Jump Around Seismic Experiment 2006


Attention all Shear-wave Splitters, Undergrads, Grads, Faculty and Badger Football Fans,

This Saturday (Nov. 18, 2006) marks the end of the 2006 successful badger football season.  As many of you are aware, the Student Geophysical Society of the University of Wisconsin-Madison as part of the Society of Exploration Geophysicists will be making the most of a time-honored badger football tradition.  We intend to use the 4th quarter intermission "Jump Around" tradition in the student section as a low-frequency, controlled excitation source for 2D Reflection Seismic Sounding. 

All are invited to participate.  Here's what we need.  Anyone interested in assisting with the collection of data, please meet at Dante Fratta's office (2228 Engineering Hall) at 11 am Saturday morning.  Anyone going to the game (e.g., Shear Wave Splitters), jump higher and think "propagation."  Finally, anyone not in either of the above-mentioned categories, jump in your home or stamp your feet at some point between the 3rd and 4th quarter and perhaps it will help.

For those interested in participating with the data collection, please send me an email so we can get a head count. 

We certainly hope to capture some fantastic irreproducible results.  GO BIG RED!

John Carlos Naranjo

In addition, we will deploy three broad-band seismometers at locations marked on the map above. The plan is to record 100 samples per second for about an hour beginning at 19:30 UTC Saturday 2006-NOV-18.

The instruments are Guralp CMG3-ESPD's, broadband sensors with on-board digitizers, nominal ~flat response 60 seconds to 50 Hz. The accompanying dataloggers are SAM disk recording units.

Kurt Feigl & Lee Powell







DATA

photos of Geo-badgers at work



John, Francisco, Randy, Manuel and Matt, fully loaded


Kurt, Francisco and Randy at BB2



Randy at BB3

Site Occupation Table

code
intsrument
observers
location
photo
distance from source
latitude
longitude
BB1 UW05
Matt & John
Parking Lot West of Engineering Building

0.13
43deg 04.305min N
89deg
24.679 min W
BB2 UW01
Francisco & Manuel
Access Road Near Birge Hall
photo
0.73
43deg 04.446min  N
89deg 24.277min W
BB3 UW07
Kurt & Randy
The Terrace photo
1.21
43deg 04.602min
89deg 23.977min W
 
 

Detailed Location Maps

Download Google Earth KMZ
Source - Student section, north end Camp Randall
BB1 - Parking Lot West of Engineering Building - 0.13 km from source
BB2 - Access Road Near Birge Hall - 0.73 km from source
BB3 - The Terrace 1.21 km from source


Data from Broad Band Seismometers

Raw data in CGF format (all data)
Raw data in CGF format (interesting time interval 19:00 to 20:00 UTC)

Traces from all 3 components from all 3 instruments for 1 hour (band-pass filtered)
Traces from all 3 components for site BB3 (instrument UW07) 3 minutes (band-pass filtered)

References

May 5, 1992 - Bastia, Corsica;


17 people are killed and 1,900 injured when a temporary grandstand, erected to increase the capacity of the stadium from 8,500 to 18,000, collapses before a French Cup semifinal match between four-time defending league champion Olympique Marseille and second-division Bastia.

http://www.crowddynamics.com/Disasters/Stadium%20Disasters.htm


I could not find out if the cause was resonance or mass.

Human-Structure Interaction in Cantilever Grandstands

A degree [sic] submitted for the degree of Doctor of Philosophy

Jackie Sim
Balliol College, Oxford
Hilary Term 2006

There is a risk that excessive vibration in long span cantilever grandstands can be
triggered by the spectators synchronising their jumps to the music played.  If the
jumping frequency excites a resonance of the grandstand, large force could be
generated.  This thesis studies human-structure interaction in cantilever grandstands,
with emphasis on modelling the passive and jumping crowds, and analysing the
response of a single degree-of-freedom (SDOF) structural system.

Preliminary work on analysing a cantilever occupied by seated humans shows that it
is acceptable to use a SDOF structural system for analysis which meant emphasis of
later work could be placed on understanding the interaction between a passive crowd
and the structure.

