ExperimentS and analyses of seismic behavior of columnS with fiber-reinforced concrete in bottom region

In order to improve the seismic behavior of the reinforced concrete columns,6 reinforced concrete column specimens with fiber-reinforced concrete (FRC) in the bottom region were designed and tested under reversed cyclic lateral loading. The specimens’ shear span ratio was 3 and their amounts of stirrups were relatively few. The height of FRC region,the axial load ratio and the concrete compressive strength were varied. The cracking and damage process of the specimens were observed and the hysteretic behavior and energy dissipation capacity were studied. The results show that,compared with ordinary concrete columns,the column with FRC in bottom region and few stirrups failed in shear after flexural yielding,and they have better ductile characteristics and damage tolerance. The columns with FRC in the bottom region can be designed with a small amount of stirrups. In addition,a finite element model was established to analyze the behavior of the columns under quasi-static cyclic loading in a displacement control mode by the software named OpenSees,and then a parametric analysis was made. Research shows that the peak load of numerical simulation are slightly smaller than that of the test,and the hysteretic curves of numerical simulation are in good agreement with those of the experiments. The parametric analysis shows that the impact of the height of FRC region and the volumetric raito of confinement steel in bottom region on the lateral load-carrying capacity and the lateral displacement is small.