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Terror-proofing the UK's buildings: the contractors' perspective

What does improving the built environment’s resilience to terrorism actually mean for the construction industry? CN speaks to three expert contractors about the measures they install and how the climate is changing.

Last month a report backed by the mayor of London urged the government to consider introducing a law to make new buildings more resilient to a major terrorist attack.

That same week, Construction News interviewed WSP Parsons Brinckerhoff’s head of security consulting Chris Driver-Williams, an ex-SAS and MI5 counter-terrorism officer, about the threats to buildings and how they can be mitigated.

It is clear this is an issue contractors need to think about, if they aren’t already, particularly when building in London and other major cities. But when it comes to delivering these extra-resilience measures on the ground, what does it actually look like?

Ring of steel

One main contractor with more reason than most to prioritise threat mitigation is Canary Wharf Contractors, which oversees the majority of projects on the Canary Wharf estate – as well as branching out to other major projects in London such as the Walkie Talkie and the Shell Centre redevelopment.

Canary Wharf Group company secretary John Garwood says that, as a contractor, it works with the tenant of a building from an early stage to identify its individual security requirements – but that the ‘ring of steel’ on the estate helps mitigate risk for buildings built there.

“Generally the arrangements we put in place to protect the estate and the exterior of the buildings obviate the need for further security enhancement of the building itself, but occupants’ security strategies vary depending on their perception of risk and threat, and we respect and recognise that they may require further provisions to be incorporated,” he says.

“We like to get involved as early as possible to make it as aesthetically pleasing as possible”

Iain Moran, ATG Access

The Canary Wharf estate provides a prime example of the layered system of defences that are in place to protect buildings away from their footprint (see box), aiming to stop threats before they get close.

On the inner layers, it’s important to stop hostile vehicles in their tracks – while on the building itself, thought has to be given to the materials used on the facade and envelope to mitigate any damage that might be done should the worst happen.

Blending in

ATG Access is one of the companies that installs hostile vehicle barriers. It designs the systems from scratch, meeting whatever requirements are set out by the client, taking the product through testing before installing it where appropriate.

If it’s an active system, ATG also carries out the civil installation and electrical commissioning in-house, before servicing and maintaining it once it’s handed over from the construction company to the client or end user.

“These products can take a variety of forms, from the humble bollard to being integrated into large letters or other landmarks,” says ATG Access national sales manager Iain Moran. “We like to get involved as early as possible to make it as aesthetically pleasing as possible.

“[Clients] want people to know they’re entering a secure environment, so they’re leaning back towards having the ring of steel that looks like bollards”

Iain Moran, ATG Access

“We’ve got integrated lighting columns that are approved by Transport for London, beacons for pedestrian access, lighting and CCTV columns, even integrated London Underground roundel signs. We can incorporate that strength and integrity into any kind of structure.”

Aesthetic concerns are also of vital important to Wrightstyle, a glazing subcontractor which specialises in blast-resistant glazing, among other things.

“Our system for blast protection, which is structurally glazed, has the same appearance as any other commercial system, whereas normal blast systems are quite heavy in their construction, which gives the appearance of being a protected enclosure,” says Wrightstyle technical director Lee Coates.

“With our stuff, you wouldn’t know the difference. Architects tend to like that, and on historic or listed buildings, that becomes quite important.

“We did a lot of work at King’s Cross on the south facade development, for example, where they wanted to mitigate the visual impact on what is a historic building, but still provide high protection for its users.”

CREDIT Wright Style_Kings Cross station 1

CREDIT Wright Style_Kings Cross station 1

Source: Wright Style

Wrightstyle’s blast-resistant glazing on the facade of King’s Cross station in London

Mr Moran says “more and more” clients want security blended into the street furniture, but that since the marauding attacks in Paris last year, there has been a slight shift back on certain types of projects.

“On stadiums, say, [clients] want people to know they’re entering a secure environment, so they’re leaning back towards having the ring of steel that looks like bollards,” he says. “These attacks have been very high-profile and people are more conscious of them, and therefore more familiar with the types of measures and security lines that are in place to offer them protection.”

As Mr Garwood puts it, whatever it looks like, security must be delivered so that the public are “reassured, not alarmed”.

Stopping vehicles

One aspect of these measures that does not vary is the rigorous testing that takes place prior to installation

On the hostile vehicle side, products are tested using the IWA 14 standard (International Workshop Agreement). Barriers are rated based on the weight of the vehicle they can stop – either 1,500 kg, 2,500 kg, 3,500 kg, 7,500 kg, 18,000 kg or 30,000 kg – and its impact speed, ranging from as low as 32 kph up to 80 kph.

“It’s a very delicate balance and there’s no national standard you can comply with to say it’s blast or ballistic-rated – it’s very much on an individual development basis”

Lee Coates, Wrightstyle

“As a designer and manufacturer, you can test your product at any speed for any of those vehicles to get certification,” Mr Moran says.

“A security consultant would determine that a vehicle of a certain size could hit a building at, say, 80 kph, in a certain location. We take that information along with the architectural requirements and the site constraints to deliver a product that is suitable.”

The strength and integrity of the hostile vehicle barriers produced by ATG comes from their core, which is predominantly made of mild steel.

“We have impact-tested cores above ground, of various different shapes and sizes,” Mr Moran says. “Then below ground is our shallow-mounted ‘biscuit’ technology, which is a number of different elements of steel that create a biscuit that, when impacted, absorbs and spreads the load across the foundation.”

