Approximations in Alternate Load Path Capacity of Welded Unreinforced Flange-Bolted Web Connections

In the event of sudden column removal, beam-to-column connections play a significant role in transferring the load carried by the damaged parts to the intact ones. This role involves experiencing a magnified bending moment and axial load which ultimately produces catenary action in the beam. This mechanism can eventually replace the flexural action in carrying the gravitational loading. Therefore, the beam and the connection must be able to develop and maintain a sufficiently large axial tension which explains the important role that connections play in mitigating progressive collapse. However, the strength and ductility of the out-of-plane members and connections affect the total load carrying capacity of structures employing moment connections. In this study, using component-based modelling, the effect of modelling these structural elements in the final result is investigated. Analysis results of a generic structure revealed that ignoring the out-of-plane members and connection can lead to overestimate the load carrying capacity of the affected span by 72%.