EXPERIMENTAL BEHAVIOR OF CONNECTIONS TO CONCRETE-FILLED STEEL TUBES

Six large-scale connections were tested to failure using the quasi-sta tic test method. All details consisted of a connection-stub which was shop fabricated and field bolted for construction. Experimental result s indicated that welding the connection-stub directly to the skin of t he steel tube resulted in a large deformation demand on the tube wall. Large tube wall distortions made the girder flange, the flange weld, and the tube wall highly, susceptible to fracture. Inelastic cyclic be havior improved when external diaphragms were used to distribute the f lange forces around the tribe, and the connection was able to develop the bending strength of the girder. Using embedded elements to distrib ute the girder flange force to the concrete core was very efficient in alleviating the stress concentration on the tube wall, however; the c onnection performance was sensitive to the type of embedded elements. Deformed bars welded to the girder flange and embedded into the concre te core developed a connection strength of more than 1.5 times the pla stic bending strength of the connected girder, and exhibited stable hy steretic behavior up to failure. Connections with continuous flange pl ates showed less promise without additional derailing to anchor the fl ange plate into the concrete core. Extending the girder connection-stu b through the entire CFT column was sufficient to develop the full pla stic bending strength of the connected girder, and exhibited favorable inelastic cyclic performance. (C) 1998 Elsevier Science Ltd. All righ ts reserved.