Secrets of Notre Dame - Ancient Engineering (2021) - Documentary
We are surrounded by extraordinary feats of engineering constantly pushing the boundaries of what's possible Without engineering, there'd be no modern world. Gigantic cities, amazing infrastructure and ingenious inventions Engineering is the key to turn dreams into reality. To reach these dizzying heights, today's technology relies on breakthroughs made by ancient engineers. It's mind boggling how they did this. How did early civilizations build on such a scale? They raised the bar for construction in a way that no one thought possible.
The sheer engineering ability it is in itself impressive By defying the known laws of physics and daring to dream big. They constructed wonders of the world from gigantic pyramids to awe inspiring temples and mighty fortresses. All with the simplest of tools. Can you imagine the skills people would have needed to build like this? Now it's possible to unearth the secrets of the first engineers.
They managed to construct edifices that has survived the ravages of time And reveal how their genius laid the foundations for everything we build today. In the modern world, structures dedicated to God still dominate city skylines. Built with no expense spared, by all the world's major religions across the globe. They are a feat of engineering. They are images of heaven. Amazing mosques, temples, synagogues and churches, Houses of the Holy.
The impact they were designed to have is utter awe and wonder But these white hot modern wonders rely upon earlier breakthroughs. The engineers who constructed them using knowledge and skills built up over thousands of years. Lessons hard won, ancient engineers battled deadly collapses, earthquakes, fire and warfare to create amazing devotional buildings in honor of their gods. Building for God reached a high point in the middle ages when a new engineering movement emerged changing the rules forever. It aimed to use engineering and architecture to create a glimpse of heaven on earth. And it led to the creation of some of the most beautiful and spectacular buildings ever seen.
Gothic cathedrals Gothic cathedrals are not only the most spectacular buildings of their age, I think there are among the most spectacular buildings of all time. They are symbols of our civilization. They are symbols of human achievement.
We've never really seen anything like it again. Taking centuries to build, reaching soaring Heights they feature intricate walls, ceilings of solid stone carved like spider silk and vast stained glass windows seeming to float in midair. When they go in, people's jaws hit the floor and your eyes go up to the roof.
I actually think your heels might come off the ground a bit as you're transported up to the heavens. You are taken out of the everyday world and you encounter something of the divine. The construction of Europe's Gothic cathedrals was one of the pinnacles of human achievement We needed an engineering revolution in design to be able to create that very characteristic Gothic style. These buildings have endured as a lasting symbols of their age To this day, Gothic cathedrals are one of the most outstanding engineering achievements of all time. One of the most iconic is Notre Dame.
Built in the heart of medieval Paris, many believe it's one of the crowning achievements of the Gothic movement. Mainly constructed between 1163 and 1250, it set out to surpass all cathedrals that had gone before, to push the technology of the day to its limits, taking great risks and completely reinventing how a church could look. There was this challenge of massive construction that would be naturally heavy but then introducing elements that made them like they lighter than air.
How could it be done? How do you build high? How do you stop the walls falling down? How do you stop the roof falling down? The solutions arrived at in Notre Dame were world changing and they've stood the test of time. Innovations built into the fabric of the cathedral were copied again and again in structures across Europe and beyond. So what are the engineering secrets that made these spectacular new marvels a reality? To create Gothic, medieval architects would need to rewrite the rule book and challenge engineering principles laid down in the earliest churches. These simple structures had their roots in a building from the pre-Christian world. The Roman Basilica.
The Basilican form is not a religious building in origins at all. It's legal building or a law court. A Basilica was always a predictable rectangular shaped building. It would have a nave and two or more aisles at each side, a high roof vaulted with a half dome and a raised tribunal that Roman tribunes would have stood upon.
Many of the features that would be found in the cathedrals and churches that would follow. Essentially the Gothic cathedral did originate from the Roman Basilica. From there we are transept and then we are at towers. So it all evolves throughout the next two, three, 400 years. Basilicas like the cathedrals that came after them were usually built in the very heart of a town or city, prestige buildings. What happens is that these basilicas are taken over by the church.
