土木工程专业英语.docx

UNIT 1Civil engineering projects are almost always unique；each has its own problems and design features.Therefore, careful study is given to each project even before design work begins.The study includes a survey both of topography and subsoil features of the proposed site.It also includes a consideration of possible alternatives, such as a concrete gravity dam or an earth-fill embankment dam.The economic factors involved in each of the possible alternatives must also be weighed.Today a study usually includes a consideration of the environmental impact of the project.Many engineers, usually working as a team that includes surveyors, specialists in soil machines ，and experts in design and construction, are involved in making this feasibility studies.Many civil engineers,among them that are people in the field, work in design. As we have seen,civil engineers work on many different kinds of structures, so it is normal practice for an engineer to specialize in just one kind.In designing buildings ,engineers often work as consultants to architectural or construction firms.Dams, bridges, water supply systems, and other large projects ordinarily employs several engineers whose work is coordinated by a system engineer who is in charge of the powerhouse and its equipment.In other cases, civil engineers are assigned to work on a project in another field;In the space program, for instance, civil engineers were necessary in the design and construction of such structures as lunching pads and rocket storage facilities.UNIT 10Concrete is a stone-like material obtained by permitting acarefully proportioned mixture of cement,Sand and gravel or other aggregate,and water to harden forms of the shape and dimensions of the desired structure.The bulk of the material consists of fine and coarse aggregate.Cement and water interact chemically to bind the aggregate particles into a solid mass.Additional water, over and above that needed for this chemical reaction, is necessary to give the mixture their work ability that enables it to fill the forms prior to hardening.Concretes in a wide range of strength properties can be obtained by appropriate adjustment of the proportions of the constituent materials.Special cements (Iris with such as high-early-strength cements),Special aggregates (Such as various lightweight or heavyweight aggregates.) and special curing methods (Such as Steam-curing)Permit an even wider variety of properties to be obtained.These properties depend to a very substantial degree on the proportions of the mix, on the thoroughness with which the various constituents are intermixed ,and on the conditions of humidity and temperature in which the mix is maintained from the moment it is placed in the form until it is fully hardened.The process of controlling these conditions is known as curing.To protect against the unintentional production of sub standard concrete, a high degree of skillful control and supervision is necessary throughout the process, from the proportioning by weight of the individual components, through mixing and placing utill the completion of curing.UNIT 11 To offset the limitation of plain concrete, it has been found passible,In the second half of the nineteenth century,To use steel with high tensile strength to reinforce concrete,chiefly in those places where its small tensile strength would limit the carrying of the member. The reinforcement usually round still rods with appropriate surface deformations to provide interlocking is placed in the forms in advance of the concrete.When completely surrounded by the hardened concrete mass, it forms an integral part of member.The resulting combination of two materials, known as reinforced concrete combines many of the advantages of each:The relatively low cost, good weather and fire resistance,good compressive strength,And excellent formability of concrete and the high tensile strength and much greater ductility and toughness of steel.It is this combination which allows the almost unlimited range of uses and possibilities of reinforced concrete in the construction of buildings,bridges.dams.tanks.reservoirs,and a host of other structure.Because if the cracks are kept very small and are bridged by tension still they have no adverse effect, on the safety or durability of the structure.The safety of reinforced concrete structures depends on the width of the cracks being kept below a permissible minimum and this has become a more serious problem in recent years because the use of higher steel stresses also increases the strain of the concrete.Cracks would not only be unsightly but would expose the Steel bars to corrosion by moisture and other chemical action,.thus crack control is a more serious matter in reinforced concrete design as compared with, say, twenty years ago.UNIT 12Besides its ability to sustain loads,concrete is also required to be durable, the durability of concrete can be defined as its resistance to deterioration resulting from external and internal causes, the external causes include the effects of environmental and service conditions to which concrete is subjected, such as weathering, chemical actions and wear.The internal causes are the effects of salts, particularly chlorides and sulphates, in the constituent materials, interaction between the constituent materials such alkali-aggregate reaction, volume changes, absorption and permeability.Principal factors responsible for volume changes are the chemical combination of water and cement and the subsequent drying of concrete,Variations in temperature and alternate wetting and drying.When a change in volume is resisted by internal or external forces, this can produce cracking,The greater the imposed restraint, the more severe the cracking.The presence of cracks in concrete reduces its resistance to the action of leaching,corrosion of reinforcement,attack by sulphates, and other chemicals, alkali-aggregate reaction and freezing and thawing, all of which may lead to disruption of concrete.Severe cracking can lead to complete disintegration of the concrete surface particularly when this is accompanied by alternate expansion and contraction.UNIT 13Conveying of most building concrete from the mixer or truck to the form is done in bottom-dump, buckets or in wheelbarrows or buggies or by pumping in through steel pipelines.The chief danger during conveying is that of segregation.The individual components of concrete tend to segregate because of their dissimilarity.In overly wets concrete standing in containers or forms, the heavier gravel components turn to settle, and the lighter materials, particularly water, tend to rise.Lateral movement, such as flow within the forms, tends to separate the coarse gravel from the finer components of the mix.The danger of segregation has caused the discarding of some previously common means of conveying, such as chutes and conveyor belts, in favor of methods which minimize this tendency.Fresh concrete gains strength most rapidly during the first few days and weeks.Structural design is generally based on the 28 day strength, about 70 percent of which is reached at the end of the first week after placing.The final concrete strength depends greatly on the conditions of the moisture and temperature during this initial period.The maintenance of proper conditions during this time is known as curing.Thirty percent of the strength or more can be lost by premature drying out of the concrete; similar accounts may be lost by permitting the concrete temperature to drop to 40F or lower during the first few days unless the concrete is maintained continuously moist for a long time thereafter.Freezing of fresh concrete may reduce its strength by as much as 50 percent.UNIT 16A second important property of the building material is its stiffness.This property is defined by the elastic modulus，which is the ratio of the stress (force per unit area),to the strain (deformation per unit length).The elastic modulus, therefore, is a measure of the resistance of a material to the deformation under load.For two materials of equal area under the same load, the one with the higher elastic modulus has the smaller deformation.Structural steel, which has an elastic modulus of thirty million pounds per square inch(psi),Or 2,100,000 kilograms per square centimeter,is 3 times as stiff as aluminum, 10times as stiff as concrete,and 15times as stiff as wood.MasonryMasonry consists of nature materials,such as stone or manufactured products, such as brick and concrete blocks.Masonry has been used since ancient times;mud bricks were used in the city of Babylon, for secular buildings, and stone was used for the great temples of the Nile Valley.The great Pyramid in Egypt,standing 481 feet (147 meters) high,is the most spectacular masonry construction.Masonry units originally were stacked without using any bonding agent, but all modern masonry construction uses a cement mortar, as a bonding material.Modern structural materials include stone, brick of burnt clay or slate,and concrete blocks.Masonry is essentially a compressive material: it cannot withstand a tensile force, that is, a pull.The ultimate compressive strength of bonded masonry depends on the strength of the masonry unit and the mortar.The ultimate strength will vary from 1,000 to 4,000 psi (70 to 280 kg/cm),Depending on the particular combination of masonry unit and mortar used.UNIT 22In an entire contract,where the employer agrees to pay a certain sum in return for civil engineering work, which is to b