What is the difference between UKC and UC sections?

UKC (UK Universal Column) is the modern designation for what was historically called UC. Sections are identical in geometry. UKC sections have approximately equal depth and flange width (aspect ratio near 1.0), thicker flanges and webs than UKB, and are optimised for axial compression. Section properties match the Tata Steel Blue Book.

What UKC sizes are most commonly used in UK building frames?

The most common UKC sections: 203x203 UKC (46 to 86 kg/m) for columns in 3-5 storey buildings; 254x254 UKC (73 to 167 kg/m) for 5-12 storey commercial buildings; and 305x305 UKC (97 to 198 kg/m) for 8-15 storey office towers. The heaviest sections, 356x406 UKC (235 to 634 kg/m), are used for high-rise columns and transfer structures.

How does column buckling design work under EN 1993-1-1 for UKC?

Column buckling per EN 1993-1-1 Clause 6.3.1: compute non-dimensional slenderness lambda_bar = sqrt(A x fy / Ncr), then determine reduction factor chi from buckling curve c for weak axis (alpha = 0.49) per UK NA. Design resistance Nb,Rd = chi x A x fy / gamma_M1. The UK NA sets gamma_M1 = 1.00.

What is the heaviest standard UKC section?

The heaviest standard UKC is the 356x406x634, weighing 634 kg/m with flange thickness 77.0 mm and area 808 cm^2. Used for high-rise columns carrying loads exceeding 20,000 kN. Requires through-thickness (Z-quality) steel per BS EN 10164 if subject to through-thickness tension from welded connections.

When should I specify S355 instead of S275 for UKC columns?

Specify S355 when: (1) lambda_bar < 1.0, where increased yield directly increases capacity; (2) weight reduction is critical - S355 saves 10-20% weight vs S275 for ~5-10% material cost premium; (3) restricted column size for architectural reasons; (4) in high-rise frames where maximum capacity from a given footprint is required.

How are UKC columns typically connected in UK steel frames?

Typical UKC connections: base plates welded to column, bolted to foundation with 4+ holding-down bolts; beam-to-column simple connections using double angle web cleats or flexible end plates; column splices ~3 m above floor level using flange cover plates and web splice plates. Full-strength moment connections use extended end plates to column flange.

UK Universal Column Guide — UKC Sizes, Properties, S275/S355 Applications

Q: How are UKC columns typically connected in UK steel frames?

Typical UKC connections: base plates welded to column, bolted to foundation with 4+ holding-down bolts; beam-to-column simple connections using double angle web cleats or flexible end plates; column splices ~3 m above floor level using flange cover plates and web splice plates. Full-strength moment connections use extended end plates to column flange.

Complete reference for UK Universal Column (UKC) sections — the standard hot-rolled H-column specified for compression members in British structural steelwork. Covers the full UKC range from 152x152x23 to 356x406x634, buckling behaviour per EN 1993-1-1, axial capacity estimation, and selection guidance for typical UK building frames.

Quick access: Section Properties Search | Column Capacity Calculator | UKB Beam Guide | Base Plate Design

UKC Designation System

UKC sections use the same metric convention as UKB:

Element	Description	Example
Nominal depth (mm)	Approx. overall depth	254
Flange width (mm)	Approx. flange width	254
Mass (kg/m)	Self-weight	107
Type	UKC	UKC

Full designation: 254x254x107 UKC

UKC sections have near-square profiles (aspect ratio ~1.0), optimised for compression.

UKC Dimensional Range

152x152 UKC Series (Light Columns)

Designation	Depth (mm)	Width (mm)	Web tw (mm)	Flange tf (mm)	Area (cm^2)	Mass (kg/m)	iy (cm)	iz (cm)
152x152x23	152.4	152.2	5.8	6.8	29.2	23.0	6.54	3.70
152x152x30	157.6	152.9	6.5	9.4	38.3	30.0	6.76	3.82
152x152x37	161.8	154.4	8.0	11.5	47.1	37.0	6.85	3.87
152x152x44	166.0	155.9	9.4	13.6	56.1	44.0	6.93	3.91
152x152x51	170.2	157.4	11.0	15.7	64.9	51.0	7.00	3.95

203x203 UKC Series (Medium Columns)

The most common series for 3-8 storey building columns.

Designation	Depth (mm)	Width (mm)	Web tw (mm)	Flange tf (mm)	Area (cm^2)	Mass (kg/m)	iy (cm)	iz (cm)
203x203x46	203.2	203.6	7.2	11.0	58.7	46.1	8.82	5.13
203x203x52	206.2	204.3	7.9	12.5	66.3	52.0	8.90	5.17
203x203x60	209.6	205.8	9.4	14.2	76.4	60.0	8.96	5.19
203x203x71	215.8	206.4	10.0	17.3	90.4	71.0	9.17	5.30
203x203x86	222.2	207.9	12.7	20.5	110	86.1	9.27	5.34
203x203x100	228.6	210.3	14.5	23.7	127	100	9.38	5.39

254x254 UKC Series (Heavy Columns)

For 6-15 storey buildings, transfer structures, and industrial framing.

