土木工程英语翻译纯英语

The history of civil engineeringAnother advance in steel construction is the method of fastening together the beams. For many years the standard method was riveting. A rivet is a bolt with a head that looks like a blunt screw without threads . It is heated, placed in holes through the pieces of steel , and a second head is formed at the other end by hammering it to hold it in place . Riveting has now largely been replaced by welding, the joining together of pieces of ste Fundamentally, engineering is an end-product-oriented discipline that is innovative, cost-conscious and mindful of human factors. It is concerned with the creation of new entities, devices or methods of solution: a new process, a new material, an improved power source, a more efficient arrangement of tasks to accomplish a desired goal or a new structure. Engineering is also more often than not concerned with obtaining economical solutions. And, finally, human safety is always a key consideration.Engineering is concerned with the use of abstract scientific ways of thinking and of defining real world problems. The use of idealizations and development of procedures for establishing bounds within which behavior can be ascertained are part of the process.Many problems, by their very nature, can’t be fully described—even after the fact, much less at the outset. Yet acceptable engineering solutions to these problems must be found which satisfy the defined needs. Engineering, then, frequently concerns the determination of possible solutions within a context of limited data. Intuition or judgment is a key factor in establishing possible alternative strategies, processes, or solutions. And this, too, is all a part of engineering.Civil engineering is one of the most diverse branches of engineering. The civil engineer plans, designs, constructs, and maintains a large variety of structures and facilities for public, commercial and industrial use. These structures include residential, office, and factorybuildings; highways, railways, airports, tunnels, bridges, harbors, channels, and pipelines. They also include many other facilities that are a part of the transportation systems of most countries, as well as sewage and waste disposal systems that add to our convenience and safeguard our health.The term “civil engineer”did not come into use until about 1750, when John Smeaton, the builder of famous Eddystone lighthouse near Plymouth, England, is said to have begun calling himself a “civil engineer”to distinguish himself from the military engineers of his time. However, the profession is as old as civilization.In ancient Egypt the simplest mechanical principles and devices were used to construct many temples and pyramids that are still standing, including the great pyramid at Giza and the temple of Amon-Ra at Karnak. The great pyramid, 481 feet(146.6 meters)high, is made of 2.25 million stone blocks having an average weight of more than 1.5tons (1.4 metric tons). Great numbers of men were used in the construction of such monuments. The Egyptians also made obelisks by cutting huge blocks of stone, some weighing as much as 1000 tons (900 metric tons). Cutting tools of hard bronze were used.The Egyptians built causeways and roads for transporting stone from the quarries to the Nile. The large blocks of stone that were erected by the Egyptians were moved by using levers, inclined planes, rollers, and sledges.The Egyptians were primarily interested in the know-how of construction; They had very little interest in why-for of use .In contrast, the Greeks made great strides in introducing theory into engineering problems during the 6th to 3rd centuries B.C. They developed an abstract knowledge of lines, angles, surfaces, and solids rather than referring to specific objects. The geometric base for Greek building construction included figures such as the square, rectangle, and triangle.The Greek architekton was usually the designer, as well as the builder,of architectural and engineering masterpieces. He was an architect and engineer. Craftsmen, masons, and sculptors worked under his supervision. In the classical period of Greece all important buildings were built of limestone or marble; the Parthenon, for example, was built of marble.The principal construction materialsThe principal construction materials of earlier times were wood and masonry-brick, stone, or tile, and similar materials. The courses or layers were bound together with mortar or bitumen, a tarlike substance, or some other binding agent. The Greeks and Romans sometimes used iron rods or clamps to strengthen their building. The columns of the Parthenon in Athens , for example, have holes drilled in them for iron bars that have now rusted away . The Romans also used a natural cement called pozzolana, made from volcanic ash, that became as hard as stone under water.Both steel and cement, the two most important construction materials of modern times, were introduced in the nineteenth century. Steel, basically an alloy of iron and a small amount of carbon, had been made up to that time by a laborious process that restricted it to such special uses as sword blades . After the invention of the Bessemer process in 1856, steel was available in large quantities at low prices. The enormous advantage of steel is its tensile strength; that is, it does not lose its strength when it is under a calculated degree of tension, a force which, as we have seen, tends to pull apart many materials. New alloys have further increased the strength of steel and eliminated some of its problems, such as fatigue, which is a tendency for it to weaken as a result of continual changes in stress .Modern cement, called Portland cement, was invented in 1824. It is a mixture of limestone and clay, which is heated and then ground into a powder . It is