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PRACTICAL WORK №7

ESTIMATION OF THE INDUSTRIAL OBJECTS STABILITY TO THE
IMPACT OF AIR SHOCK WAVE

1 OUTCOMES
Become familiar with parameters of air shock wave, methods of reducing its
force, and carrying out of the necessary calculations for assessment of stability of
industrial objects to the impact of air shock wave.

2 DURATION OF CLASS
The class duration is four academic hours.

3 BASIC THEORY
3.1 Interaction of the air shock waves with ground objects
This practical work considers the influence of the shock wave on an
elements of the object surface (building, construction, equipment, apparatus and
other items), since explosive impact in the general case – are variable in time and
space. So the work in assessing the impact of the air shock wave on an element of
the object (building, structure, equipment, apparatus and other items) to take into
account the force as result from the action of the air shock wave and reaction
which expressed as a deformation of object structure. Analyzing the dynamic load
of the shock wave and the law of its change over time, depending on the location
of the considered building, structure or a single subject design features of the item,
its shape, size, strength characteristics, internal structure, as well as the parameters
of the air shock wave, and action loads flow, are defined as mainly by the

maximum overpressure in the shock wave.

3.1.1 Shock wave
The shock wave is a region of strong compression of air heated to several
million degrees, propagating at supersonic velocity (335 m/s) in all directions from
the center of the explosion.
The source of the shock wave is a high pressure in the center of the
5
explosion, reaching 10 billion Pa.
It consists of areas of compression (where the pressure is above
atmospheric) and the zone of underpressure (pressure below atmospheric). The
damaging effects of the shock wave is determined by two parameters:
overpressure, and dynamic pressure of the air (velocity head air).
Overpressure ΔP is the difference between normal atmospheric pressure
f
before the wave front P and the maximum pressure in the shock wave front P ,
0
f
i.e.:
ΔP = P — P , kPa (7.1)
f
0
f
Unit excess pressure in the SI system is the Pascal (Pa), non-system unit of
2
2
4
kgf/cm , 1 kgf/cm = 9.80665 10 Pa ≈100 kPa.
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