The Vertical Dynamic Properties of Flexible Footbridges under Bipedal Crowd Induced Excitation

Yan-An Gao,Juan Wang,Min Liu

doi:10.3390/app7070677

Yan-An Gao, Juan Wang + Show 1 more

Open Access

https://doi.org/10.3390/app7070677

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Abstract

The excessive vibration of footbridges caused by walking pedestrians has generated great public concern in recent years. However, it has not been explored how crowd size quantitatively influences structural dynamic properties, including human dynamic properties. This paper provides an alternative method for understanding how crowds excite the excessive sway motion of a large-span structure when walking on it. In this study, pedestrians are modeled by a walking dynamic bipedal system. The crowd-structure system is established based on the bipedal model, for which the dynamic properties from pedestrians are considered. The vertical dynamic property equations of structure are calculated under crowd-induced vibration, based on the assumption of a uniformly distributed crowd. Through the proposed framework, the changes of frequency and damping of structure induced by walking pedestrians are studied. The increase of the crowd size can reduce structural frequency, but increase its damping. The impact tendency of crowd size on structural dynamic properties is consistent with measured results. This research provides insight as to how crowd size quantitatively influences the change of structural dynamic properties.

Highlights

Long-span structures, e.g., footbridges, have become prevalent all over the world, and the excessive dynamic vibrations induced by locomotive crowds are a crucial maintenance concern for their life span
Full-scale dynamic measurements on service structures has shown that humans can change structural vertical dynamic properties [1,2], which has been confirmed by a measurement experiment on a beam bearing different numbers of persons in Shahabpoor et al [3]
This paper proposes some formulas for vertical model property estimation, considering crowd size variation, based on a uniform distribution assumption with consistent walking behavior

Summary

Introduction

Long-span structures, e.g., footbridges, have become prevalent all over the world, and the excessive dynamic vibrations induced by locomotive crowds are a crucial maintenance concern for their life span. Shahabpoor et al [3] studied the effect of crowd size on vertical modal parameters of an occupied structure by and Yang Frequency [11,12,13], the Response theoretical Function mechanisms between crowd and structural modal properties by extensive (FRF)‐based modalsize identification tests. They using this model have not yet been reported.

The of themass beamofis q

Excitation Assumption

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