Experimental And Simulation Study On Pedestrian Flow With Horizontal And Vertical Bottleneck Constraints

With the rapid development of the urban economy and the gradual advancement of urbanization,pedestrians travel frequently and large-scale activities are increasing.Due to the complicated composition of collective crowds,pedestrian safe evacuation is facing severe challenges.Many pieces of research have indicated that pedestrian evacuation process in the built environment is constrained by a series of evacuation facilities in both horizontal and vertical directions.Therefore,this work aims at the actual demand for safe evacuation in typical crowded places and explores pedestrian dynamics under the combined effect of bottleneck based on experimental and simulation methods.The research of this work is mainly divided into four parts,as below:1.Experimental study on the effect of exit setting adjustment on pedestrian flow features.In total,around 100 students were recruited to participate in a series of pedestrian evacuation experiments,including varying door sizes and locations under emergency conditions.The total evacuation time,flowrate,interval time between the two successive individuals and burst sizes were measured and analyzed.The results showed that larger door width means higher egress efficiency and larger burst sizes.Further explored the features of exit flow,it can be found the time lapses between two successive pedestrians displayed heavytailed distribution in all the scenarios studied.Besides,the effect of the boundary layer and the effective width of evacuation on pedestrian dynamics was observed.The results of this paper indicate that exit location is also one of the factors affecting the efficiency of pedestrian evacuation.In narrow exit conditions,the specific capacity of the exit gradually decreases as it moves from the middle of the wall to the lateral wall.As door widths increase,this behavior disappeared.Finally,we contrasted the experimental results with relevant studies and described the necessity of carrying out experiments with pedestrians.2.Experimental study on the impact of stair construct on pedestrian single-file movement.This work designed and built an experimental platform for studying the characteristics of pedestrian dynamics on stairs.More than 100 volunteers were recruited to participate in a series of single-file movement experiments on this stairs platform.Pedestrian dynamic features on stairs were investigated by considering the impact of pedestrian density,as well as the stair inclination,including the tread depth and riser height of each step.With the extracted pedestrian trajectories information on the staircase from the recorded video,the relationship between the free movement speed and headway distance,minimum headway distance were analyzed.We found that a unified behavioral mechanism exists between pedestrian single-file movement in the plane and stair by analyzing the time spatial diagrams and headway distance distribution.Besides,the characteristics of pedestrian movement,i.e.,free movement speed and headway distance,varies when stair geometry features were different.Thus,we established a model for predicting pedestrian free walking speed under various stair constructs.Finally,we found the stair inclination has a significant influence on pedestrian speed and stair capacity with the fundamental diagram method.The data and results of this work would provide references for the pedestrian evacuation design in large buildings,terminals or stations.It can also help in improving the reliable ability of pedestrian simulation models,resulting in realistic simulation outputs of pedestrian movement on stairs.3.Simulation of pedestrian dynamics under horizontal bottleneck constraints.Pedestrian flow through narrow exits or passageways is one of the most common scenarios of crowd dynamics and evacuation.It is particularly important to simulate the pedestrian flow in these scenarios accurately.The simulation accuracy is highly dependent on the ability to produce realistic exit flow rates.Thus,firstly four parameters that are most crucial for physical interactions of the social force model were identified.Then these parameters were calibrated against two structured pedestrian experiments.With these calibrated parameters,we discussed the rationality and applicability of the sensitive parameters for pedestrian simulation under normal conditions and emergency conditions.Besides,we re-visited the basic questions which relate to the pedestrian bottleneck dynamics,i.e.,the effect of exit location,bottleneck length and obstacles on pedestrian egress.Our simulation results indicated that:(1)The effect of the exit location on pedestrian egress efficiency is uncertain,the evacuation efficiency is also related to the exit width and the level of urgency;(2)The "pass-way" after the exit also named as the bottleneck length a negative influence on the evacuation performance only in the scenarios that the length is not more than 2.0 m.When the bottleneck length exceeds 2.0 m,pedestrian outflow efficiency reaches an asymptotic value.(3)In case of emergency conditions,setting an obstacle near an exit is not leading to a longer pedestrian evacuation time,instead,it effectively improving pedestrian evacuation.4.Simulation of pedestrian dynamics under vertical bottleneck constraints.As far as we concern,in addition to comparing the outflow rate mentioned above as a benchmark to verify the reliability of the model,another valid method is to compare the pedestrian fundamental diagram distributions because these diagrams directly reflect the dependence of speed or flow on crowd densities.Therefore,based on the experimental data of pedestrian dynamics on stairs obtained in the above part of this thesis,we developed a pedestrian stairway model which can be applied to different staircase geometric structures.By comparing the density/velocity relations of the simulation output with the experimental results,the sensitive parameters of the model were confirmed and calibrated.Meanwhile,we demonstrated the generalization ability of the calibrated model by contrasting the outputs with other relative experimental results.Finally,we analyzed the stairs geometric structure,the combination effect of exit and staircase,and merging flow on pedestrian movement.The simulation results quantified the influence of different staircase geometry on pedestrian movement.Specifically speaking,under the combined conditions of "exit" and "stairs",the width of the stairs has little effect on capacity,and the capacity of pedestrians is mainly affected by the stair part.Besides,we confirmed factors,i.e.,pedestrian density and pedestrian merging types,have significant influence on the pedestrian merging ratio and subsequent floor capacity.