Design And Research Of Precast Prestressed Concrete Assembled Monolithic Frame Structure In High Seismic Intensity Regions

In recent years,modernization of construction industry is becoming a hotspot.Precast assembled structure has received widespread concern by all social circles.Many scholars have carried on a large number of researches and related experiments about the precast assembled concrete frame joints.Based on the specification now available of China,seven precast prestressed concrete frame joints are designed for the seismic region of 8 degree intensity.The low cyclic reversed loading test of scale joint models is conducted to study the seismic performances of the joints designed.The new type of joints are designed based on the scope system,and some improvements are made.The lower groove wall of precast beam keyway is removed,thus the utilization efficiency of reinforcement strength can be increased.Then,the finite element analysis of the joints is carried out,and the experimental results are compared with the simulation results.Finally,the seismic performance of the frame is evaluated by adopting the performance-based analysis method.The main contents are as follows:(1)seven joints tests with the parameters of different ratio of the lower and upper beam rebars,changing stirrup spacing in the joint region and different strength grade of beam rebars are completed.The hysteretic curve,ductility,energy dissipation capacity and stiffness degradation are analyzed,and the seismic performance of the designed joints is evaluated quantitatively.(2)OpenSees program is adopted to simulate the joints under low cyclic reversed loading,and the simulation results are compared with the test.Besides,the parameter analysis of the joints is carried out.The results show that the loading process of the joints can be simulated properly using beamcolumnjoint element within OpenSees under low cyclic loading.The unloading and reloading stiffness degradation,strength degradation and rheostriction of hysteretic curve at later loading stage of the joints can be predicted accurately in each loading cycle.(3)Pushover analysis of a six-story frame structure that joints design is based on is conducted,and the frame structure is designed using PKPM program.The results are comparied and verified through elastoplastic time-history analysis and Ry-?-T method adopting the strength reduction factor,thus the seismic performance of the structure can be evaluated more comprehensively.The research shows that:The final failure mode of seven joints designed based on the existing specifications is that the plastic hinge appears at the end of the beam,while the the column and the core region of the joint are basically no damaged,which meet the requirements of the code for seismic design of building.Nonlinear finite element program OpenSees can well simulate the mechanical behaviors of beam-column joints under low cyclic reversed loading.Performance-based analysis results show that the frame structure designed can meet the code requirement of the maximum story drift ratio under rarely expected earthquake in the seismic region of 8 degree intensity.