Human induced dynamic loads estimation based on body motion

Crowd motion on civil structures that host musical and sport events is one of the main causes of excessive vibrations. In scientific literature many works, related to the measurement of forces induced by a single volunteer, or few of them, can be found; but the extension of these results to a crowd is a non trivial operation because of crowd synchronisation effect; moreover obvious practical problems arise in measuring the forces due to many people. This work presents an innovative algorithm to estimate such an excitation without needing a direct force measurement but relying only on the knowledge of the motion of each subject in the crowd. As shown in a previous research, the motion of people in a crowd can be estimated through digital image correlation, starting from a movie of the stadia stand. The method proposed in this work was tested both for jumping and bobbing, within all the typical range characterizing these kinds of movements (1.5-3.5 Hz) and the obtained results are then validated with the signal acquired by a dynamometric platform. The results show an excellent correlation between expected and measured loads in the whole range, both for jumping and bobbing.