Models for Explosions from Terrorist Attacks Could Reduce the Carnage

By | June 25, 2015

While catastrophic event models mainly focus on weather related events, the world also has to cope with catastrophic terrorist acts, particularly those caused by explosive devices placed in areas where they will cause the most damage and kill the most people. Bombings like those in Beirut, Kenya, Oklahoma City, culminating in the September 11 attacks on the World Trade Center, pose a threat to society that is far more sinister than the weather.

Mark Lynch Impact Forecasting’s terrorism expert explained the work he and his team have done in modeling the potential effects of explosions. “Blast modeling has improved exponentially, and the insurance industry needs to use it,” he told delegates at a breakout session he chaired at Aon Benfield’s Impact Forecasting’s recent conference in London.

Lynch explained that the type of explosive used, the weight/volume of the charge and where it could potentially be placed all have to be considered in creating the models. “The blast [pressure] wave propagates through urban geometry, i.e. where the force of an explosion goes is where it finds the space to do so. “Tracking the pressure impulse curves enables us to calculate the damage.

“The difference in the curves also depends upon the type of construction and the materials used,” he continued. The most serious damage – level 3 – is a total building collapse, which is also the cause of the greatest loss of life.

"Blast modeling has improved exponentially, and the insurance industry needs to use it.” Aon Benfield terrorism expert Mark Lynch

In addition to the direct damages caused by a blast, which is essentially property damage, it can also result in business interruption and denial of access to the damaged premises. In some cases it can cause contingent business interruption (cbi).

The models are constructed not only to predict potential paths of damage, but also to identify weaknesses in planning and construction that can be mitigated to reduce losses. The models Lynch is working on incorporate “electronic mass casualty assessment and planning scenarios (EMCA & PS).” These are global applications that can be used to construct models anywhere in the world.

Lynch introduced Nick Misselbrook, an associate with Weidlinger Associates Ltd., who heads the company’s modeling and simulation team in the UK. His biography notes that he specializes in “vulnerability assessment and consequence analysis of buildings and other structures to terrorist attack, including counter-terrorist design of these structures.”

That’s a much understated way of describing Misselbrook’s presentation. His slide show featured graphic pictures of the extent of damage caused by the Oklahoma City bombing and the attack on the twin towers of the World Trade Center.

The attack on the Alfred P. Murrah Federal Building on April 19, 1995 killed at least 168 people, injured more than 680 others, destroyed or damaged 324 buildings within a 16-block radius, as well as setting cars on fire and shattering glass. Estimated damages were $652 million. It was the most serious terrorist attack in the U.S; – until the attack on the World Trade Center.

Misselbrook’s most harrowing slide, which few in the audience will forget, was a very realistic simulation of an exploded aircraft inside one of the buildings. He explained that the buildings weren’t brought down by the force of the crash or the explosion of tons of kerosene fuel, but by the fire which destroyed any systems capable of suppressing it, resulting in the weakening and eventual collapse of both structures.

These tragedies offer lessons in what incorporating pre-planning scenarios in building construction and location might achieve in reducing loss of life and property damage. Misselbrook pointed out that while UK standards mandate blast and structural analysis of larger buildings, the U.S. does not. This isn’t surprising, however, given that building codes vary from state to state and from city to city.

It is entirely possible to prevent and mitigate some of the damage from bomb blasts. Lynch explained that even one millimeter of laminate reduces the effects of the explosion significantly. Securing windows properly could almost eliminate the destructive effects caused by shattered glass.

The first concern remains the structural integrity of the buildings. There are designs that can minimize the possibility of a building collapsing because there are weak parts in the structure that can give way and trigger a total collapse. There are ways, such as barriers to underground parking garages that would seal off some of the most vulnerable areas of attack.

All of those measures and more begin with “protective assessments,” Lynch said. Unfortunately the re/insurance industry has been slow to incorporate this kind of analysis before policies are issued. It’s time that it realized the value of doing so.

In the UK, however, Pool Re, the cooperative reinsurer set up by the government after a series of IRA bombings in the 80’s and 90’s, encourages insurers to conduct them by giving discounts on premiums for those who do a “full building analysis.”

It’s often said the “where there’s a will there’s a way.” As far as blast mitigation is concerned, Lynch, and others who have addressed the problem, have described a number of ways. Now it seems that what’s needed is the will.

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