TEXT 6

1. Answer the following question and read the text below to check your answer.

What do you know about the inner structure of metals? How many valences do metals usually have?

The chemical definition of a metal is an element with one, two, or three valence electrons. These elements bond into a mass with metallic bonds. Due to the nature of metallic bonds, metals have a very regular and well-defined structure. Since the metallic bonds are nondirectional, the atoms are free to pack into a dense configuration. The regular three-dimensional geometric pattern of the atoms in a metal is called a unit cell. Repeated coalescing of unit cells forms a space lattice of the material. However, in a mass of material, a perfect structure can be achieved only through carefully controlled conditions. Generally, metallic solids are formed by cooling a mass of molten material. As the material cools, the atoms are vibrating. This can cause one atom to occupy the space of two atoms, generating a defect in the lattice structure. In addition, during the cooling process crystals grow simultaneously from several nuclei. As the material continues to cool, these crystals grow together with a boundary forming between the grains. This produces flaws or slips planes in the structure that have an important influence on the behavior and characteristics of the material. In addition, rarely are pure elemental metals used for engineering applications. Even highly refined materials contain impurities that were not removed in the refining process. In addition, most metals do not have desirable properties in a pure state. For example, iron and aluminum used for structural applications have alloying elements that impart special characteristics to the metal. As a result, understanding the nature of metals at the molecular level requires an examination of the primary structure of the metal, the effect of cooling rates, and the impact of impurities and alloying elements.

Vocabulary:

Metallic bond — металлическая связь.

Three-dimensional geometric pattern — трехмерный геометрический узор.

Repeated coalescing — повторяющееся слияние. A space lattice — пространственная решетка. Slips planes — скользящие плоскости. Elemental metal — элементарный металл. Impurity — загрязненность.

To impart — придавать.

Cooling rate — скорость охлаждения.

2. Decide whether the following statements are true or false according to the text.

1. The chemical definition of a metal is an element with five, six, or seven valence electrons. 2. The regular three-dimensional geometric pattern of the atoms in a metal is called a unit cage. 3. A perfect structure of a metal can be achieved only through carefully controlled conditions.

4. A boundary forming between the grains when the metal is cooling produces flaws or slips planes in the structure that have an important influence on the behavior and characteristics of the material.

5. Static loads are abruptly applied such that shock and vibration is generated in the structure and are very similar to the impact stress.

3. Answer the following questions and give examples.

1.How can a metal be defined from chemical point of view?

2.Why the metal atoms can form a dense configuration?

3.How can a perfect structure of metal be achieved?

4.How not following all necessary rules of production may cause flaws to appear in the metal structure?

5.What has to be examined in order to get an alloy of quality?

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TEXT 7

1. Answer the following question and read the text below to check your answer.

What are the reasons that may make buildings collapse? How to prevent these failures from happening?

Mechanical Property

The mechanical behavior of materials is the response of the material to external loads. All materials deform in response to loads; however, the specific response of a material depends on its properties, the magnitude and type of load, and the geometry of the element. Whether the material “fails” under the load conditions depends on the failure criterion. Catastrophic failure of a structural member, resulting in the collapse of the structure, is an obvious material failure. However, in some cases the failure is more subtle, but with equally severe consequences. For example, pavement may fail due to excessive roughness at the surface, even though the stress levels are well within the capabilities of the material. A building may have to be closed due to excessive vibrations by wind or other live loads, although it could be structurally sound.

One of the considerations in the design of a project is the type of loading the structure will be subjected to during its design life. The two basic types of loads are static and dynamic. Each type affects the material differently, and frequently the interactions between the load types are important. Civil engineers encounter both when designing a structure.

Static loading implies a sustained loading of the structure over a period of time. Generally, static loads are slowly applied such that no shock or vibration is generated in the structure. Once applied, the static load may remain in place or be removed slowly. Loads that remain in place for an extended period of time are called sustained (dead) loads.

In civil engineering, much of the load the materials must carry is due to the weight of the structure and equipment in the structure. Loads that generate a shock or vibration in the structure are dynamic loads. Dynamic loads can be classified as periodic, random, or transient.

A periodic load, such as a harmonic or sinusoidal load, repeats itself with time. For example, rotating equipment in a building can produce a vibratory load. In a random load, the load pattern never repeats, such as that produced by earthquakes. Transient load, on the other hand, is an impulse load that is applied over a short time interval, after which the vibrations decay until the system returns to a rest condition. For example, bridges must be designed to withstand the transient loads of trucks.

Vocabulary:

Property — cвойства.

Excessive roughness — чрезмерная шероховатость.

To encounter — сталкиваться.

Static loading — статическая нагрузка. Dynamic loads — динамические нагрузки. Periodic load — периодическая нагрузка. Transient load — переходная нагрузка.

2.Decide whether the following statements are true or false according to the text.

1.The electrical behavior of materials is the response of the material to external loads.

2.The failure of the material under the load conditions depends on the failure criterion.

3.Pavement can’t fail due to excessive roughness at the surface, even though the stress levels are well within the capabilities of the material.

