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27.08.2020 06:11

Английский язык

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Краткое изложение текста "The Design of Concrete Pavement" с элементами аннотирования и реферирования
The design of Concrete Pavement
The performance of a concrete pavement for traffic riding purposes depends not only upon the property of materials but also on the underlying sub-grade or the base course. The design of a concrete pavement must involve all physical properties of concrete. Concrete withstands high compression but it is low in tension (flexure). Like wood, it expands on wetting and shrinks while drying. With temperature, like other materials, it decreases or increases in length. Under some conditions its volume increases with age. A concrete pavement when subjected to variations of daily temperature and moisture between the top and the bottom of the slab will have a tendency to warp and curl.
The following conclusions have been generally established after a series of theoretical approaches and practical results in concrete pavement design:
1.Cracking due to flexure is almost inevitable in a concrete slab of any great length.
2.For constant loads on slabs of reasonable length, load and total stress decrease as slab thickness increases, that is to say, if the safe working stress were to remain the same, the slab thickness must increase as wheel loads increase.
Reinforcement. The provision of reinforcement in a concrete pavement is designed to hold cracks that develop due to flexural stresses as close as possible, so that they may not develop into a major defect. It must be remembered that reinforcement is not used either to increase the load bearing capacity or for complete prevention of cracking. Reinforcement may be used: 1. To prevent fracture surface from widening and to tie all parts of the slab together. 2. Where there is a possibility for the sub-grade to become weak and non-uniform in bearing, so that the induced cracks may not get widened and exposed to action of dirt and water. If additional load bearing capacity is required this can be easily achieved by thickening the pavement.