Elements of a Building

The major elements of a building include the following: (1) the foundation, which supports the building and provides stability; (2) the structure, which supports all the imposed loads and transmits them to the foundation; (3) the exterior walls, which may or may not be part of the primary supporting structure; (4) the interior partitions, which also may or may not be part of the primary structure; (5) the environmental-control systems, including the heating, ventilating, air-conditioning, lighting, and acoustical systems; (6) the vertical transportation systems, including elevators, escalators, and stairways; (7) communications, which may include such subsystems as intercommunications, public address, and closed-circuit television, as well as the more usual telephone-wiring systems; and (8) the power, water supply, and waste disposal systems.

Building Loads

The loads imposed on a building are classified as either “dead” or “live.” Dead loads include the weight of the building itself and all major items of fixed equipment. Dead loads always act directly downward, act constantly, and are additive from the top of the building down. Live loads include wind pressure, seismic forces, vibrations caused by machinery, movable furniture, stored goods and equipment, occupants, and forces caused by temperature changes. Live loads are temporary and can produce pulsing, vibratory, or impact stresses. In general, the design of a building must accommodate all possible dead and live loads to prevent the building from settling or collapsing and to prevent any permanent distortion, excessive motion, discomfort to occupants, or rupture at any point.

Text c Foundations

The structural design of a building depends greatly on the nature of the soil and underlying geologic conditions and modification by man of either of these factors

Ground Conditions

If a building is to be constructed in an area that has a history of earthquake activity, the earth must be investigated to a considerable depth. Faults in the crust of the earth beneath the soil must obviously be avoided. Some soils may liquefy when subjected to the shock waves of a quake and become like quicksand. In such cases, either construction must be avoided altogether or the foundation must be made deep enough to reach solid material below the potentially unstable soil. Certain clay soils have been found to expand 23 cm or more if subjected to long cycles of drying or wetting, thus producing powerful forces that can shear foundations and lift lightweight buildings. Some soils with high organic content may, over time, compress under the building load to a fraction of their original volume, causing the structure to settle. Other soils tend to slide under loads.

Soils that have been modified in some way often perform differently, especially when other soil has been added to or mixed with existing soil, or when the soil has been made wetter or drier than normal, or when cement or chemicals such as lime have been added. Sometimes the soil under a proposed building varies so greatly over the entire site that a building simply cannot be constructed safely or economically Soil and geologic analyses are necessary, therefore, to determine whether a proposed building can be supported adequately and what would be the most effective and economical method of support.

If there is sound bedrock a short distance below the surface of the construction site, the area over which the building loads are distributed can be quite small because of the strength of the rock. As progressively weaker rock and soils are encountered, however, the area over which the loads are distributed must be increased.

Types of Foundations

The most common types of foundation systems are classified as shallow and deep. Shallow foundation systems are several feet below the bottom of the building; examples are spread footings and mats. Deep foundations extend several dozen feet below the building; examples are piles and caissons. The foundation chosen for any particular building depends on the strength of the rock or soil, magnitude of structural loads, and depth of groundwater level.

The most economical foundation is the reinforced-concrete spread footing, which is used for buildings in areas where the subsurface conditions present no unusual difficulties. The foundation consists of concrete slabs located under each structural column and a continuous slab under load-bearing walls.

Mat foundations are typically used when the building loads are so extensive and the soil so weak that individual footings would cover more than half the building area. A mat is a flat concrete slab, heavily reinforced with steel, which carries the downward loads of the individual columns or walls. The mat load per unit area that is transmitted to the underlying soil is small in magnitude and is distributed over the entire area. For large mats supporting heavy buildings, the loads are distributed more evenly by using supplementary foundations and cross walls, which stiffen the mat.

