Finite Element Analysis On Mechanical Behavior Of Concrete Structure With Specially Shaped Column Joints By X-shaped Reinforcement

Reinforced concrete frame structure with specially shaped columns is widely used in residential construction because of its excellent architectural function and reasonable structural layout. Specially shaped column joint is weaker than rectangular column joint for the special shape of column section. It is more easily damaged under the earthquake action due to complexity of stress. So the height of frame structure with specially shaped columns is limited. Thus it is necessary to research the method of strengthening specially shaped column joint. In this essay, X-shaped reinforcement is used in joint core area to improve the seismic behavior of structure with specially shaped column joint. The finite element analysis is carried on about mechanical behavior of structure with T-shaped column joint,+-shaped column joint and Z-shaped column joint. The research work is as follows:Finite element models of structure with T-shaped colunm joint are established based on the experiment about concrete structure with T-shaped columns joints by X-shaped reinforcement.These models are used to analyze the mechanical behavior of the joints. Reversed load is applied on these models. The skeleton curve, bearing capacity and ductility of model are compared with the results of experiment to demonstrate the reliability of the model. The influence of X-shaped reinforcement on bearing capacity, ductility, steel stress and concrete stress is analyzed by changing the diameter of X-shaped reinforcement and beam bar. The results show that the yield load and the peak load of the model can be improved by adding X-shaped reinforcement in joint core area. The yield displacement is reduced because of the X-shaped reinforcement.Finite element models of structure with +-shaped column joint are established based on the experimental joints by X-shaped reinforcement.In order to demonstrate the reliability of the model, the skeleton curve, bearing capacity and ductility of model are compared with the results of experiment. The mechanical behavior of the joints are analyzed by changing the diameter of X-shaped reinforcement and beam bar.The results show that the ductility of structure with +-shaped column joint is quite well. The yield load and the peak load of the model are improved because of the existence of X-shaped reinforcement. But the yield displacement is reduced.Finite element models of structure with Z-shaped column joint are established according to the experiment about concrete structure with Z-shaped columns joints. The bearing capacity of model are compared with the results of experiment to demonstrate the reliability of the model. Two pairs of X- reinforcement are set in both sides of the web to analyze the difference of stress performance in Z-shaped column joint which is caused by X-reinforcement. The influence of X-shaped reinforcement on mechanical behavior is analyzed by changing the diameter of X-shaped reinforcement and beam bar. The results show that shear capacity can be improved by adding the X-shaped reinforcement in joints,but the influence is not significant. X-shaped reinforcement shares the shear force which was originally carried by concrete and stirrup.