April 28, 2017 § 1 Comment
Singing for my supper…and being invited to more speaking gigs in impossibly intimidating rooms. The University here held a symposium here this week on the role of the Manifattura Tabbachi in Italian culture and Bologna’s history, with contributions from literary and labor history scholars about the larger scope of the Italian state’s monopoly on tobacco (and salt, etc.) in the 20th century. Who’d turn down a chance to sit in when the venue is a 16th century hall with frescoes by Fontana and a staircase by (maybe) Bramante?
Whether I did justice to it or not is another story. My fellowship here has revolved around Nervi’s warehouse and production facility for the monopoly in Bologna, and after a semi-official tour organized by Jacopo Ibello’s Save Industrial Heritage organization and some enlightening conversation with scholars and students here I’ve been looking at the processes Nervi used to build the ballete, which is relatively famous as an example of his interest in patterned slabs using ferrocemento formwork. The Gatti Wool Factory is the most famous of these (and the subject of a particularly good fence-jumping adventure five years ago), but Bologna was his first built experiment in the expressive potential of ferrocemento formwork, and thus of particular interest.
It’s a subtle detail, but you can see from the image above that, unlike conventional two-way, or “waffle” slabs, Nervi’s slab design here includes subtle flare-outs of the joists as they approach the girders, an acknowledgement that shear forces within the former are increasing as they pick up more and more load from the slab above. You can also see that the girders flare out (in section rather than in pain) as they approach the columns, reflecting the same principle. These aren’t really necessary statically, but they resonate with our understanding of the way the stresses in the frame get collected and transferred –whether you know your two-way slab theory or not, I’d argue that this looks intuitively satisfying in ways that a conventional waffle slab doesn’t. It’s a nice, thoughtful piece of ornamentation in the Albertan sense–of clarifying how things are actually working and visually emphasizing the story Nervi wanted to tell.
Ferrocemento allowed him to do this, since the formwork pans were produced by bending wire mesh over a clay mold and then troweling the result with lightweight cement wasn’t limited to the straight, flat surfaces of steel or timber forms. Nervi had used the material with great success in naval experiments during WWII for the Italian Navy, and for the sublime–but incredibly efficient–roof of the Salone B at the Turin Esposizione.
So, between my archival trawl a few years ago and the brilliant work of Sofia Nannini, whose thesis here at Bologna this year was on the Tabbachi, there’s enough information to reconstruct Nervi’s process, and–maybe more interestingly–to reconstruct the ‘machine’ he used to form these slabs. Photos of the construction site show this–brigades of light scaffolding with pans on top, set onto rails that allowed crews to raise them into place, pour concrete over them, and then once the concrete had cured to ‘disarm’ the formwork by lowering it on the scaffold and move the whole system up seven bays, or one week’s curing time. (English doesn’t have a word for removing formwork, but in Italian it’s disamare. Like cantiere, a word that means both “shipyard” and “job site,” this is one of those linguistic oddities that tells you just a bit about different attitudes toward construction between the two cultures…)
I’ve spent a few days building some very basic digital models that future CHiRG research assistants will (I hope) clean up for me, but enough to get the basic sense for how the machines worked and what they defined about the building form. Nervi noted in his notes, and elsewhere in correspondence about the Reynolds project that how you think of scaffolding determines a lot about the building. In this case, the linear process inevitably led to an extruded, but punctuated, form. But it also imprinted the Tabbachi with a distinctly human scale. While other engineer-builders like Candela struggled to make their evocative forms relatable in terms of their scale, Nervi’s process always relied on elements–in this case the individual pans–that could be lifted by no more than three or four laborers, a way of keeping his crews small and his costs down. Today we can read that measure into almost everything he built, which offers an instantly legible grain to his otherwise vast constructions. If the machine itself reminds me of Brunelleschi, who was trained as a clockmaker and whose cranes and engines for Florence’s Duomo were as impressive to many as the finished structure, Nervi’s end results remind me of Alberti, who pointed out that beauty never arose strictly out of a building’s order, but instead out of how that building’s order was rendered in actual matter, and how that rendering was explained visually through proper ornamentation. It might just be the surroundings this month, but these sorts of parallels seem stronger and stronger the more I delve into this…
Thanks to Micaela Antonucci, Elisabetta Margiotta Nervi, Jacopo Ibello, Sofia Nannini, and a host of local caffè purveyors for their help in getting this rolling…
April 17, 2017 § Leave a comment
During last fall’s research trip to Chicago, SOM’s Bill Baker and I got into a conversation about the intractable problem, in architectural detailing, of turning a corner. You’d think this was an easy thing, but any wall with a thickness makes a 90° turn (or, really, any turn) something of an issue, especially in so-called ‘re-entrant,’ or inside corners. Especially if you’re anything of a structural rationalist and want to emphasize the importance of your structural grid, because as the layers of the wall sprout out from the column line, the edge line of your elevation and the grid line of your plan start to diverge, with consequences that you can’t fully understand in two-dimensional drawing.
