January 31, 2015 § Leave a comment
Big and Tall has been looking at ancient construction the last few weeks–we’ll switch this week from playing archaeologists to thinking more like engineers without higher math.
But for the moment, we’re thinking like builders without a lot of lifting capacity. Each week I’ve been giving two questions for students to respond to–one of them a more or less traditional academic question, the other a sketch problem. I’m a big believer in finding ways to let a range of learning styles show their stuff, and I’ve learned the hard way that what makes a smart designer doesn’t necessarily make a smart writer. So the sketch problem is designed to put you in whatever the ancient Egyptian, or Roman, or Gothic, etc., etc., equivalent of a studio desk might be, and to figure out how to solve a construction or design problem with only the tools available then.
So, last week’s sketch question? Take the Basilica of Maxentius, or the Pantheon, or the Aya Sophia, and come up with an efficient way to scaffold the roof. Timber’s scarce in all three eras/locations, so find a way to do it that minimizes the amount of wood you’d need. We’d talked about the fact that neither the Pantheon nor the Aya Sophia could take hoop stresses–the cracks at the former’s base and the windows around the perimeter of the latter show that–and I suggested that might be a clue as to how you could scaffold an ancient dome. Several students realized that this meant the scaffold wouldn’t have to form the whole dome at once–if the dome was going to behave like a series of radial arches, it could be built like a series of radial arches. So this scheme for the Pantheon and the Aya Sophia both suggested wedge- or strip-shaped scaffolding that could be used for form a segment of the dome, dropped slightly, and rotated to the next position.
More difficult? How to build groin vaults like the Basilica of Maxentius. Here, you’d have to build each vault completely, and the best you could probably have done was to build a bay at a time of timber, form the vaults, knock them down, and move them to the next bay. We agreed that the kickers here would probably have been supplemented by a pretty hefty network of ropes and cranes–otherwise it would have been a pretty big splat when the centering came down.
In all of these, the idea is that the form of the building and its structural behavior are intimately linked to how the building was put together. Every structure has to be stable not only when its being built, but also while it’s being built, and sometimes the construction is the most fragile phase of a building’s existence.
Gothic and Renaissance this coming week…quadrature, plans, section, and bearing walls to follow…