Structural Steel: Types, Benefits & Applications

Structural steel is a very common construction material used in many everyday applications, particularly in infrastructure and building. With a wide variety of shapes and material compositions, structural steel caters to countless use scenarios.

Structural steel is primarily used in the construction industry, where it is used for beams and frames for bridges or large structures such as buildings. Structural steel is cost-effective and recyclable, allowing for production at scale and long-term sustainable construction. 

If you are venturing into the steel industry or are looking for a structural steel fabrication company, you’ll find everything you need to know about structural steel in this article. 

You’ll learn the common types of structural steel, their applications, pros and cons of stainless steel, common grades and compositions of steel used for structural applications. 

Let’s get started!

What Is Structural Steel?

Structural steel refers to steel products that are used primarily in the construction industry. Structural steel is fabricated in many different shapes, including beams, plates and channels. Steel of various compositions is used in fabricating structural steel. 

Structural steel is arguably one of the most important construction materials due to its strength, versatility, sustainability, availability, and relatively low cost. The ductility of structural steel allows for the creation of various predetermined and customised shapes to satisfy particular construction requirements. That’s why structural steel is one of the key applications of steel fabrication. 

Structural steel conforms to specific standards set forth and regulated by varying entities and government agencies across different countries. In Australia, the steel industry conforms to these through the Australian Standards and Codes of Practice. Among these standards for steel are AS 4100 (for structural steel design) and AS/NZS 4600 (for the design of cold-formed steel structures), among others. 

These standards are fine-tuned to ensure mechanical properties, chemical compositions, methods of manufacture, quality control provisions, and tolerances of structural steel. In summary, Australia’s steel and steelwork frameworks require conformity to design, material, and execution standards to ensure the safety and reliability of construction projects built with structural steel.

What Are the Advantages & Disadvantages of Structural Steel?

The many advantages of structural steel, such as its high strength and low cost, are why it’s so commonly used in the construction industry. While there are some drawbacks, such as its susceptibility to corrosion, the many advantages often outweigh those few drawbacks. 

Below are the main benefits and drawbacks of structural steel. 

Pros of Structural Steel

The benefits of structural steel include:

• Strength – Although structural steel is known to have considerable strength, it can be further improved by adding various alloys to its composition. The manufacturing process, mechanical working, and heat treatment of steel will also affect its strength. But the most important factor affecting this is its strength-to-weight ratio, which means it is significantly strong for much less weight.

• Cost-effectivity – The past decades have seen advancements in steel production, making it progressively cheaper and faster to produce. The time it takes to produce a tonne of steel nowadays is significantly lower, leading to lower costs.

• Aesthetic Versatility – Owing to the versatility of steel, designers and architects have more freedom of artistic expression through the shapes of structural steel components without compromising strength or functional properties.

• Sustainability – Steel is widely recycled in the construction industry. It is 100% recyclable with minimal degradation to the properties that make it a preferred construction component. Over 90% of structural steel is recycled, making steel the world’s most sustainable building material. Very minimal processing is required for its recycling, and the carbon footprint has continually been reduced, especially in the last decade.

• Fire Resistance – Steel is, by default, a non-combustible material but loses a significant amount of its structural integrity when heated sufficiently. ‘Critical Temperature’ is the term used to indicate steel’s ability to support a load under a specific temperature. 

• Resistance to the Elements – Steel is also particularly resistant to the elements, such as mould or mildew, which could affect the integrity of other materials. Although corrosion remains a weakness of steel, there are preventive measures that can be taken, such as sprays and protective paints, albeit at a cost.

Cons of Structural Steel

The downsides of structural steel include:

• Susceptibility to Corrosion- Steel is not a material chosen for its corrosion resistance since it contains iron, which is very susceptible to corrosion, more commonly known as rust. When formed, rust will consume steel and flake off to expose underlying material until the steel is fully consumed. Although preventive measures may be taken against corrosion, these do add to the cost. 

• Decrease in Strength in High Temperatures – Despite steel’s resistance to fire, temperatures that are high enough will slowly reduce its integrity. As such, steel of appropriate material composition should be used for construction. 

