How Do Cantilevers Support Bridges? | How Did They Build That?
Summary
TLDREste video explora la ingeniería de puentes en varios lugares icónicos. Comienza en Durham, Inglaterra, con el Puente Kingsgate, un puente de doble voladizo diseñado por Ove Arup en 1963. Luego se desplaza a Escocia para examinar el majestuoso Puente Ferroviario de Forth, un logro de ingeniería del siglo XIX con tres grandes voladizos dobles. Finalmente, en Sevilla, España, se presenta el Puente Alamillo, diseñado por Santiago Calatrava para la Expo 92. Este puente atirantado destaca por su pilón inclinado y su estética innovadora, simbolizando la evolución de la construcción de puentes. El video celebra el ingenio y la visión detrás de estas estructuras emblemáticas.
Takeaways
- 🌉 El puente en voladizo es un tipo de estructura sencilla que está fijada en un extremo y se proyecta hacia el exterior.
- 🏗️ La pasarela Kingsgate en Durham es un ejemplo de puente en voladizo que une el campus universitario con el otro lado del río Weir.
- 👷♂️ Ove Arup, ingeniero famoso, diseñó la pasarela Kingsgate en 1963, utilizando un sistema de voladizo doble.
- 🔧 La construcción del puente permitió ahorrar costos al no obstruir el río, con un sistema ingenioso para mover las secciones del puente.
- 🚂 El puente ferroviario de Forth en Escocia es un enorme puente de voladizo doble, con tres grandes voladizos que conectan mediante puentes de celosía.
- 🚢 El colapso del puente Tay en 1879 llevó a la cancelación del proyecto original de suspensión del puente Forth y a la adopción del diseño de voladizo.
- ⚖️ La estructura del puente de Forth es extremadamente estable gracias a su gran peso y sistema de arriostramiento interno que soporta el tráfico ferroviario.
- 🛠️ Los cimientos del puente Forth fueron construidos mediante cajones de cimentación, hundidos en el lecho del río con aire comprimido, sin pérdidas humanas.
- 🌉 El puente Alamillo en Sevilla es un puente atirantado diseñado por Santiago Calatrava, que equilibra el peso del tablero con el contrapeso del pilar inclinado.
- 🎨 Los detalles estructurales y la estética del diseño en los puentes presentados reflejan ingenio y visión, transformando simples cruces en obras maestras de la ingeniería.
Q & A
¿Qué es un puente en voladizo y cómo funciona?
-Un puente en voladizo es una estructura donde un extremo está fijo y se proyecta hacia el espacio. Su peso es soportado por soportes en forma de 'V', lo que permite que la estructura se mantenga en equilibrio sin necesidad de soportes en el centro.
¿Cuál es la importancia del Puente de Kingsgate en Durham?
-El Puente de Kingsgate en Durham es un ejemplo de un simple puente en voladizo diseñado por el famoso ingeniero civil Ove Arup. Fue construido para conectar dos partes de la Universidad de Durham y es notable por su diseño elegante y eficiente, que no interfiere con el río Weir.
¿Cómo se construyó el Puente de Kingsgate sin obstruir el río?
-El puente fue construido a lo largo de la orilla del río y luego fue rotado en su lugar mediante un movimiento único, evitando así la necesidad de construir sobre el río, lo que redujo significativamente los costos.
¿Por qué se inclinaban los soportes del Puente de Kingsgate?
-Los soportes del Puente de Kingsgate están inclinados no solo por razones estéticas, sino también para reducir el número de fundaciones necesarias y dividir el tramo en secciones más manejables.
¿Qué tragedia detuvo el primer intento de construir un puente sobre el estuario del Firth of Forth?
-El primer intento de construir un puente fue interrumpido cuando otro puente diseñado por el ingeniero Thomas Bouch, el Puente de Tay, colapsó, causando la muerte de 76 personas y destruyendo la confianza en sus diseños.
¿Cómo restauraron John Fowler y Benjamin Baker la confianza en la ingeniería de puentes con el Puente del Ferrocarril del Forth?
-John Fowler y Benjamin Baker diseñaron un nuevo puente compuesto por tres grandes voladizos dobles. Este diseño restauró la confianza en la ingeniería de puentes al ser más robusto y seguro que el fallido diseño de Bouch.
¿Cuál es la función de las estructuras de celosía abiertas en el Puente del Ferrocarril del Forth?
