Experimental Research On Seismic Behavior Of Interior Joints With X-Shaped Reinforcement

The reinforced concrete frame structure with specially-shaped columns combines the aesthetics and flexibility of the architect effectively.However,the further generalization of the structure height and application is limited due to the problem of the weak node code area.In this paper,the reinforced concrete frame structure with specially-shaped columns is researched,which is reinforced with high-strength steel bars and X-shaped reinforcement.The enhancement effect of the seismic performance of the joints is studied,which provides theoretical support for the application of high strength steel bars and concrete specially-shaped columns.The detailed work of this paper is stated as follows:In the paper,four interior joints with high-strength reinforcement are designed.The interior joints with or without X-shaped reinforcement are tested under low cycle loading.Comparison is made on damage character,bearing capacity,deformation performance,resilience characteristics(including hysteresis curve,skeleton curve,stiffness degradation,energy dissipation capacity),stirrup strain and X-shaped steel bars strain.And the influence of reinforcement strength grade and X-shaped reinforcement on seismic behavior of specimens has been analyzed comprehensively.It is shown that X-shaped reinforcement can be used to reduce the width of crack and improve failure mode.At the same time,the shear resistance and deformation performance is enhanced,the hysteresis performance is improved,the stiffness degradation is delayed,and the energy consumption is strengthened.Considering the seismic performance of the specimen,it makes the most significant difference to improve the seismic performance of the joints in the concrete frame with HRB500 high-strength reinforcement and the same strength X-shaped reinforcement in the core area.The stress state and force mechanism of concrete frame joints are analyzed on the basis of the experimental result.Comparing with the calculation formulas about shearing capacity of “Code for Design of Concrete Structures” GB 50010-2010 and “Technical Specification for Concrete Structures with Specially Shaped Columns” JGJ 149-2006,the formula of shear capacity of RC frame joints with high-strength reinforcement concrete is put forward.The result shows that the application of X-shaped reinforcement in the core area of the concrete specially-shaped columns can improve the shearing capacity,and the shearing capacity of the joints in the concrete specially-shaped columns frame has a certain safe reserve.