The long-term operation and management strategy for long-span suspension bridges requires a suite of monitoring tools, starting with bridge structural health monitoring and extending to traffic monitoring and homeland security applications. This project will investigate the status of state-of-the-art technologies needed to improve the overall safety, reliability, availability, and longevity of long-span bridges. The study will include identifying appropriate sensors required for deployment as well as how to adapt a wireless sensor system already-developed in-house for monitoring typical bridges. This work leverages past and ongoing efforts at Clarkson with the New York Department of Transportation (NYSDOT), the Federal Highway Administration (FHWA), the New York State Energy Research and Development Authority (NYSERDA), and the National Science Foundation (NSF).
As a case study, the project will focus on the long-term in-service performance monitoring of the potential fracture of critical cables in Ogdensburg-Prescott International Bridge, a highly traveled suspension bridge connecting the United States and Canada. These non-redundant components require sensitive care and observation to avoid failure of not only the cable but the entire bridge. Currently, only 2 percent of the US bridges are categorized as a suspension bridge (FHWA, 2010), but many on that list are some of the most critical and most traveled bridges such as the Golden Gate Bridge, Manhattan Bridge and George Washington Bridge just to name a few. According to Andrew Smyth, Professor of Civil Engineering and Engineering Mechanics at Columbia University, individual replacement of a main suspension cable can cost in excess of $100 million dollars. With some bridges having approximately 4 cables, this turns into nearly $0.5 billion dollars (Smyth, 2011). Therefore, caring for the infrastructure today with intelligent monitoring techniques can aid in making smart maintenance decisions and reducing expenses due to unforeseen costly repairs in the future.
The Ogdensburg-Prescott International Bridge in a recent biannual inspection by the NYSDOT observed cracks and chips in the paint along with the onset of zinc and iron oxide corrosion (NYSDOT, 2009). Furthermore, the suspenders, while determined to be sound, were noted to have a loss of galvanizing and pitting on the wire ropes. Recommendations were made for an indepth inspection program for the cables and the anchorage assembly for documenting the corrosion and condition on a regular basis.
Accordingly, research will focus on identifying best tools in evaluating the performance and integrity of the main suspension cables. Material degradation due to corrosion and other environmental effects will be monitored using newly installed wireless sensor technology on the cables. These sensors will also be used to detect the fracturing of cables whether by long-term environmental degradation or sudden man-made events. The initial phase of the research will look to determine the appropriate monitoring system for this bridge and extend the development and customize Clarkson’s wireless sensor system for this specific deployment. It is critical to identify what sensing technology including data fusion will be an effective in bridges that are exposed to extreme environmental conditions, including snow, ice, wind, and extremely low temperatures. Therefore it is anticipated that the Ogdensburg-Prescott International Bridge will be used as a test bed for these critical technologies that can be further developed by the partner institution and deployed at national and international scales. Subsequent phases of the research will focus on the optimal deployment and monitoring plan. These phases will include selecting the optimal locations of the sensors which will allow for the best overall description of the cable performance. Sensors are not intrusive components that will not alter the structure or limit the functionality of the bridge. They will be primarily add-on miniaturized wireless devices working on dedicated transmission frequency that will locally transmit to a central unit in compliance with international communication protocols. Upon completion of the sensor installation, data will be gathered for a minimum of an 18 month period to allow for measurements to be taken over a variation of weather conditionals across seasonal climates. This will allow for any extreme temperature effects to be considered in future measurements.
The proposed research will build upon the knowledge gained from previous and ongoing research projects regarding monitoring cable based structural systems. Findings and results will be shared through technical reports, peer reviewed publications as well as presentations at conferences and workshops, thus enabling the transfer of resulting information and technology. These activities will be carried out through the Laboratory for Intelligent Infrastructure and Transportation Technologies at Clarkson University.