A Guide on Structural Health Monitoring (SHM)

1. AGuideon StructuralHealth Monitoring(SHM)

2. 1 6 STRUCTURAL HEALTH MONITORING OFBRIDGES INTRODUCTION 2 7 WHAT IS MEANT BY STRUCTURAL HEALTHMONITORING? STRUCTURAL HEALTH MONITORING OFTUNNELS TABLEOF CONTENT 3 8 WHY IS GEOTECHNICAL MONITORINGIMPORTANT? STRUCTURAL HEALTH MONITORING OFDAMS 4 9 ADVANTAGES OF STRUCTURAL HEALTHMONITORING STRUCTURAL HEALTH MONITORING OFBUILDINGS 5 10 HOW DOES STRUCTURAL HEALTH MONITORINGWORK? STRUCTURAL HEALTH MONITORING OF NUCLEAR POWERPLANTS

3. INTRODUCTION Withtechnologicaladvancementsinthefieldofcivilengineeringandgeotechnical engineering,themagnificentstructureslikeBurjKhalifaandGotthardBaseTunnel have been madepossible. Humanshavebuiltlargestructureslikedams,tunnels,skyscrapers,powerplants etc. to make their lifeeasier. Butevenaminorfailureinthesestructurescancauselossofpropertyaswellas humanlife.Hence,regularstructuralhealthmonitoringisamust. Let'sdiscussmoreonstructuralhealthmonitoring,geotechnicalinstrumentation, andhowitmakestheworldasaferplacetolive. 1

4. WHATISMEANTBYSTRUCTURALHEALTHMONITORING? Structuralhealthmonitoringisvitaltoavoidsuddenfailuresandaccidents. Beforeproceedingwithanyconstructionactivity,it'snecessarytocarryoutthe monitoringoftheconstructionsiteaswellasthenearbyassets. 2

5. WHATISMEANTBYSTRUCTURALHEALTHMONITORING? Geotechnicalinstrumentationandmonitoringsupplyquantitativedataonthestruc- ture'sperformancetoaidinevaluatingitssafetyanddetectingproblemsatanearly stage. Structurescanfailduetoseveralreasonslikedesign error,geologicalinstability, poormaintenance,deteriorationofconstructionmaterial,etc. Structuralhealthmonitoringisaprocesstokeepaneyeonallthestructuresand generate early warnings to avoidmishaps. Encardio-riteisgeotechnicalinstrumentationandmonitoringcompanythatprovides variousmonitoringservicesalongwithstate-of-the-artgeotechnicalinstruments. 2

6. WHY ISGEOTECHNICAL MONITORING IMPORTANT? Siteinvestigation Siteinvestigationiscrucialbeforecarryingoutanyconstructionactivity. 3

7. WHY ISGEOTECHNICAL MONITORING IMPORTANT? Itisimportanttocheckifthelandisstrongenoughtobearthestructure.Apartfrom this, it's essential to check for the safety of other assets in the vicinity of the con- structionland. SeveralgeotechnicalInstrumentsareusedtocharacterizeanddetermineinitialsite conditions. Themostcommonparametersofinterestinasiteinvestigationareporepressure, thepermeabilityofthesoil,slopestabilityetc. 3

8. WHY ISGEOTECHNICAL MONITORING IMPORTANT? Designverification It'squiteimportanttoverifythedesignofthestructure.Improperdesigningmay lead to itsfailure. 3

9. WHY ISGEOTECHNICAL MONITORING IMPORTANT? Geotechnical instruments are used to verify design assumptions. Instrumentation datafromtheinitialstageofaprojectmayshowtheneedorprovidetheopportunity tomodifythedesigninlaterstages. Forexample,dataobtainedfromreinforcementbarstrainmetersinstalledbyEncar- dio-riteatTeestaBarrageintheleftembankmentledtheprojectauthoritiestorevise theirestimatesoftherequirementofsteelintherightembankment. 3