mixed at or near the construction site with sand, aggregate (small stones, crushed rock, or gravel), andwater to make concrete. Different proportions of the ingredients produce concrete with different strength and weight. Concrete is very versatile; it can be poured, pumped, or even sprayed into all kinds of shapes. And whereas steel has great tensile strength, concrete has great strength under compression. Thus, the two substances complement each other .They also complement each other in another way: they have almost the same rate of contraction and expansion. They therefore can work together in situations where both compression and tension are factors . Steel rods are embedded in concrete to make reinforced concrete in concrete beams or structures where tension will develop . Concrete and steel also form such a strong bond - the force that unites them - that the steel cannot slip with the concrete. Still another advantage is that steel does not rust in concrete. Acid corrodes steel, whereas concrete has an alkaline chemical reaction, the opposite of acid.The adoption of structural steel and reinforced concrete caused major changes in traditional construction practices . It was no longer necessary to use thick walls of stone or brick for multistory buildings, and it became much simpler to build fire-resistant floors . Both these changes served to reduce the cost of construction. It also became possible to erect buildings with greater heights and longer spans.Since the weight of modern structures is carried by the steel or concrete frame, the walls do not support the building. They have become curtain walls, which keep out the weather and let in light. In the earlier steel or concrete frame building, the curtain walls were generally made of masonry; they had the solid look of bearing walls . Today, however, curtain walls are often made of lightweight materials such as glass, aluminum, or plastic, in various combinations.el by melting a steel material between them under high heat.Prestressed concrete is an improved form of reinforcement . Steelrods are bent into the shapes to give them the necessary degree of tensile strength. They are then used to prestress concrete, usually by one of two different methods. The first is to leave channels in a concrete beam that correspond to the shapes of the steel rods. When the rods are run through the channels, they are then bonded to the concrete by filling the channels with grout, a thin mortar or binding agent. In the other (and more common) method, the prestressed steel rods are placed in the lower part of a form that corresponds to the shape of the finished structure , and the concrete ispoured around them. Prestressed concrete uses less steel and less concrete. Because it is so economical, it is a highly desirable material.Prestressed concrete has made it possible to develop buildings with unusual shapes, like some of the modern sports arenas, with large space unbroken by any obstructing supports . The uses for this relatively new structural method are constantly being developed .The current tendency is to develop lighter materials, aluminum, for example, weighs much less than steel but has many of the same properties. Aluminum beams have already been used for bridge construction and for the framework of a few buildings.Lightweight concretes, another example, are now rapidly developing throughout the world. They are used for their thermal insulation . The three types are illustrated below : (a) Concretes made with lightweight aggregates; (b) Aerated concretes (US gas concretes) foamed by whisking or by some chemical process during casting; (c) No-fines concretes.All three types are used for their insulating properties , mainly in housing, where they give high comfort in cold climates and a low cost of cooling in hot climates. In housing, the relative weakness of lightweight concrete walls is unimportant, but it matters in roof slabs, floor slabs and beams.In some locations, some lightweight aggregates cost little more thanthe best dense aggregates and a large number of floor slabs have therefore been built of lightweight aggregate concrete purely for its weight saving, with no thought of its insulation value.The lightweight aggregate reduces the floor dead load by about 20 per cent resulting in considerable savings in the floor steel in every floor and the roof, as well as in the column steel and (less) in the foundations. One London contractor prefers to use lightweight aggregate because it gives him the same weight reduction in the floor slab as the use of hollow tiles, with simpler organization and therefore higher speed and profit. The insulation value of the lightweight aggregate is only important in the roof insulation, which is greatly improved.Structural AnalysisA structure consists of a series of connected parts used to support loads. Notable examples include buildings, bridges, towers, tanks, and dams. The process of creating any of these structures requires planning, analysis, design, and construction. Structural analysis consists of a variety of mathematical procedures for determining such quantities as the member forces and various structural displacements as a structure responds to its loads. Estimating realistic loads for the structure considering its use and location is often a part of structural analysis. Only two assumptions are made regarding the materials used in the structures of this chapter. First, the material has a linear stress-strain relationship. Second, there is no difference in the material behavior when stressed in tension vis-à-vis compression. The frames and trusses studied are plane structural systems. It will be assumed that there is adequate bracing perpendicular to the plane so that no member will fail due to an elastic instability. The very important