Experimental Research And Analysis On The Residual Ultimate Strength And Stiffness Degradation Of Steel Reinforced High Strength And High Performance Concrete Frame Joints

The excellent seismic performance of steel reinforced concrete (SRC) structure and the fast development of high strength and high performance concrete (HSHPC) will promote the application of HSHPC to SRC structures in the future. For complicated mechanical property and construction of joints, and concrete brittleness caused by high strength, the theoretical studies of steel reinforced high strength and high performance concrete (SRHSHPC) frame joints lag engineering application, and the studies on damage and residual ultimate strength and stiffness degradation of joints are few at home and abroad presently.This paper focuses on residual ultimate strength and stiffness degradation of SRHSHPC frame joints. The tests of 5 "weak joints" SRHSHPC frame joint specimens under low cyclic reversed load are carried out. Compared with RC joints and SRC joints, the damage behaviors of SRHSHPC frame joints including crack development, failure patterns and deformation characteristics are analyzed. Based on the analysis of test results and datas, damage model is proposed for steel reinforced high strength and high performance concrete frame joints. In the end, the residual ultimate strength and stiffness degradation of the joints are analyzed, and the influences of axial compression ratio and concrete strength on the seismic behaviors of frame joints are discussed. Test results show that SRHSHPC frame joints have good seismic behaviors, strong energy dissipation and ductility as steel improves the residual ultimate strength and stiffness degradation, and high strength and high performance concrete improves mechanical performance. The proposed restoring damage model tallies with the test curve, which can be a good reference to seismic design of SRC structures.The research will offer theoretical foundation to further study on load-transformation mechanism and shear calculating theory of SRC frame joints, and may be helpful to seismic disaster prediction and evaluation of SRC structures...