by Roma Agrawal
The Shard is now a landmark in London, England.
Moving past the plyboard portal, I entered a maze of plastic barriers and wove my way through, slightly worried that I’d get lost, as the fenced pathways were arranged differently from the last time I’d visited. Eventually I stepped tentatively into a cage-like elevator – a hoist – that was inclined slightly to match the angle of the tower. It shuddered and groaned then shot up rapidly, while my eyes stayed glued to the building, not daring to look down. (Knowing that The Shard’s elevator was the first inclined hoist ever to be stuck to the outside of a tower was cool, but it did nothing to lessen my discomfort.) When the elevator finally ground to a halt, I emerged halfway up the building. It was quiet and deserted, and its skeleton was bare: rust-coloured steel columns towered above a firm, blotchy-grey concrete floor. Resisting the urge to stroke it, I tried to picture what this place might look like when it was full of people, furniture and activity. On that day, it was quiet.
I willed myself back into the hoist, this time rising to the highest level it accessed – the 69th floor. Here it felt completely different. The structure was open to the elements. Metal barriers protected the edge of the building, as the glass was not yet installed. The solitude of the lower levels was replaced by a flurry of activity – workers shouting instructions, pieces of steel clanging, cranes beeping as they lifted beams, and concrete spewing out of quaking pumps. Above me rose the crown of the tower – its elegant spire – which I had worked on. Another eighteen flights of stairs led to the highest floor. It suddenly hit me that this was the first time I’d been able to go there, as it hadn’t been finished on my previous site visits. Today was truly special.
At the top step, though, I had to stop. The tapering shape of the tower meant that this level – the 87th floor – was relatively small. Even standing at the staircase, which ran through the centre of the floor, I seemed close to the edge. My stomach churned. I suppressed a rising feeling of fear. Fresh, chilly air entered my lungs as I took calming breaths with my eyes closed. When I felt less dizzy, I opened my eye (that’s right, just the one).
I was at the intersection of the sky and humanity. After months of making models, doing calculations and creating drawings, I was finally seeing the project made real. It felt so much larger and more tangible than the sketches on a piece of paper or drawings on a computer screen. This phase of construction is a thrill: a moment when the niceties of false ceilings and floors are missing, there isn’t the restriction of a facade, and the general public has never crossed the threshold. To me it felt like having a backstage pass for the rehearsal of a big rock concert – a privileged glimpse of all the stuff that will soon be hidden away and embellished, but which forms the backbone of what we will finally see. Visiting the site filled me with awe for the object we had created. It motivated and refreshed me, and reminded me why I love the creative process of design and construction, particularly for skyscrapers.
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If you were to draw a graph of humanity’s tallest buildings over time, which is exactly the sort of thing I might happily spend an evening doing, you would see that it suddenly shoots skywards around the 1880s. For millennia, the Great Pyramid of Giza (at 146m) held the record as the tallest human-made structure in the world. It wasn’t until medieval times that this record was surpassed, by Lincoln Cathedral (160m), which held the title from 1311 until 1549, when a storm snapped its spire. This made St Mary’s Church in Stralsund in Germany (151m) the tallest building – until it, too, lost its spire, to a lightning strike in 1647. It was replaced by Strasbourg Cathedral (which was a mere 142m, but by now the Great Pyramid had eroded so much it didn’t reach 140m). The real quest for height began in the nineteenth century, when the first skyscraper was erected in Chicago in 1884. Admittedly, at 10 storeys – a mere 42m – it’s hardly what we think of as a skyscraper today, but it was the first tall building to be supported by a metal frame. In 1889 the Eiffel Tower became the first building to hit the 300m mark. Since then our ambitions, and our buildings, have soared. It took nearly 4,000 years to beat the height of the pyramids – shaky spires notwithstanding. But in the past 150 years, our structures have grown from about 150m tall to over 1000m.
Plotting the heights of the tallest buildings over time demonstrates how technical innovations over the past century have accelerated how high we can build.
Isaac Newton famously said that ‘If I have seen further, it is by standing on the shoulders of giants.’ Standing at the top of the tallest tower in western Europe (310m), and aware of all the material and techniques that had gone into its making – the clanging steel and beeping cranes to name a couple – I was vividly reminded of how we got here, of the key people in our history who helped unlock the sky. Newton, of course, was one of them: without his Third Law of Motion, for example, I wouldn’t be able to calculate the forces at work in an arch. But there are others who pushed us to think outside the box (of simple, single-storey dwellings) and who created the cranes and elevators without which we would still be stuck at ground level or thereabouts. The Shard is built not just on innovative foundations but on a legacy of historical ideas and advances that revolutionised construction and made our skyscrapers possible. For a start, to get a tall building off the ground we have to get things off the ground. Before cranes, the difficulty of this task seriously limited our construction ambitions – until, that is, Archimedes (287–212 BC) invented the compound pulley.
