Study On Pedestrian Loads Basing On Biomechanics And Calculation Of Human Walking Induced Structural Vibration

The walking forces acting on footbridges and long-span floors are obtained through walking force tests on force plate or insole step forces measurement system. The method based on experiments often faced with two problems:(1) constrained by experimental conditions, walking force tests ignore the effects that human-structure interaction (HSI) and human-human interaction (HHI) in the real environment on walking forces; (2) due to the lack of fine analysis of walking gait, there are some special problems, such as the formation mechanism of negative damping, and the phenomenon of structural vibration instability basing on negative damping mechanism that walking force tests can’t make a clear interpretation.Aimed at above problems, the bipedal walking model considering human body dynamic features built in the field of biomechanics is used to study the characteristic of walking force considering HHI and the mechanism of HSI in this paper. The main researches carried out in this study are summarized as follows:1. The validation of bipedal walking model. This paper has introduced the center of pressure excursion to correct traditional bipedal model, and simulated the walking force under different body characteristic parameters. At the same time, compared the simulation results with experiment data in the form of spectrum through Fourier Transform, and confirmed the validity of modified bipedal model. Further, results shown that body characteristic parameters have an important influence on walking force.2. The study of spectral characteristics of walking force based on bipedal model. Combined the fundamental relationship between crowd density and velocity, the relationship between walking force and crowd density was built through simulation of walk under certain body characteristic parameters. First, the independent parameters of bipedal walking model were determined through sensitivity analysis. Second, the uniform experiment design method and ACE regression method were used to build the response surface between input parameters and walking force simulation result. Thirdly, relationships between dynamic load factors and step frequencies are counted through Mont Carlo simulation based on response surface.Finally, an example was provided to elaborate the way analyze structural dynamic response under a certain crowd density.3. The structural dynamic calculation considering HHI. First, the general rules of structure dynamic response under different crowd densities were studied based on walking force of a certain body characteristic parameters, which shown that the relationship between dynamic response under single pedestrian action and crowd action is no long subject the multiple relationship of N0.5 when considering the interaction among pedestrian. Second, the simplified calculation formulas were provided to compute dynamic response. Finally, the correctness of simplified calculation formulas was verified with example.4. The qualitative analysis of HSI based on bipedal walking model. The walking forces when pedestrian walking on a vibration interface were approached by simulation of bipedal walking model under harmonic loads with different combination of amplitudes and frequencies imposed on centroid. The additional components related to structure vibration were obtained through Fourier Transform, which reflecting the influence that structural vibration on walking force. Further, the additional component was decomposed to additional damping and mass related to vibration velocity and acceleration respectively through Fourier Transform. The instability of structural vibration would occur when structural damping offset by additional damping induced by crowd.5. The study of coupled human-structure dynamic system based on bipedal walking model. The dynamic system of double particle human body model coupled with structure was built on the basis of relevant literature. The real-time dynamic interaction was exhibited though this coupled model, further, the simulation results show that it’s necessary to consider HSI when structure is flexible.