Passing-through I-beam-to-CHS column joints made by laser cutting technology: Experimental tests and design model

Abstract

Connections of I-beam to CHS column in buildings are either simple (fin plate connection, directly welded beam connections) and flexible or rather complex and rigid (external diaphragm connections). The passing-through I-beam-to-CHS column connections made by laser cutting technology offer a solution that limit the amount of welding and enhance the stiffness of the joint. An experimental campaign has been carried out to investigate the behaviour of this type of moment resisting connections under monotonic equal bending moment produced by gravity loadings. These experimental tests demonstrate that the uninterrupted continuity of the I-beam produces rigid-full strength connections. In addition, the same configuration has been tested under opposite bending moments applied either monotonically or in a cyclic manner to characterize the connection behaviour under seismic loading. The failure modes are quite different compared to those observed under equal bending moment and involve substantial force redistributions between the different joint components after cracks propagation has occurred. These tests highlighted the impact of the tube-wall thickness and the welding technique on the connection response. An analytical model is proposed to evaluate the bending resistance and the initial rotational stiffness considering the interaction between the tube and the segment of the beam section inside the tube. This beam is assumed to rest on two supports and restrained at the support by the tube. The design model predictions are in good agreement with experimental tests and numerical simulations.