That’s something of a moot point these days, with the ease of digitally modeling in 3-d, but historically it’s been a point of some debate. If the edge line of the building (the “demise line,” in the more theatrical British term) doesn’t coincide with the structural line, then what do you emphasize? Do you make the corner lightweight, trying to make it disappear? This was an established International Style approach–pioneered by Walter Gropius but absolutely employed by SOM in their classic glass skyscrapers. Inland Steel took a particularly brave stance, making external corners of its floor plates and re-entrant corners of its cladding system.
By the end of the evening, we’d pointed out to ourselves that this wasn’t just a skyscraper problem, and that the corner had produced headaches and inspiration for a few hundred years. And in the last couple of weeks that conversation has fueled a few detours to find examples of Renaissance architects struggling with this problem–how to express a one-dimensional grid line that gets manifested in three dimensional material. Or, in Alberti’s words, how the lineaments of a design, which exist only as mathematical entities, get expressed in the matter of design, the actual stuff that buildings get made of.
Here’s the crux of the problem: Brunelleschi’s cloister at Santa Croce (1453):
You can see what he’s done–the column lines supporting the two arcades both hit on one single point, where the corner column is located. This is correct in plan, correct in elevation…and totally wrong in perspective, because our eyeballs correctly read that the thrusts of those two arches (which, admittedly, aren’t that much physically because of the nature of the wall, but are still visually how we read the arcades) as trying to topple the column back into the cloister behind it. It’s a visually weak detail–the column doesn’t have the whoomph (technical term) to resist the visual pressure being put on it. (Also, the arches collide with one another in a detail that’s visually awkward and undoubtedly cost a few extra florins, as the stonecutters had to figure out the tough three-dimensional geometry of intersecting arcs).
But it wasn’t just arcades that gave Brunelleschi fits. In the Old Sacristy of San Lorenzo, you can see that he knows there’s a ‘column’ at the internal corner of the main space, but the wall folds it in two, leaving it kind of stuck. Its counterpart in the background is also clearly not happy:
Alberti faced the arcade problem in the Rucellai Palace (also 1451)–not open to the public, but you can see this in the Strozzi Palace, designed in the 1480s and clearly patterned on Alberti’s work:
It’s odd that Alberti would have struggled with this, since his re-invention of the pier and engaged pilaster actually provided a reasonable solution to the problem. By giving the arches and the architrave above separate vertical elements, his successors discovered that you could have the arches land on their supports, turn the corner on the ‘column’ that now found itself buried in the depths of the pier, and then start fresh around the corner. Here’s Bramante figuring this out in the cloister of Santa Maria della Pace in Rome:
There’s still the problem of the trapped column, though, right? It turns out that if you adhere so strictly to the fairly simple rules that Vitruvius and Alberti codified, there’s no good way to turn this corner–either you end up with a weak corner or you trap a column inside a pier.