Human dynamic models from published biomechanics studies are used to develop a
passive crowd model.  A transfer function, fitted to the crowd apparent mass, is used
to define the crowd model.  It is found that the passive crowd can be approximated
well by using a single 2DOF system.  The combined passive crowd-structure system
is modelled as a feedback system and a parametric study is conducted.  It is found that
the passive crowd adds significant mass and damping to the structure and these effects
vary with the natural frequency of the structure.

Records of forces of people jumping to a beat are used to develop a probabilistic
model of crowd jumping loads.  Key parameters are introduced to characterise the
timing and shape of the jumping impulses.  An analytical function is used to
approximate the impulse shape.  All parameters are characterised with probability
distribution functions.

Using the fitted probability distribution functions, the Monte Carlo method is used to
simulate individual jumping load-time histories and to obtain the structural responses
due to group jumping loads.  The variations of the structural response with the natural
frequency of the empty structure and the size of the active crowd are presented in
charts.  As expected, the worst response is found on structures with natural
frequencies coinciding with the first three harmonics of the crowd jumping loads.  For
structures occupied by passive crowds, a significant reduction in the structural
response is found at resonance excited by the second and third harmonics, due to high
levels of damping provided by the passive crowds.  On variation of the structural
response with the crowd size, it is found that the structural response becomes
asymptotic for groups larger than 16 people.

http://www-civil.eng.ox.ac.uk/publications/theses/sim-part1.pdf

Experimental study of human-induced dynamic forces due to bouncing on a perceptibly moving structure

S. Yao, J.R. Wright, A. Pavic, and P. Reynolds
Can. J. Civ. Eng./Rev. can. génie civ. 31(6): 1109-1118 (2004)

This paper describes the first direct measurements of human-induced dynamic forces due to bouncing on a perceptibly moving force platform. A unique test rig, permitting a person to bounce physically on an idealized "single-degree-of-freedom system" with variable natural frequency and mass, is described and the test methodology explained. A set of representative results for different structure and bouncing frequencies is presented for one test subject. These results clearly demonstrate the effect that the flexibility of the structure has on the levels of force and dynamic response achieved. In particular, it was established that the applied force drops considerably when the subject bounces at a frequency fairly close to the natural frequency of the structure. However, it was found that it was physically not possible to bounce at or very close to the natural frequency for the configuration of the test rig chosen. Finally, the acceleration and displacement responses indicate that both the first and second harmonics of the bouncing force are capable of producing a near resonant response.

Key words: crowd loading, flexible structure, dynamics, human-structure interaction, bouncing, jouncing, bobbing.

http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?_handler_=HandleInitialGet&journal=cjce&volume=31&calyLang=eng&articleFile=l04-081.pdf

 

Changes of modal properties of a stadium structure occupied by a crowd

Paul Reynolds, Aleksandar Pavic and Zainah Ibrahim

The University of Sheffield
Department of Civil and Structural Engineering
Sir Frederick Mappin Building
Mappin Street, Sheffield, S1 3JD, UK

This paper presents results obtained from ambient vibration measurements using a remote monitoring system
(RMS) on a grandstand in Bradford, United Kingdom. Using this RMS, output-only vibration response data were
acquired when the stand was empty and when it was occupied during football and rugby matches. For the
occupied stadium, modal properties that corresponded to different crowd activities (sitting, standing and jumping)
were also extracted. The configurations of the crowd occupation during sporting events were monitored by
correlating vibration response data with synchronised video images. Modal parameter estimations were made on
data that were acquired from several events, hence improving the statistical reliability of the estimates. The
observations showed that seated crowd occupation led to a decrease in natural frequencies and an increase in
damping ratios. Further decreases in natural frequencies were observed when the crowd stood and/or jumped
following the scoring of a goal. These observations show that crowd occupation does not only contribute mass to
structure, it acts as a dynamic system that interacts with the structure it is occupying. Furthermore, it has
properties that vary according to the crowd configuration.

http://scholar.google.com/url?sa=U&q=http://vibration.shef.ac.uk/pdfs/IMAC_XXII.pdf