Architecture Puzzler #66

At the time the Dirigible Dock building was first built (1929), it was considered by some to enclose the largest unobstructed space in the world. Each end of the building had two doors measuring 202 feet (62 meters) high. Each door pivoted on a single pin at the top. Guess how these doors were designed to be pulled open. By teams of horses, a system of weights and pulleys, or with a locomotive?

Glass takes 13 to 25 gigajoules of energy per ton to produce while copper takes 70 to 170. About how much energy would you guess is required to produce a ton of steel? Aluminum?