The Steel Advantage

Lee Coates, Technical Manager, Wrightstyle

It sometimes seems that aluminium glazing systems have been around since dinosaurs ruled the earth. No doubt, these systems will be around for another eternity – and performing perfectly adequately.

Building technology continually undergoes a natural progression, through the improvement and development of new materials and manufacturing technologies. In the not too distant past the regular use of wood in glazing systems, it is remembered, progressed to drawn steel, then to aluminium and now the increased use of cold rolled steel sections in all world markets.

However, as architects have changed the face of building design with larger and still larger spans of glass, regulatory and other legislative frameworks have demanded higher and still higher safety requirements. Those two trends now mean that for some high-specification applications, aluminium can no longer deliver.

The most common form of building protection is the preservation of life and property from the effects of fire and smoke inhalation. In today’s uncertain world we can also add, at least for certain high-value projects, protection from blast, ballistic or physical attack.

Aluminium system technology cannot meet all of these requirements, a recognition that led directly to the development of steel-based glazing systems for specialist applications.

These systems should be seen as complementary to, rather than replacing aluminium products, although it takes far less energy to produce a ton of steel than it does a ton of aluminium. Aluminium systems are perfectly suitable for most architectural glazing applications.

Steel is ideally suited to meet specialist demands, providing for fire resistance, smoke resistance, blast resistance, bullet resistance, anti-bandit resistance, as well as sound and thermal performance. In addition, the inherent strength and greater stability that steel profiles can provide (the X-I value) means that steel glazing systems are suitable for spanning large distances, in either vertical or slope applications without the need of supportive steelwork.
The advantage of steel over aluminium is best exemplified in fire resistance, with the specialist glazing providing protected areas for the containment of a fire within a building, as well as providing safe escape routes for the evacuation of people. These requirements can also extend to the protection of adjoining buildings, the protection of equipment within a building, or the provision of safety zones for fire fighting forces. Simply, for maximum fire resistance, steel glazing systems offer a higher level of safety.

At the highest end of the threat scale is the requirement for specialist blast-resistant glazing systems. These type of systems are designed to be primarily used where the threat of terrorist action is considered to be a possibility. Typical examples would be embassies, law courts and government buildings.

The problem with making a glazing system blast proof is that of retaining the glazing in position, as any glass that becomes detached and is carried through the building on the shock wave from the explosion can – and does – cause horrific injury.

Because of the better structural properties of steel profiles over aluminium, these types of facade systems have a much better resistance to the force of primary or secondary explosion, whilst at the same time providing the required weather and thermal performance.

The threat of terrorism extends to anti-bandit and bullet proof glazing systems, that can prevent projectiles passing through the glazing or support system. Again, achieving this difficult specification is much easier using steel than aluminium.

In addition to countering various threats, there is an increasing requirement in modern architecture for large span glazing to roofs and facades. Once again, by using steel profiles for the glazing grid, far better structural properties can be achieved over aluminium.

It also means that large unsupported spans of glazing can be constructed without the need for secondary supportive steel – with considerable savings on constructional costs.

Pictures: SR Glazing in Roof Glazing. Fire Resistant Curtain Walling in Midsummer Place – large UK shopping mall. Cairo TV Centre – SR Glazing system used in slope glazing of the new.

As with all technical developments, research continues within the glass and glazing industry to meet evolving requirements – whether driven by changing architectural trends, new threats or new regulatory frameworks.

There is a place for both steel and aluminium glazing systems. The trick for designers is to understand their differing safety properties and to specify accordingly. In many applications, aluminium is fine. In others, the greater structural strength of steel gives it the edge. Designing for tomorrow means designing for a safer tomorrow.

Top – Glasdach-innen
Centre – Mubarak TV Centre, Cairo
Bottom – Summer Place Mall, Milton Keynes, UK