The World’s Longest Bridges | The B1M

For centuries, bridges have helped us cross
geological features – such as rivers, canyons or rugged terrain – and in modern times we’ve
seen them integrated into cities and our infrastructure networks with an almost endless array of uses. From humble beginnings, these structures have
grown into some of the greatest engineering achievements in human history. Here we look at the longest bridges in the
world. To develop this list, we’ve looked as the
longest bridges in each of the five main bridge categories and used “continuous span”
to define their length. As a result, elevated highways or causeways with regular supports
along their lengths are not included. First up is the Ikitsuki Bridge, a truss structure
built in the Nagasaki Prefecture of Japan, that links the island of Ikitsuki to its larger
neighbour Hirado. Constructed in 1991, the 400m (1,312ft)
steel span bridge supports itself through a system of interconnected steel beams that form the
triangular trusses of its superstructure. These elements carry either compressive or
tensile stresses with the counteracting actions on each individual member allowing the bridge
to distribute weight evenly when carrying dynamic loads such as vehicle traffic. Being one of earliest forms of modern bridges,
truss designs are often incorporated into other bridges due to the considerable loads
they can carry for the material they use. Next we have the Pont de Quebec, or Quebec
Bridge in Canada. This steel structure takes the title of longest cantilever bridge in the world with its impressible 549m (1,801ft) main span. Completed in 1917, the bridge was dogged
with misfortune throughout its construction, collapsing not once, but twice before it was
opened to the public. The first collapse was the result of improper
calculations relating to the bridges weight and overall load bearing capacity. In 1907,
four years after construction began, the southern and central spans collapsed into the St Lawrence
River, killing 75 workers. After going through a re-design, a second
iteration of the bridge was commissioned and began construction in 1913 with an even longer
central span than its predecessor. This time the bridge was overseen by three
engineers, including an expert who had worked on Scotland’s Forth Bridge. However, these precautions didn’t stop the
bridge from experiencing its second disaster. In 1916, the hydraulic mechanism hoisting
the central span into position failed and bridge fell into the river below, taking a
further 13 workers with it. To this day, the collapsed section still lies at the bottom of the St Lawrence River. When the bridge was finally completed in 1917
– after almost two decades of construction – it took the prestigious title of “world’s
longest bridge”. Despite losing that title in the decades
that followed, the Quebec Bridge remains to this day, the longest cantilever bridge in
the world. Arch bridges are one of the oldest types of
bridge and come in a wide variety of forms. From the early stone arches used by the Greeks
and Roman, to the steel giants of today. The longest of these, with a central span
of 552m (1,811ft) is the Chaotiamen Bridge in China. Built in 2009 the road and rail bridge stands 142m above the Yangtze river with a total
length of 1,741m (5,712ft). Despite varying greatly in appearance, arch
bridges are all based on the same engineering principle of distributing loads from the centre
of the structure outward into abutments at either end. This can be done through foundations or pylons,
like with the Sydney Harbour Bridge, or the earth itself as is the case with the Mike
O’Callaghan-Pat Tillman Memorial Bridge, in the United States. With a main span of 1,104m (3,622ft) the Russky
Bridge in Vladivostok was built to connect Russky Island to the Russian mainland ahead
of the 2012 APEC summit. With its total length exceeding 3,100m (10,200ft)
The Russky Bridge needed some of the tallest pylons of any bridge in the world in order
to carry it’s remarkably long road decks. Reaching 321m (1,053ft) into the air, the
bridges two massive pylons are taller than New York’s Chrysler Building. From these towers 168 cables, some as long as 580m reach out to support the 4-lane roadway below. Controversially, the bridge was built at an
estimated cost of USD $1.1BN with a capacity to carry 50,000 cars every day. However, with
the population of Russky Island at just over 5,000 people, the bridge is severely underutilised and considered by many Russians to be a white elephant. All of the world’s longest bridges use the
suspension principle and the longest of these is a true titan of engineering. With a central
span of almost two kilometres, the 1,991m (6,532ft) Akashi Kaikyo Bridge in Kobe, Japan
is the longest bridge in the world. Built over the course of a decade – between
1988 and 1998 – the bridge was developed to address a range of issues. The Akashi Strait is a major shipping lane
that is notorious for severe storms, so any fixed crossing had to avoid large numbers
of supports across the channel. On top of this, the bridge lies in one of the world’s
most seismically active zones; the “Pacific Ring of Fire”. To overcome these challenges, engineers developed
a structure that was able to span the vast distance whilst being able
bend and flex without suffering serious structural damage. The roadway is hung from vertical suspension
cables attached to the main cables strung between the bridge’s two supporting towers.
These cables are anchored in the bedrock at each end of the structure. Originally designed with a main span of 1,990m,
the city of Kobe experienced a 7.2 magnitude earthquake in January 1995 while the bridge
was still under construction. The resulting ground shift pushed the bridges
two supporting towers apart resulting in an additional meter (three feet) of roadway being
added to the structure to complete the deck. A dual-hinged stiffening girder system and
tuned mass dampers in each of the two support towers of the bridge mean it can withstand
286kmh (178 mph) winds and earthquakes measuring as high as 8.5 on the Richter Scale. Built at a cost of USD $3.6BN the Akashi Kaikyo
Bridge remains one of the most expensive bridges ever constructed. Of course we couldn’t end this video without
recognising some of the former record holders, and most famous bridges from around the
world. Stretching 1,280m (or 4,200 feet), the Golden
Gate Bridge in the United States was the world’s longest between 1937 and 1964. Sydney Harbour Bridge in Australia was the
world’s widest between 1932 and 2012 – with a width of 48.8m (169ft). And the Millau Viaduct in France remains the
world’s tallest bridge to this day, with pylons standing 343m above the ground. If you enjoyed this video and would like to
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