Engineers of Dreams: Great Bridge Builders and the Spanning of America

by Henry Petroski

  A Currier & Ives print, circa 1886, showing the Brooklyn Bridge across the East River and the Statue of Liberty in New York Harbor (photo credit 1.4)

  Bridge designs cannot evolve the way the Statue of Liberty or glass-faced high-rise buildings do, from the artistic outside in. A great bridge is an engineering structure first, and only when its structural integrity has been established on the drawing board and through elaborate engineering calculations can architectural embellishments be considered. This is not to say that architects have no role in bridge design, for bridge engineers have a strong tradition of involving architects as consultants. Many of the distinctive visual features of the Golden Gate Bridge, including its sculpted towers and color, are owing to the involvement of the consulting architect, Irving F. Morrow.

  The George Washington Bridge, when it was conceived in the 1920s, was to be twice as large as any existing suspension span, and so the towers had to be as tall as skyscrapers. Such massive structures demanded some special treatment, it was felt, and no less an architect than Cass Gilbert, designer of New York’s Gothic-style Woolworth Building, was involved in the design of their façade. The full story of the George Washington Bridge will be told later in this book, but it is not giving away too much to say that the architectural stone façade was never applied to the towers, whose bare steel forms stand today as one of the masterpieces of modern bridge engineering. Imagine what the George Washington Bridge would look like with stone applied, and imagine what might have been its influence on later suspension bridges, almost all of which have been built with steel towers. Each great bridge influences each later one, and that is why it is necessary to understand the history of bridges and their engineers in order to understand present and future spans and perhaps something of their builders.

  When the proportions of ancient bridges, having been arrived at by trial and error, were codified in stone according to rules that such architects as Vitruvius and Palladio prescribed for buildings, then bridges could be designed as architectural edifices. Even the great Roman aqueducts, such as the Pont du Gard in southern France, could be built with little calculation of the kind required for designing a modern bridge, for each of the individual semicircular arches could be supported by the massive piers on either side of it, and construction was more or less a matter of piling arches like blocks one beside and one upon another until the valley was filled with bridge to the desired level. Though superficially analogous processes can be said to suffice for bridge building today, now each step in the construction must be weighed so that the incomplete structure is as able to support itself as the completed bridge. Because this simple fact was overlooked, the Quebec Bridge over the St. Lawrence River, planned to be the largest of its kind, spontaneously collapsed while under construction in 1907. Great suspension bridges can be constructed without falling only because elaborate engineering calculations determine the precise order in which the parts, which individually might weigh as much as a large locomotive, will be assembled.

  The modern bridge-building era began in the late eighteenth century, with the daringly shallow stone arches built over the Seine by the French engineer Jean-Rodolphe Perronet, and with the revolutionary use of iron in British bridge building. What is generally considered the first iron bridge was built in 1779 across the River Severn at Coalbrookdale, where increasingly larger iron castings had been made by the Darby family of founders. The first iron bridge mimicked a stone arch, with connection details that suggested timber construction. When wrought iron became available in larger quantities and pieces, these were formed and assembled into chains to support a bridge that worked not on an arch but on a suspension principle. The increasing use of iron in bridges of ever-greater span led to increasingly innovative and daring designs, which more than once over the course of the nineteenth century culminated in a colossal failure. However, as the Victorian era was drawing to a close, advances in engineering, mathematics, and science had given bridge engineers a perspective and a collective set of tools that enabled them to tackle with confidence and success problems of bridging that had once been thought impossible.

  This book is about how the late-nineteenth- and early-twentieth-century engineers did what they did to leave us a legacy of bridges that define our material environment, shape our cities, suburbs, and rural areas, and ordain our routes of communication over distance and time. That period of great bridge building, especially in America, coincided with the rise of the engineering profession, and so the story of bridges provides an excellent vehicle also for understanding the development of the engineer and engineering generally. How the engineer interacted with society in the process of conceiving, promoting, financing, designing, and building bridges serves as a paradigm for appreciating the nature of engineering endeavors, and thus provides a basis for understanding how technology and society interact today and can be expected to interact in the future. No bridge is an island, entire of itself, and the story of any bridge is the story of every bridge in that it involves a plethora of characters and circumstances. By considering the stories of a few of the most significant, though not necessarily the best-known, engineers and the bridges that they conceived and built over the last century or so, we can come to understand more fully the nature of the interaction of the engineer with the rest of society, of the relationship between technology and the rest of the stuff and ideas of the world.

