Building Bridges 45 centimeters to 3 miles long
JJHS’ Principles of Engineering class took a field trip to the New NY Bridge in early March to connect what they learned in the classroom to the real world. The visit began in a fourth floor conference room with panoramic views of the bridges and river. It ended at an outside viewing area just north of the old and new bridges, where strong gusts of frigid air blew off the river.
“I can imagine myself working on this bridge,” said one student, “at a desk job.”
Building a bridge was not all craft labor, the students already knew. The project they had just completed was to design and build a bridge forty-five centimeters long, that could hold fifteen kilograms, using only wood and adhesive. Their investigation, force analysis, design, 3D models and stress analysis took the fall semester, while the final build and test were completed in one week.
“Over one million design hours went into the New NY Bridge,” said Dan Marcy, the outreach educator for the New NY Bridge Project.
He began his presentation by discussing the differences between various bridge designs. What the students designed were truss and beam bridges. The current Tappan Zee Bridge uses a cantilever design. The George Washington Bridge is a suspension bridge. The New NY Bridge is a cable-stayed bridge, which means that its towers are the primary load-bearing structures which transmit the bridge loads to the ground.
Construction Compliance Engineer Tom McGuiness stepped into the room. He asked the nineteen students, “Who here wants to be an engineer?” More than half raised their hands.
“When I was a kid, I enjoyed taking things apart and putting them back to together,” said McGuiness. ‘Seeing how things work; looking at their structure and components. That let me here. I’m a civil engineer.”
“Engineering is like the medical world. There are many specialists and we all work together. Materials engineers, environmental engineers, design engineers, structural engineers, construction engineers and more. Figure out what motivates you,” he said. “It’s a diverse field.”
Through time lapse photography and animated designs, Marcy showed the students the phases of construction already done and projections for the project’s completion. McGuiness told them about the pre-construction complexities.
“We had to find a way to build this bridge fast, efficiently, without disrupting travel on the New York State Thruway, and keeping the navigation channel open. Plus, we have a commitment to minimizing noise, air, and water pollution, and protecting endangered species in the river.”
In 2013 the team began studying the soil conditions in the riverbed north of the old bridge, along the route of the new one. The test borings found soil, sand, silt, clay, glacial till, and, seventy percent of the time, bedrock. “The soil here is what we professionals call ‘tapioca pudding,’” said McGuiness.
The results were given to designers who drafted an initial foundation plan. To optimize the design and location of some 1,000 steel piles, the team conducted extensive tests which included filling barges with water and placing them on top of test piles. “Math proves it can work but then we do a scaled load with scaled weight and validate how much the deck moves,” said McGuiness.
“We relied on tests done on other projects, and we did a lot of off-site testing behind the scenes, such as extensive wind tunnel testing. A prototype of the bridge was tested in a specially constructed wind tunnel in Canada,” said McGuiness.
“A lot of people around the world are watching this bridge,” said McGuiness, “because we’re using new types of engineering and new materials.” Innovations include the bridge’s modular construction—the eye beams were assembled near Albany, the deck panels were prefabricated in western Massachusetts, and the crossbeams were built in Virginia—and two floating concrete plants.
Tappan Zee Constructors, the consortium that won the contract for the New NY Bridge, is New York State’s first design-build contract, meaning that one entity is responsible for a unified flow of work from initial concept through completion. “Tappan Zee Constructors’ bid, at $3.1 billion, was almost $1 billion lower than those of its two competitors,” said McGuiness. “We did not chose the lowest bidder for this project. We chose the best value by the best team with the best analysis of construction.”
The students nodded; thinking of their own bridge projects. Michael and Thor designed the most successful bridge because it held the most weight and was relatively light. “It was the best solution for the least amount of money,” said Juan, a junior.
Principles of Engineering is the junior-level class in John Jay High School’s engineering track. Students typically take Design and Drawing for Production in their freshmen year, followed by Architecture 1 and 2, and Advanced Engineering in their senior year.
“My classes use programs like 3D CAD (computer-aided design). Students will actually use this software in collage and in their careers,” said Mr. Zoeller, Principles of Engineering teacher. “I also have students work in teams so they learn communication skills. It’s so important for them to know how to explain what they are doing to others.
“It’s interesting to see our bridge project on a big scale,” said Brian, an eleventh grader. “We learn a lot of new programs in Principles of Engineering, such as OnShape, a 3D CAD system that lets everyone on a design team simultaneously work together, and SimScale, which perform simulations of CAD models and shows you the weak spots. They use software like this on the New NY Bridge.”
“I never considered civil engineering as a career before,” said Fayth, a student in tenth grade. “This trip opened up new career possibilities.”
“Our infrastructure is falling apart at the seams. This is us starting to turn back the tide,” said Sol, a senior headed to study Naval Engineering at SUNY Maritime in the fall.