10. WHY ISGEOTECHNICAL MONITORING IMPORTANT? Constructioncontrol Structuralmonitoringisnecessarytohelptheengineerindetermininghowfastcon- struction can proceed without adverse effects on the foundation soil and construc- tion materialsused. 3

11. WHY ISGEOTECHNICAL MONITORING IMPORTANT? Theinstrumentsareinstalledtomonitortheeffectsofconstruction. Forexample,thetemperatureriseinconcreteduetotheheatofhydrationwasmoni- tored at Sardar Sarovar Dam on the Narmada River with Encardio-rite’s temperature meterstodeterminethepouringtemperatureofmassconcrete. Bymixingiceflakes,thetemperatureoftheconcretetobepouredwasbrought down to around15°C. Thisresultedinthetemperatureofthesettingconcretenotexceedingthecritical 29°C,asspecifiedandrequiredbytheCentralWaterandPowerResearchStation (CWPRS),Pune. 3

12. WHY ISGEOTECHNICAL MONITORING IMPORTANT? Safety Instrumentscanprovideearlywarningofimpendingfailure. 3 Safety monitoring requires quick retrieval, processing, and presentationof instrumentdatasothatanalysesanddecisionscanbemadepromptly. Aneffectiveactionplanforimplementingcorrectivemeasurescanthenbe prepared.

13. ADVANTAGES OF STRUCTURAL HEALTHMONITORING Structuralhealthmonitoring(SHM)iscriticalbecause: • Itcanprovideearlywarningtotheconcernedauthoritiessothattheycantake actions well before anycasualties. • Itkeepsaregularcheckonthehealthofstructuressothatsuddenfailurescanbe avoided. • It safeguards human life as well as the loss of property. Italsoprotectsthesurroundingstructuresinthevicinity. Itincreasesthelifespanofthestructures. • Itreducesthelong-termandshort-termcostsrelatedtostructuralmaintenance. Itmonitorstheperformanceforsafetyduringthelifeofthestructure. • Itevaluatestheeffectoftheoperationofthestructureonparameterslikestress, strain, water, pressure, inclination, deflection and waterseepage. • Itcomparestheobserveddatawithdesignassumptions. • Ithelpswiththedatatoplanandschedulepredictiveandpreventivemaintenance programs for thestructure. • 4 • • • • • • • •

14. ADVANTAGES OF STRUCTURAL HEALTHMONITORING • Itprovidesdatatodeterminetheeffectsofnaturalcalamitiessuchasearthquake, flooding etc. on thestructure. • Compilationoflong-termandreliabledataonthevariouselementsoftheplant especially foundations, anchoring systems and containmentstructures. • 4

15. HOW DOES STRUCTURAL HEALTHMONITORING WORK? Structural health monitoring requires several geotechnical instrumentsinstallation. The instruments like strain gauges, piezometers, tilt meters, temperature sensors, pressure cells, load cells etc. measure the crucial parameters affecting the struc- tures. Theseinstrumentsareinstalledondams,tunnels,nuclearpowerplants,buildings, monuments to measure the importantparameters. Themeasureddataisloggedinreal-timethroughdataloggersanddisplayedviaa PC/laptop/mobile device at any remotelocation. Thedataloggersarecapableofgeneratingearlywarningssuchthattheconcerned person can take actionsaccordingly. 5

16. 6 STRUCTURAL HEALTH MONITORING OFBRIDGES Therearenumerousrailandroadbridgesbuiltacrosstheglobe.Theyareanessen- tial component of transportation networks and, hence, structural health monitoring of bridges iscrucial.