The trick turned out to be offsetting the grid by a column’s width and tripling up on columns in the corner, creating a dense area of detail while making the corner structurally and geometrically sound. Michelangelo figured this out in his redesign of the Farnese Palace’s courtyard:
You can see that the first column in each wall is actually offset from the actual grid, like this (or, you can think of it as Michelangelo shortening the inner bays of the grid to ‘dig out’ the otherwise trapped column):
This trick shows up all over the place for the next five hundred years–in Schinckel, in Mies, in almost anything designed by an architect obsessed both with order and with the visual effects of expressing that order. What I like best about this story is that the apparently ‘perfect’ rules of antiquity contained within them inherent contradictions between what the building order ‘wanted’ to be, and what our eyeballs want to see. And it took some futzing around on the part of Bramante and Michelangelo to figure out how to get our senses and our minds to both be happy with what they’re seeing, even if it required a bit of fiction and chopping out a thin layer of building to get back to the grid we’re expecting. It’s a classic case of “the lie that tells the truth,” to paraphrase a colleague of mine. Or, as Vignola put it, right around the time Michelangelo was working on the Farnese,
“Should someone judge this a vain effort by saying that one cannot lay down a fixed rule, since, according to the opinion of all and especially of Vitruvius, it is often necessary to enlarge or to diminish the proportions of ornamental members in order to remedy with art where our vision has been deceived by some occurrence, to him I reply that concerning this matter it is necessary to know how much should appear to the eye…and then proceed in this by certain good rules of perspective, whose practice is fundamental both here and in painting…”
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…
April 9, 2017 § 1 Comment
Florence yesterday. I’ve settled into a weekday pattern in Bologna that is proving productive, but the weekends this month are absolutely about being a tourist (or, excuse me, for my Chair’s benefit here–getting good slides for next Fall’s ARCH 423 course). I know from experience that going to Florence without a work plan and sharp elbows is a recipe for disaster, especially in the height of the spring tourist season, so I hung yesterday’s itinerary on one story from Vasari that floored me last year while reading up on Brunelleschi for class:
WITH HIS OWN HAND he made…the model of the house and loggia of the Innocenti, the vaulting of which was executed without framework, a method that is still followed by all in our own day. It is said that Filippo was summoned to Milan in order to make the model of a fortress for Duke Filippo Maria, and that he left this building of the Innocenti in charge of Francesco della Luna, who was very much his friend. This Francesco made an architrave-ornament running downward from above, which is wrong according to the rules of architecture. Wherefore Filippo, on returning, reproved him for having done such a thing, and he answered that he copied it from the Church of San Giovanni, which is ancient. ” There is one sole error,” said Filippo, “in that edifice, and thou hast followed it.”
So, for those of you not up on your classical elements, the architrave in Brunelleschi’s Loggia deli Innocenti (1419-1427) is the strong horizontal band that runs straight across the top of the arches. Arch- is (roughly latin) for ‘top’ or ‘main,’ and trave is a straightforward word meaning ‘beam.’ So the architrave started life as the main beam supported by columns, and migrated over time to any strong horizontal band that is visually supported by piers, columns, or pilasters. It’s a good way of separating stories, emphasizing a horizontal grain, or just tying together, say, a bunch of arches.
What beams don’t do, at least in classical language and structure, is suddenly make a 90° turn and dive into the ground, which is what Francesco della Luna did in Vasari’s (undoubtedly exaggerated) story:
This is the detail at the very end of the loggia, and it’s safe to say it doesn’t show up in many history textbooks, because it just looks odd (one exception–an essay by Tim Benton in a collection titled Making Renaissance Art from 2007). A structural rationalist would point out that the column is already doing the “work” of holding up a beam in this allusion, so why on earth would you also need a beam/column holding up the corner? Brunelleschi’s right to call it an ‘error,’ at least as it appears here.
