The original idea for cable-stayed bridges goes back to 1595, according to the NOVA article; in a book called Machinae Novae, published in that year, a sketch of a cable-stayed bridge is clearly presented. Apparently no engineer took that sketch to be a possible bridge solution for hundreds of years because the first cable-stayed bridges were not constructed until the twentieth century (NOVA). A very good example of a cable-stayed bridge is the Sunshine Skyway Bridge in Tampa, Florida, which was built in 1988 and won the prestigious Presidential Design Award from the National Endowment for the Arts.
Robert Lamb and Michael Morrissey explain in the Discover Company's publication, Science / How Stuff Works, that the author of Machinae Novae was Croatian inventor Faust Vrancic. Lamb and Morrissey note that a cable-stayed bridge may, "at first glance," appear to be a cousin of the suspension bridge; but even though they both have "similar towers and hanging roadways" they are not the same. Cable-stayed bridges don't need anchorages and they don't need two towers either, the authors explain.
In a cable-stayed bridge, the cables run from the roadway "…up to a single tower that alone bears the weight," and the tower has the responsibility to absorb the "compressional forces" (Lamb, et al., 2011). Cables may be connected to the roadway in several places and all spiral up to a single point in the tower; Lamb compares the fact of several cables attached at different places on the roadway below to a high point above on the tower to "…numerous fishing lines attached to a single pole" (Lamb).
There are two basic types of bridges in the cable-stay category, according to Aileen Cho writing in Engineering News-Record (Cho, 2012, p. 2). There is the "fan" type and there also is the "harp" type in the cable-stay genre, Cho writes. Of the top 10 cable-stay bridges, all use the modified fan configuration instead of the harp configuration, Cho explains, because in the harp configuration there tends to be "…increased compression in the superstructure" (p. 2). In the fan type of cable-stay bridge the cable stays "…are spaced out over the top portion of the pylon" to allow more room "…to be individually anchored near the pylon top" (Cho, p. 2). While the harp model uses cable stays "…in equal spaces over much of the height of the pylon" and hence, it offers a "pleasant aesthetic appearance" albeit the harp style is not as efficient structurally (Cho, p. 2).
Advantages of Cable-Stayed Bridges
According to Robert Lamb and Michael Morrissey, cable-stayed bridges offer all the positives that go along with suspension bridges, but for cable-stayed bridges that have spans of 500 to 2,800 feet, they cost less to build. Moreover, cable-stayed bridges do not need as much steel cable as other bridges, they are quickly to construct and they "incorporate more pre-cast concrete sections" (Lamb, 2011).
The Top Five of the World's Longest Cable-Stayed Bridges
The Sutong Bridge -- which crosses the Yangtze River in China, is 1,088 meters, Aileen Cho explains. The Stonecutters Bridge spans the Rambler Channel in Hong Kong Harbor; it is 1,018 meters and was completed in 2009. Another long Chinese bridge, the Edong Bridge, which is 926 meters long, spans the Yangtze River at the Port of Huangshi; the Edong Bridge is aesthetically beautiful with harp-like cables connecting the highway with the pylons. It was completed in 2010. The Tatara Bridge, in Japan, crosses the Inland Sea of Japan to connect the main island in Japan, Honshu, with Shikoku. It is 890 meters and was completed in 1999; at that time it was the longest cable-stayed bridge in the world. The fifth longest cable-stayed bridge in the world, as of 2012, is the Pont De Normandie Bridge in Northern France; it is 856 meters and it spans the River Seine. (Cho, 2012).
Comparing Cable-stayed Bridges with Cantilever Bridges
For one thing, a cable-stayed bridge is less costly than a cantilever bridge (Weeks, 1996). Indeed, author Mark Denny explains that cantilever bridges "…tend to be massive and therefore expensive" (Denny, 160). Denny goes on to say that cable-stayed bridges "…have much in common with cantilever bridges"; in fact, Denny asserts, a cable-stayed bridge is really "…a cantilever bridge with cables added to relieve the load" (164). Since the cables of a cable-stayed bridge are "…distributed symmetrically about each tower," and hence the weight of the deck (highway or railroad tracks) supported by the tower is also symmetrical, Denny writes (164).
That having been said, Denny adds that there will be some asymmetrical loading with cable-stayed bridges because traffic differs from morning to afternoon. In the morning there may be heavy traffic on one lane of the bridge's road, and in the evening the traffic is heavy...
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