About the time that Frank Gehry’s design for the Guggenheim Museum Bilbao was grabbing headlines, I started to hear about blob architecture. The gist of the discussion was that the development of 3-D architectural modeling tools had freed designers from the tyranny of regular -or worse, orthogonal – geometry, and the future would be blobby. I have no idea about the future – although as someone who owns a fair amount of furniture that’s rectangular in plan, I’m something of a fan of straight walls and right-angled corners – but I know about the past. It’s always been possible to build blobs.
The picture above shows the inside of the Statue of Liberty, looking up from near the top of the masonry pedestal. The inside of the copper skin of the sculpture is obvious, but there are three levels of structure supporting it. The skin has ribs along it, following the curves, but not directly fastened. Rather, these slender, flexible ribs are fastened with slip connections to allow for some level of thermal movement. The slip connections are most visible on the right center of the photo. Those ribs are fastened to a light (for structure) but heavier framework of angles riveted to form a rough approximation of the statue’s shape. The angles are the diagonal lines criss-crossing all over the photo. And the angle frames are supported on a heavy, cross-braced central pylon, which is the main structure. The large group of rivets at the bottom edge of the photo, slightly right of center, are part of that pylon. It’s difficult, even with modern computer-aided analysis, to make a structure that conforms to the shape of a woman and her gown that is as strong as one with more regular geometry. So the structure has three levels of abstraction: strong and with regular geometry, middling-strong and with geometry that’s roughly conforming, and weak and with geometric that’s closely conforming. Here’s the HABS diagram of the structure:
The ribs adjacent to the skin are not shown, and the difference in weight between the main pylon and the angle frames is clear. It seems odd that the main pylon is not in line with her head, until you consider that it is, as near as possible, at the centroid of wind load.
An article in Gothamist sent me off to the NYPL digital archive for 1883 “construction” photos. They’re technically not the actual construction, since they show the statue being temporarily erected in Paris before being broken up for shipment across the Atlantic. First, the sculpture work yard:
The head grabs your attention, but note that not only has the pylon construction begun, the crowd of dignities is looking at that rather than the head.
For an engineer, that’s the shot that carries weight in more ways than one. The pylon is complete and the secondary angle frames are in progress. You really get the sense here of how the angles exist to connect the irregular geometry to the straight core. This photo is listed at the NYPL as “Scaffolding for the assemblage of the Statue of Liberty, of which the head is shown at left, in Paris.” The use of the word “scaffolding” seems odd, since this is the actual frame, but if the title is a translation from French, it makes more sense.
The arm frame, which is a branch off the main pylon, is complete, and the skin installation is in progress. The polka-dot appearance of the arm frame is an artifact of using riveted connections and diagonal bracing: the gusset plates for the bracing connections are about a third the width of the frame. Here there is actual scaffolding around the outer skin.
The head’s finally up off the ground and the torch has gone missing. There’s something funny about the sequencing here: in the previous photo, the arm frame was complete and it’s missing here even though the skin is further along. My pet theory, with no evidence to back it up, is that this last picture was taken during disassembly, and the others were all taken during assembly. The torch has been packed for shipping and the arm frame was taken down as the skin was being taken off. But there are other scenarios that would explain the discrepancies between this picture and the previous three.
TL;DR: Frédéric Auguste Bartholdi and Gustave Eiffel were so good at their work that 140 years later we’re still marveling at it.
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