17. STRUCTURAL HEALTH MONITORING OFBRIDGES Anydamageorcollapseofbridgesduetotheirdeterioratingperformancedisrupts transportationsystemsandmayresultinthelossoflifeaswellasproperty. Therailwaybridgesarewelldocumentedandhavealaiddownsystemforchecking andmaintenance. Bridges must function safely at all times. A large number of bridges are quite old andnotdesignedfortheheavierandfaster-movingvehicularloadsthattheyarecur- rently subjectedto. 6

18. STRUCTURAL HEALTH MONITORING OFBRIDGES Online cloud-based web data monitoringservice Encardio-riteofferspubliccloud-basedonlinewebdatamonitoringservicesforthe safety ofexisting rail and road bridges. The heart of the online structural monitoring instrumentation system is a web data monitoringservice(WDMS)offeredbyEncardio-rite.Theserviceformsanimportant part of the Bridge ManagementSystem. Itisaweb-baseddata-managementandpresentationtoolforretrievingdatafrom thesensorsthroughEncardio-riterangeofautomaticdataloggers. WDMSconsistsofDrishti,datamanagementsoftwarethatactsasadatacollection agent, a database server and a web server hosted on a high-reliability server computer. 6

19. STRUCTURAL HEALTH MONITORING OFBRIDGES Thehostcomputerperiodicallycollectsdatafromtheremotedataloggerovercell phonenetworks. Usersinteractwiththesoftwareusingtheirweb-browserwhenconnectedtothe Internet. Theonlyrequirementisthatthedataloggersiteiscoveredbyacellphoneservice provider who can provide reliable GSM/GPRS enabled cellular data connection locally. Multiple authorized users at different locations assigned with an individual passwordareallowedtoviewanydataorreportfromthestructuresimultaneously. Graphs&reportscanbeviewedusingpopularwebbrowserslikeMicrosoftinternet explorer or Mozilla Firefox amongstothers. 6

20. STRUCTURAL HEALTH MONITORING OFBRIDGES Detailslikesensoridentificationtag,lastrecordedsensorreadingandvaluesofpro- grammedalertlevelscanbeviewedonthefirstpageofthesitethatshowstheloca- tion ofinstallation. Ifanyoneofthealarmlevelexceeds,thesensorlocationturnstoareddot. Clickingthepop-uptablebringsupanassociateddatawindowwherethesensor datacanbeseeneitherasatableorasagraph. Siteadministratorscansetalarmlimitswhicharegenerallyconsideredas“alert level” and “actionlevel”. WDMScanalsobeprogrammedtosendSMSalertmessagesore-mailtoselected users as soon as any sensor data crosses its predefined alarm levels, either while goingaboveorgoingbelowthealarmlevel. 6

21. STRUCTURAL HEALTH MONITORING OFBRIDGES Bridge Monitoring InstrumentationScheme Therearetwotypesofinstrumentationschemestomonitorthehealthofthe bridges. 6 Thefigureaboveshowsonlinewebbasedmonitoringofsurfaceparametersliketilt, crack,load,strain,vibrationsandsubsurfaceparameterslikelateralmovement,set- tlement and piezometricpressure.

22. STRUCTURAL HEALTH MONITORING OFBRIDGES 6 Theabovefigureshowsonlinewebbasedmonitoringoflateralmovementand settlementusingrobotictotalstationsandprismtargets.

23. STRUCTURAL HEALTH MONITORING OFBRIDGES The picture on the left is a typical installation of a robotic total station installed to automaticallygatherdatafromprismtargetsinstalledonthestructureofabridge. Thepictureinthemiddleisthatofaminiprismtarget. The figure on the right shows points at which prism targets may be installed on a typicalbridge.Morethanonerobotictotalstationmayberequiredforpropermoni- toring of astructure. 6

24. STRUCTURAL HEALTH MONITORING OFBRIDGES Screenshotsofsomesamplelongtermmonitoringdata 6 Thefigureaboveshowsstructuralcrackmonitoringoveraperiodofoneyearusing Encardio-rite Model EDJ-40V crackmeter. Crackopeningisinblueandvariationintemperatureisinred.Theinitialopeningof thecrackgaugewassetat5.12mm

25. STRUCTURAL HEALTH MONITORING OFBRIDGES 6 TheaboveimageshowsthestructuraltiltmonitoringofthebridgefromSeptember 12,2015toDecember8,2016usingEncardio-riteModelEAN-92Mbiaxialtiltmeter. Tiltvariationinthetwodirectionsisshownbytheblueandblacklines.Themaxi- mumchangeintiltrecordingduringthisperiodis0.04deg. Thetwohorizontalredlinesatthetopandbottomarethealarmlimitssetat±0.1 deg.Theredlinegivesthetemperaturevariationduringthisperiod.