• Buckling – When under compression, steel is subjected to what is referred to as buckling. It is what happens when force presses into a slender structure and causes it to collapse. This means consideration during the design phase is essential to gauge the force structural steel will be subjected to. 

• Fatigue – This refers to the repeated cycles of strain/stress onto structural steel. This eventually breaks the steel and leads to the fracturing of the material. Metal fatigue in structural steel should also be considered during design and engineering. 

What Are the Most Common Types of Structural Steel?

The most common types of structural steel are beams, tee sections, flanges, plates and channels, among others. Learn more about these components below. 

Universal Beams 

Universal beams, also known as I-Beams, H-Beams, or Rolled Steel Joist (RSI), are generally used to serve as building blocks within steel frameworks, ensuring the structural integrity of the project due to their ability to support heavy loads. 

Universal beams come in different sizes and may be cut for specific construction requirements. Although they are often confused with universal columns, they have distinct differences and uses. Columns have almost equal width and depth, while beams have much more depth than width.

In turn, the dimensions of universal beams make them efficient at carrying shear and bending loads in the plane of the web due to the beams’ flanges, which resist parallel loads much more reliably than other structural alternatives.

Tee Sections

Tee sections, also called ‘T-sections,’ are load-bearing structural steel components. In some industries, they are also called ‘T-beams’ or ‘T-bars.’ They are made through specific manufacturing processes: hot rolling, hot extrusion, and plate welding. 

This type of steel section offers much more resistance than a flat steel bar if it is at least 4 metres long. Using tee sections also reduces the need for rebars and saves as much as 9% to 20% of required reinforcement compared to flat steel bars. 

They are also used aesthetically in modern architecture with many applications, such as bumper bars, edge protection, or even wooden furniture, as a visual accent.

Tapered Flange Beams 

These are similar in shape to universal beams, with the primary difference being the tapered flanges. The beam’s vertical section is referred to as a ‘web’, and the outer horizontal portions are ‘flanges’. 

Tapered flange beams are manufactured in a variety of sizes. They are used in a range of commercial and residential constructions, engineering, civil and bridge constructions, mining infrastructure, and rail car & machine building.

Parallel Flange Channels  

Parallel Flange Channels are also referred to as PFC or C-sections (due to their shape). They are suitable for many structural applications and engineering and boast many properties, such as increased strength and durability. 

They are generally used as support for floor joists since they are suitable for load-bearing applications.

Angled Beams 

Angled beams are steel beams shaped as an ‘L’ and come in several measurements. For this type of structural steel section, two steel legs are joined at a 90-degree angle. The legs can either be equal or unequal in length.

Because of their reduced structural depth, these angled beams are often used for floor systems due to their enhanced strength-to-weight ratio. They are often used for residential structures, transportation applications, and infrastructure.

Plates 

Plates are considered by many to be one of the most versatile structural steels. These can be cut and processed into a number of shapes and sizes based on the specific application. 

This further processing is a requirement since plates cannot stand independently and are usually attached to another section of structural steel. They are also sometimes attached to other steel parts to serve as reinforcing components.

The most common type of steel plates are referred to as base plates and are used in circumstances where the foundation is uneven, shallow, and difficult to work with. Base plates are usually applied to columns to allow for a better load distribution towards the soil beneath. 

Doing so ensures that the underlying foundation’s bearing capacity is not surpassed. Base plates are also classified into different types, the two most common ones being slab bases and gusseted bases.

Channels 

These are visually similar to steel beams due to the presence of webs flanked with flanges. However, the key difference is that the webs are oriented onto the side. In contrast, the flanges are oriented perpendicular to the web. 

This kind of design allows them to be well-suited for bridges, similar structures, and some marine applications.

Channels come in different lengths and may be manufactured up to 60 feet in length. However, the standard sizing falls between 20 to 40 feet. These structural steel sections cannot be used in the same way as beams since they do not have a flat side all around; their only flat surface is used to have them bolted onto other flat surfaces.

