Finite element analysis of ultra high performance fiber reinforced concrete beams subjected to impact load

The behavior of ultra-high performance fiber reinforced concrete members is quite different from traditional concrete. However, due to the fact that there is no design code in our country and in many countries related to this concrete and its high cost, there are limited studies about the dynamic behavior of ultra high performance fiber reinforced concrete elements in the literature. The number of specimens in experimental studies to develop design procedures for large-scale structural members can be reduced by finite element programs. Verified numerical models can be used to study the effect of change geometry, the rate of reinforcement and loading conditions on structural behavior. In this study; ultra high performance fiber reinforced beams, which were subjected to dynamic and static loadings from the literature, were modeled by a finite element program and the simulation ability of the numerical models was examined. The analyzes were carried out using the concrete damage plasticity model for concrete and the classical metal plasticity model for reinforcement in ABAQUS finite element program. The parameters required to constitute the material model were obtained from the pressure and tensile tests. The results obtained from the numerical models show that the Concrete Damage Plasticity model can accurately represent the behavior of the ultra-high performance reinforced concrete beams under dynamic and static loadings. Additionally; a parametric study was performed by selecting one of the validated numerical models. In the parametric study; geometry, material properties and size were kept constant and displacement-time values were compared by examining the effect of the stirrup spacing, strength of longitudinal reinforcement and impact velocity on the dynamic behavior of the reinforced concrete beams made up of ultra high performance fiber reinforced concrete. It was observed that there was no significant effect of the change in the stirrup spacing on the behavior of the beams exposed to a one-time impact loading and there was a significant increase in both maximum and permanent displacements with the decrease in strength of longitudinal reinforcement. It has been determined that the most effective parameter for deformation of the member is the change of impact velocity. An apparent increases in the maximum and permanent displacements in the middle of the beam is observed along with increase in the speed.