Hall’s Harbour Wharf, Nova Scotia

Vaughan Engineering/MacDonnell Group

Category: Transportation Infrastructure

After a stormy night in February 1998, the people of Hall’s Harbour off the Atlantic coast in Nova Scotia woke to find the mid-section of their breakwater wharf had collapsed. This is the only safe harbour on the Fundy Shore north of Digby that is open throughout the winter months, so there was an urgent need to rehabilitate the 1904 timber structure.

The reconstruction of the wharf resulted in Canada’s first marine structure that uses glass fibre reinforced polymer (GFRP) reinforcing. GFRP is lightweight and corrosion- free.

The community had limited funds for the repair, and were drawn to new technologies. Preliminary design work by Vaughan Engineering and a team from ISIS Canada in Halifax showed that the additional cost of using GFRP reinforcement and a steel free deck compared to conventional steel reinforced concrete was only $20,000, or 4.5% more.

The long-term benefits, however, are substantial because the absence of steel reinforcements extends the life of the wharf from approximately 30 years to between 80 and 90 years with minimal maintenance.

The reconstructed 40-metre mid-section of the wharf blends aesthetically with the existing wharf but is a meter higher to alleviate flooding problems during extreme high tides. It is in a modular design so that new sections can be easily added when funding allows.

Completed in December 1999 as a demonstration project, the wharf incorporates a number of new technologies. It is constructed with concrete deck panels on deep corner beams spaced at approximately four metre intervals. The transverse beams are supported on piles, which are a steel-free concrete core encased in a GFRP jacket. The jacket provides reinforcement against bending as well as circumferential confinement that is necessary for adequate performance.

The pile caps and bents contain some steel reinforcement, though the reinforcement in locations under low service stresses is GFRP rods.

The deck panels contain synthetic fibre reinforced concrete and use an internal compressive arching technology. The panels also contain GFRP rods to reinforce them against the uplift force of waves during severe storms.

To monitor the wharf’s behaviour and general health, ISIS Canada has installed fibre optic sensors embedded in glass rods (a newly patented Canadian technology), along with traditional strain gauges at critical junctures.

Most of the research around the globe in innovative technologies to improve the durability of concrete structures exposed to corrosive environments has concentrated on land-based civil engineering structures such as bridges. However, deterioration of marine infrastructure is also an important problem. With an average daily tidal range of 10 metres, Hall’s Harbour is in a critical zone where corrosion is most likely to occur, and thus was an ideal site for demonstrating the durability of lightweight GFRP reinforcing in marine environments.CCE

Project name: Hall’s Harbour Wharf, Nova Scotia

Award winner: Vaughan Engineering/MacDonnell Group, Halifax (prime consultant).

Project team leaders: Ralston E. MacDonnell, P.Eng., Michael Williams, P.Eng., (Vaughan Engineering); John Newhook, P. Eng. (ISIS Canada), Dr. Aftab A. Mufti (Daltech)

Client/Owner: Harbour Authority of Hall’s Harbour

Other key players: Nova Scotia CAD/CAM Centre (structure), ISIS Canada (sensing), JMBT Structures Research Inc. (design concepts), Waterworks Construction (contractor), CAN/ACM Consultants, St. Lawrence Cement, Forta Corporation, CH2M Waterworks, Shaw Pipe, Pultrall Inc.