Built

by Roma Agrawal

  Thankfully, these are mostly occasional occurrences. And ultimately I love what I do and believe that anyone can succeed in my field with persistence and resilience. I acknowledge that being in a minority can even have advantages – people tend to remember me after a meeting because I’ve spoken knowledgeably about concrete and cranes while wearing a chic dress and shoes. And it has provided some unusual opportunities to be a spokesperson for engineering, such as fashion and make-up shoots.

  My engineering idol: Emily Warren Roebling.

  I admire many engineers – I’ve talked about many of them in this book – but Emily Warren Roebling holds a special place in my heart. She understood technical concepts as well as any of the male engineers churned out by universities that wouldn’t admit women, yet she never trained as an engineer: she simply learned when she had to. Her brilliant communication skills earned her the respect not only of labourers on site but also of the highest-ranking politicians of the time. What’s more, pioneering innovations in engineering were implemented under her watchful eye.

  Being in a minority and working in construction has its difficulties in the twenty-first century, but Emily did all this at a time when most believed that womens’ brains were not even capable of understanding the complex mathematics and engineering she mastered. Her masterpiece, the Brooklyn Bridge, remains one of the most iconic symbols of New York.

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  From a very early age it was clear that Emily was extremely intelligent and had a keen interest in science. Despite a 14-year age gap, she shared a very close relationship with her oldest brother, Gouverneur K. Warren. He entered West Point military academy at 16 and then joined the Corps of Topographical Engineers, surveying for future railroads and mapping areas west of the Mississippi. He went on to fight with distinction in the American Civil War (a statue to him stands at the entrance to Prospect Park in Brooklyn). Warren was Emily’s hero. When their father died he assumed responsibility for his family, encouraging Emily’s interest in science and arranging for her to be enrolled in the Georgetown Visitation Convent, a preparatory school for women. There, she further explored her passionate interest in science, history and geography, as well as becoming an accomplished horsewoman. In 1864, during the American Civil War, Warren was posted far away, but Emily made the arduous journey to visit him and, during her stay, met Warren’s friend and fellow soldier Washington Roebling. Contrary to her usually balanced and sensible nature, she fell in love at first sight. Six weeks later, he bought her a diamond ring.

  Throughout the rest of the war, Emily wrote long affectionate letters full of details of her life. But Washington destroyed them soon after he read them, saying that the letters made their separation much more painful to him. Emily, on the other hand, saved everything he ever wrote to her, and in less than a year she had more than 100 letters containing all his thoughts, fears and affections. While he was away fighting in the war she visited his family, and they took a great liking to her. Finally, after 11 months of correspondence, Emily and Washington Roebling were married on 18 January 1865, and Emily stepped seamlessly and gracefully into the role of a typical Victorian housewife: tending to house and family in the shadows of her husband.

  Washington’s father, German-born John Augustus Roebling, was an accomplished engineer, and Washington planned to follow in his father’s footsteps. In 1867 John sent Washington to Europe to study building methods, one of which was inspired by the Romans.

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  The relatively light and small structures that the Romans built in the early years of their empire didn’t really need foundations because the ground was strong enough to carry them. But as they mastered the techniques of construction, their structures increased in size and weight, and the Romans learned that foundations were a crucial part of the design of their creations, which would otherwise move or sink. It was relatively easy to build foundations on land by digging out the soft earth and laying strong stone or concrete on the firmer, deeper layers of earth. Doing the same in a river, though, was – as you might imagine – more complicated. But being the inventors they were, the Romans came up with a solution.

  They sometimes supported their structures by driving piles made from logs into the ground. They inserted the piles using piledrivers: machines made from inclined pieces of timber connected together in a pyramid shape, and about two storeys tall. Pulleys and ropes attached to the apex of the pyramid allowed men or animals to raise a heavy weight. A wooden log was pushed into the ground as deep as could be achieved manually, and then the rope holding the weight was released, dropping it on top of the log and pushing it further. The process was repeated until the log was completely submerged.

  To create foundations in water, the Roman engineers started by using piledrivers to install wooden piles into the riverbed in a ring around the position of their intended foundation. They inserted two concentric rings of piles, and then packed the space between them with clay to seal it. The water within the ring was bailed out, leaving a dry area in which they could work. This sort of construction is called a cofferdam. It’s a technique still used today (in the Thames Tideway Tunnel, for example, as we saw in the previous chapter), but using large steel piles shaped like circular tubes or trapezoids.

  Building foundations in water the Roman way.

  Inside the dry cofferdam, Roman workers dug out mud until either they hit rock, or the cofferdam started leaking. On top of the strong ground they built a pier of stone or concrete in layers. (Using their special pozzolanic cement they were able to make solid concrete even in damp and soggy environments.) Once the pier was built, they piled rocks against the base to stabilise it further, then put mud back into the hole to its original level. The base of the pier or column and the pile of rocks were buried in the riverbed. The timber piles were then removed and water flooded back in. The workers continued to build the pier as high as it needed to be to support the bridge structure above.

