New Mississippi River Crossing Design Chosen

  


     Beginning in April 2000, for the past 18 months, Modjeski and Masters assisted the Illinois and Missouri Departments of Transportation in working with citizens and officials from throughout the St. Louis region to identify a world-class design for a new Mississippi River Bridge north of downtown to carry both I-70 and I-64.  

     Six concept bridges were selected to study from more than 30 initial design concepts by the owners, the design team, and members of the community advisory committee at a Design Charrette in late November 2000.  The six different bridge designs studied for the new structure included:  a river spanning cable-stayed bridge with single inclined pylon towers; a cable-stayed bridge with bent leg A-frame towers; a cable-stayed bridge with Y-towers; a river spanning suspension bridge with delta towers; a river spanning suspension bridge with pylon towers; and a hybrid cable-stayed/suspension bridge with trident towers.  These designs underwent rigorous evaluation over a nine month study period. Selection of one bridge to carry forward to final design was made in July of 2001.

     The selected design is a world-record-breaking, signature structure that will further define the region's skyline for generations to come --- a river spanning cable-stayed bridge with two single-pylon towers, inclined nine degrees away from the river and soaring 435 feet above the roadway.

     Modjeski and Masters was chosen by the Illinois Department of Transportation to perform the bridge type study and to provide preliminary and final design for the proposed bridge.  Modjeski and Masters was chosen from among four other firms deemed acceptable by an advisory panel of engineers, planners and civic and businesses leaders.  The project is being sought to alleviate traffic on existing bridges linking Illinois and Missouri in downtown St. Louis. The structure is to be part of a $1 billion package of highway improvements.    

    To learn more about the project, visit the official New Mississippi River bridge website at www.newriverbridge.org.  

  

 

Home

  
PROJECT FACTS
  • World’s widest cable stayed bridge at 222 feet.
  • Main span of 2000 feet provides longest clear span across the Mississippi River and longest cable stayed bridge in Western Hemisphere.
  • 5th longest cable stayed bridge in world when completed.
  • First major cable stayed bridge to use three planes of cables in the main span.
  • Main bridge consists of three spans totaling 3200 feet.
  • Two towers measuring 435 feet above the roadway, inclined 9-degrees from the river.
  • Eight mainline traffic lanes; each roadway includes two full shoulders providing a potential for 12 lanes in the future.
  • Edge box girders provide unique superstructure solution.
  • Center slot provides aerodynamic stability
  • Extensive use of high performance steels

DESIGN CHALLENGES

  • Inclined main span towers and resulting "locked-in" loads
  • Overall width of main span
  • Owner’s requirement for future deck replaceability
  • Proximity to New Madrid seismic zone and strict seismic design requirements
  • Foundation loads due to lateral spread resulting from design seismic event
  • Interface with flood control works, including the Missouri floodwall and the Illinois levee
  • Approach spans interface with existing railroad lines
  • Close proximity of exit and entrance ramps to the main structure