LESSONS LEARNED FROM THE NAIRN AVENUE OVERPASS CONCRETE GIRDER PIER REPAIRS

摘要

The Nairn Avenue Overpass is a 213 m long, 11-span, 4-lane + sidewalk precast prestressed concrete I-girder bridge over the CP Keewatin Subdivision line in Winnipeg, MB. The superstructure consists of three continuous segments with deck joints at piers #3 and #8. The structure was built in 1967, and underwent major strengthening and rehabilitation of the deck, girders, and bearings in 1985. Piers consist of a cast-in-place pier cap approximately 18 m long supported on two cast-in-place columns approximately 7 to 8 m tall supported on concrete pile caps over timber raft-pile foundations. Leaking omega-style strip seal deck joints at Pier #3 and Pier #8 have exposed the piers and girder ends to chloride contaminated run-off from the deck. In 2002, the pier caps were re-faced on three sides and provided with galvanic anode cathodic protection, and the pier columns received local patch repairs only. In 2014, during a deck rehabilitation project that included rehabilitating the deck joints, Morrison Hershfield (the Consultant) noted significant deterioration of pier column concrete including staining, moderate-to-severe cracking and localized spalling. The Consultant was subsequently engaged by the City of Winnipeg (City) to conduct a field investigation to quantify the degree of deterioration, evaluate alternatives, and undertake design and construction administration of the preferred solution. This presentation describes these steps, and lessons learned from the Contractor, Consultant, and Owner's perspective.