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  The Roman cofferdams worked in places where the water was not too deep. But Washington Roebling wanted to know how to go deeper. Driving piles wouldn’t work because they would be really tall and wouldn’t be able to resist the push of the water. So he studied caissons.

  A caisson is a chamber with a watertight top and an open base, which penetrates into the mud of the sea- or riverbed. (You can picture this by pushing an upside-down tumbler into a pot of water that has sand at the base: the tumbler rim pushes into the sand while the sealed top keeps water from coming in.) One chute from the surface provides access to workers so they can descend into the chamber, and another is the passage through which they can take materials in and out. But if you want to really go deep into the water, there is another challenge. The further you descend, the greater the pressure of the water, and the harder it pushes against the walls of the caisson.

  The immense caisson used during the construction of the Brooklyn Bridge.

  To counteract this pressure, you can use a pneumatic caisson. These are ‘normal’ caissons with an added feature: compressed air is pumped into them. The pressurised air stops water from coming in and also balances the push of the water on the sides. An airlock gives workers access to the chamber. Engineers started to use these literally groundbreaking innovations to install foundations for bridges around the middle of the nineteenth century, and Washington Roebling was fascinated. He even considered using explosives in the confined space – a technique that, for obvious reasons, hadn’t been tried before.

  Emily began to assist her husband’s research, studying caissons alongside him, and using the scientific methods she had learned at the Georgetown Visitation Convent to understand bridge engineering. Little did she realise at the time, that the dangers of working in the highly pressured environment of a caisson would eventually lead to a catastrophic change in their lives, one from which Emily and her husband would both emerge very different people.

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  Until the late nineteenth century there was no bridge connecting Brooklyn
to the island of Manhattan, and although ferries shuttled back and forth across the East River, they were often halted during winter when the river froze over. So there was great pressure on the government to improve the situation. A bill was passed chartering the New York Bridge Company to do exactly that, and in 1865 John Augustus Roebling was appointed to design and make cost estimates for a bridge over the East River. They were to arrange for funds, which were to be split between the City of New York and the City of Brooklyn (which at the time were separate cities), along with private investors. Two years later, John Roebling began to lead the entire project.

  The central section of the bridge he designed took the form of a suspension bridge, which has some similarities to the cable-stayed form I used for the Northumbria University footbridge: both employ tall towers to which cables are attached. And in both types the cables are always in tension, which holds up the deck. However, the two bridges differ in the way the tension force channels itself into the ground.

  The journey of the forces in a cable-stayed bridge is direct. As the deck pulls down on the cables, putting them in tension, these cables, which are connected directly to the towers, compress the towers. In a suspension bridge, however, the weight of the deck pulls on cables that in turn pull downwards on another cable – a parabolic cable – which is suspended from the tall towers at each end. (Parabolas are curves with a particular shape – for the mathematically minded, if you plot a graph of y = x2, you get a parabolic curve.) The parabolic cable is anchored to foundations on the opposite side of each of the towers. The parabolic cable exerts a downward force on each tower, putting them into compression and channelling the forces into the foundations. This is the difference between the two types of bridge: cable-stayed bridges don’t have parabolic cables.

  Suspension versus cable-stayed.

  Work on the Brooklyn Bridge began in 1869, but disaster struck almost immediately. An accident on site left John Roebling with tetanus and he died a few weeks later, without even seeing the first stone of his spectacular structure laid.

  Washington Roebling was the natural successor to his father, and took on the role of Chief Engineer on the project. To sink the piers for the bridge, he made use of the caissons that had caught his imagination in Europe. But his were larger than any that had been used before, and he was also going much deeper under water. With layers of heavy stone on the lid, he drove two huge chambers – each 50m wide by 30m long – into the river, one on the New York side and another on the Brooklyn side.

  While this looked to be a reasonable engineering decision on paper, reality soon sank in. During the first month of excavation, progress was so slow that the engineers questioned whether they should give up and start again with a different approach. As columns of black smoke emanated from steam engines, and tar barrels, tools and stacks of stone and sand cluttered the site, reports began to surface from the workers about what it was like to be in the caisson.

  It was incredibly loud in the restricted space, and shadows darted everywhere; the pressure affected the workers’ pulses and made their voices faint. Every internal surface of the large chambers was covered with slimy mud, and the air was humid and warm. As the ground became more difficult to work with – constantly throwing up boulders through which the caisson couldn’t cut through – Roebling began experimenting with explosives. He worried about the quality of the air and how his design would affect his workers, not knowing at the time that his own health would soon be ruined.