  From another viewpoint, fully understanding how bridges have been conceived, financed, and built requires a fully integrated view of technology, society, and culture. The financial link is often the crucial metaphorical span between the dream and reality of an actual bridge. Many a wonderful concept, beautifully drawn by an inspired structural artist, has never risen off the paper because its cost could not be justified. Most of the great bridges of the nineteenth century, which served to define bridge building and other technological achievements for the twentieth century, were financed by private enterprise, often led by the expanding railroads. Engineers acting as entrepreneurs frequently put together the prospectuses, and in some cases almost single-handedly promoted their dreams to the realists. In the early twentieth century, in larger cities like New York, there were needs for bridges to move citizens, increasingly in automobiles, from homes to workplaces and back, across rivers and bays that were becoming choked with ferryboats and other water traffic and sometimes ice, and so local and state governments began to get more and more involved in the building of great bridges. Debates over how to pay for them were common. When the Delaware River Bridge, now known as the Ben Franklin Bridge, was under construction in the mid-1920s, an argument between Philadelphia, which wanted a free bridge, and Camden, New Jersey, which wanted to collect tolls, brought progress on the structure to a standstill.

  The stories of the building of great long-span bridges coincide with the rise of the steel industry. Beginning with the Eads Bridge, whose requirements for steel were almost too demanding for the fledgling industry and its up-and-coming barons, like Andrew Carnegie, the desire for stronger and stronger materials to make ever larger and relatively lighter structures drove research and development among competitive suppliers. Later, the introduction of concrete, first reinforced and subsequently prestressed, as an alternative to steel in some structures, provided a new element of competition that remains to this day. Whether a bridge should be steel or concrete in some cases can be a toss-up financially, and the decision becomes one of aesthetics, maintenance, or technological preference.

  Though it is true that no individual engineer, no matter how great, can single-handedly do everything—from detailed calculations to supervision of construction—required to bring a major span to fruition, great bridges do appear to have had masterminds behind them, albeit masterminds with many helper minds. Indeed, the stories of the great bridges built in the half-century or so between the 1870s and the 1930s, the era when length records were set that remain unsurpassed or just barely surpassed today, are stories of recurring characters, both major an
d minor, who seem to have played a role in almost every bridge of any significance that was constructed during the period in which they flourished. There was also a necessarily large cast of supporting engineers, of course, and their roles in the realizations of dreams will be seen to be no less significant. However, the main action shows that a few handfuls of leading engineer-entrepreneurs, by the force of their personalities, talents, ambitions, and dreams, rose to or seized the leadership roles during the era of great bridge building. Yet these great engineers were also as much a product of the opportunities and circumstances of their times, which they often influenced themselves, as of their dreams and talents.

  If the stories of bridges begin in dreams, they often reach a climax, at least formally, in celebration. The completion of a great bridge, especially one linking what theretofore had been so close to the eye and yet so far from the body, has traditionally been cause for celebration. The formal opening of the Eads Bridge on July 4, 1874, which began with a huge parade in the morning and closed with a grand display of fireworks in the evening, set the standard for subsequent American bridge openings. The opening of the Brooklyn Bridge in 1883 was the subject of many a lithograph, and its spectacular fireworks show was recalled by an equally spectacular one on the occasion of its centennial in 1983. Great suspension bridges and celebrations seem especially to go together, and the clearly distinct stages of construction provide various opportunities to acknowledge progress and achievement. Discrete ceremonies often mark the topping out of towers, the completion of foot-walks for cable spinning, the finishing of the cables, and the placement of the final segment in the roadway.

  A special rivet was put in place by the Prince of Wales when the Firth of Forth cantilever bridge was opened in 1890. Though the engineers, bankers, and politicians are often joined only by the press on such occasions, the opening ceremonies of a bridge can also be a veritable test of the bridge itself. Pedestrians have traditionally had the run of bridges on their first day, and re-created walks across them have marked their anniversaries. Throughout the course of its opening day, May 27, 1937, which was designated Pedestrian Day, about two hundred thousand people had the Golden Gate Bridge all to themselves, and they walked leisurely between San Francisco and Marin County. To celebrate the fiftieth anniversary of the bridge, another Pedestrian Day was held in 1987, and of the half-million or so people who showed up all at once, only a couple hundred thousand could get onto the bridge’s main span at one time. It turned out to be the heaviest load the bridge had ever experienced, and the structure was visibly strained under the weight.

  The Golden Gate Bridge, on the occasion of Pedestrian Day in 1987, marking the structure’s fiftieth anniversary (photo credit 1.5)

  Unfortunately, our thoughts about bridges often end the day after such celebrations, and we tend to take these structures, once thought impossible to finance or build, for granted. Yet bridges are affected by their environment no less than people are, and the wear and tear of traffic, pollution, abuse, neglect, and just plain old age take their toll. It is implicit, and often made quite explicit, in the design of every product of engineering that there are limits to its health and strength, and therefore limits to what it can be subjected to. A recognition of those limits and regular checkups and inspections of the artifact are required, as is a certain amount of preventive maintenance and repair. To neglect this common sense is to find ourselves in the position in which we now are in America, with roughly one out of every five of our bridges said to be structurally deficient. A familiarity with the stories of our bridges not only can bring a fuller appreciation of their rich history and significance, along with an appreciation and understanding of the humanity of engineers and of engineering generally, but also can promote a greater enjoyment and pride in the contribution of bridges to our physical and cultural infrastructure, and a sense of obligation to maintain them. Imagine what our lives would be without bridges.

