Richard Hammond's Engineering Connections | S02E05 - The Millau Bridge | DocumentaryHub

this bridge is monumentally huge not this bridge that bridge deep in the South of France

the stunning Miller bridge is a record breaker these tapering concrete Giants are the tallest piers ever built from the top you would look down on the Eiffel Tower

driving above the clouds you cross the longest cable-stayed bridge deck on earth spanning the deepest Canyon in Europe each year this spectacular

engineering achievement faces extremes of wind and heat in a valley no one thought could ever be conquered but it

wouldn't be standing here today without and the power of lightning find a lost

nuclear submarine an accident in the silver mine and a crafty trick of ancient Celtic boat booms

how did all those make that possible this triumph of engineering and design lies in the massive central mountains of southern France it was built to lift a

curse on a tiny town of Leyland for 30 years the auto route linking Paris to the beaches of the Mediterranean sped south through the

French countryside until it hit this the town Valley a two and a half kilometre wide 250 meter deep gorge or in

technical terms a very big gap to cross this gap the tourist traffic was diverted off the four-lane Express route and funneled over me last tiny two lane medieval bridge

summer in Mina was a nightmare gridlock traffic with three hour tailbacks an

18-mile cubes after three decades of mayhem it was time to conquer the gorge and so in 2004 the world's tallest Road

bridge was born a giant span a quarter of a kilometer [Music]

the final lightweight steel design was the engineering equivalent of a curved port because the road is not straight it arcs as it spans across the valley the

been designed to keep drivers alert meant that for the engineers it was not going to be simple to build they needed a complex skeleton of over 2,000

individual parts cutting that much steel quickly and accurately would mean that have to master one of nature's greatest forces but first to get the inside angle

on the jigsaw of steel that makes up the deck security have granted me special access this in case you haven't guessed is the tunnel inside the deck so right

now we're sandwiched between the road up above and then well nothing below and from inside you can see just how clever it is it's hollow they worked very hard

to make it strong and light and to do that they leave thousands of pieces of Steel that had to fit together precisely in a massive jigsaw to make the curve of

the deck and each of those pieces of steel had to be made individually and in record time and there's the challenge how to cut

2078 giant pieces of shaped steel with incredible precision phenomenally fast the traditional way to cut steel is with

one of these an oxy-acetylene thought it works but it's not fast and it's not even painstakingly slicing over 2,000

steel panels with oxy-acetylene was a potential nightmare for the engineers especially with the 25,000 euro penalty but every day's delay if they weren't

seriously over schedule so for the solution to their cutting challenge they harness the power of lightning a bolt of

lightning is an electric current that can generate up to 300,000 amps that's enough to power 24,000 domestic counters more importantly when a lightning bolt

arcs through the atmosphere it literally changes the world it produces a new state of matter and it's the key to

cutting steel quickly I'm about to see here first I'm going to control

lightning this machine belongs to a special-effects expert he's going to help me become a human lightning rod and

direct a scary amount of power mark Turner is my lightning wizard Wow mark this is like walking onto the set of a 1950s beam do you like it it's brilliant I think what is it it's a lightning

machine so I call a Tesla coil okay it produces lining what I'd like you to do is to put this on I'll get dressed you do here dressed up this is the fun bit that looks like chainmail it is chainmail probably call a bolt track

suit you know I protect you from the lightning okay there's holes in it and so I boots on boots off please check it off are you entirely sure about what we're doing here what can possibly go

wrong Scarfo my best scarf look after that James so one foot in there it's just so

the machine outputs about three-quarters of a million volts what but this suit will protect you it's got holes in it has got holes in it can I have your hand no please

the metal suit will act like a cage allowing the Lightning to flow around me rather than through me at least that's the theory just when they buy me again

the whole ship if the game doesn't work then what happens if it were to go through you that would be a bad thing when you say let's not explore the badness of it yeah just bad its way but