4.The type of loading the structure will be subjected to during its design life doesn’t matter at all.

5.Shock or vibration that appear in the structure are called dynamic loads.

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3.Answer the following questions and give examples.

1.What types of failures do you know?

2.What loads may cause a building to collapse?

3.How loads may be classified?

4.What is the difference between a static and a cyclic load?

5.Effects of what loads should bridges be supposed to avoid?

TEXT 8

1. Answer the following question and read the text below to check your answer.

Is wood a structural or decorative material?

Wood, because of its availability, relatively low cost, ease of use, and durability (if properly designed), continues to be an important civil engineering material. Wood is used extensively for buildings, bridges, utility poles, floors, roofs, trusses, and piles.

Civil engineering applications include both natural wood and engineered wood products, such as laminates, plywood, and strand board.

In order to use wood efficiently, it is important to understand its basic properties and limitations. In the United States, the Forest Service of the Department of Agriculture has broad management responsibility for the harvesting of wood from public lands and for assisting private sources with the selection of products for harvesting.

Wood is a natural, renewable product from trees. Biologically, a tree is a woody plant that attains a height of at least 6 m (20 ft), normally has a single self-supporting trunk with no branches for about 1.5 m (4 ft) above the ground, and has a definite crown. There are over 600 species of trees in the United States.

Trees are classified as either endogenous or exogenous, based on the type of growth. Endogenous trees, such as palm trees, grow with intertwined fibers. Wood from endogenous trees is not generally used for engineering applications in the United States. Exogenous trees grow from the center out by adding concentric layers of wood around the central core. This book considers only exogenous trees.

Exogenous trees are broadly classified as deciduous and conifers, producing hardwoods and softwoods, respectively. The terms hardwood and softwood are classifications within the tree family, not a description of the woods’ characteristics. In general, softwoods are softer, less dense, and easier to cut than hardwoods. However, exceptions exist such as balsa, a very soft and lightweight wood that is botanically a hardwood.

Deciduous trees generally shed their leaves at the end of each growing season. Commercial hardwood production in the U.S. comes from 40 different tree species.

Many hardwoods are used for furniture and decorative veneers, due to their pleasing grain pattern. The decorative properties of some hardwoods increase their value and cost. This makes them uneconomical for construction lumber. Again, there are some exceptions where some hardwoods are used engineered wood products that are used in construction applications.

Conifers, also known as evergreens, have needlelike leaves and normally do not shed them at the end of the growing season. Conifers grow continuously through the crown, producing a uniform stem and homogenous characteristics. Softwood production in the U.S. comes from about 20 individual species of conifers. Conifers are widely used for construction. Conifers grow in large stands, permitting economical harvesting. They mature rapidly, making them a renewable resource.

Vocabulary:

Endogenous — эндогенный. Exogenous — экзогенный. Deciduous trees — лиственный.

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Conifers — хвойные деревья.

Evergreens — вечнозеленые растения.

Hardwoods — лиственные породы.

Decorative veneers — декоративные шпоны.

Needlelike leaves — игольчатые листья.

2. Decide whether the following statements are true or false according to the text.

1.Wood possesses such properties as availability, relatively low cost and durability.

2.Civil engineering applications include both structural wood and decorative wood products, such as laminates, plywood, and strand board.

3.It’s the Forest Service of the Department of Agriculture which has broad management responsibility for the harvesting of wood from public lands.

4.Deciduous trees generally never shed their leaves at the end of each growing season so the leaves remain ever green.

5.Conifers have wide leaves and normally shed them at the end of the growing season.

3. Answer the following questions and give examples.

1.Is wood considered as a structural or decorative material?

2.Is wood an expensive material?

3.What types of wood do you know? What purposes are these types used for?

4.What happens to the deciduous trees leaves at the end of each season?

5.What is the difference between exogenous and endogenous trees?

TEXT 9

1. Answer the following question and read the text below to check your answer.

Are the aesthetic characteristics of a building project as important as its structural characteristics?

The aesthetic characteristics of a material refer to the appearance of the material. Generally, these characteristics are the responsibility of the architect. However, the civil engineer is responsible for working with the architect to ensure that the aesthetic characteristics of the facility are compatible with the structural requirements.

During the construction of many public projects, a certain percentage of the capital budget typically goes toward artistic input. The collaboration between the civil engineer and the architect is greatly encouraged, and the result can increase the value of the structure.

In many cases, the mix of artistic and technical design skills makes the project acceptable to the community. In fact, political views are often more difficult to deal with than technical design problems. Thus, engineers should understand that there are many factors beyond the technical needs that must be considered when selecting materials and designing public projects.

2. Decide whether the following statements are true or false according to the text.

1.The aesthetic characteristics of a material are as important as their engineering properties.

2.The civil engineer is responsible for working with the architect.

3.The collaboration between the civil engineer and the architect is never welcome, so everyone must work separately in order the result could increase the value of the structure.

4.The mix of artistic and humanitarian design skills makes the project acceptable to the community.

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