Experimental Research And Analysis On Restoring Force Characteristics 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 seismic behavior and restoring force model of them are few at home and abroad presently.This paper focuses on restoring force characteristics 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 mechanical behaviors of SRHSHPC frame joints including crack development, failure patterns and deformation characteristic etc. are analyzed. According to seismic hysteresis curve and skeleton curve obtained by joint tests, restoring force characteristics of SRHSHPC frame joints including ductility, energy dissipation, strength and rigidity degradation are analyzed, and the influences of axial compression ratio and concrete strength on the seismic behaviors of frame joints are discussed. Based on the test results and numerical analysis, rigidity degradation rules and hysteretic rules are analyzed. Trilinear hysteretic model considering rigidity degradation is proposed for steel reinforced high strength and high performance concrete frame joints. Test results show that SRHSHPC frame joints possess good seismic behaviors, strong energy dissipation and ductility as steel improves structure ductility, and high strength and high performance concrete improves concrete brittleness. The proposed restoring force model tallies with the test curve, which can be a good reference for seismic design of SRC structures.The study results will be the basis of the elastic-plastic dynamic analysis, which provide theoretical foundation for establishing reasonable calculation theories and design methods of SRHSHPC frame joints to promote the development and application of the excellent seismic structures.