A Precursor Design

That’s a view of the interior of the American Institute Hall, formerly the Empire City Skating Rink. The building filled most of the block between Second and Third Avenues, and 63rd and 64th Streets.

Honestly, I’d never heard of it until a recent article on ice-skating mentioned it. It didn’t last long as a skating rink but was taken over by the American Institute for fairs and rented out for athletic competitions. A bicycle race, for example, could easily fit in a space 350 feet long and 170 feet wide. That was an amazingly long span for a roof in that era.

Starting in the 1870s, an important structural type was developed for train stations: the wrought-iron or steel-framed balloon shed, which had arched trusses of ductile metal supporting a fire-resistant roof. Grand Central Depot, constructed in 1871, was the first of these in New York. The metal-framed balloon sheds were preceded by a similar form of structure in wood, of which the Hall is a good example. The striking thing about the building on the Sanborn map fragment above is its yellow color, which means flammable structure. That is an enormous footprint for a building with wood-framed exterior walls.

These wood-framed balloon sheds were rare but there were various examples. Old Structures worked on the 1864 Wagner Institute in Philadelphia, which has a similar truss roof spanning about 60 feet.

The form of the Hall’s trusses seems to be similar to Wagner’s trusses: double wood diagonals between wood top and bottom chords, with a wrought-iron tension rod running between the chords at each diagonal intersection. Our analysis of the Wagner trusses showed that they worked fine for stress but were rather flexible, with significant movement under wind and snow load.

An example of a hybrid is the 1880 Seventh Regiment Armory, which has masonry walls and iron trusses supporting a wood-joist roof.

The drill shed roof at the armory is roughly the same span as the Hall, which goes a sense of how remarkable those wood trusses were. Of course, a wood roof structure that moves a lot under load is liable to develop leaks from splits and tears in the roofing material, and when the hall was 25 years old and about to be demolished it was described as being in poor condition. In one sense it was a temporary exhibit hall that somehow hung around for 25 years, which is almost as remarkable as its structure.