A Robust Methodology for the Reconstruction of the Vertical Pedestrian-Induced Load from the Registered Body Motion

Nimmen, Katrien Van; Zhao, Guoping; Seyfarth, André; Broeck, Peter Van den

doi:10.3390/vibration1020018

Cited by 18 publications

(19 citation statements)

References 28 publications

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“…For example, the feet do not (or barely) move during the bouncing motion. Similar observations are made for walking [25,26]. It is outside the scope of this paper to biomechanically identify the mass distribution and activated mass of the person during the dynamic bouncing motion.…”

Section: Verification Of the Experimental Methodsupporting

confidence: 59%

Data‐Driven Synchronization Analysis of a Bouncing Crowd

Chen

Tan

Nimmen

et al. 2019

Shock and Vibration

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Vibration serviceability problems concerning lightweight, flexible long-span floors and cantilever structures such as grandstands generally arise from crowd-induced loading, in particular due to bouncing or jumping activities. Predicting the dynamic responses of these structures induced by bouncing and jumping crowds has therefore become a critical aspect of vibration serviceability design. Although accurate models describing the load induced by a single person are available, essential information on the level of synchronization within the crowd is missing. In answer to this lack of information, this paper experimentally investigates the inter- and intraperson variability as well as the global crowd behavior in bouncing crowds. A group size of 48 persons is considered in the experiment whereby the individual body motions are registered synchronously by means of a 3D motion capture system. Preliminary tests verified a new approach to characterize the bouncing motion via markers on the clavicle. Subsequently, the full-scale experimental study considered various crowd spacing parameters, auditory stimuli, and bouncing frequencies. Moreover, special test cases were performed whereby each participant was wearing an eyepatch to exclude visual effects. Through the analysis of 330 test cases, the interperson variability at the bouncing frequency is identified. In addition, the cross-correlation and coherence between participants are analyzed. The coherence coefficients between each pair of participants in the same row or column are calculated and can be described by a lognormal distribution function. The influence of the spatial configurations and visual and auditory stimuli is analyzed. For the considered spatial configurations, no relevant impact on the inter- and intraperson variability in the bouncing motion nor in the global crowd behavior is observed. Visual stimuli are found to enhance the coordination and synchronization. Without eyesight, the participants are feeling uncertain about their bouncing behavior. The results evaluating the auditory cues indicate that significantly higher levels of synchronization and a lower degree of the intraperson variability are attained when a metronome cue is used in comparison to songs where the tempo often varies.

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Section: Verification Of the Experimental Methodsupporting

confidence: 59%

Data‐Driven Synchronization Analysis of a Bouncing Crowd

Chen

Tan

Nimmen

et al. 2019

Shock and Vibration

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“…10 gives an example of the vertical acceleration levels registered on the lower back of Pedestrian 1. Based on the measurements of all USB sensors, the time-variant pacing rate for each pedestrian was determined, using the procedure detailed in Van Nimmen et al (2018). The steps taken within 2 m of each end of the bridge deck, i.e., where the pedestrians slowed down to turn around, were excluded from the analysis.…”

Section: Distribution Of Step Frequenciesmentioning

confidence: 99%

“…That being said, it may be argued that this dataset will allow the derivation of some general characteristics of crowd dynamics on footbridges, such as the strength of the boundary forces and the repulsive interaction forces between pedestrians, as used in the widely applied social force model for pedestrian dynamics (Helbing and Molnar 1995;Helbing et al 2005). Conversely, the registered 3D body motion allows the time-variant pacing rate of each pedestrian to be identified (Bocian et al 2018;Van Nimmen et al 2018). Some impressions of this large-scale measurement campaign are given in Fig.…”

