C Channels

C channels, also known as C beams or structural channels, are standardized by international organizations such as AISC, CEN, and ISO to ensure uniformity and compatibility across industries. These structural beams with a C-shaped cross-section are primarily used in construction, engineering, and industrial applications due to their ability to resist bending and shear forces. The load-bearing capacity, moment of inertia, and section modulus are crucial factors in determining the performance and suitability of C channels for specific applications, requiring careful structural analysis and calculations.

C Channel Sizes

Designation W [lb/ft] A [in^2] d [in] bf [in] tw [in] tf [in] Ix [in] Sx [in]
C15X50 50.0 14.7 15.0 3.72 0.716 0.650 404 53.8
C15X40 40.0 11.8 15.0 3.52 0.520 0.650 348 46.5
C15X33.9 33.9 10.0 15.0 3.40 0.400 0.650 315 42.0
C12X30 30.0 8.81 12.0 3.17 0.510 0.501 162 27.0
C12X25 25.0 7.34 12.0 3.05 0.387 0.501 144 24.0
C12X20.7 20.7 6.08 12.0 2.94 0.282 0.501 129 21.5
C10X30 30.0 8.81 10.0 3.03 0.673 0.436 103 20.7
C10X25 25.0 7.35 10.0 2.89 0.526 0.436 91.1 18.2
C10X20 20.0 5.87 10.0 2.74 0.379 0.436 78.9 15.8
C10X15.3 15.3 4.48 10.0 2.60 0.240 0.436 67.3 13.5
C9X20 20.0 5.87 9.00 2.65 0.448 0.413 60.9 13.5
C9X15 15.0 4.40 9.00 2.49 0.285 0.413 51.0 11.3
C9X13.4 13.4 3.94 9.00 2.43 0.233 0.413 47.8 10.6
C8X18.75 18.75 5.51 8.00 2.53 0.487 0.390 43.9 11.0
C8X13.75 13.75 4.03 8.00 2.34 0.303 0.390 36.1 9.02
C8x11.5 11.5 3.37 8.00 2.26 0.220 0.390 32.5 8.14
C7X14.75 14.75 4.33 7.00 2.30 0.419 0.366 27.2 7.78
C7X12.25 12.25 3.59 7.00 2.19 0.314 0.366 24.2 6.92
C7X9.8 9.80 2.87 7.00 2.09 0.210 0.366 21.2 6.07
C6X13 13.0 3.82 6.00 2.16 0.437 0.343 17.3 5.78
C6X10.5 10.5 3.07 6.00 2.03 0.314 0.343 15.1 5.04
C6X8.2 8.20 2.39 6.00 1.92 0.200 0.343 13.1 4.35
C5X9 9.00 2.64 5.00 1.89 0.325 0.320 8.89 3.56
C5X6.7 6.70 1.97 5.00 1.75 0.190 0.320 7.48 2.99
C4X7.25 7.25 2.13 4.00 1.72 0.321 0.296 4.58 2.29
C4X6.25 6.25 1.84 4.00 1.65 0.247 0.296 4.19 2.10
C4X5.4 5.40 1.58 4.00 1.58 0.184 0.296 3.85 1.92
C4X4.5 4.50 1.34 4.00 1.52 0.125 0.296 3.53 1.77
C3X6 6.00 1.76 3.00 1.60 0.356 0.273 2.07 1.38
C3X5 5.00 1.47 3.00 1.50 0.258 0.273 1.85 1.23
C3X4.1 4.10 1.20 3.00 1.41 0.170 0.273 1.65 1.10
C3X3.5 3.50 1.09 3.00 1.37 0.132 0.273 1.57 1.04

C Channel Basics

Standardization and Specifications

C channels, also known as C beams or structural channels, are standardized by various international organizations, including the American Institute of Steel Construction (AISC), the European Committee for Standardization (CEN), and the International Organization for Standardization (ISO). They determine the standard sizes, classifications, material specifications, and tolerances for C channels, ensuring uniformity and compatibility across industries. For example, AISC maintains the manual of steel construction that details various standardizations and specifications.

