The Modal Parameter Identification And Crowd-induced Vibration Analysis Of Floor Of Large-span Waiting Hall

Abstract:As one of the main carriers of the force tolerance and transmission, the static and dynamic performance of the floor will directly affect the normal use of structure. Modern large-scale train station structure systems usually use a large number of high strength lightweight materials, the large-span floor of waiting hall tend to possess small damping and low natural frequency. Thus, it is meaningful to study the simulation and analysis of large-span structures under crowd-induced load. This paper will carry out the research work from three aspects:the modal parameter identification, the generation of crowd-induced load models and the response of large-span floor under emergency evacuation condition. The main contents are listed below:1. Beijing South Railway Station, which is in the spring festival peak travel season, is taken as the study object. Vibration test on the floor of the large-span waiting hall is firstly conducted. After the time-domain filtering for the data, STD, PRCE and SSI are utilized respectively to identify the natural frequency and damping of the structure. After the comparison between the test results and the finite element result, the effectiveness of the three modal identification methods to large-span floor will be evaluated and the dynamic properties of this structure will be analysed. Considering the identified modal parameters, a modified finite element model of the floor of the large-span waiting hall is established. The mass modification parameter is determined.2. Then on the basis of the conclusion of accurate crowd-induced load model, the hypothesis setting upon ideal mathematical model and the common equivalent crowd-induced load model, the paper simplifies the stochastic crowd-induced load model, which considers the probability distribution of human gait parameters. And on the basis of the research result in transportation and biological fields by Venuti and Bruno, the predictive crowd-induced load model, which reflects the relationship between the pedestrian flow density and the pedestrian velocity is generated. Finally, through comparing and analyzing the vibration responses of the floor of large-span waiting hall under different load models, the merits and demerits and the application scopes of each method are discussed. These conclusions will provide theoretical foundation for the development of accurate crowd-induced load model that is more workable on large-span floor.3. Summarize and predict the possible evacuation routines for passengers in Beijing South Railway Station, combining simulation results of crowd evacuation in traffic research area and actual train formation to build passenger arrival model, determine four emergency evacuation load conditions that are based on crowd behavior features, analyze the dynamic response of floor under evacuation conditions, evaluate the comfort and safety of structure and propose suggestions to the structures optimization.