By Joe Nasvik
OWNER: CHICAGO DOT
DOT FUNDING: Federal Highway Administration and Illinois DOT
Architect: Site Design Group, Chicago
ENGINEER OF RECORD: ALFRED BENESCH, CHICAGO
GENERAL CONTRACTOR: James McHugh Construction, Chicago
READY-MIX PRODUCER: Ozinga Ready-Mix Concrete, Chicago
POST-TENSION REINFORCEMENT SUPPLIER: Dywidag Systems International, Bolingbrook, Ill.
LATEX-MODIFIED CONCRETE CONTRACTOR: Henry Frerk, Chicago
TESTING: FLOOD TESTING LABORATORIES, CHICAGO
Running along the Chicago River as it curves south toward St. Louis, Chicago's dual-level Wacker Drive is used by 300,000 vehicles and pedestrians every day. The top level is for local traffic; the bottom level for through-traffic and trucks servicing buildings along the street. Originally built in 1926, the east-west portion was demolished and rebuilt in 2002 and 2003. Many of that project's specifications carried over to reconstruction of the north-south portion, which began in the fall of 2010 and continues today. These include:Considered a bridge deck, Upper Wacker Drive must be designed and built for a minimum 100-year service life and resist chemical assault from deicers.The deck should have no cracks during its service life.Pedestrian access to all building entrances must continue throughout construction, including demolition, even though the deck extends to the building walls on both sides.The vertical clearance for Lower Wacker Drive must increase from 12 feet 6 inches to 13 feet 9 inches to allow for truck access.
Brett Szabo, senior project manager for McHugh Construction of Chicago, says there were additional challenges:Although most of the east-west reconstruction had buildings on one side and the Chicago River on the other, the north-south portion has buildings on both sides, including the Opera House, Mercantile Exchange, and the Willis (formerly Sears) Tower — 18 skyscrapers along the project's entire length.To maintain access to all building loading docks and underground parking, traffic on the lower level continue during construction; thus, upper deck forming operations must proceed with live traffic beneath.The concrete superstructure for the upper deck is built first, at 13 inches thick, then topped with 2 inches of latex-modified concrete to get the final profile and elevation.
Funding for the $54 million project is shared between the Federal Highway Administration (FHWA), the Illinois DOT (IDOT ), and the Chicago DOT (CDOT).
A total of 15 segments — separate 200 x140-foot concrete placements — are planned to complete the construction in mid-2012. As the project progresses, each segment is completed and turned over for public use.
The overall length is 2,900 feet over seven intersections. This construction used 55,000 cubic yards of high-performance concrete , 2½ million feet of post-tensioning (PT) strand, and almost 7 million pounds of epoxy-coated reinforcing steel bars (all rebar on the project is epoxy-coated).
|Historical Wacker Drive|
In 1909, Daniel Burnham and Edward Bennett produced a long-range plan for the development of the City of Chicago that included Wacker Drive: a two-level street alongside the Chicago River circling two-thirds of the downtown Loop. Construction on the east-west portion of the street didn't begin until 1924; the north-south section wasn't built until the 1950s.
For the initial two-year project completed in 1926, workers installed 598 caissons to a depth of 95 feet below the surface to support the 5,700-foot length of the upper deck. More than 1 million pounds of reinforcing steel and 116,000 cubic yards of concrete were used for the columns and deck with a thickness as great as 3 feet.