ANALYSIS ON MECHANICAL PROPERTIES OF THROUGH DIAPHRAGM BOLTED-WELDED JOINTS BETWEEN CFST COLUMN AND STEEL BEAM

Proposes two types of through diaphragm bolted-welded joints (TDBWJs) between narrow concrete-filled steel tube (CFST) column to steel beam. The bolted connection is used in bottom flange and web of the beam, and the welded connection is adopted in the upper flange of the beam. The joints can not only effectively avoid the appearance of exposed corners indoor, but also solve the problems of reserved installation gaps and smaller joint stiffness of full bolted joints. The joints also facilitate assembly and concrete pouring. The structural details, assembly process, design principle of joints were presented. In order to investigate the loading process, failure mode, stiffness and ductility of the joints, monotonic loading tests were carried on the joints, and the finite analysis was conducted based on the tests. The results show good agreement between the tests and finite element analysis. The main failure modes of the joints are the buckling of the flange in compression and the bulge of the adjacent web, with the plastic hinges of the joints far away from the panel zone, which conforms to the design principle of strong joint and weak member. The joints can be classified as rigid connections, which have large stiffness and bearing capacity, as well as preferable ductility.