Piles are used primarily in areas where near-surface soil conditions are poor. They are made of timber, concrete, or steel and are located in clusters. The piles are driven down to strong soil or rock at a predetermined depth, and each cluster is then covered by a cap of reinforced concrete. A pile may support its load either at the lower end or by skin friction along its entire length. The number of piles in each cluster is determined by the structural load and the average load-carrying capacity of each pile in the cluster. A timber pile is simply the trunk of a tree stripped of its branches and is thus limited in height. A concrete pile, on the other hand, may be of any reasonable length and may extend below groundwater level as well. For extremely heavy or tall buildings, steel piles, known as H-piles because of their shape, are used. H-piles are driven through to bedrock, often as far as 30 m below the surface. H-piles can be driven to great depths more easily than piles made of wood or concrete; although they are more expensive, the cost is usually justified for large buildings, which represent a substantial financial investment. Caisson foundations are used when soil of adequate bearing strength is found below surface layers of weak materials such as fill or peat. A caisson foundation consists of concrete columns constructed in cylindrical shafts excavated under the proposed structural column locations. The caisson foundations carry the building loads at their lower ends, which are often bell-shaped.

Words and expressions

structural design - строительный проект

pile foundation - свайное основание

bearing strength - несущая способность

Exercise 1

Ответьте на следующие вопросы:

1. What does the structural design of a building depend greatly on?

2. What should be done by a construction company, if a building is constructed in an area that has a history of earthquake activity?

3. In what case the construction company has to investigate the earth to a considerable depth?

4. In what cases construction must be avoided altogether or the foundation must be made deep enough?

5. What kinds of soils expand 23 cm or more if subjected to long cycles of drying or wetting?

6. What kinds of soils compress under the building load to a fraction of their original volume?

7. What kind of soil causes the structure to settle?

8. What soils in some way often perform differently?

9. What is usually done by a construction company if the soil under a proposed building varies so greatly over the entire site?

10. What are the main goals of soil and geologic analyses before construction of a building?

11. What are the most common types of foundation systems?

12. What is the most economical type of a foundation?

13. In what cases mat foundations are typically used?

14. What types of foundations are used primarily in areas where near-surface soil conditions are poor?

15. What types of piles are used for extremely heavy or tall buildings?

Exercise 2

Заполните пропуски недостающими по смыслу словами, используя текст:

1. The structural … of a building depends greatly on the nature of the soil.

2. The earth must be investigated to a considerable depth if a building is constructed in an area that has a history of … activity.

3. Soils with high organic content may, over time, … under the building load to a fraction of their original volume.

4. If the soil under a proposed building varies so greatly over the entire site a building simply cannot be constructed … .

5. Soil and geologic … are necessary to determine whether a proposed building can be supported adequately.

6. The foundation chosen for any particular building depends on the … of the rock or soil.

7. The most economical foundation is the … spread footing.

8. Piles are used in areas where near-surface soil conditions are … .

9. Piles are made of … , …, or … .

10. H-piles can be driven to great depths more easily than piles made of … .

Exercise 3

Соответствуют ли данные предложения содержанию текста:

1. The structural design of a building depends greatly on underlying geologic conditions.

2. If a building is to be constructed in rural area, the earth must be investigated to a considerable depth.

3. Certain clay soils have been found to expand 23 cm or more if subjected to long cycles of cooling, thus producing powerful forces that can lift heavyweight buildings.

4. Some soils with high content of iron may, over time, compress under the building load to a fraction of their original volume.

5. Soil and geologic analyses are necessary to find out is building economical in construction.

6. If rock and soils are more weaker, the area over which the loads are distributed must be decreased.

7. The most common types of foundation systems are classified as expensive and cheap.

8. Shallow foundation systems are several meters below the bottom of the building.

9. The foundation chosen for any building depends only on depth of groundwater level.

10. Piles are used primarily in areas where near-surface soil conditions are very good

11. Piles are made of stainless steel, plastics and bricks.

Exercise 4

Используя текст, составьте высказывания с данными словами и выражениями:

Structural design - geologic conditions - earthquake activity - shock waves - solid material - unstable soil - to shear foundation - organic content - to construct safely and economically - soil and geologic analyses - to be supported adequately - effective and economical method of support - building loads - shallow and deep - strength of the rock - magnitude of structural loads - depth of groundwater level - the downward load - predetermined depth - substantial financial investment.

