Study On Vertical Vibration Response Of Structures Under Different Density Of Moving Crowd With Human-human Interaction

It is very easy to produce excessive vibration response for the large span footbridge or floor structure under the action of crowd walking,the excessive vibration not only make the structure cannot meet the normal limit state,but also cause structural instability.Existing research results indicate that the structure vibration response under the action of the crowd walking is N~0.5.5 times as many as the structure vibration response under the action of a single pedestrian,however,This multiple relationship applies just apply to people with low density,which is no interaction between pedestrians.When the pedestrian density is high,people-people interact with each other come out gradually,and then it may lead to two questions.On the one hand,the speed of pedestrians will decrease as the population density increases,and then change the spectrum structure of pedestrian walking force,on the other hand,the pedestrians have to change their walking habits and paths,which leads to the Phase and step frequency of pedestrian changed,and then caused crowd synchronization.because of the influence of above-mentioned two factors,current studies mainly focus on the analytical calculation of the structure vibration response under the action of the crowd walking without regard to the People-people interact with each other,but the studies of the structure vibration response under the action of the crowd walking less considered people-people interact with each other.To address this problem,the paper studied the structure vibration response under the action of the crowd walking in different density from the angle of People-people interact with each other,The main work and results are as follows.(1)Analysis of the vertical vibration response of structure under the influence of crowd walking in different densities.The increase of pedestrian density would lead the decrease of the walking speed,and consequently result the decrease of the step frequency and the fire-order component of the pedestrian loads.This can further change the increase law between structural vibration responses and pedestrian number.To solve the problem,the walking speeds varying with the crowd densities and furthermore the changing of the step frequencies are first taken into accounted in this paper through existing empirical relationship.And then the spectral parameters of pedestrian loads in different crowd densities are determined based on the step frequencies.At last,the formulae of the influence coefficient of pedestrian density are proposed.(2)The numerical simulation study of crowd synchronous effect based on cellular automaton.This chapter simulated the microcosmic motor behavior and the interaction of pedestrian by cellular automata model to obtain the motor process of one-way flow of people and two-way flow of people.Then Simulated the motor process of one-way flow of people and two-way flow respectively in different density,and statisticsed the law of the flow rate varies with the crowd density in in different density at at some point,and fitted the calculated expression between crowd density and the ratio of Synchronous start-stop.(3)Analysis of the vertical vibration response of structure under the influence of crowd walking in different densities with regard of people-people interacts with each other.This chapter established the calculation model of vertical vibration response of structure with regard of people-people interact with each other based on forced vibration theory,which make use of fixed multiplayer walking.And then simulated the vertical vibration response of structure under one-way flow of people and two-way flow of people with regard of people-people interact with each other in different density,and presented the structural equivalent response correction coefficient consult to equivalent synchronized pedestrian model.