2008: Steel Bridge Team Constructs a Winner

Monday we went through three practice runs of our construction sequence in front of the Student Center. A crowd of thousands (or hundreds ... or maybe 20) cheered as we threw down times of 5:50, then 5:24, then 4:57. This event is always one of our favorite parts of the whole process. It gets us pumped up and lets our friends and faculty see what we’ve been spending so much time on during the semester.

We always try to play the crowd with some antics, such as Adam sitting down to read a newspaper, me doing my best LeBron James impersonation with the chalk, and Matt generally just being a clown.

We were hoping to get our time a little bit lower, but we actually had some problems with the legs. First, it was tough to get them to stand up on the uneven concrete surface, and secondly, the heat actually caused some of our connections to expand, making it difficult to get things to go together. Nevertheless, we were able to demonstrate the sequence that we have worked on so hard, and display our beautiful, slender bridge.

We are continuing to practice the construction sequence and hope to get down to a point where we are consistently under 5 minutes. If we can do this, I feel like a place in the top 10 at nationals is very possible.

Time is running out, however, and we need to ship our bridge down to Florida sometime next week. Then on the Wednesday of finals week we head down there ourselves to enjoy the sun and show the rest of the nation what the MIT Steel Bridge team is made of.

Saturday we woke up bright and early to set up the bridge at UNH's Whittemore Arena for aesthetics judging. Eleven teams were registered for the competition, but UNH was disqualified because the team didn’t complete fabrication of its bridge (because they were so busy setting up logistics for the competition itself). To their credit, they still registered as the 11th team at regionals, making it possible for three instead of two New England teams to enter nationals. Having more than 10 teams compete in a regional competition qualifies that region to send three teams to the national competition.

Merrimack University finished fabrication of its bridge the morning of the competition and made it just in time for the judging. And we thought we waited until the last minute...

The Competition

A surprising three teams entered this year's competition with simple girder bridges, which was truly shocking under the new rules. The rules change a little each year; this year they limited the depth of the girders and increased the importance of stiffness. There were several impressive truss bridges, and an unprecedented arch bridge with a box girder deck from the University of Vermont. But our bridge idea—which can best be described as a frame-supported, cable-stayed bridge—was an original.

We were the second team to construct and load our bridge. We accomplished a construction time of 7:40, but made a couple of minor errors, which added time penalties, bringing it up to 8:15. More importantly, we made a key mistake: at the end of our construction, our bridge didn’t sit completely inside the footings. The judges added a stiff penalty to our score for the weight of our bridge.

Regardless, we went on to load test the bridge. We passed the 50-pound lateral-load test with flying colors, then began the 2,500-pound vertical-load test. Adam Talsma, Matt Pires and I began loading 28-pound weights to the deck of the bridge. By the end, we were becoming very nervous that the top member of our frame would buckle. Thankfully it did not, and we unloaded the bridge quickly after deflection measurements were taken. Our deflection was right about what we thought it would be, but we will have to come up with ways to decrease it in order to be competitive at nationals.

Of the first seven teams who competed, we were the only ones to have a bridge that didn't exceed the maximum deflection or fail completely.

The last three teams to compete—UConn, Laval and Northeastern—were all very good and we were concerned that, because of our penalties, they could all beat us. UConn turned in a good time and had a bridge that performed very well. We all breathed a sigh of relief (or in Adam's case, a scream of joy), when we discovered that we had beaten them by about 3 percent of our own score. Northeastern built their bridge very quickly with just five builders (we had six), and their deflection was 40 percent of ours, so they wound up beating us by a considerable amount. Laval, the last of the teams that we thought would do very well, suffered several costly penalties that nullified the incredible stiffness of their bridge. Laval wound up coming in 4th.

That put us in first place for construction time and second place overall, giving us a chance to compete in the national competition in Florida next month.

We’re greatly looking forward to that, but we have a lot of work to do if we want to be competitive. Keep checking back for more updates on our work.

We're leaving today for New Hampshire and the regional steel bridge competition. Last night we practiced for about three hours, after we uncovered some rules that we had previously missed. The new rules call for a floodway in addition to the river, in which no team members can step. This means that the builders who stand in "barges" in the "river" have a greater amount of work to do than we thought, because the people on land cannot reach many of the connections.

We settled on a construction sequence that is a left-to-right construction rather than a bottom-to-top construction. This way all builders are busy for the entire time. We are confident that this new sequence, which we can complete in roughly eight minutes, will give us good odds to place in the top three at regionals, and earn a trip to the national competition in Florida at the end of May.

Conceptual design began in the fall. We decided early on to go with a truss-like structure this year because the new rules emphasized stiffness over lightness. Based on some other bridges we saw at nationals last year, we came up with a few basic ideas then began to go into more detailed design. Our final product will be a sort of hybrid between a truss bridge and a cable-stayed bridge.

The first detailed design challenge was to decide what to do for the girder pieces. We wanted a section that was lightweight and would provide lateral stiffness, so we could eliminate cross-bracing. The trickiest part was to come up with a connection for the pieces that was quick to put together and also very rigid. We had some ideas for dovetail connections from bridges we saw at nationals, and were able to prototype and test a sample connection.

We began fabrication on the main girder pieces in February, and with the help of Jimmy Duffy and Jimmy O’Donnell from Boston Bridge Services, we were able to fabricate these very efficiently. The next step was to build legs for the bridge and design pieces for the upper part of the truss structure. These pieces were simpler to design than the main girder pieces and were done in the matter of a couple days, although ironing out some troubles with the connections has taken some more time.

We currently stand very close to completing the bridge. We hope to finish up this week and have time to practice before and after spring break.