The Chicago Transit Authority (CTA) is currently constructing its largest capital investment project to date on Chicago’s North side – Phase 1 of the Red & Purple Modernization (RPM) program!  A major component of the $1.2 billion design-build project is the complete reconstruction of 1.3 miles of four track structure running from Lawrence to Bryn Mawr.  The general contractor, Walsh-Fluor Design Build Team (WFDBT), elected to construct the new superstructure using precast concrete segmental box girders instead of steel or concrete beams.  Utility Concrete partnered with WFDBT and DEAL, a specialty formwork supplier, to fabricate and deliver the precast segments for this historical project.

The precast scope includes fabrication of 1,555 precast segments that are transported to the jobsite via truck and erected by launching gantry – conveniently named the ‘Windy City Gantry’ – utilizing the span-by-span segmental construction method.  The heaviest segment is approximately 100,000 pounds with a 27ft wide deck and 7.5ft box depth.

To meet the project schedule, our casting area was setup with three casting moulds, two for typical/deviator segments and one for pier segments.  DEAL designed the moulds around two unique challenges, a transverse shifting top deck to accommodate alley clearances around the bridge and the ability to change between box sizes so the moulds could produce smaller single-track segments. We also worked with lead superstructure designer SYSTRA IBT to design the segments with mesh and self-consolidating concrete which helped to streamline production operations.  The segments were also designed for the signal, communication, and traction-power systems which required us to precisely locate and cast over 50,000 sleeves and inserts into the precast for connection of these systems in the field.

Delivery of the 841 Stage A segments wrapped up in December 2022 and the remaining 714 Stage B segments will begin delivery in 2024.