Dynamic Behavior of Concrete: Experimental Aspects - Dynamic Behavior of Concrete and Seismic Engineering - page 47

traction strength increase, which enables us to calibrate a visco-elasto-plastic model
with viscous strain-hardening, and application of dynamic failure mechanics when
high-rate failure propagation is at stake. The choice of the behavior description level
seems to be consistent with a clear choice of other modeling hypotheses: speed
range of the considered strains, unique or repeated characteristic of the dynamic
stress, presence or absence of uniaxial behavior, presence or absence of
reinforcements, possibility or impossibility of limiting the justification validity in a
domain where concrete can still be considered as continuous, etc. Depending on the
circumstances, we will naturally turn to a different description level with a more or
less important integration of chance in the properties of the material.
After taking these considerations into account, as well as considerations dealing
with dimensioning an important number of structures and increasingly considering
fortuitous situations ([PER 01], [TRO 01]), we underlined a few shortcomings. First
we have seen how difficult it is to access the material under high tri-axial stress.
However, it is a crucial problem for direct impacts, areas close to an explosive
charge or in cases of potential penetration. As for validating “viscous strain-
hardening” hypotheses, and in order to better model the combined effects of inertial
confinement [UNO 02], more complete information in the field would be quite
helpful as well.
While understanding the mechanisms in the case of a single dynamic stress can
be considered as correct and reliable for calculations, the problem of repeated
impacts remains difficult, both for validating the potential progressive damage
predictions models are likely to supply, and accurately taking into account the
evolution of adherence for reinforced concrete structures. This field seems to
represent very important stakes for engineers, in the frequent cases of fortuitous
dynamic stresses.
Finally, the increasing range of materials coming under the definition of
“concrete”, including fiber reinforced concretes, high and very high-performance
concretes and ultra-efficient fiber-cement composites will demand more diversified
validation of the indications and mechanisms highlighted in this synthesis.
1.7. Bibliography
[ALE 94] ALEXANDRE M., “Etablissement du cahier des charges d'un conteneur de haute
intégrité pour l'entreposage de longue durée des déchets B en vrac”, Rapport de la
commission pour les questions scientifiques et techniques relatives à la gestion des
déchets radioactifs auprès du conseil scientifique du CEA , March 1994.