Carol Willis was kind enough to point out that yesterday’s image is original from A History of the Singer Building Construction, edited by Otto Semsch. He was the chief engineer for the building and so obviously knew it well, and the book is a promotion piece for the building, for the Singer Company, and to a lesser degree for Ernest Flagg and himself. I had read this book years ago but looked at it again after reading Carol’s email, and I’ve set aside the posts planned for this week to take a moment to look at some of the pictures from the book. The title of this post is not meant as irony: describing the innovative techniques used to construct the Singer Building was, in 1908, roughly the equivalent to discussing the cutting edge of micro-computer or space-station tech today.
Let’s start, as one does with skyscrapers, at the bottom. The Foundation Company built the foundations for a lot of early skyscrapers and a fair number of later ones, and, as seen above, they built the foundations for Singer. I doubt they pioneered putting the company name on everything, but they were good at it: two cranes, a caisson, and two signs in that one picture. The caissons are the steel cylinders in the foreground, and more on them tomorrow. I’m going to go slightly out of construction order and discuss one of my favorite topics: how do you keep the building from falling up?
People have always understood that buildings can fall over or collapse, but the issue of uplift was quite rare before skyscrapers. You get uplift on the windward side of a slender and lightweight structure, and historically most slender structures were masonry and not all that light. Wood-framed church spires are an example of structures that get uplift, as are the more slender pagodas. Large masonry-walled buildings did not have this problem. People switching to steel skeleton framing did two things that led to uplift problems: they built buildings taller and more slender, and they used thinner and lighter walls. There were some very slender buildings constructed in New York between 1890 and 1910, in part because a lot of early skyscrapers were built on small lots. (Obligatory reference: more on this in The Structure of Skyscrapers.) Singer was 612 feet high and the main tower was 65 feet square in plan; a slenderness ratio of 9.4 is higher than most of its colleagues in the “once tallest in the world” group.
The answer was to tie the steel columns to the concrete caissons, and let the caisson weight offset the uplift. Here’s a drawing showing the steel reinforcing – bolts at the top, eyebars lower down – running the height of the caisson from the column steel above:
Here’s a close-up on the large anchor bolts tying the built-up steel column to cast-iron column base and then down to the steel grillage embedded in the caisson top:
And here’s a photo of the reality during construction:
In case you’re wondering, no the building never had uplift problems.