黑洞社区

Three years of terror

Of all the images of terrorism, the sudden collapse of Manhattan鈥檚 twin towers as the buildings鈥� structure suddenly gave way is the most numbing, the most frightening. The fact that it was the absolute destruction of a very public place of work also makes it somehow real and incomprehensible at the same time.

The world, of course, keeps spinning; the world moves on. But the impact of the World Trade Centre attacks is still felt.

Osama bin Laden changing the course of history is obviously far more significant than the attacks鈥� effect on the built environment, but changes within our industry have been perhaps more keenly felt than in any other line of work. Here 黑洞社区 details just some of those changes, which range from structural and design rethinks, through hikes in insurance premiums, to a massive drive to improve security of the places in which we live and work.

Structure

The breathtaking, stomach-churning collapse of the twin towers posed a lot of questions. Engineers had to come up with a lot of answers very quickly if they were to secure work from commercial developers and public bodies: if terrorists could get to a symbol of Western hegemony like the World Trade Centre, tall buildings would have to change, if only to reassure those working in them that they would not share the fate of those in the twin towers.

The major questions surrounded the towers鈥� structural design and the problem of progressive collapse. In particular there were concerns about the robustness of the connections between the buildings鈥� supporting steelwork and the floor structure.

The design of Barclays鈥� 33-storey headquarters in Canary Wharf was at an early stage when the attack on the twin towers took place. In the wake of 9/11, its design was adapted to take on board the latest safety developments.

The building鈥檚 structure, conceived by Cantor Seinuk, a WSP subsidiary and tall buildings specialist, has been hailed by project insiders as 鈥渙ne of the most robust buildings in the world鈥� and a blueprint for future tall buildings. Kamran Moazami, a director of Cantor Seinuk, has called it 鈥渙ne of the best in the world as far as progressive collapse is concerned鈥�. The design has also been used by Cantor Seinuk for Block 7, the first building to go up on Ground Zero.

Most of the Barclays headquarters鈥� structure is fairly conventional; the steelwork frame is attached to three reinforced concrete cores, which climb the full height of the building. What makes this building鈥檚 structure different is that Cantor Seinuk鈥檚 design allows for any two adjacent structural columns to be removed on any floor without endangering the remainder of the building鈥檚 structure.

It was the engineers working in a joint venture between steelwork contractors Victor Buyck and Hollandia that developed the pioneering structure. It uses a 鈥渟trap鈥� to tie the floors鈥� supporting beams together. Usually, floor beams are just bolted to the steel supporting columns. At Barclays, the 鈥渟trap鈥� is a short steel plate pushed through the column to tie together adjacent floor beams (see diagram). So, if a column is removed, the strap will allow the beams to hang from the remaining structure.

The building鈥檚 steelwork is not the only element to have an enhanced specification. The building has two additional fire escape stairs on the perimeter of each floor, each sheathed in protective concrete. The escape staircases are 200 mm wider than normal to increase capacity and help halve evacuation time.

The building has a beefed up central core structure with reinforced concrete walls 400 mm thick 鈥� compared with the more usual 300 mm. The core is large enough to allow the building鈥檚 occupants to take refuge in it in the event of an attack. The core includes a Tannoy system to keep personnel informed of the situation.

Other safety innovations include situating the air-conditioning plantroom on the roof of the building to make it more difficult to introduce biological agents into the air supply, using laminated glass to avoid flying shards in a bomb blast and improving the standard of fireproofing material throughout the building.

Fire

The World Trade Centre attacks have played a huge role in increasing the ability of buildings to withstand fires.

The 9/11 inferno鈥檚 implications for building management and design were identified by industry chiefs immediately after the attacks. The Institution of Structural Engineers鈥� Safety in Tall 黑洞社区s and Arup鈥檚 Extreme Events, both published in 2002, argued that escape procedures and the robustness of structural fire protection required urgent attention.

Industry-led reform has changed the way fire safety is approached. Lifts are considered the quickest method of evacuating tall buildings struck by extreme events. They can aid simultaneous evacuation, which was not possible at the World Trade Centre. Peter Bressington, director of Arup Fire, believes British consultants will soon extend the escape-lift concept to conventional fires. 鈥淥bviously there are additional considerations, such as the problem of smoke inhalation,鈥� he says, 鈥渂ut lifts are already used in this way in tall buildings in China.鈥�

Structural fire protection has also been rethought. Engineers鈥� emphasis now lies on incorporating fire resistance into the structure of the building, rather than relying on fire-resistant coatings. Bressington stresses that the twin tower鈥檚 failure to withstand fire was not an inevitable consequence of high temperatures. 鈥淎lthough intense, the fire wasn鈥檛 remarkably hot for long. Structural damage sealed the building鈥檚 demise. The plane contributed to that, but it wasn鈥檛 the whole issue.鈥� Now, studies monitor the behaviour of structure in actual fires, and future designs are altered accordingly.

In such an adaptive project, it is doubtful whether there is a role for government regulation. The ODPM is due to release its 黑洞社区 Regulations Approved Document B on fire and safety in January. It is uncertain whether any 9/11 issues will be addressed in that, but Bressington thinks some mention of management and training procedures might be made. 鈥淚f they don鈥檛, they could be accused of saying everything鈥檚 perfect,鈥� he says.

