VIBRATING BARRIERS: THE FUTURE OF STRUCTURAL
DEFENSE AGAINST EARTHQUAKES
OVERVIEW
Inordertoprotectsocietyfromearthquakes,engineersandseismologists
havedevelopedandimplementedvarioustechnologiestocounteractthe
damagingeffectsthattheywouldotherwiseinflict.Somepastattemptsat
“earthquake-proofing”buildingshaveincludedtheuseofsteelbracing,
bufferingsystems,andbuildingmaterialsthatarelesspronetofracturing.
Althoughthesemethodshavehadsomesuccess,theyarenoteffectiveona
largescale.Whileoldertechniquesofearthquakedefensewereusually
specifictoindividualbuildings,vibratingbarrier(ViBa)deviceswouldbeable
toprotectentirecitiesandsurroundingareas.TheoscillatorydesignofViBa
wouldallowittoreducethemagnitudeoftremorstosignificantlyless
harmfullevels.
Withfurthertestingandstudies,vibratingbarrierscanbecomeamore
effectivemechanismofprotectionagainstearthquakesthanprevious
technologies,makingsocietybetterequippedforanyfuturecalamities.
SCIENCEBEHINDTHEDISASTER
PhysicalProcesses
•Tectonicplates
•Makeupthelithosphere(earth’soutermostlayer)
•Moveslowlyovertime
•Generateearthquakeswhenforcefullygrindingpasteachotheralong
faultlines
•Forcebetweenplatesgeneratesvibrationsoflarge magnitude
(earthquakes)
•Radiatethroughthegroundandtravelgreatdistances
•Createexcessivevibrationsthatcausebuildingstocollapse,leadingto
infrastructuraldamageandlossoflife
VIBRATINGBARRIERSFORPROTECTIONOFCITIES
•Structure-soilinteraction(SSI)andstructure-soil-structure(SSSI)govern
functionalityofViBa
•Theseprocessesinvolvetheinteractionbetweenthegroundandvarious
buildingsduetoseismicactivity
•ViBaisdesignedtominimizetheseinteractions,reducingmagnitudeof
vibrationstransferredintoinfrastructure
DesignandImplementation
Components
•Spring-likeoscillatorto
absorbshockwaves
•Massiveanchoring
foundationmadefrom
recycledwastematerialor
excavatedsoil
Placement
•Buriedbelowground
•Locatedincloseproximity
butdetachedfrom
buildingsratherthanbeing
integratedintofoundation
Function
•Incidentvibrationsfromearthquakescauseoscillatortomovebackandforth
•Thismovement,anchoredbythefirmfoundation,absorbsanddisperses
energyfromseismicwavespriortoimpactingbuildings
•Greatlyreducesmagnitudeoftremorsexperiencedbyprotectedstructures
•Capableofsimultaneouslyprotectingmultiplebuildingsratherthanone
individualstructureduetoitsdetacheddesign
TestResultsforViBa
Measuringearthquakemagnitude
•Seismograph
•Measuresamplitudeofseismicwaves
•Producesseismogram(shownbelow)depictingcharacteristicsofwaves
•Richterscale
•Logarithm-basedmeasurementsofmagnitude
•Notaseffectiveformeasuringlarge-magnitudetremors
•MomentMagnitudescale
•Moredetailedassessmentofanearthquake’scharacteristics
•Increasedreliabilityformeasuringlarger-magnitudeearthquakes
•Commonlyusedtoday
Ü1 ishorizontalaccelerationofastructureasa
functionoftime,where“coupledsystem”
incorporatesViBa
FurtherBenefits
StudiesoftheViBasystemusing
aluminumandacrylicprototype
modelsinashake-tablesimulation
haveshownitseffectivenessfor
earthquakedefense.Whenabase
motionofcircularfrequency22.62
rad/s(simulatedseismicactivity)was
applied,thestructurenotprotected
byViBaexperiencedahorizontal
accelerationofapproximately20m/s2
(overtwicetheaccelerationdueto
earth’sgravitationalfield).Incontrast,
thestructurewhichwascoupledwith
theViBasystemexperienced,after3
seconds,anaccelerationofabout3
m/s2.TheViBasystemcanreduce
horizontalaccelerationbyupto87%.
•ViBareduceschronicdamageonstructurescausedbyregularhumanactivities
suchasmining,transportation,andmanufacturing
•Thedevice’sfoundationcanbeproducedfromwastematerialsorexcavatedsoil
•Minimizesproductionofairandwaterpollutantsthatwouldbegeneratedif
concreteoraless“green”materialwasusedforconstructingthefoundation
Sujay Murthy
Timothy Snyder
COMPARINGVIBRATINGBARRIERSTOPAST
ATTEMPTSATINFRASTRUCTURALPROTECTION
Technology
Advantages
Ductility;flexibility
Steel
(abletobendrather
Reinforcement thanyieldunder
stress)
BaseIsolation
Disadvantages
Lackssufficient
strengthtowithstand
greatforce
Mustbeinstalledin
Minimizeshorizontal originalfoundation;
motionofstructures failstosufficiently
cushionvibrations
Damping
Devices
Attacheddirectlyto
Reducemagnitudeof
structures;vibrations
vibrationtransferred
stilldirectlyaffect
intobuildings
buildings
Vibrating
Barriers
Detachedfrom
buildings;ableto
significantlyreduce
seismicwave
magnitude;capable
ofprotectingnetwork
ofmultiplebuildings
Musthaveextremely
largemassto
withstandforcefrom
earthquakes
THEVERDICTONVIBRATINGBARRIERS
Currently,onlyprototypesofViBahavebeenconstructedortested.While
itisnotafaultlesssolution,itcertainlyhaspotentialtorevolutionizethe
fieldofearthquakeengineering.Furtherdevelopmentofthevibrating
barrierwillrenderitaviablesolutionforearthquakedefense,minimizing
thethreatsimposedbyseismicactivitiesmorethaneverbefore.Basedon
recentanalysisoftestingandresearchdoneonthissystem,ViBa
technologywillgreatlysimplifytheprocessofprotectingcitiesagainst
futureearthquakesandotherseismicevents,withoutsacrificingutility,
sustainability,andperformance.