The Longbird bridge in Bermuda, a swinging asymmetrical steel span, was built across Castle Harbor by the US Navy in 1953 to facilitate movements to St. David’s Island near the Kindley Naval Air Station (now the Bermuda L. F. Wade International Airport). The US Navy maintained a military presence in Bermuda from the 1940’s to 1995 and constructed many structures as part of its operations, including the Longbird Bridge. Due to the high chloride environment, hot-dip galvanized steel reinforcement was used in the concrete approach and bridge deck.

Over the nearly seven decades the Longbird Bridge stood, several inspections and corings were conducted to evaluate the performance of the hot-dip galvanized (HDG) rebar used in the bridge deck. In each of the studies, the average galvanized coating thickness was measured and found to exceed the requirements for newly galvanized rebar despite being exposed to a highly corrosive, tropical marine Bermuda environment. The bridge was exposed to heavy salt-spray from tidal splash zones and was constructed in very close proximity to the ocean water.

In 1995, when the bridge was 42 years old, the HDG rebar coating thickness was in excess of the requirement for newly galvanized rebar even though the chloride levels were 3-10 lbs/yd3, well beyond the threshold limit of 1.1 lbs/yd3 for black rebar. In 2020, after the bridge had been demolished, analyzed rebar samples also showed HDG coating thickness in excess of the requirement for new galvanized rebar after 67 years of service.

The performance of the Longbird Bridge led Bermuda’s Ministry of Works and Engineering (MW&E) to exclusively specify hot-dip galvanized reinforcement in future bridge projects for more than 50 years. If it were not for damage from multiple hurricanes over the years, including the devastating final blow delivered by Hurricane Fabian in 2008, the Longbird bridge would have provided service for well over 100 years.

Coating Thickness