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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 roadway applications it is usually a poured reinforced concrete slab, but can also be a steel grid or wood plank. The deck includes any road lanes, medians, sidewalks, parapets or railings, and miscellaneous items like drainage and lighting. The supporting structure consists of the steel or concrete system supporting the deck. This includes ...
Slabs are one of the greatest consumers of concrete in many buildings, [14] so reducing the slab mass can make a relatively large difference to the environmental impact of a building's construction. Biaxial slabs may be marginally cheaper than solid slabs, partly due to the lower mass.
The narrow section at mid-span gives the bridge profile a slight arch shape making this design particularly useful when large headroom is required. The profile also makes the bridge more architecturally pleasing than a beam bridge. Rigid-frame design may be the most efficient bridge type for spans between 35 and 80 feet (11 and 24 m). [5]
The simplest beam bridge could be a log (see log bridge), a wood plank, or a stone slab (see clapper bridge) laid across a stream. Bridges designed for modern infrastructure will usually be constructed of steel or reinforced concrete, or a combination of both. The concrete elements may be reinforced or prestressed.
In the deck-type bridge, a wood, steel or reinforced concrete bridge deck is supported on top of two or more plate girders, and may act compositely with them. In the case of railroad bridges, the railroad ties themselves may form the bridge deck, or the deck may support ballast on which the track is laid.
Single box girder bridge , flyover above eastern approach of the San Francisco–Oakland Bay Bridge. A box girder bridge, or box section bridge, is a bridge in which the main beams comprise girders in the shape of a hollow box. The box girder normally comprises prestressed concrete, structural steel, or a composite of steel and reinforced concrete.
The derivation of the maximum arching moment of resistance of laterally restrained concrete bridge deck slabs utilised Rankin's [21] idealised elastic-plastic stress-strain criterion for concrete, valid for concrete cylinder strengths up to at least 70N/mm 2, which he had derived on the basis of Hognestad, Hanson and McHenry's [23] ultimate ...