a) a mass construction
b) a frame construction
c) a planar construction
Building materials are used in two basic ways. In the first way they are used to support the loads on a building and in the second way they are used to divide the space in a building. Building components are made from building materials and the form of a component is related to the way in which it is used. We can see how this works by considering three different types f construction:
1. In one kind of construction, blocks of materials such as brick, stone, or concrete are put together to form solid walls. These materials are heavy, however, they can support the structural loads because they have the property of high compressive strength. Walls made up of blocks both support the building and divide the space in the building.
Planar construction
Mass construction
2. In another type of construction, sheet materials are used to form walls which act as both space-dividers and structural support. Timber, concrete and some plastics can be made into large rigid sheets and fixed together to form a building. These buildings are lighter and faster to construct than buildings made up of blocks.
3. Rod materials, on the other hand, can be used for structural support but not for dividing spaces. Timber, steel and concrete can be formed into rods and used as columns. Rod materials with high tensile and compressive strength can be fixed together to form framed structures. The spaces between the rods can be filled with light sheet materials which act as space dividers but do not support structural loads.
XIV. Say whether these statements are true or false. Correct the false statements.
1. Rod materials can be used for both dividing space and supporting the building.
2. Concrete is used as a block material, a sheet material and a rod material.
3. Steel is used for frame constructions because it has a property of high tensile strength and low compressive strength.
4. The sheet materials, which act as space dividers in a frame building are light because they do not support structural loads.
5. Mass construction buildings are light whereas planar constructions are heavy.
Unit 7
Irrigation dams
I. Memorize the following words and expressions:
a feeder canal -
a main drainage channel -
receiving basin -
an outlet - ,
drainage network -
to surge -
surplus -
II. Read the text
Irrigation dams
Irrigation dams are designed to store water. The next step in irrigation is to construct a system of canals and channels feeding the land from a natural or man-made source: a river, or a reservoir. When the feeder canals reach the area to be irrigated, they branch out into many smaller channels, which are spread out systematically, and share out the water over the dry land. As the irrigation network gives up more and more of its water, the channels get smaller and smaller.
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When the engineer wants to drain land of an excess of water, his aim is just the opposite of irrigation. He digs many small channels, or drains, which collect the excess water from particular areas of the marsh-and carry it to the main drainage channel, just as the tributaries of a river flow into the main river. As the drainage network collects more and more water, the main collecting drain gets larger.
There are important differences between the two kinds of network, for irrigation is adjusted to needs, whereas drainage, depending mainly on rainfall, is not subject to man's will. The bed of an irrigation channel is kept as high as possible so that water can flow onto the land the bed of a drainage channel is kept as low as possible so that excess water flows off the land.
The main drainage canal, carrying all the water it has collected from its tributary channels, empties into a receiving basin, which may be a river, lake, or sea. If the water in this basin is subject to floods or high tides, the engineer must build a check structure at or near the outlet to prevent the floodwater from surging back into the drainage channels. The structure contains gates -or sluices that may be closed to prevent back-flow, or opened to allow the drainage canal to empty into the receiving basin.
