Experimental and theoretical investigations of spigot connections under cyclic loading

Abstract

Cyclic load tests were conducted on the spigot connections for a system scaffold. Two different connections were tested, one where both ends of a spigot were bolted to tubes and the other where one end was bolted and the other end welded. The tests were conducted by applying a series of different fixed axial loads together with a variable side load which was increased until failure occurred. The objective of undertaking cyclic tests was to not only obtain the rotational stiffness of the connection but also the looseness in the connection as looseness has been shown to reduce the performance of frames, and previous research and experiments involving spigots have ignored these effects. The tests and accompanying finite element calculations showed that the looseness was 0.009 radians for the double bolted spigot and 0.005 radians for the welded connection. The connections proved to be relatively unstable at high axial loads showing considerable scatter in the results. The results were in agreement with the stiffness results obtained by André that for a range of axial loads a single rotational stiffness could be applied but that for low and high axial loads different stiffnesses must be used.