In the wake of Tacoma: Suspension bridges and the quest for aerodynamic stability

"In the Wake of Tacoma: Suspension Bridges and the Quest for Aerodynamic Stability", Richard Scott. American Society of Civil Engineers ASCE Press, 2001, USA, Reston, Va. ISBN 0-7844-0542-5.
On 7 November 1940 the world’s third-longest suspension bridge, the newly completed Tacoma Narrows Bridge, collapsed during a gale. This calamity was at once the most widely noted bridge failure anywhere and a severe shock to the structural engineering profession. The Tacoma Narrows Bridge was the work of one of the most respected suspension bridge engi- neers of the first half of the twentieth century and represented the culmi- nation of new theories of suspension bridge design that had been applied to a growing number of major spans. In this exceptionally thorough work, Richard Scott delves deeply into the complex origins of the failure and the flaws in the so-called deflection theory upon which the design was based. He then takes us on a comprehensive survey of the extraordinary progress in suspension bridge design and construction over the subsequent six decades that owe so much to the lessons of Tacoma Narrows.
Scott begins the story with a brief review of the origins of the modern suspension bridge, pointing out the similarities to Tacoma Narrows in some notable nineteenth-century failures whose lessons were either ig- nored or never fully understood. John Roebling’s great Brooklyn Bridge of 1883 and the notable suspension spans of the first several decades of the twentieth century depended upon deep stiffening trusses to maintain their stability under wind and traffic loads. Under the deflection theory, devel- oped early in the century, the principal requirement of the trusses was to distribute local live loads to the main cables and avoid local grade changes, permitting substantial reductions in their size. By the 1930s this design approach had evolved to the use of plate girders that were breathtakingly shallow by comparison to the trusses of earlier practice.
Scott gives us a good account of the long period of research into the aerodynamic characteristics of suspension bridges that followed the collapse, as well as the new era of spectacular achievement by bridge engineers that it helped to make possible. This post-Tacoma era is covered in chapters that range across such topics as Mackinac Straits and Verrazano-Narrows; European innovation that included a new concept of box-girder suspended structures that would see worldwide application; and the remarkable development of bridge engineering in Japan which brought forth what currently ranks as the world’s longest suspension span, the 1,780-meter Akashi Kaikyo Bridge of 1998. Scott concludes with a long look at the many still greater sus- pension spans that have been proposed for such formidable crossings as the Straits of Messina, the Dardenelles, and the Straits of Gibraltar (taken from: W.D. Middleton).