Author(s)

J. Heyman

Abstract

Slender structural elements often appear "lively" when scaffolded for repair: a masonry spire, for example, or a smaller tapering pinnacle, can be made to vibrate quite easily. This natural behaviour is examined by obtaining estimates of fundamental frequencies, using the Rayleigh-Ritz method. 1 Introduction The type of pinnacle to be considered is shown schematically in fig. 1. The shape will be taken to be that of a right cone, whose cross-section may in practice be square or octangular. A real pinnacle will have crockets or other surface decoration, but examination of the conical shape gives results which lead to more or less general conclusions. (A more complex profile is considered later, fig. 5.) Loading on the pinnacle will be taken to be lateral, whether due to horizontal wind forces or to inertia effects arising from vibration. Steady gravity loading from self-weight of the material will not enter the analy

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