ly together. In this type of structure, therefore, the floors and the roof serve the added purpose of forming part .of the framework. When roof and floors are all finally in place and connected to the columns, the protective walls can be built up from ground level.
In large buildings, the civil engineer's main task is the design of frameworks and foundations.
Left, model by Mies van der Rohe for a glass skyscraper, 1920. Right, Tokyo hotel designed by Frank Lloyd Wright; it rents on a concrete raft (diagram).
Where a building is supported by its walls, the weight is spread out over a large area. This gives relatively low pressures on the ground and makes foundation work easy. But in a modern building framework, the load is carried by a small number of columns, which leads to highly concentrated ground pressure. Hence the foundations must be strong, particularly if the ground is weak.
If the ground is reasonably firm, it is often enough to place the columns on spread footings. These are blocks of concrete of such area as to spread the load to within the carrying strength of the ground. On soft ground, a building is sometimes put on a concrete raft, which is a footing covering the whole ground plan area. A building on its raft is virtually floating on the ground beneath. A method often used is to drive a number of piles under each column foundation. The piles are made long enough to rest on the hard ground below the soft surface. The building is then literally on stilts. Another method is to carry the columns on fairly large diameter cylinders sunk deeply into the ground.
Below, the Empire State Building lowers above :he skyscrapers of New York.
II. Answer the following questions.
1) What factors have led to the revolution in the "history of modern structures"?
2) Why is the «framework principle» used widely in modern constructions?
3) How does the "lift- slab" method work?
4) Why is it necessary for civil engineers to pay special attention to the design of frameworks and foundations?
5) What types of foundations are mentioned in the text?
III. Describe the types of foundation works given in the text. Determine what conditions must be considered to choose the right type of foundation works.
IV. Are these statements true or false?
Correct the wrong statements.
1. The outside walls of new buildings are "bearing walls".
2. The weight of the outside walls is taken by the foundations.
3. "The lift -slab" method consists in the construction of the frame and floors on the top level.
4. The structure of the ground under the construction should be thoroughly examined.
5. It is enough to place the columns on spread footings if the ground is firm.
V. Complete the sentences using an appropriate link.
1. Engineers have been able to achieve new results
2. The walls of the buildings were bearing walls
3. We can build to greater heights, span wider gaps
4. In a mass construction the building is supported by its walls
5. In a modern building the foundations must be strong
a) The rise of the science of structure and the advent of steel and concrete have enabled them to build their structures as frameworks.
b) The weight is spread out over a large area.
c) The load is carried bya small number of columns.
d) Advanced techniques in building and progressive building materials
e) They carried the dead weight and the live load of the structure
VI. Match the word from column A to its synonym in column B.
1. to substitute a) to place
2. to carry the load b) to replace
3. to invent c) to support
4. to settle d) to devise
5. to uphold e) to bear
Fill in the gaps with the words from column A.
1. New materials _______ the old ones and with these materials we can build to greater heights
and ______ the greater_______.
2. When the lift-slab method was first _______, some people described it as a way of constructing a building from the top downward.
3. The protective walls can be built up from ground level, when roof and floors, are finally
4. As a mass construction is _____________by its walls, the weight is spread out over a large
VII. Translate into En