Built by Roma Agrawal
★ ★ ★ ★ ★
The wind blows, the ground shakes, and your home remains standing whether it is stick-built or a skyscraper of steel and concrete. There are specific reasons why this is the case, and structural engineer Roma Agrawal’s new book Built: The Hidden Stories Behind Our Structures explains in lucid prose just how that miracle comes about. It is a primer on how to build a structure that will endure.
This is a useful companion to Fallen Glory by James Crawford, a sobering look at how mankind has historically built fine structures and chosen to reduce those same buildings to rubble. In Built, Agrawal shows us how buildings, tunnels, and bridges are constructed. In doing so, she also reveals how pride or even small mathematical errors can lead to disasters. Her explanations of historical and modern building methods bring a perspective that is enlightening and entertaining, and range in subject from both Roman concrete to modern construction that allows a building to “float” over unstable ground.
Agrawal covers topics that range from building up structures to dreaming about what may be coming. She discusses the effects of force, fire, clay, earth, sky, and hollow. Simple line drawings reveal the grace behind even the most arcane, professional jargon. Her descriptions and comparisons are so compelling that it is difficult to decide which best convey the delight one receives from this book. The chapter on “force” is a good example: force comes from gravity and wind, so the weight and height of a structure are significant variables. The engineer who designs that structure must compute its weight and height, not to mention the properties of the materials being used and even the potential number of people who will be in or on the structure. Taller buildings and bridges sway to varying degrees. Their “resonance” is the tendency of a structure to quiver or vibrate from force (think what happens when a tuning fork is struck). Who knew, for example, that the frequency of the steel deck of the Northumbria University Footbridge, for which Agrawal designed the cables, “was close to the frequency of walking pedestrians, which meant it was in danger of resonating.” Too much movement would bring disaster; the Tacoma Narrows Bridge collapse in 1940 is an extreme example.
The chapter “Pure” notes that the structures Agrawal designs “are skeletons: until they have water, they are merely uninhabitable shells.” This leads to a brief history of how people have found fresh water and conveyed it to a place where it can be utilized. Even two millennia past, the Persians developed sophisticated means of finding water and retrieving it. Once found, means of storing it for later use had to be developed. We know the Romans built magnificent aqueducts, but few know of the even more magnificent Basilica Cistern underneath central Istanbul, and its immense walls that contain enough water to fill “32 Olympic-sized swimming pools.” Built in 532 AD, it still contains water within its beautiful walls and is a must-see for any tourist lucky enough to visit Istanbul. (Of course, many have already seen it in From Russia with Love and will remember it from the novel or film Inferno.) Agrawal ends this chapter with a visit to Singapore and its “Four National Taps”: “the four sources of water it will harness as efficiently as possible” in order to become nearly self-sufficient in water. Rainwater, continuing to import water from Malaysia, recycled water, and seawater are the means to that independence.
In the course of this most excellent book, Agrawal draws on her personal experiences in designing major bridges, The Shard in London, and other structures. Only thirty-three years old, she helps build big projects and is often the only woman on her design team. She can be found on TEDx, at various university and television presentations, or at her website: www.romatheenginer.com.