Title: Monitoring Structural Response to Earthquakes using Wireless Sensor Networks
1Monitoring Structural Response to Earthquakes
using Wireless Sensor Networks
- Judith Mitrani
- June 18, 2002
2Why 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
3Instrumentation for Monitoring
- Accelerometers (acceleration)
- GPS (displacement)
- Rate Gyroscopes (dynamic strain)
- Magnetometer (sensor bearings)
- Barometer (pressure)
- Thermistor (temperature)
4Lessons Learned from 1994 Northridge Earthquake
- Apartment buildings built with tuck-under parking
in the 1960s and the 1970s - 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
5CUREE Wood-Frame Test at Richmond Field Station
- Build large-scale model of a typical late 1960s
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
6Retrofit for Soft-Stories
Close-up of Retrofit Steel Moment Resisting
Frame (mechanism for resisting lateral forces
induced by earthquakes)
3-Story Wood Frame Apartment Building with Finish
Materials
7Why Wireless Motes?
- Easy to Install
- Cheap
- Store Data Onboard
- Expandable Sensor-Board Platform/Flexible
Software - Message Hopping Capabilities
- Remote Communication
8Structural Testing in a Controlled Environment
- Footprint of building is 16W ? 32L ?
27T - 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 First Story Wall
9Scaled 1994 Northridge Earthquake on Wood-Frame
of Apartment Building
10Structural Response to Earthquake
11More Civil Engineering ApplicationsLiquefaction
Experiment in Japan
12Measured Accelerations
13Potential 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)
14Mote Challenges
- Storage
- Communication
- Numerical Computation Capability
- Power
- Reliability (in Japan, 50 of the motes thought
they were there for security reasons) - Time Synchronization