Illinois Department of Transportation (IDOT)
AES Services, Inc.
Phase I Design Services
Structural Engineering
Chicago, IL
2017
Ohio Street over North Branch of Chicago River – Feasibility Study
The existing structure consists of two double-leaf trunnion bascule bridges that carry three lanes of westbound traffic and three lanes of eastbound traffic over the North Branch of the Chicago River. Each bridge consists of a variable-length west backspan, a west fixed span over the counterweight pit, two bascule leaves comprising the main river span, an east fixed span over the counterweight pit, and a variable-length east backspan. The structure has an overall length of 354’ (centerline-to-centerline fixed piers; 26’-9” / 31’-9” / 237’-6” / 31’-9” / 26’-3” spans). The overall out-to-out deck width of each bridge is 43’-10”. The movable span superstructure consists of 3” high concrete-filled metal grating supported on W18 steel stringers, built-up transverse floor beams and built-up truss members. The approach span superstructure consists of a 71/2”-thick reinforced concrete deck on W30 steel stringers and built-up transverse floorbeams and cross girders. The substructure consists of reinforced concrete piers and abutments with counterweight pits.
HBM’s Scope:
HBM conducted an in-depth structural inspection, utilizing hands-on assessments and advanced finite element modeling. The study covered gusset plates, truss members, stringers, floor beams, and lateral bracing members. Repair alternatives were meticulously analyzed, considering the intricacies of the movable and fixed framing.
Feasibility Study Highlights:
- Structural Analysis and Rating: Employed advanced finite element modeling to assess dead and live loads, ensuring a thorough understanding of the bridge’s condition.
- Repair Alternatives: Presented three alternatives, ranging from truss member repairs to comprehensive fixes addressing multiple structural elements.
- Recommendations: Prioritized repairs based on inventory ratings, addressing critical elements such as gusset plates, truss members, stringer webs, lateral bracing, and more.
Future Phases: The Feasibility Study, submitted in May 2017, sets the stage for Phase II engineering services. HBM remains committed to delivering sustainable and innovative solutions, aligning with IDOT recommendations for the Ohio Street Bridge’s continued resilience.