But Francesco was also right, if Brunelleschi told him to copy the Baptistery, (1059-1128) because the one place a true architrave exists is on the upper story, where it crosses over four columns and then, at the edges of each wall, it dives down exactly like the detail on the Ospedale. (If the builders of the Baptistery had been good classicists, of course, they would have made the horizontal line above the arches, on the lower story, a true architrave, too…)
So, what gives? First, Vasari was notorious for repeating gossip, whether substantiated or not, and it seems unlikely that, no matter how busy Brunelleschi was, such a detail would have been left in the hands of a subordinate. He was notorious for giving verbal orders instead of drawing things out, but still, this was a howler. And, of course, if he had just said “copy the Baptistery,” any good second-in-command would have copied the lower story, which had arches similar to those of the Loggia, right?
The problem, I think, is the confusion that was evident in medieval building–and for that matter in the first couple of generations of the Renaissance–between the structural and the graphic languages of classicism. The architrave is a horizontal punctuation in its purest form–a graphic that’s designed to cast a deep shadow line on a facade and thus to drive home that there’s a distinction between what’s above and what’s below. But the builders of the Baptistery faced a curious problem that results from its octagonal shape. How do you make visually strong corners–necessary if you want to connote the monumental presence of one of the most important religious and political structures in the city–with a language of columnar, point elements? On the lower story they resorted to the green and white stripes that are familiar from medieval building all over town–effective visually. But the top is designed to be visually lighter, and it’s apparent that here the builders reverted to a graphic trope that borrowed the multiple lines of classical architraves and simply repeated it at the obtuse corners. There’s a bit of a vertical emphasis there that let them finish off the intercolumniation, and that lets one facade ‘breathe’ a little without being jammed into the corner of the next. It’s not overly elegant, but in white stone it’s also gentle.
In grey pietra serena, however, it’s a pretty violent clash, and whatever the actual story one can imagine Brunelleschi being desperate to blame the results on anyone handy. Whatever the actual story, the lesson was clearly learned. Here’s Alberti, who learned every trick he could from Brunelleschi, employing a very Baptistery-like architrave to help distract from the fact that the graphic ‘columns’ on the facade of Santa Maria Novella (1448-1470) don’t actually line up (note that he repeats the ‘mistake’ of pairing the column with, in this case, a pier…but the pier has those horizontal stripes that make it at least seem like it’s part of a different system):
And sometime later, here’s Alberti with a more archaeologically correct architrave on the Rucellai Palace (1446-1451, and maybe more by Rossellino than Alberti):
That’s doing it right, at least by classical rules. The horizontal line makes an absolute distinction between stories, and it carries all the way around the corner, making it seem that the columns at the corners are doing what columns do, namely carry the beam above them. It’s free and clear, too, of the arches, which also makes an important distinction that Brunelleschi never quite understood–that if the columns carry the beam, the arches really aren’t necessary except to carry the bit of wall between them and the beam itself. It makes sense to disengage these, and to put the arches on separate supports, to show that there are two different orders of structure going on here.
Splitting hairs? Sure. But this is the fun of teaching Renaissance architecture in between research on concrete and steel, etc. There was an awful lot of extra money and time being thrown around in Florence in the 15th century, which meant that for the first time in centuries architects got to throw ideas around and think about how ornament, or detailing, could help tell a story–or could make an otherwise legible facade trip over its own feet. That lesson is worth learning, and the subtleties are, if nothing else, fun to ponder. Over a doppio or two, in the midst of a 30,000 step, half-million tourist kind of a Saturday.
April 5, 2017 § 1 Comment
The next five weeks are going to be pretty alright, as my colleague Pete would say. I’m a Visiting Fellow at the Università di Bologna, where I’ll be doing some freestanding research on Nervi’s Manufattura di Tabbachi and catching up on some writing projects. In exchange for an apartment and access to the library here Fellows give, uh, one lecture, which happened last night. Most of the subject matter remains to be discovered and assembled, but I appreciated a crowd that was willing to listen to some rampant speculation, and to see some of the highlights of my research group’s work over the last few years. My sponsor, Renaissance and Nervi scholar Micaela Antonucci, has been an extraordinary host and very graciously documented the talk. Americans are easily impressed by “old stuff,” but the Sala Rossa at the University, which dates to the 15th century, was a particularly inspiring place to speak.