THE PROTECTION OF BUILDINGS AGAINST TERRORISM AND DISORDER

Terrorism and public disorder have increased in Britain in the past two decades. Although terrorism is not a recent phenomenon, the modern terrorist has more powerful resources at his disposal than ever before, and the likely threats that a terrorist could employ against ordinary buildings are listed. Also, it is argued that public disorder has merely returned to levels which were common in the 19th century. The significant point, however, is that many public and corporate buildings were constructed at a time when the threat from terrorism and disorder was slight, and, as such, they offer little inherent protection. The majority of terrorist attacks employ explosives, and the distinction is made between low order, or deflagrating, and high order, or detonating, explosives. However, it is argued that, in the quantities necessary to attack structures, the explosives employed by terrorists behave as detonating high explosive materials. The nature of blast loading is described, and the dependence of the structural response on the relative duration of the blast load and the structure's natural period of vibration is emphasized. Pressure-impulse isodamage curves may be constructed for particular structural forms to predict the damage level from a particular threat. In order to protect people against terrorism and disorder, buildings should not collapse catastrophically, they should not burn out of control, and people should be protected against flying fragments. Protection may be achieved through structural design, with an appropriate selection of materials and structural form, together with adequate elemental and joint detailing. The protection afforded by the future building stock could also be enhanced by some modification to current legislation in the form of Building Regulations and the associated approved documents. Finally, the use of different building arrangements to achieve protection is discussed.