Internal eaves connections of double-bay cold-formed steel portal frames

Double-bay or multi-bay portal frames of hot-rolled steel have been in existence since the development of the plastic analysis theory, and the behaviour of the eaves connections of these frames are well established. With the increasing use of cold-formed steel in portal frames, it is necessary to develop connecting structural systems that are favourable to these elements, and to understand the behaviour of these connections. The purpose of this investigation is to develop internal eaves connections of double-bay portal frames of cold-formed steel channels, with the main frames members connected back-to-back. In double-bay portal frames, the columns of two single-bay portal frames, positioned adjacent to each other, are replaced by one internal column. Two internal eaves connections were developed and investigated, and are referred in this paper as Eaves Connection Type 1 (ECT-1) and Eaves Connection Type 2 (ECT-2). Tests were then performed to determine the capacity and failure mechanism of these connections, including the members forming these connections. Although the failure mechanisms included local buckling of the compression zone of the web and flange of the channels, and bolt-bearing deformations, all frames finally failed by local buckling of the web and flange of the channels. The moment-curvature graphs show that enough plasticity could not be achieved in both connections.