Universal Beams (UB) — BS 4-1 Series

UK universal beams are designated by nominal depth (mm) and mass per metre (kg/m). All sections are hot-rolled from S275 or S355 steel to BS EN 10025-2. The standard range covers 178 mm to 1016 mm deep.

Universal Columns (UC) — BS 4-1 Series

UK universal columns carry axial load in multi-storey frames. The range covers 152 mm to 356 mm deep. UC sections have approximately equal depth and width for efficient buckling resistance about both axes.

Parallel Flange Channels (PFC) — BS 4-1 Series

UK PFC sections are used for bracing, edge beams, stair stringers, and secondary framing. Designated by depth and mass.

UK Steel Grades for Sections

UK sections are typically supplied in S275 or S355 to BS EN 10025-2. For buildings designed to BS 5950-1:2000, the design strength py depends on the flange thickness:

BS 5950-1 uses py = minimum yield strength from these tables. EN 1993-1-1 uses fy with gamma_M0 = 1.00.

Worked Example — Beam Selection for UK Office Floor

Problem: Select a UK universal beam for a simply supported floor beam spanning 6.0 m at 3.5 m centres in a commercial office. Dead load 4.5 kN/m² (150 mm RC slab on steel deck + services + ceiling), live load 3.5 kN/m² (BS 6399-1 office loading). Steel grade S275.

Step 1 — Factored Loads (BS 5950-1):

Unfactored dead: w_d = 4.5 x 3.5 = 15.75 kN/m. Add 0.50 kN/m self-weight estimate. Total: 16.25 kN/m. Unfactored live: w_l = 3.5 x 3.5 = 12.25 kN/m.

Ultimate load: w_u = 1.4 x 16.25 + 1.6 x 12.25 = 22.75 + 19.60 = 42.35 kN/m.

Step 2 — Design Moment and Shear:

M_x = w_u x L² / 8 = 42.35 x 36 / 8 = 190.6 kN·m. F_v = w_u x L / 2 = 42.35 x 6.0 / 2 = 127.0 kN.

Step 3 — Required Section Modulus:

S_req = M_x / py = 190.6 x 10⁶ / 275 = 693 x 10³ mm³ = 693 cm³.

Try 356x171x45 UB (S_x = 688 cm³ — close to required, check).

Step 4 — Bending Check (BS 5950-1 Clause 4.2.5):

M_c = py x S_x = 275 x 688 x 10³ / 10⁶ = 189.2 kN·m. M_x / M_c = 190.6 / 189.2 = 1.007 — marginally over. Try next section.

Try 406x178x54 UB (S_x = 931 cm³): M_c = 275 x 931 x 10³ / 10⁶ = 256.0 kN·m. Utilisation = 190.6 / 256.0 = 0.74. OK.

Step 5 — Shear Check (BS 5950-1 Clause 4.2.3):

P_v = 0.6 x py x D x t = 0.6 x 275 x 403 x 7.7 / 1000 = 512 kN. 127.0 < 0.6 x 512 = 307 kN — no moment-shear interaction. OK.

Step 6 — Deflection Check (BS 5950-1 Table 8):

Live load deflection limit: span / 360 = 6000 / 360 = 16.7 mm. delta_ll = 5 x 12.25 x 6000⁴ / (384 x 205000 x 18700 x 10⁴) = 5 x 12.25 x 1296 x 10¹² / (384 x 205000 x 18700 x 10⁴) = 7.94 x 10¹⁶ / 1.473 x 10¹⁴ = 5.4 mm. OK.

Selected section: 406x178x54 UB in S275.

UK Joist Sections — Additional Lightweight Options

For lighter framing, UK practice also uses:

These lighter sections are commonly specified for domestic and light commercial construction where the standard UB range starts heavier than needed.

Section Designation Conventions — UK vs European

UK BS 4-1 sections differ from European Euronorm sections in designation and dimensions:

Critical note for UK projects: Do not substitute EN 10365 sections for BS 4-1 sections without re-running the full design. The section properties (I, Z, A, r) differ, and using the "nearest equivalent" can produce 5-15% differences in design utilisation. Always use the section database that matches your project specification.

Steel Section Procurement for UK Projects

When specifying steel sections for UK construction, include these details on the steelwork schedule:

1. Designation: e.g., 406x178x54 UB (BS 4-1)
2. Steel grade and sub-grade: e.g., S275JR, S355J0
3. Length: exact cut length including end preparation (saw cut, 2 mm tolerance)
4. Camber: if required — "camber to 75% of dead load deflection" or "no camber"
5. Surface preparation: blast cleaning to SA 2.5 per BS EN ISO 8501-1
6. Shop primer: typically 15-25 micrometres DFT zinc-rich epoxy primer
7. CE/UKCA marking: required for all structural steelwork per UK Construction Products Regulations

For UK projects after Brexit, UKCA marking (not CE marking) applies to steel products placed on the GB market. BS EN 10025-2 is a designated standard under the UK Construction Products Regulations 2013. The test certificate (EN 10204 Type 3.1 or 3.2) must reference the UK-designated standard.

Service Integration — Beam Penetrations and Notches

In multi-storey UK buildings, services (HVAC, sprinklers, electrical) pass through beam webs. Key guidance per SCI P355:

• Circular web openings: Diameter <= 0.75D (D = beam depth), centreline at mid-depth
• Rectangular openings: Height <= 0.6D, length <= 1.5x height
• Opening spacing: Centre-to-centre >= 2.5x larger opening dimension
• Edge distance: From support >= D/2, from concentrated load >= D
• Reinforcement: Required when the opening reduces the beam capacity below the demand. Typically horizontal stiffeners above and below the opening, fillet welded.

For a 406x178x54 UB with a 250 mm diameter circular opening at mid-depth:

• Check Vierendeel bending across the opening
• Check shear in the top and bottom tee sections
• Local buckling of the web posts between adjacent openings

These checks are typically performed using SCI P355 design aids or finite element analysis for complex opening layouts. For standard office buildings, beam cellular openings are typically pre-planned and the beam size is upsized by 10-15% to account for the opening effects.

Related Pages

• UK Steel Beam Design — BS 5950 Flexure & LTB
• UK Column Design — BS 5950 Compression Members
• UK Steel Properties — fy & fu Values
• UK Compact Section Limits — BS 5950 Classification
• UK Deflection Limits — BS 5950 Serviceability
• UK Lateral Torsional Buckling — BS 5950 Cl. 4.3
• UK Load Combinations — BS 5950 ULS & SLS
• UK Connection Design — Bolted & Welded
• Beam Capacity Calculator — Free Online Tool

Educational reference only. Verify section properties against current Tata Steel Blue Book or SCI P363. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent Chartered Engineer verification per UK Building Regulations Approved Document A.