Exercise 5

Кратко передайте содержание каждого абзаца.

Exercise 6

Выделите пять основных идей текста.

Exercise 7

Составьте предложения, используя данные выражения:

• bearing pile (несущая свая); built pile (составная свая); cast-in-place concrete pile (набивная бетонная свая); filling pile (набивная свая); friction pile (висячая свая); precast concrete pile (готовая железобетонная свая); reinforced concrete pile (железобетонная свая); sectional steel pile (набивная свая со стальной обоймой); steel pile (стальная свая).

• isolated foundation (отдельный фундамент); permanent foundation (постоянный фундамент); pile foundation (свайной основание); ring foundation (кольцевой фундамент); shallow foundation (мелкозаложенный фундамент); stone foundation (каменное основание, фундамент); sunk foundation (погруженный фундамент; кессон); well foundation (фундамент из опускных колодцев).

Exercise 8

Переведите на русский язык следующие предложения:

1. The foundations in these buildings support considerably heavier loads than those of residential buildings.

2. Floor loadings range from 450 to 1,500 kilograms per square meter.

3. Spread footings are of two types, bearing and friction.

4. Solid bearing piles were originally made of timber.

5. The pile length may be a maximum of about 60 meters but is usually much less.

6. The piles are put in place by driving them into the ground with large mechanical hammers.

7. The building load is supported by the surface friction between the pile and the soil.

8. When the soil is so soft that even friction piles will not support the building load, the final option is the use of a floating foundation.

9. Floating foundations consist of flat reinforced concrete slabs or mats.

Exercise 9

Переведите на английский язык:

1. Тип фундамента здания зависит в большой степени от природы почвы и основных геологических условий.

2. При строительстве здания в сейсмически опасной местности земля должна быть обследована достаточно глубоко.

3. Состояние грунта и почвы зависит от конкретной местности строительства.

4. Строительство метро на этом участке было приостановлено из-за недостаточной исследованности почвы.

5. Фундаменты высоких здания должны быть сделаны на значительной глубине.

6. Существуют почвы, имеющие тенденцию скользить под весом зданий.

7. Самой простой классификацией фундаментов является их классификация по глубине.

8. Тип фундамента зависит от типа здания, почвы, веса строительных грузов и уровня грунтовых вод.

9. В сейсмически опасной местности фундамент здания располагается на большой глубине.

10. Сваи используются в местностях, с плохим поверхностным состоянием почвы.

11. Сваи забиваются в твердую почву или каменистый грунт на определенную глубину.

12. Стальные сваи, известные как H-сваи, используются при строительстве тяжелых или высоких зданий

13. H-сваи можно забивать на большие глубины значительно легче чем сваи изготовленные из древесины и бетона.

14. Любой фундамент несет нагрузку на здание сверху вниз.

Exercise 10

Текст на самостоятельный перевод:

Groundwater Level

Foundation construction is complicated by groundwater flowing above the bottom of the proposed foundation level. In such cases the sides of the excavation may be undermined and cave in. Lowering the groundwater level by pumping the water out of the excavation usually requires the installation of braced sheathing to shore up, or retain, the sides of the excavation to prevent any cave-ins. When the amount of water within the excavation is excessive, ordinary pumping methods, which bring to the surface loose soil mixed with the water, can undermine the foundations of buildings on adjoining property. To prevent damage caused by soil movement, wellpoint dewatering is often used. Wellpoints are small pipes with a perforated screen at one end. They are driven or jetted into the ground so that the screen, which prevents soil from flowing in with the water, is below groundwater level. These pipes are linked to a common manifold (pipe) that is connected to a water pump. In this way the groundwater is removed from below the excavation without damaging nearby property. Dewatering may also make it unnecessary to sheathe the sides of the excavation, providing the soil will not slide into the excavation because of its composition or because of vibrations from nearby heavy traffic or machinery.