CFT Connections

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A wide range of beam-to-CFT column connections have been studied over the past several decades. Some type of connections transfer the load from the girders directly to the steel tube, while others transfer the load to both the concrete core and the steel tube. The connection types having girders welded to the steel tube are often suitable for simple connections (Dunberry, LeBlanc, and Redwood 1987; Shakir-Khalil and Mahmoud, 1995). However, for moment connections, these configurations impose high deformation demands on the steel tube, possibly causing fracture of the tube wall. This results in a deterioration of strength and stiffness. Thus, in some connection systems, it is common to distribute the girder force around the steel tube by means of internal and external diaphragm plates welded to the steel tube. For connections to circular CFTs, Schneider and Alostaz (1998) found that the connection types having extended plates or deformed bars passing into the concrete core improved both strength and stiffness. Among their specimens, the one with a continuous girder into the CFT column produced the most desirable cyclic response. For connections to rectangular CFTs, Ricles, Peng, and Lu (2004) found that using split-tee connections with through-bolts or post-tensioned bolts provided excellent hysteretic performance.