| With the vigorous development of rail transportation,there has begun the planning of rail transit line 1 and line 2 in Hohhot area.The Xinhua Square Station and Daxue West Street Station and Zhongshan Road station are built by Top-down method.The design of beam-column joints is a difficulty problem which need to be studied in detail.In the process of Covered top-down method,the structure is not completed in the same time.The joint of the CFST column and RC beam is very important.In the design of joints,in order to meet the needs of shear resistance,we designed a new type of joint which has two Annular corbel,this paper compare the new type of joint with the traditional joint,and designed 3 groups of reduced scale experiment to study the shear bearing capacity and load transfer mechanism and damage form of this type of joint.Compared with the numerical simulation,we study the influence of key parameter,in order to provide advice for the design and application of engineer.The results are as follows:(1)According to the results of loading in laboratory and finite element simulation,the shear capacity of this joints with double Annular corbel(1 bright + 1 dark)is greater than that of single Annular corbel joints,with beam being constant.The ultimate load of the joints increased about 15% and the yield load of annular corbel increased about 40% by setting 1 bright Annular corbel under the beam,the use of double Annular corbel can effectively improve the bearing capacity of the joints in the same parameter of beam.(2)The ultimate load of the joints increased about 10% and the yield load increased about 36% by using double Annular corbel(2 dark)joint,with beam being constant.The shear force is mainly beard by Annular corbel in the lower height,the shear force beard by lower Annular corbel is about 2.4 times larger than upper Annular corbel.(3)The failure process of joints shows that the cracks at the bottom edge of the beam extend along the Annular corbel to form through cracks,and linked the main cracks in the core area of the joints then form shear failure.The failure modes of the joints are shear failure in the core region of the joints,the Annular corbels are not failure.(4)When the shear force become very large,the upper face of beam in the core area of the joint expand and the lower face of beam condense,extruding the steel tube,and forming large local compressive stresses and friction,which transfer shear force.(5)To study and compare the effects of beam width,beam height,reinforcement ratio,concrete strength,steel tube thickness,number of stiffeners and number of brackets on the shear capacity of joints,using ABAQUS to establish Numerical simulation of the same parameters and reach following conclusions: The promotion of shear capacity is not obvious by increasing reinforcement ratio and width of beam and concrete strength.Increasing the height of the beam can greatly improve the shear bearing capacity of the joints.Increasing thickness of steel tube and web number and Annular corbel can greatly improve the shear bearing capacity of the joints. |