26. STRUCTURAL HEALTH MONITORING OFBRIDGES 6 Theaboveimageshowsmonitoringofgroundwaterlevelalongwithdailyrainfallfor a period of fiveyears.

27. STRUCTURAL HEALTH MONITORING OFBRIDGES Piezometricpressureisinblueanddailyrainfallisinpurple.Maximumrainfallre- cordedonanydayduringthisperiodis157mm. Groundwatertablevariationduringthisperiodhasbeenbetween34and43mof watercolumn. Sensors used are Encardio-rite piezometer Model EPP-30V andRain Gauge model ERG-200 tipping buckettype. 6

28. 7 STRUCTURAL HEALTH MONITORING OFTUNNELS Encardio-riteoffersacomprehensiveweb-basedmonitoringsolutionforthe long-term safety monitoring oftunnels.

29. STRUCTURAL HEALTH MONITORING OFTUNNELS Itmanufacturesawiderangeofsensorswhichhaveaproventrackrecordforreli- ability and long-term performance under harshconditions. Italsooffersadvancedmonitoringtechnologiessuchasautomatic3Ddeformation monitoring using ATS, laser scanning and aerial survey using drones for keeping a tabonthestructuralhealthoftunnelsandappurtenantstructures. Structural monitoring solution fortunnels WDMS –Web-based Data Monitoring Solution Web-based data monitoring solution for any type of tunnel construction such as NATM, TBM tunnelling, cut & cover, micro-TBM/pipe jacking, etc. essentiallycom- prises of thefollowing: 7

30. STRUCTURAL HEALTH MONITORING OFTUNNELS • ModelEAN-52Mverticalin-placeinclinometersystemwithseveralbiaxialprobes withSDI-12 output mounted vertically in a borehole. • Theseareconnectedinadaisychainmannerwithasingleoutputcablefor continuously monitoring sub-surface lateralmovements. • ModelEPP-30VvibratingwirepiezometerwithmodelESVI-01-01orESVI-10VB SDI12 interface box formonitoring pore pressure variations. • Model EDS-70V vibrating wire type multiple point borehole extensometer (with ESVI-01-04SDI-12interfacebox)formonitoringsub-surfacesettlementandlateral movement at specifieddepths. • Model EAN-92M-BorEAN-93M-BbiaxialtiltmeterwithSDI-12outputmountedat one or more locations on the structures within the zone of influence to record changes intilt. • ModelEDJ-40V vibratingwirecrackmeter(withESVI-01-01SDI-12interfacebox)for monitoringdisplacement/openingofexistingcracksinstructureswithinthezoneof influence. • 7 • • •

31. STRUCTURAL HEALTH MONITORING OFTUNNELS • ModelELC-30S/ELC-30SHresistivestraingagetypecentreholeloadcell(withES BI-10SDI-12interfacebox)formonitoringtensioninanchorsandrockbolts. • ModelESC-30VvibratingwireshotcretepressurecellormodelEPS-30Vvibrating wireconcretepressurecell(withESVI-01-01SDI-12interfacebox)formonitoring radialandtangentialstressinshotcreteliningorconcretepre-castsegments. • Model EDS-20V-E/EDS-20V-AW vibrating wire strain gauges (withESVI-01-01 SDI12 interface box) for monitoring strains in tunnel linings and concrete pre-cast segments. • ModelEBS-16buildingsettlementpointsformonitoringsettlementofstructures using a digitallevel. • Model ESMP-10C2orEPS-12-60surfacesettlementpointsformonitoring settlement of ground above thetunnel. • Encardio-riteModel EAN-26-MV manualinclinometersystemcomprisingofa bi-axial digital inclinometer probe, operating cable on a reel with Bluetooth transceiverandasmartphonedataloggerwithinclinometerapplication • • 7 • • •

