Steel Section Types — W, HSS, Angle, Channel, WT & Plate

Structural steel section types: W-shapes, HSS, angles, channels, WT tees, HP piles, and plates. When to use each, efficiency comparison, and cross-code equivalents.

Why section type matters

The choice of section type affects bending efficiency, connection detailing, local buckling classification, fire protection cost, and aesthetic expression. A W-shape is the default for beams and columns, but HSS tubes may be preferred for architecturally exposed steelwork, angles dominate truss web members, and channels suit stringer applications. Selecting the wrong section type leads to heavier designs, awkward connections, or fabrication premium.

Section families

W-shapes (wide flange)

The workhorse of structural steel in North America. Designated by nominal depth and weight per foot (e.g., W14x82 is approximately 14 inches deep, 82 lb/ft). W-shapes have parallel flanges and are hot-rolled per ASTM A6. Available in depths from W4 to W44. Efficient for flexure because most material is in the flanges, far from the neutral axis.

Bending efficiency metric: Zx / (weight per foot). A W21x44 achieves Zx = 95.4 in^3 at 44 lb/ft, giving a ratio of 2.17 in^3 per lb/ft. Compare with W14x48 at Zx = 78.4 in^3 and ratio 1.63 — the deeper section is 33 percent more material-efficient in flexure.

International equivalents: UB/UC (Australia/UK per AS/NZS 3679), IPE/HEA/HEB (Europe per EN 10025), W/WWF (Canada per CSA G40.20).

HSS (Hollow Structural Sections)

Square, rectangular, and round tubes. Excellent torsional resistance and biaxial bending capacity. Designated as HSS8x8x1/2 (square, 8 in x 8 in, 0.5 in wall) or HSS8.625x0.500 (round, 8.625 in OD, 0.5 in wall).

Key advantages: closed cross-section resists torsion efficiently, aesthetically clean for exposed structures, good compression capacity due to low KL/r in both axes. Key disadvantages: connections require slotted gusset plates or through-plates, wall slenderness limits govern for thin-wall sections per AISC 360 Table B4.1a, and internal corrosion protection is difficult.

Angles (L-shapes)

Single angles are used for truss web members, bracing, lintels, and miscellaneous framing. Double angles (back-to-back) serve as truss chords and light beam-column members. Designated by leg lengths and thickness (e.g., L4x3x3/8).

Important: single angles loaded through one leg experience combined bending and axial load due to eccentricity. AISC 360 Section E5 provides specific provisions for single-angle compression members. The effective slenderness ratio includes an eccentricity modification.

Channels (C and MC)

C-shapes have parallel flanges with the web offset to one side, creating an asymmetric section. Used for stair stringers, wall studs, stiffeners, and built-up members. Designated as C12x20.7 (American Standard) or MC12x10.6 (Miscellaneous Channel).

The shear center of a channel is outside the web, so transverse loads applied through the web induce torsion. For beams, channels must be braced or loaded through the shear center to avoid twisting.

WT (structural tees)

Cut from W-shapes by splitting along the web. WT7x41 is half of a W14x82. Used for truss chords (stem acts as gusset plate connection surface), hangers, and cap members. Bending capacity is limited because the stem is prone to local buckling in compression. AISC 360 Section F9 covers flexure of tees.

HP (bearing piles)

Wide-flange shapes with approximately equal flange width and depth, designed for pile driving. HP14x89 is a common heavy pile section. Flanges and web have nearly the same thickness to resist driving stresses. Not typically used as building columns, but occasionally repurposed where high axial capacity and robustness are needed.

Worked example — section selection for a 9 m beam

A simply supported floor beam spans 9 m (29.5 ft), supporting a factored UDL of 45 kN/m (3.08 kip/ft). Lateral bracing at third points (Lb = 3 m = 9.84 ft). Steel grade A992 (Fy = 345 MPa, 50 ksi).

Required moment capacity: Mu = wL^2/8 = 45 x 9^2 / 8 = 456 kN-m (4,037 kip-in).

Option A — W-shape: W18x40 has phiMp = 0.9 x 50 x 78.4 = 3,528 kip-in. Not enough. W21x44 gives phiMp = 0.9 x 50 x 95.4 = 4,293 kip-in. Check LTB with Lb = 9.84 ft: Lp = 5.36 ft, Lr = 15.5 ft, so Lb is between Lp and Lr — inelastic LTB governs. With Cb = 1.14 for uniform load, phi*Mn = 4,100 kip-in. Adequate.

Option B — HSS: HSS12x8x1/2 has phi*Mp = 3,420 kip-in on strong axis. Insufficient. HSS14x10x1/2 provides 4,260 kip-in and weighs 68 lb/ft vs 44 lb/ft for the W21x44. The W-shape uses 35 percent less steel.

Conclusion: W-shapes are the most weight-efficient choice for simple beams. HSS becomes competitive only where torsion or biaxial bending governs, or where connection simplicity and aesthetics justify the weight premium.

Code classification of section slenderness

Classification AISC 360 AS 4100 EN 1993 CSA S16
Compact / Class 1 Table B4.1b (lambda <= lambda_p) Cl. 5.2.2 (compact) Table 5.2 (Class 1 plastic) Table 2 (Class 1)
Non-compact / Class 2 Table B4.1b (lambda_p < lambda <= lambda_r) Cl. 5.2.3 (non-compact) Table 5.2 (Class 2) Table 2 (Class 2)
Slender / Class 3-4 Table B4.1b (lambda > lambda_r) Cl. 5.2.4 (slender) Table 5.2 (Class 3/4) Table 2 (Class 3/4)

Compact sections can develop full plastic moment Mp. Non-compact sections can reach yield stress Fy in extreme fiber but not full plasticity. Slender sections buckle locally before yielding.

Common pitfalls

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Related references

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.