Abstract
Built: The Hidden Stories Behind Our Structures is an articulate and engaging book and an excellent introduction to the wonders of human-created structures. As a structural engineer with a specialty in high-rise buildings, Roma Agrawal uses her own experience on projects to illustrate the core concepts of how the structures work, and enlivens the discussion with the design challenges she faces to accommodate a range of performance requirements and site conditions using straightforward sentences and simple sketches.
Using examples of structures from around the world, past and present, she illustrates basic structural design concepts and practices. The first aqueduct created in Nineveh, Assyria, in the 8th century BC demonstrates the ingenuity needed to supply a growing urban center with potable water that needed to cross an intervening valley, with the resultant arched bridge structure that provided a continuous water flow with sufficient pressure. The foundation pilings in Tenochtitlan (now Mexico City) in 1325 illustrate the means through which the Aztecs could connect the island city in Lake Texcoco to the shore through constructed pathways on the piles. The Burj Khalifa in Dubai, which was the world’s tallest building in 2018, exemplifies the structural design innovations by Fazlur Khan, including structural exoskeletons and structural clustering that enables ultratall skyscrapers.
Stories on engineering innovators also abound, filling human faces into what could be fairly dry discussions. She clearly revels in Brunelleschi’s audacious design and execution for the cathedral dome in Florence, Italy, in the 15th century and Henry Bessemer’s flash of insight and subsequent struggles to refine the basic oxygen furnace for the mass production of steel in the 19th century. Her special engineering idol is Emily Warren Roebling, who worked with her husband Washington Roebling on the design and construction of the Brooklyn Bridge in New York City, overcoming daunting difficulties and mishaps that often injured her husband and workers, and in the process securing the respect and admiration of everyone with whom she worked.
Agrawal explores multiple types of structures, from buildings to bridges to tunnels, wells, and cisterns, reapplying the theories described in earlier sections to refresh the ideas with new applications, and building a coherent understanding of the means and methods to construct these creations. Descriptions of how construction materials are made from clay, metal, and concrete inform both the pathways of engineering development and the relative advantages or disadvantages of each type of material under different conditions. Discussions of pulleys, cranes, and tunneling equipment emphasize the effort and danger associated with many of these endeavors, and the contribution of equipment in making these structures possible.
She also provides straightforward desktop experiments that demonstrate basic structural design principles. For example, she uses a simple example of a book suspended from a string or supported by a paper tube to explain tension and compression. Later in the book, she builds an explanation of force distribution in masonry using strips of cardboard, which can be arranged and connected to explore the structural forces in domes.
A significant challenge for the book is its rather cryptic chapter titles, which range from structural concepts (such as “Force” in the first chapter) to structural materials to abstract concepts (“Pure,” “Clean”). The informality of the book is one of its charms, but its usability as a reference (particularly in a learning environment) would be greatly aided by a more detailed description of the contents of each chapter. For example, the third chapter in the book, “Fire,” starts with her personal experience with an explosion in a building, moves on to the progressive collapse of the Ronan Point apartment building in London in 1968, briefly considers the Great Fire in Rome in AD 64, and the explosion and collapse of the World Trade Towers in New York City on September 11, 2001. The following chapter, “Clay,” initiates the book’s consideration of specific structural materials, starting with the bricks developed in Jericho around 9000 BC, proceeding to Roman brick arches in ancient Pompeii, and including a discussion of mining, forming, and firing clay to create bricks.
“Metal,” the fifth chapter, opens with a description of the making of the Iron Pillar in the Qutb complex in Delhi, India, in AD 400 to establish the basis for a discussion of ductility, elasticity, and malleability of iron-based structural metals, followed by Henry Bessemer’s development of the basic oxygen furnace to enable the mass production of high-quality steel. Steel then plays a key role in her experience in the design of the cables and dampening springs for the Northumbria University Footbridge in Newcastle Upon Tyne, England. In “Rock,” the sixth chapter, Agrawal somewhat confusingly focuses on concrete (rather than, for instance, cut stone), but enthusiastically details the novel structural forms and systems made possible by the creation of cement, and its mixture with water and aggregate to create concrete. The story of Joseph Monier and his insertion of metal mesh in his cast concrete forms introduces structural concepts of composite tension and compression from embedding reinforcing steel in concrete, and its extensive use in current building systems.
The theme for the “Sky” chapter is somewhat difficult to discern, which starts with a brief description of her experience working on the Shard in London, and the role of pulleys and eventually elevators in the creation of high-rise buildings. In the middle of the chapter, however, she engagingly digresses into Filippo Brunelleshi and his design and construction methods for the Duomo on Santa Maria del Fiore in Florence, Italy, before proceeding on to current “megatall” buildings, including the Burj Khalifa in Dubai. “Earth” commences with the pilings underlying Mexico City, and current structural stabilizing efforts for the Metropolitan Cathedral in that city, while the subsequent chapter “Hollow” discusses the underground city of Deinkuyu, Turkey, and the tunneling technique developed by Marc Brunel for the Thames Tunnel in London, England, completed in 1843. Although the chapter “Pure” discusses water structural systems, including wells, aqueducts, and cisterns, “Clean” focuses on sanitary structural systems, specifically the London sewer system first designed and built in 1859 and the current upgrades. Agrawal briefly describes multiple approaches to bridge structures in the “Bridge” chapter, starting with the London Bridge completed in 1209, the pontoon bridge used by the ancient Persian King Xerxes in 480 BC, the Falkirk Wheel on the Union Canal in Scotland, to the cantenary bridge in Ishibune, Japan, before ending the book with a final chapter, “Dream,” proposing new advances in engineering concepts, materials, and methods for new structures.
In conclusion, this volume is an excellent introductory text to the concepts on constructed facilities, and would be a great read for middle school classes through early college, and for the general public. It has some unique contributions—specifically, the author provides examples from all over the world past and present (rather than most English-language books on structures, which are heavily Eurocentric and U.S.-centric), uses examples from her own experience, references many types of constructed facilities beyond buildings (such as cisterns), includes engaging stories about individual innovators, and provides hands-on experiments to demonstrate basic concepts. She also explicitly references the professional challenges of being a woman structural engineer and has a chapter on Emily Warren Roebling and her role in the Brooklyn Bridge design and construction, which is an excellent inclusion to broaden the appeal of the field to a more diverse audience.