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12 CTA RPM Project.jpg

Red Purple Modernization (RPM)


Date of Performance:



Completion Date:


Project Location:

Cook County, IL



Chicago Transit Authority (CTA)


Project Role:

Structural Engineering Design Services


Garza Karhoff Engineering (GKE) provided structural engineering design services for the design of foundation replacements at Montrose Ave Bents 7093& 7094 in Pre-Stage (A09C) of CTA’s RPM Project. Existing wedding cake foundations were replaced with micro-pile supported footings. The existing columns were cut off approximately 2.5’ above the adjacent sidewalk level, fitted with new base plates and supported on reinforced concrete pedestals. New longitudinal beams (stringers)were added to support proposed Montrose Interlocking Crossovers between North Mainline bents 7086 and 7089 and between 7097 and 7100. In existing condition, there are 8 longitudinal stringers supporting 4 tracks (2 stringers under each track). Additional stringers will be added to support the crossover track. Scope of work included design of structural connections and checking of the open deck superstructure


GKE provided structural engineering design services for the design of the substructures and structural connections and checking of the superstructure oft he open deck track structure. GKE worked on multiple contracts, performing analysis and design for new footings per AREMA and CTA criteria at Montrose(A09C), for the temporary structure for RVT(B06), and the new open deck structure (B07). Additional key tasks included designing foundations using micro-piles, checking analysis and design of the open deck superstructure, designing and detailing column splices and beam connections (B09), and responding to contractor’s requests for alternative span arrangements.


GKE provided structural engineering design services for detailing the staged removals of the existing viaduct and its foundations. The LBMM project area begins north of W. Leland Avenue and continues north to a point approximately300 feet north of Ardmore Ave. The four CTA tracks within the project area run in an elevated corridor located between N. Broadway on the west side and N. Winthrop Ave. on the east side. There are four existing stations within the area which were demolished and replaced with new stations. Some of the key tasks included detailing staged removals of the existing viaduct foundations for LBMM (D18). Multiple detail options for removal limits to these foundations were presented to the contractor. Coordination between retaining wall demolition, temporary shoring, station design with staging, and the contractor’s staging were implemented. Accommodations took account of an engineered barrier, temporary platform foundations and future station footings at Lawrence, Argyle, Berwyn and Bryn Mawr. Other responsibilities required performing site visits to verify existing plans


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