Experimental Research For Impaired Reinforced Concrete Frame Joint

The joint of reinforced concrete frame structure’s force condition is complex, bear the bending moment, shear force and axial force coming from the beams and columns, and play a part in transmission and distribution of internal forces and maintain the integrity of the frame structure. The joint is the weakest parts of the framework, in the earthquake, many structures lose the bearing capacity and even collapsed due to the destruction of the joint. When the design of joint is improper, the construction method is unreasonable or the fortification intensity of the area improved, it may cause the seismic behavior of the structure does not meet the specification requirements, such as the bearing capacity, ductility, stiffness of the structure,then we can reinforced it to improve the seismic behavior. In order to study the reinforcement performance of the joint, through Quasi-static load test of four cross-shaped reinforced concrete frame joint, analyze the seismic performance of the impaired joint after reinforced by carbon fiber. Through low cyclic loading test of four reinforced concrete frame joint, study the seismic behavior of reinforced concrete frame joint,and systematically analyze the corresponding structural behavior parameters.The content of the article includes:(1) provides an overview of the seismic performance and strengthening methods, and describes the advantages and disadvantages of each study and the achievements of the research;(2) for the mechanical characteristics of the joint, design the reinforcement program of four joints;(3) measure the hysteresis curve of the joint, and get the skeleton curves, ductility, energy dissipation capacity, strength degradation, stiffness degradation according to calculated the hysteresis curve;(4) analyze and compare these four groups of specimens, and get the appropriate conclusions..The main conclusions of the test are as follows:(1) the column yield load and yield displacement, maximum load and maximum displacement has improved to varying degrees, stiffness and ductility remain unchanged. However, the strength degradation and stiffness degradation has been improved, energy dissipation capacity is larger. The joint’s failure mode has been changed from unstrengthened column undermine to beam and the core area undermine after reinforced;(2) Axial compression ratio has a certain influence on the seismic behavior of the specimen before and after reinforcement, with the axial compression ratio increased, the yield load, maximum load, ultimate load has improved to varying degrees, while the yield displacement, maximum displacement and ultimate displacement are different degrees of decrease;(3) the yield load, maximum load, ultimate load of the specimen which is directly reinforced is higher than the reinforced specimen, while the former’s yield displacement, maximum displacement and the ultimate displacement is smaller than the latter; the strength degradation and stiffness degradation of the specimen which is directly reinforced is better than the reinforced specimen. The difference between the former’s ductility and the latter’s ductility is not significant, but the energy dissipation capacity of the former is stronger than the latter.