工程管理外文翻译(原文+译文)

Concrete Construction matterT. Pauly, M. J. N. PriestleyAbstractViewed in terms of accepted practices, concrete construction operations leave much to be desired with respect to the quality, serviceability, and safety of completed structures. The shortcomings of these operations became abundantly clear when a magnitude 7.6 earthquake struck northern Paki-stan on October 8, 2005, destroying thousands of buildings, damaging bridges, and killing an esti-mated 79,000 people. The unusually low quality of construction operations prevalent was a major cause of the immense devastation.Keywords: Concrete Placing Curing Construction TechnologyPlacing ConcreteIf concrete is placed in the surface, the sur-face should be filled with water sufficiently to prevent it from absorbing the concrete of its water. If fresh concrete is to be placed on or nearby to concrete that has solidified, the surface of the placed concrete should be cleaned absolutely, preferably with a high-pressure air or water jet or steel-wire brushes. The surface should be wet, but there should be no much water. A little quantity of cement grout should be brushed over the whole area, and then followed immediately with the application of a 1/2-in Layer of mortar. The fresh concrete should be placed on or against the mortar.In order to decrease the disintegration re-sulting from carriage after it is placed. The con-crete should be placed as nearly as probably in itsfinal point. It should be placed in layers to permit uniform compaction. The time interval between the placing of layers should be limited to assure perfect bond between the fresh and previously placed concrete.In placing concrete in deeper patters, a ves-sel should be used to limit the free fall to not over 3 or 4 ft, in order to prevent concrete disintegra-tion. The vessel is a pipe made of lightweight metal, having adjustable lengths and attached to the bottom of a hopper into which the concrete is deposited. As the patters are filled, sections of the pipe may be removed.Immediately after the concrete is placed, it should be compacted by hand pudding or a me-chanical vibrator to eliminate voids. The vibrator should be left in one position only long enough to reduce the concrete around it to a plastic mass; then the vibrator should be moved, or disintegra-tion of the aggregate will occur. In general, the vibrator should not be permitted to penetrate concrete in the prior lift.The mainly advantage of vibrating is that it permits the use of a drier concrete, which has a higher strength because of the reduced water content. Among the advantages of vibrating con-crete are the following:1. The decreased water permits a reduction in the cement and fine aggregate because less cement paste is needed. 2. The lower water content decreases shrinkage and voids. 3. The drier concrete decreases the cost of finishing the surface. 4. Mechanical vibration may replace three to eight hand puddles. 5. The lower water content increases the strength of the concrete. 6. The drier mixture permits theremoval of some patters more quickly, which may reduce the cost of patters. Curing ConcreteIf concrete is to gain its maximum strength and other desirable properties, it should be cured with adequate moisture and at a favorable tem-perature. Failure to provide these conditions may result in an inferior concrete.The initial moisture in concrete is adequate to hydrate all the cement, provided it is not should replace the moisture that does evaporate. This may be accomplished by many methods, such as leaving the patters in place, keeping the surface wet, or covering the surface with a liquid curing compound, which comes being to a water-tight membrane that prevents the escape of the initial water. Curing compounds may be applied by brushes or pressure sprayers. A gallon will cover 200 to 300 sq ft.Concrete should be placed at a temperature not less than 40 or more than 80 F.A lower tem-perature will decrease the rate of setting, while ahigher temperature will decrease the ultimate strength.Placing Concrete in Cold WeatherWhen the concrete is placed during cold weather, it is usually necessary to preheat the water, the aggregate, or both in order that the ini-tial temperature will assure an initial set and gain in strength .Preheating the water is the most ef-fective method of