The Basilica form is then reproduced again and again and again in early churches. In the fourth century, dramatic events in Rome would speed up the transition from Basilica to church. Inspired by a series of religious dreams and visions, the Emperor Constantine made Christianity legal. 10 years later, it became the official religion of the Roman empire. By the sixth century, the Western Roman empire had fallen. What survived lay in the East.
It came to be known as the Byzantine Empire and it straddled Europe and Asia. Its capital was Constantinople. The Byzantine empire was the most important economic, cultural and military power in Europe leading the world in mathematics and engineering. In 532, the new emperor Justinian wanted to signal his prestige with a spectacular Christian Church.
It would be known as the Hagia Sophia or Holy wisdom. Justinian imagined a vast interior, topped by a huge and dazzling dome. And that presented a major engineering challenge. They wouldn't have had any idea whether that building would have worked because there's nothing else like it. They're stepping off into the unknown Could such an audacious design be made a reality? For those charged with building it, the pressures would have been immense. I can imagine the construction site at the Hagia Sophia was incredibly stressful because you were embarking on the unknown.
With a planned height of 183 feet, and a footprint of nearly 65,000 square feet, the Hagia Sophia would be a huge building. Two things happen when you increase the height of the building. One of them is that you expose the building to a lot more wind force. The other thing is the building itself weighs more and that increases the loads on the foundations that are underneath. Workers would need to dig deep foundations into thick bed rock with limited tools. Today mechanical excavators dig foundations which are then reinforced with concrete.
In 2014 the Wilshire Grand Center in Los Angeles took foundation construction to a whole new level. It required a single gargantuan slab of concrete sufficiently robust to stabilize the building in an earthquake calling for a lot of concrete to be poured in one go. Engineers choreographed 2000 truckloads of concrete pouring continuously for 20 hours breaking the world record at the time for the largest uninterrupted pour. When completed, the foundations were 18 feet deep and weighed a mighty 84 million pounds.
They support the tallest building in Los Angeles. An office and hotel complex reaching 1099 feet In sixth century Constantinople, the Emperor Justinian had started his own record breaking building, the Hagia Sophia. To ensure success, he turned to two of the greatest geometers or engineers of his day Isidore of Miletus and Anthemius of Tralles.
Before they could construct the massive dome, they had to solve the geometric problem of placing a circle on top of a square. What domes tried to do is flatten. So they push outwards.
So what you do in that case is you have to tie the base of the dome together so the forces are resisted and only vertical loads go down the walls 'cause it's the horizontal loads that would push the walls over. The architect's designed for massive piers to stand at each corner of the square. On top of the piers, they built four arches and fill the spaces between with masonry to create curved triangular shapes called pendentives. These combined with the tops of the arches to create a strong base for the dome.
The engineers recruited 10,000 workers to get the job done. And in 537 AD, after little more than five years construction time, it was complete. The structures dome towered over the city. From inside the dome appears to float above a ring of windows. These led in a flood of celestial light to illuminate the nave below. At the time, this was the world's largest interior space and the most complex building yet constructed.
Isidore and Anthemius had solved the problem of dome architecture in a stroke of engineering genius. But it wasn't long before the Hagia Sophia faced disaster. Despite Justinian having the best technologies available to him at the time, he is still at the mercy ultimately of the gods in the natural world In 558AD, a major earthquake struck Constantinople The dome failed collapsing in ruins. It was soon rebuilt in a taller and stronger form. Over the centuries, earthquakes have continued to inflict damage on the Hagia Sophia but this magnificent structure still stands today, a landmark in the history of engineering It shows the fundamental strength of the principles that they are applying that despite earthquake, despite war it's still there.
Even modern day engineers struggle when faced with the destructive power of earthquakes. In Kobe Japan in 1995, a quake measuring 7.2 on the Richter scale wreaked havoc toppling countless buildings and an elevated freeway. In total that caused $100 billion worth of damage. What we've learned from recent earthquakes like in Kobe is that every single earthquake is different. It has its own fingerprints, if you like.
Every time an earthquake happens, engineers learned something new and they apply it on the next building. Most buildings are designed to support a vertical load flowing down through the walls but not a horizontal load pushing sideways. And in earthquakes it's often the horizontal forces that do the damage. When an earthquake hits a structure, the structure is going to be shaken in a sideways motion and these forces can also push the building up and down as well as sideways.