Bearing Piles 

Bearing piles are utilised when construction workers or engineers cannot find or create a solid foundation at the work site. These structural steel sections create deeper foundation systems that are much more stable and structurally sound.

These H-shaped steel components are designed to ensure an effective transfer of load through the pile to its tip. Known to be durable and efficient, they are able to bear more than 1,000 tonnes of weight and work best in densely packed soil (since this type of soil offers more resistance to the tip). 

The most common types of bearing piles are H-Piles, Pipe-Piles, Disc Piles, and Screw Piles.

Angled Sections

For some, steel angles are the bread and butter of steel fabrication as they are the most basic type of roll-formed steel. They are designed using a flat steel section and bending it (usually at a 90-degree angle), with both legs resulting in the same size. 

These are often found in framing, brackets, or reinforcements across different industries. They may be cut to size, which gives them enormous versatility.

Steel-angled sections come in two primary types – Equal Angle and Unequal Angle. The former has two axes which measure up to the same lengths. The latter is also right-angled but contains different-sized axes. You will usually see angled sections in residential structures, mining, infrastructure, and transport/logistics construction.

Square & Rectangular Hollow Structural Sections

Hollow Structural Sections (HSS) are steel profiles/ sections with a hollow portion that can be fabricated into several shapes – square, rectangular, elliptical, and circular. The profiles of these steel components are a little rounded, and their radiuses are almost twice the value of their thickness. 

They are commonly used with welded steel frames for constructing structures that carry loads in different directions.

Different forms of HSS offer distinct advantages and intended applications. But they are generally best for multi-axis load-bearing applications, and the creation of columns and posts, among others.

What Are the Applications of Structural Steel?

The most common applications of structural steel are in the construction industry, but it also plays a role in transport. 

Let’s explore the applications of structural steel in more detail:

• Construction: It is used to make the channels, plates and support beams found in residential, commercial, and industrial buildings such as homes, hospitals, stadiums, and bridges. Structural steel is also used to construct industrial spaces such as warehouses, bridges, factories, and buildings. These require structural steel to form steel frames, columns, bars, plates, and girders, among others. 

• Mining: In the mining industry, structural steel components are used for a variety of mine site infrastructure needs. This includes the mines’ structural elements, such as mining screens, the fluidised bed builders, and even the buildings, such as workshops and offices. 

• Energy: The energy industry uses structural steel in producing wind, electric, and nuclear power, and natural gas. Transmission towers, wind turbines, pipelines, oil and gas wells all use structural steel components.  

What Type of Steel Is Structural Steel Made Of? 

Generally, structural steel is a carbon steel, meaning its chemical composition contains iron and carbon. Structural steel is any steel with a carbon content that reaches up to 2.1% of its weight. The carbon content of steel is directly proportional to its yield strength.

However there are different types of steel that can be used for structural steel fabrication. 

Carbon Steel

All structural steels are considered carbon steel if no other alloying elements are present, the copper content of the steel does not exceed 0.4% to 0.6%, its manganese content is equal to or under 1.6%, and its silicone content does not exceed 0.6%.

High Strength Low Alloy Steel

This type of steel is meant to optimise its mechanical properties and corrosion resistance. These kinds of steel have manganese content which reaches up to 2%. Depending on the intended application, this type of steel may have trace amounts of other elements such as chromium, molybdenum, nickel, nitrogen, niobium, vanadium, and titanium to alter its properties.

Forged Steel

Forging refers to the process of shaping metal (in this case, steel) while it is in a solid state. The process produces a uniform grain structure to the steel, consequently improving its integrity due to removing voids and gas bubbles. Forged steel is any steel that undergoes this process.

Quenched and Tempered Alloy Steel

Quenching and tempering are processes which improve structural steel through the use of heat while also simultaneously cooling it in water, forced air, nitrogen, or oil. The result is a stronger, higher-strength structural steel that is much less brittle.

What Are Structural Steel Grades?

Structural steel grades are used to indicate the characteristics of the steel and distinguish it from others based on its properties. There are currently thousands of steel grades, each with specific chemical, physical, and environmental properties.

