STUDY ON STATIC PROPERTIES AND INITIAL STIFFNESS FOR A NEW TYPE OF INNER SLEEVE CONNECTIONS BETWEEN SQUARE STEEL TUBE COLUMNS AND H-TYPE BEAMS

A new type of connections between square steel tube columns and H-type beams with inner sleeves was proposed. Moving the splice joints of columns above the panel zone provided spaces for installation of high-strength bolts, while ensured the continuity of panel zones. To analyze the mechanical properties of three improved connections by finite element simulation method, a connection structure of the connection was obtained, which was of outstanding mechanical properties. To study the static performances of the new type connections and the parameters influences, finite element models were constructed and the design parameters including the thickness and the length of the inner sleeves and the thickness of end-plates. The results showed that the new type connection had higher initial stiffness and bearing capacity. Plastic hinges appeared at the end of beam when the connection damaged, which met the seismic design principles that were "strong columns and weak beams" and "strong joints and weak members". The parameters including the thickness or the length of the inner sleeve, and the thickness of end-plate have some effects on joint static performances. Based on the results, design values were suggested. A calculating formula of initial stiffness for the new type connection was given by using components method, and the calculated results were in good agreement with the results simulated by the finite element method.