And that was kind of what makes it so chaotic and intense. That change in direction which cause forces and stresses in the building and cause things to break One high-tech solution is to protect a building through base isolation. Constructing it on giant flexible pads made of steel and a rubber or pits of ball bearings and Springs. When a quake strikes, the isolators vibrate but the building itself should remain steady. Incredibly, a similar solution was developed by Chinese engineers 2,500 years ago. They designed a bracket system called dougong that can even survive modern day shake tests.
The dougong is a masterpiece of joinery, a series of interlocking beams, each cut to precise measurements. When compressed under the heavy roof, the system is very strong yet remarkably flexible. None of the individual pieces are fixed or glued and the supporting columns are also free standing.
so the building moves with a quake And it's worked Many ancient Chinese buildings have survived numerous earthquakes. This principle underpins another modern earthquake-proofing technology. Another way is to put a damper inside the building. When the earthquake pushes in one direction, the dumper moves in the other direction. So it counteracts the forces.
Taipei 101 has a damper system featuring a mighty 728 ton pendulum. It's made of 41 layers of steel plates suspended by eight steel cables. Below are 16 hydraulic viscous dampers eight slanted and eight level. The pendulum moves to counteract strong winds and even earthquakes reducing building vibration by 40%. It's incredibly impressive.
When you think about it's a very simple use of physics to protect a building but incredibly effective. There's no doubt these engineering developments have helped tall structures survive earthquakes In medieval France, a different kind of seismic change was about to occur. This time it wasn't earthquakes that posed a threat to traditional churches but the ambition of a new breed of engineer. Leading the way, Abbot Suger.
Close to the King of France and to the Pope, Suger was an influential figure of his age. His prestigious Abbey Saint-Denis, stood on the outskirts of Paris, but was in dire need of renovation. Suger make-over plans called for nothing less than an engineering revolution. Until now the options had been limited for European churches. Most were built in a bulky and squat style known as Romanesque, heavy roofs supported by thick walls with small windows casting very little light into cramped interiors. Suger believed a new form of engineering could make a new kind of church possible.
His ultimate goal to get more heavenly light into his Abbey. Christ and God was seen as lux, light, the light of the world. And so the more lights you could get into your building, the closer you could get man to God.
Light would help create an experience of heaven on earth inspiring religious fervor in church goers. But how could Suger develop the engineering tools to achieve this? It wouldn't be easy. The simple problem of getting light into a massive building, is that you need to make holes in walls and yet those walls support the roof. So to put windows into walls you need to make sure that those walls themselves on not weight-bearing. Suger needed a new approach to construction. In the process he'd kickstart what would become known as Gothic architecture.
Work began on Saint-Denis around the year 1135. The first engineering innovation was the use of the pointed arch. At this time, most churches had conventional rounded arches weight from above was distributed out to the sides. Thick walls were required to resist these forces but to achieve his new vision, Suger needed tall thin walls with large windows. The pointed arch distributes weight downwards not sideways.
So heavy walls would no longer be necessary. A second innovation helped reduce the load even further. Ribbed vaulted ceilings work like a skeleton of stone thick supporting ribs with a thinner stone skin filling the space between. What the narrowness of those ribs actually does is allow you to transfer more weight from above and it takes it directly downwards rather than pushing the walls out. Revolting was extremely revolutionary. The excess tension was taken down into your small slender piers so everything could be lifted upwards, could be lifted outwards. and the tension
was taken down once without just collapsing in. It's effect was to make the vault or ceiling much lighter. You have these thin ribs going up into the ceiling and peeling off in wonderful curve. So they almost looked like the bowels of a tree, very very delicate and yet so good at supporting immense weight But even with a reduced load, some sideways pressure pushed against the walls.
So Sujer and his architect made use of the feature that now truly defines Gothic architecture. The flying buttress Flying buttresses are sort of the epitomy of Gothic which create a sort of skeletal structural cage around the exterior that holds up this light airy structure within it. Piers or buttresses, outside the building are connected using sloped fliers. These take horizontal forces and redirect them to the ground. They took the weight, which was pressed outward on the walls and they absorbed it down to strong buttresses on the outside Flying buttresses are thin and separated from the building so they don't block out light.
