Collins performed the erection engineering for the removal of the existing bascule bridge and replacement tied arch bridge over the North Branch Canal of the Chicago River.
The waterway is heavily silted at this location, making access via barge impossible. Collins devised a scheme to drive temporary support frames into the river to support the erection of the bridge. The same temporary supports were used to jack the tie strut and arch structure so that the chord suspender cables could be installed and adjusted for proper tension. Collins modeled the entire bridge in SAP to determine the forces during erection, develop hanger tensioning procedures, and verify the analysis. Collins noted problems with the box member welding details and recommended modifications be made to ensure that fatigue performance of the completed structure was not compromised.