Objective: The phenomenon of synchronous lateral excitation caused by pedestrians walking on footbridges such as the London Millennium Bridge has increasingly attracted public attention. This excitation phenomenon for example the triggering of the lock-in phenomenon and its self-limited nature has not been fully understood or modeled. Therefore, in this paper, a neural-oscillator-model is investigated to grasp some useful information for human-induced lateral vibration on congested pedestrian bridges.
Methods: The oscillator model consists of two simulated neurons arranged in mutual inhibition, as shown in Fig.1. Dynamic response analyses taking into account the neural oscillator proposed by Matsuoka is carried out for the pedestrian bridge model with the center span length of 50 m, placing much emphasis on the lock-in phenomenon.
Results: Fig.2 shows the oscillator (pedestrian walking on the bridge) frequency which is obtained by zero-crossing method for the time history oscillator output. It can be seen from this figure that the oscillator frequency varies gradually, and is entrained to be equal to 1.000 Hz which is the lateral natural frequency of the bridge.
Conclusions: The results are summarized below:
(1) The oscillator behavior is investigated and the oscillator’s entrainment property is clarified
(2) A simplified method to evaluate the frequency of the neural-oscillator model is proposed.
(3) Based on the results of dynamic response analyses, it is confirmed that the neural-oscillator might be one of the effective models to explain the synchronization (the lock-in phenomenon) of a fairly high part of all pedestrians being on the bridge.