1. Monitoring Structural Response to Earthquakes using Wireless Sensor Networks Judith Mitrani June 18, 2002

2. Why is Structural Health Monitoring Important? Measure changes to applied loads Evaluate health due to accumulated damage (weather, age, ambient vibrations, natural disasters, “unnatural” disasters) Evaluate structure after major event (earthquakes, hurricanes, industrial accidents, terrorist attacks) Use measurements to actively or passively control structure

3. Instrumentation for Monitoring Accelerometers (acceleration) GPS (displacement) Rate Gyroscopes (dynamic strain) Magnetometer (sensor bearings) Barometer (pressure) Thermistor (temperature)

4. Lessons Learned from 1994 Northridge Earthquake Apartment buildings built with tuck-under parking in the 1960’s and the 1970’s Configuration creates a soft-story in the ground floor and torsional modes of vibration Important welded connections failed in hundreds of buildings Severe damage and even collapse

5. CUREE Wood-Frame Test at Richmond Field Station Build large-scale model of a typical late 1960’s apartment building with tuck-under parking, using 1964 Uniform Building Code (UBC) Run series of scaled 1994 Northridge and 1999 Izmit Earthquakes Asses the effect of finish materials on structure (exterior stucco, interior gypsum boards, etc.) Test effectiveness of most common retrofit Detect damage to structure using dense array of wireless sensors

6. Retrofit for Soft-Stories 3-Story Wood Frame Apartment Building with Finish Materials Close-up of Retrofit: Steel Moment Resisting Frame (mechanism for resisting lateral forces induced by earthquakes)

7. Why Wireless Motes? Easy to Install Cheap Store Data Onboard Expandable Sensor-Board Platform/Flexible Software Message Hopping Capabilities Remote Communication

8. Structural Testing in a Controlled Environment Footprint of building is 16’W  32’L  27’T Longitudinal side completely open on one side for parking Shaking table (20’  20’) produces 3 translational components of motion Wireless and conventional sensors used Software for sensors by Crossbow Technology, Inc. 25 Motes on Glulam Beam 25 Motes on First Story Wall

9. Scaled 1994 Northridge Earthquake on Wood-Frame of Apartment Building

10. Structural Response to Earthquake

11. More Civil Engineering Applications: Liquefaction Experiment in Japan

12. Measured Accelerations

13. Potential Applications Instrument Golden Gate Bridge Prompt Post-Event Tagging of Structures FEMA Urban Search & Rescue Team On-line Health Monitoring (update dynamic model of structure) Enabling Technology for Self-Repairing Structures (active control)

14. Mote Challenges Storage Communication Numerical Computation Capability Power Reliability (in Japan, 50% of the motes thought they were there for “security” reasons) Time Synchronization