32. STRUCTURAL HEALTH MONITORING OFTUNNELS • These could be single & multichannel. RF Gateways with integrated GSM/GPRS modemforenablingcable-freewirelesstransmissionofdata.Refertothefigure below showing installed sensors in a typical tunnel section with RF data transmission. • Encardio-riteModelESDL-30dataloggerfortheSDI-12outputsensors,withintegral GSM/GPRS for wireless datatransmission. • Encardio-rite Online Web Data Monitoring Service (WDMS) that providesdataaccess (with alarms) to authorized users at different geographical locations, on their computer/laptops. • 7 •

33. STRUCTURAL HEALTH MONITORING OFTUNNELS LaserScanning Laserscanningisanadvancedmethodofsurveyingandconductinggeometricdoc- umentation of buildings, architectural and archaeological monuments, engineering projects or other construction works and objects which require a high degree of analysis,aredifficulttoreachorgainaccessto,orarenottobetouched. 7

34. STRUCTURAL HEALTH MONITORING OFTUNNELS Recentdevelopments,especiallyinthesoftware,havemadeitaveryconvenientand cost-effectivetooltoaccuratelymonitorstructuraldeformationsin3D. Accuracyofupto2-3mmispossibleusingthemethod. Duetothelighternatureofthenewsoftware,ittakessignificantlylessertimetopro- cesstheresultsandmakethesameavailableonline,almostinreal-time. It is based on exceptionally dense mapping of 3D coordinates of the points on the surfacethatistobesurveyed,takenatspeedsrangingfromafewthousanduptoa million points persecond. Dependingontheobject(size,shape,desiredaccuracy),laserscanningmaybeair- borneorterrestrial,staticormobile,autonomousorincombinationwithotherstan- dard topographicmethods. 7

35. STRUCTURAL HEALTH MONITORING OFTUNNELS Completionofthefieldworkresultsinageo-referencedpointcloudwhich,duetoits great density and its ability to bear information on the reflectivity and/or the colour ofeachpoint,comesclosetotheterm,“virtualreality”. Depending on the case and on the user’s needs, horizontal, vertical or diagonal sec- tions, aspects, images, videos, ortho-photographs, surface expansions, interval curves, 3Dmodels,determinationofdistortionaswellasanumberofotheranalysis derivedfromthescanner’soperationsinthenon-visiblespectrum,canbeproduced. 7

36. STRUCTURAL HEALTH MONITORING OFTUNNELS • The results oflaser scanning give us: • Surveyingofcurrentstateor‘asconstructed’state • Virtual reality creations; Virtual tourvideos • Geometric documentation of thestructure • Quantitativecalculation • Inspectionoffreepassagespace–determinationofbottlenecks • Creation of 2D & 3D products (sections, facets, 3D models,etc.) • Identification of deformations –discrepancies 7

37. STRUCTURAL HEALTH MONITORING OFTUNNELS Aerial Mapping using Unmanned Aerial Vehicles(UAV/Drone) Inspectionofhugeandcomplexstructuresliketunnelconstructionsitesrequiresa highdegreeofanalysisbutattimesisdifficulttoreachorgainaccessto. 7 UseofUnmannedAerialVehicles(UAV)/Dronesisbestsuitedforsuchapplications. UAVs/Drones are unmanned and remotely-piloted aircraft that follow a pre-pro- grammedpathfortakeoff,flightandlanding.

38. STRUCTURAL HEALTH MONITORING OFTUNNELS TheseaircraftareequippedwithHD/IR/Thermalcamerasthatcomputeaerial imagesandvideosoveradefinedareaataspecifiedheight. Using UAVs/drones to video, model and scan for cracks, erosion, corrosion and defectsinareas,thatwouldotherwiserequiretheinspectortousearope/harnessor erectaccessscaffolding,isasafer,fasterandsmarterchoice. Largesiteswithcomplexstructuresnecessitateaerialphotogrammetryavoiding ex- pensive ground-basedsurveys. Thistechnologyisusefulduringtheconstructionprocessalso-asthedevelopment occurs,managershavedifficultymaintainingatruepictureofthesite. 7