I mean it's not instant but I mean it's your odds are against you rather than for you thank you stop talking now please mark don't say

any other words the Tesla : massively increases the mains voltage when the energy levels high enough

current will flow to me and I should be able to direct it with my so everybody

with sensitive hearing or to leave the room now anybody with implants in their ears or pacemakers or heart problems ought to leave now and we're good to go

so good to go Richard fantastic mark takes a moment to build the voltage to Lightning levels okay

[Music] [Music] this machine was conceived by eccentric

19th century inventor Nikola Tesla labeled a mad scientist about we fell in love with a pigeon he was also a pioneer of robotics radio and

electric power in the course of looking for ways to transmit electricity across America he devised this way of controlling lightly

like nature's lightning by lightning wants to find the shortest way to learn [Music] it is the most extraordinary experience

like millions of ants crawling all over me okay crew let's go in I was making lightning come out of my fingers briefly

I can't by some freak chance just continue to happen for me unfortunately no that is a superhero moving up okay so controlling lightning looks good but

how does it help engineers who want to cut steel fast and precisely the answer to that is as fantastic sounding as lightning is to look at because what is

happening is the huge surge of electricity turns the air into a fourth state of matter plasma more familiar with three stage

spreads like ice liquids like water and then gas like steam from a kettle and we're all familiar with the way you move from one state to another if you heat

the solid and get a liquid it's a liquid you get gas but if you heat a gas with say a huge surge of electricity you get plasma the fourth state of matter

plasma is actually common throughout the universe the Sun and the stars of human plasma but it's very rare on earth this

is a slow-motion shot of man-made plasma when it's controlled and super focused

its heat can be used to cut metal stream of pressurized air comes out of it the

air is charged that's what creates the plasma and that's what melts through the steel just as lightning charges air and turns it into a plasma the electric current in

the cutter does the same it charges the air turns it into a jet of plasma and that's what melts the metal very quickly faster but an oxy-acetylene cutter but

there's absolutely no sense of course of resistance there's no effort through it from me I'm just moving along the surface of the

metal plasma cutting is brilliant for big metal construction because it's quicker than oxy-acetylene it also creates a much cleaner cut so it needs

less finishing and that speeds production get further just air and electricity doing that the power of lightning [Music]

plasma cutting on a grand scale was the secret behind making the meal average roading here at the Eiffel metal construction company he has the same rifle that built the Paris terror the

lightning heat of the plasma cutters sliced over 2000 steel segments in just two years so that's how the deck of the

world's longest cable-stayed bridge was built by controlling the power of lightning but once they'd created the road deck they faced another challenge

putting it in place without toppling the colossal towers built to hold it up a lucky accident that reinvented the

frying pan would solve this problem [Music] vermeil our bridge engineers had to

somehow launch their steel road across the top of the giant concrete piers but to achieve this they had to devise a

radical new delivery technique only a regular bridge there's kind of two main ways of getting the deck onto the piers first of all you build your peers which

I'm doing here with bread obviously there we go that's my peers then you can either build sections of your deck actually on site

and crane them into position and there's my bridge complete or option two you can build the whole deck and push it out

over the piers from the sides of the valley until it's in place perfect but Millau is not your regular bridge for one thing because of the depth of the valley they're trying to cross the

piers are not little squat ones like these they're great big tall ones like these which means once they've actually got these into place 240 metres tall the

expense difficulty and complications of using cranes to sections of Road bridge up were just immense so you go for the second option you build the deck you

push it out but with piers this high 240 metres the sideways force of the deck would just topple them and disaster

this is the engineer's solution a special hydraulic jack it uses two giant wedges which slide across each other to

lift and move a steel deck over the dunes using wedges means that the road deck is lifted and slid forward in one

move avoiding any pushing against the piers then as the second wedge is pull that the deck is lowered to sit back down on top of the piers

both wedges then reset to start the cycle again each cycle lifts and moves thousands of tons of steel a modest 60

centimeters but over 15 months the giant Road deck was slid precisely and safely into place it's incredibly simple but

very very clever there's just one thing 36,000 tons of decking are pressing down on top of these wedges they have to be able to slide over one another to work

but to do that the engineers had to rely on the most slippery substance ever created back in 1938 chemist Roy

