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Glazing
Over the
Window
Pain
By Les O’May,
wrightstyle Sales Manager,
Far East & SE Asia
We live in uncertain times, whether
in Europe, the Americas or the Far
East. The threat of terror, real or
imagined, involves both global and
local dimensions. In our industry
it also involves the design of new
buildings and how those buildings
are built to withstand new threats.
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The searing image of 9/11 remains the toy-like aeroplane flying into the World Trade Center; an image plucked from a Hollywood blockbuster and thrust under the world’s unbelieving eyes. But it wasn’t the first terrorist attack and, sadly, won’t be the last – although it’s likely that future activity will involve more conventional means to create carnage.
It is, of course, the first objective of governments world-wide to remove explosives from the terrorist arsenal. However, it would be wrong to assume that high explosive alone is the main cause of death and injury. In urban areas, between 80-85% of all secondary blast injuries are caused by flying glass.
It was the terrible attack on the Federal Building in Oklahoma City nearly eight years ago that really focused minds both in governments and in the glass industry. Amid that carnage, 200 victims suffered from glass injuries. The images from that atrocity were compelling reminders that glass can be both a friend and an enemy.
The lessons learned from Oklahoma and elsewhere have now directly led to new and better glazing systems, allowing architects to design aesthetically-pleasing structures – but knowing that large glass frontages can safely still be incorporated.
One of the foremost experts on blast injury is Eric Lavonas MD of the Department of Emergency Medicine, Carolinas Medical Centre. He writes: “Secondary blast injury is responsible for the majority of casualties in many explosions. For example, the glass façade of the Alfred P Murrah Federal Building in Oklahoma City shattered into thousands of heavy glass chunks that were propelled through occupied areas of the building with devastating results.”
The day after the Oklahoma bombing, the US President instructed the Department of Justice to see what conclusions could be drawn in terms of protecting federal buildings. One of the DOJ’s key findings was “to provide for [the] application of shatter-resistant material to protect personnel and citizens from the hazards of flying glass.”
This echoes findings of the Applied Research Association Inc. “Historically, the major contributor to injuries due to terrorist explosion in urban environments is the glass fragment hazard generated by breakage of windows.”
At Oklahoma, glass fragments were found six miles from the detonation. In New York, 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.
However, in the wake of Oklahoma, researchers from the Glass Research and Testing Laboratory at Texas Tech University reached a significant conclusion. They found that damage to property and person could have been reduced if laminated glass had been used in the buildings that surrounded the Federal building.
It’s a lesson being learned across the globe as architects struggle to balance form and function with the new requirement of additional security. For example, after Oklahoma, the US State Department started to make windows smaller and less numerous in several embassy projects. Knee-jerk reaction, perhaps – but entirely understandable.
However, and quite simply, none of us want to live and work in windowless environments – and architects don’t want to design buildings where form and function are severely imbalanced. So it was in the US, and the State Department experiment was dropped on aesthetic grounds.
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Partly this was in response to a report written for the US National Academy of Engineering. It said that “a more proactive approach is to develop glazing materials that meet aesthetic and functional design objectives but do not contribute to the explosion-induced projectile hazard.”
A laudable objective and several manufacturers have rushed to offer blast-resistant glazing systems. Some are good. Others, frankly, are either bad or ugly. The key requirement – for designers or anyone involved in specifying blast-resistant glazing systems – is to ascertain what level of testing the product or system has undergone.
This is a central observation in a report from the Applied Research Association. It states: “As a general rule, products that have been specifically engineered to perform well in blast environments perform much better than those products that have undergone limited or no research and development in this area.”
For such applications, suitable glass is not just the only consideration. It has to be properly supported and retained by a high-performing frame. Fit the wrong framing system and in the fraction of a second following an adjacent or nearby blast, the explosive pressure may blow out – intact – the entire window system.
Here at wrightstyle Ltd we’ve just completed project-related high pressure blast-resistant testing. The system tested was our SR curtain walling and roof glazing systems. It’s a sign of the times that the test was carried out amid tight security and, for reasons of confidentiality, we are not allowed to say what level of blast our system was subjected to.
However, what we can say is that independent test analysis conclusively demonstrated that the SR system, using either steel or stainless steel rolled hollow profiles, does provide life-saving protection. It also has the added benefit of aesthetics – secure and safe glass façades can also look good, from the inside or outside.
What the SR system does is withstand the blast pressure and keep the glass within the system profiles. This eliminates primary and secondary blast injury – as well as the tertiary injuries associated with people being lifted off their feet and thrown against hard objects such as walls or office furniture.
The glass and glazing industries have responded to painful lessons. None of us in the industry really wanted to develop such safety characteristics to cope with a mad and bad world. We’d much rather that the baddies were caught or went away. However, the harsh reality is that we had to respond and we have now pushed the design envelope of what can be achieved safely.
We may not have yet taken explosives from the hands of terrorists. But for the occupants of those new buildings that incorporate the latest blast-resistant glass systems, we have taken away a much more potent weapon: the glass itself.
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Glazing Over the Window Pain
