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A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Steel- reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving ( see below ).
For example, in designing a staircase, a dead load factor may be 1.2 times the weight of the structure, and a live load factor may be 1.6 times the maximum expected live load. These two "factored loads" are combined (added) to determine the "required strength" of the staircase.
Lift slab construction (also called the Youtz-Slick Method) is a method of constructing concrete buildings by casting the floor or roof slab on top of the previous slab and then raising (jacking) the slab up with hydraulic jacks. This method of construction allows for a large portion of the work to be completed at ground level, negating the ...
Concrete has a very low coefficient of thermal expansion, and as it matures concrete shrinks. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete which is subjected to long-duration forces is prone to creep. The density of concrete varies, but is around 2,400 kilograms per cubic metre (150 lb/cu ft). [1]
Segmented load plates adapt to the shape of the pavement to more evenly distribute the load on uneven surfaces. The load plate diameter is typically 300 mm diameter on roads and 450 mm on airports, and the load for road testing is about 40 kN, producing about 567 kPa pressure under the load plate (50 kN / 707 kPa according to European standard).
The test is carried out using a metal mould in the shape of a conical frustum known as a slump cone or Abrams cone, that is open at both ends and has attached handles.The tool typically has an internal diameter of 100 millimetres (3.9 in) at the top and of 200 millimetres (7.9 in) at the bottom with a height of 305 millimetres (12.0 in).The cone is placed on a hard non-absorbent surface.
For slabs using spherical voids, the shear resistance is approximately proportional to the volume of concrete, as the geometry of the voids causes efficient transfer of force to load-bearing parts, enabling all the concrete to be effective. Other shapes of voids, with flat or flattened surfaces, will result in more concrete and/or less strength.
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 ...