Inclinometers in Structural Monitoring

1. Inclinometers in Structural Monitoring CEE 398 KUC Sudhir

2. Introduction • Monitoring • Inclino/ Clino/ Tilt meters Sudhir

3. Inclinometers / Tiltmeters • Where are they used • Types • Reference System used • Gravity - referenced w.r.t gravity • Locally - referenced w.r.t fibers • Principle used • Optical • Mechanical • Electrical • Resistive, Inductive, Capacitive Sudhir

4. Simple Hydraulic Tiltmeter 2 cylinders – same height – connected by a tube – filled with water – difference in water levels indicates the amount of tilt present Separation of the tanks determines the Sensitivity Central connecting tube having the piston is used to change the water level and Calibrate Sudhir

5. Today’s Market … Portable Tiltmeter Tuff Tilt – Uniaxial Tiltmeter Surface Mount Tiltmeter EL Beam Sensor Biaxial Tiltmeter EL Tiltmeter Portable Tiltmeter Sudhir

6. The Process Monitoring using Tiltmeters Data Analysis Software A data Acquisition System e.g. Model 796 Recording Station Sudhir

7. Real Life ExampleLong Term Monitoring of Lutrive Bridge • Twin bridges – Lausanne to Vevey • Bridge Monitoring, 1973 – 1987 • Bridge Retrofit 1998, additional Post tensioning, 13000 kN  30mm uplift. • IBAP of EPFL is involved in Long term monitoring of the bridge. • Hydrostatic system • Inclinometers Sudhir

8. Things to look for in a new Inclinometer ….. • Angular Range (degrees/ radian/ arc seconds) • Scale Factors (degree/volt) • Resolution (degrees) • Repeatability (degrees) • Hysteresis (degrees) • Linearity (% of full span) • Time Constants (sec) • Tilt Output (No. of angles; Voltage range) • Temperature Output (oC / mV) Sudhir

9. Structural Monitoring Stabilization measures, such as grouting. Structures for the effects of tunneling and excavating. Stability of structures in landslide areas. Deflection and deformation of retaining walls. Convergence and other movements in tunnels. Evaluating performance of bridge, beams and dams under loads. Providing early warning of threatening deformations. Applications Sudhir

10. Applications Geotechnical Monitoring • slopes and landslides to detect zones of movement to establish whether movement is constant, accelerating. • diaphragm walls and sheet piles to check that deflections are within design limits, performance is as expected, and that adjacent buildings are not affected by ground movements • the effects of tunneling operations to ensure that adjacent structures are not damaged by ground movements Providing settlement profiles of embankments, foundations and other structures Sudhir

11. Surface Mount TiltmeterModel 711 – 2/ 716 - 2 of Applied Geomechanics • A precision Biaxial Tiltmeter – Can bolt or clamp to any surface • Well suited for areas of heavy traffic or vibration • Internal Electronics of the models drive cable lengths of 1000m • Widely used for structural monitoring, load testing and precision alignment of machinery and antennae Sudhir

12. Tuff Tilt – Uniaxial TiltmeterModel 801 Applied Geomechanics • Gravity referenced - Electrolytic tilt transducer • A economical precision instrument with high dynamic range and long term stability • Applications • Monitoring of Bridges and Structures • Rotary Position of dam gates and other machinery • Antenna Leveling and tracking Sudhir

13. Portable ClinometersModel 800P Portable Tiltmeter of Applied Geomechanics • A economical hand held instrument suited best for measurements at a number of points when continuous monitoring is not required • Comparatively cheaper than other contemporary Inclinometers in the category due to the use of a precision electrolytic transducer as sensing element which converts changes in angular positions to resistance changes • Operation • Tilt plate option • Metrology Option Sudhir

14. Portable ClinometersPortable Tiltmeter of Slope indicator • The system uses a number of tilt plates, a portable Tiltmeter and a readout unit • The portable Tiltmeter uses a force balanced servo – accelerometer to measure inclination. • Operation … • Advantages: • Economical and east to use and install • Accurate - portable Tiltmeter uses the same technology as a digital inclinometer probe Sudhir

15. El Tiltmeter • Ideal for long term monitoring of deflection of structures and performance evaluation under loads • Consists of an electrolytic tilt sensor – a precision bubble level that is sensed electrically as a resistance bridge ; output voltage  tilt of the sensor • Operation … Sudhir

16. EL Beam Sensors • Consists of an electrolytic sensor attached to a rigid metal beam – the sensor is a precision bubble level that is sensed electrically • Operation .. • High Resolution, Installing ease while being robust and cost effective are its advantages Sudhir

17. Little Dipper Model 904 – T of Applied Geomechanics • Low Cost – Analog Output – Biaxial Inclinometers – small scale testing and measurement applications, most of them being in Geotechnical fields. • Liquid filled electrolytic transducer - sensing element • Analog Voltage signal - X tilt, Y tilt and temperature • Cable length varies - 3m to 500m. • High gain version of the instrument - capture an angle range of 10 degrees with an accuracy of 0.005 degrees Sudhir

18. Lutrive Bridges Sudhir

19. Lutrive Bridges Sudhir

20. Evolution of Mid Span deflections of the North Lutrive Bridge since 1973 Sudhir

21. Evolution of Mid Span deflections of the South Lutrive Bridge since 1973 Sudhir

22. Setup Sudhir

23. Typical Output Sudhir