A British glass company that specialises in designing systems designed to withstand terrorist attack has welcomed new advice from the Royal Institute of British Architects (RIBA).
Architects have been issued with guidance from RIBA for the first time about incorporating anti-terrorism measures into their designs. “This advice is very welcome because it will make architects think about the safety of a building’s residents from the outset and, as we now know, terrorism is threat to all of us,” said Denis Wright, managing director of Wrightstyle Limited.
Wrightstyle has been at the forefront in developing glass and glazing systems to mitigate against a whole range of threats, from fire to ballistic and explosive attack, and has recently introduced a system that can withstand even the explosive impact of a lorry bomb.
The Royal Institute of British Architects (RIBA) has issued its advice to improve the way architects and planners think about security. The advice includes a range of measures, including barriers and bollards, landscaping and surveillance, as well as using blast and ballistic resistant glass.
“The message that we have been trying to convey to architects is that, if a system such as ours is used for the external glazing, the glazing system will look no different from conventional curtain walling,” said Denis Wright.
The RIBA advice comes in the wake of further recent terrorist atrocities in Moscow and amid continuing uncertainty worldwide. The importance of blast resistant curtain walling is that the main cause of injury and death from a bomb attack is flying glass. In an attack using explosives in an urban area, between 80-85% of all secondary blast injuries are caused by flying glass.
Wrightstyle’s landmark test, conducted independently at a specialist site in the UK, involved the system being subjected to the equivalent of 500k of TNT, acknowledged as an average-sized lorry bomb.
Although glass and glazing companies have been active for some years in developing safer systems, the attack on the Federal Building in Oklahoma City some fifteen years ago focused research attention. Amid that carnage, 200 victims suffered from glass injuries and glass fragments were found six miles from the detonation. In New York, on 9/11, 15,500 windows were damaged within a mile of Ground Zero, nearly 9,000 within half that distance. One senior fire officer had to have 47 shards of glass removed from his eyes.
When a bomb detonates, it produces gases at very high temperatures. This in turn 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.
The Wrightstyle system’s strength was achieved through a glazing technique that bonds the glass to the framing support system, so that in an explosion, the components work together to safely absorb the shock of the explosion and retain the glazing elements.
In the independent test at RAF Spadeadam in Northumberland, the simulated lorry bomb attack was immediately followed by a simulated car bomb attack (100k of TNT). The lorry bomb was detonated 75m from the test rig, whilst the car bomb was detonated at a distance of 20m to produce a higher pressure loading and shock on the façade.
“We may not have yet taken explosives from the hands of terrorists. But for the occupants of those buildings that incorporate the latest blast-resistant steel glazing systems, we have taken away an equally potent weapon: the glass itself,” said Denis Wright. “We absolutely welcome RIBA’s advice because, from now on, architects must consider the whole range of measures that can be taken to mitigate against terrorist attack, yet still design buildings able to incorporate beautiful glass façades,” he said.