CHICAGO, IL A developer has submitted plans to the city of Chicago, Illinois, for a $700 million supertall residential project that would include the sixth-tallest building in the city.

Chicago-based JDL Development's two-tower proposal includes a 76-story, 1,011-foot-tall tower, which includes nine stories of restaurant, office, retail and other amenities, topped by luxury apartments and condominiums. The adjacent 45-story building will be 100% rental units.

The JDL project, if approved, would be one of the largest residential projects in the city and would require a zoning change. Upon completion, according to Curbed Chicago, the taller tower would be one of eight supertalls in Chicago and the city's sixth-tallest building. 

According to the Council on Tall Buildings and Urban Habitat (CTBUH), buildings 984 feet or taller qualify as supertall. There are currently 126 completed structures worldwide that would qualify as a supertall or megatall building and nearly 150 in various stages of construction or planning, according to CTBUH's Skyscraper Center database. In January, the CTBUH reported that several of the supertall projects had fallen behind schedule and expected a rush of completions this year.

Although America has its share of these skyscrapers, China is first in that category with more than 80 in-progress supertall and megatall buildings and 57 completed. The tallest building in the world, however, will soon be the Jeddah Tower in Saudi Arabia, the first skyscraper to reach 1 kilometer (3,280 feet) in height.

Tall buildings require special mechanical systems to ensure the safety and comfort of their occupants. One area of focus is elevators, a feature that must always remain operational and up-to-speed in a tall building given that very few, if any, building occupants are likely to take the stairs. In addition, the potential for sway and the height and speed at which an elevator must travel in these buildings has spawned a new generation of elevator technology, including the ropes used in elevator systems.

The weight of the traditional steel ropes necessary to move an elevator up and down a supertall precludes a non-stop ride and necessitates features like transfer stations. However, elevator company Kone developed a lighter and thinner carbon-fiber cable in 2013 allowing elevators to make longer runs. The new rope will be used in the Jeddah Tower.