consideration regarding such instability will be left for the specific design course.All structures are assumed to undergo only small deformations as theyare loaded. As a consequence we assume no change in the position or direction of a force as a result of structural deflections. Finally, since linear elastic materials and small displacement are assumed, the principle of superposition will apply in all cases. Thus the displacements or internal forces that arise from two different forces systems applied one at a time（一次一个）may be added algebraically to determine the structure’s response when both system(s) are applied simultaneously.In the real sense an exact analysis of a structure can never be carried out since estimates always have to be made of the loadings and the strength of the materials composing the structure. Furthermore, points of application for the loadings must also be estimated. It is important, therefore, that the structural engineers develop the ability to model or idealize a structure so that he or she can perform a practical force analysis of the members.Structural members are joined together in various ways depending on the intent of the designer. The two types of joints most often specified are the pin connection and the fixed joint. A pin-connected joint allows some freedom for slight rotation, whereas the fixed joint allows no relative rotation between the connected members. In reality, however, all connections exhibit some stiffness toward joint rotations, owing to friction and material behavior. When selecting a particular model for each support or joint, the engineer must be aware of how the assumptions will affect the actual performance of the member and whether the assumptions are reasonable for the structural design. In reality, all structural supports actually exert distributed surface loads on their contacting members. The resultants of these load distributions are often idealized as the concentrated forces and moments, since the surface area over which the distributed load acts is considerably smaller than the total surface area of the connecting members. The ability to reduce an actual structureto an idealized form can only be gained by experience. In engineering practice, if it becomes doubtful as to how to model a structure or transferthe loads to the members, it is best to consider several idealized structures and loadings and then design the actual structure so that itcan resist the loadings in all the idealized models.Almost all truss systems are configured so that analysis using the method of joints must begin at one end and proceed joint by joint towardthe other end. If it is necessary to evaluate the forces carried by a member located some distance from the ends, the method of joints requires the calculation of the forces in many members before the desired one is reached. The method of sections provides a means for a direct calculation in these cases. After the support reactions have been calculated the truss is cut through so that one part of the truss is completely severed from the rest. When this is done, no more than three unknown members should be cut. If possiblethe cut should pass through the member or members whose internal forces are to be found. A free-body diagram of the part of the truss onone side of this section is drawn, and the internal forces are found through the equilibrium equations. Since the system of forces on the free-body diagram is a plane non-concurrent force system, three equilibrium equations may be written and solved for the three unknowns.Influence lines have important application for the design of structures that resist large live loads. An influence line represents the variation of either the reaction, shear, moment, or deflection at a specific point in a member as concentrated force moves over the member. Once this line is constructed, one can tell at a glance where a live load should be placed on the structure so that it creates the greatest influenceat the specified point. Furthermore, the magnitude of the associated reaction, shear, moment, or deflection at the point can then be calculated from the ordinates of the influence-line diagram. For these reasons（因此）, influence lines play an important part in the design of bridges, industrial crane rails, conveyors, and other structures where loads move across their span. Although the procedure for constructing an influence line is rather basic, one should clearly be aware of the difference between constructing an influence line and constructing a shear or moment diagram. Influence lines represent the effect of a moving load only at a specified point on a member, whereas shear and moment diagrams represent the effect of fixed loads at all points along the axis of the member.Deflections of structures can occur from various sources, such as loads, temperature, fabrication errors, or settlement. In design, deflections must be limited in order to prevent cracking of attached brittle materials such as concrete or plaster. Furthermore, a structure must not vibrate or deflect severely in order to“appear” safe for its occupants. More important, though, deflections at specified points in a structure must be computed if one is to analyze statically indeterminate structures. We often determine the elastic deflections of a structure using both geometrical and energy methods. Also, the methods of double integration are used. The geometrical methods include the moment-area theorems and the conjugate-beam method, and the energy methods to be considered are based on virtual work and Castigliano’s theorem. Each of these methods has particular advantages or disadvantages.Concrete and reinforced concrete are used as building materials in every country. In many, including the United States and Canada, reinforced concrete is a dominant