Seismic behavior of bidirectional bolted connections for CFT columns and H-beams

Concrete-filled tubes (CFTs) have the advantages of both steel tubes and concrete. For that the confinement of the steel tube on the concrete would enhance the stiffness, strength and ductility of the concrete; also, the filled concrete can decrease the possibility of inward buckling of the steel. In this paper, bidirectional bolted beam-to-column connections for CFTs are proposed. A mechanical model is established to derive theoretical equations for calculating the stiffness, the yielding shear strength and ultimate shear strength of the panel zone. Also, a series of cyclic loading experiments has been conducted to verify it. The experimental results demonstrate that the bidirectional bolted connections have superior earthquake resistance in stiffness, strength, ductility and energy dissipation mechanism. These results indicate that the seismic resistance exceeds those specified in the seismic design codes of Taiwan and the US. Therefore, the bidirectional bolted beam-to-column connection has excellent seismic resistance, and this structural system can perform well as expected and be put into practice.