Experimental Study on Innovative Π-Shaped Beam-to-Column Connections under Cyclic Loading

Abstract

An innovative type of bolted beam-to-column connection by means of a Π-shaped connector welded by two flanges, one web and one end-plate is put forward in this study. Besides standard bolt holes, short-slotted bolt holes are considered in the flanges and web of the connector for the Π-shaped bolted connections. An experimental investigation of six Π-shaped bolted connections with the parameters of slotted bolt-hole sizes and treatment methods of the faying surfaces between the Π-shaped connector and the beam and two comparative connections under cyclic load was undertaken to provide insight into the cyclic behavior of this joint type. The results demonstrate that the presented Π-shaped connections are characteristic of large plastic rotation, good ductility, and high energy dissipation, meeting the seismic design provisions for stiffness, resistance, rotation, and ductility. A slightly slotted size of the bolt holes in the connectors can greatly improve the seismic performance of connections in terms of the rotation capacity, ductility, and energy dissipation, and consequently prevent or reduce the risk of local damage progression in the beam flanges and web through the small movement allowed for the beam end. This can increase the postearthquake reparability of steel structures with such connections. Treatment methods of the surfaces just affect the slip resistance, the corresponding displacement, and therefore the ductility of connections. Observations of test connection specimens show that the Π-shaped bolted connections have multiple failure modes and can be viewed as a combination of end-plate and T-stub connections. Based on this, a reliable and conservative formula for prediction of rotation capacity of this joint type is proposed.