providing the necessary tem-perature. For this purpose a water reservoir should be equipped with pipe coils through which steam can be passed, or steam may bedischarged directly into the water, several outlets being used to given better distribution of the heat.When the temperatures of the mixtures are known, some specific charts may be used to cal-culate the temperature of concrete. A straight line pass all three scales, passing through every two known temperatures, will assure the determina-tion of the third temperature. If the surface of sand is dry, the fact lines of the scales giving the temperature of concrete should be used. However, if the sand contains about 3 percent moisture, the dotted lines should be used.Specifications usually demand that freshly placed concrete shall be kept at a temperature of not less than 70F for 3 days or 50F for 5 days after it is placed. Some proper method must be provided to keep the demanded temperature when the cold weather is estimated.Reinforcing steels for concreteCompared with concrete, steel is a high strength material. The useful strength of ordinary reinforcing steels in tension as well as compres-sion, i.e., the yield strength, is about 15 times the compressive strength of common structural con-crete, and well over 100 times its tensile strength. On the other hand, steel is a high-cost material compared with concrete. It follow that the two materials are the best used in combination if theconcrete is made to resist the compressive stresses and the compressive force, longitudinal steel reinforcing bars are located close to the ten-sion face to resist the tension force., and usually additional steel bars are so disposed that they re-sist the inclined tension stresses that are caused by the shear force in the beams. However, rein-forcement is also used for resisting compressive forces primarily where it is desired to reduce the cross-sectional dimensions of compression members, as in the lower-floor columns of multi-story buildings. Even if no such necessity exits , a minimum amount of reinforce- ment is placed in all compression members to safeguard them against the effects of small accidental bending moments that might crack and even fail an unre-inforced member.For most effective reinforcing action, it is essential that steel and concrete deform together, i. e., that there be a sufficiently strong bond be-tween the two materials to ensure that no relative movements of the steel bars and the surrounding concrete occur. This bond is provided by the rela-tively large chemical adhesion which develops at the steel-concrete interface, by the natural roughness of the mill scale of hot-rolled rein-forcing bars , and by the closely spaced rib-shap-ed surface deformations with which reinforcing bars are furnished in order to provide a high de-gree of interlocking of the two materials.Steel is used in two different ways in con-crete structures: as reinforcing steel and as prestressing steel .reinforcing steel is placed in the forms prior to casting of the concrete. Stresses in the steel, as in the hardened concrete, are caused only by the loads on the structure, except for possible parasitic stresses from shrinkage or similar causes. In contrast, in priestesses concrete structures large tension forces are applied to the reinforcement prior to letting it act jointly with the concrete in resistingexternal.The most common type of reinforcing steel is in the form of round bars, sometimes called rebars, available in a large range of diameters,from 10 to 35 mm for ordinary applications and in two heavy bar sizes off 44 and 57 mm these bars are furnished with surface deformations for the purpose of increasing resistance to slip be-tween steel and concrete minimum requirements for these deformations have been developed in experimental research. Different bar producers use different patterns, all of which satisfy these requirements.Welding of rebars in making splices, or for convenience in fabricating reinforcing cages for placement in the forms, may result in metal-lurgical changes that reduce both strength and ductility, and special restrictions must be placed both strength and ductility, and special restric-tions must be placed both on the type of steel used and the welding procedures the provisions of ASTM A706 relate specifically to welding.In