Plunkett was working to improve the efficiency of fridges but he ended up making an amazingly slippery powder he'd made PTFE polytetrafluoroethylene known

the world over by its famous brand name Tiffany you black no stain Tech law even hours after cooking pans rinse clean in

seconds no soaking no scouring Teflon inside it really is the slipperiest thing made by mankind and that sounds like something that's got to be put to

the test which is where my friend Warren comes in right when I say my friend Warrick it's more Boris yes Boris is a decade he's got stickiest feet I would say in the animal kingdom this is Boris

the Gecko before me for us the Gecko test on a piece of glass well that's Boris quite happily there you go that's vertical maybe even a bit

more and is that's glass gecko tested by Boris food now we must test Teflon so all right let's perform a gecko test I've just realized this might be quite

disconcerting for Boris but I don't Boris don't think what I know you're now thinking we're using frying pan because it's coated with the material not

because okay I'm sorry well I wouldn't blame you if you jump straight out of this right so let's try

them on this well clearly then our nonstick material passes the internationally recognized gecko test

winnings it's gecko proof I think that really is the final word from our gecko tester

Teflon really is very very slippery I think we need to turn things up a bit

[Music] yes this is attraction to a lot heavier

than a gecko and a lot more difficult to push around Gary Lynch is from one of the UK's leading PTFE manufacturers Gary's

helping me to test just how nonstick his brand of Teflon can be okay let's get off now this is a non-slip stuff and then you're gonna try

and move the traction engine oh yeah this is simplest this is just a metal tray with well stickers on it how we're gonna ship this thing are we gonna shift it yeah well I've got a few friends

Richard I brought along with you what some beefcakes turns out the muscle is my local rugby team look properly daft if it doesn't work agent one

question this weighs well now it's weighs just under ten ton ten tons so if this was just standing on its wheels just not on this stuff on the ground it would take twenty six and a half turn to

break the friction and move it so if we use people let's well under kilos peace be pushing 400 people 300 people and one fruit beat okay good luck okay if we're

ready in your own time do you want me to count you in or you're best off okay one

two three and then a ten-ton wait come on lads keep it go we'll do it again three two one Hey

well that's fantastic you could take a breather obviously was only really when Gary and I joined in Euler noticed it it moved so there we have it over nine tons

of traction engine shifted standing on concrete it should have taken three hundred people on Teflon it took just ten a pretty graphic illustration of

just how effective PTFE is obviously not just of moving traction engines sideways with a rugby team you could also use it to move bridges and they did once the

launch had begun there was no going back and PTFE proved itself on the wedges sliding the massive steel road deck over the valley all thanks to the Wonder

nonstick stuff called Teflon discovered by luck in a nap now the engineers had to face their next big problem how to

construct the tallest piers ever built each to a specific point in the sky with millimeter precision the highest of these Giants is 245

meters as tall as a 70 story skyscraper and the other six aren't exactly short they all had to end up in exactly the right place within millimeters

they were only possible with the technology from the submarine war games of the Cold War Engineers analyze the stresses and

strains on the bridge round-the-clock 365 days a year this is the control room where today cameras and sensors monitor the traffic the wind temperature and humidity but

back then when the bridge was under construction it was if anything under even closer scrutiny reflectors dotted about over the structure allowed the

engineers to track the build and monitor the bridges precise position the engineers needed to build each towering pier up to a precise point in space

hundreds of meters above the ground so it could meet the horizontal deck as it slid out thousands of meters from the valley sides a precise surveying network

ensured that they got to exactly the right point in space to within millimeters impossible without a supremely accurate system of measurement the kind you'd need to find a dot in the

ocean q and next connection sex also important it all started when US nuclear submarines began to get lost

the subs were designed to submerge for months with gyroscopic systems to record every move but over time tiny errors mounted up when the subs

surfaced out in the middle of the ocean they couldn't work out where they were a precision nuclear weapon is not much use if you don't know which way to pointed

the US Navy's solution was to launch satellites on surfacing the subs would listen for the satellite signal to work out where they were it was the very

first use of satellites for global navigation the foundation of today's global positioning system or GPS as we all know but Han does it actually work

and how could a signal beam from 20,000 kilometers away help engineers build a bridge to millimeter accuracy the trick is to calculate how long a signal takes

to get to earth if you know its speed and when a signal was sent you can work out a distance very accurately to see just how this works I'm meeting

