Structural Steel is a vital building material that is defined by its shape, cross-section. Its mechanical and chemical properties differ from other types of steel products.


Structural Steel comes in a variety of shapes, including: beam, channel, angle, and as Hollow Structural Steel Tube (HSS). In the following article we will go into some detail about each type and the terminology surrounding each.


History of Structural Steel


Structural steel has been around over 100 years. Initially the standards and regulation of structural steel was quite lax. However, due to stringent research and testing over the course of the 20th century, engineers now have a very intimate knowledge of the properties and applications of structural steel.


Given the rapid rate of research surrounding structural steel, due to it’s obvious economic importance, each new generation of engineers has had to learn more than their predecessors.


Modern understanding of structural steel requires an understanding of structural stability and chemical composition of metals. For the purposes of this article, we will forego a lot of the science and chemical properties associated with structural steel.


Instead, we will be focusing on the types of structural steel available on the market, and each of their practical applications as well as key terminology.


Structural Beams


Depending on their shape, structural beams are also known as I Beams, H Beams or even W Beams. They are also often referred to as Rolled Steel Joists (RSJ).


These beams are commonplace structural support on various building projects. The ‘web’ (see diagram below) is what provides the resistance, whilst the flanges on either side are what prevent any bending motions.


  • Beam Depth
  • Flange Width
  • Web Thickness
  • Fillet Radius


Steel Channel


Steel Channel, also known as a C channel, is produced through a process known as Hot Rolling. This type of structural steel is available in a wide range of sizes and web thicknesses. Due to the structural strength it provides, Steel Channel is excellent for frames and bracing. Steel channels can be found anywhere from vehicles to construction sites.


Steel channel can be sub-divided further into four other types of channel:


  • Structural Channel – This type of steel channel is commonly used in the construction industry;
  • Ship & Car Channel – These channels have specific dimensions and sizes tailored to marine and automobile production;
  • Stair Stringer Channel – This type of channel was developed specifically for the construction of stair casings.
  • U-Channel – Finally, the smallest dimensions are reserved for U-channel or Bar channel steel.


  • Channel Depth
  • Flange Height
  • Web Thickness


Structural Angle


Structural angle is a steel bar with a 90-degree angle ‘L-shaped’ cross section. It is used in a variety of structural applications, as well as fabrication and repairs.


The curved part on the inside of the structural angle is called the fillet. The radius of the fillet is, unsurprisingly, known as the fillet radius.


The size of structural angle is usually expressed using the length and thickness of the leg (also known as the flange).


  • Leg Size
  • Leg Thickness
  • Fillet radius


HSS Rectangular  and Square Tube


  • Outside dimensions
  • Wall thickness


Hollow structural steel is used for a variety of purposes in a variety of industries. They are a crucial component of any construction job. These types of steel are good for compression column application.


Due to their shape and structure, hollowed structural steel is light-weight with high strength, which is uniformly distributed along the length of the steel.


These types of steel are particularly useful as braces due to their high resistance to torsional loading.  Their shape also facilitates reduced resistance to air and water flow.


HSS Round Tube


  • Outside dimensions
  • Wall thickness


Round tube hollowed structural steel is identical to square and rectangular tube with exception to the shape. Round tube is typically expressed as it’s outside dimensions (diameter) and it’s wall thickness.


Hollowed structural steel has excellent formability. It is also easier to fit parts that mate together with little notching,




Structural steel is a vital part of many industries, particularly in building and construction. Steel channel, angle and hollowed structural steel, each has important roles to play in the construction of a project. Knowing your terminology is key.

To find out more about structural steel, contact your local steel supplier to find out what would be appropriate for your project. Your steel supplier will also have an intimate knowledge of the different metallurgical steel types; which, as well as shape will have an impact of the effectiveness of the steel you use.