Visco-elastic behavior of free hexagons applied to FRC

Before designing structures, the material parameters have to be known from experiments or "in situ" measurement. Some of these methods may be very expensive and some of them very unreliable. Moreover, the numerical analysis enables designers to simulate different situation in the structure. Therefore, very accurate experiments are prepared for fiber reinforced concrete. In this paper, time dependent behavior of fiber reinforced concrete is studied. It is well known that in concrete itself the visco-elasticity or visc-plasticity plays a very important role. In the case of fiber reinforced concrete, the influence of time is a little bit suppressed, but still is very important. Only the effects of visco-elastic appear in a different way than that in the case of plain concrete. As a numerical tool, one of the discrete element method (DEM) is used, namely the free hexagonal elements, which are often used for solution of granular materials. They substitute the methods for solving continuum problems. We utilize the principal idea of the balls (particle flow code, PFC), but cover the continuum by hexagonal elastic, or elastic-plastic elements. In our case, the time dependence is concentrated into connections of elements, rather then to elements itself. The connections simulate non-rigid phase (clay), which can change during the time, although no additional force is added. The element themselves me more representatives of stone (time independent phase). The results from three and four point tests show the ability of the method.