Study On Deformation Behavior And Equivalent Damping Of Confined Reinforced Concrete Columns

Confined concrete has been widely used in concrete columns, piers and pre-stressed piles. Stirrups provide lateral confinement to core concrete, which improves the strength and ductility of core concrete. Aiming at the stress-strain relationship of confined concrete and equivalent damping of columns of flexural failure, the following work has been done:(1) The previously proposed confined concrete constitutive models have been introduced. Stress-strain curves and load-deformation curves using different confined concrete models have been compared through calculation examples. The results show that there are scarce differences in the ascending branch of stress-strain curves, but remarkable discrepancies in the descending branch. The influence of different models on load-deformation relationship is relatively small in the pre-peak range, but large in the post-peak range, especially when under high axial load level. The strength and ductility of confined concrete increases with the increasing of stirrups diameter, and decreases with the increasing of stirrup spacing.(2) A new constitutive model is proposed based on experimental results of square RC columns of flexural failure from PEER database. Parameters in the new model are determined based on the error from experimental results from PEER database. The comparison of proposed model and existing models shows that the proposed model provides a more accurate prediction of confined concrete behavior.(3) A new hysteretic loop model of RC column is proposed based on experimental results from PEER database, and a equivalent damping ratio formula is derived corresponding to this hysteretic model. Compared to existing equivalent damping ratio models, the proposed model has better agreement with experimental values from PEER database. A Pushover analysis using proposed equivalent damping ratio model and existing models is made, respectively.