Designation	Depth (mm)	Width (mm)	Web tw (mm)	Flange tf (mm)	Area (cm^2)	Mass (kg/m)	iy (cm)	iz (cm)
254x254x73	254.1	254.6	8.6	14.2	93.1	73.1	11.1	6.46
254x254x89	260.3	256.3	10.3	17.3	113	88.9	11.2	6.52
254x254x107	266.7	258.8	12.8	20.5	136	107	11.3	6.57
254x254x132	276.3	261.3	15.3	25.3	168	132	11.5	6.66
254x254x167	289.1	265.2	19.2	31.7	213	167	11.7	6.78

305x305 and 356x368/406 UKC (Very Heavy)

Designation	Depth (mm)	Width (mm)	Web tw (mm)	Flange tf (mm)	Area (cm^2)	Mass (kg/m)	iy (cm)	iz (cm)
305x305x97	307.9	305.3	9.9	15.4	123	96.9	13.4	7.73
305x305x118	314.5	307.4	12.0	18.7	150	118	13.6	7.82
305x305x137	320.5	309.2	13.8	21.7	174	137	13.7	7.89
305x305x158	327.1	311.2	15.8	25.0	201	158	13.9	7.97
305x305x198	339.9	314.5	19.1	31.4	252	198	14.2	8.12
305x305x240	352.5	318.4	23.0	37.7	306	240	14.5	8.30
305x305x283	365.3	322.2	26.8	44.1	360	283	14.8	8.47
356x368x129	355.6	368.6	10.4	17.5	164	129	15.2	9.43
356x368x153	362.0	370.5	12.3	20.7	195	153	15.4	9.52
356x368x177	368.2	372.6	14.4	23.8	226	177	15.5	9.59
356x368x202	374.6	374.7	16.5	27.0	257	202	15.6	9.68
356x406x235	381.0	394.8	18.4	30.2	299	235	16.3	10.3
356x406x287	393.6	399.0	22.6	36.5	366	287	16.5	10.5
356x406x340	406.4	403.0	26.6	42.9	433	340	16.8	10.6
356x406x393	419.0	407.0	30.6	49.2	501	393	17.0	10.8
356x406x467	436.6	412.4	35.8	58.0	595	467	17.3	11.0
356x406x551	455.6	418.5	42.1	67.5	702	551	17.7	11.2
356x406x634	474.6	424.0	47.6	77.0	808	634	18.1	11.4

Heavier sections (above 400 kg/m) are special-order items. Confirm availability with Tata Steel.

Column Buckling per EN 1993-1-1

The buckling resistance of a UKC column:

Step 1 — Squash load: Npl,Rd = A x fy / gamma_M0

Step 2 — Elastic critical load: Ncr = pi^2 x E x I / Lcr^2

Step 3 — Slenderness: lambda_bar = sqrt(A x fy / Ncr)

Step 4 — Reduction factor chi: UKC sections (h/b <= 1.2, tf <= 100 mm) use buckling curve 'c' for weak axis (alpha = 0.49).

Step 5 — Buckling resistance: Nb,Rd = chi x A x fy / gamma_M1

Worked example — 254x254x107 UKC in S355, Lcr = 4.0 m:

A = 136 cm^2, fy = 355 MPa, Npl,Rd = 4,828 kN
iz = 6.57 cm, Ncr,z = pi^2 x 210,000 x 5,880 x 10^4 / 4,000^2 / 1000 = 7,620 kN
lambda_bar,z = sqrt(4,828 / 7,620) = 0.796
Phi = 0.5 x (1 + 0.49 x (0.796 - 0.2) + 0.796^2) = 0.962
chi = 1 / (0.962 + sqrt(0.962^2 - 0.796^2)) = 0.670
Nb,Rd,z = 0.670 x 4,828 = 3,235 kN

Grade Selection

Grade	fy (MPa)	Npl,Rd (kN)	chi (Lcr=4m)	Nb,Rd (kN)
S275	275	3,740	0.718	2,685
S355	355	4,828	0.670	3,235

S355 provides ~21% capacity increase for ~5-10% cost premium.

When S355 provides value:

lambda_bar < 1.0 (stocky to intermediate columns)
Weight savings target (10-20% reduction)
Restricted column size (architectural preference)
Transfer columns — highest loads

When S275 is appropriate:

Very slender columns (lambda_bar > 1.5) — elastic buckling governs
Deflection-governed frames
Small projects with limited stock availability

Typical Applications

Application	UKC range	Axial load	Key considerations
Residential (3-5 storeys)	152x152 to 203x203	500-3,000 kN	Base plate, fire protection
Offices (5-12 storeys)	203x203 to 305x305	2,000-8,000 kN	Sway stiffness, splices
High-rise (15+ storeys)	305x305 to 356x406	6,000-25,000 kN	Axial shortening, concrete fill
Transfer columns	356x368 to 356x406	10,000-30,000 kN	Bearing, stiffeners
Portal frame legs	305x305 to 356x368	—	Combined bending + axial

FAQ

What is the weight difference between UKC and HEB for the same depth?

For approximately equivalent capacity: 254x254x107 UKC (107 kg/m, iz = 6.57 cm) vs HEB 260 (93 kg/m, iz = 6.58 cm). The HEB achieves similar buckling resistance at 13% less weight because parallel flanges give a slightly better iz/A ratio. However, UKC and HEB have different connection geometry — do not substitute without full re-check.

What buckling curve applies?

Curve 'c' (alpha = 0.49) for weak-axis buckling per UK NA to EN 1993-1-1. Strong-axis uses curve 'b' (alpha = 0.34) but rarely governs.

What is the standard UK approach to fire protection of UKC columns?

Three methods: (1) intumescent paint for up to 120 min; (2) board encasement for 60-180 min; (3) concrete encasement for highest ratings. Fire engineering per EN 1993-1-2 can demonstrate that heavier UKC sections achieve 30-60 min with reduced protection.

References

Tata Steel Blue Book — Section Properties and Member Capacities. Free PDF.
SCI P363 — Steel Building Design: Design Data.
BS EN 1993-1-1:2005 + A1:2014 — Eurocode 3.
NSSS 7th Edition — National Structural Steelwork Specification. BCSA.