reinforced concrete a long-time trend is evident toward the use of higher strength materi-als, both steel and concrete.Reinforcing bars with 40ksi yield stress , almost standard 20 years ago , have largely been replaced by bars with 60ksi yield stress , both because they are more economical and because their use tends to reduce congestion of steel in the forms .The ACI Code permits reinforcing steels up to Fy=80ksi. Such high strength steels usually yield gradually but have no yield plateau in this situation the ACI Code requires that at the speci-fied minimum yield strength the total strain shall not exceed 0.0035 this is necessary to make cur-rent design methods, which were developed for sharp-yielding steels with a yield plateau, appli-cable to such higher strength steels. there is no ASTM specification for deformed bars may be used , according to the ACI Code , providing they meet the requirements stated under special circumstances steel in this higher strength range has its place, e.g., in lower-story columns of high-rise buildings.In order to minimize corrosion of rein-forcement and consequent spelling of concrete under sever exposure conditions such as in bridge decks subjected to deicing chemicals , galvanized or epoxy-coated rebars may be specified.Repair of Concrete StructuresReinforced concrete is generally a very du-rable structural material and very little repair work is usually needed. However, its durability can be affected by a variety of causes, including those of design and construction faults, use of inferior materials and exposure to aggressive en-vironment. The need for a repair is primarily dic-tated by the severity of the deterioration as de-termined from the diagnosis. Good workmanship is essential if any thing more than just a cosmetic treatment to the creation is required.1. performance requirements of repair systemHaving established the causes of the defect by carefully diagnosing the distress, the next step should be to consider the requirements of the re-pair method that will offer an effective solution to the problem (see fig.).DurabilityIt is important to select repair materials that provide adequate durability. Materials used for the repair job should be at least as durable as the substrate concrete to which it is applied.Protection of steelThe mechanism of protection provided to the reinforcing depends on the type of repair ma-terials used. For example, cementations materials can protect the steel from further corrosion by their inhibitive effect of increasing the alkalinity of the concrete, whereas epoxy resin mortars can give protection against the ingress of oxygen,moisture and other harmful agents.Bond with substrate The bond with the substrate must produce an integral repair to prevent entry of moisture and atmospheric gases at the interface. With most re-pair materials, the bond is greatly enhanced with the use of a suitable bonding aid such as an un-filled epoxy resin systems and slurry of Portland cement, plus any latex additives for a Portland cement-based repair system. Precautions should also be taken to remove all loose and friable ma-terials from the surfaces to be bonded.Dimensional StabilityShrinkage of materials during curing should be kept to a minimum. Subsequent dimensional change should be very close in the substrate in order to prevent failureInitial Resistance to Environmentally In-duced DamageSome initial exposure conditions may lead to premature damage lo repairs. For example, partially cured Portland cement repairs can dete-riorate from hot weather preventing full hydration of the cement. To prevent this from happening extra protection during curing time may be nec-essary.Ease of ApplicationMaterials should be easily mixed and ap-plied so that they can be worked readily into small crevices and voids. Ideally, the material should not stick to tools, and should not shear while being trowel led nor slump after placement.AppearanceThe degree to which the repair material should match the existing concrete will depend on the use of the structure and the client s re-quirements. A surface coating may be required when appearance is important or when cover to reinforcement is small.2. Selection of Repair MethodsA suitable repair counteracts all the defi-ciencies which are relevant to the use of the structure. The selection of tile