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Monitoring Structural Response to Earthquakes using Wireless Sensor Networks

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Title: Monitoring Structural Response to Earthquakes using Wireless Sensor Networks


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 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

5
CUREE 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

6
Retrofit 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
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 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 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 ApplicationsLiquefaction
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
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