ABSTRACT
Suspension bridges are graceful and aesthetic. More importantly, they are efficient and economical structures for the lengths they span. The basic concept is not new: China reportedly used this concept as early as 200 BC. The development of the suspension bridge concept has been steady, and there are numerous examples that can be cited. Improvements in materials led to the first chain suspension bridge in Europe in 1741 (Winch Bridge, near Bowleed in UK). Later, an improved version was constructed in the United States, supported by iron chains similar in profile to today’s bridges, which remained in service from 1801 to 1833 (Jacobs Creek Bridge, just south of Mount Pleasant, Pennsylvania). Continued improvements led to the use of wire cables and deployment of suspension bridges over larger spans. The Wheeling Suspension Bridge in Ohio (1010 ft tower to tower) was constructed in 1849 and is still in service. In 1854, a windstorm destroyed the deck through torsional and vertical movements. The deck was rebuilt, and subsequently, stay cables were added in 1871. Aerodynamic issues were not fully understood at that time, as became evident later with the collapse of the Tacoma Narrows Bridge in 1940. The Bronx-Whitestone Bridge was, like the Tacoma Narrows Bridge, built with a slender profile susceptible to aerodynamic problems. Improvements to the behavior of the bridge in high winds were achieved with the installation of a stiffening truss in 1941 and a tuned mass damper in the mid-1980s. Further improvements were achieved with the replacement of the bridge deck, relocation of the bridge lateral bracing, and installation of fairing. With every new suspension bridge constructed, the lessons learned from previous bridge performances have been incorporated, leading to an ever-improving design for suspension bridges. At present, the Akashi Kaikyo Bridge, which connects the city of Kobe on the mainland of Honshu to Iwaya on Awaji Island in Japan, is considered the longest suspension bridge in the world, with a central span of 1991 m.
