Computational Study Of Pedestrian Bridge Vibration Response Under Random Crowd Load Excitation

In recent years,with the rapid development of China’s economy,in order to meet the demand of pedestrian travel traffic,high-strength,lightweight,and large-span pedestrian bridge structures began to emerge in large numbers in the construction market.These structures usually have small damping,resulting in high sensitivity of pedestrian bridge vibration response to changes in pedestrian load excitation frequency.As an important source of human comfort and pedestrian bridge usability problems,pedestrian loads have obvious multi-behavior and stochastic characteristics during walking,which not only lead to abnormal vibration conditions of the structure in the vertical direction,but also cause structural lateral instability problems more easily.In this paper,the vertical vibration problem of the structure under unidirectional and bidirectional crowd load excitation is firstly studied in comparison,followed by the proposed crowd-structure lateral interaction model with bidirectional interaction of crowd-structure system considering pedestrian perception and self-regulation mechanism,and the pedestrian walking characteristics and structural vibration situation when single pedestrian and crowd Lock-in behaviors occur are discussed separately.Finally,a joint MATLAB-COMSOL simulation of the pedestrian bridge vibration response computational m odel is developed to consider the pedestrian perception and feedback of the structural acceleration response at their foot position during walking.This article examines the following aspects :1)The study proposes a vibration control method for pedestrian bridges with two-way crowd flow diversion.A microscopic social force model is used to simulate the unidirectional and bidirectional crowd flow,and the vibration reduction study with controlled excitation sources is conducted for the vertical excess vibration of the pedestrian bridge caused by the bidirectional crowd flow.Based on the field experiments of the laboratory steel-glass pedestrian bridge and the simulation results of the MATLAB simulation platform,the vibration damping effect of the method is verified.2)A coupled model of crowd-structure lateral interaction with bidirectional interaction of pedestrian-structure system considering pedestrian perception and self-regulation mechanism is developed.By defining the pedestrian perceptible deceleration threshold,lock-in threshold,stopping threshold and pedestrian deceleration function,the possible Lock-in behavior,changes in step frequency,step speed and changes in the lateral acceleration response of the pedestrian bridge when a single pedestrian passes through the pedestrian bridge at different step frequencies are investigated.Finally,the lateral vibratio n of the pedestrian bridge under one-way and two-way crowd load excitation is explored.3)A computational model of the vibration response of a pedestrian bridge with a joint MATLAB-COMSOL simulation is established.With the powerful capabilities of COMSOL finite element software in refinement modeling and the advantages of MATLAB in computational programming,a link between the two was established by technical means.The social force model is used to simulate the crowd motion in MATLAB,and the simulation results of each step are loaded into the finite element model established by COMSOL to calculate the structural response,and the structural response results are fed back to the crowd simulation,and the two software are used interactively in the joint simulation to realize the pedestrian’s perception and feedback of the structural acceleration response at his foot position.