Numerical Analysis Of Plastic Hinge Lengths Of Reinforced Concrete Columns Under Different Seismic Failure Modes

The seismic failure mode and plastic hinge length of reinforced concrete column were firstly summarized and analyzed.Then based on ABAQUS software,the influencing factors of seismic failure mode and plastic hinge length of RC column were analyzed.Finally,the calculation formula of plastic hinge length was proposed.Based on existing test data,the failure mode and plastic hinge length of RC column under low-cycle repeated lateral force were simulated.The concrete damaged plasticity material model and stiffness degradation hysteretic constitutive for bilinear reloading of longitudinal reinforcement were adopted in model.Different failure modes were distinguished from three aspects of failure forms,hysteretic curves and mechanism,including flexural failure,flexural-shear failure and shear failure.The plastic hinge region of the simulated column was defined successfully by longitudinal reinforcement yield zone or the method of concrete crushing zone.Then 25 RC columns were designed.The parameters included stirrup ratio,section aspect ratio,axial compression ratio,shear span ratio,concrete strength and longitudinal reinforcement ratio.The column was analyzed under axial force and low cycle recurring lateral force.It was founded that with increasing axial pressure ratio and stirrup ratio,the columns changed from flexural failure to flexural shear failure.And with increasing stirrup ratio,section aspect ratio and shear span ratio,the columns changed from flexural failure to flexural shear failure.When the column-shear span ratio was greater than 3,the plastic hinge length had no obvious relationship with the seismic failure mode.By using simulated specimens,the boundary between flexural failure and flexural shear failure was given.Through comparative analysis,it was founded that the existing calculation formula of plastic hinge length of column didn't distinguish different seismic failure modes,and the existing formula of plastic hinge length wasn't applicable to the flexural shear failure column.In this paper,by collecting the test data of column plastic hinge length and combining the data of simulated specimen,the calculation formulas of plastic hinge length of RC column under flexural failure mode and flexural shear failure modes were obtained respectively.