Steel Sections — validation & limitations

What it calculates

• EN 1993-1-1 section classification (Class 1–4) using the right Table 5.2 sheet per element — outstand limits for I/H flanges, internal-part limits for webs and hollow walls (with the web classified for the axial compression it carries), and d/t for circular hollow sections
• Bending, shear and axial unity checks per Eurocode 3 §6.2 (elastic and plastic resistances with γ_M0 = 1.0)
• Lateral-torsional buckling (LTB) check with χ_LT reduction factor and design buckling moment resistance M_b,Rd (EN 1993-1-1 §6.3.2.2 general case, curve b), or a fully-restrained compression flange declared explicitly
• M-N interaction diagram for combined bending and axial load per EN 1993-1-1 §6.2.9 (Class 1/2 linear boundary)
• Compression with bending checked against a conservative Method 2 bound of EN 1993-1-1 §6.3.3 Eq. 6.61 / 6.62 (Annex B with C_m = 1 and buckling curve c, rolled sections): at or below 1 it passes, above 1 the tool returns NO RESULT rather than a verdict it cannot support
• Deflection under UDL AND point load, using the formula for the actual support condition (simply supported, cantilever, fixed-fixed or propped), checked against an L/300 target
• Resistance of the web to transverse forces (EN 1993-1-5 §6, patch loading / web crippling) under the point load and at bearing end supports for I/H sections, with the §7.2 interaction with bending at the point load — enter the stiff bearing lengths, or a knife-edge bearing (s_s = 0) is assumed and labelled
• Side-by-side section comparison with radar chart (Iy, Iz, Wy,el, mass, height) and material-efficiency index (Wy,el / mass)

Standards this tool applies

• EN 1993-1-1 — EN 1993-1-1 section classification, bending/shear/axial unity checks, LTB (§6.3.2.2 general case: curve b rolled, c/d welded), M-N interaction and a conservative §6.3.3 (Method 2) compression-with-bending bound for European IPE, HEA, HEB, RHS, SHS and CHS profiles.
• EN 1993-1-8 — EN 1993-1-1 cross-section resistance and LTB for the steel members that EN 1993-1-8 joints connect — section classification, bending/shear/axial unity checks and M-N interaction.

Validation evidence — independent reference cases (2)

Each case runs the tool's engine on a worked example whose values come from a published source or a hand derivation from the cited equations, and an automated regression test asserts the engine against those values within the stated tolerance. "Conservative" means the engine is known to sit on the safe side of the reference and the test asserts that side. Sources are cited; their text is not reproduced.

• Section class, bending and shear resistance, UDL deflection (IPE 300)

  Agrees

  Source: EN 1993-1-1:2005 Table 5.2, §6.2.5, §6.2.6, Table 3.1, §3.2.6; EN 10365 / ArcelorMittal section tables; Roark Table 8.1 case 2e

  Inputs: IPE 300, S235, simply supported, L 6 m, w 20 kN/m, fully restrained, N_Ed 0

  Quantity	Reference value	Tolerance
  M_c,Rd (kN·m)	147.674	0.2 % relative
  V_pl,Rd (kN)	348.415	0.2 % relative
  bending utilisation	0.60945	0.2 % relative
  deflection (mm)	19.2334	0.2 % relative

  tests/golden/REF-steel-cross-section.golden.test.ts

• Flexural buckling of a column and lateral-torsional buckling of a beam

  Conservative

  Source: EN 1993-1-1:2005 §6.3.1.2, Tables 6.1, 6.2, §6.3.2.2, Table 6.4; Timoshenko & Gere, Theory of Elastic Stability §6 (M_cr); EN 10365 / ArcelorMittal section tables

  Inputs: HEB 200 S235 pinned L 4 m, N_Ed 1000 kN; IPE 300 S235 L 5 m, uniform M_Ed 60 kN·m, load at shear centre

  Quantity	Reference value	Engine	Tolerance
  chi_z (HEB 200, curve c)	0.636942	—	0.1 % relative
  N_b,Rd (kN)	1168.71	—	0.1 % relative
  M_cr (kN·m)	115.685	about 113.16	-4 % / +0.5 %
  M_b,Rd IPE 300 (kN·m)	85.026 (curve a)	within 2.5 % of 76.439 (curve b)	one-sided (engine <= curve-a reference)

  Conservative simplification: The engine uses buckling curve b for lateral-torsional buckling of every section and recomputes I_t and I_w, which lowers M_cr by about 2.2 %; M_b,Rd for the IPE 300 reads about 10 % below the Table 6.4 curve-a reference of 85.026 kN·m.

  tests/golden/REF-steel-member-buckling.golden.test.ts

Limitations

Conservative simplifications

• Flexural buckling of a column and lateral-torsional buckling of a beam — The engine uses buckling curve b for lateral-torsional buckling of every section and recomputes I_t and I_w, which lowers M_cr by about 2.2 %; M_b,Rd for the IPE 300 reads about 10 % below the Table 6.4 curve-a reference of 85.026 kN·m.

Not checked by this tool

• Class 4 effective section (EN 1993-1-5 section 4.4) — A Class 4 section returns NO RESULT; compute the effective section or pick a stockier section
• Biaxial bending and the full M_N,Rd interaction (EN 1993-1-1 section 6.2.9) — Bending about one axis only; check minor-axis bending by hand
• Connections, splices and base plates — Check them with /bolts and /welds (EN 1993-1-8)
• Fatigue (EN 1993-1-9) — Static design only; for cranes, machinery or traffic loads check the detail categories (/welds fatigue panel)
• Brittle fracture: steel sub-grade for thickness and temperature — Select the toughness sub-grade per EN 1993-1-10
• Fire resistance — Room-temperature design only; use EN 1993-1-2
• Floor vibration (natural frequency) — Not checked; check the frequency of footfall-sensitive floors (e.g. /beams natural frequency)