John Shelton an expert in the field of acoustics in a field I don't well I'm here and well frankly I'm

confused so first of all how can you measure these distances what are we gonna do well you know how GPS works you've got satellites up in the sky that a beaming out signals down to us yeah so depending upon where we are on the

surface of the earth by measuring the delay between those signals from the different satellites we can find out exactly where we are because we know where the satellites are we can measure the delay yes I can get that's right the only problem is we haven't got any pet

satellites so instead of using radio signals we're going to be using acoustic waves noise exactly yeah okay so what we need is a nice noise source I've got my

car I could start it up it makes quite a racket big VA no I think we can do better than that all right it's this I did wonder it's in there it's in here

okay [Music] that's louder than my car

[Music] it's quite handy good enough yeah we call the kiss mo over here and we're going to take this with us and we're going to be making the noise as we go

down and measuring the delay as we go you're coming with a crisp at 20 degrees centigrade sound travels at 340 meters

per second by walking away from the truck then stopping and playing some notes we can measure the delay between the sound leaving the speaker's back at

the truck and reaching us John's computer uses this time difference to calculate a distance okay got it

I immediately noticed the delay between Chris playing and us hearing the sound let's rewind and check it again Chris

strikes the strings then there's a delay before you hear the sound from the speakers the electrical signal travels

to the speaker's the instant Chris plays but it returns through the air at the speed of sound when you get far enough away the delay becomes quite obvious

John's computer measures the time it takes the guitar notes to get from the truck that a to us B from this knowing the speed of sound we can work out how

far we are from the start so half second delay would mean that we're 170 meters from the speakest

our own version of a GPS [Music]

this is quite weird 170 there you go thank you very much so although what we've been doing was a bit well frankly odd if you're watching from over there probably but we were

using a signal to measure distance and it doesn't matter what the signal is we use noise it could be anything if you know how fast the signal is traveling and you know how long it's taken to get

from one point to another then you can use that information to work out how far apart those two points are you don't need a guitarist the satellite signal of nuclear subs

listen form contained data on the time it was sent and where it was sent from and the more satellites you have the more precisely you can fix your position measuring the delay from the time a

signal was sent to the time it's received you can work out how far you are from a satellite just like we calculated our distance from the guitar amplifiers today there

are 24 global positioning satellites orbiting the planet sending signals back to earth now GPS receivers use exactly the same principle only with greater

accuracy they compare the distance from four or more satellites to determine their position your GPS receiver can work out where it is to within 10 meters

but that's fine for directing your car but completely useless in building a fridge where an error of 10 centimeters would be a disaster the meal our

engineers fixed GPS receivers to the deck and piers to keep construction on track their system was way more accurate than car sat-nav but it still wasn't enough

tiny temperature fluctuations and building stresses could send the piers and deck off course and although successfully guided by the satellite data they needed to double-check their

GPS positions against a rock-solid reference point so they anchored one to the ground the engineers took GPS guidance a step

further they bolted a receiver to a fixed point on the side of the valley and it provided a reference signal for all the other receivers on the piers

because it's anchored it reduced the error of the GPS signal down from meters 10 millimeter so the network of monitors

on the bridge constantly check the accuracy of their position data against these known points and all the time the

towers climbed Skyler's so that's how a technology for locating loss subs positioned with pinpoint precision the world's tallest peers but Milla's steel

roadway weighing five times more than the metal used to build the Eiffel Tower needed support from above as well as below and that's where cables come in

when the deck was being pushed out over the top of the piers the engineers used a web of cannons to support the end of it and they held it in place even when

