Concrete wall subjected to fragment impacts - Numerical analyses of perforation and scabbing

Abstract

Concrete subjected to fragment impact is mainly related to protective structures such as civil defence shelters where the main threat arise from explosions caused by military weapons. For analysing impacts on concrete, material models are used in numerical analyses to simulate the reality. Such a model is the RHT model which is used to describe the material behaviour of concrete in the software Autodyn. The model has been evaluated for constructions subjected to compression and the result were satisfying. However, the function of the model is not satisfying for constructions subjected to tensile stresses. Therefore there exists a need for deepening the knowledge about penetration and scabbing of concrete subjected to fragment impact, about the parameters involved, and how the impact should be modelled in a accurate way. The intentions are to give recommendations on how scabbing and perforation by fragment impact will be modelled in Autodyn. The numerical calculations, based on the RHT model, were verified by results of already performed full-scale tests. The model was calibrated from information gained from a parameter study of the most important parameters such as tensile strength, softening energies, strain rate and shear strength. It was found out that by a calibration of the parameters conduction strain rate and shear resistance, in the material model, a result was obtained that was in accordance with the full-scale tests at the backside of the specimen. On the front side the result was not that convincing but showed tendencies that with further evaluation of the material model it could reach satisfaction.