Image:US DOT Orthotropic Deck Fabrication.jpg An orthotropic bridge or orthotropic deck is one whose deck typically comprises a structural steel deck plate stiffened either longitudinally or transversely, or in both directions. This allows the deck both to directly bear vehicular loads and to contribute to the bridge structures overall load-bearing behaviour. The orthotropic deck may be integral with or supported on a grid of deck framing members such as floor Beam (structure) and girder . The same is also true of the concrete slab in a composite girder bridge, but the steel orthotropic deck is considerably lighter, and therefore allows longer span bridges to be more efficiently designed. The stiffening elements can serve several functions simultaneously. They enhance the bending resistance of the plate to allow it to carry local wheel structural load and distribute those loads to main girders. They also increase the total cross-sectional area of steel in the plate, which can increase its contribution to the overall bending capacity of the deck (i.e. the deck plate acts as a top flange in a box girder or I beam girder). Finally, the stiffeners increase the resistance of the plate to buckling A German Engineer Dr. Cornelis of MAN SE Corporation was issued German patent No. 847014 in 1948. MANs design manual was published in 1957 in German. In 1963 AISC published their manual based on North American design practices today called AASHTO. Image:GoldenGateBridge.jpg Some very large cable-supported bridges, plus current record span (cable-stayed bridge and suspension bridge ) would not be feasible without steel orthotropic decks. The longest or record span box girder , slant-leg bridge ; arch bridge ; movable bridge and two Norwegian Floating Bridges (The steel deck-plate-and-ribs system may be idealized for analytical purposes as an Orthogonality Anisotropy plate, hence the abbreviated designation “orthotropic.”) Thousands of orthotropic deck bridges are in existence throughout the world. Despite the savings and advantages (up to 25% of total bridge mass can be saved by reducing deck weight, as the weight reductions extend to cables, towers, piers, anchorages, and so forth), the US has only about 60 such bridge decks in use as of late 2005. About 25% of USA Orthotropic Steel Deck Bridges are in California, including the San Mateo-Hayward Bridge box girder 1967) one of the first major bridges in the US to be built using an orthotropic deck. Three "basic types"; movable bridge , are the swing bridge vertical lift bridge and bascule bridge The El Ferdan Bridge across the Suez Canal of Egypt is the record span bridge. The Erasmus Bridge has an orthotropic deck for both its cable-stayed bridge and bascule span. The Danziger Bridge of New Orleans is a very large vertical lift bridge. The Millau Viaduct a Cable-Stayed Bridge of Millau, France has the largest orthotropic steel deck area of any single bridge. The lower total gross weight of the superstructure allowed bridge launching from both ends of the Millau Viaduct The Akashi-Kaikyō Bridge s orthotropic deck allowed the Japanese to build the longest span at about 6000 ft or 50% longer than the Golden Gate Bridge The Italian Government is proposing to build a Messina Suspension Bridge 10,000 ft at the Strait of Messina between the Island of Sicily and Italy Orthotropic decks permit a very shallow deck depth which reduces the steepness of approach gradients and hence their costs. The form is also widely used on bascule bridge and other moveable bridge where significant savings in the cost of the mechanical elements can be made where a lighter deck is used. The unpopularity of the orthotropic deck relates mainly to its cost of fabrication, due to the amount of welding involved. In addition, it must be prefabricated rather than assembled on site, which offers less flexibility than in-situ concrete decks. Orthotropic decks have been prone to fatigue (material) problems and to delamination of the wearing surface, which, like the deck, is also often of a very thin material to reduce weight. It is possible to refit a bridge originally designed with a concrete or non-structural deck to use an orthotropic deck, which was first utilized in Vancouver Canadas Lions Gate Bridge For example, San Francisco’s Golden Gate Bridge completed in 1937, originally used a concrete Deck (building) Salt carried by fog or mist reached the rebar causing corrosion and concrete spall ng. In 1985, the bridge was restored using steel deck panels. The project not only restored the bridge to prime condition but also used fewer materials and reduced the deck weight by 12,300 ton (11,160 tonne .

See also

* Bridge deck

References

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External links

*http://www.orthotropic-bridge.org/ Orthotropic bridge conference] held in Sacramento, California in August 2004 & 2008. *http://www.tfhrc.gov/pubrds/05mar/06.htm Turner-Fairbark Highway research center] Orthotropic deck article from United States Department of Transportation website *http://www.orthotropic-bridge.org/Pages/USA.htm Orthotropic Bridge organisation] list of bridges in the US that use Orthotropic decks. *http://training.bossintl.com/html/design-orthotropic-bridges.html Course outline] for a design of orthotropic bridges class. *http://www.fhwa.dot.gov/bridge/automate.htm Federal Highway Administration (US Department of Transportation) report] on automation of bridge deck section fabrication. *http://www.chemcosystems.com/epoxy.html Chemco systems commercial site] describing Epoxy Asphalt Polymer Concrete, a wear surface material that addresses the delamination problem *http://iiw-wg5.cv.titech.ac.jp/case/Other%20cases/Severn.htm Severn Crossing deck details] Illustrations include deck underside and weldpoint diagrams *http://www.westernbridge.net/2009/3D.php Western Bridge Engineers Seminar]* orthotropic bridges of California *ftp://ftp.wsdot.wa.gov/public/Bridge/WBES2009/D/3D2/3D2.pdf orthotropic bridges of California]* Powerpoint

Foreign Language Search Terms -Examples Famous Bridges with Orthotropic Steel Decks

Dutch: Erasmus Orthotropic Bridge Erasmusbrug (Brug Bridge in Dutch) French: Pont Gustave-Flaubert (Pont Bridge and orthotrope orthotropic in French) German: Erasmus-Brücke (Brücke Bridge and orthotropen orthotropic in German) Brazilian Portuguese: The Juscelino Kubitschek Bridge (Portuguese: Ponte Juscelino Kubitschek) (Ponte Bridge in Portuguese) Italian Ponte sullo Stretto di Messina (Ponte Bridge in Italian) Norweigan: Nordhordland Bridge Nordhordlandsbrua (Brua Bridge in Norwegian) Category:Bridges fr:Pont à tablier en dalle orthotrope