Structural Health Monitoring using Wireless Sensor Networks - Mobile and Pervasive Computing in Construction - page 210

11 Structural Health Monitoring

using Wireless Sensor
Networks

Jiannong Cao and Xuefeng Liu

11.1 Introduction

Structures such as large dams, long-span cable-supported bridges, high-rise towers,
tunnels and so on are critical components of the economic and industrial
infrastructure. These structures age with years and are also subjected to possible
unexpected severe environmental conditions and harsh loading scenarios. There-
fore, it is important to monitor the integrity of these structures and detect and
pinpoint the locations of any possible damage before it reaches a critical state.
A system that is able to provide such information is called a Structural Health
Monitoring (SHM) system (Doebling et al ., 1996)
To design a SHM system, it is firstly necessary to identify the structural
phenomena to be monitored. Depending on structure types, acting loads, and
environmental conditions, typical structural phenomena include vibration, deflec-
tion and inclination, internal strain, crack, and corrosion. After these phenomena
have been determined, the suitable types, the number and the locations of sensors
to be deployed should then be determined. The commonly selected sensors in SHM
include accelerometers, strain gauges, anemometers, GPS, and temperature sen-
sors. Additionally, appropriate sampling frequency and time strategy, such as long
term, short term, continuous, periodic, or event triggered, should be determined.
Additionally, the algorithms chosen to detect the structural damage, which are
application dependent, should also be carefully considered.
Traditional SHM systems are wire-based and centralized. A network of sensors
distributed throughout a structure is linked through cables to a data acquisition
hub. After all of the sensed data are collected at the data acquisition center,
SHM algorithms are carried out to extract damage-sensitive features and make
corresponding decisions about structural condition (Doebling et al ., 1998).