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Multi span suspension bridges

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The presentation provides a summary of a state-of-the-art review of the design and construction of multiple-span suspension bridges. Based on a paper by David Collings in ICE Proceedings, Bridge Engineering, September 2016.

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Multi span suspension bridges

  1. 1. Multiple Span Suspension Bridges State of the Art1 Summary presentation of a paper by David Collings published in ICE Proceedings; Bridge Engineering; September 2016. The full paper can be read at http://www.icevirtuallibrary.com/toc/jbren/169/3
  2. 2. Abstract The paper1 provides a state-of-the-art review of the design and construction of multiple-span suspension bridges; This presentation provides a summary of the key conclusions of the paper; Much of the recent work on this subject has been carried out in China, translations of the abstracts of some recent Chinese papers are included in an appendix to the paper; The full paper can be read at: . http://www.icevirtuallibrary.com/toc/jbren/169/3
  3. 3. Introduction Multi-span suspension bridges were relatively common during the initial development of suspension bridges in the 19th century when spans were modest and multiple spans were needed to cross major rivers. The paper outlines the work of previous generations together with a summary of modern research, with the aim of seeing more major multi-span suspension bridges being proposed.
  4. 4. Historical Review Multi-span suspension bridges were relatively common during the initial development of suspension bridges in the 19th century when spans were modest and multiple spans were needed to cross major rivers. It was known that such bridges were relatively more flexible than the single span suspension bridge. A number of methods were developed to stiffen multi span suspension bridges.
  5. 5. The earliest record of a multi-span suspension bridge is Samuel Brown’s Brighton Chain Pier, painted by Turner and Constable (this picture). This structure has four spans of 81m. It was constructed in 1823 and destroyed by wind in 1896.
  6. 6. In France in the early 19th century multi-span suspension bridges were also proposed and built to cross major rivers. One of the most impressive was the Dordogne Cubzac Bridge of 1839 with 5 spans of 109m, designed by Mark Seguin.
  7. 7. Dnper River Bridge The 6-span 700m long multi-span bridge across the Dnper River of 1853 was the longest length suspension bridge until the construction of the famous Brooklyn bridge in 1865.
  8. 8. Kiev Dnper Bridge was destroyed in 1920 by retreating troops. A new multi-span bridge with deep, shaped deck trusses was erected on the same foundations but also destroyed by war in 1941.
  9. 9. A number of multi-span suspension bridges were constructed in France, many no longer exist (see table 1). That the French engineers understood the problems of multi-span suspension bridges is evident from the cable layouts on these bridges, most of the French bridges have horizontal ties linking the tower tops.
  10. 10. For a classic 3-span suspension bridge with short side spans the behaviour is similar to the single span bridge. If all three spans are equal the deflections are 6 times those of the single span; . A 4-span bridge with short end spans gives deflections nearer those of a 2-span bridge. For a 4-span bridge with equal spans the deflection is 7 times as large as a single span; . The deflections increase as the number of spans but flattens out beyond 7 spans, as shown in figure 11. Suspension System Stiffness
  11. 11. For longer more modern multi-span suspension bridges such as the San Francisco Bay Bridge, Seto-Chuo Crossing and Kurushima-Kaikyo Bridges (see figure) the use of conventional single or 3-span bridges placed end on end has been the favoured solution. This solution retains the higher stiffness of the classic suspension bridge, but often requires the construction of major cable anchorages in deep water. Methods of Stiffening Multi-Span Bridges
  12. 12. Kurushima-Kaikyo Bridges
  13. 13. San Francisco Bay Bridge The options considered for the San Francisco Bay Bridge prior to the choice of a back to back structure illustrate some of the range of solutions (see figure 9).
  14. 14. There has been a recent resurgence of interest in multi- span cable stayed and extradosed2 bridges. Some of the problems and solutions relevant to cable stay bridges are similar to those of multi-span suspension bridges, and similar stiffening methods are often used. Other Multi-Span Bridge Problems
  15. 15. Recently the use of 2-span (3-tower) suspension bridges has been used for two major bridges over the Yangtze in China3. The 2-span bridge has a number of problems similar to those of full multi-span bridges. A significant amount of research has been carried out in China to solve some of the problems, such as construction methods and saddle slip.
  16. 16. Multi-span suspension bridges are appropriate for deep water crossings, and can be more economic than very long spans, their use is likely to continue to increase (figure 5); . The paper1 has outlined the work of previous generations, together with a summary of modern research on multi-span suspension bridges, with the aim of seeing more major multi-span suspension bridges being proposed for future estuary and sea crossings. Summary & Conclusions
  17. 17. References 1. Collings D (2016) Multiple-Span Suspension Bridges: State of the Art, Proc ICE BE 169(3), 215–231. http://www.icevirtuallibrary.com/toc/jbren/169/3 2. Collings D, Santiago A S, Extradosed and cable stayed Bridges: Exploring the boundaries, Proc ICE BE 166, 231-239. http://www.icevirtuallibrary.com/doi/abs/10.1680/bren.10.00058 3. Zhang M, Wang Y L and Wan T B (2015) Design and Static Analysis of the Taizhou Yangtzee River Bridge, China, Proc ICE, BE 168(1), 52–63. 4. Collings D, (2005), Steel-concrete composite bridges, Thomas Telford, London. 5. Collings D (2015) Long Span Bridges, http://www.slideshare.net/DavidCollings/long-span-bridges
  18. 18. Author David Collings BSc CEng FICE The author is an independent consultant and bridge designer; a writer 4 and also a researcher and associate lecturer at the University of Surrey on long span bridges 5.
  19. 19. Presentation by CRD and Wolf productions. The full paper can be read at http://www.icevirtuallibrary.com/toc/jbren/169/3

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