How to Read Steel Section Tables -- W, HSS, C, L Properties Decoded

Every structural engineer encounters a steel section table within their first week on the job. The dense grid of numbers — depth, flange width, web thickness, area, moments of inertia, section moduli, radii of gyration — can be intimidating for a beginner. Yet knowing how to read steel section tables is an essential skill that underpins every beam design, column check, and connection calculation you will ever perform.

Dimension columns: d, bf, tf, tw

The first columns in any steel section table list the physical dimensions. The depth (d) is the overall height of the cross-section, driving moment of inertia and architectural clearance. The flange width (bf) affects lateral stiffness and bearing area for connections. Flange thickness (tf) and web thickness (tw) control compactness limits and shear capacity.

Section property columns: A, Ix, Sx, Zx, rx, ry

The area (A) is used directly for axial tension, compression, and self-weight. The moment of inertia (Ix, strong axis) governs deflection and flexural buckling. The elastic section modulus (Sx) gives the yield moment My = Fy _ Sx. The plastic section modulus (Zx) gives the plastic moment Mp = Fy _ Zx, used for LRFD flexural design. The radii of gyration (rx, ry) are critical for slenderness KL/r in column buckling checks.

Torsion properties: J and Cw

The torsional constant (J) is small for open sections like W-shapes and large for closed sections like HSS. The warping constant (Cw) affects lateral-torsional buckling resistance.

Shape prefixes

• W — Wide-flange, parallel flange faces (beams and columns)
• S — American standard beam, tapered flanges (largely superseded)
• HP — Bearing pile section (piles and short columns)
• C — Standard channel (bracing, girts, light framing)
• L — Angle (bracing, truss members, connections)
• HSS — Hollow structural section (columns, trusses)
• WT — Structural tee (truss chords, lintels)

Common mistakes

Confusing Sx and Zx gives approximately 10-15% lower capacity in LRFD checks. Using the wrong axis (Ix vs Iy) produces errors of 10x or more. Ignoring ry — the weak-axis radius of gyration is the critical parameter for column and lateral-torsional buckling. And the nominal depth in the designation is approximate: a W21x50 is actually 20.83 in deep.

Educational reference only. Verify all section property values against the current edition of the governing design code.

Try It Yourself

Ready to try this yourself? Use our free Moment of Inertia Calculator. Look up Ix, Sx, Zx, rx, J, and Cw for any standard steel section with cross-code comparison across AISC 360, AS 4100, EN 1993, and CSA S16.