The managing director of Wrightstyle, a glass solutions company that worked on Orbital at London's...
Wrightstyle Limited is a leading UK supplier of integrated steel and glass systems. Simon Bennett, the company’s international sales director, worries that the British prime minister’s statement on terrorism may lead to unnecessary or inappropriate knee-jerk architectural responses.
Prime Minister Gordon Brown recently outlined further measures to combat terrorism – from recruiting additional staff into the security service, to introducing additional security checks at main railway stations. The government also conceded that the physical layout or design of buildings might have to change, a statement that needs to be challenged, because too few architects and security experts fully understand the enormous advances that the building industry has made to make buildings safer.
The simple fact is that, when it comes to building safety, the main cause of injury and death is not high-explosive, but silicon and sand.
According to a recent submission to the US House of Representatives sub-committee on public buildings and economic development: “Glass is the single greatest source of both building damage and human injury in urban bomb attacks. In urban bomb attacks many people can be fatally injured at great distances from the detonation – people who would have survived uninjured but for falling or flying glass.”
The mechanism of injury from blast trauma has been studied since the Balkan Wars in 1914 and continued during and after World Wars I and II. Overall, blast injuries result in mortality ranging between 7.8% in open air to 49% in a confined space. A majority of victims (70%) will sustain soft tissue injury, and traumatic amputations will occur in approximately 11% of cases.
The issue of glass as a terrorist weapon was pushed to the top of the security agenda by the attack on the Alfred P Murrah Federal Building in Oklahoma City in 1995, the first time that a major terrorist attack occured on US soil, and which gave rise to an unprecedented level of buildings research. In that attack, 167 people died and 750 were injured.
Based on research carried out by the Walter Reed Army Medical Center following the Oklahoma bombing, another fact from the NCTC is that: “Blasts involving explosives inflict severe…injury, mostly as a result of secondary blast effects from glass and other debris.”
Most people killed or badly injured in a blast involving High- Explosives (HE) are affected by either primary or secondary blast injuries. Primary HE blast injuries are caused by high-pressure gases from the explosion rapidly expanding to produce a supersonic blast wave. This has devastating effects on human air-filled tissue, particularly the lungs and gastrointestinal tract. Primary blast injuries are generally fatal. Secondary blast injuries are much more common than primary blast injuries and are the most common causes of death in blast victims. The penetrating injuries occur most often in the exposed areas of the body such as the head, neck and extremities.
The Journal of Performance of Constructed Facilities puts it more graphically: “When a terrorist bomb explodes in an urban area, it produces devastating effects, including structural and non-structural damage to buildings, injuries and death. Numerous injuries in explosions result directly and indirectly from window glass failure. Direct glass-related injuries occur when glass shards flying and falling from fractured windows cause lacerations and abrasions. Secondary glass-related injuries occur when the shock front of the blast wave passes into buildings through fenestrations vacated by fractured glazing.”
Research from Oklahoma and elsewhere concluded more than one-quarter of glass-related injury victims in buildings occur within 1.5 metres of a wall with glazed windows and nearly one-half of glass-related injury victims are positioned within 3.0 metres of a wall with glazed windows.
Oklahoma focused the attention of the engineering and security communities on two major issues: the prevention of progressive structural collapse (once again a prime focus following the September 11th terrorist attacks) and the design of blast-resistant glazing. This led the Commission on Engineering and Technical Systems to set up a Blast Mitigation Program to develop methods to protect people inside buildings from terrorist bomb attacks.
The Commission noted that: “The focus is on protecting people, not the building or other assets. Two key issues in the program are the primary cause of injuries and death in terrorist bombings; structural collapse, and flying debris, for example, glass.”
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 application of shatter-resistant material to protect personnel and citizens from the hazards of flying glass. This indictment on glass was echoed by the conclusions of the Applied Research Association: “Historically, the major contributor to injuries due to terrorist explosion in urban environments is the glass fragment hazard generated by breakage of windows.”
The scale of glass injury can’t be overstated. At Oklahoma, for example, glass fragments were found six miles from the detonation. In New York on September 11th, 15,500 windows were damaged within a mile of Ground Zero – nearly 9,000 within half that distance.
In the wake of the Oklahoma bombings, 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. An obvious conclusion, perhaps, but one that began to concentrate minds and encourage focus on the importance of enhanced glass and framing systems.
Until Oklahoma, certainly in the USA, there had been little market demand for bomb-proof glass or glazing systems. In the UK, despite the Provisional IRA, there was a similar complacency. The PIRA’s modus operandi had always been to balance the propaganda value of an attack against the likely number of fatalities and, with few exceptions, only to carry out operations resulting in limited injuries or loss of life.
On both sides of the Atlantic therefore, until Oklahoma, there was no clear security or architectural consensus that glass and glazing systems needed to be improved. The accepted design solution was either to design smaller windows – a move pioneered in the USA by the US State Department – or coat them with a plastic polymer and hope for the best.
However, a report written for the US National Academy of Engineering helped to change official views. It stated: “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.” That report, among many others, made clear that terrorist activity might not be a transient phenomenon and had to be planned for at the design stage of a new building, particularly for sensitive commercial or military installations, and that it was up to the glass and glazing industries to come up with technical solutions. As the security, architectural and glass industries began to fully wake up to the enormity of Oklahoma, and of other attacks on western interests in the Middle East, the world suddenly changed.
Perhaps the world should have seen it coming.
In a submission to a US Senate Committee on Intelligence, Louis J Freeh, director of the FBI, said that: “Loosely affiliated extremists, motivated by political or religious beliefs, may pose the most urgent threat to the United States. Within this category, Islamist extremists, such as Osama bin Laden and individuals affiliated with the al-Qaeda organization, have demonstrated a willingness and capability to carry out attacks resulting in large-scale casualties.”
His words, prescient and concise, were spoken in May 2001, four months before Osama bin Laden proved him right. After those attacks, a clear consensus immediately emerged among urban planners, architects and, not least, the glass and 0.glazing industry. Ways to mitigate against blast hazards posed by terrorism had to be found, and quickly.
The initial knee-jerk response, to design high-risk buildings with smaller windows, was quietly swept under the carpet. Nobody wants to work in a bunker, architects didn’t want their designs to be compromised, and planners and politicians didn’t want to feel that terrorism – in design terms – was dictating what cityscapes should look like. The architectural and aesthetic imperative was to find new ways that would allow buildings to continue to make full use of structural glazing and curtain walling.
THE WRIGHTSTYLE SOLUTION
At Wrightstyle, we took a more holistic approach, a design journey that brought us recently to a test site in Northumberland, where we simulated what would happen to our glazing system if a lorry packed with 500 kg of TNT-equivalent explosive was detonated nearby.
Our integrated system not only passed the test, remaining intact within its frame, but then passed a second test when we moved the seat of the explosion closer to the glass and simulated a car bomb attack. It might have been a smaller explosion but, being closer to the test rig, it generated a more intense shock wave.
In terms of safety and aesthetics, it is a significant step forwards. It means that the inhabitants of buildings can be protected against terrorist attack, while not giving the ‘bad guys’ the satisfaction of having buildings being designed to look like reinforced bunkers. Architects can still use their full imaginations to design stunning buildings.
It may be a small victory in the War on Terror but it does mean that we are taking glass from the terrorist’s arsenal. The explosives may still be out there, but let’s not redesign our cities around redundant concepts of building safety.
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