structural material in engineered construction. The universal nature of reinforced concrete construction stems from the wide availability of reinforcing bars and the constituents of concrete, gravel,sand, and cement, the relatively simple skills required in concrete construction, and the economy of reinforced concrete compared to other form of construction. Concrete and reinforced concrete are usedin bridges, buildings of all sorts, underground structures, water tanks, television towers, offshore oil exploration and production structures, dams, and even in ships.value of Reinforced ConcreteConcrete is strong in compression but weak in tension. As a result, cracks develop whenever loads, or restrained shrinkage or temperature changes, give rise to tensile stresses in excess of the tensile strength of the concrete. In the plain concrete beam, the moments due to applied loads are resisted by an internal tension-compression couple involving tension in the concrete. Such a beam fails very suddenly and completely when the first crack forms. In a reinforced concrete beam, steel bars are embedded in the concrete in such a way that the tension forces needed for moment equilibrium after the concrete cracks can be developed in the bars. Economy Frequently, the foremost consideration is the overall cost of the structure. This is, of course, a function of the costs of the materials and the labor necessary to erect them. Frequently, however, the overall cost is affected as much or more by the overall construction time since the contractor and owner must allocate money to carry out the construction and will not receive a return on this investment until the building is ready for occupancy. As a result, financial savings due to rapid construction may more than offset increased material costs. Any measures designer can take to standardize the design and forming will generally pay off in reduced overall costs.The choice of whether a structure should be built of concrete, steel, masonry, or timber depends on the availability of materials and on a number of value decisions.Economy Frequently, the foremost consideration is the overall cost of the structure. This is, of course, a function of the costs of the materials and the labor necessary to erect them. Frequently, however, theoverall cost is affected as much or more by the overall construction time since the contractor and owner must allocate money to carry out the construction and will not receive a return on this investment until the building is ready for occupancy. As a result, financial savings due to rapid construction may more than offset increased material costs. Any measures designer can take to standardize the design and forming will generally pay off in reduced overall costs. In many cases the long-term economy of the structure may be more important than the first cost. Asa result, maintenance and durabilityare important considerations.Suitability of Material for Architectural and Structural Function A reinforced concrete system frequently allows the designer to combinethe architectural and structural functions. Concrete has the advantagethat it is placed in a plastic condition and is given the desired shape and texture by means of the forms and the finishing techniques. This allows such elements as flat plates or other types of slabs to serve asload-bearing elements while providing the finished floor and ceiling surface.Similarly, reinforced concrete walls can provide architecturally attractive surfaces in addition to having the ability to resist gravity, wind, or seismic loads. Finally, the choice of size or shape is governedby the designer and not by the availability of standard manufactured members.Fire Resistance The structure in a building must withstand the effects of a fire and remain standing while the building is evacuated andthe fire is extinguished. A concrete building inherently has a 1- to 3-hourfire rating without special fireproofing or other details. Structural steel or timber buildings must be fireproofed to attain similar fire ratings.Rigidity The occupants of a building may be disturbed if their building oscillates in the wind or the floors vibrate as people walk by.Due to the greater stiffness and mass of a concrete structure, vibrations are seldom a problem.Low Maintenance Concrete members inherently require less maintenance than do structural steel or timber members. This is particularly true if dense, air-entrained concrete has been used for surfaces exposed to the atmosphere, and if care has been taken in the design to provide adequate drainage off and away from the structure. Availability of Materials Sand, gravel, cement, and concrete mixing facilities are very widely available, and reinforcing steel can be transported to most job sites more easily than can structural steel. As a result, reinforced concrete is frequently used in remote areas. On the other hand, there are a number of factors that may cause one to select a material other than reinforced concrete. These include： Low Tensile Strength As stated earlier, the tensile strength of concrete is much lower than its compressive strength (about 1/10), and hence concrete is subject to cracking. In structural uses this is overcome by using reinforcement to carry tensile forces and limit crack widths to within acceptable values. Unless care is taken in design and construction, however, these cracks may be unsightly or may allow penetration of water. Relatively Low Strength Per Unit of Weight or Volume The compressive strength of concrete is roughly 5%to10% that of steel, while its unit density is roughly 30% that of steel. As a result, a concrete structure requires a larger volume and a greater weight of material than does a comparable steel structure. As a result, long-span structures are often built from steel.。