If you are someone who lives in Kolkata, or have visited the place during one of your holidays, then you surely must have seen the Howrah Bridge. A famous symbol of the city and the State, the bridge has connected Howrah and Kolkata from 1943. With a main span of 457 m, the Howrah Bridge was the third-longest cantilever bridge at the time of its construction and currently occupies the sixth spot.
Since the 19th century
Pont de Quebec in Canada with a span of 549 m and Forth Bridge in Scotland with a span of 521 m were the only ones that were longer than Howrah Bridge while it was constructed. And out of those two, the Forth Bridge has stood the test of time longer, as it came into existence in the 19th century…
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Popular crossing
As far back as the 12th century, people were crossing the water at Queensferry by ferries. The regular ferry that connected North and South Queensferry became one of the busiest in Scotland by the 18th century, as it linked Edinburgh and the south with the north east of the country.
The advent of railways and its rapid expansion in the United Kingdom, along with the rising demand for a crossing that would support a larger volume of people, got people thinking about a weather independent means of connecting the two places. While proposals for tunnels were shot down, designs for bridges were submitted and scrutinised as the years passed.
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Bouch’s failure
A proposal by engineer Thomas Bouch for a rail bridge was finally approved and the foundation stone was laid in 1873. That project, however, came to an abrupt end when the Tay Bridge, also built by Bouch, collapsed during a winter storm in 1879, killing an estimated 75 train passengers.
Despite this setback, the desire and need for a new bridge still existed. That provided the space for John Fowler and Benjamin Baker, who submitted their new design for a cantilever bridge to be built of modern steel in 1881. While the concept wasn’t new at that time, it had never been done at such a large scale.
Seven year work
Construction work on this design began in 1883, with factories built on the site to cut and shape the steel, spawning the birth of a new town that housed over 4,500 workers. Even though construction didn’t go on without incident – an estimated 73 people lost their lives during the construction – work went on and it was finally ready seven years later.
On March 4, 1890, the Prince of Wales screwed the last rivet – made of gold to add to the occasion – and the bridge was declared open. He called it a “triumph of science and engineering skill over obstacles of no ordinary kind,” a succinct summary of the work that had been undertaken and executed.
World Heritage Site
The Forth Bridge, which sees more than 200 trains cross it every day even today, has remained open ever since, even though it does require a great deal of maintenance to ensure public safety. It was the longest cantilever bridge when it was built and even now is only outranked by the Pont de Quebec, which was opened in 1919.
In July 2015, 125 years after the Forth Bridge had begun operation, it was designated as a UNESCO World Heritage Site, recognising it as “an extraordinary and impressive milestone in bridge design and construction”. It surely is a triumph of engineering, science and human endeavour.
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Difference between cantilever bridge and suspension bridge
* Cantilever bridge is a bridge that uses projecting beams, which are called cantilevers, to support the main structure.
* Suspension bridge is a bridge that has its roadway suspended from two or more cables. These cables usually pass over towers and are securely anchored at the ends.
* The structure of a cantilever bridge is such that the weight is evenly distributed over the beams, which are anchored to the shore.
* The structure of a suspension bridge is such that there are two sets of cables. While the primary cables are the ones that connect the towers to one another, the secondary cables hang from the primary cables and help keep the roadway in place.