Straight and Curved

I first started reading architectural theory and criticism when I was still an engineering undergrad student. It gave me a perspective on buildings that was notably different than that I was learning in my design and analysis classes, but because I was an outsider it took me a while to understand the biases contained within. Engineering bias was relatively easy to see, by comparison. One of the assumptions that was taken for granted in architectural critique of the 1980s was that reinforced-concrete structure gave you the freedom to make any shape you wanted while steel structure forced you into boring straight lines. This assumption is simply not true and I’ll give three examples of varying age and architectural interest to back up my statement.

First – and the trigger for me writing this blog post – is the Chicago Loop. Not the neighborhood, but the actual rail loop that created the name. Here’s the intersection of Wabash and Lake Streets:

The Loop was opened in the 1890s as a solution to keep elevated rail moving in downtown Chicago. It is a rectangle with rounded corners – because having a 90-degree corner in rail is a good way to watch every train derail – with Lake Street as the north side of the loop and Wabash Street as the east side. The girder directly over my head forms the east limit of the straight north side; the girder left of the red light is the north limit of the straight east side. The diagonal girders support the curved tracks that connect the two. So the steel structure is straight but is there to enable a use – the “architecture,” if you will – that is inherently curved.

Here’s an older example:

That’s the mid-1880s inside of the Statue of Liberty, where an iron frame composed entirely of straight-line segments supports the three-dimensional curve of the copper skin and its curved stiffening strap-ribs.

And here’s a much newer example: the Guggenheim Bilbao under construction in the 1990s. (Click the link for construction photos.) Note that Bilbao has some curved steel members but the primary structure is a three-dimensional steel space frame made of straight-line segments.

So if we’ve got going on 140 years of curvy architecture supported by straight-line iron and steel, why the assumption that steel can’t be used this way? Because the steel is almost always supporting a curved outer shell (if we call the rails of the loop “the shell”) and that is, to a certain way of thinking, dishonest. On the other hand, I’ve never seen an actual building that is both really honest in that way and bigger than a garden shed.