-Las estructuras de celosía abiertas funcionan bajo tensión y se combinan con los miembros tubulares que trabajan bajo compresión para crear un sistema lo suficientemente rígido como para soportar el peso de los trenes.
¿Qué elementos de diseño hacen que el Puente del Ferrocarril del Forth sea resistente al viento?
-El Puente del Ferrocarril del Forth utiliza un sistema de contravientos y celosías cruzadas en sus grandes voladizos para resistir el viento, mientras que sus torres se inclinan hacia adentro para mayor estabilidad.
¿Cómo afecta el peso de los trenes al Puente del Ferrocarril del Forth?
-El peso de los trenes es equilibrado mediante un sistema de pesos muertos, como los mil toneladas de plomo que contrarrestan el movimiento de los trenes y evitan que los voladizos se levanten.
¿Qué distingue al Puente Alamillo en Sevilla de los otros puentes mencionados?
-El Puente Alamillo en Sevilla, diseñado por Santiago Calatrava, es un puente atirantado con un solo pilón inclinado que equilibra el peso del tablero mediante cables. A diferencia de los otros puentes, este se destaca por su diseño moderno y asimétrico.
Outlines
🌉 Introducción a los puentes en voladizo y la visita a Kingsgate Footbridge
El vídeo comienza explicando el concepto básico del voladizo, un tipo de soporte que se proyecta hacia afuera desde un extremo fijo. Luego, se introduce el Kingsgate Footbridge en Durham, Inglaterra, diseñado por el renombrado ingeniero Ove Arup en 1963. La construcción fue económica debido a su diseño simple pero eficiente de voladizo doble, con inclinaciones estratégicas en los soportes para maximizar su estabilidad. Arup diseñó el puente como una obra de arte en su ubicación sobre el río Weir, mostrando una estética minimalista combinada con una estructura funcional.
🚂 La construcción del puente ferroviario de Forth
La historia continúa en Escocia, donde se describe el majestuoso puente ferroviario de Forth, un puente de tres voladizos dobles que conecta las orillas del Firth of Forth. El proyecto comenzó a finales del siglo XIX después de varios intentos fallidos, incluido uno que resultó en un trágico accidente. El diseño de Thomas Bouch fue reemplazado por el de John Fowler y Benjamin Baker, quienes idearon una estructura de voladizos dobles de 17,000 toneladas que equilibran las fuerzas mediante una serie de tensiones internas y refuerzos para soportar el tráfico ferroviario.
🏗️ La estructura interna del puente de Forth y sus innovaciones
Se describe cómo los arcos de mampostería en los extremos del puente ferroviario de Forth ocultan grandes pesos de contrapeso que estabilizan la estructura. Los puentes de celosía conectan las secciones del puente principal, permitiendo movimiento y expansión. La ingeniería permite que los puentes de celosía se muevan de forma independiente, mientras que las columnas y las vigas de refuerzo aseguran la estabilidad contra los fuertes vientos y las cargas de tráfico. La construcción del puente, que tomó diez años, fue un esfuerzo monumental, con 57 vidas perdidas durante su construcción.
⚓ Fundaciones del puente y el reto de las cimentaciones bajo el agua
La narración se centra en las cimentaciones del puente ferroviario de Forth, construidas mediante el uso de cajones de aire comprimido. Los trabajadores cavaron a mano bajo el nivel del mar para asegurar los cimientos en el lecho marino. A pesar de las difíciles condiciones laborales, no se perdieron vidas en este proceso. La construcción de las fundaciones fue esencial para soportar las enormes cargas del puente, destacando el contraste con los diseños de puentes suspendidos anteriores, como los de Bouch. Finalmente, el príncipe de Gales colocó el último remache en 1891.
🌍 Innovación en diseño: Puente Alamelu en Sevilla
El vídeo concluye en Sevilla, España, con el Puente Alamelu diseñado por Santiago Calatrava para la Expo 92. Este puente atirantado, con un diseño asimétrico, utiliza un gran pilón inclinado a 58,25 grados que sostiene los cables que equilibran el peso del puente. El innovador uso de acero y hormigón para crear una estructura rígida y ligera ejemplifica los avances en la ingeniería de puentes. El diseño de Calatrava, tanto estético como funcional, ha cambiado la percepción de cómo deberían verse y funcionar los puentes modernos.
