MIT Steel Bridge Team breaks into the top 10 at national competition

June 3, 2010

By Denise Brehm
Civil & Environmental Engineering

The regionally top-ranked MIT Steel Bridge Team placed sixth at the national competition at Purdue University May 29, an extraordinary feat for this young team of undergraduates in its fourth year of participation. MIT ranked first among private universities.

Participants in the competition were required to design a 21-foot bridge that can be assembled quickly (the top speed this year was 3 minutes, 12 seconds) and withstand loads of 2,500 pounds with little deflection or sag. While the design rules change annually, all bridge pieces must fit into small boxes (about 3.5 feet long), and during construction, each team member is allowed to enter only certain portions of the staging area and to hold only one bridge piece at a time. This requires team members to pass pieces from hand to hand, relay-race style, as they construct the bridge.

The students’ success this year is due largely to their enthusiasm, willingness to put in late nights and their ability to work well under deadline pressure. Another very important factor was their bridge design, which benefitted from the work of Pierre Ghisbain, a graduate student advisor to the team whose area of research is earthquake engineering and structural optimization. The Department of Civil and Environmental Engineering (CEE) awarded Ghisbain the Trond Kaalstad (Class of 1957) Fellowship for his voluntary efforts working with the team.

“My specialty is optimization, and the whole competition is really about optimization, so I decided to jump in,” said Ghisbain, who had no prior experience in bridge design, but was very familiar with engineering design software.

“Without his guidance on design issues and the many hours he devoted towards fabricating the bridge during evenings and weekends, the student team would not have been as successful,” said the team’s faculty advisor, Professor Jerome Connor of CEE.

Building a better bridge

Ghisbain explained that the team chose a unique design concept, a truss structure that had far fewer pieces and less depth (the measurement of the height of the horizontal “beam” of the bridge) than the truss structure traditionally seen at the competition. This design emphasized tight connections to optimize stiffness, the category in which the team placed third, and less material to optimize efficiency.

Bridges are judged on five aspects that go into an overall ranking. A sixth category, “aesthetics,” is used as a tiebreaker. The “economy” rating is based on the construction time and the number of builders. “Efficiency” is based on weight of the bridge and deflection. “The MIT team has always done well on speed [6:33 this year], and economy. This year’s big jump is due to much better stiffness and efficiency scores,” said Ghisbain.

“At the awards ceremon