COWI was retained by the Halifax Harbour Bridges (HHB), owner of the Angus L. Macdonald Bridge in 1996 to provide expert review of the proposed 1998 widening scheme.
This included the effect on aerodynamic stability of adding orthotropic deck sidewalks to the suspension bridge outside the existing stiffening trusses.
The bridge comprises a 762 m (2,500 ft.) suspension bridge, with main span of 441 m (1447 ft.), and 585 m (1,918 ft.) long approaches. The bridge was constructed in 1955 and was widened from two lanes to three in 1998.
In 2001/2002, COWI was again retained to provide expert advice on the condition of the orthotropic steel deck paving after two or three years of service. In 2003, HHB decided to repave the deck on the approaches. COWI prepared tender documents for the repaving and acted as HHB’s Representative on-site during construction in 2004.
In 2004, HHB retained COWI to evaluate the “health” of the bridge. This was done using our “survey and analysis” technique, which consists of conducting a survey to establish the position of main structural elements and comparing this with a detailed analysis of the bridge as-built and as subsequently modified.
In 2010, HHB entrusted COWI to design the replacement of the roadway deck, floor beams, stiffening trusses and suspender ropes. Beginning construction in 2014, the entire suspended deck was replaced with only night and weekend bridge closures, allowing traffic to continue unimpeded during the day. The scope also included raising the bridge superstructure to accommodate larger vessels passing into Halifax Harbour and installing a main cable dehumidification system, which is the first of its kind in Canada.