Mindmap
Keywords
💡Puente en voladizo
💡Kingsgate Footbridge
💡Cuarto puente ferroviario
💡Ingeniería victoriana
💡Ove Arup
💡Puente de Alamelu
💡Santiago Calatrava
💡Cimientos de los puentes
💡Puente atirantado
💡Bracing
Highlights
Introduction to the concept of a cantilever bridge, explaining its basic structure and function.
Discussion of the Kingsgate footbridge in Durham, emphasizing its simple double cantilever design.
Details on the engineering and aesthetic balance of the inclined supports on the Kingsgate footbridge.
Insight into the design process where the bridge was constructed along the bank and then moved into place over the river.
Explanation of how the bridge's halves are structurally independent, enhancing its flexibility.
Comparison of the Kingsgate footbridge to larger cantilever bridges, like the Fourth Rail Bridge.
Overview of the historical context of the Fourth Rail Bridge, highlighting the tragedy of the Tay Bridge collapse.
Introduction to the Fourth Rail Bridge’s vast double cantilever structure, which was a response to earlier engineering failures.
Focus on the construction technique of the Fourth Rail Bridge, using tubular members for compression and open lattice girders for tension.
Description of the massive pig iron weights used to balance the cantilever sections of the Fourth Rail Bridge.
Exploration of the bridge's ball-and-socket joint design that allows for movement and expansion.
Historical insight into the human cost of building the Fourth Rail Bridge, with 57 workers losing their lives.
Transition to modern bridge design with the Alamillo Bridge in Seville, showcasing a cable-stayed system.
Explanation of the Alamillo Bridge's asymmetrical design, with a single inclined pylon supporting the deck through tensioned cables.
Highlight of the innovation in modern bridge design, contrasting older massive structures with new lighter materials and designs.
Transcripts
you
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a cantilever is the simplest of all
supports like a bracket supporting a
bookshelf a cantilever is fixed at one
end and projects outwards into space
it's an obvious technique for building
bridges in this program we travel to
Scotland to see the bold Victorian
engineering of the fourth rail bridge
then fly to Seville Spain to see the
outlandish Alamelu bridge but we start
our story at the elegant Kingsgate
footbridge in Durham northeast England
here in Durham where the river Weir
loops around the great Cathedral there's
an outstanding example of the simplicity
of the cantilever bridge in the
Kingsgate footbridge in 1963 the
university wanted to build a link to the
extension of the campus on the other
side of the river they had little money
but they thought it might stretch to a
span from bank to bank of course being
in a gorge that would have meant the
students having to walk all the way down
one side and all the way up the other
the university commissioned over up one
of the greatest civil engineers of the
20th century born in Newcastle of
Scandinavian parents Arab came to
engineering from philosophy the
Kingsgate footbridge was the last great
structure that he designed himself and
its success in such a dramatic and
sensitive setting is a testament to a
remarkable career Arab solution was a
simple double cantilever bridge spanning
right across the top of the Gorge the
deck acts as a beam and the whole weight
of the bridge is carried down the
supports inclining the supports is not
merely for aesthetic reasons it means
there are any two foundations
and it divides the span into four
sections in the words of the designers
the bridges like a thin taut white band
stretched across the valley resting on a
pair of slender tapered fingers in a
v-shape rising from each bank of the
river the best way to see how the
cantilever principle applies to the
bridge is to look up at the supports
from below this is half of the bridge
like this and the weight of the deck is
supported on two twin supports like this
which come down to the foundation
the weight of each end of the deck can't
leave it off the end here from the
supports is balanced by the weight at
the other end and the weight of the
whole deck is carried down to the
foundation it's a double cantilever and
this is one half and it's exactly
balanced by the weight of the other half
this is the base of one of the two
double cantilevers of the bridge with
its foundation block below each of the
two foundations supporting the bridge
have these great v-shaped supports with
two fingers on each which stretch away
to the deck above beautifully designed I
paid a huge amount of attention to the
detail in the design every line
carefully laid out the bridge was
actually constructed this way along the
bank of the river over the bank so there
was no need to obstruct the river at all
making it a lot cheaper and then it was
turned out to the river like this in a
single movement and it was brilliant
really because inside here were two
cones one on top of the other with the
outer one turning like this ninety
degrees just once and the two spans
meeting in the middle and then this was
grouted up through holes so that it all
became a solid lump and the bridge looks
wonderful today I'm standing here at one
end of the double cantilever each of the
two halves of the bridge is completely
structurally independent of each other
it's much more flexible than it would
have been if it was all rigidly
connected together a large group of
schoolchildren have just walked across
and you can
really feel the bridge moved quite
perceptibly the deck of the bridge is
like a u-shaped beam with each of the
sidewalls providing a lot of the
strength inside the walls which are
called the flange of the beam there's
