| Engineered cementitious composites(ECC)has over 3% ultimate strain under uniaxial tensile load,and has good ductility,deformation capacity and energy dissipation capacity.These advantages of ECC materials make it have a wide development prospect and application space in the seismic resistance of Bridges.At present,ECC is not widely used in the study of seismic behavior of Bridges,the simulation of ECC materials by general finite element software is not perfect,and the theoretical study of seismic behavior of ECC Bridges is not deep.Therefore,in this paper,the ECC uniaxial hysteretic constitutive model is improved in the finite element software OpenSees.On this basis,numerical simulation is used to carry out theoretical research on the seismic performance of ECC section and ECC pier,thus laying a foundation for the seismic design of ECC pier.The content and results of the study are as follows:(1)Development of constitutive model of ECC based on OpenSees platform.Based on the ECC uniaxial hysteretic constitutive relationship obtained by foreign scholars’ experimental studies,a more complete ECC uniaxial hysteretic constitutive model,namely ECC02,was successfully implemented in OpenSees after a reasonable simplification.The reliability and rationality of ECC02 constitutive model are demonstrated by comparing ECC02 constitutive model with existing ECC01 constitutive model.(2)Study the bending resistance and ductility of ECC pier section basing on the concept of ductile seismic design.The influences of axial compression ratio,reinforcement ratio and material strength on ECC section performance were analyzed.It is found that when the axial pressure ratio is less than 5% or reinforcement ratio is less than 2%,the improvement of the axial pressure ratio or the reinforcement ratio can improve the deformation capacity and ductility of ECC pier section.The influence of axial compression ratio,reinforcement ratio and material strength on the envelope curve of axial moment of ECC pier section is linear.(3)Pushover parametric analysis of ECC pier and comparison with RC pier.It is found that increasing axial compression ratio in a certain range is not conducive to the deformation capacity of ECC pier.Increasing slenderness ratio in a certain range is helpful to improve the deformation capacity of ECC pier,but reduces the lateral bearing capacity of ECC pier.The effect of longitudinal reinforcement ratio on bearing capacity and displacement ductility of ECC pier is monotonic.The comparison between ECC pier and RC pier shows that ECC pier has better lateral bearing capacity and ductility of displacement than RC pier.(4)The hysteresis performance of ECC pier was parameterized and compared with that of RC pier.It is found that increasing axial pressure can improve the bearing capacity of ECC pier,but reduce the hysteretic ductility.The effect of slenderness ratio on ECC pier is the most complicated.Increasing the reinforcement ratio is conducive to improving the energy dissipation,initial stiffness,bearing capacity and hysteresis ductility of ECC piers,and inhibiting the degradation of strength and stiffness of piers.The hysteresis performance of ECC pier is better than that of RC pier. |
