ANALYTICAL BEHAVIOR OF CONNECTIONS TO CONCRETE-FILLED STEEL TUBES

This paper presents a non-linear 3-D finite element study on a variety of details for connections to concrete-filled steel tubes. An analyti cal study was needed to verify connections that might be suitable for seismic conditions. This research focused on the connection to circula r steel tubes, because this shape presents more detailing difficulties compared to the square tube counterpart. Analytical models were gener ated using eight-node shell elements for the structural steel componen ts, and 20-node 3-D brick elements far the concrete core. Each element had the capacity for material inelastic and geometric non-linear beha vior. To verify the accuracy of the analytical models, results were co mpared to available test data. Parameters used in this analytical stud y included: the diameter-to-tube wall thickness ratio, the applied axi al load on the column, and the moment-to-shear ratio of the girder. An alytical results suggest that connections which transfer load from the girder to the concrete core potentially offer better seismic performa nce than connections to the steel tube alone. Connections to the steel tube only exhibit large distortion of the tube wall around the connec tion region. Components that transfer girder forces into the concrete core exhibit better strength and stiffness characteristics than a simp le connection to the tube face. However, the improvement in behavior d epends on the type components penetrating the concrete core. Connectio ns in which the girder extends through the composite column offers the most effective method in developing the ideal rigid girder connection behavior. (C) 1997 Elsevier Science Ltd.