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Lab-Type Instruments Monitor Health of Structures in Beijing
Systems offer real-time alternative to strain gauges
Charles J. Murray, Senior Technical Editor -- Design News, August 20, 2008
Using a graphical system design platform and programmable automation controllers, engineers have created a real-time system that's being used for monitoring the structural health of buildings at the 2008 Summer Olympics in Beijing.
CGM Engineering Inc., an engineering and systems integration firm that specializes in automation and test, worked with engineers at National Instruments to create the new real-time product, which they say goes beyond traditional strain gauges. Employing the system, engineers can check on the vibrational signatures of buildings and bridges at any given time by reading data off an Internet site.
"It's like taking the heartbeat of a building," says Chris McDonald, vice president and director of engineering for GM Engineering. "If there's a change in the 'heartbeat' then you know you've got an issue."
The systems are designed to aid engineers in conducting structural health research on recently constructed mega-structures in China, including the Beijing National Stadium and National Aquatics Center. The 64-channel and 36-channel structural health monitoring systems each contain multiple CompactRIO controllers that directly connect to accelerometers for vibration measurements and an external GPS receiver for inter-chassis synchronization. Within each chassis, a LabView FPGA Module synchronizes the measurement channels to within ±10 msec of the GPS clock. During operation, LabView acquires the FPGA code, passes data from the FPGAs to a real-time processor, then sends the data to a server, which relays it to the Internet.
Engineers say the structural health monitoring system provides an advantage over traditional methods because it offers more channels and its data is available in real-time on the Internet.
"With the old traditional data loggers, you'd leave it there, wire it up and then come back and pick it up in a month," says David Potter, who works in product strategy in measurements and control for National Instruments. "With this, we take the performance of a lab-based instrument and make it usable on a bridge."
