Dynamic Behavior of Concrete: Experimental Aspects - Dynamic Behavior of Concrete and Seismic Engineering - page 32

submitted to a shock are used. This is especially the case when validating
radioactive waste containers ([LAE 94], [VEC 88]). In order to anticipate the result
of this kind of test, simplified analysis methods have been developed ([MAR 87],
[SER 98a]), and these allow parametric study when designing and developing
prototypes. This experimental configuration allows good control of energy during
the shock, and confirmation of the hypothesis when the impacted area is motionless
and dimensionally stable. On the other hand, fitting structures with the required
instruments for this is generally expensive and difficult (on-board accelerometers);
consequently, identifying the analysis should be based on a posteriori observable
cracking state.
1.4.2.3. Explosion resistance test
For a number of protection structures, overall dynamic loading is more
significant than a local impact. Adapted large-scale experimentation is carried out
via pressure loading caused by an explosion. Control of such loading and its
similarity rules is rather good, subject to limit conditions and simple structure
geometry, which limits uncertainties linked to reflections. In this kind of experiment,
instrumentation can be quite complex (numerous pressure sensors , gauges,
displacement sensors and accelerometers). The most important factors are the data
acquisition speed, and the qualities of activation and filtering. Many experiments
have been carried out on typical structures, including structural walls and slabs
([GRO 90], [KR 96]), vaults and tunnels [KRA 89] and hot caves. Controlling the
mechanical limit conditions is the main difficulty for obtaining a precise inverse
analysis in such cases; therefore, this kind of test is often used for validating
simplified regulations and abacuses for the dimensioning of protection structures.
Another category of tests carried out using blasting charges is aimed at
characterizing the “compaction” behavior of a material, the latter being closest to the
blasting charge in a highly confined stress state due to the pressure resulting from
the explosion nearby on the one hand, and to the rest of the surrounding structure not
yet hit by the loading wave. Such tests are transient, and the analysis requires re-
calculation (made easier by the semi-spherical symmetry of the problem). The data
is generally adapted to a volume-pressure limit curve interpretation, characteristic of
the areas submitted to strong tri-axial compressions. A recent description and
interpretation of such tests can be found in the works of the GEO network [BAI 99].