Shaking Table Tests Studying About Self-centering Prestressed Concrete Frames With WEB Friction Devices

In recent years,the functional recoverable structural system has gradually attracted attention and recognition.The core idea of the proposed system is concentrating the structural plastic damage under earthquakes on the replaceable components and reducing structural residual deformation,so as to achieve the aims that use-function recovery rapidly and reduction of repair workload after earthquakes.In view of this situation,a novel self-centering prestressed concrete(SCPC)frame with web friction devices is proposed,which could re-centering to its original position and have non-plastic damage to members after earthquake,.Precast beams and columns are assembled together by post-tensioned(PT)tendons to create the lateral load resisting and gravity support systems.Web friction devices are used at beam ends and dissipate earthquake energy when the beam rotates to the column.Regarding this novel structure,model design,shaking table tests and numerical simulation about two kinds of SCPC frame have been studied in this dissertation.The main work of this dissertation is summarized as follows:(1)The shaking table specimen design of SC frame.A set of scaling factors of the experimental model is adopted through the study of the similarity ratio system of shaker model and experimental conditions.Based on the scaling factors and performance-based design method,two kinds of SC frame are designed(one is SCPC frame,which has PT tendons through beams and columns;the other is SCRB frame,which only has PT tendons through beams).The initial prestress of the PT tendons,initial friction of energy dissipation devices and additional mass are also provided.According to structural natural frequency and site soil information,and considering the specification of structural responses under earthquakes and the conditions of shaking table,two natural motions and one artificial motion are selected.(2)The shaking table tests study of SC frame.To study the seismic resistant performance under earthquake,different test matrixes are designed for the two frames.Several mations had been investigated during the experiment,as following: the structure dynamic characteristics,mode shape and initial stiffness,accelerate and displacement response,the relative rotation of joints,relative sliding between slab and beam,strain response of steel jacket and reinforcement and concrete.The influence of initial PT prestress and friction force on the global and local response for the SCPC frame also have been studied.(3)Owing to the fundamental differences between two frames is connection method at column-base joints,so the influence of the column-base connection method on the self-centering frame were studied particularly through comparative analysis the results of the two frames.Follwing the experimental results: desirable self-centering capacity and low level plastic damage of the members of the SC frame are demonstrated,and the self-centering prestressed concrete frame showed good seismic performance which could meet the engineering requirements effectively.It is worth noting that,furthermore,the displacement demand of SCRB is approved lower than SCPC's,but the column-base joints of SCRB have plastic damage,which increase the difficulty of repair after earthquake.(4)The numerical simulation study of the SC frame.Based on the early theoretical and experimental study,numerical models of the two SC frames are carried out by using the Open system for Earthquake Engineering Simulation(OpenSees).The simulation involvings joints contact,shear deformation of joint core area and energy dissipation devices.Good agreement is obtained between the numerical and test results,which proved the reliability of the numerical simulation method.However,the further noting is worth to be instructed that the initial shortcomings of structure should further be studied in the numerical simulation in future work.