THE CONCRETE BRIDGE MAGAZINE

FALL 2018

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/1027820

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Architecturally, Chicago is considered one of the world's greatest cities. This recognition is due in no small part to the Plan of Chicago 1 or the "Burnham Plan," the early-20th-century vision of architects and urban planners Daniel Burnham and Edward H. Bennett. In p a r t i c u l a r, B u r n h a m a n d B e n n e t t advocated for protection of the Chicago lakefront with an extensive network of parks bordering Lake Michigan that could never be commercialized. In 1973, the Lake Michigan and Chicago Lakefront Protection Ordinance further solidified this commitment to a public lakefront and included requirements to provide universal access to the lakefront for all of Chicago's neighborhoods. Over the years, the urban plan led to the construction of numerous bridges and underpasses to allow pedestrians to safely cross Lake Shore Drive and access the lakefront. The original 35th Street Pedestrian Bridge built in the 1930s was one such access point. However, by the early 21st century, the bridge no longer served its purpose. It was classified as structurally deficient and did not meet the requirements of the Americans with Disabilities Act. Call for Proposals In 2003, the Chicago Department of Transportation (CDOT)—in conjunction w i t h t h e C h i c a g o A r c h i t e c t u r e Foundation—initiated the "Bridging the Drive Competition" to solicit concepts for replacement structures for four pedestrian crossings of Lake Shore Drive, including the 35th Street Bridge. The City intended to create iconic bridges at each of these locations. The international competition garnered 67 proposals from 23 firms. The concept submitted by EXP was selected as the winning entry for the 35th Street location. Project Challenges and Design Specifications The 35th Street Pedestrian Bridge invokes the classic principles of a self- anchored suspension bridge, but with a twist. It crosses over Lake Shore Drive on a horizontally reverse-curved alignment, which provides for panoramic views of Lake Michigan and the Chicago skyline. The S-shaped curvilinear alignment became a necessity due to the unique site constraints—the western approach is between two historical landmarks, the Stephen A. Douglas Memorial and a former Civil War hospital. The alignment also minimizes the distance of the Lake Shore Drive crossing, limits the required approach grades, preserves a grouping of mature trees in Burnham Park, and achieves the required vertical clearances over Lake Shore Drive and the railroad. profile 35TH STREET PEDESTRIAN BRIDGE / CHICAGO, ILLINOIS BRIDGE DESIGN ENGINEER: EXP, Chicago, Ill. CONSTRUCTION MANAGER: CH2M, Chicago, Ill. PRIME CONTRACTOR: McHugh/Araiza Joint Venture, Chicago, Ill. POST-TENSIONING CONTRACTOR: James McHugh Construction Co., Chicago, Ill. OTHER MATERIAL SUPPLIERS: Post-tensioning strand and hardware: DYWIDAG-Systems International USA, Bolingbrook, Ill.; Suspension cable: WireCo WorldGroup, Kansas City, Mo. 35TH STREET PEDESTRIAN BRIDGE by John Hillman, Parsons Construction Group, and Brian Umbright, EXP Overview of the completed bridge looking north. All Photos: Dave Burk Photography. 12 | ASPIRE Fall 2018 P R O J E C T Installation of the main cable and hanger system. The main cable is composed of seven parallel 3½-in.- diameter cables and becomes integral to the superstructure near the bridge ends.

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