Instrumentación de Puentes Structural Health Monitoring of Bridges
Agenda! Some examples! Focus on Rion Antirion System! General architecture of Structural Health Monitoring System! Data management & long term storage system! Data acquisition & temporary storage system! Sensors for characterization of effects vs loads! Sensors for monitoring of ageing
SOME EXAMPLES
Russky Island Bridge! Unique signature bridge! Worldwide longest cable stayed span! 1104m main span! Very aggressive environment! Monitoring is a key tool to evaluate real bridge behavior and confirm design hypothesis
Normandie Bridge Accelerometers on stay! Long span cable stayed bridge! 2141m long, 854m main span Load cell! Built in 1995! Worldwide longest at the time Acoustic sensors Uscan Survey! Complementary monitoring installed after 20 years! Focus on bridge ageing and durability " Acoustic monitoring of stay cables " US inspection of anchorages Expansion joint movements sensors Weather station Tiltmeters Deck temperature sensor Water presence sensor
Grande Ravine Viaduct! Construction monitoring! Check geometry in real time! Adjust tension in cables as needed Load cell Tiltmeters Long base extensometers! Operation monitoring! Monitor wind loads! Monitor bridge response during wind events Structural accelerometers (1D, 2D, 3D) Tri axial anemometer Indoor and outdoor temperature sensors Differential air pressure sensors
Astana Arch Bridge Strain gages! Monitoring during load test! Static! Dynamic! Design check before bridge opening Tension in stay (Vibration method)
Penang Bridge Acoustic sensors! Underestimation of fatigue loads at construction stage! Crack in stay detected during maintenance works! Preventive acoustic monitoring of all stays
ASF Highway viaduct Acoustic sensors! Local corrosion found in some cables! Extend of the problem is not known! Acoustic monitoring is placed on all beams! External posttensioning is added! Post tensioning can be adjusted if progress of deterioration is detected
Bosporus Bridges 1 & 2 Cable clamps (UPUS measurement) Differential GPS! Traffic load more important than expected! Risk of fatigue on some critical steel components! Temporary monitoring for assessment of actual condition of the two bridges Hanger force transducers (with invar mechanics) Tiltmeters Deck & Pylon Expansion joint movements sensors! Permanent monitoring left in place on B1! Continuous monitoring of fatigue! Automatic alarm in case of storm or earthquakes Tri axial anemometer Weather station Dynamic strain gages (1, 21 3D) (stools, hanger pin, cable clamps) Structural accelerometers (deck, pylon, hanger) Structural temperature (deck, pylon, hanger, main cable)
Frontera Weight in Motion sensor Tri axial anemometer, weather station and structural temperature Tiltmeters! Instrumentation installed during retrofitting of piers in 2013 Structural accelerometers (1D, 2D, 3D)! Monitoring of traffic loads Camera! Weight in motion sensors! Deck strain! Monitoring of piers / scouring effect! Water level and speed! Pier tilting and natural frequencies Expansion joint movements sensors Strain gages Water speed & level
FOCUS ON RION ANTIRION EXAMPLE
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Rion-Antirion environment & design loads Design Loads: " Earthquake with a return period of 2000 yrs or 5% possibility of exceedance in 120 yrs (operational life) " Tectonic movements of 2m in all directions between adjacent piers " Wind speeds up to 266km/h " Ship collision of 180000t DWT approaching at a speed of 16 knots RΙΟN PROJECT BRIEF DESCRIPTION# RION-ANTIRION ENVIRONMENT & DESIGN LOADS 65 m. ΑΝΤΙRΙΟN 14
Definition of the system Severity General surveillance : visual, ndt, post incident = Inspection & Maintenance Manual 1 2 3 Likelihood Structural Risk Analysis Continuous monitoring: when visual inspection is not sufficient (no detection, not enough reactivity or too expensive) 15
Structural Monitoring System! ~ 300 sensors! Real Time Information, up to 500 Hz per channel! Fully customizable system! Specified during design! Installed to follow construction! Used to manage operation! Maintenance Management " Detection of defects " Control of maintenance actions! Traffic management! Design calculations " Identification of real load cases " Validation of models 16
Monitoring strategy & thresholds defined with design/construction team EARTHQUAKE! Automatic event detection Automatic modification of acquisition parameters Automatic Data treatment and classification of earthquakes in 3 cases (small, moderate, strong) Automatic Report, Mail and Phone Call 17
Accelerometer (Pylon Head) Sensors for earthquake detection and characterization Sensors for earthquake case determination (structural response) Load Cells (Stay Cables) Accelerometers (Stay Cables) Sensors for long term management and operation Meteo Station (deck) Strain gages (gussets) Force in transverse retaining device Temperature (pavement) Expansion joint movement Accelerometers (deck) Accelerometer (Pier Base) Water presence (Pier Base) Accelerometer (Shore)
