Highway 520 Floating Bridge Instrumentation: Washington State D.O.T.
Challenge
The 520 floating bridge between Seattle and Bellevue Washington was put into service in 1962 and handles heavy traffic flows every day. D.O.T. engineers noticed that cracks had formed in some of the floating concrete pontoons. They commissioned Washington State University's Engineering Department to develop a computer model to determine what stresses were present under storm loading conditions so they could focus upgrade and maintenance efforts to extend the service life of this vital bridge. Measuring stress and strain was fundamental to establishing the validity of the model.
Response
Measurement Technology Northwest created an instrumentation system that provided Washington State University engineers real-time access to bridge stress and strain data. The 40+ sensors - including mooring cable tension meters, bondable strain sensors, and displacement sensors - were mounted to various bridge sections with leads back to 2 data nodes. These data nodes were equipped with spread-spectrum RF modems that in-turn relayed the information back to MTNW's facility. A PC software program that also served as Web host managed the RF transmitted data. University and D.O.T. engineers could access this web site for both logged and current data on a 24/7 basis.
Auto and Passenger Transfer Span Tension Monitoring System: Washington State Ferries
Challenge
Washington State Ferries is the largest ferry system in the United States, serving eight counties within Washington and the Province of British Columbia in Canada. The existing system consists of 10 routes and 20 terminals served by 29 vessels, and it's an essential part of Western Washington's highway network - carrying over 11 million vehicles and 26 million people per year. As part of a safety upgrade to state ferry terminals, WSF engineers wanted to install line tension monitors to the heavily used auto and passenger transfer spans that connect vessel and terminal.
Response
Measurement Technology Northwest developed a dedicated line monitoring system consisting of a modified LCI-100 dual-tension display, one or two 7,000 pound tension links, and interconnect cables. The LCI-100 interfaces with the analog output of the tension links, and provides a visual display of line tension along with the added safety of high/low tension alarm setpoints. This system was designed to be fully autonomous, and it requires only annual calibration checks and visual inspection to ensure continued trouble-free performance.
