Steel Scaffolding systems are often constructed from cold-formed circular hollow sections. The beams of this system are normally called "ledgers" and the columns are normally called "standards". To allow the system to be quickly erected on site, "spigot joints" are inserted in the standards. The spigot joints consist of smaller diameter tubes which slide into the larger diameter tubes to provide a safe connection under gravity load. However, the spigot joints may have a lack of fit, and when located midway between the ledgers, they can cause significant out-of-straightness in a standard. This PΔ effect may weaken the standard as a column and lead to a reduced load capacity of the scaffold system. The paper describes tests on sub-assemblages of scaffolding with and without spigot joints. Concentric and eccentric loading eccentricity was also investigated. The results are compared with a nonlinear inelastic finite element frame analysis (program NIFA) developed at the University of Sydney. The nonlinear analysis included special modelling of the spigot joints. The results are also compared with design capacities computed using the Australian Steel Structures standard AS 4100-1998. Conclusions are given regarding the modelling of the spigot joints and the effect of the spigot joints on the strength of scaffolding systems.
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