Segmental bridge

A segmental bridge is a bridge built in short sections (called segments), i.e., one piece at a time, as opposed to traditional methods that build a bridge in very large sections. The bridge is made of concrete that is either cast-in-place (constructed fully in its final location) or precast concrete (built at another location and then transported to their final location for placement in the full structure).

Segmental bridge
AncestorBox girder bridge
RelatedPrecast Segmental Bridge
CarriesTraffic
Span rangeLong
MaterialConcrete
MovableNo
Design effortHigh
Falsework requiredYes

These bridges are very economical for long spans (over 100 meters), especially when access to the construction site is restricted. They are also chosen for their aesthetic appeal.

History

The first cantilevered segmental cast-in-place concrete bridge, built in 1930, was Ponte Emílio Baumgart across Rio do Peixe in the state of Santa Catarina of Brazil [1]. It was followed in 1951 by the prestressed concrete bridge across the Lahn River in Balduinstein, Germany, the first of many cantilevered bridges designed by Ulrich Finsterwalder.

The first prestressed concrete bridge, assembled by several precast elements, was the Pont de Luzancy across the river Marne in France, built according to the design by Eugène Freyssinet and commenced in 1940, but due to the war, completed only in 1946.

Construction

The sequence of construction is similar to traditional concrete bridge building, i.e., build the support towers (columns), build the temporary falsework, build the deck, perform finish work. The principal differences are as follows:

  1. The support towers may be built segmentally. Often this is accomplished using "slip-form" construction, where the falsework moves (slips) upward following sequential concrete "pours." The falsework uses the newly constructed concrete as the basis for moving upward.
  2. After the towers are built, a superstructure is built atop the towers. This superstructure serves as the "launching" point for building the deck. (The deck is often built in both directions away from the tower, simultaneously.)
  3. The deck is now constructed sequentially, beginning at the tower, one section at a time. This process is usually accomplished using a self propelled bridge layer that hoists the bridge section into place.
    • In cast-in-place bridges, the falsework is connected to the previously installed concrete and allowed to cantilever freely. Next, the permanent reinforcing steel and supports are installed. Finally, the concrete is placed and cured, freeing the falsework to be moved.
    • In pre-cast bridges, the concrete segment is constructed on the ground, and then transported and hoisted into place. As the new segment is suspended in place by the crane, workers install steel reinforcing that attaches the new segment to preceding segments. Each segment of the bridge is designed to accept connections from both preceding and succeeding segments.
  4. The process in step 3 is repeated until the span is completed.
Segmental bridge under construction, Ft. Lauderdale, Florida, USA.
The Pierre Pflimlin bridge being built over the Rhine south of Strasbourg.

Notable examples
gollark: Combining the totally economical launch costs and probably loss of power to transmission of orbital solar with the wide public acceptance of nuclear power!
gollark: Bad idea #12589172598: orbital nuclear power plants.
gollark: Nuclear fission is pretty great too. We should do more of that.
gollark: I mean, orbital launch is not cheap, though in space you benefit from the shorter nights.
gollark: As of now, wouldn't it probably be better to just find some abandoned desert, stick a lot of solar panels there, and somehow run power cables back to somewhere useful?

References
  1. Girard, L. (1931): Le pont de Herval au Brésil. In: La Technique des Travaux, v. 7, n. 11 (November 1931). The Instituto Militar de Engenharia, provided a free pdf copy of the original magazine article at http://aquarius.ime.eb.br/~webde2/prof/ethomaz/baumgart/rev_travaux.pdf
  2. Two kilometer span bridge over the River Kosi in Bihar, India : http://www.spsc.co.in/Ongoing-Projects.aspx

Further reading
  1. LoBuono, J. (2005). "Assembly required-The instructions for building New Jersey’s first segmental bridge." Chicago, Illinois: GoBridges.com. September/October. Published October 18, 2005 at https://web.archive.org/web/20071014060418/http://www.gobridges.com/article.asp?id=770
  2. (2006) "Design & Construction of Ngong Shuen Chau Viaduct" International Conference on Bridge Engineering – Challenges in the 21st Century, Hong Kong, 1 ~ 3 November 2006 http://www.ywlgroup.com/Articles.html
  3. Liu, Xian Peng; Qin, Zong Ping; Leung, L. W.; Yue, Lingling (2007). "Construction of the Precast Segmental Approach Structures for Sutong Bridge" (PDF). ICE Conference 2007. Beijing, China: YWL.
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