There has been criticism that the construction industry has been left to drive reform, with the government nowhere to be seen. But the government may lack the ability to legislate because of the specific nature of tall buildings and extreme events. John Roberts, chairman of the ISE working group that produced Safety in Tall 黑洞社区s, said: 鈥淭he government, with the best will in the world, is very good at ensuring houses have the correct insulation. But it鈥檚 not easy to write codified rules for situations like 9/11.鈥�

There is every sign, though, that the industry can manage for itself. Despite concern over the cost of improvements, tenants鈥� demands ensure reasonable consideration is given to fire safety. Often alterations do not require huge increases in funding. Many existing stairwells can be widened to facilitate simultaneous evacuation. And interest in the issues remains high, even in unexpected quarters. Roberts recently gave a talk on safety in tall buildings to engineers and architects in south-west England. It was surprisingly well attended. 鈥淚f Plymouth and Exeter are interested, you can rest assured concern is still alive.鈥�

Security

It鈥檚 all about fear. For a long time security has been something of an afterthought. But now, terror has led to a drive to make our buildings much more protected.

A top-level security adviser to the government says: 鈥淚t took about six months for everything to sink in. There was a reassessment of the change of the threat. Concerns were raised about suicide devices.鈥�

There were also more 21st-century methods of attack, with biological or chemical terrorism now a possibility. The government adviser instructed that post rooms should no longer be based in the same building as their companies, as biological agents could be delivered through the mail. Often post for government buildings is now handled in mobile buildings away from the rest of the staff.

And if an agent did get into a building, it could easily spread. So public entrances now often have no air-conditioning, or at least have a separate system from the rest of the building.

Although faced with fresh challenges since 9/11, the UK has had a long experience of designing in the shadow of the IRA. Chris Bowes of security specialist TPS Consultancy says that interest in his field of expertise has largely come from overseas: 鈥淚t used to be that 90% of our work was in the UK; now it is much less than that,鈥� he says.

One of Bowes鈥� international projects is one of the replacement towers for World Trade Centre 鈥� but his specialism also takes him as far afield as Hong Kong and the Middle East. The Australian market, in particular, has grown in the wake of the Bali bombings 鈥� Bowes reckons that Australia is at least 10 years behind the UK in securing its built environment.

If the range of international clients has broadened, so the breadth of type of clients has changed, argues John Moore, director of construction and security consultant MFD International. 鈥淭here are more private sector clients. It鈥檚 not just that people consider themselves targets, but the effects if they have neighbours who could be targets. They are secondary targets,鈥� he says rather ominously.

And the techniques these private sector clients can now enjoy have become highly sophisticated technologically. 鈥満诙瓷缜鴖 used to just have a guard sitting at a desk, but now we have things like access control on doors and recognition systems. It鈥檚 now almost unheard of not to have CCTV covering every aspect of a building,鈥� says Edward Lister, general manager of ADT Fire and Security.

An example of the latest thinking on security is demonstrated by the Treasury refurbishment, organised by developer Stanhope and architect Foster and Partners. Here, bomb-blast curtains have been replaced by strengthened windows so that shards of glass cannot fly around. All public space is also on camera.

Another massive issue, of course, is airport security, which has to prevent terrorist hijackings and keep bombs out of cargo bays. Since 9/11, there has been considerable redesign of airport layouts so that extra security facilities can be implemented. But some in the industry want more radical ideas. Peter Farmer, an associate director at Reid Architecture, which specialises in airport design, would like to move cargo facilities to secure areas off site and introduce high-speed rail links to bring cargo into airports.

But there is a problem with such plans: cost. He says: 鈥淭he cargo industry is very competitive; there is marginal profit. The issue of security costs has shot up the agenda,鈥� says Farmer.

Insurance

Whereas most people will have felt traumatised by the sheer shock of 9/11, there were at least one group who were probably thinking in the language of Mammon: the World Trade Centre鈥檚 insurers. The payout to the twin towers鈥� owner, Larry Silverstein, could set new records.

As a result, many at the time predicted that insurance premiums for developers and contractors would go through the roof. Steve Atkins is chief executive of Pool Re, a terrorism reinsurance specialist underwritten by the government. At the time he hinted to 黑洞社区 that the nature of insurance premiums could change: 鈥淎t the moment we don鈥檛 distinguish between types of building. Terrorism insurance is driven by location not construction.鈥�

Atkins admits this has not happened, although there were some talks between the Treasury and Pool Re on the issue of scaled insurance charges for different types of building. What happened instead was more simple: insurance premiums doubled. In central business districts and London, the premium went up from 拢150 per 拢1m of insured value to 拢300.

On the positive side, the insurance was broadened to include biological attacks. Atkins says today鈥檚 insurance covers nearly every eventuality: 鈥淭he only exclusions are war risks and the damage to computer systems caused by viruses.鈥�

The cost issue was predicted by an insurance analyst who talked to 黑洞社区 in 2001. He said that there was likely to be at least a 50% hike in premiums for likely target buildings, such as the towers at Canary Wharf. But that same analyst today says a greater sense of perspective has come to the way insurers treat some industries, and that this could soon return to the building sector: 鈥淚n the airline industry the rates went up for a while, but once some common sense returned they came down again.鈥�

Alastair Nevin is managing director of Wren Managers, which provides professional insurance to architects. In September 2001 he was quoted as saying that clients would have to increase their insurance cover, inevitably driving up construction costs.

Neil Smith from Wren鈥檚 legal team agrees that this has happened, but that the costs have not been substantial: 鈥淚nsurance is an overhead to some extent that鈥檚 going to be passed on, but it is a small percentage cost of a construction project.鈥�

A minor cost or not, penny pinching contractors will doubtless have noticed yet more extra cash they have to pay out as a result of the first world historic event of the 21st century.