A Comparative Study on the Lateral-Torsional Buckling Capacity of Double Channel Beams with Self-Supporting Connective Constraints versus I-Shaped Beams with External Lateral Bracing

In steel structures, beams in Moment-Resisting Frames play an essential role due to their ductile nature as structural members. The capacity of conventional steel beams is determined by the lower of the plastic moment capacity and the lateral-torsional buckling capacity. In order to attain the plastic moment capacity of the beams, lateral-torsional bracing is applied to postpone lateral-torsional buckling, allowing the plastic moment of the section to control the behavior. However, in some structures, it is a challenge to appropriately place lateral-torsional bracing, leading to difficulties in the execution of certain beams. A practical solution to this challenge is to use double channel sections instead of I-sections, along with intermediate connectors between the channels to improve the section's buckling capacity.  In this study, several intermediate connectors were considered for joining double channel beams, and among them, the connector with the best performance was identified as the most suitable intermediate connector for joining double channels. Using ABAQUS software, this research modeled double channel beams and compared them with I-shaped beams. To apply different loading conditions, the concentrated moment applied at one end of the beam was considered as a multiple of the moment applied at the other end. Additionally, in this study, four different beam lengths—4, 6, 8, and 10 m—were used to examine the effect of beam length. The research results revealed that, among the various spacing lengths considered for the intermediate connectors in the double channel sections, the restraining length used for the single channel section beams was found to be appropriate. Moreover, the study confirmed that the intermediate connector used to join the channels performed effectively, leading to a flexural capacity in double channel beams comparable to that of equivalent I-shaped beams.