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The pulley itself pre-dates Archimedes. In approximately 1500 BC people of the Mesopotamian civilisation (in what is now Iraq) used single-pulley systems to hoist water. A pulley is a suspended wheel with a rope wrapped around it. One end of the rope is tied to the heavy object that needs to be lifted – like a bucket – while a person pulls on the other end. It was a very practical tool, because you could lift objects while standing on the ground and pulling downwards, using gravity to help you. Until the pulley was invented, you had to find a level that was higher than your object’s destination and pull upwards. The pulley changed the direction of the force, which meant we could move larger loads.
Simple (above left) and compound pulleys (above right).
Archimedes, however, had a restless imagination that he applied to mathematics, physics and even weapon-making, as well as engineering. He improved the pulley by wrapping the rope around not one wheel but several. With one pulley, the force you have to exert to lift a load of a certain weight is equal to that weight. So a 10kg mass needs a force of 10kg x 9.8m/s2 (the gravitational pull), which equals 9.8N. (The N stands for newtons: named after the scientist, and another reminder of how key a figure he is for engineering – without his Law of Universal Gravitation I wouldn’t be able to make this calculation.) The amount of energy you expend is the force you’ve applied multiplied by the distance. With a single pulley, if you want to lift this weight by 1m, you have to pull the rope 1m as well, so the energy you’ve used is 9.8N x 1m = 9.8Nm (i.e. newton metre).
If you use two pulleys, however, while the energy you expend must remain the same (since you’re moving a fixed weight by a fixed amount), you halve the force needed. The reason for this is that the weight is now supported by not one but two sections of rope. Each section of rope needs to move by 1m to lift the weight by 1m, which means you have to pull the rope by 2m. Since the energy is the same, but the distance is doubled, the force you apply is halved. The same principle applies for three pulleys, or ten.
Archimedes made a radical claim to his ruler, King Hiero II, that any weight could be moved using his compound pulley system. Unsurprisingly, Hiero was sceptical and demanded that Archimedes prove it. One of the largest cargo ships from the king’s arsenal was heavily loaded with people and freight. Hauling it to the sea with ropes normally took the full strength of dozens of men, but Hiero challenged Archimedes to do it alone. Watched by the king and an assembled crowd, Archimedes set up an arrangement of pulleys, wrapped a rope around them, attached one end of the rope to the shi
p, and pulled on the other. According to Plutarch’s Lives (biographies believed to have been written in the early second century) ‘he drew the ship in a straight line, as smoothly and evenly as if she had been in the sea.’
A Roman crane using a five-pulley system.
The Romans recognised the multiple pulley’s potential and developed it further by incorporating it into their cranes. Two staves of wood arranged in an inverted V formed the crane’s skeleton. The top ends of the staves were fixed together with an iron bracket and the base was anchored to the ground. Between these two staves a rod would be set horizontally (creating an A shape) to act as a windlass: i.e., a rope could be attached to it and then raised or lowered by rotating it, just like the apparatus used to operate a bucket in a well. Fixed to the top of the crane was a two-wheel pulley block; a rope was threaded from the windlass through this and into a third pulley positioned just above the load. At either end of the windlass were four handle-like spikes that could be used to turn it, thereby raising or lowering relatively big loads with ease. If the Romans had to lift something larger they added more pulleys and more rotating sections, and replaced the four turning spikes with a large wheel called a treadwheel.
Using a crane with pulleys, a Roman labourer could lift loads 60 times heavier than an ancient Egyptian could handle. And although they are much bigger, the cranes we use today still work on the same principle. Long, square hollow pieces of steel are assembled into a frame to form a very tall tower, and a long arm or jib is attached. The jib holds the all-important multiple pulley system, and the human muscles and spike-handles of the Roman version are replaced by petrol power. The jib moves right and left, through 360°, carrying multiple tonnes of steel or glass, attached safely to the modern version of Archimedes’ invention.
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By understanding the potential of cranes and arches, the Romans were able to build bigger. But their abilities were matched by their ambition: they were prepared to think bigger as well. As their empire grew, and the population along with it, the Romans found their towns expanding into large cities. To fit everybody in they built insulae: the ancient equivalent of apartment buildings, up to an unprecedented 10 storeys tall. (The pyramids were of course much taller, but you certainly couldn’t live in them.)
Spreading across an entire block of the city, the insulae were surrounded on all sides by roads (appropriately enough, insula means ‘island’). Instead of a central atrium for light and air, which was typical in most private homes at the time, the insulae had windows facing outwards at the city: in effect they were turned inside out. The first storey was built by installing many columns and then spanning relatively shallow arches between them. Concrete was laid over the curved tops of the arches to level them off and create a floor. Without the arch, far more columns would have been needed to support the floor beams, which would have created even tinier, more obstructed rooms.
To go higher, the Romans layered on more columns and arches. For the first time, they had to consider the design of foundations to ensure that their large, heavy structures didn’t sink into the ground. After studying the type of earth present under the proposed building, they constructed foundations made from stone and concrete to hold the structure up.
The most expensive, sought-after apartments were on the ground floor. The higher you went, the smaller and cheaper the dwellings became – which is of course the opposite of today: the height of luxury (literally) is a penthouse that will cost you a small fortune. The insulae were rather harried places: without elevators, residents had to trudge the stairs to the upper floors. Since water couldn’t be pumped that high, they had to lug clean water up with them, and drag their waste back down (although many would simply throw it out of the window). En route you might even encounter an animal: a cow is said to have wandered up to the third storey of such a block.
