A History of Research and a Review of Recent Developments

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Response, safety and evolution
resistance factor might be reduced to about 1.3, giving an overall factor of
1.95. This is close to the factors produced in the reliability based air-blast
analysis described earlier.
The work on reliability-based design is still continuing, and no doubt
there will be adjustments to the proposals of Twisdale and others as time
goes on, particularly as more test information becomes available and as
analytical ideas progress. It is encouraging to know, however, that modern
load and resistance factor design has now entered the world of structural
assessment under blast and penetrative loading, as it has for buildings,
bridges, aircraft and ships under dynamic loads due to wind, waves and
earthquakes.
9.4 EVOLUTION
We have now examined the gradual assembly of information on the explosive
loading of structures over two centuries and more. As in many other subjects,
the march of progress has not been gradual and well-conditioned. There have
been periods of intense activity followed by years of rest and recovery, not
unlike the growth patterns of nature which so often consist of steep gradients
and level plateaux. From the analytical and experimental viewpoints, major
progress was made at the time of two world wars and the nuclear cold war,
when money was available for the very costly activity of full-scale field testing.
Theories and analysis are subject to swings of fashion, but the results of wellconducted
tests have a lasting value.
There are psychological problems when a field of research is connected
with an activity considered to be associated with physical danger, or with the
pursuit of war or terrorism. A background of uncertainty can sometimes lead
to a superficial consideration of basic engineering or scientific principles. Much
has been written in this book about the behaviour of engineering structures,
but less about the behaviour of structural engineers. Perhaps future research
will examine this problem in greater depth, and the subject has been explored
by the author in a series of short stories.
Future work on the shock loading of structures is likely to continue at a
steady rate as the train of research moves on to its next stop. On the way it is
expected to journey through fields of risk and reliability, modelling laws, new
instrumentation, and the computer simulation of large-scale testing. There is
also a considerable interest now in the prediction of fragment loading and
damage, and in penetration mechanics.
At the time of writing these closing remarks the 8th International
Symposium on the Interaction of the Effects of Munitions with Structures
has just taken place in the USA. A glance through the agenda shows that,
very approximately, about half the papers dealt with structural response
and protective design, about one quarter with penetration and fragmentation,
and the remaining quarter was divided about equally between blast loading