  EADS

  James Buchanan Eads was born on May 23, 1820, in Lawrenceburg, Indiana, which is in the southeastern part of the state, near the Ohio border, just a few miles west of Cincinnati, and, like that Queen City, on the Ohio River. The third child of Ann Buchanan and Thomas C. Eads, he was named after his mother’s young cousin, soon to be a Pennsylvania congressman, who in 1857 would become the fifteenth president of the United States. Thomas Eads was a businessman looking for a business in which to succeed, and this led the family to move first just up the Ohio River to Cincinnati; then, when James was nine years old, down the Ohio to Louisville, Kentucky; and, finally, farther down the Ohio, along southern Illinois, to where the Ohio meets the Mississippi, and up that legendary river to St. Louis.

  The accident of his birthplace and his forced travel on two of the most important waterways of the time seem to have greatly influenced young Eads, and he would spend most of his adult life engaged in pursuits that would keep him over, in, under, and around water. He would devise some of the grandest schemes of the nineteenth century to raise great masses of sunken riverboat cargo from the bottom, to flush the silt and sand from the entire middle of a continent out the mouth of the Mississippi, to build a bridge over a river that many said could not be crossed, and to carry fully laden oceangoing ships across the land between the seas. Of these dreams of James Buchanan Eads, only the last was not to be realized.

  Young James, his two sisters, and their mother actually went ahead to St. Louis in September 1833, where she was to set up a household before the father arrived to open a general store in the bustling city. James is reported to have been fascinated by the riverboat voyage, and by the vastness and vitality of the Mississippi River. He is said to have told his mother then that he would build a steamboat in St. Louis, which seemed a reasonable ambition for a boy who had already built a model of a steamboat able to cross a pond, as well as models of steam engines, sawmills, and fire engines, in a small workshop that his father had fitted out for him in Louisville. The young lad is said also to have whispered something to himself on the Mississippi on the way to St. Louis, something that even his mother might have found more an idle dream than a possibility: “This is going to be my river.”

  First, however, the Eads family was to be the river’s, for, while they lay asleep on the last night of their voyage, as the riverboat approached St. Louis, a fire broke out on board. To escape the smoke filling the confined spaces of the boat, the passengers rushed to the railing, from which they could see the city before them and feel the fire behind. The boat did remain afloat until it reached the dock, upon which the Eads family and other passengers then stood helplessly watching their possessions go up in flames. However, with the few resources with which she had escaped, Mrs. Eads was able to rent the upstairs of a house that faced the river. It was evidently large enough for her to take in boarders and so bring in some income.

  Although he had attended school up until that time, thirteen-year-old James could not continue his education in St. Louis, because he had to work to help support his family. At first he sold apples to bring home some money, but soon he found a more substantial opportunity as a “boy-of-all-work” in the Williams & Duhring dry-goods store run by Barrett Williams, one of the men who took meals at Mrs. Eads’s boarding house. James was evidently a bright, energetic, and well-mannered employee, to whom Williams took a liking. Thinking it a pity that someone like young James could not go to school, Williams gave his loyal worker the run of his library, which was located in a room above the store. James was told that in his spare time he could read at will among the books, which included works on physical science, mechanics, machinery, and civil engineering.

  Had young Eads wanted to study engineering formally at this time in America, he would have had virtually no opportunities close to home, and thus it is hard to imagine a better opportunity, especially in the St. Louis area, than the one given him by Barrett Williams. Though an engineering school had been called for by General George Washington as early as 1778, the Military Academy did not become
firmly established at West Point until 1802. There were only the beginnings of a few other formally established courses in engineering in the early 1830s, let alone schools where a young man like James Eads could get a degree in civil engineering.

  There were, of course, the likes of the Franklin Institute, established in Philadelphia in 1825, where lectures on applied science and mechanics were offered, often in the evening and aimed toward individual betterment rather than toward a degree. Also, up and down the East Coast, there were the beginnings of what might have developed into engineering schools. In Vermont, in 1819, Alden Partridge, who in 1813 at West Point had become the first individual to hold the title of professor of engineering in the United States, established the American Literary, Scientific and Military Academy, which later was renamed Norwich University. Courses in civil engineering were offered there as early as 1821. In Maine, in 1822, Robert H. Gardiner started a lyceum that bore his name and offered courses of study preparatory to engineering, but it survived for barely a decade.