Angus Macdonald Bridge Suspended Spans Deck Replacement

Built in 1955, the 762m (2500′) Angus Macdonald Suspension Bridge is a vital link between the communities of Halifax and Dartmouth, Nova Scotia. In 2014, Halifax Harbour Bridges (HHB) awarded the contract for a full replacement of the suspended spans to American Bridge. The superstructure replacement work was completed in 10m (32′) and 20m (65′) orthotropic deck truss segments. The old thru-truss deck segments were cut away, lowered to a waiting barge, and the new segment raised and installed, all during a limited closure window. American Bridge accomplished this with a custom lifting gantry fitted with strand jacks, temporary deck connection (to maintain continuity of the stiffening truss), and custom cantilevering falsework mounted on delivery barges that enabled positioning of the segments over the tower islands. American Bridge developed a 57 step procedure for replacing each segment, with individual durations ranging from 10 minutes to 3 hours. Constantly changing loads were accurately calibrated and distributed through retensioning of suspender extensions after each lower and lift.

Other work included the replacement of 148 hanger assemblies, installation of new handstrands, replacement of six cable bands and 192 cable band waisted rods, and the addition of a dehumidification system for main cables.

The bridge remained open to commuter traffic during normal weekday hours when traffic was the heaviest. American Bridge utilized weekend closures to replace two deck segments a weekend, finish the paving of the Dartmouth side span and the main span, and open the bike lane and sidewalk by the end of 2016, enabling completion of the Halifax side span by 2017. This was only the second time that the suspended spans of a suspension bridge was replaced while keeping the bridge open to traffic. The first was completed by American Bridge on the Lions Gate Bridge in 2002.