And with thinner walls, it was possible to engineer huge stained glass windows on a monumental scale. Just as Abbot Suger had intended, they allowed daylight to flood in. The link between light and the divine is actually a very ancient idea, but the Gothic architects were the first ones who managed to bring it into the construction of immense buildings in a coherent way Completed in 1144, the rebuilt Abbey of Saint-Denis was an engineering triumph.
Here for the first time in one place, were the three defining elements of Gothic pointed arches, rib vaulted ceilings and flying buttresses. What Suger did at Saint-Denis was so spectacular but it becomes a blueprint for cathedrals across Northern Europe. The result of the innovations at Saint-Denis was spectacular.
A gravity defying lightness, soaring ceilings, a delicate house of cards, suffused with light. The success of this new Gothic engineering lay in moving stone from inside to outside leaving the interior open and uncluttered, a lesson modern engineers haven't forgotten. 800 years after Saint-Denis, a new building in Paris would once again turn the world upside down.
The Pompidou Centre opened in 1977 It's the first example of a modern inside out building. All of its plumbing, electrics and air con systems have been moved to the outside of the structure where they're celebrated in bright colors. Just as at Saint-Denis, The motivation was to create more space inside.
Engineering driving new forms of construction. In 1986, the Lloyd's Building in the city of London pulled the same trick shifting services to the exterior, but this time upward creating cavernous interiors filled with light. This is sort of like putting your skeleton on the outside of your body so that you can see how your body works. You create some interesting architecture, engineers love it, but not everybody does Never again, would an architect need to hide the working guts of a building. I really love inside out buildings.
And what I really like about places like the Pompidou Center is that you can really see how the structure works. Groundbreaking engineering sets trends that inspires imitation. And in 12th century Europe, this was certainly true of Saint-Denis. Suger's New Abbey had caused a stir. It's adventurous style would inspire one of the greatest cathedrals of all time and a pinnacle of French Gothic architecture, Notre-Dame. The Bishop of Paris, Maurice de Sully was determined to outdo his rival Abbot Suger.
Like Saint-Denis, Notre Dame Cathedral was no longer fit for purpose and De Sully wanted the latest engineering for his own renovation. It really was a cathedral race. There's almost certainly a one-upmanship that's going on all over North and Europe.
Threw down the gauntlet to his cathedral builders. The challenge, construct a church in the style established at Saint-Denis, but on steroids What they were doing at Notre Dame is essentially supersizing what had just been achieved at Saint-Denis And it was very audacious to actually say, we can do more. The architects of Notre Dame, they wanna pick it up and they wanna push it even further. And they want to build a church bigger than anything that had been built before. Work began on the reconstruction of Notre Dame in 1163 when its cornerstone was laid it was a colossal undertaking several hundred workers, a building site full of noise and dust, the smoke and fire forges, the rasp of carpenter saws, stone dust thick in the air as masons cut and carved and polished. It's bringing in so many people to do the work that it helps to transform the economy of Paris.
The architects of the time were master masons, men of vision and skill who use geometry to create sophisticated patterns in stone. Once foundations were in place, engineers could make a start on the walls of the church. De Sully wanted taller walls so much bigger flying buttresses would be needed than at Santa-Denis.
As the walls soared higher, scaffolding became necessary. It was hung as a section from the walls and lifted higher as the wall height increased Building cathedrals was an incredibly dangerous process. You're thinking about carrying blocks up immense heights in an age before they have proper modern scaffolding They need to be brave. And there are tragedies there are accidents people die But how did medieval builders haul huge rocks high up in the air? Today city skylines are dominated by cranes mechanized equivalents of a tool invented around 1700 years ago, the windlass. This early form of winch was designed to lift heavy weights. Medieval engineers adapted it to create a crane attaching the winch to a large wheel.
Like some giant hamster wheel, the human inside provided muscle power to efficiently lift heavy loads of stone. Placed high in the building, it was used to lift all the elements needed for the roof and vault. The vaulting was very important because it was something beautiful to look up to. That was the whole point of the Gothic cathedrals so your eyes were raised up to the ceiling so it needed to be beautiful. Construction of the roof and the vault was one of the most dangerous stages of cathedral building.