GENERAL ARCHITECTURE OF STRUCTURAL HEALTH MONITORING SYSTEM
System Overview Sensors Static Sensors Dynamic Sensors Network of digitizers Static DAUs Dynamic DAUs Data Acquisition and Temporary Storage System TDSS Server Temporary Data Storage System Local access Basic visualization & analysis Optical Sensors Optical DAUs Raw, processed, historical, event & condition data Weigh Sensor DWIMS DAU Alert GPS receivers GPS DAU Data Management and Long Term Storage System Data visualization, post processing, analysis and report generation Mobile Sensors Portable DAUs LTSS Server Long Term Data Storage System Raw, processed, historical, event, condition data & alert data Cloud access
What do we expect from the SHM System? To calibrate models To monitor ageing To asses real behaviour To take relevant decision To detect hidden defects
Web platform for long term data management Decision is taken from Inventory data + visual inspection data + maintenance history + other constrain Data & alert indicators shall be integrated to the Bridge Management System and available to all stakeholders
Acquisition frequency shall be adapted to each case Periodic visual inspection Periodic measurement Continuous Monitoring Main surveillance method When relevant information is not visible (ex: stress; hidden defect) When loads and effects shall be recorded at slow time steps (say > 1/month) When measurement cannot be periodic (ex: acoustic monitoring) When quick reaction is needed (earthquake; lack of redundancy) When loads and effects shall be recorded at faster time steps (say < 1/ month)
Example of portable DAUs for periodic measurement Vibration measurement of cables Load test Tension measurement in bars Stress measurement in concrete
Wireless sensor network Four channels wireless nodes with solar panel! Quick deployment! Local communication by radio! Remote communication by GSM! Up to 5 years autonomy One channel battery powered wireless nodes
Wired DAU! For complex situations as for example long term dynamic systems! Customized on demand! Integrating different sensor technologies (analog, vibrating wire, optical, )! Integrating watchdogs for optimization of uptime! Integrating NF EN 61643-21 lightning protection! Integration real time data analysis!
Use of SHM System! Data will be used to calibrate models! Simultaneous measurement of loads and effect of loads (displacement, strain, force)! Experimental modal analysis (identification of Eigen modes)! Hidden defects will be identified by! Dedicated sensors / abnormal values! Changes in load vs effect relationship! Thresholds shall be defined with engineering team
Acquisition & alert strategy 15 10 5 Raw/Processed data: not recorded Example: strain/temperature 4 3 2 1 History data: (ex: average, max, min, std, ) Calculated statistics over a period 0-5 0 50 100 150 200 0-1 -2 0 50 100 150 200-10 -3 15 Event data: Short record of raw/calculated data 10 threshold 5 0 0 50 100 150 200-5 -10! Raw data is processed continuously! Filtering! Scaling! Calculated channels! Only relevant information is recorded! Event data! History data
Monitoring of loads 2D & 3D anemometer & weather station (Temperature, air pressure, relative humidity, sun, rainfall) Water level & speed Weigth In Motion (WIM) Seismic Accelerometer Accelerometer for shock detection
Monitoring of strain & displacement Weldable strain gages Embedded strain gages 1D & 3D crackmeter Long base (20cm) displacement sensor Long base (1m) invar displacement sensor Wire displacement sensor
Monitoring of movements Accelerometers on stay Accelerometer on deck Tiltmeter Differential GPS Total station Crack propagation sensor
Monitoring of stress & force Load cell Electromagnetic sensors UPUS measurement for bars SlotStress measurement for concrete
Monitoring of hidden defects! Acoustic monitoring! Grid of sensors is glued on the area to monitor! Detects sound released during a break! Events are located by triangulation
Monitoring of hidden defects! Continuous strain sensors! Strain increase at crack level! Cracks are detected before they are visible! Can be used to detect early sign of deterioration is concrete structures
Monitoring of corrosion or fatigue risk Corrosion ladders: monitoring of corrosion potential and current Dynamic strain/force sensors for fatigue monitoring Single steel anodes at different depths for the monitoring of the timedependent chloride ingress or carbonation progress into the concrete Rainflow algorithm for fatigue monitoring (load cycle counting)
Monitoring of corrosion or fatigue effect Escan: detection of voids and white paste Uscan: detection of corroded or broken wires Example of white paste in external post tensioning duct Example of corroded strand with broken wires
Conclusion! Structural Health Monitoring is very efficient tool complementary to periodic visual inspections! For maximum efficiency, It should be designed with the engineering team! It can be tuned to any structure! And will provide data helping managers and engineers in managing their building assets
Thank you for your attention