| Concrete beam to Special-shaped concrete-filled steel tubular column joints not only can well satisfy the bearing capacity of the structure and seismic requirements,but also can avoid the appearance of corner column in the room which makes room more beautiful and neat and improves usable floor area of the building,so it is used widely in practical engineering.Based on the low cyclic load test of concrete beam to T-shaped concrete-filled steel tube column connections with outer stiffening ring which have been completed by Dr Liu Jixiong,this paper emphasizes on the further study of the seismic behavior of concrete beam to T-shaped concrete-filled steel tubular column joint with outer stiffening ring and investigates the restoring force model of this connections through the finite element software ABAQUS.The main research contents and conclusions are as follows:(1)The seismic behavior of concrete beam to T-shaped concrete-filled steel tubular column joint with outer stiffening ring was analyzed through establishing its finite element model with software ABAQUS.The influence of seismic performance of each factor of outer stiffening ring connection was analyzed by changing arrangement of hoop reinforcement,length of corbel,reinforcement ratio of beam,axial compression ratio,stiffness ratio of beam-column and other factors.Studies have shown that setting up hoop reinforcement can obviously improve the ultimate bearing capacity and the initial stiffness of the connection and strengthen the deformation ability and seismic performance of the joint so as to make point destruction form changed from brittle fracture to ductile fracture.By arranging steel corbel in the concrete beam,stiffness of joint area is enhanced,which lead to plastic hinge caused by bending shear failure go outward and appear in the outside of corbel.This joint satisfies structural design principle of “strong column,weak beam,strong joint“.The reinforcement ratio influences the seismic performance and bearing capacity of the joint deepest in the eight factors.Reducing its reinforcement ratio causes bearing capacity and energy consumption coefficient of this joint decline dramatically.The column section stiffness is far greater than the stiffness of beam section of the joint,and the failure pattern of the joint is commonly concrete beam bending shear failure,and the ferrule effect of steel tube increases the limit compressive stress of core concrete,so the change of the axial compression ratio at 0.2-0.6 range have few effects on the seismic performance of the joint.The brittleness also increases with the increasing of concrete strength.Increasing concrete strength of the joint leads to bearing capacity increasing slightly and the ductility decreasing,so C35 can be used in practical engineering comprehensively considering economical factor.(2)By analyzing the skeleton curve and hysteretic curve of concrete beam to T-shaped concrete-filled steel tubular column connections with outer stiffening ring,adopting dimensional normalization and data fitting method,the tri-linear skeleton curve model and the stiffness degradation rule were established.Comparing this skeleton curve model to the skeleton curve of the finite element calculation,coincide degree of two skeleton curves is good.Combining the tri-linear skeleton curve model with the stiffness degradation rule and uninstall hysteresis criteria,the restoring force model is obtained. |
