The Chicago Spire, Chicago, Illinois, USA

The Chicago Spire is a new (ground breaking in June 2007), hyper-tall skyscraper in Chicago, Illinois. It has been designed by the well-known Spanish architect Santiago Calatrava.

The 150-floor building is being developed by Garrett Kelleher of Shelbourne Development Group Inc and is expected to be completed in 2010. Construction is expected to cost $2.4bn. The Spire was designed for a 2.2-acre lakefront site but its footprint will only occupy half the area.

Access to the tower will be from Lower Lake Shore Drive to reduce the impact on traffic in the neighbourhood – the tower is expected to add one car a minute to the local traffic pattern. Within three months of the building announcement, 800 people had contacted the developer wanting to buy apartments in the building.

HISTORY

The building was originally announced in July 2005 by Christopher T Carley of the Fordham Company and was well received by the city and people. The project failed to acquire the necessary financing and was taken over by Garrett Kelleher, using his own finance with help from the Anglo Irish Bank. There have been three major revisions to the design since the developer changed.

The Chicago Spire will be taller than the Sears Tower and also the Freedom Tower in New York. It will be the tallest solely residential building in the world and the tallest building in the US.

CHICAGO SPIRE LOCATION

The Spire will be constructed along the Chicago lakefront west of Navy Pier, in the Streeterville neighbourhood of the Near North Side community area. The vacant site (sold for $64m by LR Development Company of Chicago and JER Partners of Virginia) is at the junction of Lake Michigan and the Chicago River at 420 East South Water Street, and 400 North Lake Shore Drive.

Some say the design looks like a lighthouse and its positioning bears this out. The new 3.24 acres (1.3ha) DuSable Park, which is to adjoin the property of the Chicago Spire, has a $11.4m budget for its renovation by the City and Shelbourne has pledged to pay $6m toward its development.

DESIGN AND INSPIRATION

Calatrava's design for the tall, twisting skyscraper was based on an imaginary smoke spiral coming from a campfire near the Chicago River lit by Native Americans indigenous to the area. He also related the newly designed pinnacle to the 'graceful' and 'rotating forms' of a snail shell.

The building has been described as a 'giant drill bit' by the public and others have likened it to a 'tall twisting tree' and a 'blade of grass'.

The Chicago Spire will stand at 2,000ft (610m) and include 1,200 apartments with the structure also housing a communal viewing room at the top floor offering residents a view of the four surrounding States.

Each of the 150 storeys will rotate more than 2° from the one below with a total 360° rotation. For structural support, each floor will be surrounded by cantilevered corners and four concave sides. The five-storey lobby will have translucent glass walls and be framed by arching, steel-reinforced concrete vaults.

The seven-sided glass tower will taper and twist to its peak and will contain three million square feet (278,709m²) of floor space.

STRUCTURE AND FUNCTION

The structure of the Chicago Spire will benefit greatly from its design, because curved designs tend to add strength to the structure, and in addition the curved face of the exterior will minimise wind forces (important in the Windy City). The curved design will not completely negate wind forces, so a tapering concrete core and 12 shear walls emanating from it will also be installed to counteract these forces.

The entire structure will perch on seven, w-shaped columns that surround a 56ft-tall glass atrium. The structure of the Spire is liked by the residents of Chicago as it will block less sunshine than the buildings previously planned for the site.

The Chicago Spire will also incorporate as much environmentally friendly technology as possible and the developer is aiming for LEED gold certification. The LEED will stipulate that rainwater be recycled for landscaping treatments, river water be used for cooling and special glass be included to protect migratory birds.

The Spire is designed to be made primarily out of concrete and, in response to the 9/11 attacks in New York, will have two emergency stairwells.

CHICAGO SPIRE REVISIONS

In December 2006, Shelbourne Development stated that the design of the building had been revised. This included the removal of the hotel (bottom 20 floors) and broadcast antenna, making the building all apartments. The design change also altered the twist to be consolidated towards the base of the building (wider than the original plan).

In addition the spire no longer tapered at the top, resulting in increased floor space and more floors. Finally, the building's separate parking structure was replaced with underground parking below the Spire.

By March 2007 the architect Santiago Calatrava had restored the rotating design and presented a vision of the lobby, and now the building is in its final design form awaiting ground breaking. There has been some contamination (radioactive thorium from an old adjacent light bulb factory) of the site found during routine tests but this has been dealt with.

The building was finally given unanimous city approval on 12 May 2007 by the Chicago Planning Commission. The commission approved the fourth change of the design.

CONTRACTORS

The building was designed by Santiago Calatrava, who is the lead architect and engineer on the project. The architect of record is Perkins and Will. The structural engineer of record is Thornton-Tomasetti Engineers Inc. Other companies involved include Walsh Construction, Santiago Calatrava SA, Buro Happold Consulting Engineers PC, Cosentini Associates, STS and FPD Savills.

A factor that could increase the complexity and cost of the project would be excavating to build an underground car park so close to the river. To dig below the water level while keeping the site dry would require the use of a process called slurry wall construction that calls for great skill and time, both costly commodities. Because of this cost, the units might have to sell for $1,500/ft² or above.