the winds blast it up the map so how did 36,000 tons of steel roads stay put in a valley notorious for storm

force winds the answer lies with a series of accidents in a German silver mine in winter and early spring Europe's weather can turn on its head low

pressure over the Mediterranean sucks cold air from the north down through the south of France the town Valley is pretty much your perfect winter channeling Mountain

storms along its length winds here can reach a hundred and thirty kilometres an hour that's a pretty severe test for the cables here on the mill a bridge they

take the strain but it's only because of a series of mining accidents that they exist at or throughout history miners

have hauled heavier and heavier loads up from the low ground but this put dangerous stresses on the traditional pulleys and ropes used man has made rope since the earliest

times and depending upon where you lift you could choose from a range of different plants to make it in Asia a relative of the banana plant was used to make Manila and then across much of

Europe cannabis in which this is a relative was used to make hemp amongst other things rope is usually made by twisting fibers

together but it does have its limitations to understand ropes limitations I've decided to break some and materials expert climb celia is

going to help me ok Richard what we've got here is a hydraulic press you have the load cell here yes ok so it's going to pull on there yeah and this that's gonna tell us the

force that this is supporting and this is rope as was used initially in the silver mines and everywhere else I'm going to start the Machine by pressing on guessing the big green button taking

up strain I said it just started stretch the rope now

this is a 10-millimeter hemp rope about

the thickness of my little thing and here we go with those increasing just

hit a hundred kilograms 200 and we're now on to 60 kilograms now we're just hitting 300 kilograms oh and

there we go the rope doesn't break suddenly but it gradually different strands at the rope starts to break kids eventually it's supporting some load until eventually

eventually some final strand will break and that's your law lots of 640 kilograms that's nearly two-thirds of a ton so the way it breaks is useful

that's right the weight at which it breaks is not so good the rope breaks gradually single strands break but the rest of the rope um still holds some of the load and so it doesn't sort of just

give up so we need there to test something exactly to earn more the miners needed to haul bigger loads so they were looking for something stronger

than one which is why alternatives like metal chains came about trouble is compared to rope metal chain has a nasty

way of breaking so now I want to test a 10 millimeter metal chain in the same diameter as the rope we snapped I'm gonna film it with a slow-motion camera

while using water from the friendly fire crew to gradually increase the weight in a skip and the loads now starting to go up so we've got 800 remember the same size

rope broke at just six hundred and forty kilos not even two thirds of the time just about to hit 1.7 tons so now we're having me a large car

the chain is rated at two and a half tonnes but we've already hit over three and a half tonnes and it's still holding now we're running out of water we've

probably got about a minute deployed boy telling me is our chain is too strong okay thank you [Music]

all baby does 3790 just like in the minds the chain takes a much greater load the rope but it breaks catastrophic

ly and without any warning so that's exact it's where the two links cross over and that's about cheering it's where as bending around so how quickly were you recording this is a corner of 2004 means per second so that

broke in less than five milliseconds yes warning instant you have the culprit we found the link here in the water and so

you can see here where it's failed so the significance of this is where it's gone is a weak point inherent to the chase it's early it's inherent to the to the design of the chain that the material here is going to see a shear

stress that's going to cause it to fail and this shear strain this is this bending that's every chain has that week every chain is going to have that weakness at that point and that's what costs lives down the mines it's only yes

a failure that catastrophic slack quick what can you do what can you do and that's where a great invention for a

German silver mine comes in in 1829 hair Vilhelm albert director of a cloud style silver mine having witnessed chain links

snap without warning was inspired to reconsider the merits of rope so what was needed to hold huge loads of silver from deep in the mine was

something that combined the structure of rope with the strength of metal hair Vilhelm Albert discovered just that he twisted metal strands together to form a

metal rope the world's first cable sapru Vilhelm Albert gone to something we tested cable no surprise we quickly got

the skip to overflow the cable although the same diameter as the chain is easily carrying over 800 kilos more and well over 4,000 kilos more than the rope it's

the best of both worlds twisting metal strands together like rope means cable is exceptionally strong and when it fails it should give ample

warning just like right and back at Mila the engineers were utterly confident in the strength of their metal ropes at one point during

construction almost 170 metres of deck hung over the valley from just six cables the completed bridge is designed to carry 35,000 tons that's the

equivalent of pickup trucks crammed nose-to-tail in all lanes piled ten to prove the cable strength engineers organized as showy demonstration 28

trucks with a combined weight of over 900 tons drove to the midpoint the cables barely gave the span bent a mere