Section: Introductionmentioning

confidence: 99%

Eeklo Footbridge: Benchmark Dataset on Pedestrian-Induced Vibrations

2021

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Vibration serviceability under crowd-induced loading has become a key design criterion for footbridges. Although increased research efforts are put into the characterization of crowd-induced loading, including related interaction phenomena, and first-generation design guides are available, a major challenge lies in the further development and validation of prediction models for crowd-induced vibrations. Full-scale benchmark datasets that simultaneously register structural and crowd motion make an invaluable contribution to meeting this need by providing detailed information on representative operational loading and response data. Currently available datasets either (1) involve a (too) small number of pedestrians or (2) do not involve the simultaneous registration of pedestrian and bridge motion, or else they involve a footbridge (3) where only a single mode or a very limited number of modes are sensitive to walking excitation, (4) for which no suitable digital twin is available, or (5) that is not open access. This paper therefore presents a new and publicly available full-scale dataset collected specifically for the further development and validation of models for crowd-induced loading. The dataset is collected for a real footbridge, with a number of modes that are sensitive to pedestrian-induced vibrations, and with a digital twin available. The pedestrian and bridge motions are registered simultaneously using wireless triaxial accelerometers and video cameras. In addition to two data blocks involving purely ambient excitation, four data blocks are collected for two pedestrian densities, 0.25 and 0.50 persons/m 2 , representing a total of more than 1 h of data for each pedestrian density. Analysis of the structural response shows that the different data blocks can be considered representative for the involved load case. The identified distribution of step frequencies in the crowd indicates a significant contribution of (near-)resonant loading for a number of modes of the footbridge. Furthermore, the dataset displays clear signs of human-structure interaction, suggesting a significant increase in effective modal damping ratios due to the presence of the crowd.

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“…The reconstruction of the vertical contact force using a single accelerometer located at the lower back near the 5th lumbar vertebra (L5) has been extensively investigated in the literature [9][10][11][12][13][14]. When the vertical contact force is reconstructed using a single inertial sensor, it is assumed that that the acceleration coincides with the body center of mass.…”

Section: Introductionmentioning

confidence: 99%

“…Denoth et al [15] proposed an alternative formulation using an apparent mass accounting for the fact that only a fraction of the body center of mass acceleration is registered. The factor was experimentally established in [12,13] and found to be dependent on the walking velocity with values ranging between 0.74 and 0.96. The values were established by applying a leastsquares minimization of the reconstructed and measured contact force in the time domain.…”

Section: Introductionmentioning

confidence: 99%

Contact Force Reconstruction from the Lower-Back Accelerations during Walking on Vibrating Surfaces

et al. 2021

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Current models describing the effect of crowd-induced loading require a full-scale validation. To measure the lower-back accelerations during such validation, low-cost accelerometers are used to ensure a sufficient scalability. The goal is to verify to what extent the low-cost sensors can be used for the contact force reconstruction in case the pedestrian walks on a vibrating surface. First, a data set is collected comprising the simultaneous registration of the lower-back accelerations and the contact forces. Three contact force reconstruction methods are presented to accurately reconstruct the contact force in case of walking on a rigid surface. Second, the focus is on the contact force reconstruction in case of walking on a vibrating surface. A numerical study is performed adopting quantities of the Eeklo Benchmark Dataset providing a realistic framework. The additional lower-back accelerations as a result of the vibrating surface are estimated numerically. It is found that directly reconstructing the total contact force leads to inaccurate results. Instead, it is more suited to reconstruct the contact force one would induce on a rigid surface and combine this with an independent model to account for human–structure interaction. The conclusions of this numerical example are case-specific while the presented methodology is generic and can be readily extended to virtually any other structure.

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A Robust Methodology for the Reconstruction of the Vertical Pedestrian-Induced Load from the Registered Body Motion

Cited by 18 publications

References 28 publications

Data‐Driven Synchronization Analysis of a Bouncing Crowd

Data‐Driven Synchronization Analysis of a Bouncing Crowd

Eeklo Footbridge: Benchmark Dataset on Pedestrian-Induced Vibrations

Contact Force Reconstruction from the Lower-Back Accelerations during Walking on Vibrating Surfaces

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