Moment connections between rectangular hollow sections

Abstract Research and development activity on manufactured tubes or ‘Hollow Structural Sections’ (HSS), has been remarkably well co-ordinated during the period from 1970 to 1992, but emphasis has been on axially loaded connections. Most of this research has been directed at connections under predominantly static loading but lately there has been increased attention given to fatigue loading. This co-ordination has been achieved principally by an international organization of HSS producers called CIDECT (International Committee for the Development and Study of Tubular Construction). This has resulted in a very favourable share of the structural steel market for this product. CIDECT and the International Institute of Welding (IIW) have collaborated closely over the last decade to produce several sets of HSS connection design recommendations, which have now achieved wide acceptance (for example, IIW Fatigue Design Recommendations (1985) and IIW Static Design Recommendations (1981, 1989)). The static design recommendations covered axially-loaded K, N, T, Y and X connections, and were based on a large number of laboratory tests and observed failure modes. Although work has evolved on moment-loaded connections it has not, until very recently, been summarized in a rational manner like axially-loaded HSS connections. This paper therefore aims to synthesize the design procedures for Rectangular Hollow Section (RHS) connections under moment loading, using for the design basis a set of failure modes which are consistent with those identified for axially-loaded connections. By proceeding in this manner, a unified design approach will be achieved for all RHS connections under ‘predominantly static loading’.