ABSTRACT
INTRODUCTION When it was introduced in September 1996, BS 6399: Part 1 [1] became the first British Standard which included a section on synchronised dance loading. It stated that any structures which might be subjected to this loading should be designed in one of two ways. Either by designing the structure to have natural frequencies above specific threshold values in which case the problem was avoided; or by ensuring that the structure was designed to be able to withstand this type of loading. The threshold values of natural frequency given in the standard are 8.4 Hz in the vertical direction and 4.0 Hz in the horizontal direction. Many large cantilever grandstands are being designed and built at present in the UK, but it is difficult for them to be both designed economically and to meet the frequency thresholds. Consequently, there has been considerable debate as to whether the frequencies given in BS6399 can be safely reduced in the specific case of cantilever grandstands, and whether the synchronised loading case in BS6399 was appropriate for sporting events as well as pop and rock concerts.
