Proposal and calibration of an human-structure interaction biomechanical model by the resolution of the inverse dynamic problem

The phenomena of interaction between pedestrians and structures is known since, at the end of the 19th century, a group of 60 soldiers excited, under its step, a bridge located in the British town of Broughton. Although the scientific community didn't stop studying this issue, it was the occurrence of the phenomenon happened in the Millennium Bridge (London) that stressed the importance of the problem and produced a higher level of attention. Large advances have been realized, from the above mentioned date, in the characterization of the interaction force that takes place between pedestrians and footbridges during the step of a pedestrian flow. Nonetheless, measured footbridge responses often deviate from the values predicted by these models. One of the main deficiencies of the existing models and international standards is the exclusion of the effect of changes in the footbridge's dynamic properties due to the presence of pedestrians. In this paper, the formulation of a human-structure interaction model is carried out and the calibration of its dynamic structural parameters is performed by the resolution of the inverse dynamic problem from the measures made on a real footbridge when a controlled number of pedestrians circulate on it. The model allows taking account of the changes in mass, damping and stiffness that a pedestrian might introduce to a footbridge and may affect the overall dynamic response of the structure. The model is especially useful for a more accurately characterization of the structural response of a footbridge under a pedestrian flow in order to check the standards comfort limits, and in the case, where these limits aren't guaranteed, the model allows a better characterization of the vibration control system parameters, and its corresponding performance, if its implantation was necessary..