Modelling of hollow structural section trusses

Abstract

It has been recently advocated that a practical static design of hollow structural section (HSS) Warren and Pratt trusses, having either gapped or overlapped connections, can be performed on the basis of a force distribution obtained from an elastic analysis of the truss with either all the members pin-jointed or the web members pin-jointed to continuous chord members. However, at the service load level, gap-connected truss deflections have been previously underestimated by around 12%–15%. Laboratory testing of HSS trusses has accordingly been undertaken to establish experimental axial force and bending moment distributions and truss deflection patterns. Tests have been conducted on two large-scale, 12.0 and 12.2 m span, simply supported, HSS Warren trusses, comprised of 60° gap or overlap K-connections. Based upon the experimental behaviour of the two trusses and the theoretical analyses, it is shown that simple pin-jointed analysis is sufficient to give good predictions for web and chord member forces. In the case of truss deflections, the contribution of connection flexibility on truss deflection has been taken into account using a simple virtual work method, and excellent agreement is then obtained between the predicted and actual truss deflections. Key words: steel structures, hollow structural sections, trusses, connections, deflections.