Name: simulation of human-induced vibrations based on the characterized in-field pedestrian behavior
Uploaded: 2016-04-13T13:00:00
Description: Watch this Scientific Journal Video about Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior at JoVE.com

The experiments involving walking individuals are performed in cooperation with Movement &#38; posture Analysis Laboratory Leuven (MALL)25. Their cooperation and support is gratefully acknowledged.

All procedures were approved by the ethical committee of the university hospital of the KU Leuven and each subject gave a written informed consent prior to participation.
1. 3D Motion Tracking: Configuration and Data Acquisition
<ol>
	<li>Ensure that the individual sensors are fully charged (Figure 1A). This step takes about 1 hr but can be performed on the days prior to the actual measurements. Follow the manufacturer&#39;s charging protocol.</li>
	<li>MT Manager &#8212; Da...

<ol>
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Signal Process. 24 (1), 138-152 (2010).</li><li>The MathWorks Inc. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> MATLAB and Signal Processing Toolbox Release. , (2014).</li><li>Van Nimmen, K., Van den Broeck, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> PediVib 1.0 - A MATLAB toolbox for the simulation of human-induced vibrations. , (2015).</li><li>Li, Q., Fan, J., Nie, J., Li, Q., Chen, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crowd-induced+random+vibration+of+footbridge+and+vibration+control+using+multiple+tuned+mass+dampers.">Crowd-induced random vibration of footbridge and vibration control using multiple tuned mass dampers.</a> J. Sound Vib. 329 (19), 4068-4092 (2010).</li><li>Van Nimmen, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Numerical and experimental study of human-induced vibrations of footbridges [dissertation]. , (2015).</li><li>Middleton, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Dynamic performance of high frequency floors [dissertation]. , (2009).</li><li>Ing&#242;lfsson, E. T., Georgakis, C. T., Ricciardelli, F., J&#246;nsson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+identification+of+pedestrian-induced+lateral+forces+on+footbridges.">Experimental identification of pedestrian-induced lateral forces on footbridges.</a> J. 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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+spatially+unrestricted+pedestrian+traffic+on+footbridges.">Modeling spatially unrestricted pedestrian traffic on footbridges.</a> Journal of Structural Engineering. 136 (10), 1296-1308 (2010).</li><li>Agu, E., Kasperski, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+the+random+dynamic+parameters+of+the+human+body+on+the+dynamic+characteristics+of+the+coupled+system+of+structurecrowd.">Influence of the random dynamic parameters of the human body on the dynamic characteristics of the coupled system of structurecrowd.</a> J. 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Biomech. 47 (11), 2693-2699 (2014).</li><li>Liedtke, C., Fokkenrood, S. A., Menger, J. T., van der Kooij, H., Veltink, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+instrumented+shoes+for+ambulatory+assessment+of+ground+reaction+forces.">Evaluation of instrumented shoes for ambulatory assessment of ground reaction forces.</a> Gait Posture. 26 (1), 39-47 (2007).</li><li>Boutaayamou, M., Schwartz, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validated+extraction+of+gait+events+from+3D+accelerometer+recordings.">Validated extraction of gait events from 3D accelerometer recordings.</a> , 6-9 (2012).</li><li>Kavanagh, J. J., Menz, H. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accelerometry:+A+technique+for+quantifying+movement+patterns+during+walking.">Accelerometry: A technique for quantifying movement patterns during walking.</a> Gait Posture. 28 (1), 1-15 (2008).</li><li>. MALL: Movement and posture Analysis Laboratory Leuven (Interdepartemental research laboratory at the Faculty of Kinisiology and Rehabilitation Sciences) Available from: <a target="_blank" href="https://faber.kuleuven.be/MALL/mall.php">https://faber.kuleuven.be/MALL/mall.php</a> (2015)</li></ol>

The human motion and resulting GRFs are usually identified by the application of force plates, instrumented treadmills as well as optical motion capture technology such as Vicon18 and CODA19. The application of these techniques is, however, restricted to the laboratory environment. In answer to this drawback, the potential of innovative techniques that permit the measurement of &#39;natural&#39; person behavior over many repeated and uninterrupted cycles is currently investigated20. Alter...

