building machines

IMG_5898Singing 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.

tabbachi expansion joint

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 Albertian 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.

tabbachi pan closeup

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 disarmare.  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…)

machine iso

09 transparent

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…

nave view 01

4 thoughts on “building machines

  1. Thanks for continuing these blog posts. I do enjoy reading them. Your insight and clarity offer a refreshing look at subjects that are often presented with neither.
    This one in particular struck a chord with me, since I was smitten with Nervi’s work at a young age. I especially appreciated your calling attention to how the “human scale” of Nervi’s work was achieved not only through subtlety of design, but also through awareness of the importance of construction technique. A blending of art and technology that always brings me joy!


    • Well, I think you more than anyone else know where my appreciation of that comes from…Glad you’re enjoying the posts, there’s lots to learn from Nervi, especially seeing the structures firsthand. Hope all’s well!


  2. Dear Tom, thanks for your excellent recent posts, especially ‘building machines’. I note that you’re doing something on glass boxes and i thought you might be interested in an article I wrote for Architectural Design with Chris Arnold back in 1977 on the phenomenon of mirrored glass. The files are big so I should send it to you separately via drop-box. Can I use this e-mail? Best regards

    A N D R E W R A B E N E C K 15D Hyde Park Mansions Cabbell Street London NW1 5AX England T: +44 (0)207 258 0920 M: +44 (0)7802 61 44 77



    • Hi, Andrew–absolutely interested, and please do sent to my Iowa State email address (tleslie (at) The glass box project right now runs from the 1930s up through about 1960, but we’ve been collecting material through the mirrored glass ‘era’ as well. Thanks! Hope all is well.


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