Analysis on the vertical coupled dynamic effect of a crowd-bridge system based on the social force model

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Journal of Vibration and Shock ›› 2020, Vol. 39 ›› Issue (9) : 71-79.

ZHANG Qiong1, NAN Nana1, ZHU Qiankun1,2, DU Yongfeng1,2

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Abstract

For more and more structural vibration problems of lightweight flexible footbridges under random crowd loading, it is particularly important to establish a stochastic crowd model considering the crowd-structure interaction in order to obtain more realistic and accurate vibration responses.A moving spring-mass-damping model was used to simulate the dynamical characters of a single pedestrian, and the movement model of a random crowd was established based on the social force model.Then a random crowd load model considering the crowd-structure coupled vibration was built.According to the dynamic balance of the pedestrian bridge and the random crowd at any time, the control equation for the coupled vibration of the crowd and the bridge was established.The variation of footbridge dynamic parameters in pace with the crowd motion was solved by the state space method and the control equation for the coupled vibration was solved by the mode decomposition method.The influence of random crowd load on the modal and vibration responses of the pedestrian bridge considering crowd-structure coupled vibration was discussed.The results show that the modal variation of the coupled system increases along with the increase of pedestrians.The pedestrian-structure interaction and pedestrian randomness are of marked effect on vertical dynamic responses so they should not be ignored while analysing the vibration of light-weight footbridges.Compared with the peak acceleration, the RMS acceleration can weaken the disturbance of random fluctuation, so 1-s RMS acceleration is more reasonable to be used in measuring structural vibration responses.

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light-weight footbridge / crowd-bridge coupled system / social force model / modal analysis / dynamic response analysis

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ZHANG Qiong1, NAN Nana1, ZHU Qiankun1,2, DU Yongfeng1,2. Analysis on the vertical coupled dynamic effect of a crowd-bridge system based on the social force model[J]. Journal of Vibration and Shock, 2020, 39(9): 71-79

References

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