Protecting buildings from terrorists, disaster

EYES glued to the television screen, Professor Pan Tso-Chien watched the haunting image of smoke billowing from the Twin Towers of the World Trade Center in 2001.

An enemy that had lost its sense of humanity had struck the United States. Al-Qaeda terrorists had deliberately rammed two aeroplanes into the World Trade Center on Sept 11, 2001, killing more than 2,800 people.

He reeled in shock, just like many ordinary folk. "I thought it was a scene from a Hollywood movie," he says.

But, he went further. He began taking mental notes of the time the crash occurred and the time it took for the towers to crumble. He also noted that the copious black smoke pouring out of the buildings was caused by fuel.

His conclusion: The two towers, at 110 storeys each, remained standing for more than one hour, proof that the buildings were not structurally faulty.

The collapse that came later lasted a mere 10 seconds, and resembled a stack of pancakes being driven swiftly into the ground by an invisible piling hammer.

Prof Pan, executive director of the Institute of Catastrophe Risk Management at the Nanyang Technological University (NTU), concluded that the cause of the building collapse was the fire.

It was ignited by the massive amount of aviation fuel - more than 90,000 litres - the two aeroplanes were carrying when the collision occurred.

Even though the aeroplanes crashed into the main columns supporting the building, the weight of the building shifted to the other columns. So, the buildings were structurally strong, he reveals.

It was the heat of the inferno that burned at more than 800 degC that distorted and weakened the steel structures that held the building together.

Considered an engineering feat when construction ended in 1973, the Twin Towers were designed to endure strong winds and even an aeroplane crash.

But, here is the catch: There was no way an engineer in 1973 could predict the size of aeroplanes or the amount of fuel they could potentially carry in 2001, he says.

Engineers design buildings on what they know now, and plan for ways to survive disasters in an unknown future, adds the soft-spoken Prof Pan, 60.

He and his team of researchers in the institute study the risks related to natural and non-traditional catastrophes, such as earthquakes, tsunamis and typhoons.

Planning for a fall

PROF Pan is a much sought-after engineering expert locally and internationally for his knowledge in protecting infrastructure from natural and man-made disasters.

Assessing damage to buildings, studying structural designs for buildings to withstand missile impacts and protecting infrastructure from seismic hazards keep the urbane professor occupied.

Can engineers build a perfect building that can withstand any form of damage?

The aim is always to build a strong building that will not fail, he states. "But, at the bottom of our hearts, we should always remember that failure is almost inevitable.

"I just want to make sure that when the building is going to give way, it should fall in a controlled way. I won't really want it to crash down without any warning.

"I would love the building to say, 'Hey, I am falling, please run away from me'. That is the bottom line of all building design," says the professor.

This can be achieved by having a strong structural design that will enable the building to stand for a long period.

Cost matters

RESEARCHERS at the institute, set up in 2010, aim to provide better understanding of the types of risks related to natural and non-traditional disasters or threats. These include earthquakes, tsunamis and typhoons, as well as non-traditional hazards such as infectious diseases.

A white board in Prof Pan's office in NTU is filled with dates of meetings scheduled with officers of the Monetary Authority of Singapore, and ministries of National Development and Home Affairs, as well as security experts from the S. Rajaratnam School of International Studies, among others.

At meetings attended by engineers, town planners, security officers and economists, the issues of which building to protect and at what cost are discussed.

The teams also consider ways to protect nearby buildings that can be damaged by a falling building, and how buildings that are already constructed can be reinforced.

Prof Pan studied civil engineering and graduated from the National Cheng-Kung University, Taiwan, in 1975. He later received his master's in structural mechanics and PhD in structural dynamics and earthquake engineering from the University of California, Berkeley, in 1978 and 1983, respectively.

Now an American citizen and a Singapore permanent resident, he is often travelling, giving talks on protecting buildings.

Among the numerous boards and committees he sits on are the Cambridge Centre for Risk Studies in Britain, the Research Institute for Sustainable Urban Development in Hong Kong and the OECD Global Earthquake Model Foundation.

Deadly projectiles

INFRASTRUCTURE protection has become an integral part of a country's defence against terrorism. Damaged buildings need to remain standing for a long time so that people can escape, he says.

When a bomb explodes, devastation and death can be caused directly by the bomb. People can also be killed by shrapnel from glass fragments or parts of the building.

For example, in the bombing of the United States Embassy in Nairobi, Kenya, lethal shrapnel killed 224 people and wounded 4,650.

To protect buildings from bombs, Prof Pan says several features can be included in the building design. For example, to reduce the risk of large dagger-like glass shards from flying through the air and killing people, tempered or laminated glass can be used.

The film that coats the glass panels will trap the broken bits.

To reduce the build-up of pressure created when a bomb goes off, the aluminium window frames anchored to buildings can be designed to move about 1cm back. This will reduce the pressure on the buildings and prevent building parts and glass from shattering.

Highlighting the difficulties in planning a super-building, he says: "You don't want to over-design because it will cost a lot, or under-design a building.

"We need to design for a possible attack that might come 50 years later, or it might not come at all."


I just want to make sure that when the building is going to give way, it should fall in a controlled way. I won't really want it to crash down without any warning. I would love the building to say, 'Hey, I am falling, please run away from me'. That is the bottom line of all building design.

- Professor Pan Tso-Chien

Minimising damage

THE following design features will help deter a terrorist attack or minimise the destructive potential if one should actually take place.

•Road design: Never build a long and straight road that leads to the entrance of a building. Design winding roads instead that will slow down vehicles.

Force vehicles to travel along the serpentine path by planting trees along the route. Include speed humps and vehicle barriers.

Avoid including underground carparks. Locate carparks far away from buildings.

•Landscape: To slow down the movement of terrorists towards a building, have water features such as small ponds. Earthen berms, hedges and walkways are also good barriers. Always preserve the line of sight so that security officers can spot suspicious-looking persons.

To enhance building security, have plants like the red barberry, a dense spiny shrub, to block the paths to the entrance. Palm trees are also good. Terrorists cannot hide behind the tree as its leaves are at its top.

•Interior design: Scientists have created blast-proof curtains. The curtains, a few millimetres thick, can self-adjust to absorb the impact of a blast. They can also catch flying debris.

A flexible wallpaper that can withstand the impact of a wrecking ball is the brainchild of the United States Army Corps of Engineers and a private company.

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