41st Street Pedestrian Bridge

Chicago's 41st Street Pedestrian Bridge design was an award winner right from the get-go.

The design team’s curving, arch-supported steel concept won an international design competition to create the bridge. The resulting span connects the city’s Bronzeville neighborhood with the trail system that runs along Lake Michigan. The bridge provides pedestrians with safe passage over Lake Shore Drive as well as the Metra Electric/CN Railroads, both of which had to stay in operation during construction. The railway sees approximately 263 trains per day while Lake Shore Drive carries approximately 100,000 vehicles per day.

Two main component round sections (36-in. and 48-in. OD induction bent pipe) tied together with built-up box girders form the main span of the pedestrian bridge. The pipe and bridge have both sweep and camber, so the pipe had to be carefully bent in order to induce both elements simultaneously. The process of induction-bending the pipe was particularly challenging, given that the actual diameter, ovality, and pipe shrinkage had to be taken into consideration prior to fabrication to ensure all of the subcomponents that tie into the pipe fit correctly. The bridge was progressively preassembled in the shop in order to ensure proper geometry and fit-up, which was especially challenging due to the large sweeping and curving geometry that required much preplanning and lots of shop floor space.

The team also had to figure out the logistics of shipping the large sections of the bridge from two fabrication shops to the project site. The bridge components were shop-welded to their fullest extent, resulting in extremely long, wide, and heavy permit loads that required significant preplanning and coordination. The largest structural piece was 62 ft long, 24 ft, 4 in. wide, and 38.3 tons, with the heaviest structural piece being just over 42 tons. The bridge was shipped to the job site in 14 built-up sections, including six approach single-pipe spine assemblies and eight main span double-pipe assemblies; the main span assemblies were more than 24 ft wide.

The arches use bolted splices as well as field welds for aesthetic purposes. The design team chose to use the end-plate bolted connection option to save time and cost during erection.

Prior to delivery to the site, the structural steel was blasted and painted with a three-coat paint system in the shop. The project came in under budget and opened six months ahead of the original contract completion date.

Project Team

Steel team:

• Fabricators:

  • Hillsdale Fabricators, St. Louis *AISC MEMBER* *AISC CERTIFIED*

  • Metal Pros, LLC, Wichita, Kan. (handrails) *AISC MEMBER* *AISC CERTIFIED*

• Bender-roller and additional fabricator: BendTec Inc., Duluth, Minn. *AISC MEMBER* *AISC CERTIFIED*

• Detailer: Esskay Structures, Inc., Vienna, Va. *AISC MEMBER*

• Erector: S&J Construction Co., Inc., Oak Forest, Ill. *AISC MEMBER* *AISC CERTIFIED*

Designer/engineer: AECOM, Chicago

General contractor: F.H. Paschen, S.N. Nielsen & Associates LLC, Chicago

Construction manager: TranSystems, Chicago

Owner: Chicago Department of Transportation, Chicago