Experiment Research On Seismic Behavior Of Joints With Specially Shaped Columns And 600MPa-grade Bars

The reinforced concrete(RC)frame structure with specially-shaped columns has been widely applied in China because of its good architectural functions.It is shown that the joints of beam-columns are weaker in this structure from many experiment results,which limits the building height and the application range of specially-shaped column structure.How to enhance the seismic behavior of the weak part like the beam-column joints,improve the building height and expand the application range is urgent.X-shaped reinforcement and 600MPa-grade bars have been used to reinforce the joints with specially shaped columns in this paper.Based on the comparison of the joints with X-shaped reinforcement and those without X-shaped reinforcement,the joints with 600MPa-grade bars and those with 500MPa-grade bars,the applicability of X-shaped reinforcement and 600MPa-grade bars in joints' weak position is studied.It is shown from the experiment research on seismic behavior of joints with specially shaped columns that the joints with 600MPa-grade bars have high bearing capacity,while ductility is worse compared with the joints with 500MPa-grade bars.Because of the setting of X-shaped reinforcement in the core region of joint,the damage characteristics,bearing capacity,ductility,energy dissipation capacity and aseismic behavior of the joints are improved significantly.The mechanical mechanism of the joints of specially shaped columns with X-shaped reinforcement is studied.The formula of shearing capacity of the joints of specially shaped columns with X-shaped reinforcement is proposed according to the analysis of shearing capacity.The formula has been verified to have a certain safety stock.The ANSYS models of the joints with specially shaped columns are established and analyzed,the simulation results are in good agreement with the experimental results.The mechanical properties of the joints instead of rectangle columns in the core region of joints are studied,it is shown from the results that the bearing capacity of the joints is increased,the stress of the concrete and the stirrup in the core region is reduced.It is shown from the results that the bearing capacity of the joint is increased with the increase of the stirrup ratio in the core region of the joint.