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BP Pedestrian Bridge

The BP Pedestrian Bridge, or simply BP Bridge, is a girder footbridge in the Loop community area of Chicago, United States. It spans Columbus Drive to connect Maggie Daley Park with Millennium Park, both parts of the larger Grant Park. Designed by Pritzker Prize-winning architect Frank Gehry and structurally engineered by Skidmore, Owings and Merrill, it opened along with the rest of Millennium Park on July 16, 2004. Gehry had been courted by the city to design the bridge and the neighboring Jay Pritzker Pavilion, and eventually agreed to do so after the Pritzker family funded the Pavilion.

Design
Preliminary plans Since the mid-19th century, Grant Park has been Chicago's "front yard", with Lake Michigan to the east and the Loop to the west. Columbus Drive runs north–south through Grant Park, with Daley Bicentennial Plaza in the northeast corner of the park. West of Columbus Drive, the northwest corner of the park had been Illinois Central rail yards and parking lots until 1997, when it became available for development by the city as Millennium Park. Millennium Park is also north of Monroe Street and the Art Institute, east of Michigan Avenue, and south of Randolph Street. For 2007, Millennium Park trailed only Navy Pier as a Chicago tourist attraction. with curving stainless steel plates. In February 1999, the city announced it was negotiating with Frank Gehry to design a proscenium arch and orchestra enclosure for a band shell in the new park, as well as a pedestrian bridge crossing Columbus Drive between Millennium Park and Daley Bicentennial Plaza. The city also sought donors to cover the cost of Gehry's work, which would eventually become Jay Pritzker Pavilion and the BP Pedestrian Bridge. At the time, the Chicago Tribune dubbed Gehry "the hottest architect in the universe" in reference to the acclaim for his Guggenheim Museum Bilbao. Millennium Park project manager Edward Uhlir said "Frank is just the cutting edge of the next century of architecture", and noted that no other architect was being sought. Gehry was approached several times by Skidmore, Owings & Merrill architect Adrian Smith on behalf of the city. In April 1999, the city announced that the Pritzker family had donated $15 million to fund Gehry's band shell and an additional nine donors committed a total of $10 million more to the park. That same day, Gehry agreed to the design request. In November 1999, when he unveiled his initial plans for the bridge and band shell, Gehry admitted the bridge's design was underdeveloped because funding for it was not yet committed. Even at this early point, the need for a sound barrier for Columbus Drive traffic noise was recognized, although Gehry indicated this might take the form of a berm, or raised barrier. The need to fund a bridge to span the eight-lane Columbus Drive was evident, but some planning for the park was delayed in anticipation of details on the redesign of Soldier Field. In January 2000, the city announced plans to expand the park to include features that became Cloud Gate, Crown Fountain, the McDonald's Cycle Center, and the BP Pedestrian Bridge. Later that month, Gehry unveiled his next design, which depicted a winding bridge. While the neighboring Jay Pritzker Pavilion changed relatively little from Gehry's 1999 design when built, the bridge went through several proposed designs. That design was not approved, and Chicago Mayor Richard M. Daley's disapproval of Gehry's subsequent design of an bridge caused Gehry to come up with ten more designs. The first of these plans was for a Z-shaped bridge that would have run northwest–southeast with western ramps in Millennium Park, leading south, and eastern ramps in the empty north section of Daley Bicentennial Plaza, leading north. It would have required elevators to conform to the Americans with Disabilities Act. Gehry had only designed two bridges previously, both in the mid-1990s (Pferdeturm USTRA Bridge in Hanover, Germany and Financial Times Millennium Bridge in London, United Kingdom) but neither was built. Final plan in the background. The final design for the bridge was revealed in an exhibit at the Chicago Cultural Center on June 10, 2000. The clearance was designed to slightly exceed the standard set by the United States Department of Transportation's Federal Highway Administration for urban area interstate bridge clearances, and to allow for additional future layers of pavement below. This height is also greater than the maximum vehicle height of set by the Illinois Vehicle Code. According to the Chicago Tribune the width of the "trenchlike" area spanned is approximately , BP Bridge begins in Millennium Park between the trellis system over the Jay Pritzker Pavilion's great lawn and the Lurie Garden; the design was changed so that the west ramp coincided with the boardwalk of the Lurie Garden seam. The bridge winds its way northward along the eastern edge of Millennium Park before crossing Columbus Drive in a C-shaped curve, above underground parking garage entrances. In Daley Bicentennial Plaza the bridge has an S-shape, then turns east. BP Bridge is designed so that its inclined surfaces have a continuous five percent slope rather than landings and switchback ramps, which provides easy access for the physically challenged. The gently sloped ramp eliminates the need for lifts or any of the other common types of ramps (L-shaped, switchback, U-shaped, straight), and helped the park earn the 2005 Barrier-Free America Award for its exemplary barrier-free design. ) Gehry had hoped to design the bridge so that it could be constructed without a support column in the center of Columbus Drive. However, Chicago Tribune architecture critic Blair Kamin notes that if he had done so, the bridge might not have been as sleek. The bridge is