26 centimeters and triumph then for Wilhelm Albert's metal rope I did but there's a neat twist here at Miele this bridge is designed to last a

hundred and twenty years but inevitably essentially old cable isn't as strong as a new one but if the bridge is held up by cables how do you take them down to

replace them without the bridge falling there well the answer to that lies in the construction of the cables themselves because from above they look like a single solid piece but in fact each one is made up of a bundle of as

many as ninety one smaller cables here they are those smaller cables in fact are venniese made up of seven individual strands and their job is crucial those

middle sized cables because each of those can be taken down and replaced if they corrode without having to take down the entire bundle prompted by accidents

in German silver mines over 180 years ago the inspired idea to make rope from metal strands has made the Magnificent meal our bridge possible but the bridge

would still collapse in the scorching summer heat without an engineering solution borrowed from the ancient Celtic boat builders building with metal comes with one

massive drawback the hotter it gets the more it expands let me show you a little example of metal expansion this is a

heavy duty jar pretty tough to break this is a metal core put in a jar around the core I shall now apply heat and well you probably guess what's going to

happen if I heat up the metal core and expand the metal add heat to metal and it expands this becomes a problem though when the metal

is up against the material its much less flexible in this case glass and what we're waiting for something to happen it's worth thinking where else

might we find large amounts of metal interacting with the material that doesn't like to bend the tiny expansion in this demonstration

scales up the more metal involved Railtrack can dramatically expand in extreme heat and with nowhere to go it in conveniently buckles if this were to

happen on bridge it could be a disaster on your average bridge you leave gaps expansion joints to take up movement of the deck with changes in temperature

but this is not your average bridge the Miller bridge has been welded into one continuous piece of steel from end to end the only place for expansion gaps is

where the road meets the valley at either side in the heat of summer these expansion joints have a critical job to do

every summer the bridge is heated up and it expands the engineers predicted at 40 degrees it grows by about 1.2 meters and that's what this section is for to allow

it to do that the expansion joints above my head that you can hear the traffic thundering over allow the road to remain a continuous surface as the bridge moves backwards and forwards on these mounting

points even the cables taking power to it are designed to be flexible with that movement and that's all well and good here where the bridge meets the land but it doesn't expand just at its ends it

expands all along its length so what you do at the points where it's fixed to those concrete piers obviously the deck has to be fixed to the piers for

stability but in summer heat the two and a half kilometers and horizontal dead expand it's the growth along its length there's the real problem because it

exerts a massive unstoppable force on the vertical concrete piers and concrete is notoriously unbending so the

engineers came up with a very clever solution the base of each pier is solid

but the top 90 metres is split into two thin arms how does this weird design overcome a potentially fatal threat that

brings us to our final connection prehistoric Celtic boats for centuries the ancient Celtic peoples of Ireland and Wales used ingenious boats called

Couric's they were made of a bent wood frame and covered with hide sometimes canvas the key to making concrete flexible enough to withstand summer heat

lies in the wooden skeleton of some of these foes in some Couric's pieces of wood including a keel stringer would run

under the boat from stem to stern they had to be strong but also had to curve even flexible timber can only bend so

far but some early woodworkers found a way around this to find out how I'm visiting the carpentry shop of Peter Faulkner whose passion is building these craft

