Dynamic behaviour of concrete: the structural effects on compressive strength increase

Many concrete structures may be submitted to high rate dynamic loadings (impacts, explosions, etc.). So, it is necessary to know the behaviour of this material in order to predict the response of the structure. Under dynamic loading an increase of apparent compressive strength is observed. This may be due to a rheological effect or to a structural effect. Dynamic compression tests are available using the split Hopkinson pressure bars. Forces and velocities are obtained on each face of the specimen. A simulation of these tests is carried out using two different models. The first, based on plasticity theory, is a non-associated model with a failure surface of the Ottosen type. This model is independent of the strain rate. The second model is an elasto-viscoplastic model with a damage law. It only takes into account the main features of the behaviour, the sliding phenomena, the damage and the softening. The comparison of experimental results and simulations leads us to consider the structural effect as an inertial confinement responsible for the apparent increase in strength. Copyright © 2000 John Wiley & Sons, Ltd.