Abstract: A three-column two-span plane frame structure is designed based on a concrete- filled steel tubular diaphragm through bolted joints. The entire process of collapse is simulated by static loading, and the mechanical deformation, resistance mechanism, failure phenomenon, and strain development of the joints are investigated. An ABAQUS finite element model is established to analyse the structural failure mode. Experimental and finite element results show that the collapse process can be divided into four stages: beam mechanism, mixed action, catenary action, and failure. The collapse resistance of the structure depends on both the bending and tensile capacities. The designed joints can meet the rotation requirements of FEMA-365, and the catenary action in the structure occurs prior to the failure stage. In addition, structure component failure occurs at the lower flange of the middle node H-beam, and the hole wall tearing causes the crack to extend to the web plate, which in turn generates a fracture in the H-beam. Because of the weakening of the flanges by bolt holes, it is suggested that the flanges of bolted H-section steel should be strengthened to ensure the effectiveness of the connection.

Key words: concrete-filled steel tube, Bolt connection, finite element analysis, progressive collapse