  Over the next few months, having spent hours deep below the surface, Washington suffered exhaustion, temporary paralysis and deep pain in his joints and muscles. He had even hired a doctor to be on hand to supervise the condition of the men working in the Brooklyn caisson, which was deeper than the New York one. Without a full understanding of the health issues that he and his workers were facing, Washington shrugged off his symptoms and continued working. But even though the pain was temporary, the feeling of numbness in his extremities was not. He became a victim of caisson disease, in which nitrogen is released into the blood, causing acute pain (liable to make the sufferer double over, which is why the condition became known as ‘the bends’) and even paralysis or death. Now, of course, we understand the dangers of moving from high- to low-pressure environments too quickly – divers, for example, ascend at a rigorously controlled rate so the gas can be expelled. In 1870, however, caissons were a relatively new innovation and, although the engineers knew something about the dangers of working at depth, they had yet to determine the mechanism for avoiding injury.

  Washington was in constant pain – in his stomach, his joints and his limbs – and severely depressed. Ravaged by headaches, he was losing his eyesight and was upset by the slightest noise. But only he had the knowledge and ability to oversee the project in his father’s place. Nevertheless, Washington’s physical condition made it impossible for him to be actively involved; even normal day-to-day tasks were now a struggle. His mental state left him loath to speak to anyone except Emily. It seemed as though all the years of design and planning that the Roeblings had put into the bridge, and all the personal sacrifice they had endured, were going to count for nothing. Emily, however, had spent a long time with her husband and father-in-law, hearing about bridge design and engineering, and even helping with the technical research. Slowly, she began to get involved. It was, however, a huge step. The idea of a woman being involved in the project, and perhaps even leading it, was unprecedented. Apart from the doubts and mistrust everyone would likely feel for Emily – from the builders on site to the investors – did she herself have the confidence and resolve to act as a liaison between her husband and the site, let alone take over the role of Chief Engineer?

  With some background in science, but no detailed knowledge of bridge design, Emily began by taking extensive notes from her husband. She feared that he would not live to see the bridge completed. She then took over all correspondence on her husband’s behalf, regularly writing to the offices of the company. With unwavering focus, she started to study complex mathematics and material engineering, learning about steel strength, cable analysis and construction; calculating catenary curves, and gaining a thorough grasp of the technical aspects of the project. Emily was determined to see her family’s legacy built.

  She soon realised that these skills alone were not enough for her to successfully lead the project: she had to communicate with the workers on site, and the powerful stakeholders. So she began visiting the site every day, instructing the labourers on their work and answering their questions. She supervised the build and relayed messages between her husband and the other engineers working on the project.

  As Emily grew in confidence, she relied on Washington less and less. Her gut instincts guided her decisions and her blossoming skills helped her anticipate problems before they happened. Records of all work on site and responses to letters were diligently filed, and she tactfully represented her husband at meetings and social events. When bridge officials, labourers and contractors visited looking for her husband, she intercepted, answering their questions with authority and confidence. Most of them left satisfied, and many of them addressed all future correspondence to her – and in their minds she became the true authority. (At one point during the build, there were investigations into the honesty of some of the suppliers. In 1879, representatives of one of the contractors, the Edge Moor Iron Company, keen to allay suspicions, wrote a letter addressed to ‘Mrs Washington A. Roebling’ that made no mention of soliciting opinions from her husband.)

  Yet Emily conducted her work in Washington’s name. Rumours circulated that she was the actual Chief Engineer and the real force behind the bridge. News outlets made oblique references to her: the New York Star commented archly about ‘a clever lady, whose style and calligraphy are already familiar in the office of the Brooklyn Bridge’. During the entire period of construction, the Roeblings kept their home life strictly private – no magazines or newspapers were permitted to interview them.
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  Despite Emily’s careful handling of the project, problems started to proliferate. Costs mounted. Twenty men died from accidents and the caisson disease. Washington’s health showed no signs of improvement. The so-called ‘Miller Suit’ had been filed. Warehouse owner Abraham Miller sued the cities in charge of the bridge, demanding that they remove the structure in its entirety; claiming that it would divert trade to Philadelphia; challenging the cities’ ability to fund the project; and presenting a number of shipmasters, shipbuilders and engineers who would testify against the safety of the steel cables used in the bridge. Only the determined efforts of Senator Henry Murphy, a long-time supporter of Washington’s father, led to the suit finally being settled. Even the Roeblings didn’t escape accusation – it was claimed they had conducted questionable transactions with steel manufacturers, and they were investigated for accepting bribes, before eventually being cleared. The board of trustees overseeing the build changed and political dogfights broke out between new and old members. And then, in 1879, the Tay Bridge in Scotland – one of the biggest and most famous bridges in the world at the time – collapsed in a gale, killing 75 people. A headline in the New York Herald wondered: ‘Will the Tay Disaster Be Repeated Between New York and Brooklyn?’

  In 1882, despite Emily’s skilful and assured work on behalf of her husband, the Mayor of Brooklyn decided to replace Washington Roebling as Chief Engineer on the basis of physical incapacity. He passed a motion with the Board of Trustees to dismiss Roebling, calling for a vote at their subsequent meeting. After much argument, political wrangling, and reporting in the press, they gathered, debated, and cast their ballots.