Stadia and structures which host crowd events often experience dynamic crowd loading. Of greatest concern is the loading from the actions of jumping and bobbing, especially if the action is regulated by an external stimulus. Gathered crowds of individuals will often synchronise their actions with one another exacerbating the jumping and bobbing load. Crowd and individual jumping and bobbing models are used to predict the dynamic forces experienced by a structure, however there is a lack of in-situ forces and experimental data from groups. To further the advancement of current crowd and individual models, this thesis provides an in depth study into the actions of jumping and bobbing. Experiments with eight test subjects (TS) and a range of activity frequencies were first conducted to study the loads generated by individuals. The properties of both actions were characterised and the variation within each TS’s ground reaction force (GRF) known as intrasubject variability, and inter-subject variability (between TSs) was quantified. Weight, gender and height affected the jumping GRFs. For jumping a significant portion of the properties were found to have the largest inter-subject variation at a frequency of 2Hz, suggesting high diversity of jumping properties between TSs. Overall there was more inter and intra-subject variation in the activity of bobbing than jumping. A novel indirect force measurement method was sought to aid the data collection of in-situ individual and group jumping and bobbing GRFs, by monitoring a single point on individual’s bodies. It was found that the best monitoring point was the C7th Vertebrae which provided reliable force data for the 1st and 2nd harmonics of jumping and bobbing. Having verified the single body point methodology for force measurement, group experiments with 2, 4 and 8 TSs were conducted. Metronome, music and visual stimuli were used to dictate the target frequency which ranged between 1.5 and 3.5Hz. A large database comprising of4,794 individual GRFs was collected. The degree of individual and group synchronisation with the beat and with one another was quantified for the first two harmonics. Group size, stimulus, and stimulus frequency were found to affect synchronisation. Charts detailing the expected levels of synchronisation were produced. The responses of simulated single degree of freedom (SDOF) systems to the group GRFs were examined and compared to responses from a periodic signal. For resonance responses there is potential for crowd loads to be modelled as a half-sine periodic force. Structural responses from forces measured on rigid surfaces were compared to responses from forces measured on flexible surfaces and found to be larger, especially at resonance. Charts are presented detailing the likely levels of structural resonance response for each stimulus and group size.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:682908 |
| Date | January 2015 |
| Creators | McDonald, Madison G. |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/77517/ |
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