The ABCs of Structural Steel

Structural Steel is an important building material characterized by its shape and cross-section, as well as its mechanical and chemical qualities.

Structural Angle

Structural Angle Terms

Leg (Flange) Size: The measurement of each leg (see “A & B” in diagram).
Leg (Flange) Thickness: The thickness of the leg (“C”).
Other terms: Fillet radius: The curved portion, where the inside transition between the web and flange occurs is called a fillet. The radius of the fillet is called the fillet radius (not always provided)

Structural Angle is a steel bar that has an L-shaped cross section. It is a piece of structural iron or steel in the form of a 90 degree angle. It is ideal for all structural applications, general fabrication and repairs. This item can have equal sized legs (or flanges); this is typically known as equal leg angle. Legs (or flanges) that are differently sized are typically known as unequal leg angle.

The size measurement of structural angle is commonly specified using the length of each leg (flange) and the thickness of the leg (flange). Dimensions in North America are typically in inches and in the UK, millimeters.

Hollow Structural Steel Tube

HSS Rectangular Tube and Square Tube Terms

Outside Dimensions: The outer measurement of each side (see “A & B” in the diagrams below).
Wall Thickness: The thickness of the tube wall (“C”).

HSS Round Tube Terms

Outside Diameter: The measurement of the outer diameter of the tube (see “A” in the diagram below).
Wall Thickness: The thickness of the tube wall (“B”).

Hollow Structural Steel (HSS) Tubing has become an essential component of the construction industry. It is also used to a great extent in the fabrication of enclosures, automobiles and many other structural applications. HSS Tubes are produced in three shapes – round, square and rectangular.  They are available in a broad range of sizes and gauges. Some of the benefits of HSS Tube are:

• A high strength-to-weight ratio (less weight-per-foot)
• Uniform strength
• High resistance to torsional loading (excellent choice for bracing)
• Increased formability
• Less resistance to air or water flow
• Easier in fitting mating parts together (no notching)
• Particularly well suited for compression column applications

HSS Tube is commonly specified using the outside size measurements and the tube wall thickness (square tube example: 2.000” x 2.000″ x 0.250” wall / round tube example: 3.000” Dia. x 0.250” wall).

Structural Beams

Structural Beams come in various shapes and sizes so it is important to use the correct terminology when measuring.

Beam Terms

Beam Depth: The distance from the top and bottom surface of the steel (see “A” in diagram).
Flange Width: The top and bottom flat horizontal sections width (“B”).
Flange Thickness: The thickness of the top and bottom flat horizontal sections (“C”).
Web Thickness: The thickness of the vertical center section of a steel beam (“D”).
Fillet radius: The curved portion, where the inside transition between the web and flange occurs is called a fillet. The radius of the fillet is called the fillet radius (not always provided).

Structural Beams are also known as I Beams or H Beams, and W Beams for the wider flanged versions. Some construction companies refer to them as Universal Beams or Rolled Steel Joists (RSJ). Typically they are used in the construction of buildings for structural support.  The part of the Structural Beam that provides resistance to shear forces (breaking, tearing apart, or collapsing) is the web, while the flanges resist the bending movement of the section.

In the United Kingdom, Universal Beams or Columns are commonly specified with a code consisting of the depth (the measurement taken from the outer face of the first flange, to the outer face of the opposite flange), the flange width and the kilograms per metre. The code can end with the section type (Such as UB – Universal Beam or UC – Universal Column). All measurements are in metric. Therefore a 152x152x23UB would be a Universal Beam of approximately 152 millimeters in depth x 152 millimeters in width and weighing approximately 23 kilograms per metre.

In Canada and the United States, steel I-beams are commonly specified using the depth (in inches) and weight of the beam (in pounds per foot). For example, a “4 x 13” I-beam is approximately 4 inches in depth (the measurement taken from the outer face of the first flange, to the outer face of the opposite flange). This channel would weigh approximately 13 pounds per foot (note that wide flange beams can often vary from the mill listed depth measurement).

In Canada, certain steel I-beams may be available in metric, and while depth and weight of the beam are in metric terms, the way they are measured is very similar.  An example would be a “W250x33” beam which is approximately 250 millimeters in depth and weighs approximately 33 kg per metre.

Structural Channel

Channel Terms

Channel Depth: The distance from the top and bottom surface of the steel (see “A” in diagram).
Flange Height: The top and bottom flat horizontal sections (flanges) width (“B”).
Web Thickness: The thickness of vertical center section of a channel (“C”).
Fillet radius: The curved portion, where the inside transition between the web and flange occurs is called a fillet. The radius of the fillet is called the fillet radius (not always provided).

Steel Channel is a Hot Rolled product (typically grade ASTM A36). When looking at a cross section it has a vertical web with horizontal top and bottom flanges. It comes in a wide varying range of sizes and web thicknesses. The shape of this type of product provides a great amount of structural strength, making it an ideal product for making frames and bracing. Typically it is used in the manufacturing of machinery, enclosures and vehicles. It is also used in the construction of buildings for structural support. The Structural Channel, also known as a C-Channel is distinguished from I-beam or H-beam or W-beam which has flanges on both sides of the web.

In the UK, steel channel (or C-section) can also be called parallel flange channel. They are measured very similarly to universal beams: the depth, the flange width and the kilograms per metre.

In the Canada and the United States, steel channels are commonly specified using the depth (in inches) and weight of the channel (in pounds per foot). For example, a “6 x 13” channel is approximately 6 inches in depth and weighs approximately 13 pounds per foot.

The only exception to the above method in channel measurement would be U-Channel or Bar Channel, which are measured by the depth, then the flange height, and lastly the web thickness. Dimensions in North America are typically in inches and in the UK, millimeters.

Steel Channel has the following categories:

• Structural Channel – Used in varied construction and manufacturing projects.
• Ship & Car Channel – A set of sizes that were developed for the use in the construction of Marine Vessels and Automobiles.
• Stair Stringer Channel – A set of sizes that were developed for the use in the construction of Stair Casings
• U-Channel or Bar Channel – A set of smaller channel sizes (Depth – 0.750” minimum to 2.500” maximum).