39. STRUCTURAL HEALTH MONITORING OFTUNNELS Automatic 3D deformation monitoringsystem Thereal-time3Ddeformationmonitoringsystemisasystematictrackingofanyal- teration that may take place in the shape or dimension of the tunnel as a result of stress, load, ageing etc. or of any structure located within the zone of influence of the tunnelconstruction. 7 Theabovedeformationmonitoringsystemconsistsofahighaccuracyautomated total stations (ATS) that have the ability of auto-target recognition (without any humaninterference).

40. STRUCTURAL HEALTH MONITORING OFTUNNELS EachATShasadedicatedcontrolboxthatincludesacomputerrunningspecial software. This control box manages the total station and schedules the frequency of the measurements, the addition or subtraction of monitor benchmarks, the filters of acceptance or repetition of each measurement, the atmospheric corrections in distancemeasurements,thecalculationandrepositioningofthetotalstationetc. Thewholesystemcanbecontrolled/re-configuredremotelyafterinstallationatsite. The on-site system transmits the collected raw data to a remote server/computer viaGSM/GPRS. Raw dataisprocessedintomeaningfulresultsandpresentedintheWDMS. ThesystemhasthefacilityofalertnotificationsthroughSMSand(or)e-mailtothe authorizedteamforanyresultexceedingpresentalarmandcriticallevels. 7

41. STRUCTURAL HEALTH MONITORING OFTUNNELS Thesystemprovidesanaccurate,continuous,real-timedata,eliminatinganyhuman error/delay in manualdata. Therawdataisprocessed,analysedandtheresultismajorlyusedforpredictive maintenance, alarming forsafety. 7

42. 7 STRUCTURAL HEALTH MONITORING OFTUNNELS Tunnel Monitoring InstrumentationScheme

43. 8 STRUCTURAL HEALTH MONITORING OFDAMS Dam monitoring instrumentation plays a key role in safety monitoring for dam and people,providingnecessaryinformationontheperformanceofthedamanddetect problems at an early and preventablestage.

44. STRUCTURAL HEALTH MONITORING OFDAMS Theextentandnatureofinstrumentationdependnotonlyonthecomplexityofthe dam and the size of the reservoir but also on the potential for loss of life and propertydownstream. Thisinformationiscriticalforthedam’sownerwhoisdirectlyresponsibleforany consequences of itsfailure. Instrumentation includes different type of sensors used for measuring pore pres- sure,waterflow,lateralmovement,deformation,stress,strainandtemperature,in- stalledinthedamanditsauxiliarystructures. Italsoincludesgeodetictargetsmeasuredusingsurveyingtechniques. 8

45. STRUCTURAL HEALTH MONITORING OFDAMS Monitoring solutions fordam FollowingsolutionsareavailablewithEncardio-riteforonlinemonitoring: • Geotechnicalsensorstomeasureallrelevantparametersrequiredtomonitor different types ofdams • AutomaticmonitoringofgeotechnicalsensorswithSDI-12digitalinterfaceusing SDI-12 data logger with GSM/GPRStelemetry • Automatic monitoring of geotechnical sensors using nodes and gateways Geodeticmonitoringwithautomatictotalstations(ATS)withGSM/GPRStelemetry Laserscanning • Survey by UAVs (unmanned aerial vehicle) ordrones 8 • • • • •

46. STRUCTURAL HEALTH MONITORING OFDAMS 8 Publiccloud-basedwebdatamanagementservice(WDMS)thatprovidesdataonline (with alarms) to authorised users at different locations on their computers/mobile devices.

47. STRUCTURAL HEALTH MONITORING OFDAMS Dam Monitoring InstrumentationScheme ConcreteDam 8

48. STRUCTURAL HEALTH MONITORING OFDAMS 8

49. STRUCTURAL HEALTH MONITORING OFDAMS 8

50. STRUCTURAL HEALTH MONITORING OFDAMS 8