And even today roof construction can be an engineering nightmare. In 2003, a new terminal open at Charles de Gaulle Airport 15 miles Northeast of Paris, Terminal two featured a futuristic concrete tube cut through with windows designed to awe inspiring but sometimes the vision of architects conflicts with on the ground realities faced by engineers. Quite often you get this battle of form versus function. And as engineers, we're obviously trained to come at this from a very pragmatic approach and the artistic nature of it comes second to that. 11 months after opening a section of roof collapsed The disaster killed four people and injured more.
An investigation revealed the main roof beam and concrete reinforcing weren't strong enough and this contributed to the collapse. The tragic collapse of the Charles de Gaulle Airport building just shows how critical it is for engineers to be able to deliver the architect's vision safely and securely At Notre Dame, the engineers and builders toiled for decades to realize the dreams of the Bishop of Paris. By the year 1260, Notre Dame was largely complete. It had taken around a century to create this remarkable structure.
The rebuilt cathedral soon became a symbol of Paris and even of France itself. Notre Dame is one of the first supersize Gothic cathedrals that then came to dominate Europe. It was proof that the idea is explored in Saint-Denis actually worked and could be applied across the board That is where the real engineering feat is in these Gothic cathedrals. It's just pushing the style and the technology as far as it can go. It's pioneering rib vaults, colorful and gigantic rose windows and staggering height made this cathedral a new wonder of the world.
If I today, I'm in awe of it goodness knows how people must've felt all the way back in the 12th and 13th centuries. I think that going into Notre Dame would have been mind blowing for people in the 13th or 14th centuries to see a building the likes of which had never been achieved before you'd go in and the walls were pierced with windows. The whole building was flooded with light. The vaulting was inconceivably high. It would have been a profound memorable physical experience.
The outside of the cathedral was equally impressive not least thanks to its spectacular flying buttresses. These had never been attempted on such a scale before and came to define cathedrals from the peak of the Gothic era. Some modern architects still incorporate flying buttresses into their buildings but this is often more about style than necessity. With the advent of steel and reinforced concrete in the 19th century, what we're able to do is resist tension forces. They didn't have that option in the Gothic cathedrals. Today's engineers have access to materials that can stretch or resist tension in ways their medieval ancestors could only dream of.
Thanks to the strength and malleability of concrete and steel, buildings can now soar to the heavens without any extra support structures. Materials like steel which can have high tensile strength means that we have much more freedom in terms of how we design a building And human nature means striving to build ever higher. In the middle ages, Notre Dame launched a race for height At 226 feet tall, it was undoubtedly impressive, but inspired by the achievement across Europe, New cathedrals would go on to smash the record time and time again. They were building greater higher, wider, taller buildings all trying to outdo and get theirs finished first.
In 1311, Lincoln cathedral became the tallest building in the world at 525 feet. It was the first to surpass the height of the Great Pyramid of Giza and held the record for 238 years until its Spire collapsed. In the year 1225, Beauvais Cathedral was sent to take up the mantle but something went terribly wrong during construction.
It collapses. What happens at Beauvais is a collapse. Engineering experts think that cathedrals, columns or piers were simply too slender for its great height. Over time, the weight of a building can cause mortar to shift and crack which can in turn, move arches and columns and eventually bring the whole thing crashing down In 1573, Beauvais collapsed a second time. Stones began to fall during a service.
The congregation rushed out Miraculously, nobody was killed. Today, modern braces may be the only thing keeping Beauvais cathedral from falling down. I think what happens at Beauvais is an example of really just pushing high Gothic to its limits. You can put your trust in God and the skills of your masons but when you just try to push too far and too hard things start collapsing The passion to build ever bigger ever more beautiful had pushed Gothic engineers to the limits and beyond Its estimated that almost one in five of all cathedrals built in the middle ages suffered catastrophic damage or collapse.
We live in a day and age where we have the mathematical capabilities and the computational capabilities to work out stress, how far we can push materials structurally. They didn't have that technology available to them. Compression, the downward force of a building's own weight was often the culprit in the collapse of cathedrals. The stone structure too heavy for slender columns.
