BP Pedestrian Bridge in Millennium Park
This iconic pedestrian bridge has a unique sinuous shape and connects two parts of Chicago’s Grant Park on the lakefront. The collaborations between SOM and Frank Gehry, the BP Bridge crosses Columbus Drive and connects downtown Chicago’s Millennium Park and Grant Park to the east. In each collaboration, SOM structural engineers play a critical part in the process of developing the structures that enable the support of Gehry’s inventive curved metal surfaces.
The BP Bridge extends across Columbus Drive and connects Millennium Park to the Daley Bicentennial Plaza. the polished stainless steel façade of the Bridge snakes through Millennium Park and spans over Columbus Drive, offering a magnificent view of the city’s skyline and waterfront. as a pedestrian negotiates the gently undulating curved path, the views change. it was reportedly difficult to acquire Gehry’s design team for the Millennium Park project. the firm was already fully committed to other work when adrian smith, the principal architect from soM, first approached him.
Gehry initially turned down the opportunity to design a sculptured addition to the Park’s “band shell.” Convincing Gehry to sign on appears to have required combined efforts and incentives. the Pritzker family traded on their long-standing relationship with Gehry (a former winner of the prestigious Pritzker Prize for architecture) and made a $15 million gift to fund the project. ed uhlir also included the BP Pedestrian Bridge as part of the design project, which would be the firm’s first bridge commission.
The Bridge provides a connection to the Plaza, views of the city and parks, and a sound barrier between the Pavilion’s lawn and Columbus avenue traffic noise. Craig Webb, the project designer for Gehry Partners, tells the story of one exchange between the Mayor and Gehry, during which the Mayor expressed concern about the visual impact of the Bridge on the site. Gehry explained that no one would really see the bridge in plan, only on its edge. it would be like the flat edge of a butter knife, rotated so that the blade would be seen only in its narrow dimension.
It opened along with the rest of Millennium Park on July 16, 2004. Named for BP (British Petroleum), who donated $5 million to the Park’s construction, the 925-foot long, 20-foot wide, winding footbridge serves not only as a connector, but as a viewing platform and a berm sound barrier, blocking noise on the eight-lane road below.
The first Gehry-designed bridge to be completed, BP Bridge was designed with a continuous slope rather than landings and switchback ramps. Its modest 5% slope provides access for the physically challenged. The use of large sculptural plates of curvilinear stainless steel and biomorpic allusions that are two of Gehry’s signature stylistic footprints. The bridge is designed without standard handrails and uses waist-high parapets as guard rails instead. The landscaping surrounding the bridge was redesigned by landscape architect Terry Guen.
Frank Gehry was hired to design the bandshell and the pedestrian link; his first bridge design commission. The first concept was a simple straight bridge that was only a fifth the total length the bridge would eventually become. In an effort to increase the design quality and to be fully compliant with requirements of the Americans with Disabilities Act (ADA), the design was eventually modified into the current 925 foot length which has a consistent gradient below 5%. The final design is equally inclusive of all users including those with disabilities.
The primary cladding of the bridge is 22 gauge stainless steel paneling that was custom manufactured and fitted in the field. The bridge deck itself is made from Brazilian hardwood that is resistant to rotting and creates a comfortable walking surface.
The bridge was built using 22-gauge stainless steel type 316 plates (0.031 inches / 0.79 millimetres thick), with an angel hair finish and a flat interlocking panel process. Stainless steel type 316 is known for its excellent welding characteristics, as well as for its resistance to pitting. According to the Chicago Tribune, the bridge materials used in construction include 2,000 rot-resistant Brazilian hardwood boards for the deck, 115,000 stainless steel screws and 9,800 stainless steel shingle plates. According to Architecture Metal Expertise, the bridge has “10,400 stainless steel trapezoidal panels in 17 different shop fabricated configurations involved 1,000 shop hours”.
The sheet metal work totaled 5,900 field hours over a six-month period. During construction, about 200 shingles were installed per day. The bridge includes two types of structural steel: steel that is 2.0 inches / 5.1 centimetres thick and 20.0 inches / 51 centimetres in diameter for the approaches and box girders for the span.
Project name: BP Pedestrian Bridge (BP Bridge)
Location: Millennium Park, Chicago, Illinois, United States
Type: Bridge, Pedestrian / Street, Public Facilities
Materials: stainless steel, reinforced concrete, and hardwood
Structural Type: Girder Bridge
Length: 935 feet (285.0 m)
Width: 20 feet (6.1 m)
Design Year: 2002
Construction End: May 22, 2004
Opening Date: July 16, 2004
Completion Year: 2004
Client / Owner / Developer: City of Chicago
Architects: Frank Gehry – 12541 Beatrice Street, Los Angeles, CA 90066, United States
Structural Engineer: SOM-Skidmore+Owings+Merrill – 224 S. Michigan Avenue, Suite 1000, Chicago, IL 60604, United States
Text Description: © Courtesy of SOM-Skidmore+Owings+Merrill
Images: © Franco Di Capua, flickr – Maricel Cruz, flickr – pov_steve