Study On The Re-centering Behavior Of Unsymmetrical Hybrid Connections By Key Parameters Of Prestressed Steels

According to the seismic tests of the related structures,it is shown that the seismic performance of the assembled structure depends largely on the structure of the joints,and the joint is the key to determine the overall performance of the structure.Prestressed reinforced concrete structures shows that the feature of the residual deformation after the earthquake is relatively small.Therefore,it is generally believed that the properties of the joints have great advantages in terms of seismic performance.The asymmetrical hybrid joint proposed in this thesis is a new type of prefabricated concrete structure,which is composed of post-tensioned unbonded prestressed steels and prefabricated concrete structures,in which the energy dissipation bars are only arranged in the upper part of the beam section.Under the earthquake,the elastic-plastic deformation of the structure is mainly concentrated in the connection part of beams and columns,and through the rebound effect of the prestress bars,the structure has a certain ability of self-reset,so that the residual deformation of the structure becomes smaller and meets the requirement of repairing the structure after the earthquake.Aiming at the key parameters of the prestress bar,the reset performance of the asymmetrical hybrid joint of the assembled frame is deeply analyzed by using the finite element software Abaqus.First of all,due to the limited research conditions,there are no relevant test conditions and time,so there is not enough experimental data to support.Based on the experimental data of a group of samples from Southeast University in the reference literature,the model was established and analyzed by means of failure morphology,hysteresis curve,skeleton curve,and so on.The strain variation of steel bar verifies the accuracy and reliability of the modeling theory in this paper.Then,in order to study the reset performance of prestressed steels to asymmetrical hybrid assembled frame joints,on the basis of the above verification,Abaqus is still used to establish the joint model,and different effective prestressed values are set up according to the prestressed steels.The skeleton curve,hysteretic curve,energy dissipation capacity,stiffness degradation and reset performance of the joints under low cycle reciprocating load are analyzed by using the reinforcement ratio and the relative parameters of the eccentric position at the lower end of the beam.The results show that the greater the effective prestressed value and the reinforcement ratio,the better the reset performance of the joint,and that the prestressed steels should be placed at the center of the beam section as far as possible in order to ensure the good reset performance of the joint.If placed in an eccentric position,the distance should be between 1/6 and 1/4 at the center of the beam section.Furthermore,in order to better study the reset performance of the nodes,Abaqus is used to simulate the joint material replacement process of the beam-column interface,and the three-node model is repaired.The low-cycle reciprocating load of the nodes under various parameters is analyzed again.The skeletal curve,hysteresis curve,stiffness degradation and reset performance are compared with the previous simulation.The results show that as long as the simple repair is performed,the seismic performance after the node repair can reach the level of the original node,but if the stress ribs are configured with too many steel strands,the excessively high reinforcement ratio will reduce the self-resetting ability of the nodes to some extent.