Dynamic Behavior of Concrete: Experimental Aspects - Dynamic Behavior of Concrete and Seismic Engineering - page 31

operation is a bending mechanism, though with some inherent complexities [KRA
93]. We need to consider:
- operation as a slab which cannot be reduced to a beam operation;
- plate operation (diaphragm effect);
- possible local mechanisms depending on the shock range and energy (local
crush, punching or transverse load failure on the supports);
- sensitivity to the support conditions (problem linked to the dynamic unilateral
support conditions);
- problems linked to the resilience of the impactor;
- sensitivity of the failure mode to singularities (corner effects).
As an example of the extra information that can emerge if the above points are
considered, an important sensitivity of such tests' overall results to the “nose-
shaped” impactor [BIN 01] has been shown, with a part of the impact energy being
consumed when starting a penetration mechanism [WAT 02]. When a complete
inverse analysis can be conducted, notably with well controlled loading and limit
conditions, the competition between the different damage and collapse mechanisms
can be highlighted according to the impact speed, which was especially the case for
reinforced concrete walls submitted to the impact of a pendulum in [MIY 91a] and
[MIY 91b].
As regards validating complex systems [SAT 95a] comprising a concrete
structure (reinforced or pre-stressed) and/or supports interacting with the ground,
tests where impact is achieved by means of a falling mass are often used [PER 01],
the ability to control and modulate the incident energy (blocks ranging from a few
tens to several hundreds of kilos, falling heights up to 30 m - limitations due to the
sizes of cranes) must be taken into account. Re-calculating the test is often difficult
because of the frequent presence of dissipative materials (ground, granular materials,
energy dampers). Research into systematic empirical interpretations worthy of note
(especially with a view to dimensioning rock fall devices to protect transport
infrastructures) includes [LAB 96], [MIK 95], [MON 98] and [SAT 95b].
1.4.2.2. Block fall tests
If we want to collect exploitable information about the participation of the
different materials and components in the overall strength, tests on structure
elements require an inverse analysis, which is often complex in dynamics. However,
in so far as the load and the test body are close to the “real” situation, some tests are
used directly, to confirm and/or compare various technical solutions. In a manner
complementary to block-falling tests, tests where the concrete element itself is