The insulae were noisy: even after glass windows were invented and replaced shutters, they couldn’t keep out the constant commotion of Roman streetlife. Before dawn, the bakers were out clanging their ovens. Later in the morning, teachers would be shouting out their lessons in the squares. All day you could hear the constant hammering of the gold beaters, the jangling coins of the money changers, the cries of beggars and of vociferous shopkeepers trying to strike a bargain. At night, dancing, drunken sailors and creaking carts added to the din. But worse than the noise and lack of sanitation was the fear that your building might collapse or burn down, as happened to a number of poor-quality blocks. The emperor Augustus instituted an early form of planning restriction, limiting the maximum height to about 20m (later adjusted by Nero to just under 18m), but these regulations were often disregarded. Despite the discomforts, by AD 300 the majority of Rome’s population lived in insulae. There were over 45,000 such buildings, and in contrast, fewer than 2,000 single-family homes.
For the first time in history, practical tall structures for hundreds of people, spread over many storeys, were built. It was a revolutionary idea – although it must have been a disconcerting experience for the first inhabitants, rubbing shoulders with their neighbours, and a bizarre sight for outsiders unaccustomed to this new way of living. This, though, was the future. This idea – humans living in layers on top of one another – was the start of what would eventually become the skyscraper.
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Archimedes took the Mesopotamians’ pulley and improved it. Similarly, the Romans took Archimedes’ innovation and applied it in new ways, creating heavy-duty cranes in the process. But advances in engineering don’t come just from picking up a tradition or innovation and taking it forward. Sometimes they are about breaking with tradition and thinking the impossible. I admire Leonardo da Vinci (1452–1519), for example, who envisioned flying machines, mechanical knights and even a famous concept for a bridge (made from short ladder-like units that could be assembled and disassembled quickly). Another such thinker was Filippo Brunelleschi (1377–1446), who singlehandedly – and, as you’ll see, single-mindedly – created one of the most famous domes in Renaissance architecture, and revolutionised construction in the process by building it without a supporting framework. Not bad for a man after whom people shouted, ‘There goes the madman!’
By Brunelleschi’s time, work on the Cattedrale di Santa Maria del Fiore in Florence had already been under way for more than 100 years. An edict of 1296 had proposed the construction of an edifice ‘so magnificent in its height and beauty that it will surpass anything of its kind built by the Greeks and the Romans’, and building began that same year, following designs by Arnolfo di Cambio (who was also responsible for two other great Florentine landmarks, the Basilica di Santa Croce and the Palazzo Vecchio). Despite the edict’s grandiose assertions, enthusiasm and civic energy – not to mention cash – waxed and waned in the following decades, and as a result it wasn’t until 1418 that the cathedral was finished – except for its dome. During construction, little thought had been given to how someone might place a dome on what was, for the times, a massive hole of 42m.
Brunelleschi’s Duomo in Florence, which caps the Santa Maria del Fiore cathedral in this Italian city.
Brunelleschi grew up close to the building site and its unfinished cathedral. Construction had been going on for so long that one of the streets by the site was now called Lungo di Fondamenti: ‘Along the Foundations’. As an apprentice, he learnt to cast bronze and gold, forge iron and shape and form metals. He later moved to Rome to study the techniques of his ancestors, the ancient Romans. Brunelleschi had always been drawn to engineering and made two resolutions as a young man: to revive architecture to the greatness of ancient Roman times, and to provide a dome for the cathedral. The chance to fulfil both resolutions presented itself when the authorities in charge of the structure ran a competition to find a suitable candidate to build the dome. But Brunelleschi was unlikely to win unless he could overcome the hostility his radical ideas engendered in lesser imaginations, and diplomacy was not his strong point. (On one occasion a committee reviewing his
designs had him forcibly ejected from their presence and thrown into the piazza, which is what earned him a reputation as a madman.)
The construction process of building an arch whereby a timber centering allows the stones to be placed in position, finishing with the all-important keystone.
It’s perhaps easy to understand why people denounced Brunelleschi’s claims that he had a new method of construction. For thousands of years, arches – and domes – had been built in the same way. Carpenters made a timber template or centering to match the shape of the underside of the arch. Stonemasons or bricklayers carefully added material around this template, often gluing the masonry together with some form of mortar. They started by laying brick or stone from the base, working their way slowly towards the centre of the arch. The final stage was crowning the arch with a keystone. Until the keystone was placed, the curved arms that sprung up from the base remained disconnected. The timber centering supported them; without it the arch would simply have collapsed. Once the keystone was placed, the pathway for the compression loads was complete, and the arch was stable. The centering could then be removed and the arch would remain standing. The construction of domes followed the same process, but used a hemispherical timber centering.
Everyone believed this was the only way to build a dome. Brunelleschi disagreed. He presented a model to the committee that was 2m wide and almost 4m high, made from 5,000 bricks, which he said had taken just over a month to complete and had been built without using centering. The claim was met with scepticism, especially since he refused to tell anyone how he had done it.
