What is structural steel?

We, Neil’s Steels, are a specialist steel fabricators based on the south coast that specialise in structural steel. We’ve worked in the area for over 30 years and our expertise is renowned. But what is structural steel? Read the short overview below and hopefully you’ll be a bit more clued up! We’ll cover what it is, where it is used and what the most popular steel sections are.

Cowfold fabricated structural steel

Structural steel

In essence, structural steel is defined as steel shaped for use in construction for building purposes. There are a few variants of the type of steel we work with, a large part of which is determined by which process we roll the steel with (hot or cold). If you aren’t familiar with what hot and cold rolled steel are, click here.

Having high strength, stiffness, toughness, and ductile properties, structural steel is one of the most commonly used materials in commercial and industrial building construction.

Many structural steel shapes take the form of an elongated beam having a specific cross-section profile. Structural steel shapes, sizes, chemical composition, mechanical properties such as strengths, storage practices, etc., are regulated by government mandated standard in most fully industrialized countries.

Steel can be cast, molded, shaped or beaten into nearly any shapes you could require. There are usually either bolted or welded together in construction, as it would be almost impossible to transport a fully built frame. Structural steel can be erected as soon as the materials are delivers on-site, whereas materials such as concrete must be cured at least 1-2 weeks after pouring before construction can continue, making steel a time-economic construction material.

The density of steel varies based on the alloying constituents but usually ranges between 7,750 and 8,050 kg/m3.

Common steel shapes

UC – universal column or UB – universal beam. In Europe it includes the IPE, HE, HL, HD, and other sections; in the US it includes Wide Flange (WF or W-Shape) and H sections). Universal columns are the most often used sections for structural steel purposes. Unlike a universal beam, the UC’s width is roughly equal to their depth. For example, a 152 UC 23 is 152 mm wide and 152 mm deep and 152*89 UB 16 is 89mm wide and 152mm deep. The last number (23 in this example) is the weight per meter in kilograms. It is therefore easy to work out what the total weight of a UC is by simply multiplying its weight per meter by the total length in meters. Universal columns are mainly used for columns, however, their small depth compared to universal beams make them ideal load bearing members when height is limited.

Structural channel – PFC. Parallel flange channel is normally called a channel or a “C-section”. They are described by their depth, width and weight per meter in kilograms, eg. 150 x 75 x 18 PFC. The PFC is used for columns, lintels above doors or simply a beam supporting floor joists. When used for lintels, they have a bottom plate welded to it that takes the outer bricks or 2 channels are bolted back to back with 100 mm spacers to support both leaves of a cavity wall.

Equal angle (L-shaped cross-section) – RSA-e (equal) and RSA (unequal). Rolled steel angle – equal is normally called an “angle”, “equal angle” or “L-shape”. Even though both legs are the same length, they are described by giving both leg lengths and the wall thickness (all in mm), eg. 100 x 100 x 12 RSA. For structural steel purposes, equal angles are often used for brackets for cleat connections. Sometimes they are also used as lintels (2 angles bolted back to back).

Unequal angle – unequal is called “angle” or “L-shape”. They are described by giving both leg lengths (longer first) and the wall thickness (all in mm), eg. 150 x 100 x 8 RSA. With the longer leg being in a vertical position, its loading capabilities are greater than equal angles, therefore they are often used as lintels. Unequal angles are also used as brackets for cleat connections. Both types of angles are often used for balconies, platforms, stairs, concrete supports, etc.

HSS-Shape – (Hollow structural section, also known as SHS (structural hollow section), including square, rectangular RHS, circular CHS (pipe). Hollow sections are often used as columns, they are not commonly used as beams due to the shape that makes it difficult to bolt to other beams. For example, if you have 100 x 100 x 10 SHS, the column will be 100 mm deep, 100 mm wide and 10 mm thick. Circular hollow sections are used as columns and braces in portal frames structures. For example, 114.3 x 5 CHS, has a diameter of 114.3 mm and the wall is 5 mm thick.

Plate- FLT, metal sheets thicker than 6 mm or 1⁄4 in. Flat sections are used anywhere where a connection between 2 beams is required. They are used for base plates, end plates, stiffeners, gussets, tabs, splice plates and many more. In some cases, they add strength to a beam when welded along the length of a beam (top or bottom). Flat sections are described by its width and thickness, eg. 200 x 12 Flat (both in mm). When a flat section is cut into smaller pieces, then they are called “plates”. Sometimes flat sections are used to reinforce timber joists (“flitch beam”) by bolting it to the joist every 400 – 600 mm.

Did you know?

Why 152mm is the number in cross section rather than 150 mm? In the United Kingdom, these steel sections are commonly specified with a code consisting of the major dimension where all measurements being metric. Therefore, a 152x152x23UC would be a column section (UC = universal column) of approximately 152 mm (6.0 in) depth 152 mm width and weighing 23 kg/m (46 lb/yd) of length. So, the metric number comes from inches.

Browse our website to learn more about steel profiles: sections, connections, structures and finishes. If you are looking for any other type of steel fabrication, consider contacting our sister company J. Colburn.

2 thoughts on “What is structural steel?

  1. Marcus says:

    Worker safety should be paramount for companies, but that’s not always the case. Some of the scariest moments in a structural steel shop occur when very large plates are handled sloppily. That led to an important lesson. When picking up a plate, lay the plate down and use spreader chains with bent plates on the chains to grab all four edges. Do not use hooks on the ends of chains to move plate, and do not use clamps on painted material to avoid paint buildup.

    • Jack Maile says:

      Absolutely Marcus, we couldn’t agree more. Usually these lessons can be passed on from one generation to another, but unfortunately some lessons have to be learnt the hard way.

Leave a Reply

Your email address will not be published. Required fields are marked *