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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 structure's overall load-bearing behaviour. The orthotropic deck may be integral with or supported on a grid of deck framing members such as floor beams and girders. Decks with different stiffnesses in longitudinal and transverse directions are called 'orthotropic'. If the stiffnesses are similar in the two directions, then the deck is called 'isotropic'. The steel deck-plate-and-ribs system may be idealized for analytical purposes as an orthogonal-anisotropic plate, hence the abbreviated designation “orthotropic.” ==Discussion== The stiffening elements can serve several functions simultaneously. They enhance the bending resistance of the plate to allow it to carry local wheel loads 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 or I beam girder). Finally, the stiffeners increase the resistance of the plate to buckling. The same structural effects are 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. Resistance to use of an 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 problems and to delamination of the wearing surface, which, like the deck, is also often of a very thin material to reduce weight. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Orthotropic deck」の詳細全文を読む スポンサード リンク
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