Notes on Skybridge Engineering Session

Our conception of a sky-bridge is the idea of a structural solution that one can inhabit, as well as a space that would make the center feel special in some way. We believe there is a solution that can integrate the skin, walkway, and the structure. Wednesday’s meeting with the engineers produced a constructive dialogue that led us to rule out solutions that had not considered all the facts and consider new ones. One of the main issues our engineers brought up was the fact that the older building would probably not hold up against strong lateral loads. This immediately ruled out our initial idea of a suspended glass tube with enclosed walkway, a.k.a. “the Chinese finger trap” despite the seductive rendering. One solution, however, to keep a similar idea would be to extend a leaning, tapered pylon from the sidewalk on the side of the older building that would counteract lateral forces and leave only a short span for a beam. This led to the issue of obstructing sidewalk space. We all agreed that it really isn’t an area that we would want to obstruct as there is a large amount of foot traffic, bike traffic, and delivery trucks that pass this location on a daily basis.

Our engineers brought a couple sketches of ideas that could work structurally, but remained a simple frame. The one that interested all of us the most was a tied arch that rested on an inserted beam on the side with the older building. Lateral forceswould be taken by a tension element at the base. This seemed to work, but was a bit massive, as we would need to buildcompressive elements that would have to reach very high above the walkway. The issue of enclosure was still at question in this scheme as there was nothing really lending itself to a place that would be fully enclosed. We kept this idea on the backburner as we looked into alternative solutions.

We explored the idea of a “drawbridge” type design that would consist of a beam that was hung from the newer building by a cable stay. This still required either a large beam solution or many cable attachments on the exterior of the new building, which didn’t really appeal much to any of us as a really smart solution.

We began exploring other options. Another idea we had brought a sketch of was to create a corrugated beam that wasblown up to the size of being inhabitable. This allows a meandering, as well as a straight path, opens up opportunities for varying transparency, making the center point of the bridge a special moment and small alcoves of some inserted programmatic detours. The corrugations would be designed to correspond with the shear forces in the bridge. This seems to be our most viable solution so far, as the stress induced would remain vertical for the most part. Our engineer friends seemed to like this idea as well. The big question that remains is one of materiality and construction. We briefly discussed the issues of constructing on such a busy road. Something that could go up quickly will be fairly important on such an important artery on the MIT campus. We are now considering ways of breaking up the corrugated beam into secondary members that can reduce weight and increase transparency. This will lead to some real decisions on materiality and construction. This is as far as we I think we were all a little stuck at times, but, overall, it was a really positive session. No one was afraid to throw in new ideas, or toss out old ones; everyone’s input was valued and respected. I think we would all agree this was a great opportunity and should be continued in the future. We exchanged contact information and will most likely meet again soon so we can discuss the further progress the design.

Tyler Crain