Structural Steel Shapes: I-Beams, Channels, Angles, and Tube

Standard Structural Shapes

Structural steel comes in standardized shapes that are efficient for carrying loads. Understanding these shapes helps you design structures and communicate with fabricators.

Wide Flange Beams (W-Shapes)

The classic “I-beam.” Wide, parallel flanges connected by a web. Designated like: W12×26 (approximately 12″ deep, 26 lbs per foot).

• Use: Building columns, bridge girders, crane beams — anywhere you need to span a distance or support a load
• Advantage: Efficient use of material — most metal is in the flanges where bending stress is highest
• Material: Usually A992 (Fy = 50 ksi)

Standard Beams (S-Shapes)

Older I-beam design with tapered flanges (thicker at the web). Being phased out in favor of W-shapes but still available. Designated: S10×25.4.

Channels (C-Shapes)

Half an I-beam — one flat side. Designated: C8×11.5 (8″ deep, 11.5 lbs/ft).

• Use: Frames, brackets, supports, stair stringers
• Note: Asymmetric — loads cause twisting unless braced or paired back-to-back

Angles (L-Shapes)

Two legs at 90°. Equal leg (L3×3×1/4) or unequal (L4×3×3/8).

• Use: Bracing, framing, lintels, shelf supports, connections
• The most versatile structural shape — every fab shop has a pile of angle iron

Hollow Structural Sections (HSS)

Square, rectangular, or round tube. Designated by outside dimensions and wall thickness: HSS 4×4×1/4.

• Square/Rectangular tube: Frames, columns, truck beds, guard rails, furniture
• Round tube: Columns, roll cages, handrails, bicycle frames
• Advantage: Excellent torsional strength, clean appearance, easy to weld from any direction
• Material: Usually A500 Grade B (Fy = 46 ksi) or Grade C (Fy = 50 ksi)

Plate, Bar, and Flat Stock

• Plate: Flat steel ≥ 3/16″ thick. Hot rolled. A36 or A572-50.
• Bar: Round, square, hex, or flat. Hot rolled or cold finished (more precise).
• Flat bar: Rectangular cross-section. Used for brackets, stiffeners, base plates.

Pipe

Designated by Nominal Pipe Size (NPS) and schedule (wall thickness). NPS 2 Schedule 40 has an OD of 2.375″ and wall of 0.154″.

• Schedule 40: Standard weight — general structural and pressure
• Schedule 80: Extra heavy — higher pressure, more strength
• Note: Pipe sizes are NOMINAL — a 2″ pipe is not 2″ in any measurable dimension

Selecting the Right Shape

Need structural fabrication? Send us your design — we’ll source material and fabricate to your spec.