Comparison Between The Effects of a Moving Crowd on Different Grandstands During Similar Events

In recent years a growing number of large civil structures have been monitored in order to check their structural integrity and vibration serviceability performance. Among them, stadia have attracted considerable interest. A large amount of vibration data is available from different events (football matches, concerts, etc.) held at different places. Structural response is easily measured and occupied modal properties can be determined through operational modal analysis techniques, while estimating the excitation due to the moving crowd is a harder task. In order to provide more insight into these phenomena, the responses of two very different structures to nominally the same event are compared in this paper. The occasion in question is the world tour of the Red Hot Chili Peppers that took place in the summer of 2004, for which measurements exist both from the G Meazza Stadium in Milano and from the City of Manchester Stadium. The former structure is a huge concrete one capable of hosting 70000 people during concerts, partly built in the 50's and partly in the 90's; the latter is a state-of-the-art in-situ and precast reinforced concrete structure built initially for the commonwealth games in 2000. A direct comparison of the structural response during similar situations, e.g. comparing the same song for the two structures, will give some further ideas on the mechanism of crowd induced excitation. The effects exhibited by both structures can be attributed to people movements, while structural vibration components will be different in the two sites.