In 1885, a pivotal moment in bridge design history transpired when Fredericton‘s first bridge was inaugurated, extending Carleton Street over the Saint John River.
Historically, the assessment of column strength was primarily based on antiquated lab tests. Many inconsistencies and discrepancies plagued the widely accepted rules and tables used by builders. The design principles for beams were also largely misunderstood. As of 1872, many designers still considered mathematical models for bending as questionable.
Moreover, bridge design was the sole jurisdiction of bridge builders. The owners had minimal influence over the durability or effectiveness of the builders’ designs. Around 1880, this began to shift when owners started taking on a more proactive role, resulting in a so-called “specification disease”.
The early phase of bridge construction was also dictated by the materials at disposal. Timber and masonry were the only materials used for bridge construction until iron was introduced. It wasn’t until the 1880s, after a series of catastrophic bridge collapses, that steel became commonly used, forcing the industry to shift away from iron.
Various bridge designs gained popularity during the early days, one of which was the Burr truss that integrated a timber arch with a timber truss.
Theodore Burr’s design wasn’t ‘engineered’ in the contemporary sense, but it had proven effective and was thus repeatedly employed, becoming a common feature. Many Burr trusses in New Brunswick were part of covered bridges, making their construction and prevalence less evident to passersby.
In 1884, New Brunswick’s Premier, Andrew Blair, resolved to construct a bridge at Carleton Street to connect the city with Alexander Gibson’s industrial and railway conglomerate situated across the river.
Blair’s proposal faced staunch opposition. Critics argued that the bridge would undermine ferry operators, divert traffic from the city’s core, or be swept away by spring floods. Unfazed, Blair remained resolute in his intent to expedite the bridge’s construction. In the fall of 1884, he sought tenders even before securing legislative approval for the necessary funds. He further dismissed the federal government and proceeded without their consent to construct over a navigable waterway.
The project was sarcastically referred to as ‘Blair’s Paper Bridge’. In 1885, inspired by news of the proposed bridge, Mary Pengilly wrote ‘Fredricton Bridge, A Prophetic Warning’ while she was confined in the Provincial Lunatic Asylum. She feared that the proposed bridge could become a dam, and in a situation like the Spring of ’78, it could cause a flood that could decimate the city.
During this period, design methods were evolving, and Premier Blair was in a rush to get the bridge constructed. Therefore, it’s not unreasonable to question the choice of Alfred Haines as the designer, with the superstructure engineered by A.G. Beckwith, and the finalized design executed by Simmons and Burpee. Alfred Haines, hailing from Saint Mary’s, was a second-generation bridge builder with multiple structures to his name. Although not an engineer, he was deemed suitable for the project as he was a provincial staff inspector with connections to talented engineers with bridge knowledge. A.G. Beckwith served as a city engineer in Fredericton. My suspicion is that Haines and Beckwith formulated a conceptual layout, with Haines determining the dimensions of some timbers based on experience and discretion. Haines probably also planned the piers (substructures), as Beckwith is specifically credited with engineering the superstructures (spans). Simmons and Burpee likely created any additional necessary details.
Carleton Street was extended to the waterfront and construction commenced. The stone for the piers was sourced from Spoon Island, and the bridge was inaugurated on November 27, 1885, a mere two years after it was initially proposed. The bridge design included a swing span to allow for boat passage.
Frequent minor fires, often blamed on discarded cigars, erupted on the bridge deck. A full-time attendant was tasked with keeping the deck free of combustibles, so fires were typically small and easily extinguished. However, on the evening of July 15, 1905, a fire broke out that resulted in two spans being destroyed and plummeting into the river within a couple of hours. These spans were replaced with steel trusses, and over the next few years, other spans were replaced until all of the Burr trusses were removed by 1909.
The modified bridge was eventually dismantled in 1982 with the inauguration of the Westmorland Street Bridge. Today, only the piers remain in the river.
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