How Do Cantilevers Support Bridges? | How Did They Build That?

Summary

Este 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

00:00

🌉 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.

05:02

🚂 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.

10:04

🏗️ 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.

15:06

⚓ 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.

20:13

🌍 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.

Keywords

💡Puente en voladizo

Un puente en voladizo es una estructura que se extiende hacia afuera sin soporte intermedio, estando fijo en un extremo. En el video, este concepto es central para comprender cómo se diseñaron varios puentes, incluyendo el Kingsgate Footbridge y el Puente Forth Rail. En el Puente Forth Rail, se utilizan grandes voladizos dobles que conectan secciones a través del estuario del Forth.

💡Kingsgate Footbridge

Este es un puente peatonal en Durham, Inglaterra, que fue diseñado por Ove Arup. Se presenta como un ejemplo de la simplicidad y elegancia de un puente en voladizo, donde el peso del puente se distribuye entre dos soportes inclinados. Es una muestra de cómo el diseño económico y estructural puede ser innovador y eficiente.

💡Cuarto puente ferroviario

El Cuarto Puente Ferroviario es una estructura monumental en Escocia que cruza el Firth of Forth. Se menciona en el video como un ejemplo de ingeniería victoriana, construido con tres grandes voladizos dobles. Este puente representó un hito en la restauración de la confianza en los ferrocarriles y la ingeniería británica después de la tragedia del puente Tay.

💡Ingeniería victoriana

La ingeniería victoriana se refiere a los logros técnicos durante la era victoriana (siglo XIX). En el video, se menciona en relación con el Cuarto Puente Ferroviario y cómo esta estructura muestra la ambición y el ingenio de los ingenieros de la época, como Fowler y Baker, que trabajaron en su diseño y construcción.

💡Ove Arup

Ove Arup fue uno de los ingenieros civiles más destacados del siglo XX. En el video, se le menciona por diseñar el Kingsgate Footbridge, que fue su última gran estructura. Su habilidad para combinar simplicidad y funcionalidad se refleja en este puente en voladizo que cruza el río Wear en Durham.

💡Puente de Alamelu

Este es un puente atirantado diseñado por Santiago Calatrava sobre el río Guadalquivir en Sevilla, España. Contrasta con los puentes en voladizo mencionados previamente, ya que usa un sistema de cables tensados y un gran pilón inclinado como soporte principal. Se completó en 1992 y es un ejemplo de cómo la ingeniería moderna desafía las ideas tradicionales de lo que debe ser un puente.

💡Santiago Calatrava

Calatrava es un ingeniero y arquitecto español conocido por su capacidad para fusionar estructura y estética. En el video, se menciona por su trabajo en el Puente de Alamelu, donde su diseño incorpora un gran pilón inclinado y cables tensados, desafiando las nociones convencionales de estabilidad estructural.

💡Cimientos de los puentes

Los cimientos son esenciales para la estabilidad de cualquier puente. En el Cuarto Puente Ferroviario, los cimientos se lograron usando grandes bloques de granito y caissons (cajones) llenos de concreto que fueron hundidos en el lecho del río. Los cimientos robustos permiten que el puente soporte cargas pesadas y resista las inclemencias del clima.

💡Puente atirantado

Un puente atirantado es una estructura donde el peso del puente se sostiene mediante cables tensados. Este tipo de puente se menciona en el video a través del Puente de Alamelu, que utiliza un pilón inclinado y cables que se estiran hacia el puente, equilibrando el peso de manera efectiva.

💡Bracing

El bracing (entramado de refuerzo) es una técnica de ingeniería utilizada para proporcionar rigidez y estabilidad a una estructura. En el Cuarto Puente Ferroviario, se utilizan tubos y rejillas de acero para formar un sistema de refuerzo que soporta el peso del tráfico ferroviario y las fuerzas del viento, asegurando la estabilidad del puente.

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

[Music]

[Music]

[Music]

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

[Music]

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

[Music]

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

[Music]

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

[Music]

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

[Music]

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

[Music]

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

[Music]

you can see clearly the cross-bracing in

between the poems behind me

[Music]

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

[Music]

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

[Music]

[Music]

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

[Music]

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

[Music]

inside it's just like a ship miles of

Steel staircases until they get smaller

at the top

[Music]

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

[Music]

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

[Music]