Orthotropic deck
Encyclopedia : O : OR : ORT : Orthotropic deck
An orthotropic bridge or orthotropic deck is one whose deck material is an integral part of the bridge's load-bearing structure. Such decks, which integrate the bridge structure and the driving surface, are lighter and more efficient on long-span bridges than non-structural decks such as concrete. Such decks often include a driving surface of flat, solid steel plates stiffened by a grid of deck ribs and welded to framing members such as floor beams and girders.
Some very large cable-supported bridges (cable-stayed bridges and suspension bridges) would not be feasible without steel orthotropic decks. (The steel deck-plate-and-ribs system may be idealized for analytical purposes as an orthogonal-anisotropic 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 ripple to cables, towers, piers, anchorages, and so forth), the US has only about 60 such bridge decks in use as of late 2005. Many of them are in California, including the San Mateo-Hayward Bridge (1967) one of the first major bridges in the US to be built using an orthotropic deck. It is believed that concerns about delamination of wear surfaces, and deck fabrication difficulty issues (larger cranes are required than if the deck is built up from girder and beam components), have hindered adoption.
It is possible to refit a bridge originally designed with a concrete or non structural deck to use an orthotropic deck. For example San Francisco’s Golden Gate Bridge completed in 1937, the landmark bridge spanning the bay between San Francisco and Marin County, California, originally used a concrete deck. Salt carried by fog or mist had reached the rebar, causing corrosion and concrete spalling. In 1985, the Golden Gate 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 11,160 metric tons (12,300 tons).
External links
- [Orthotropic bridge conference] held in Sacramento, California in August 2004
- [Turner-Fairbark Highway research center] Orthotropic deck article from United States Department of Transportation website
- [Orthotropic Bridge organisation] list of bridges in the US that use Orthotropic decks.
- [Course outline] for a design of orthotropic bridges class.
- [Federal Highway Administration (US Department of Transportation) report] on automation of bridge deck section fabrication.
- [Chemco systems commercial site] describing Epoxy Asphalt Polymer Concrete, a wear surface material that addresses the delamination problem
- [Severn Crossing deck details] Illustrations include deck underside and weldpoint diagrams
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.