Study On Seismic Deformation Behavior Of Circular Reinforced Concrete Columns

Experiment of sixteen circular reinforced concrete columns of different reinforcement parameters under low cyclic loading was conducted. The influence of shear span ratio, longitudinal reinforcement ratio, stirrup ratio(stirrup spacing) and axial load ratio on hysteretic curves, energy dissipation ability, strength degradation, skeleton curves and deformability of column were analyzed; the percentage and tendency of bending deformation, shear deformation and deformation due to the pullout of reinforcement were study; and the theoretical values of bending deformation and deformation due to the pullout of reinfo rcement are compared to experimental values; the load-deformation curves of sixteen columns were calculated using six different confined concrete constitutive models, and compared with experimental curves. The results show that:(1) All of the specimens failed in bending. Specimen of large shear span ratio has small horizontal capacity, and gentle ascending branch and descending branch of skeleton curve, which means a good ductility. Specimen with more longitudinal reinforcement has a large horizontal capacity. Specimen with small stirrup spacing has a plump hysteretic curve, high energy dissipation capacity and good ductility. Specimen under high axial load ratio has high horizontal capacity, low energy dissipation capacity, steep ascending branch and descending branch of skeleton curve, a significantly decreasing strength after peak-load, a small ultimate displacement and poor ductility.(2) Bending deformation, shear deformation and deformation due to the pullout of reinforcement increase with the increasing of total deformation. The percentage of bending deformation first decreases and then increases, while the deformation due to the pullout of reinforcement first increases and then decreases. The percentage of shear deformation is less than10%as the shear span ratio is relatively large. The percentage of deformation due to the pullout of reinforcement is larger in specimen with smaller shear span ratio and more longitudinal reinforcement. The theoretical values of bending deformation and deformation due to the pullout of reinforcement are basically tallies with experimental values.(3) There are little difference in load-deformation curves using the six confined concrete models respectively, and also little difference from load-deformation curves in experiment. Most of the difference are in the descending branch of the load-deformation curves. The prediction of load-deformation curves of column based on Mander-Priestley model and Fafitis-Shah model show satisfactory agreement with the experimental results.