A History of Research and a Review of Recent Developments

Introduction xxix
particularly damaging when peak overpressures exceed 315 KPa. The response
of structures and the humans in them to nuclear explosions is therefore a very
complex design field, and the engineering of the subject is often left to physicists,
with questionable results.
Another field of interest is what might be termed civil explosions. These
are non-military or non-terrorist explosions which are either the result of
accidents due to natural forces or deliberately produced to aid the requirements
of civilized society. The most frequent accidental explosions are probably due
to domestic gas leaks, and there have also been accidents due to the ignition
of methane gas in civil engineering works and mines. In Britain much structural
research has centred on the former Building Research Establishment. Many
reviews and reports have been written on the nature of serious gas explosions
and structural disasters are well documented. The action of domestic gas
explosions is nearly always from within the structure, and in structures that
are badly designed with respect to progressive collapse a relatively small
explosion can lead to spectacular results. The collapse of a high stack of corner
rooms at the Ronan Point high-rise apartment building in London following
a gas explosion led, in the 1960s, to a formal enquiry and adjustments to
future design requirements for all types of building. Internal gas explosions
are unfortunately still a regular occurrence, often resulting in the death of
house or apartment dwellers.
The possibility of internal explosions also occurs in buildings that house
test facilities for engines, and here it is good practice to limit the instantaneous
pressure rise of the explosion by using weak panels in the superstructure that
will collapse outwards. Other industrial manufacturers who require protective
construction in their facilities are the producers and storers of explosive
materials. The possibility of an accidental explosion causing detonation of
other explosive devices is a hazard that has to be carefully examined at the
building design stage. Hardened buildings that limit the propagation of mass
detonations are usually constructed of reinforced concrete with steel blast
doors. There are regular conferences, particularly in the USA, on protection
against the accidental explosion of hazardous mixtures, and safety control in
this field is becoming increasingly important in most countries.
Another civil hazard is the unconfined vapour cloud or dust cloud explosion,
which has often resulted in a major national disaster. In Britain the on-shore
explosion of the Flixborough chemical plant and the off-shore explosion at
the Piper Alpha oil rig have caused much damage and loss of life. Explosions
of this type cause secondary damage due to fragmentation, fire and loss of
structural stability. There is always much publicity and speculation when large
cloud explosions occur, and the political pressures to find the causes and
distribute the blame are usually as intense as the explosion itself. Smaller
explosions of this type have occurred from time to time in ships, under cargo
conditions that are not always foreseen as dangerous. The problem of design
against accidental explosions has been addressed by the US Department of