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Compared to traditional solid slabs, the reduced self-weight of biaxial slabs allows for longer spans and/or reduced deck thickness. The overall mass of concrete can be reduced by 35–50% depending on the design, [ 1 ] as a consequence of reduced slab mass, as well as lower requirements for vertical structure and foundations.
Waffle slabs are preferred for spans greater than 40 feet (12 m), because, for a given mass of concrete, they are much stronger than flat slabs, flat slabs with drop panels, two-way slabs, one-way slabs, and one-way joist slabs. [2] Section of a waffle slab including beam, ribs, and column head
Single span rigid-frame bridges are typically made of reinforced concrete and are commonly used on parkways and other roadways. [4] This design is an efficient use of material as the cross section at mid-span is relatively narrow and the amount of concrete needed at the abutments is reduced. [4]
The Precast/Prestressed Concrete Institute (PCI) published the double tee load capacity calculation (load tables) for the first time in the PCI Design Handbook in 1971. The load tables use the code to identify double tee span type by using the width in feet, followed by "DT", followed by depth in inches, for example, 4DT14 is for 4-foot (1.2 m ...
A grid deck uses beams and diaphragms as the supporting structure. The supporting system of a grid deck is analyzed using a grillage analysis. A slab deck is one where the deck is analyzed as a plate. If the slab has a stiffness that is different in two directions (at right angles), then the deck is known and analyzed as an orthotropic deck.
In this case, the height of the structure, measured between the top of the deck and the ground, is between the values a/3 and a/2, where a denotes the span of the arch, which is generally a semicircular or elliptical arch. [7] The thickness e of the pier depends solely on the span of the arches: a/10 < e < a/8.
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 ...
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.