Experimental And Numrerical Study On Dynamic Behaviorof Reinforeed Concrete Columns

Concrete material has been the most widely used construction material instructural engineering. The dynamic behavior of concrete materials and reinforcedconcrete (RC) structures under dynamic loads including earthquake and strong windhas been a challenging problem. It had been widely recognized that strain rate hassignificant effect on material properties of concrete under dynamic loads. While, incurrent aseismic design code of China, the effect of strain rate on materials strengthand structural performance are not considered properly. In order to further study, thebehavior of RC structures under dynamic loadings, experimental and numericalstudies on RC columns under cyclic and monotonic loadings with different rates arecarried out in this study. Moreover, an embedded PZT-based functional element isemployed to monitor the damage condition of the specimens.The main content of this study can be summarized as follows:(1) Experiments of twelve RC columns under constant axially compressive loadand lateral cyclic and monotonic loads with different load rates are carried out in thispaper. The results show that the load-carrying capacity and energy dissipationcapacity increased significantly with the increase of loading rate, but the load andstiffness degradation rates accelerated. The increase of reinforcement ratio ofspecimens under dynamic loadings could delay the speed of load degradation, andenhance the energy dissipation capacity, while accelerate the stiffness degradationspeed. Axial compression ratio is an important factor in the impact of structuralductility. Test results show load degradation rate, stiffness degradation rate increasewith the increase of axial compression ratio，while energy dissipation capacitydecreases with the increase of axial compression ratio. The load-carrying capacityunder monotonic dynamic loading pattern is higher than that under cyclic dynamicloading mode.(2) In order to investigate the effect of the randomness of concrete material onthe dynamic behaviorof the columns, test identical specimens under same dynamicloading condition are repeated. Although differences of load-carrying capacity can bedetected, the overall results are similar.(3) In the numerical simulation study, two concrete dynamic constitutive modelsare employed and fiber element model are used to simulate the dynamic behavior of the RC columns with different reinforcement ratios under different loading rates, anddifferent axial compression ratios. At the same time, by the introduction of dynamiceffects in the plastic damage model, the behavior of the specimens under dymanicloads is simulated with ABAQUS. Simulation and experimental results are in goodagreement.(4) Utilizing an innovative embedded PZT-based functional element, damagecondition status of one RC column under dynamic loading experiment is monitored bythe frequency response function analysis on the measurement of PZT under impact.Results show that the embedded PZT-based functional element can monitor thedamage condition at different deformation level. Moreover, feasibility study in thedynamic stress measurement using the functional element has been carried out.