A History of Research and a Review of Recent Developments

The stability of masonry walls under the action of blast from conventional
explosives was examined experimentally in a series of tests in the late 1970s
and early 1980s in the USA. Collapse mechanisms were recorded, as well as
the nature and distribution of debris from shattering walls, and a range of
construction was investigated, varying from load-bearing masonry to reinforced
concrete frames with a masonry infill. These tests were summarised by Rempel
and Beck [8.13], who also analysed crushing energy and wall rotation.
Attention was also paid to the design of explosive storage facilities constructed
of masonry, including overpressures to cause incipient failure and safe separation
distances between storage facilities and neighbouring buildings of brick, masonry
and prefabricated blocks. The state of affairs in the early 1980s was reviewed by
Napadensky and Longinow [8.14]. They quoted current US regulations, which at
the time permitted conventional, inhabited buildings to be located at distances of
40 W 1/3 to 50 W 1/3 ft from an explosives store, where W is the weight of explosive in
pounds. For long-duration pressure/duration blast loads that would be experienced
in a nuclear explosion, incipient failure overpressures (where the structure will fail
under any additional load) was given in terms of probability of failure as follows.
(a) Light commercial buildings with masonry load bearing walls: 2.0; 3.2; 4.9
psi for failure probabilities of 10%, 50% and 90% respectively.
(b) One-storey masonry load-bearing wall: 1.8; 2.8; 4.6 psi for failure
probabilities of 10%, 50% and 90% respectively.
Safe separation distances, peak overpressures and impulses, for a range of
non-nuclear explosions, were tabulated by the authors for a range of targets.
Excerpts from their survey are given in Table 8.3.
The authors compared the damage, pressures and distances with the recorded
effects of the Flixborough vapour cloud explosion in 1974. Damage analysis
Table 8.3
Civil buildings 189
(Separation distance in ft; overpressive in psi; impulse in psi ms)