Evaluation of Wireless Devices for Monitoring Fracture-Critical Steel Bridges

Highway bridges are vital links in the U.S. transportation network, providing the public with routes for daily commutes and businesses with the infrastructure needed to supply goods and services. Identifying possible safety problems in the approximately 600,000 bridges across the country generally is accomplished through labor-intensive visual inspections. The National Bridge Inspection Program requires that bridges be inspected at least once every 2 years. Pending legislation spurred by the collapse of the I-35W steel truss bridge in Minneapolis, Minnesota, would increase the inspections for fracture-critical bridges to once a year and likely strain department of transportation resources that are already stretched to the limit. This paper outlines ongoing research sponsored by the National Institute of Standards and Technology that seeks to improve inspection practices by providing the technology and methodology for real-time monitoring of steel bridges. The first generation of two wireless systems (one based on IEEE 802.11 and another on IEEE 802.15.4) from National Instruments has been evaluated in field conditions. This paper presents results of a study to characterize wireless communication in steel box girders and I-girders. In addition, enhancements to be made in the second generation are discussed.