Structural steels that are widely used are categorised into steel grades by different national and international standards organisations. The standards serve as a foundation from which engineers can use as a guide when using structural steel. 

An example of steel grade would be Grade 250, which refers to a medium-strength structural steel plate usually meant for high-rise structures, bridges, and general fabrication. Although properties are standardised, Grade 250 structural steel can come in a range of thicknesses, from 3mm to 300mm.

Some more examples would be Grade 350, which is generally stronger, Grade 1045, which is designed with the intent of being used for high heat applications with a lot of moving parts (e.g., gears), and Grade 500, which is typically used in mining equipment for its toughness and lead bearing.

How Is Structural Steel Fabricated?

Fabricating structural steel involves several processes to form a steel section, starting at the ideation and planning phase and quickly moving onto fabrication, which involves cutting and shaping the steel. From there, the steel is engraved, finished and coated as necessary, and is ready to be delivered. 

The structural steel fabrication process undergoes five stages, namely (1) ideation, blueprint and shop drawings, (2) cutting, bending, and drilling, (3) engraving and assembly (including steel welding), (4) shipping preparation and component finishing, and (5) site delivery and erection. The actual fabrication does not begin until the second stage, where a majority of the physical processes are involved.

Due to structural steel’s properties, it is easy to fabricate into many sizes and shapes. Its cost-effective nature compared to other metals, such as copper, makes it the preferred metal for fabrication. Structural steel remains one of the most suitable materials for fabrication with an equally reliable ROI.

Structural Steel FAQs

What Is the Most Common Structural Steel?

Carbon steel is the most commonly used structural steel in the market today, largely due to its many beneficial properties, such as its affordability and strength. Carbon steel is more common than high strength low alloy steel, which is also frequently used due to its versatility.

Is Rebar Structural Steel?

Rebar (or reinforcing bar), also referred to as reinforcing steel, differs from structural steel. Rebar is used to reinforce or support concrete and masonry, while structural steel serves as the frame of a structure, for example. 

How Strong Is Structural Steel?

Structural steel is considered to be similar in strength to reinforced concrete. Its tensile strength sits in the range of 400 to 500 MegaPascals (MPa). This value determines how much pressure it takes before structural steel reaches a point of material failure.

What Is the Difference Between Reinforcement Steel and Structural Steel?

Reinforcement steel, or rebar, is used with concrete and masonry solely for support. Alternatively, structural steel is used by itself and serves as the frame of structures. Unlike reinforcement steel, structural steel must conform to higher standards and regulations, and comes in more sizes.

What Is the Strongest Beam Shape?

The I-beam is considered the strongest beam shape for structural steel. These are intended to resist bending and are capable of bearing heavy loads. Vertical strips of metal across the flanges place the greatest depth of material on the plane of stress, preventing twisting.

How Does Carbon Content Effect Steel?

Carbon content is directly proportional to the strength of steel. The more carbon is added, the stronger the steel is. But this also makes the steel more brittle, which reduces its weldability. The right mixture of steel and carbon is much better than just increasing carbon content to harden the steel.

Is Steel Stronger Than Concrete?

Yes, generally speaking, steel is much stronger than concrete. Although reinforced concrete (with rebar/reinforcement steel) is on par with structural steel, concrete alone is not. Concrete has a tensile strength of just 70MPa, while structural steel sits at 400 to 500MPa.

Disclaimer:

This article is published in good faith and for general informational purposes only. Kanyana Engineering does not make any warranties about the ongoing completeness and reliability of this information. Always seek specific advice on your metal fabrication project to ensure all variables are considered. 

Graham Dawe is the Managing Director and Works Manager of Kanyana Engineering. With decades of experience in the metal fabrication industry, he is dedicated to keeping Kanyana at the forefront of the sector’s technological growth. Looking beyond the process itself to holistic, integrated CAD, CAM and MRP solutions, Graham believes Australian manufacturing has an enduring place on the global stage. In Kanyana Engineering’s state-of-the-art workshop in Mandurah, WA, Graham delivers an exceptional standard of work for commercial, industrial and government clients alike.