Definition and Characteristics

C channels are structural beams with a C-shaped cross-section. They are primarily used in construction, engineering, and industrial applications because of their ability to resist bending and shear forces. The cross-section consists of three flat surfaces – a top flange, a web, and a bottom flange. The web connects the flanges, providing stability and strength to the channel. C channels can be classified into the following types based on their dimensions:

  1. Imperial Channels: These channels use the imperial system for dimensions and are dominant in countries like the United States.
  2. Metric Channels: These channels use the metric system for dimensions and are primarily prevalent in European countries.

The dimensions and properties of C channels include:

  • Depth
  • Weight per Unit Length
  • Web Thickness
  • Flange Width
  • Flange Thickness
  • Cross-Sectional Area
c channel specifications

Material Composition

C channels are typically made from various grades of steel, chosen for their specific strength and corrosion resistance properties. For applications requiring increased corrosion resistance, stainless steel C channels are also available.

While the majority of C channels are manufactured from steel, other materials like aluminum and fiberglass reinforced plastic (FRP) may be used for specific applications where lighter weight or non-metallic properties are essential

C Channel Load Bearing Capacity

Load-Bearing Capacity

The most important factor when designing a C channel is the determination of its load-bearing capacity. This refers to the ability of the C channel to support vertical loads, such as the weight of materials placed upon it, without deformation or failure. The load-bearing capacity of a C channel is determined by its material properties, cross-sectional dimensions, and the type of load being applied (e.g., concentrated loads, distributed loads, or combinations thereof).

Based on these factors, it is essential to perform structural analysis and calculations in order to ensure that the designed C channel can adequately support the intended service loads. Some of the key calculations in determining load-bearing capacity include the calculation of shear stress, bending stress, and deflection. It is also essential to consider factors such as lateral-torsional buckling and local buckling in order to accurately determine the load-bearing capacity of the C channel.

C Channel Moment of Inertia

The moment of inertia (MOI) determines a C channel’s resistance to bending and deflection.

The moment of inertia of a C channel can be derived from its basic dimensions: height (h), web thickness (t_w), and flange width (b). It is quantified in units of length^4 . To understand the MOI effectively, it is crucial to emphasize that it must be specified with respect to a chosen axis of rotation.

For C channels, the primary axis of rotation is the centroidal axis. There are two principal moments of inertia – one along the x-axis (Ix) and another along the y-axis (Iy). The MOI along the x-axis is significant for engineering applications, as it directly correlates with the channel’s bending resistance.

To calculate the moment of inertia for a C channel, one can use the parallel axis theorem. This method involves splitting the C channel into three rectangular sections, finding their individual MOI, and summing them up. The moment of inertia (I) for each section can be determined using the equation:

moment of inertia for rectangle

For a C channel with known dimensions, the overall MOI can be calculated by adding the individual MOIs and accounting for the distance between each section’s centroid and the overall centroidal axis using the parallel axis theorem. The equation becomes:

c channel moment of inertia parallel axis theorem

where:

  • IA, IB, IC are the moments of inertia for each section
  • AA, AB, AC are the cross-sectional areas of each section
  • dA, dB, dC are the distances from each section’s centroid to the overall centroid
c channel moment of inertia calculation

An alternative method is to calculate the MOI by using a composite area approach. In this method, instead of splitting the C channel into rectangles, one derives the MOI by subtracting the MOI of an inner rectangular section from that of an outer rectangular section. This approach is more time-efficient than the parallel axis theorem method and provides an equivalent result.

The equation for calculating the C channel moment of inertia with this approach is:

c channel moment of inertia composite approach

where

  • B = flange width
  • H = overall height
  • b = flange width minus web thickness
  • h = web height, or overall height minus 2x the flange thickness

C Channel Section Modulus

The C channel section modulus is another essential engineering parameter to determine the section’s capacity to withstand stresses and loads.

The section modulus (S) for a C channel can be computed using the following formula:

c channel section modulus formula
c-channel section modulus

When selecting a C channel for a specific application, it is essential to compare the section modulus with the application’s required section modulus, considering factors like force, span length, and material properties.

The specifications for C channels often include their corresponding section modulus values for ease of reference, making it convenient for engineers and designers to select the appropriate member for their project requirements.

Scroll to Top
Complete... 50%
Please enter your name and email address below to receive a link to the ebook.

You’ll also receive regular tips to help you master Excel for engineering.

FREE EBOOK:

10 SMARTER WAYS TO USE EXCEL FOR ENGINEERING

By Charlie Young, P.E.

Take your engineering to the next level with advanced Excel skills.