Modern demolition experts have learned that when buildings have to come down, they often simply need to take out the pillars and compression will do the rest. Despite the many collapses, dozens of Gothic cathedrals across Europe still stand today, iconic buildings . And iconic buildings often bear witness to the great moments of history. Notre Dame has seen coronations, canonizations, funeral masses and notable marriages. It's hosted important visitors.
Some more welcome than others. Sometimes being an icon can draw unwelcome attention. In the French revolution in 1789, Notre Dame was attacked as a symbol of the old regime. Statues were destroyed. Windows smashed and the mighty bronze bells melted down to make canon but the cathedral stood firm throughout the turbulence centuries until 2019.
Notre Dame was undergoing major renovations when around 6:00 PM on April 15th, it's fire alarm sounded. Guards investigated but could find no flames. It turned out they'd searched the wrong area. By the time they realized their mistake, it was too late. The fire raged for 15 hours.
Lead from the roof melted and ran down the building like water. Flames soared hundreds of feet into the sky. At around 8:00 PM, the Spire collapsed. 400 firefighters tackled the blaze but structural engineering experts advised against fighting the flames from the air. The weight to falling water would cause collapse. Instead they risked their lives to tackle the fire from within the structure.
Raving ferocious temperatures and the risk of falling masonry. The fire burned all night. By 7:00 AM, the danger was over. Firefighters put out the last embers. The roof and vault were gone and the interior left blackened and ruined.
The world really did weep on April 15, 2019 when Notre Dame did go up in flames It had been such an icon of Paris and France, but also of everything that had occurred from the Gothic era. But it's Testament to Notre Dame's original brilliant engineers that the walls towers largely survived. Even the 13th century rose windows stood firm.
Notre Dame will rise again And Gothic engineering isn't over. There have been revivals and in Spain one spectacular modern flourish. The Sagrada Familia in Barcelona is taking Gothic in a totally new direction. It's architect Antoni Gaudi took on the project in 1883 and decided to attempt something far more intriguing than just another Gothic structure.
Gaudi was already renowned for stunning homes built in an Art Nouveau style, Casa Calvet and the Güell Palace But his defining project aimed to surpass even the greatest feats of Gothic engineering. Could it be done? Just as eight centuries before, new engineering would have to provide solutions. The Sagrada Familia, it's evolving as it's being built. And so it shows the ongoing story of cathedral building To complicate things further, Gaudi wanted to build a structure with no right angles or even any straight lines.
This truly was something totally new. It is the vision of a visionary architect who is seeking to express not just architectural practices but also expressing his own very personal devotion to particular theological ideas. Gaudi liked to use scale models in his work. And for the Sagrada Familia built a series of upside down hanging models.
Gaudi was trying to make a structure like Gothic Cathedral essentially a compression only structure. The models allowed him to analyze how forces would move through his building enabling him to create a compression only structure where the force has traveled downwards not sideways. And so dispensing with the need for buttressing. Unfortunately, many of Gaudi's models were destroyed by anarchists in the Spanish civil war. So engineers have had to use modern computerized techniques to achieve Gaudi's vision.
The resulting engineering solutions are inspired. The main piers of the church lean outwards to help balance the structure. And thanks to the innovative forms Gaudi developed, holes are punched in the volts allowing light into the church from above something Gothic cathedral builders of the past could never have achieved. Ingenious double twist columns enabled this structure to soar higher than any other religious building in year-round. over 550 feet.
Gaudi died in 1926 before his cathedral was completed. Work continues to this day. The cathedral is proof that engineers can take the Gothic project further.
It's perfectly possible to build Gothic cathedrals that are bigger than the ones that were done at the time. Be very expensive but yeah we know we could certainly go bigger. So far it's taken over 130 years to build the Sagrada Familia and nobody knows exactly when the final stone will be set in place. Perhaps further Gothic cathedrals will one day follow this one potentially reaching even higher than Gaudi's masterpiece. The human race has created sacred spaces since the dawn of history, constructing devotional buildings of beauty and serenity to honor the gods. And the great Gothic cathedrals are houses of light soaring heavenward, pinnacles of achievement, still awe inspiring today, monuments to the skills and imagination of ancient engineers.