Driven by the economic demand of efficiency and the increasing strength of (new) materials, architects and engineers are pushing the limits to build ever longer, taller and lighter structures. Typically, light and slender structures have one or more natural frequencies that lie within the dominant spectrum of common human activities such as walking, running or jumping. Likely to be subject to (near-)resonant excitation, they are often unduly responsive to human motion, resulting in disturbing or even harmful vibrations1. For these slender and lightweight structures, the vibration serviceability is a matter of growing concern, often constituting the critical design requirement.
The human motion and the resulting ground reaction forces (GRFs) are usually experimentally identified in laboratory conditions. Currently, designers are forced to rely on &#8212; what are assumed to be &#39;conservative&#39;&#160;&#8212; equivalent load models, upscaled from single-person force measurements. With designs governed by the dynamic performance under high crowd densities, a strong demand exists for the verification and refinement of the currently available load models.
The present protocol employs a 3D inertial motion tracking technique for the characterization of the natural motion of pedestrians. It is shown how this information can be used to define the correlation among the pedestrians as well as the corresponding induced loads. In a subsequent step, the characterized pedestrian behavior is used to numerically simulate the induced structural response. Comparison with the registered structural response allows to quantify the effect of unaccounted human-structure interaction phenomena, e.g., the added damping due to the presence of the pedestrians. The methodology is illustrated for full-scale experiments on a real footbridge where the structural response and the motion of the participants are registered simultaneously.

<table border="0" cellpadding="0" cellspacing="0" width="1081">
	<tbody>
		<tr height="65">
			<td height="65" style="height:65px;width:301px;">MTw Development Kit + MT Manager Software</td>
			<td style="width:107px;">Xsens</td>
			<td style="width:280px;">MTW-38A70G20-1</td>
			<td style="width:393px;">Development kit with wireless, highly accurate, small and lightweight 3D human motion trackers and accompanying click-in full body straps.</td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:301px;">True Impulse Kinetic Measurement System + NDI Open Capture Data Acquisition and Visualization System</td>
			<td style="width:107px;">NDI Northern Digital Inc.</td>
			<td style="width:280px;">791028</td>
			<td style="width:393px;">TrueImpulse measures reaction forces exerted by humans during a wide variety of activities.</td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:301px;">GMS-24</td>
			<td style="width:107px;">GeoSIG Ltd</td>
			<td style="width:280px;">Rev. 03.08.2010</td>
			<td style="width:393px;">(Wireless) accelerometers to register the structural vibrations.</td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:301px;">GeoDAS GeoSIG Data Acquisition System</td>
			<td style="width:107px;">GeoSIG Ltd</td>
			<td style="width:280px;">Rev. 03.08.2010</td>
			<td style="width:393px;">Graphical MS Windows application running under Windows 9x/NT/2000, providing a software interface between users and GeoSIG recorders GSR/GCR/GBV/GT.</td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:301px;">PediVib toolbox</td>
			<td style="width:107px;">KU Leuven</td>
			<td style="width:280px;">/</td>
			<td style="width:393px;">Software interface/toolbox to simulate the structural vibrations induced by pedestrians.</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:301px;">Metronome</td>
			<td style="width:107px;">/</td>
			<td style="width:280px;">/</td>
			<td style="width:393px;">A device to indicate the targetted pacing rate of the activity (free applications are available online for pc/laptop/smartphone).</td>
		</tr>
	</tbody>
</table>

simulation of human-induced vibrations based on the characterized in-field pedestrian behavior

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

First, it is shown how the accelerations registered near the CoM of the individuals can be used to characterize the consequent GRFs. The results are discussed here for a walking individual3. Fully comparable observations are made when rhythmical human activities, i.e., jumping and bobbing, are considered. Figure 7A and 7B show that the amplitude spectrum of the continuous vertical foot forces and the corresponding acceleration levels r...

Watch this Scientific Journal Video about Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior at JoVE.com

Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior

A protocol is presented for the characterization of the in-field pedestrian behavior and the simulation of the resulting structural response. Field-tests demonstrate that the in situ identified pacing rate and synchronization rate among the participants constitute an essential input for the simulation and verification of the human-induced loads.

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With ...

