Around 20 self anchored suspension (SAS) bridges are known to have been built around the world since the Deutzer Hangebrucke was opened in Cologne in 1915. The UK's only example is London's Chelsea Bridge, which dates from 1937.
Most recent examples have been footbridges, apart from Japan's 1987 Konahana Bridge and the Yeongjong Grand Bridge in Korea (BELOW), opened in 2000. These both have main spans of 300m and, like all other examples in the world, twin towers in the classic suspension bridge mode.
From a modern bridge designer's point of view the SAS concept has two main advantages. Its tower or towers will normally be significantly lower than an equivalent span cable stay crossing.
And, with no need for anchorages, an SAS span can be used for the main span of a long crossing, as on the Yeongjong Grand Bridge.
Against that must be set the cost and complexity of a deck structure that can resist the compressive forces involved.
Unlike cable stay decks, where compressive loads are fed in at intervals along the deck, an SAS deck is loaded at its extreme ends, and must be stiff enough to resist buckling forces. At Yeongjong this was less of a problem, as the steel deck truss is double decked, with heavy rail running inside the lower box.