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

The concrete-filled steel tubular column base joint is an important link in the concrete filled steel tubular structure design. But currently research about the concrete-filled steel tubular column base joint is relatively few. So, develop research on this base joint has practical significance for concrete-filled steel tubular structure's theory and application. This article studies the punching performance of the concrete-filled steel tubular column base joint which was buried in concrete foundation beam. Two embedded type column base joint models be designed, the models have no strengthen measures. Through the static load experiment to the models, this kind of column base joint's static work performance and the punching destruction shape be analyzed; in the experimental phenomenon and each material's stress in the process of loading be studied.Utilizing the nonlinear finite element analysis (FEM) ANSYS, column base joint was analyzed. Analysis shows that at the bottom of the ring board, concrete stress is big and near the steel pipe, stress cloud diagram indicated that the stress at stirrups is obvious,these stirrups have yield when the model destroyed.The FEM results concorded with the experiment results.Through contrast two types of joints, one type is the joint with no strengthen measure,the other type is joint with different strengthen measure. The impression of strengthen measures to punching shear strength be discussed.This study shows that: the concrete-filled steel tubular column base joint with no strengthen measure will be destroied as punching failure,the punching face appeared along the ring board down,punching angle greater than 45 o. In punching region, the stirrups'effect to punching shear strength is obvious. when the model destroyed, stirrups in punching region have yield.If strengthen measures were added to the steel tube, such as studs,shearing ring,external annular steel plate, the punching shear strength of the joints would be improved effectively.If the joint has enough strengthen measure, the punching shear strength of this embedded type column base joint will greater than its flexural strength and shear capacity, punching failure cannot happen.