Section Comparison — UB, UC, IPE, HEA, HEB & W-Shapes

Structural steel sections manufactured to different national standards can look similar on a drawing yet behave differently under load. This reference provides side-by-side property comparisons, a worked substitution example, code-specific requirements for section classification, and the pitfalls engineers encounter when substituting sections across standards.

Section families and their standards

W-shapes (AISC / ASTM A6)

Wide-flange sections designated by nominal depth and weight per foot (e.g., W360x33 in metric or W14x22). Standardized per ASTM A6/A6M. Default grade: ASTM A992 (Fy = 345 MPa / 50 ksi, Fu = 450 MPa / 65 ksi). Most common structural shape in North America.

UB / UC (BS 4-1, AS/NZS 3679.1)

Universal Beams (UB) have deeper webs optimized for bending; Universal Columns (UC) have roughly equal depth and width, optimized for axial compression. Designated by serial size and mass per meter (e.g., 310UB40.4). Default grade: AS/NZS 3679.1 Grade 300 (Fy = 300 MPa, Fu = 440 MPa) or BS EN 10025 S275/S355.

IPE / HEA / HEB (EN 10025, EN 10034)

European I-sections with parallel flanges. IPE sections have narrow flanges for bending. HEA (light) and HEB (standard) have wider flanges suited for columns. HEM (heavy) series exists for high-axial-load columns. Default grade: S355 (fy = 355 MPa, fu = 510 MPa for t <= 16 mm).

Key dimensional differences

Notice: W14x22, 310UB40.4, and IPE 300 have similar Ix values (~83-86 x 10^6 mm^4) but very different flange widths (127 vs 166 vs 150 mm). This means their lateral-torsional buckling resistance differs significantly even though bending stiffness is nearly identical.

Worked example — substituting W310x33 with 310UB40.4

Problem: A project designed to AISC 360 with W310x33 (W12x22) must source sections in Australia where only UB/UC sections are available. Is 310UB40.4 an adequate substitute for a 6 m simply-supported floor beam?

Step 1 — Compare bending capacity (AISC 360 Eq. F2-1 vs AS 4100 Cl. 5.1):

AISC: phiMn = 0.90 x Fy x Zx = 0.90 x 345 x 545x10^-3 = 169 kN-m (W310x33)

AS 4100: phiMs = 0.90 x fy x Ze = 0.90 x 300 x 634x10^-3 = 171 kN-m (310UB40.4, compact)

Bending capacities are comparable (169 vs 171 kN-m), but note the Australian section uses a lower Fy (300 vs 345 MPa) offset by its larger Zx.

Step 2 — Compare deflection (stiffness check):

Ix(W310x33) = 82.8 x 10^6 mm^4 vs Ix(310UB40.4) = 86.4 x 10^6 mm^4. The UB section is 4.3% stiffer, so deflection is acceptable.

Step 3 — Check lateral-torsional buckling:

The 310UB40.4 has a wider flange (bf = 166 mm vs 127 mm), giving it better lateral stability. LTB capacity is adequate.

Step 4 — Check weight penalty:

310UB40.4 weighs 40.4 kg/m vs 32.7 kg/m for W310x33, a 24% weight increase. On a 6 m beam this adds 46 kg of steel, roughly $50-70 USD in material cost. Acceptable for procurement flexibility.

Conclusion: 310UB40.4 is a valid substitute, but the engineer must verify local buckling classification under the governing code (the section may be compact under AISC but non-compact under AS 4100 due to different slenderness limits).

Code-specific section classification limits

Section classification determines whether a member can develop full plastic moment (Class 1/Compact) or is limited to elastic capacity (Class 3-4/Slender). The slenderness limits differ across codes:

Flange slenderness (half-width / thickness, compression flange of I-beam):

Where epsilon = sqrt(235/fy). For S355: epsilon = 0.81, so Class 1 limit = 7.3.

Web slenderness (clear depth / thickness, pure bending):

A section that is compact under AISC may be Class 2 (non-compact equivalent) under EN 1993 due to the tighter European flange limits. Always re-classify when changing codes.

Common pitfalls in cross-standard section substitution

1. Matching only one property. A section with equal Ix to the original may have a much smaller Zx, lower flange width (worse LTB), or different web thickness (affecting shear and web crippling). Always compare the full property set: Ix, Zx, Sx, ry, J, Cw, bf, tf, tw, and Ag.

2. Ignoring different yield strengths. ASTM A992 has Fy = 345 MPa; AS/NZS Grade 300 has Fy = 300 MPa; EN S275 has fy = 275 MPa. A section with 10% more Zx but 15% lower Fy results in a net capacity reduction. Capacity is Fy x Zx, not just Zx.

3. Not re-classifying the section under the new code. The AISC compact/non-compact limits differ from AS 4100 and EN 1993 plate slenderness classes. A W-shape that is compact under AISC 360 Table B4.1b may be Class 2 or even Class 3 under EN 1993 Table 5.2, reducing the usable section modulus from plastic (Zx) to elastic (Sx).

4. Overlooking connection compatibility. Different section families have different flange widths, web thicknesses, and fillet radii. A connection designed for a W-shape flange may not work with a UB flange due to different bolt gage, access clearance, or weld root gap. Column splice plates, beam-to-column clips, and base plates often need redesign.

Frequently asked questions

Are W-shapes and UB sections interchangeable? Not directly. While some have similar depth and Ix, they differ in flange proportions, web thickness, fillet radius, and standard grades. Each substitution requires a full property comparison and re-check of all limit states under the governing code.

Which section is most efficient for bending? For pure strong-axis bending, IPE sections are typically the lightest because their deep, narrow profile maximizes Ix per kg. However, their narrow flanges make them more susceptible to LTB, so they require closer bracing spacing.

Can I use European section data with AISC 360? Yes, but you must verify that the section properties are computed per AISC conventions (e.g., k-design vs k-detailing for web depth, fillet radius treatment) and that the material grade meets AISC requirements or is approved as an equivalent per AISC 360 Section A3.1a.

Run this calculation

• Section Properties Database
• Beam Calculator
• Column Capacity Calculator

Related references

• Beam Sizes Reference
• HSS Section Properties
• Steel Angle Sizes
• Steel Channel Sizes
• How to Verify Calculations
• Beam capacity calculator
• IPE vs HEA vs UB Steel Sections

Disclaimer

This page is for educational and reference use only. It does not constitute professional engineering advice. All design values must be verified against the applicable standard and project specification before use. The site operator disclaims liability for any loss arising from the use of this information.