| In recent years,prefabricated RC frame structure has been widely concerned and used in China.However,at present,prefabricated structure is still dominated by assembled integral structure,and the connection between prefabricated beam and column members has some problems in engineering application,such as single connection form,few connection types,less consideration of post earthquake damage repair,which has seriously restricted the application and development of prefabricated RC frame structure.To give full play to the advantages of prefabricated structure construction,improve the seismic performance of the structure and facilitate post earthquake damage repair,a prefabricated RC frame structure with replaceable energy dissipation connections is proposed.In this structure,replaceable energy dissipation devices are installed between precast beam and column members,and the detachable dry connection mode is adopted.When the structure encounters a certain degree of earthquake damage,the damage is controlled on the energy dissipation devices and can be replaced during post earthquake to achieve the goal of structural damage repair.The mechanical properties of replaceable energy dissipation devices and the seismic performance of the proposed repairable fabricated RC beam-column joints and frame structures are investigated by the combination of experimental research,numerical simulation and theoretical analysis.The main contents and conclusions of this paper are as follows:(1)A type of replaceable energy dissipation device was developed,and five specimens of energy dissipation devices were made for quasi-static loading test to study the effects of different constraints(including pure shear deformation loading and bending shear deformation loading)and geometric parameters on its failure mode and mechanical properties.At the same time,ABAQUS software was used to establish the numerical model of the device and verify its accuracy.On this basis,the influence law of various factors on the energy dissipation device was analyzed and its opening form was optimized,and the bearing capacity deformation relationship of the optimized energy dissipation device was deduced theoretically.The experimental research and numerical analysis results show that the energy dissipation device can provide high bearing capacity and initial stiffness under different constraints,and has excellent energy dissipation and deformation performance.It can be used to improve the mechanical properties of precast beam-column joints.In addition,the theoretical analysis results of bearing capacity-deformation of the energy dissipation device are in good agreement with the numerical simulation results,which shows that the calculation method can provide a theoretical basis for the geometric structure design of the energy dissipation device and the analysis of precast beam-column joints.(2)Two different connection forms of precast beam-column joints were proposed,and one cast-in-situ beam-column external joint(namely MC joint),three precast beam-column joints connected by connection form 1(namely P1 joint)and three fabricated beam column joints connected by connection form 2(namely P2 joint)were made for quasi-static loading tests to study their failure mode,bearing capacity,hysteretic behavior,energy dissipation performance and deformation capacity.The experimental results show that the maximum deformation,ductility and energy dissipation capacity of the two types of precast joints are significantly better than that of the cast-in-place joint.The damage of precast beam-column joints is mainly concentrated in the multi-slit device,and the precast beam and column members are basically intact,which can achieve the goal of joint damage control and rapid repair of structural damage after earthquake.(3)For the two types of fabricated beam-column joints,the mechanical relationship between bearing capacity and deformation in the whole range from elasticity to plasticity was deduced theoretically.On this basis,a simplified analysis model of fabricated beam-column joints was proposed,and the restoring force model of the connection zone was determined.At the same time,based on the relationship between bearing capacity and deformation theory method,the determination method of the parameters of each key point in the skeleton curve of the restoring capacity model was given.The analysis results show that the theoretical calculation results of bearing capacity-deformation in the connection zone of precast beam-column joints are in good agreement with the experimental measurement results,which shows that the theoretical calculation method can truly describe the mechanical behavior of the connection zone of precast beam-column joints.In addition,The numerical model of fabricated beam-column joints was established by using Seismo Struct software,and the calculated hysteretic curve results are highly consistent with the joint test results,which shows that the method of determining the parameters of the restoring capacity model of the connecting part according to the bearing capacity deformation theoretical analysis method of the connecting zone is reasonable and accurate.(4)The numerical analysis model of a three-story fabricated RC frame structure was established,and the failure mode,bearing capacity and deformation of the fabricated structure under quasi-static loading and seismic wave loading were studied.The working mechanism of multi-slit energy dissipation device under different seismic intensity was discussed.At the same time,the numerical model of three-dimensional fabricated frame structure was established to further study the seismic response of the structure,and compared with the simulation results of cast-in-situ frame structure.The analysis results show that the maximum bearing capacity of the fabricated structure is basically close to that of the cast-in-place structure,and has better deformation and ductility than the cast-in-place structure.The deformation of the fabricated structure in the early stage is mainly concentrated in the beam end connection,which is conducive to give full play to the mechanical properties of multi-slit energy dissipation devices.Before the plastic hinge failure at the column end of the structure occurs,the damage degree of beam and column components is relatively light,which can realize the purpose of controllable damage location and rapid repair after earthquake.In addition,the fabricated structure performs well under horizontal earthquake at all levels,and its overall seismic performance is basically close to that of cast-in-place structure.(5)According to the characteristics of failure mode and capacity curve of prefabricated RC frame structure,the energy balance equation of the structure was established,and the calculation method of energy correction coefficientγof seismic input energy was improved.The theoretical relationship amongγ-μ_s-α_s-R_s was obtained,and the theoretical calculation formulas of yield base shear,plastic base shear and maximum deformation of the structure under different seismic levels were deduced.Finally,the performance-based plastic design method of fabricated RC frame structure was established,and the effectiveness of the design method was verified by designing a 7-story fabricated RC frame structure.The analysis results show that the prefabricated RC frame structure with this design method can achieve the expected performance target and has good seismic performance. |
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