Steel bridges are one of the principal applications of steel materials. The world's first steel bridge, named the "Iron Bridge", was an arch type built in 1779 in Coalbrookdale, which is not far from Birmingham, England, and is known as the cradle of the coke blast furnace. This photograph shows a modern version of steel bridges, the Seto Bridge in Japan, which was completed in April 1988. The complete structure is composed of three suspension bridges, two cable-stayed bridges, four elevated bridges, and one truss bridge, and connects mainland Honshu with Shikoku island with total bridge length of 9,368m. The steel materials used to build the Seto Bridge amount to 660,000 tons. Particularly significant are the main cable wires supporting the suspension bridges, which are made of high strength steel with a tensile strength of 1.6 gigapascals, or four times the strength of ordinary carbon steel. As the size of structures increases the weight of the members also increases. For example, in the largest suspension bridge in the Seto structure(full length: 1,723m, central span: 1,100m), the bridge girders weigh 43,000 tons. Each of the main cables that support the suspension bridge requires 34,417 component wires of 5.1mm in diameter. Even when using high strength steel wires with a tensile strength as high as 1.6 gigapascals, these main cables have a diameter of 1.06m when stranded and a total weight of 25,000 tons. In the latest construction of the Akashi Bridge, even stronger steel wires with a tensile strength of 1.8 gigapascals have been employed for the main cables. Without the development of such high tensile strength wires, construction of the bridge was reportedly said impracticable due to the excessive weight of the cables. Higher strength materials make it possible to reduce the cross-sectional area of the members needed to support a constant load, and hence their weight. Therefore, the development of high strength materials is extremely important.