Why urban glass is a double-edged sword
Glass has cemented itself as the architects’ medium of choice. Renzo Piano’s majestic ‘Shard’ in London is Europe’s tallest building and the envelope continues to be well and truly pushed elsewhere around the globe in pursuit of construction utopia. Whilst designed to be aesthetically pleasing and more environmentally efficient, modern office blocks and other notable public buildings, shrouded in vast, architect-inspired expanses of glass, still remain vulnerable in the event of a terrorist attack. Buildings with significant areas of unprotected glass and there are hundreds just in London alone, pose a dangerous risk to life in the event of a bomb blast.
According to London based secure glazing and counter-terror buildings specialist, Advanced Glass Technology, at least half of all flat glass in the City is unprotected. Continuing high threat levels across Europe mean that investment in protecting personnel and infrastructure should be a major priority for property owners and facilities managers in urban areas. Having delivered a number of building protection projects in the capital as well as in the Middle East over the past 15 years, AGT is urging property owners to ensure adequate measures are in place, as part of their Corporate Social Responsibility, to mitigate the risk of injury and death in the event of a terrorist attack.
Due to the number of rapidly developing infrastructure projects in Northern Iraq, in particular within the Kurdish capital of Erbil, the region is now AGT’s biggest international market. As well as the private sector, including major oil companies and other corporations, the company is working on behalf of a number of embassies and Non-Governmental Organisations.
AGT are specialists in the retro-fitment of BSEN and GSA-approved anti-shatter security film, window frame anchoring systems and ballistic-proof doors and walling for any building. In the UK, the window film market has historically focused on providing aesthetic, anti-glare and environmental benefits but AGT believes that the requirement for physical protection is now critical. Advances in new construction materials have made the process of installation quicker, easier and more cost-effective, as Martin Westney, Managing Director, AGT, explains:
“A fundamental part of new building planning is the safety and protection of occupants, building assets and utilities, so our expertise in risk mitigation and injury prevention is increasingly being called upon. In light of heightened threat levels, UK companies employing large numbers of office workers, as well as organisations with assets in the public domain should have this on their radar and we would expect and hope that legislation to reflect this will be introduced.”
Tests have shown that the resulting shock wave from a bomb blast results in more than 1,800 glass fragments per square metre being accelerated across a huge radius, causing catastrophic destruction. With anti-shatter blast mitigation film in place, however, the glass breaks but all the pieces are contained, thereby protecting people in the vicinity, as demonstrated in this video.
Guidance from the Home Office’s Centre for Applied Science and Technology (CAST) requires security film to achieve a specified adhesion to the glass at regular intervals after installation. This is essential to maintain the film’s ability to hold glass fragments together after a ballistic attack or bomb blast. According to AGT, film requires replacement after failing a ‘peel test’ or after a maximum of ten years.
“Security film acts as a protective skin on windows but as they are constantly exposed to sunlight, UV rays and also temperature fluctuations start to affect the efficacy of the adhesive over a prolonged period. In the UK, we specify that film should be replaced within ten years and tested at least every five years,” said Westney.
At present, the complete unknown, AGT believes, is how ‘fit for purpose’ existing installations are. A culture of ‘fit and forget’ and the absence of documented ‘peel test’ records has the potential to put lives and property at risk in the event of a major incident.
It’s vital that maintenance records are checked to ensure that installations remain up to the job. Security film is an effective and proven means of protecting occupants and property but it has a limited lifespan and loses its protective capabilities over time. The ‘peel test’ involves the ability of the window film to hold a weight for a designated time before the film detaches from the glass. Correct adhesion is crucial for ensuring the integrity of the film’s protective capability, to contain shattered glass fragments. To do this, a good adhesive also needs tackiness to dissipate energy away from the cracks. Brittle or over stiff adhesive will propagate the concentration of stress at the cracks into the film, which may cause it to tear prematurely, rendering it useless in the event of a blast shock wave.
In AGT’s experience, record keeping is not applied consistently across the industry and there are certainly many installations that require immediate checks. Its advice to property owners is simply this, ‘if the answer’s unknown then pick up the phone’.
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