SENSORS | ARTICLE
Te US highway system is a prime example of how a valuable asset has been permited to slowly deteriorate to the point where several bridges have collapsed, one of which, the I-35W bridge over the Mississippi River in Minneapolis, Minnesota, resulted in the death of 13 individuals in 2007 (figure 5).
• Major construction of highway roads and bridges constructed during the 1950s to 1970s as part of the interstate highway system
• Many have exceeded their design life expectancy and are still in use
• Local, state and federal agency funding have been limited to support adequate maintenance and repair
• Recent study — Federal National Bridge Inventory — showed that out of 607,380 bridges:
- 65,605 were classified as ‘structurally deficient’ (a bridge is defined as ‘structurally deficient’ when it is in need of rehabilitation or replacement because at least one of its major components of the span has advanced deterioration or other problems that lead inspectors to deem its condition poor or worse)
- 20,808 were classified as ‘fracture critical’ ( a bridge is considered ‘fracture critical’ when it does not have redundant protections and is at risk of collapse if a single, vital component fails)
- 7,795 were classified as both. >> Continued on page 44
To directly address this severe situation, Prof. Jerry Lynch from University of Michigan has instrumented two bridges with sensor nodes to determine the bridges’ structural status under dynamic conditions: the Monroe Michigan Telegraph Road Bridge and the New Carquinez California Bridge. Built in 2003, the New Carquinez Bridge, which is on Route I-80 in Vallejo, (Northern) California, has 31 wireless sensor nodes deployed on the 1056 meter structure. A total of 87 channels of tri-axis accelerometers, strain gages, wind velocity, temperature and potentiometer displacement sensors are measured using his proprietary Narada 4 x 4 inch pc board platorm, which can accept up to four channels of sensor data. Te purpose of the deployment, states Prof. Lynch “was to determine the cost-effective deployment and robustness of the Narada sensor nodes and their remote sensors.” Te system, installed in 2011, is currently collecting data and is supported by the California Department of Transportation (Caltrans). Data taken by the system will be used to validate the models developed by the WIMSS team and will be used to beter understand the response of the bridge under conditions including high wind loading and earthquakes.
Micro Size Ultra Precision
Customized fine ceramic solutions for medical, dental, industrial and electronic markets.
n Ceramic Injection Molding n Net Shape Process n Micro Tolerances n High Strength n Bio-Compatible n Chemically Inert
SPT Roth Ltd
3250 Lyss, Switzerland T +41 32 387 80 80
cim-ch@spt.net
>>
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Small Precision Tools Inc. Petaluma, CA 94954, USA T +1 707 765 4545
cim-usa@spt.net
43 | commercial micro manufacturing international Vol 7 No.6
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