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A variety of devices, usually electronically controlled, have been developed to produce both wave and tidal effects.
The value of these experiments derives from the reduction in the time scale, which has been found to correspond to the reduction in the dimensional scales of the model.
Once regarded as scientific toys, such studies are now considered an essential preliminary step to any large-scale redevelopment of a port or coastal area and are useful even for minor modifications or additions.
Scale models of the area, harbour, or estuary are made so that water can be caused to flow in such a way as to reproduce the various tidal and other streams in the same direction and with velocities equivalent to those occurring on the site.
In many places, without continuous attention to such maintenance, the coincidence of high tides with heavy rainfall would lead to frequent disastrous flooding of inhabited areas.
Of many of the ancient port structures, no physical trace remains, but knowledge of the fact that they existed and even a measure of technical description has come down through the written word.
There is no conclusive evidence for the date or locality of the first artificial harbour construction, but it is known that the Phoenicians built harbours at Sidon and Tyre in the 13th century BC.
The engineers of those days either knew or thought little about conservancy even as applied to the ports they constructed.
An operation of maintaining a river estuary at a depth sufficient for navigation, for example, may at the same time greatly improve its capacity for the drainage of upland floodwaters.
The planning of maritime civil engineering works, whether for transportation, reclamation, or conservancy, has been facilitated by the development of the technique of model studies.