Dynamic Behaviour of UHPFRC Used in Protective Structures

Memoria tratta da "The New Boundaries of Structural Concrete: Session B – Controlled-performance concrete", ACI IC - Bergamo 2013

In the field of protective structures, the demand for improved properties of the construction materials increases with time. Ultra-High Performance Fibre-Reinforced Concrete in such structures have been more and more used and investigated. When subjected to fast dynamic loadings, they require failure models able to predict fracture for high strain rate and for different kind of stresses. Thus the assessment of protective structures against severe accidental loads like impact and blast needs detailed investigation on their mechanical response under higher loading rates. The paper provides an overview of a recent works concerning direct tensile and compression behaviour using a modified Hopkinson bar on UHPFRCs used in protective structures. The data presented in this paper are part of a project called “Protection of In- frastructure Elements from the effects of IEDs and Blast Charges”. In the project were scheduled a series of near-contact charge tests on various concrete plates. The paper is focused on the behaviour of the UHPFRC material, used in these slabs, under high loading rate in tension and compression. These tests were performed at the DynaMat laboratory on UHPFRCs obtaining stress-rate up to 1300GPa/s for spec- imens having diameter and length of 20 mm. Within such experimental activities, variations of peak and post-peak strength as well as of dissipated energy investigated and analysed in function of the stress rate. Furthermore, in order to determine the influence of the matrix on dynamic mechanical behaviour of the UHPFRC, the dynamic characterization was repeated on the material without fibres.

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