steel reinforcement and in the floor
underneath the paving stones there's
more reinforcement to help the beam
carry the weight of the people in
bending the genius of Eric's bridge was
to achieve this beautiful solution for
the same budget that the university had
set aside for a simple bridge across the
bottom of the gorge the Kingsgate
footbridge clearly illustrates how
dividing up a span into sections can be
an ideal solution to bridging a gap but
this is an example of the cantilever on
a small scale
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the colossal fourth rail bridge spans
the Firth of Forth near the Scottish
capital city of Edinburgh the bridge is
made up of three huge double cantilevers
connected by girder bridges and at the
time of its construction was the biggest
bridge in the world the ambition to
cross the Firth of Forth has existed for
centuries the direct route across the
ester II is just a few miles but
conditions in winter in particular can
be pretty rough and treacherous the
alternative is a long detour maybe 50
miles around the shore as the railways
expanded in the 19th century it became
increasingly important to construct a
permanent crossing passengers and
freight had to transfer from the
railways to a ferry to cross over and it
was very time-consuming and expensive as
early as 1805 there were proposals for a
double tunnel quaintly described as one
for the comers and one for the goers but
that plan wasn't feasible but it wasn't
until the middle of the century that the
railway companies finally decided to go
ahead and let a contract to the
country's foremost bridge engineer
Thomas Bouch pouch began work on a huge
double suspension bridge but soon after
the start work came to an abrupt and
tragic halt when another of his bridges
Fateh bridge collapsed a busy passenger
train plummeted into the Tay and 76
people were killed faith in badge
evaporated and the project was abandoned
Bouch died a year later the ambition to
cross the fourth did not die with him
however and in 1882 some 10 years later
a new bridge contract was awarded to
John Fowler and Benjamin Baker the two
were leading civil engineers and they
began work on a different bridge design
two batches double suspension bridge
instead they opted for three vast double
cantilevers and with this new design
they said about trying to restore
confidence in the railways
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each of the three huge double
cantilevers of the fourth rail bridge
weigh around 17,000 tons and are
immensely stable because of their great
self weight each of the huge cantilevers
needs a system of bracing internally to
make it stiff enough to carry the weight
of the railway traffic the bracing is
very simple the solid tubular members
work in compression and the open lattice
girders work in tension and together
they form a system which is stiff enough
to take the weight of the trains
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at each end of the bridge masonry
archers disguise a thousand tons of pig
on waiting down the end of the
cantilever against the weight of a train
and the girder bridge is trying to tip
it up
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this is where the girder bridge
connecting the South Queensferry
cantilever meets the main central
cantilever at inch garvey these standard
girder bridges were used to keep the
size of the main cantilevers as small as
possible and it's here that we can see
how the bridge accommodates movement and
expansion the sheer size of the bridge
it's a mile long means that the wind can
blow on one end and not on the other so
it's essential that the cantilever is
connect independently of each other a
bit like the carriages on a railway
train
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this is the end of the girder bridge and
there's a gap between it and the
cantilever here the girder bridge
actually hangs off the cantilever on a
ball-and-socket joint like this so it
can move backwards and forwards but the
girder bridge can also twist sideways
relative to the cantilever like this
around this pin here and another one at
the top
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we're going out to the double-o here on
let me to get out and see the top of the
fridge for juice they're sending one of
the big tubular columns it's not
particularly windy today it's only
gusting to about 50 miles an hour
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you can see clearly the cross-bracing in
between the poems behind me
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the top of the towers are nearly 400
feet above the sea that's over a hundred
metres and you can see them sloping
together to provide stability but the
main stability against the wind is in
the cross bracing that you can see
beneath me here in between the towers
we came up the easy way of course we
came up the lift but when they were
building it they would have had to come
up the tubes themselves every day
thousands of men working their way up
riveting the the bridge in sections
assembling it building these lattice
girders standing and walking along these
girders without the sort of protection
that I've got here today
fifty-seven men died building this over
ten years it was a big human price
really
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off
thanks love late great
so the ten around then we'll head out
that way
this is essential Puritans garmi for
huge foundations for the 17 18 thousand
tons of steel work above us these
granite blocks are there to to protect
against the waves of course dan Valois
is the enormous casein foundation
concrete filled which was floated out in
