17. Mesoscopic Modelling of Ultra-High Performance Fiber Reinforced Concrete Under Dynamic Loading

For the two last decades numerous research works have been developed on the mechanical behavior of UHPFRC (Ultra-High Performance Fiber Reinforced Concrete) under quasi-static and dynamic loadings. However fibers orientation remains a major problem as during the implementation of fibers in concrete structure a random distribution and orientation of fibers is difficult to achieve. In this study four UHPFRC have been tested in dynamic tension and numerically simulated. The first concrete is made without any fibers. A random orientation of fibers is considered in the second concrete. Fibers oriented parallel or orthogonally to the loading direction (tensile loading) are considered in the two last cases. The four sets of concrete have been subjected to dynamic tensile loading by means of spalling tests. Next, a mesoscopic numerical simulation has been developed by considering a biphasic model: the concrete matrix is modelled by applying the DFH (Denoual-Forquin-Hild) anisotropic damage model to 3D finite-elements. In addition two nodes-finite elements are introduced in the 3D mesh to simulate numerically the presence of fibers by considering three orientations: fibers randomly distributed, parallel or orthogonal to the loading direction. As observed in the experiments, a small influence of fibers is observed regarding the peak-stress whereas a strong influence of fibers orientation is noted regarding the post-peak tensile response of UHPFRC.