Research On Seismic Performance Of PEC Column-steel Beam Composite Frame With Friction Damped Self-centering Connection

To improve the brittle failure of conventional welded connections under the action of an earthquake,Self-Centering Moment Resisting Frames have been studied analytically and experimentally by domestic and foreign experts in the last twenty years.The results showed that the SC-MRF is capable of returning to its original position and eliminating residual deformations.This paper presents a revised moment-rotation relationship of friction damped post-tensioned self-centering connection to meet the different seismic performance design objectives of modern building structures and enrich the research contents of the self-centering systems.Combined with the related results of the research group,a 1/2 scale two-story speciment of self-centering composite frame with PT bars and friction damped self-centering connection was designed and fabricated with experimental test and numerical simulation.The optimal coordination mode of the self-centering capability and energy dissipation capacity is obtained by analyzing the influence of different parameters on the residual deformation,energy dissipation capacity and stiffness degradation of the composite frame,which provides a theoretical foundation for the application of the friction damped post-tensioned self-centering composite frame.The results demonstrated that the the bearing capacity and lateral stiffness of PEC column meet the requirements of the self-centering frame for the vertical members.Although the post-tensioned bars along the whole length of the beam reduces the effective prestress at the end of the beam,the residual deformation of all specimens are limited to the maximum story drift(1/200)of the frequemt earthquake at the end of duration of ground motion,showing adequate deformation capacity and self-centering capability.The energy dissipation of the specimens is mainly provided by the friction of the plates and the yielding of the beams.Before the contact between the bolt and the hole of the friction plate,the energy dissipation of the specimen is mainly contributed by the sliding friction between the plates.After the bolt contact the wall of the elliptical hole,the energy dissipation of the specimen is mainly provided by the yielding of the beam sections arond the friction plate.The diamater of the elliptical hole can flexibly control the capacity of energy dissipation of friction slip and the force-tansferring mechanism of the joint,which is the key to meet the different seismic performance design requirements of structure.High-strength bolts arranged on the interior and exterior flange of the friction plate guarantees the utilization of the mechanical performance of the beam,therefore,the structure has adequateself-centering capability and energy dissipation capacity.Although the vertical force on the top of the column exerts additional moment on the joint area and composite column,it has little effect on the self-centering mechanism and bearing capacity of the frame.Friction damped posttensioned self-centering composite frame can flexibly choose different diamater of the elliptical hole on the basis of seismic performance design objectives to control the moment of different force-tansferring mechanism of the joint.As a result of that the composite frame can be used again after the earthquake by replacing the friction plate,which has a great prospect of engineering application.