By Debbie Levey
Civil & Environmental Engineering

Weather permitting, on a spring afternoon every year the Course 1 senior class assembles and tests 10-foot-long bridges outside the MIT Student Center. While this eye-catching event always attracts a curious crowd, it is only one of many group projects assigned in this capstone course, 1.013 Senior Civil and Environmental Engineering Design.

“This course ties together the whole experience of sophomore, junior and senior years, where everything that the students have learned is integrated,” said Professor Herbert Einstein, who co-taught the class in the spring semester with senior lecturer Peter Shanahan. “They need to make a design for a problem. The important part is that they design and build, not just design or just build.”

During sophomore year, all CEE students take 1.101 and 1.102, Introduction to Civil and Environmental Engineering Design, where the projects have included designing and building energy-generating machines. The following year, the 1C (civil engineering) and 1E (environmental engineering science) students diverge for specialized courses, then come back together in their senior year for the capstone course, consisting of a set of innovative, open-ended assignments.

This year’s major project topics included the redesign of coastal structures in south Florida to deal with rising sea levels and consequent flooding; restoring south Florida’s Cowbone Marsh after an illegally dug canal altered the hydrology; and rehabilitating MIT’s overcrowded, aging sailing pavilion. Students made and tested a physical model of their designs, rewrote their reports to incorporate feedback they received throughout the process and made a formal presentation of the results. Shanahan emphasized that doing everything in teams is part of the learning process, which can include solving disagreements among team members.

Bridging the curriculum

Displayed and tested in public, the bridges are the most visible assignment. Rules specify that the bridge be made of readily available, cheap materials; portable by a team of four or five students; 10 feet long with a deck two feet above the ground; and able to withstand a ton of concrete blocks without deflecting more than 1/3 inch.

“It’s a test of the students’ conceptual design and a real learning experience. When you actually build something you’ve designed, your design might not quite stand up,” said Shanahan. CEE technical assistant Steve Rudolph and engineers Lisa O’Donnell and Bashar Altabba provided help throughout the project.

This year’s display included six predominantly wooden bridges with steel cables, plus two radically different structures of recycled materials including discarded plastic bags and old tires. Shanahan said, “The students who worked on the recycled bridges knew they were building something really on the edge. We encouraged them because we thought the designs were so innovative, although we knew that the bridges might fail to hold the required weight.”

Because the students laboriously braided plastic bags into progressively thicker suspension cables, Shanahan said the cables were “amazingly strong. They did lots of trial and error and different designs and testing in the lab. It was a neat design experience and they really enjoyed it.”

Stringing together eight tires to take the role of cables in her team’s bridge, Carly Narlesky (1E) said, “Think of all the discarded material in developing countries. We made a simple design with unusual materials to see if we could use tires structurally. I found it challenging because I’m in the environmental engineering track, and I liked the chance to get my hands dirty.”

When the two CEE tracks collaborate on the bridges, Shanahan noted that the 1E students refer to their junior year classes in hydrology and the transport of chemicals in the environment. Likewise, 1C students rely on their junior structural courses.

“The project is open-ended enough so students can draw on almost anything they’ve done,” he observed. “They’ve had a good introduction in sophomore year to working on teams and the design process. By senior year they’re comfortable with tools, and we’ve noticed just how adept they are in construction. These bridges came together really quickly compared to just a few years ago.”