Iy = 53.66×106 mm⁴, Iz = 1.55×106 mm⁴, Wpl,y = 403,000 mm³, Wel,y = 348,000 mm³, Wpl,z = 48,500 mm³ and Wel,z = 30,500 mm³ gives Mpl,y,Rd = 110.825 kN·m and Vpl,z,Rd = 315.142 kN. With My,Ed = 50 kN·m, Vz,Ed = 60 kN, all other listed actions zero, supplied Mcr = 91.8107217684 kN·m and rolled αLT = 0.49, β = 0.75, λLT,0 = 0.4, the declared screen gives Mb,Rd ≈ 58.5105 kN·m and utilisation ≈ 85.45%. For a 3 m simply-supported span with total UDL 5 kN/m and central point load 10 kN, the elastic full-span deflection is the sum of 5wL⁴/(384EI) and PL³/(48EI); the L/250 comparison is an editable project example, not a prescribed universal limit.
What this calculator does not establish
- No complete EN 1993 member design, load-combination generation, restraint or effective-length selection is performed.
- Class 4 sections, plate shear buckling, local patch loading, web crippling, bearing, connections, fatigue, fire, seismic, vibration, erection stages and accidental design are outside scope.
- Catalog data are not a substitute for project drawings or a verified section table. A custom welded section assumes sharp corners and does not check welds, residual stress or fabrication tolerances.
- Serviceability is an elastic simply-supported screen only; no composite action, cracking, creep, vibration or second-order analysis is included.
- A “pass” on an individual screen is not a guarantee of all-code compliance. Any unavailable or blocked branch is labelled explicitly in the report.
Engineering disclaimer
For learning and preliminary checking only. Do not rely on these results alone for construction, statutory submission, certification or safety decisions. A qualified engineer must independently verify inputs, equations, combinations, code editions and every governing check. Content and software may contain errors or omissions; no guarantee of completeness or fitness for a project is given.
Read the terms and full disclaimer. A disclaimer does not itself guarantee immunity from liability.