Peter Richert hello so you ran a workshop here building traditional boats using ancient skills but there is a link to do with the way the pillars of our

bridge a built it is to do with that split in them and I think before we can really understand it a bit more we need to split some wood how'd you do it to cleave it yes yes yeah please that's the way you want to cleave something yes I'd

like to keep something great right table pieces here that's a piece of wood that's piece of ash yes so we just make I'm gonna put in a wedge clean it away

right so you want to have a tap never time yes you'll soon you'll soon break out right no but then I guess this tells

us that actually people have known about cleaving wood for a long time this is new technology no no no prehistoric I mean we don't know ten twenty thousand years cleaving the wood like this means

it splits along its natural grain and keeps it strength but it also changes the flexibility of the wood dramatically let's imagine this now is one of the

pillars supporting our bridge the problem here remember is flexibility because the road deck is so long when it gets hot it expands and it moves out this way or it shrinks back this way when it gets cold and that needs

flexibility it'll just snap the pillar with these splits in how much this is this will Bend as much as you like but because we've left the same amount of wood in it the same amount of stuff it's still just as strong holding things up

there's as much to work under compression I feel a test coming on with two pieces of timber exactly the same size right what I have here is my unique and

custom-built flex test rig this is one of the pillars okay represented by this big chunk of wood and actually proportionally it's almost the same as the pillars with two height I'm going to test an uncleared post

first I've added these straws to measure how far it will Bend before it snaps well I'm so this if it flexes it'll start to knock these little straws out

so using this winch I will pull on that wire to apply the same force as if the

road deck we're expanding out this way

on top of my giant oh the tension grows

as the deck expands oh no it's all gone wrong well we've hit three of the little straws but oh yeah that's not good at

all is it now with the new post Peter uses wedges to drive a split

[Music] will this cleaved timber really bend further than the last poster right now

to simulate another hot day in our bridge the Sun comes up and warms two kilometres of steel road deck it expands and pushes that column that's split in

the wood is allowing it to flex it can still support the same weight from above but it's coping right that's for get it

back so this split timber has gone twice as far without breaking is the first unsplit one but will it return to its

original state as I release the tension the wooden test pair shows it handles the stress without any permanent damage all that flexibility given to it just by

this splitting it down to there at the top lets it Bend it can still support but now it can bend modern woodworkers believe Celtic boat builders used this same principle for

their currents the wooden keel stringer could be split to allow it to bend whilst keeping it strong and sturdy on the mill our bridge concrete which is

usually more like brittle glass can become more flexible with a split in the right place I decided to go to the top of one of the concrete piers to find out just how they

cope with the deck movement in summer I wish to have the ladder is strong for climbing the ladder down onto the tiny inspection

platform precariously positioned on the tallest bridge pier on earth was more than scary a lot more okay I'm assuming

there's somewhere down there to attach the harness - oh that's of you know that's a view

[Laughter] if a file is an excuse second time and I

braced myself to face the winds and my fear 245 meters above the town valley okay

where does this car oh I feel better now Bridge engineer Silvestre galleys explained as I hung on for dear life just how the concrete why

shape allows for movement of the pillars the why form under concrete structure makes the movement easier so the pile if

you like is fixed to the deck is the deck that's in charge and the pillar has to move with the deck as it expands and contract great engineering making concrete bending but discussing the

concept nearly a quarter of a kilometer in the air wasn't my idea of fun thank you very much for explaining it to me I'm not sure I'm so grateful to you for bringing me here to do it we could have

done it on the ground in a roasting heat of high summer when the massive metal road deck expands these split piers can flex 10 times more than conventional

concrete towers then as night falls the bridge cools the deck shrinks and the giant piers return

to shape concrete cleaving is just one inspired solution to the many exceptional challenges that the mill a bridge engineers overcame and rightly

celebrated they wanted to build a bridge that was more than just a link between the two sides of the valley they wanted to create a structure that rather than

detract from would add to the landscape a sculpture in a region treasured by France for its natural beauty and for

what it's worth if you ask me they did it who would guess that to make it they embrace the power of lightning were guided by submarine navigation

use the chance discovery from a chemistry cables prompted by accidents in a German silver mine

and were inspired by a crafty idea from ancient boat builders the meal average a stunning piece of engineering made with incredible style

[Music] [Music]