C & MC Channel Section Properties Quick Reference — AISC Channels

Quick-reference tables for C (American Standard) and MC (Miscellaneous) channel section properties per AISC. Properties include depth (d), flange width (bf), flange thickness (tf), web thickness (tw), cross-sectional area (A), moment of inertia (Ix), elastic section modulus (Sx), radius of gyration (rx), and plastic section modulus (Zx). All values from the AISC Steel Construction Manual, 16th Edition.

Channels are versatile structural shapes used for beams, columns, bracing, lintels, stair stringers, purlins, girts, and stiffeners. Their single-axis symmetry (C-shape with the web centered about the y-axis but offset about the x-axis) means the shear center does not coincide with the centroid, making channels prone to twisting under loads applied through the web. This must be accounted for in design.

Understanding Channel Properties

PRELIMINARY — NOT FOR CONSTRUCTION. All results are for educational and reference use only. Must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in any project.

C Channels — Section Properties

American Standard Channels (C-shapes) with tapered flanges. Sorted by nominal depth and weight.

MC Channels — Section Properties

Miscellaneous Channels (MC-shapes) with wider flanges than C channels. Sorted by nominal depth.

Source: AISC Steel Construction Manual, 16th Edition, Tables 1-5 and 1-6. All values in US customary units.

How to Select a Channel for Beam Design

Channel beams require careful consideration because of their single-axis symmetry:

1. Strong-axis bending: The x-x axis (parallel to the web). Use Ix and Sx for flexure checks. For a simply supported channel beam loaded through the shear center or with adequate torsional restraint: fb = M/Sx no greater than 0.66Fy (ASD) or phi*Mn = 0.90 * Zx _ Fy no greater than M (LRFD).

2. Weak-axis consideration: Channel beams loaded through the web (the typical case) will twist because the shear center is outside the section (left of the web for a standard C-shape). This induces torsion and warping. For beams loaded through the web, lateral bracing at closer intervals or a boxed configuration (two channels back-to-back) is required.

3. Lateral-torsional buckling: For unbraced channel beams, check LTB per AISC 360 Chapter F2 using the channel-specific Cb factor and Lp/Lr values.

4. Bearing at supports: Check web yielding and web crippling at bearing points per AISC J10 — the thinner tw of channels makes this more critical than for W-shapes of similar weight.

Channel Selection for Built-Up Members

Channels are commonly used in built-up configurations:

• Box column: Two C channels placed toe-to-toe and stitch-welded create a closed box section with excellent torsional resistance. Common for industrial columns where access to the interior for bolting is not needed.
• Cap channel on column: An MC channel placed on top of a W-shape column (cap plate detail) provides a wider bearing surface for supported beams and improves the column's weak-axis properties.
• Double channel strut: Two channels back-to-back with stitch bolts or continuous welds serve as chord members in trusses. The gap between channels allows gusset plates to pass through.

Frequently Asked Questions

What is the x-bar distance and why does it matter? The x (or x-bar) distance is the distance from the back of the web to the centroid of the channel. This is critical because: (1) The shear center is located outside the section at x + e where e is an additional eccentricity. (2) When a load is applied through the web, it produces a torsional moment of P * (x + e). (3) For connection design, the bolt group centroid relative to the channel centroid determines eccentricity moments. Always check torsional effects when loading a channel through its web.

Are channels more efficient than W-shapes? Generally, no. W-shapes are more efficient for flexure because they have a larger proportion of material in the flanges and are doubly symmetric (no torsion from symmetric loading). Channels carry approximately 30-40% less moment per pound than a comparable W-shape. However, channels are preferred where connection geometry demands a flat back surface (bolting to a wall, girt, or column face) or where the section must fit within a narrow width constraint.

How do I calculate the weight of a channel? Weight per foot is listed in the table above or can be calculated as A _ 3.40 lb/ft per in^2 of steel. Example: C12x20.7 has A = 6.08 in^2, so weight = 6.08 _ 3.40 = 20.7 lb/ft. Total weight for a 30 ft member = 30 * 20.7 = 621 lbs.

What steel grade are channels available in? C channels are typically ASTM A36 (Fy = 36 ksi). MC channels can be A36 or ASTM A529 Gr 50 (Fy = 50 ksi). In the AISC Manual, properties are the same for both grades (E, geometry unchanged), but the capacity calculations differ. Always verify the mill cert to confirm grade before using Fy = 50 ksi assumptions.

Can I use channels as columns? Yes, but single channels are extremely weak about the y-y axis (ry is very small — typically 0.7-1.1 inches) and are torsionally unstable. A single channel column should be used only for very short lengths (KL less than 6 ft) with light axial loads. For column applications, use two channels laced or battened together, or use a W-shape or HSS section instead.

Try it now: Calculate channel section properties with our free tool

Related Pages

• Channel Sizes Chart — Complete C and MC channel database
• Steel Angle Properties — Equal and unequal leg angle properties
• Purlin and Girt Design — Channel purlins for metal building systems
• Steel Beam Span Guide — Span tables for W-shapes and channels
• Beam Capacity Calculator

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.

Design Resources

Calculator tools

• Beam Capacity Calculator
• Section Properties Lookup
• Steel Weight Calculator

Design guides

• Steel Lintel Design
• Metal Building Purlin Design
• Built-Up Column Design