A long time ago, I read Eric Sloane’s books on early American tools and construction. Some of it stuck with me and some did not, but one item I clearly remember was the origin of stone walls in New England farms. People didn’t build them because they were picturesque, or sturdy, or even particularly useful. They built them because the fields had to be cleared of stones if they were to be plowed, and it was simply too much work to haul the stones completely away. Sometime people do things because it’s expedient, and decades (or centuries) later, we may misunderstand and ascribe motives that were not there.
The picture above is another of the series of construction photos of the bank of America Building at 44 Wall Street, taken in 1925. I’m reasonably certain that the steel beams in the center are the first floor, with the planks below at the cellar level. The wood structure in the right background, looking vaguely like a railroad trestle, is the sidewalk bridge, and I’ve never seen one that was two stories tall. (Doesn’t mean there wasn’t ever a double-decker bridge, and I’d love to find out if there was.) There’s steel framing below the plank, so either the building has a sub-cellar, or the steel grillages at the base of the columns hadn’t yet been buried; the cellar-level steel is what’s supporting the stockpiled beams in the right foreground, where the photo-title text is.
Only one crane is visible, at the left foreground, and it was not in use when this photo was taken.
The relationship between point I was trying to make in the first paragraph and this photo is the use of large built-up steel members. The columns are built up H sections, with either angles or channels (the photo is too low-res to make it out) giving the flanges their own flanges parallel to the web; the girders are pairs of built-up channels. All the built-up sections are riveted together, best seen on the girder nearest us at the first floor, and the one not yet erected sitting on the plank in the right foreground.
People didn’t use these built-up sections because they’re cool, or because they wanted a very specific shape. They used them because in 1925, some twenty years after wide-flange shapes were first used in the US (slightly after they were first used in Europe), there were simply not heavy-enough sections being rolled to make up the girders and columns at the base of a skyscraper. A lot of design effort by engineers went into those built-up sections and an enormous amount of fabrication effort by steel workers. They did it because it was, then, the only way to build what they wanted.
