Designing buildings with bomb resistant glazing is sadly becoming more relevant in our cities.
In recent years, the threat of terror has focused the minds of architects, engineers, and planners to design buildings to withstand a whole new array of risks.
Proposals this week following a spate of terrorist incidents, recommend that businesses and councils put in place better measures to protect the public from terrorist attacks.
Designing-in safety is nothing new, but as yet there is no universal methodology for assessing terrorist threats within buildings, or how to protect against them.
Partly, that’s because of the variable nature and size of the threat, but also because of the lack of understanding of the options available to make buildings safer.
The need to guard against fire are integral legal requirements in building regulations everywhere. But what is not included to date, are explicit guidelines on building safety against terrorist attack.
At Wrightstyle, we’ve been supplying glass and glazing systems internationally for many years now, mostly to contain fire and provide safe evacuation routes, but also to reduce the risk from explosions, bombs and ballistics.
One of the biggest threats in an attack, is not from a blast or explosion itself but from broken glass. In urban areas, between 80-85% of all secondary blast injuries are caused by flying debris.
That’s because when a bomb detonates, it produces gases at very high temperatures. This leads to a rapid expansion of air and the creation of a shock wave travelling at supersonic speeds.
The shock wave lasts only a few milliseconds and is then followed by an equally sudden, but longer lasting, drop in pressure. It’s the enormous impact of the shock wave and the subsequent suction that shatters the glass and distorts the framing.
Until quite recently, the physical properties of glass made it impossible to guard against a severe detonation. However, innovation in steel technologies and glazing materials have enabled us to overcome glass’s inherent fragility.
We can now provide architects with glazing systems that allow for aesthetically-pleasing structures with large spans of glass – but which will remain intact in the event of an explosion.
Which is good news, as none of us want to live and work in windowless environments – and architects don’t want to design buildings where form and function are unbalanced.
It is important though, that anybody specifying a glazing system to mitigate against explosion must ensure that both the glass and framing system have been tested together.
That’s why our strong advice is to always specify the glass and framing as one unit. In a real fire or terrorist situation, the glass will only be as protective as its frame, and vice versa.
Our own steel system has been successfully tested independently. In recent tests, a charge of 500 kg of TNT-equivalent explosive was detonated adjacent to the glazing system. That’s the size of a lorry bomb. We immediately followed that with a simulated car bomb attack on the same assembly (100 kg of TNT).
You can watch a video of the blast testing on our website here.
We may not be able to stop an unexpected knife attack or an exploding nail bomb. But for the occupants or passers-by of buildings that incorporate our latest blast-resistant steel glazing systems, we have taken away an equally potent weapon: the glass itself.
Wrightstyle, based in the UK, supplies specialist glass and glazing systems worldwide, including their steel bomb resistant glazing.
Picture credit: mputsylo