sunken position here compressed air to
create a working space men went down
below the sea level below the sea bed
and they hand dug the foundations
sinking the casein into the seabed
amazingly no men were lost at all in the
in the thinking of the caissons and the
construction of the foundations men were
sick of course because it was horrendous
working conditions down there and
working under the seabed in the winter
very difficult indeed when they finished
that they would fill the casing with
concrete facing it with these granite
blocks to form this enormous foundation
this is all that remains of one of
bouches piers for his suspension bridge
crossing faced in brick it's quite a
different design to the granite facing
of our bridge here other side really the
last rivet was hammered in on the 4th of
March 1891 by the Prince of Wales the
bridge had taken 10 years three million
pounds that's about 200 million pounds
today and cost 57 lives but they had
achieved the crossing and with the
greatest railway bridge in the world and
it did restore faith in the railways and
in British engineering and it remains
one of the world's most famous
structures nearly 200 trains a day still
use the bridge today new Steel's
allow designers to create bridges that
are lighter in weight and easier to
build nothing epitomizes that more than
our next bridge
one of the primary functions of the
fourth rail bridge design was to restore
confidence in bridge engineering the
bridge looks like it will stand forever
but in Seville Spain there is a bridge
that challenges notions of what a bridge
should look like
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this is Spanish engineer Santiago
Calatrava
dynamic 20 Dalila me low on the
Guadalquivir River it was completed in
1992 for Expo 92 a festival celebrating
Commerce and Industry and is a fantastic
example of a cable-stayed bridge it
works on the same principle as the
cantilever bridge but in this bridge the
support for the deck comes from the
tension of the cables above and the
counterweight of the great pylon also
unlike the two bridges we've already
seen the Alamelu bridge is a symmetrical
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santiago calatrava was born near
Valencia where he studied architecture
he also read civil engineering and it's
his extraordinary ability to combine
structural form with architectural
qualities that has marked him as one of
the foremost engineers of the late 20th
century the cable-stay bridge has
actually been around for centuries and
many early bridges had cable-stayed
elements the concept is simple but it's
difficult to analyze which kept the
bridge in the wings until modern
materials and analytical techniques
realized its potential it's now one of
the most favored bridge forms of all
it's not the 200 metres span of the
Alamelu which strikes you it's the great
single pylon leaning at what seemed like
an outrageous angle but it's this
apparent instability which is the key to
the bridges success the enormous pylon
stands at an angle of 58 and a quarter
degrees and supports 13 pairs of
parallel cables which run down to the
deck like harp strings the weight of the
deck is exactly balanced by the weight
of the pylon so there is no need for a
second set of cables at the back to
anchor it
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inside it's just like a ship miles of
Steel staircases until they get smaller
at the top
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the tower was built by welding steel
plate to form two tubes one inside the
other
and were right inside the center of the
tower and the gap between them which is
up to two meters was filled with
concrete creating a composite structure
where the concrete gives the tower mass
and stiffness and the steel gives it
strength this is one of the welded
joints between the steel plates
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finally at the top
the bridge was meant to be a landmark
drawing you over the river to the Expo
site on this side the top of the bridge
is a hundred and fifty meters above the
ground and the cables stretched down to
the deck below the concrete is heavily
reinforced at the base and where the
cables are anchored to the tower under
the bridge the cables are fixed on
either side of the spine of the deck
into special Anchorage's
a critical feature of the cable-stay
bridge is its rigidity it would buckle
upwards under the huge forces from the
cables pulling it back to the tower
behind me or twists sideways under the
weight of traffic if it wasn't
restrained properly to achieve this the
spine of the bridge where the walkway is
is a huge hollow hexagonal steel box
girder which has excellent torsional or
twisting rigidity the roadways on either
side are cantilevered off steel ribs at
4 meter centers like a fishbone
here under the spine of the bridge we
can see the depth of the central girder
and the ribs on either side much more
clearly in design it's not just the
grand form that's important but the
details and these holes in the deck and
in the ribs above let the Sun through to
the water and lighten the whole
appearance of the structure
Crossing bridges is an everyday
experience and yet often they're
utilitarian anonymous structures which
we scarcely notice the common
denominator of successful engineering
design is thought ingenuity and vision
transformed all these structures from
what they could have been to what they
are in next week's program we look at
domes we start our story at
Brunelleschi's famous Duomo in Florence
then travel to Paris to explore the
extraordinary canet building and catch
work in progress at the Millennium Dome
in London
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