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.

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).

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).

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.

Section efficiency comparison

Bending efficiency (Zx per unit weight)

Deeper W-shapes are the most efficient for pure flexure. HSS sections sacrifice bending efficiency for torsion, biaxial capacity, and aesthetics. Angles are inefficient in flexure but cheap and simple for bracing.

Compression efficiency (r_x per unit weight)

HSS sections have equal r_x and r_y, making them ideal for columns where buckling about both axes is a concern. W-shapes are strong-axis dominant; weak-axis bracing is often required.

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.

Cross-code equivalent section types

Section dimensions differ between standards. A W21x44 is not identical to a 530UB82 — check actual properties, not just nominal depth.

Code classification of section slenderness

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.

Compact/non-compact limits for common shapes (Fy = 50 ksi)

Most standard W-shapes are compact for Fy = 50 ksi. Only very light sections (W12x14, W14x22) may have non-compact flanges.

Connection implications by section type

HSS connections are the most expensive due to slotting, welding access, and the need to seal the interior against corrosion. Factor connection cost into section selection.

Common mistakes to avoid

1. Using HSS for long-span beams. HSS is inefficient in pure flexure compared to W-shapes because material is distributed equally around the perimeter instead of concentrated in the flanges.
2. Ignoring shear center eccentricity in channels. Loading a channel through its web (not the shear center) induces torsion that can reduce effective bending capacity by 20-40 percent.
3. Selecting WT sections for flexure without checking stem buckling. The WT stem in compression buckles locally. AISC 360 Section F9 limits WT flexural capacity well below what the plastic modulus suggests.
4. Assuming angle members are axially loaded. Truss angles connected through one leg have significant eccentricity. AISC 360 Section E5 slenderness modifications can increase effective KL/r by 30-50 percent over the geometric value.
5. Not checking HSS wall slenderness. Thin-walled HSS sections (e.g., HSS10x10x3/16) may be slender, requiring effective area reduction per AISC 360 Table B4.1a. This can reduce compression capacity by 10-20%.
6. Specifying non-standard depths. W44 and W36 shapes are less readily available than W24 and W21. Check mill rolling schedules and regional availability before specifying heavy/odd sections.

Frequently asked questions

What is the most efficient section type for a beam? A deep W-shape (W33, W36, W44) provides the highest Zx per unit weight. For typical building floors, W21 to W27 is the sweet spot of efficiency, availability, and depth constraints.

When should I use HSS instead of W-shapes? Use HSS when: (1) torsion governs, (2) you need equal strong and weak axis properties (columns with biaxial bending), (3) the steel is architecturally exposed and a clean rectangular or round profile is desired, or (4) the member is a bracing diagonal where connections are simple gusset plates.

What is the difference between W-shapes and S-shapes? W-shapes have parallel inner and outer flange surfaces. S-shapes (American Standard beams) have tapered inner flange surfaces (16.7% slope). W-shapes are the modern standard; S-shapes are rarely used in new construction.

Can I use HP sections as building columns? Technically yes — HP sections have approximately equal flange width and depth, making them nearly square in profile. They are heavy for their depth compared to W-shapes. Use HP sections as columns only when their robust cross-section is specifically needed (e.g., high-impact industrial settings, blast resistance).

What is a built-up section? A member fabricated from plates (plate girder) or multiple standard shapes (double angle, double channel). Built-up sections are used when no rolled shape meets the required capacity or when specific geometric properties are needed. Cost per ton is 2-3x rolled shapes.

How do fire protection requirements vary by section type? Fire protection cost is proportional to surface area. HSS sections have the lowest surface area per unit weight (most economical to protect). W-shapes have more surface area (higher protection cost). Open sections like angles and channels have the most surface area per unit weight.

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Steel Shape Comparison Table

The table below compares all major structural steel shape designations, their key properties, and distinguishing characteristics.

When to Use Each Shape Type

Selecting the right shape for the application is fundamental to efficient structural design. The following guide matches shapes to their most appropriate structural roles.

Shape Availability and Cost Comparison

Not all shapes are readily available from service centers. Specifying scarce shapes causes delays and cost premiums. The table below ranks shapes by availability and relative cost.

Cost-saving tip: Specifying W-shapes wherever possible reduces both material and fabrication costs. W-shapes benefit from the highest production volumes and the widest availability, translating to the lowest per-pound cost in the structural steel market.

Related references

• HSS Section Properties
• Steel Angle Sizes
• Steel Material Properties
• Steel Grade Selection
• HSS Connections
• Beam Sizes
• Column Design
• Steel Pipe Schedule Chart
• How to Verify Calculations

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 this information.