both a connector and a viewing platform for the park. It was designed to link the Historic Michigan Boulevard District and the entire Loop to the west with the Lake Michigan lakefront to the east. It was also designed to be a berm noise barrier blocking noise on the eight-lane Columbus Drive from the Park's outdoor band shell (Jay Pritzker Pavilion), by deflecting traffic sounds upward. It contains large sculptural plates of curvilinear stainless steel instead of more standard flat plates. The concrete base and box girder are flanked by a hollow stainless steel skeleton. Despite its hollow structure, and the fact that it is designed as a concealed beam bridge, the footbridge is built to highway standards and can support a full capacity load of pedestrians. The bridge is designed without standard handrails and uses waist-high parapets as guard rails instead. ==Construction==
Construction
The bridge was built using 22-gauge stainless steel type 316 plates ( 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. The bridge includes two types of structural steel: steel that is thick and in diameter for the approaches and box girders for the span. CATIA software was used to handle the complex geometric layout. To ensure accurate fitting and alignment to the sloping, curving sides of the bridge, 4,400 custom-made convex, concave and radiused cladding panels were fabricated on site by sheet metal contractor Custom Metal Fabricators (CMF). CMF used of stainless steel sheet to cover the sides, which have a combined perimeter length of . CMF built special heated enclosures so that work could continue on site through the winter. They designed, fabricated and installed custom type 4 brushed stainless steel parapets serving in the place of handrails on the bridge. CMF earned the 2005 Tom Guilfoy Memorial Architectural Sheet Metal Award, by the California chapter of the Sheet Metal and Air Conditioning Contractors' National Association for the project. On the day that the two halves of the bridge were joined, each side of Columbus Drive was closed for a 12-hour period and a crane was used to install the girders. Before bringing the crane to the location, screw jacks were used to shore up the underground garage roof to hold the crane's weight. The landscaping surrounding the bridge was redesigned by landscape architect Terry Guen. Honey locusts, ash and maple trees were removed and replaced with three varieties of magnolia and more than two dozen ornamental and canopy trees along the eastern foot of the bridge in Daley Bicentennial Plaza. Other preliminary construction work included setting reinforcing rods for the bridge in the concrete roof deck of the parking garage located under the park. ==Use and controversies==
Use and controversies
Before its official opening on 22 May 2004, the bridge had a private ribbon-cutting ceremony attended by Gehry and Mayor Daley. During the weekend of the ribbon-cutting, Gehry was awarded an honorary degree from the School of the Art Institute of Chicago. The BP Pedestrian Bridge officially opened, along with the rest of Millennium Park, on July 16, 2004. It remained unnamed at the ribbon-cutting, Timothy Gilfoyle, author of Millennium Park: Creating a Chicago Landmark, notes that a controversy surrounds the "tasteless" corporate naming of several of the Park's features, including the bridge, which was named after an oil company. It is well documented that naming rights were sold for high fees, and Gilfoyle was not the only one who chastised park officials for selling naming rights to the highest bidder. Public interest groups have crusaded against commercialization of Chicago parks. However, many of the donors have a long history of local philanthropy and the funds were essential to providing necessary financing for several features of the park. Since the bridge is over an expressway-like trench of Columbus Drive, shoveling the snow onto passing cars is not an option and the Brazilian hardwood would be damaged by rock salt. The city not only mandates that the bridge be swept and washed daily, but also that the parapets be wiped free of fingerprints. The bridge has also had controversial closures in the summer, which were related to larger park concerns. On September 8, 2005, Toyota Motor Sales USA paid $800,000 to rent the bridge and all but four venues in the park from 6 a.m. to 11 p.m. On August 7, 2006, Allstate paid $700,000 to rent the bridge and most of the park for a day. The exclusion of commuters who normally walk through the park and tourists lured by its attractions was controversial, though the city said the money raised paid for free public programs in Millennium Park. ==Aesthetics==
Aesthetics
The bridge is noted for its sculptural characteristics and Kamin describes it as a delightful pleasure that was designed to emphasize its artistic elements while de-emphasizing its concrete and steel support system. Many references to the bridge describe it as snakelike for its winding path, Pulitzer Prize-winning architecture critic Kamin gave the bridge four stars (out of a possible four) in his review and admires how "computers have given Gehry unparalleled formal freedom" to design "the complexity of its geometry" and multidimensional curvatures. Kamin also recommends anyone having a bad day to stroll across the bridge, adding, "You won't get where you're going quickly, but you'll feel a whole lot better once you're done." ==Credits==
Credits
s, the BP Bridge uses parapets (with lights for illumination at night). • Commissioned by – The City of Chicago • Landscape Architect - Terry Guen Design Associates • Project manager – US Equities • Steel supplier – Littell Steel Company • Steel construction – Imperial Construction Associates • Sheet metal contractor – Custom Metal Fabricators Inc. ==See also==
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