correct method and material for a particular, application requires careful consideration, whether to meet special requirements for placing strength, durability or other short-or long-term properties. These con-siderations include:1. Nature of the DistressIf alive crack is filled with a rigid material, then either the repair material will eventually fail or some new cracking will occur adjacent to the original crack. Repairs to live cracks must either use flexible materials to accommodate move-ments or else steps must be taken prior to the re-pair to eliminate the movement.2. Position of the CrackTechniques which rely on gravity to intro-duce the material into the crack are more suc-cessfully carried out on horizontal surfaces but are rarely effective on vertical ones.3. EnvironmentIf moisture, water or contaminants are found in the crack, then it is necessary to rectify the leaks Repair to slop leaks may be further com-plicated by the need to make the repairs while the structure is in service and the environment is damp.4. WorkmanshipThe skill the operatives available to carry put the repairs is another relevant factors. Some-times this can mean the difference between a permanent repair and premature failure of the re-pair material.5. CostThe cost of repair materials is usually small compared with the costs of providing access, preparation and actual labor.6. AppearanceThe repair surface may be unsightly, par-ticularly when it appears on a prominent part of the building. In this case, the repair system will include some form of treatment over the entire surface.Reference1 Philip Jodidio, Contemporary European Architecture, Taschen, Koln, pp.148-153 2 Ann Breen & Dick Rigby, Waterfronts, McGraw-Hill, Inc. New York, 1994, pp.297-300 3 Ann Breen & Dick Rigby, The New Waterfront, Thames and Hudson, London, 1996, pp.118-120 4 Ann Breen & Dick Rigby, The New Waterfront, Thames and Hudson, London, 1996, pp.52-55 5 Robert Holden, International Landscape Design, Laurence King Publishing, London, 1996, pp.10-27 6 A new concept in refrigerant control for heat pumps ,J.R.Harnish,IIR Conference Pa-per,Cleveland,Ohio.May,1996 7 Carrier Corporation-Catalog 523 848, 1997 8 Waste Heat Management Handbook, Na-tional Bureau of Standardc Handbook 121, Pub-lica-tion PB , February,1997 Ten design principles for air to air heat pumps,Allen Trask,ASHRAE Journal,July,1997 重庆科技学院学生毕业设计（论文）外 文 译 文学 院建 建筑工程学院 专业班级 工管103 学生姓名 李 学 号 附件1：外文资料翻译译文混凝土施工事项T.Pauly, M.J.N.Priestley 摘要：根据一般承认的惯例看,巴基斯坦的混凝土结构建筑物在结构上的质量，效用和安全需要上都留下了很多值得关注的问题。 当2005 年10月8日发生在巴基斯坦北部的一个7.6级地震的时候，这些施工技术上的缺点袒露无遗了,破坏了数以千计建筑物、桥梁, 而且造成估计79,000人的死亡。 在巴基斯坦这种十分低质量的混凝土施工技术是造成这次极广破坏的主要原因。关键字：混凝土 浇筑 养护 建筑工艺混凝土浇筑若混凝土在地面上浇筑，地面应该具有足够的含水量以避免它吸收混凝土中的水分。如果新混凝土将被浇筑在已经凝固的混凝土上或其旁边，已浇混凝土表面应该彻底清除干净，最好使用高压空气、高压水流或钢丝刷。其表应潮湿，但不应有集水，应当在整个范围内刷上少量的水泥浆，然后立即铺上一层厚度为1/2in的砂浆。新混凝土应铺筑在砂浆上或其旁边。为减少混凝土在浇筑后由于运输导致的离析，混凝土的制备应该尽可能靠近最后浇筑的地方。它应该分层浇筑以使每层可被均压实。每层浇筑间隔的时间应该限制在能够保证新浇筑的混凝土与前面浇筑的有良好的结合。当向较深的模板中浇筑混凝土时，就应该使用一根导管来限制混凝土的自由降落高度不超过3或4ft，以防止混凝土离析。这种导管是由轻金属制成的管子，具有可调节的长度而且被连接到储存的混凝土的罐的底部。当模板被浇筑满后，就可以抽出管节。混凝土一浇筑完成，应立即用手提振捣器或机器振捣器进行捣密后就应该移走，否则就会发生骨料离析。一般来说，振捣器不应该集中在先前提起的混凝土上。振捣主要优点是它允许使用较干的混凝土，由于减少了混凝土的含水量，这种混凝土有较高的强度。振捣混凝土的优点如下：1、水分的减少允许水泥和细集料的用量，因为这时需要较少的水泥浆。2、较低的含水量可减少收缩和空隙。3、较干的混凝土减少混凝土表面处理的费用。4、机械振捣可代替38个手持振捣棒。 5、较低的含水量可提高混凝土的强度。 6、较干的混合料允许较早地拆除一些模板，这样可降低模板的造价。混凝土的养护 若混凝土想要获得最高强度或其它必要特性，则应该对其用足够的水分和适当的温度进行养护。如果没能提供这些条件，则会导致劣质的混凝土。混凝土中最初的水分足够所有水泥的水化反应，只要在使用前没有被蒸发。这可以用多种方法来实现，例如把模板留在混凝土中，保持表面潮湿，或在混凝土表面覆盖一层液体养生化合物，它可以形成一种不透水的隔膜来阻止混凝土中的水分遗失。养生化合物可以用刷子或压力喷嘴加到混凝土表面。一加仑可以覆盖200300ft2。混凝土应该在40F以上或80F以下进行浇筑。低温会降低凝结速度，而高温会降低混凝土的极限强度。寒冷天气下的混凝土浇筑当混凝土在寒冷天气下浇筑时，通常有必要预先加热水、骨料或两者同时预热，以便使其初始温度能够保证混凝土的初凝并获得强度。对水进行预热是提供必要的温度最有效的方法。出于这一目的，蓄水池应该安装一个通有蒸气的蛇形管或将蒸气可以直接通到水中，这是可以使用多个排气口以提供良好的热量分布。当混合料的温度已知，一些专用图可以用来计算混凝土的温度。一条直线穿过所有三种比例，通过任意两个已知温度，就可以确定出第三个温度。如果砂的表面干燥，则应使用实线计算混凝土的温度。然而，如果砂含有3%的水分，则应使用虚线。规范通常要求新浇筑的混凝土在浇筑后应保持3天温度不低于70F或5天不低于50F。当预计有寒冷天气时必须提供一些适当的方法来保持要求的温度。用于混凝土中的钢筋与混凝土相比，钢是一种高强度材料。普通钢筋在抗拉和抗压时可以利用的强度，即屈服强度，约为普通的结构混凝土抗压强度的1.5倍，而且超过抗拉强度的100倍。另一方面，与混凝土相比，钢材的成本要高得多。所以，两种材料最好的结合使用是混凝土用于抵抗压应力。因此，在钢筋混凝土梁内，混凝土抵抗压应力，纵向钢筋配置在靠近受拉面处以抵抗拉应力，通常还附加配有一些钢筋，抵抗梁内的剪应力所引起的斜向拉应力。然而，钢材也可以用于抵抗应力，主要是为了减小受压构件的截面尺寸，例如用于多层建筑的下部楼层柱。即使不存在这种必要性，所有受压构件也要配置最少数量的钢筋， 以保证这些构件在偶然出现的小弯矩作用下的安全性，在这情况下，不加钢筋的混凝土构件可能会开裂，甚至破坏。使配筋最有效的发挥作用的基本条件是钢筋和混凝土的变形要一致，即这两种材料间要有足够强的黏结力，以确保钢筋和其周围混凝土间不发生相对移动。这种黏结力是由钢筋-混凝土结合面上较强的化学粘合作用，热轧钢筋表面层的固有粗