millennium tower, southern european version
April 12, 2017 § Leave a comment
Bologna can’t, honestly, take last Fall’s controversy over San Francisco’s leaning Millennium Tower seriously. I mean, check out the Torre Garisenda, which greets me each morning on my walk to the office. Built in the early 12th century as one of dozens of defensive towers in the city, it started proving some fundamental elements of soil mechanics right away, and eventually construction just stopped. That’s a good 2 or 3 meters out of plumb, by my estimates, over a height of 48 meters. Admittedly, it was shortened in the 14th century because of its lean–no doubt a wise move–but the fact that the remaining stump has been standing there, in a legitimate seismic zone and on obviously poor soil, for nine hundred years suggests that the very slow tendency of everything we build to ooze into the earth can be arrested for usefully long periods. I’d still argue that’s the fundamental goal of any good geotechnical engineer.
Torre Asinelli, in the background, has a less dramatic lean and stands at the same impressive 97 meters as it’s been since it was constructed around the same time. Interestingly, one of the things I’ve found out about Nervi’s work here in Bologna (thanks to the brilliant thesis of Sofia Nannini) is that he won the contract for the tobacco factory here in part because he suggested changing the foundation type specified in the competition–from standard bearing footings to friction piles. Bologna’s soil is apparently Chicago-like all over, and that system made much more sense. It also, given the leaning tower in SF, rings a bell…