Concrete or Steel?

Steel and concrete are not the only materials used in construction of course, but they are among the most plentiful and widely used materials in most modern building construction. Steel of various grades and attributes, concrete of various grades and attributes, and other materials, such as clay, mortar, ceramics, wood, masonry are all commonly used.

For load-bearing purposes, such as structural framing and weight-bearing crossbeams, the materials usually used include some combination of structural steel, concrete, masonry, and/or wood. Depending on the conditions and desired performance of the structural component, different combinations, grades and designs will be employed. By far the most common and plentiful component materials in these situations are reinforced concrete and steel. The best grade, material combination, and design for the purpose is determined by an engineer. Factors that influence these decisions include weight, strength, constructability, sustainability, availability, longevity, fire resistance, appearance and cost.

Let’s take a more detailed look at a few of these factors:

Costs

This will depend on several factors, such as the location of the build, the size of the order made, transport costs, availability and cost of supporting machinery, components and skilled and unskilled labour. Reinforced concrete, for example, requires form work prior to pouring, which accounts for roughly half of the finished cost. Prep work demands are high, but once this work is properly completed, the concrete can be poured in and allowed to cure. It them forms a solid, strong material that has conformed to the desired shape it took when in its pre-cured, liquid form. Precast concrete has become a popular way to reduce costs (through factory manufacturing methods) and maintain greater regularity of shape and form. Manufacture is swift and so, assuming transport is available and efficient, using preform methods can speed up other aspects of a build as well, saving costs over a wider range of factors than just the concrete itself. Since the steel (which is used to reinforce the concrete from with) is sold by weight, structural designers determine the lightest and least amount of steel that will still produce the required strength and other properties needed for the components. Bulk buying identical components (even though some may be over-engineered for their purpose) can greatly reduce costs as compared to buying each component with properties specific to the job at hand.

Strength-Weight Ratio

Strength-to-Weight Ratios, or specific strengths, are common ways to categorize construction materials. The strength is divided by the density, and the resulting rating is used to indicate how useful the material would be in a given situation of for a given purpose. For example, concrete is ten times greater for compression strength than for tension strength, so its strength-weight ratio is much higher for situations in which compression strength is the main attribute needed.

Sustainability

As environmental concerns grow in importance and urgency, many construction companies and materials vendors are listing sustainability attributes as major features of their products. Using sustainable and sustainably-manufactured materials usually does not significantly affect the performance or cost of structures, and some of them are actually less expensive. Currently, for example, more than 80% of structural steel members are made from recycled materials (A992 steel). It is cheaper and has a higher strength to weight ration than A36 grade steel members. Concrete primarily uses naturally-occurring materials as components, and is now being made to be permeable, which decreases the need for drainage and overflow infrastructure, as the water can pass through the surfaces themselves. Disposing of old concrete is also less environmentally harmful, as it can be used as aggregate in other construction projects, rather than simply thrown into a landfill.

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Fire Resistance

Fire can be one of the most frightening and dangerous risks to a structure and those living and working within it. In climates where the weather is dry and windy, a fire can mean a roaring inferno in minutes, and wooden structures are especially susceptible to this danger. Even structural steel can be in danger of failure in such conditions. Using reinforced concrete, both as a primary part of the structure and as a firebreak or shield for other materials, is a great way to mitigate these risks.

Corrosion

Corrosion from exposure to water, heat, humidity, salt and other substances can pose a long-term problem to some building materials, causing damage to the appearance of the materials, but also to structural integrity. When installing some materials, special steps must be taken to ensure such materials are protected from potentially harmful elements, and maintenance of such materials needs to be done regularly and in compliance with recommended care procedures. Structural steel may rust if exposed to water, wood may rot, and mould may infiltrate cracks and cavities in the structure, causing danger to those living and working in the vicinity of the structure. These are all well-known risks, however, and both materials manufacturers and construction companies take steps to mitigate risks and educate users as to best practices to stay safe and extend the usable life of these products and structures.