An Introduction to Steel Bending

SmartShelters was founded over a century ago and some of our first steel structures supported the New Zealand military during World War 1. From world-class event structures to industrial shelters, wide-span covered areas to agricultural fabric buildings, SmartShelters are one of a few companies in New Zealand that are specialists in commercial steel bending.

Modern architecture with fabricated structures relies heavily on curved metal beams, pipes, tubes, and angles to construct everything from a simple park bench to spiral staircases, to the backbones of skyscrapers. Visit any airport or museum built in the past few decades and keep an eye out for the numerous curved metal structures that go into their designs.

Whatever structure you’re interested in building, there may be advantages to utilising steel framing to ensure its durability and longevity. Let’s take a look at what exactly steel bending is and how you might be able to incorporate it into your building.

What Is Steel Bending?

Bending or rolling steel is the process of curving a length of steel, also known as a steel member, to a specified radius and arc length. Bending is commonly used to describe the process for a tighter radius bend, whereas rolling is used to describe a larger radius bend.

History of Steel Bending

Before steel bending came into general use, blacksmiths worked with iron. Due to wrought iron being a relatively soft metal, it could be easily manipulated with heat to form sound structures.

On the contrary, using curved steel members in larger structures came into fruition during the nineteenth century due to the improved strength of the material. In its early applications, curved steel joists were rolled into colliery arches by metal benders to support underground workings, or mining tunnels. As early as 1910, steel bending was also used in the fabrication of ship hulls, aircraft hangers, military buildings and other relatively simple structures.

Smart Shelters, formally known as Cairns & Woodward, was founded in 1915 and is the longest-established fabric clad shelter company in New Zealand. Some of our first shelters were provided for the New Zealand defence industry during World War 1 and with over 100 years experience in this field we now provide the best quality and competitive standard military shelters today.

Initially, hydraulic presses were used to curve the joists until the more advanced three-roll bending machines came into play, streamlining and simplifying the process. For this reason, steel bending rose in popularity in the late 1970s with the help of technological advances and better machinery. This development has had a significant influence on the design of curved steel structures and metal bending became a common feature in the construction industry.

Demand for curved steel members increased considerably in building structures during the last half-century. With capital investment shifting from industrial to commercial buildings, the construction of new offices, train stations, airport hangers and terminals, leisure facilities, and shopping centres has encouraged the structural steel business to flourish. Metal bending became a viable business in its own right, offering curved metals in a limitless variety of shapes and sizes.

How do you Bend Steel?

There are three main bending processes and each method produces different results depending on the member, material, and required radius.

Roller bending

Roller bending is a cold process using a mechanical jig with three rollers. The member passes through the rollers with the use of force to bend the metal into a circular arc. The rollers freely rotate about three parallel axes. Two outer rollers cradle the bottom of the metal while the inner roller, whose position is adjustable to determine the radius, presses down on top of the metal. This process is repeated until the desired curve is created.

SmartShelters utilises and bends galvanised steel framework for our shelters and with the use of the best quality materials, SmartShelters are designed to be strong, reliable, fit for purpose and easy to maintain. We have developed and strengthened our reputation for providing class-leading and innovative fabric weather protection solutions.

Roller bending is the steel bending process used in SmartShelters and we have one of only a handful of large section rollers in NZ. This form of bending has many benefits:

Roll forming provides tight tolerances and eye catching finishes due to the radial forming sequence.
Roll bending has no limit on part length unlike other methods of bending.
Almost any type of metal can be roll formed using this method.
This process can produce higher volumes at lower costs.
The rolling dies are gentle on soft sheet metal, making roll forming ideal for metals already finished with paint, plating, or coating such as the galvanised steel we use at SmartShelters.

Induction bending

With induction bending, a member is passed through an electric coil. Electric currents heat up the cross-section around 50mm wide to between 700°C and 1100°C. The leading end of the section is clamped to the pivoted radius arm and once the metal reaches the desired temperature, the straight metal section is passed through the coil to the length of the radius arm, creating the desired arc. This section is then immediately cooled using air or water to set it. The combination of speed, heat, and cooling allows for bending larger profiles.

Combined induction/roller bending

A mix of these first two methods can produce different bending requirements. The length of the radius arm limits the bending radius possibilities. By incorporating or replacing the radius arm with a set of bending rolls, this method can be used to produce larger radii or multi-radius curves. The bending still occurs from the applied heat from the induction coil, but the force is provided by the rolls rather than the radius arm.

The Advantages of Bending Steel

Curving steel framing brings elegance and function together in the construction of large commercial buildings. It is instantaneously more aesthetically appealing and with the combination of strength, durability, beauty, precision and malleability, architects can stretch their imagination and create striking and eye-catching structures with exposed steelwork, while forming the skeleton of the structure.

Steel’s ability to span long distances without the need for support enhances the functionality of large open spaces, free of intermediate columns or load-bearing walls. Take sports stadiums, for example, that incorporate large spans of curved steel to avoid the use of columns and enhance the viewing experience. It also has the ability to enhance structural efficiency with arches and variable depth trusses, as such is utilised in the framework of our shelters.

What are the Bending Materials?

Steel is great for large scale construction foundations and carbon steel is the most widely used material for structural purposes due to its flexibility as a strong and reliable component for construction and OEM purposes.

Galvanised steel is the best steel to use for roller bending. SmartShelters specialises in roller bending and uses superior galvanised steel (that meets or exceeds C350 grade). Galvanised steel works well with cold work used for commercial structures and roller bending is the best method for this desired finish.

Besides steel, other sheet metals that are commonly used in the bending process are aluminium and copper, more commonly used for pipes and tubing. These materials are not commonly used for structures. Other malleable metals that can be bent without breaking include silver, gold, iron, and lead.

What Are Common Uses for Steel Bending?

Some of the most common uses for steel bending at SmartShelters is for arch beams on shelter roofs. There are many other uses for steel bending across the construction, industrial and commercial sectors such as large arches, architectural work, guide rails, lifting hooks and u bolts, piping, tracks and more.