Health Monitoring Aspects of Low Cost Housing

Transcription

1 Workshop on PERFORMANCE EVALUATION OF HOUSING UNITS July 2017 IIT Kanpur, Extension Center, Noida Health Monitoring Aspects of Low Cost Housing Debasish Jana Dr. Suparno Mukhopadhyay

2 International Scenarios of Failure Damage in corbel in the precast joint Failure of precast parking lot structure January 17 th, 1994 Northridge earthquake (California, USA, M W =6.7) 2

3 International Scenarios of Failure Pounding failure of the upper part during seismic activity Failure of corbel due to poor connection design August 17 th, 1999, Kokaeli earthquake (Turkey, M W =7.4) www3.nd.edu/~concrete/1999_duzce_earthquake_reconnaissance/precast 3

4 International Scenarios of Failure Insufficient anchorage in the connections Failure of precast structure due to connection dislocation April 6 th, 2009, Abruzzo earthquake (Italy, M W =6.3) 4

5 What is Structural Health Monitoring (SHM) The process of implementing a damage detection and characterization strategy for engineering structures SHM Involves: Health monitoring Operational Evaluation Data Feature Extraction Statistical Models Development

6 Objective of Structural Health Monitoring Modifications to an existing structure. Monitoring of structures affected by external works. Monitoring during demolition. Novel systems of construction. Assessment of post-earthquake structural integrity.

7 Steps of Structural Health Monitoring Determination of damage existence Determination of damage s geometric location Quantification of damage severity Prediction of remaining life of the structure

8 Need for Structural System Identification

9 Operating under continuously changing environment Wind Induced Vibrations Wind Turbine Pedestrian Vibrations Millennium Bridge

10 How to Do SHM in practice? Visual Inspection It requires a high degree of expertise, Subjective. Non-Destructive Evaluation (NDE) Various technologies for different purposes, Demands a high degree of expertise, May be subjective, Time consuming and costly, Usually requires a priori knowledge of the potentially damaged region, Works only in accessible regions of the structure.

11 NDT Visual Inspection Magnetic Particle Testing Dye Penetration Test Radiography Test

12 NDT Eddy Current Test Ultrasonic Test Acoustic Emission Test Thermal Infrared Test

13 How to Do SHM in practice? Static-Based SHM Based on the premise that damage will alter the static properties of the structure. e.g. displacements, rotations Drawback Considerable static deflection requires large amount of static force

14 How to Do SHM in practice? Vibration-Based SHM Based on the premise that damage will alter the dynamic properties of the structure. e.g. structural response, frequencies, mode shapes, damping or modal strain energy change By measuring the structural response by means of sensors strategically placed on the structure, and intelligently analyzing these measured responses, it is possible to identify damage occurrence. It can be done either in modal domain or physical domain

15 Vibration Based SHM: Sensors Different forms of dynamic structural response: Displacement, Velocity, Acceleration, Strain. Which ones to measure depends on monitoring conditions and objectives. Sensing technology: an ever emerging field of study. Based on what to measure, different sensors available: Laser Displacement Sensors (LDS), Velocity Transducers, Seismometers, Piezoelectric Accelerometers, Strain Gauges. Most of these sensors can be wirelessly connected.

16 Collection of Sensory Information Load Cell (Force) LVDT (Displacement) Strain Gauge (Strain) Accelerometer (Acceleration) Meteo Data from GPS

17 SHM by Structural System Identification Courtesy of Prof. E. Chatzi, ETH

18 Some Barriers in SHM up today Conventional cables High installation costs Vulnerable to ambient signal noise corruption Vulnerable to earthquake conditions Size and complexity of large structures require a large number of sensing points to be installed.

19 Technological Solutions Wireless Sensors Accelerometers/Inclinometers etc Laser Scanning RFIDs (Radio Frequency Identification) Acoustic Emissions MEMS (Micro-Electro-Mechanical Systems) Increase of Computation capabilities Fiber technologies

20 Monitoring Metrics Measure: Identify Acceleration Strain Climatic Conditions Curvature Displacements Load Corrosion Cracking Strength Tension Location of rebar/delaminations Tilt/Slope Scour

21 Smart Sensor concept Earthquake Event Sensors Wake-up (unique IDs) Events Recorded and stored in BS Sensors go back to sleep

22 Future of SHM

23 Worldwide Monitoring Projects

24 Conclusion: Application of SHM in Housing for All Project Occurrence of mild earthquakes are increasing day by day in India. So monitoring of houses are important to reduce the hazard. Proposed Idea: One house will be properly instrumented among the colony of houses. Sensor data will be taken once is a year and the health of that colony can be estimated. Visual inspection and NDTs will be done if any earthquake occur in its lifetime. It will be used to determine the health of retrofitted structures.

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