**9. Suspension bridges**

The carrying elements of a suspension bridge is a set of pylons and a rope in its natural catenary shape. It is assumed that the origins of suspension bridges are hidden in remote history. The tradition of the construction of narrow footpaths in Asia, especially in Tibet, is widespread. The first modern chain suspension bridge was built over the Menai Strait in 1826, connecting the Welsh island of Anglesey to the mainland. Its maker was brilliant bridge constructor Thomas Telford (1757–1834), see [20].

A turning point in the suspension bridge construction took place at the turn of the nineteenth and twentieth centuries in New York. An engineer constructing suspension bridges in the United States was German immigrant John Augustus Roebling (1806–1869) who also produced wire ropes. Roebling started developing the production of a seven-strand wire rope on a ropewalk that he built on his farm in Saxonburg, Pennsylvania. Next, he built a large industrial complex for the production of wire suited to the needs of the bridges he constructed. His first and significant bridge—Roebling cooperated with two other engineers—was the rail Niagara Falls Bridge which remained in use from 1855 to 1897. The span was 251 m. In 1866, Roebling built a 322-m span bridge in Cincinnati, **Figure 18**.

**Figure 18.** Roebling's suspension bridge in Cincinnati (1866) [21].

**Figure 19.** Suspension bridges in New York: left—Brooklin Bridge (1883), right—Williamsburg Bridge (1903) (*photo tak‐ en by Alicja Filipowska, 2015*).

Actually, it was a mixed system which nowadays is called the *hybrid suspension and cable stayed bridge*. In a manner of speaking Roebling *repeated* the above- mentioned bridge in New York in 1883. The bridge is called the Brooklyn Bridge. In this case, however, the main span amounted to 486 m. New Yorker Henry Hornbostel (1867–1961) built the Williamsburg Bridge in 1903, see **Figure 19**. This is a road bridge of eight lanes. The longest middle span amounts to 490 m.

**9. Suspension bridges**

14 Structural Bridge Engineering

Thomas Telford (1757–1834), see [20].

built a 322-m span bridge in Cincinnati, **Figure 18**.

**Figure 18.** Roebling's suspension bridge in Cincinnati (1866) [21].

*en by Alicja Filipowska, 2015*).

The carrying elements of a suspension bridge is a set of pylons and a rope in its natural catenary shape. It is assumed that the origins of suspension bridges are hidden in remote history. The tradition of the construction of narrow footpaths in Asia, especially in Tibet, is widespread. The first modern chain suspension bridge was built over the Menai Strait in 1826, connecting the Welsh island of Anglesey to the mainland. Its maker was brilliant bridge constructor

A turning point in the suspension bridge construction took place at the turn of the nineteenth and twentieth centuries in New York. An engineer constructing suspension bridges in the United States was German immigrant John Augustus Roebling (1806–1869) who also produced wire ropes. Roebling started developing the production of a seven-strand wire rope on a ropewalk that he built on his farm in Saxonburg, Pennsylvania. Next, he built a large industrial complex for the production of wire suited to the needs of the bridges he constructed. His first and significant bridge—Roebling cooperated with two other engineers—was the rail Niagara Falls Bridge which remained in use from 1855 to 1897. The span was 251 m. In 1866, Roebling

**Figure 19.** Suspension bridges in New York: left—Brooklin Bridge (1883), right—Williamsburg Bridge (1903) (*photo tak‐*

Actually, it was a mixed system which nowadays is called the *hybrid suspension and cable stayed bridge*. In a manner of speaking Roebling *repeated* the above- mentioned bridge in New York in Contrary to Roebling, he used a steel frame to raise towers. In this case, the suspension ropes were vertical that became the classical solution for many years. In 1927, Swiss-American engineers Othmar Ammann (1879–1965) and Cass Gilbert (1859–1934) built the double-deck George Washington Bridge. Its middle span amounts to 1067 m. The Mid-Hudson Bridge was built in 1930. The chief engineer was Polish immigrant Ralph Modjeski (1861–1940). The longest span is 910 m, see [22].

The most famous American suspension bridge is naturally the Golden Gate Bridge, constructed in 1937. Its total length amounts to 2737 m, while the main span 1280 m, **Figure 20**.

**Figure 20.** Golden Gate Bridge, 1937: (a) side view; (b) road traffic (*photo by Alicja Filipowska, 2015*).

At present, the Akashi Kaikyō Bridge (Japan) has the longest central span of all suspension bridges—it is 1991 m long.

All the above-mentioned bridges have truss platforms. It is a proven and reliable solution. Simultaneously, suspension bridges with plate girder deck were constructed such as the Tacoma Narrows Bridge, for instance. The length of its main span amounts to 853 m. The bridge was opened for traffic on 1 July 1940. On 7 November 1940, the catastrophe stuck—and was filmed. The cause of it was the so-called aeroelastic flutter effect. For this reason, the bridge is unofficially known as *Galloping Gertie*. The studies and analyses conducted at that time showed that truss load-bearing structures should be used [23]. Nowadays, when the advanced finite element method (FEM) procedures are available, it is easy to demonstrate by means of numerical analyses that the causes of the catastrophe were correctly identified.

In 1966, the bridge over the Severn Bay near Beachley in Scotland was built. It is a low profile box carrying deck structure. The middle span is 988 m long. An unusual feature of the suspension cables carrying the deck is that they are not vertical, but arranged in a zigzag pattern. The diagonal arrangement of hangers—as compared to vertical ones—increase the dynamic stiffness that is additionally supported by tuned mass damper-harmonic absorbers. The deck is an orthotropic steel box of the aerofoil shape. The bridge was tested and approved by the designers Freeman, Fox and Partners following wind tunnel tests.

The First Bosphorus Bridge constructed in Istanbul in 1973 is a replica of this bridge. The main span—the distance between the towers—is 1074 m, **Figure 21**. When opened, it was the second bridge crossing between Europe and Asia constructed since 480 B.C.

**Figure 21.** First Bosphorus Bridge: (a) side view; (b) tower and aerodynamic low profile deck.

Currently, the construction works of the third Bosphorus bridge—Yavuz Sultan Selim Köprüsü —are underway, according to the design by Michel Virlogeux and Jean-François Klein. The bridge has been designed as a hybrid structure.
