Calibration of inverted pendulum pedestrian model for laterally oscillating bridges based on stepping behaviour

Abstract

Despite the problem of lateral excitation of bridges by walking pedestrians being intensively studied for over two decades, there is currently no model which could quantitatively explain pedestrian-generated lateral forces. The most promising of the models proposed thus far, that is the rigid-leg inverted pendulum model (IPM) confined to the frontal plane, has been previously shown to qualitatively capture the main features of pedestrian behaviour on laterally oscillating ground, including kinematics and kinetics. However, to make the model suitable for engineering applications, it needs be reconciled with observations. To this end, a dataset collected from pedestrians walking on a laterally-oscillating instrumented treadmill is used to derive fundamental properties of pedestrian walking gait. Informed by these findings, a foot placement control law is proposed ensuring good match between the outputs of the IPM and empirical data in terms of the main components of pedestrian-generated lateral forces. That control law is then parametrised based on pedestrian anatomical and gait characteristics, thus generalising the calibrated IPM and making it suitable for use in a predictive manner. Simulations of the lateral bridge response to the lateral loading from a crowd of pedestrians with random parameters and interacting with a bridge are also conducted. It is shown that the calibrated IPM can generate self-excited forces in close agreement with those measured and that the generalised IPM, producing slightly conservative loading predictions on average, can serve in the assessment of lateral structural stability.