Traditional reinforced concrete foundation products need deeper foundations. But with shallow-mounted technology, ATG says it can stop a 7,500 kg vehicle travelling at 80 kph with a depth as shallow as 150 mm below the finished surface.

ATG Access Cityscape Gate

ATG Access Cityscape Gate

ATG’s Cityscape Gate can stop a 7.5-tonne truck travelling at 70 kph

“It’s effectively a shallow frame made up of steel beneath the surface. The bollard links to it, which then links to the next one underground, and they get their strength and integrity from each other. That’s how we can achieve the strength at such a shallow depth, and with so little penetration.”

This is especially important in the centre of London, where the presence of numerous utilities and tunnels means that shallow foundations are a big positive.

On the outside

For the facade, Wrightstyle also tests its products rigorously to ensure they will stand up to an attack

“The first and most important thing is the glass,” Mr Coates explains. “That’s the largest area that will have an effect from a ballistic or blast attack.

“We must be ready for the next event, not the last one. You could say the greatest threat is a lack of imagination”

John Garwood, Canary Wharf Group

“But people forget that equally important is the framing system, and how the frame retains that glass under a blast or ballistic load. Glass obviously breaks, and when that happens – particularly as a laminate substrate – it goes into what we call a membrane action, so it’s immediately going to try to detach from the frame as it’s no longer a solid.”

Wrightstyle thus has to design the glass and framing to consider all of this – if it builds up the glass too thick, it won’t break, which will put more load on the frame, which in turn will put more load on the structure it’s fixed to and produce knock-on effects.

There are national standards for both live blast testing and ballistic products, which Wrightstyle tests its products against, but they do not provide guidance on where and how the products should be used (as opposed to regulations on fire-rated products, for example, which dictate where they are required and what tests are acceptable).

“It’s a very delicate balance – it’s very much on an individual development basis and it has to be considered as that,” Mr Coates says. “That’s why you don’t see quite as many companies getting involved in it, as there is a lot to consider.”

CREDIT Wright Style_Kings Cross station 2

CREDIT Wright Style_Kings Cross station 2

Source: Wright Style

The first and most important thing is the glass, according to Wrightstyle – this is the largest area that will have an effect from a blast attack

When testing, the glazing will behave very differently depending on what size is considered, because an explosion will send out a spherical wave of rapidly expanding pressure that will wash over the entire assembly.

“How big it is will affect how long the pressure stays on it – testing a 1 m x 1 m window is very different to testing the whole facade of a building, as on the whole façade the pressure is going to take longer to wash over the surface of the building, so the pressure stays on it longer,” Mr Coates says.

“There are other effects as well – after a blast, you immediately get a negative load, a suction, so not only does the system have to be designed to resist the initial load, it’s got to also resist it from being ripped out of the building envelope itself.”

The contractor has undertaken a number of live blast tests, too, to test its products (see below).

Source: Wrightstyle

Wrightstyle’s contract depends on how the main contractor wants to manage the build.

“Some will split the package out as they recognise the specialist glazing is the highest cost and that it’s better to do it directly with us,” Mr Coates says. “But sometimes the contractor wants to only manage one [facade] package, so he will let the entire facade to a facade contractor, who would then sub-let the package to us and we will manage that part for them.”

Heightened mindset

Since the Paris attacks last year, there has been a heightened awareness of the risk of terror attacks on UK buildings – especially of those similar to the marauding-style attack that was carried out in the French capital.

And the mayor-backed report published in October only emphasised the need to think about security further.

“It all depends on the building usage – people are certainly more aware of it and considering it at design stage, which is great, as doing it retrospectively is often difficult,” Mr Coates says.

ATG Access Heart of Doha

ATG Access Heart of Doha

ATG Access installs hostile vehicle barriers from scratch, including this system at the Heart of Doha project in Qatar

Mr Moran agrees, saying that he doesn’t expect demand for his systems in the UK to slow down at all this year. “We’ve just completed our half-year and our figures are above where we thought we’d be, and the forecast for the next six months is about 25 per cent up on where we thought we’d be in the UK alone.

“International is also a huge growth area – we manufacture in the Middle East, Singapore, and Brazil and we now export more than we do in the UK.”

For a contractor-client such as Canary Wharf Group, Mr Garwood acknowledges that the marauding style of attack is one of the biggest threats and that, despite the extensive measures taken on the estate, “no-one can afford to be complacent”.

“We must be ready for the next event, not the last one,” he says. “You could say the greatest threat is a lack of imagination.”

Protecting the Wharf

“The layered defence of Canary Wharf starts right at the perimeter,” Mr Garwood explains. “Permanent checkpoints control all vehicle access routes onto the estate. They are equipped with explosive particle detectors, automatic number plate readers and hydraulic vehicle blockers.”

Canary Wharf’s security teams stop, search, swab or interact in some way with around one million vehicles a year, with all delivery vehicles required to be booked in and potentially searched.

This ‘ring of steel’ is reinforced by a system of hostile vehicle blockers on the estate’s exit lanes, which will deploy within less than a second should entry be attempted that way.

Within the ring, uniformed officers patrol across the estate’s public areas, while a specialist covert operations team functions throughout the estate, focusing mainly on potential hostile reconnaissance and criminal activity.

As an added measure, explosives detection dog teams patrol the area, with 1,700 CCTV cameras and more than 1,000 alarms providing additional security.

“We have a 500-strong security force, approximately one security officer for every 220 people on the estate, which is the best-serviced area for security, per capita, in the UK. As a consequence Canary Wharf has the lowest crime rate in London,” Mr Garwood says.

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