The overall goal of this procedure is to use the tracked motion of pedestrians to characterize human-induced loads and subsequently, to verify the induced structural vibrations. This method can help to answer key questions in the field of human-induced vibrations, such as the characterization of the individual walking behavior, the identification of the correlation among pedestrians in a crowd, as well as the quantification of human-structure interaction phenomena. The main advantage of this technique is that it can be applied in-situ and thus allows us to analyze real traffic conditions.In-field observations are the only way to obtain detailed and accurate information on representative loading data. Therefore, they are essential for the further development and validation of the load models used for pedestrian excitation. Demonstrating the procedure will be Klaus Lievens, Xinxin Wei, and Krumka Kasapova, three PhD students of our research group, and Bram Gezels, an academic assistant.Use wireless motion trackers to register the motion of pedestrians. To configure the sensors, use the MT manager software to establish the wireless connection. Specify the desired sample rate, which should be at least 60 hertz to capture human motion.Then, make slow movements with the motion trackers until they are connected, and then continue by activating the measurement mode. Next, display the inertial data of all the active motion trackers. Now, attach a motion tracker as closely as possible to each participant's center of mass.Robustly fasten the motion tracker onto the participant so it is snug and secure. Now, data can be recorded as required. When making measurements in the laboratory, the motion of the human subject can be tracked simultaneously with ground reaction forces measured with a force plate.First, use the accompanying software to configure the force plate and acquisition settings. Select a gain and sample rate in accordance with the desired accuracy and the involved loading type. For human-induced loads, set the gain for a maximum force of 4, 879 newtons, and set the sample rate to 200 hertz.Always start and end a measurement with an empty force plate. Use the tare function or the automatic offset correction to reset the force when the plate is empty. Once tared, data can be recorded as required.For measurements performed on site, structural vibrations can be measured at relevant locations, such as at mid-span of a footbridge. To do this, use displacement, velocity, or acceleration sensing recorders. Configure the recorders according to the manufacturer's instructions.After placing the recorders at the desired locations, level them in agreement with a global reference frame. In the lab, after setting up motion trackers and the force plate, start the data recording. Then, ask the participant to step onto the force plate and stand still for at least 30 seconds.Thus, weigh the participant. Next, start a metronome to dictate the fundamental forcing frequency. Then, ask the participant to move at the pace of the metronome signal, such as by walking, jumping, or bobbing.Record this activity for a sufficient number of cycles, 60 cycles are recommended. When the cycles are complete, ask the participant to get off the plate. For experiments conducted on site on a civil structure of interest, set up the motion trackers and a network of sensors that will register the structural vibrations.In an outdoor setting, a megaphone can be used to amplify the metronome signal. On site, repeat the test at least three times, preferably four times, to check the repeatability of the experiment. In any setting when multiple acquisition systems are used and no trigger or common channel is available, synchronize the devices using a single event that each system can register, such as a strong impact.Add synchronizing events to the beginning and end of each test. Based on these events, the data of the different systems can be synchronized offline. When performing dynamic measurements with more than one type of sensor, synchronization of the data is essential.Therefore, we either try to use a single data acquisition system or for the systems to record a common signal. Begin by identifying the time between the nominally identical events of the load cycles. For the reference lab experiments, perform this step on both the pedestrian motion data and the force plate data.After loading the data, specify the sampling rate and estimate the average loading frequency. Also, specify the relevant time window if needed. The most critical step in this procedure lies in the identification of the onset of each load cycle from the tracked pedestrian motion.It is this timing information which allows us to compute the time-variant pacing rate of the pedestrian. For the analysis of the experiments in the lab, exclude the first and last five cycles from the analysis and work with the remaining 50. Be sure to visually check the timing information before saving the data.Now, compute the average fundamental loading frequency as the inverse of the average time in between the subsequent load cycles. When multiple pedestrians are involved, the identified timing information can be applied to analyze their correlation. For the analysis of the experiments on site, the next step is to use the identified timing information to simulate the induced structural response.Firstly, define the modal parameters of the test structure. These include the natural frequencies, modal damping ratios, and the mass-normalized modal displacements. Be sure to visually check the modal input information before proceeding.Secondly, define the characteristics of the pedestrians and their induced loads. These include the load type, weight, walking path or location, average pacing rate, and timing of the load cycles. Specify the solution parameters, such as the output locations, as well as the time parameters.Then, run and save the simulated structural response for the involved participants. As before, visually check the results before proceeding. Thirdly, compute the total structural response through superposition of the individual responses by summing the corresponding vectors.Then, compare the result with the measured structural response with a graphical representation of the data. From a single pedestrian tested in the lab, the onset of each load cycle was identified. This data is used to simulate the walking forces, shown in blue, and compare to the measured forces, shown in black.A good approximation of real walking forces was obtained. Similarly, the walking behavior of six pedestrians on a footbridge was analyzed. Again, the onset of each load cycle was identified from the tracked pedestrian motion.This load cycle information was then used to simulate the pedestrian-induced forces. After about 16 seconds, the pedestrians were walking in step, while after 50 seconds, a significant loss of synchronization was observed. By comparing the timing of the load cycles among the pedestrians, the synchronization rate was found to decrease to 60%after about 50 seconds.The structural response was then simulated. When the pacing rate of the pedestrians was assumed to be constant and identical to the metronome signal, shown in gray, the result significantly overestimated the measurements, shown in black. When the simulation accounted for the identified time-variant pacing rate, shown in blue, it was clearly closer to the measured response.This procedure can be applied to analyze the natural walking behavior of pedestrians. In this way, essential input is provided for the development of suitable models for the correlation among pedestrians. In addition, the comparison between the measured and the simulated structural response allows us to validate and calibrate the load models used for pedestrian excitation.By doing so, also the impact of human-structure interaction phenomena, such as added damping, can be investigated.

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