Experimental Investigation On Punching Shear Behaviors Of The Embedded Concrete-filled Steel Tubular Column Base With Shearing Ring

The concrete filled steel tubular (CFST) has been used in the high building structure. However, the column base joint design is an important part in the design of concrete-filled steel tubular structure. At present, column base joint has not been able to satisfy the high-rise concrete-filled steel tubular structure, moreover still had many problems in practical application of column base join,particularly punching shear failure mechanism, failure shape and bearing influence factors of the embedded concrete-filled steel tubular column base joint. In this paper, a new embedded concrete-filled steel tubular column base joint with shearing ring as the main object investigated is proposed. The punching shear experiment was carried to analyze punching shear failure shape, the failure mechanism as well as the bearing influence factor.In this paper, two specimens of the embedded concrete-filled steel tubular column base joint with shearing ring were designed. One specimen (NO ZJ/J-5) was fixed 3 eight-diameter bar shearing rings interspaced 65 millimeter, another specimen (NO ZJ/J-6) was fixed 2 six-diameter bar shearing rings interspaced 60 millimeter. Loading vertical axial pressure to these specimens to study failure shape, failure mechanics and influence factors. The result showed that the specimens set up shearing rings effectively improved the punching- shearing performance of those joints. Based on the proving trial, According to the test result of the failure shape and ultimate bearing load, it found that such joint damage appeared at the top shearing ring. The failure characteristic was similar to the punching-shearing of concrete isolated foundation. The more and the higher the size of shearing ring was, the more the punching-shearing circumference and area was, as increase of punching-shearing load. Stirrup had important influence on load in joint.The column base joint was analyzed by the nonlinear finite element method, The model of column base joint ZJ/J-6 was analyzed by the software ANSYS in this text. The calculated results inosculated with the test results. It indicated that the modeling and material parameters in numerical analysis were correct. On the basis of the analysis, the bearing mechanism and punching-shearing damage pattern at column base joint were further understood. The damage pattern obtained by finite element analysis was basically consistent with test.