An explicity damage model for dynamic concrete behaviour. Numerical simulations and comparisons with experimental results on reinforced concrete plates under blast loading

摘要

Under severe mechanical loading, brittle materials, like concrete, can be described favourably using damage models. In order to determine the vulnerability of reinforced concrete structures submitted to accidental loading, the Centre d'Etudes de Gramat has developed an explicit damage model. This new concrete model uses two internal scalar variables to represent the material stiffness with opened or closed Inelastic tensile and inelastic compressive strains are introduced. Strain rate effects are also taking into account in order to separately increase the dynamic tensile and compressive material strength. Friction stresses are added to simulate stress strain hysteresis during unloading and reloading path. The Hillerborg regularisation concept is applied to reduced mesh size effects on failure process. The explicit model allows computation of the stress tensor directly and exactly, without any iterative process. Computation time are reduced drastically and convergence difficulties of the iterative procedure are suppressed. The model has been implemented in an explicit finite element program. Numerical simulations has been done to simulate experimental results obtained on a reinforced concrete circular plates under shock wave loading. The concrete plates have a diameter of 1.3 meter and a thickness of 8 or 10 centimetres. The plates are supported on it external edge. Calibrated shock wave loading inducing static overpressure between 100 Kpa and 500 Kpa are applied successively to the reinforced concrete plates. Large and permanent deflections are obtained on the concrete structure. Strain gage measurements are recorded on the steel reinforcement. Comparisons between numerical and experimental results are presented and discussed.