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This 'Living Bridge' Has a Lot to Say

With a network of sensors, New Hampshire's Memorial Bridge will constantly report back on its structural performance and the marine ecology below it.

The Memorial Bridge in Portsmouth, New Hampshire will soon be equipped with dozen (Keith Burgie/Flickr)

If bridges could talk, what would they say?

Given the right tools, civil engineer Erin Bell thinks they can spout off a trove of valuable information, with one bridge alone capable of revealing daily traffic patterns, the effects of weather and stress, as well as the structure’s impact on the environment.

This isn’t some science fiction fantasy, but a project that Bell and her team at University of New Hampshire have been working on since 2013. With $1.2 million in federal funding from the National Science Foundation and the New Hampshire Department of Transportation, they are turning the new Memorial Bridge between Portsmouth, New Hampshire, and Kittery, Maine, into a “living bridge.” They will outfit the bridge with a network of 40 sensors that monitor structural performance over time, while another 15 will track the marine ecology below. A turbine system will convert the tides into electricity to power the entire operation, making it a self-sustaining endeavor.

Bell and her team haven’t installed all the sensors yet, but they’ve done shorter-term tests at various points in the research process. She says the sensors should be fully installed and operational by mid-December. For the first six to nine months, they will be powered by the state’s electrical grid while the marine science team studies the ecological impact of placing a roughly 10-foot by 7-foot tidal turbine system in the water.

The team is testing a scaled model of the tidal turbine system that will be installed on the Memorial Bridge. (Courtesy of Erin Bell)

The data collected will eventually be available to researchers, urban planners, and to the public. It’ll answer questions like, “What happens to the bridge when the middle span lifts, what kind of vibrations do you see?” says Bell, referring to the section of the bridge that opens up to let commercial ships pass by. “Just things to really put some data on the structural phenomenon and hopefully excite that sense of inquiry [from] citizen scientists.”

It’s a far more ambitious project than Bell initially envisioned. When officials announced the closure and replacement of the 1922 Memorial Bridge in 2012, she and her team had only wanted to temporarily test a tidal turbine system in the estuary. But DOT had bigger ideas. “Unbeknownst to us, there was this other movement for [the new] bridge to add bike paths and pedestrian walkways,” Bell says. “So there was this whole community sustainability aspect to it.“

Meeting with various federal and local agencies, designers, and engineers, Bell figured out what they could learn from the new structure, which wasn’t designed like traditional bridges. I ask Bell to name a few examples, and already, the list is exhaustive: At the top of the bridge tower is a weather station to help operators decide when to close the bridges. An array of accelerators measure vibrations due to winds and lift operations. Gauges on the horizontal span measure the stress load on the bridge connection and create a database of information for future engineers considering a similar design. Then there are sensors and webcams monitoring vehicular and foot traffic. Under the bridge is another weather station that will feed information about temperature, water depth, and tidal heights to organizations like NOAA and the Coastal Adaptation Workgroup.

The new Memorial Bridge is designed with more slender towers and without the use of gusset plates. (Courtesy of Erin Bell)

Local science and math teachers are by far the most excited partners of the living bridge project, and they look forward to incorporating real-life data into their lessons. "There's such a push on data-driven STEM education,” Bell says. “And this would be data from a bridge in your backyard.”

Bell says her project is all about showing the potential of America’s future infrastructure. “We want to show that by having this data, you will be able to make better decisions today and 20 years from now,” Bell says. “From under the water side, we wanted to show the renewable energy community, as well as the bridge design community, that there is an opportunity to harden our infrastructure against power outages and extreme weather events.”

The project is the latest to harness the power of data to save America’s crumbling bridges. The federal government has yet to come up with a funding plan to rebuild the nation’s bridge infrastructure on a large scale. But as CityLab previously reported, local governments have started to turn to technology to maintain existing bridges. Sensors generate continuous data that can warn authorities of cracks or other damages before they become irreparable. And at the same time that E-Z passes generate revenue for the sate, they can also help ease traffic during rush hour, limiting the stress that idling cars put on bridges.

Still, with 1 in 10 bridges in urgent need of repair, combined with tragic stories of collapsed bridges that caught national attention but not enough to spur significant infrastructure spending, the future of American bridges appears bleak to some. Bridges, after all, are not the kind of “sexy” topics that politicians throw themselves at.

But Bell says having an arsenal of data could change that, in part by changing public opinion. A project like hers can get people to stop thinking of bridges as only a means of ferrying drivers across the waterways, but also as a learning tool.

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