Initial stiffness evaluation of reverse channel connections in tension and compression

Abstract

The so-called Reverse Channel connection has been conceived for the purpose of accommodating the thermal expansion of beams so that premature failure due to thermal buckling is avoided. The connection is made of a channel-shaped element, welded along the tips of its flanges onto the face of a hollow section column; an endplate welded on the beam is bolted onto the web of the channel. In a fire situation, the thermal expansion of a reverse-channel supported beam causes extensive bending deformation of the connection, therefore preventing the development of significant axial stress in the beam. Furthermore, this connection offers a high rotational capacity, if designed properly, which is beneficial in a fire situation where excessive deflections of beams can be expected.This paper aims to provide analytical stiffness assessment tools for reverse channel connections in compression and tension under uniform temperatures. The proposed analytical models are compared to results of Finite Element simulations, which in turn have been benchmarked with experiments. In addition, a comprehensive parametric study is conducted in order to identify all influencing factors on the initial stiffness response: reverse channel geometry and thickness, plate thickness, bolt position, and bolt diameter. Correction factors that account for 3D effects and bolt size are presented and discussed.The obtained expressions for the reverse channel stiffness are found to provide an accuracy that is acceptable for structural applications and can, therefore, be used as a design tool.