土木工程外文翻譯原文

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土木工程外文翻譯原文

　　土木工程是建造各類工程設施的科學技術的統稱。以下是有關土木工程的外文翻譯，一起來看看吧！

土木工程外文翻譯原文

　　由于鋼筋混凝土截面在均質性上與標準的木材或鋼的截面存在著差異，因此，需要對結構設計的基本原理進行修改。將鋼筋混凝土這種非均質截面的兩種組成部分按一定比例適當布置，可以最好的利用這兩種材料。這一要求是可以達到的。因混凝土由配料攪拌成濕拌合物，經過振搗并凝固硬化，可以做成任何一種需要的形狀。如果拌制混凝土的各種材料配合比恰當，則混凝土制成品的強度較高，經久耐用，配置鋼筋后，可以作為任何結構體系的主要構件。

　　澆筑混凝土所需要的技術取決于即將澆筑的構件類型，諸如：柱、梁、墻、板、基礎，大體積混凝土水壩或者繼續延長已澆筑完畢并且已經凝固的混凝土等。對于梁、柱、墻等構件，當模板清理干凈后應該在其上涂油，鋼筋表面的銹及其他有害物質也應該被清除干凈。澆筑基礎前，應將坑底土夯實并用水浸濕6英寸，以免土壤從新澆的混凝土中吸收水分。一般情況下，除使用混凝土泵澆筑外，混凝土都應在水平方向分層澆筑，并使用插入式或表面式高頻電動振搗器搗實。必須記住，過分的振搗將導致骨料離析和混凝土泌漿等現象，因而是有害的。

　　水泥的水化作用發生在有水分存在，而且氣溫在50°F以上的條件下。為了保證水泥的水化作用得以進行，必須具備上述條件。如果干燥過快則會出現表面裂縫，這將有損與混凝土的強度，同時也會影響到水泥水化作用的充分進行。

　　設計鋼筋混凝土構件時顯然需要處理大量的參數，諸如寬度、高度等幾何尺寸，配筋的面積，鋼筋的應變和混凝土的應變，鋼筋的應力等等。因此，在選擇混凝土截面時需要進行試算并作調整，根據施工現場條件、混凝土原材料的供應情況、業主提出的特殊要求、對建筑和凈空高度的要求、所用的設計規范以及建筑物周圍環境條件等最后確定截面。鋼筋混凝土通常是現場澆注的合成材料，它與在工廠中制造的標準的鋼結構梁、柱等不同，因此對于上面所提到的一系列因素必須予以考慮。

　　對結構體系的各個部位均需選定試算截面并進行驗算，以確定該截面的名義強度是否足以承受所作用的計算荷載。由于經常需要進行多次試算，才能求出所需的'截面，因此設計時第一次采用的數值將導致一系列的試算與調整工作。

　　選擇混凝土截面時，采用試算與調整過程可以使復核與設計結合在一起。因此，當試算截面選定后，每次設計都是對截面進行復核。手冊、圖表和微型計算機以及專用程序的使用，使這種設計方法更為簡捷有效，而傳統的方法則是把鋼筋混凝土的復核與單純的設計分別進行處理。

　　由于和土木工程中任何其他工種的施工方法與費用相比較，土方挖運的施工方法與費用的變化都要快得多，因此對于有事業心的人來說，土方工程是一個可以大有作為的領域。在1935年，目前采用的利用輪胎式機械設備進行土方挖運的方法大多數還沒有出現。那是大部分土方是采用窄軌鐵路運輸，在這目前來說是很少采用的。當時主要的開挖方式是使用正鏟、反鏟、拉鏟或抓斗等挖土機，盡管這些機械目前仍然在廣泛應用，但是它們只不過是目前所采用的許多方法中的一小部分。因此，一個工程師為了使自己在土方挖運設備方面的知識跟得上時代的發展，他應當花費一些時間去研究現代的機械。一般說來，有關挖土機、裝載機和運輸機械的唯一可靠而又最新的資料可以從制造廠商處獲得。

　　土方工程或土方挖運工程指的是把地表面過高處的土壤挖去（挖方），并把它傾卸到地表面過低的其他地方（填方）。為了降低土方工程費用，填方量應該等于挖方量，而且挖方地點應該盡可能靠近土方量相等的填方地點，以減少運輸量和填方的二次搬運。土方設計這項工作落到了從事道路設計的工程師的身上，因為土方工程的設計比其他任何工作更能決定工程造價是否低廉。根據現有的地圖和標高，道路工程師應在設計繪圖室中的工作也并不是徒勞的。它將幫助他在最短的時間內獲得最好的方案。

　　費用最低的運土方法是用同一臺機械直接挖方取土并且卸土作為填方。這并不是經常可以做到的，但是如果能夠做到則是很理想的，因為這樣做既快捷又省錢。拉鏟挖土機。推土機和正鏟挖土機都能做到這點。拉鏟挖土機的工作半徑最大。推土機所推運的圖的數量最多，只是運輸距離很短。拉鏟挖土機的缺點是只能挖比它本身低的土，不能施加壓力挖入壓實的土壤內，不能在陡坡上挖土，而且挖。卸都不準確。

　　正鏟挖土機介于推土機和拉鏟挖土機的之間，其作用半徑大于推土機，但小于拉鏟挖土機。正鏟挖土機能挖取豎直陡峭的工作面，這種方式對推土機司機來說是危險的，而對拉鏟挖土機則是不可能的。每種機械設備應該進行最適合它的性能的作業。正鏟挖土機不能挖比其停機平面低很多的土，而深挖堅實的土壤時，反鏟挖土機最適用，但其卸料半徑比起裝有正鏟的同一挖土機的卸料半徑則要小很多。

　　在比較平坦的場地開挖，如果用拉鏟或正鏟挖土機運輸距離太遠時，則裝有輪胎式的斗式鏟運機就是比不可少的。它能在比較平的地面上挖較深的土（但只能挖機械本身下面的土），需要時可以將土運至幾百米遠，然后卸土并在卸土的過程中把土大致鏟平。在挖掘硬土時，人們發現在開挖場地經常用一輛助推拖拉機（輪式或履帶式），對返回挖土的鏟運機進行助推這種施工方法是經濟的。一旦鏟運機裝滿，助推拖拉機就回到開挖的地點去幫助下一臺鏟運機。

　　斗式鏟運機通常是功率非常大的機械，許多廠家制造的鏟運機鏟斗容量為8 m，滿載時可達10 m。最大的自行式鏟運機鏟斗容量為19立方米（滿載時為25 m），由430馬力的牽引發動機驅動。

　　翻斗機可能是使用最為普遍的輪胎式運輸設備，因為它們還可以被用來送混凝土或者其他建筑材料。翻斗車的車斗位于大橡膠輪胎車輪前軸的上方，盡管鉸接式翻斗車的卸料方向有很多種，但大多數車斗是向前翻轉的。最小的翻斗車的容量大約為0.5立方米，而最大的標準型翻斗車的容量大約為4.5m。特殊型式的翻斗車包括容量為4 m的自裝式翻斗車，和容量約為0.5 m的鉸接式翻斗車。必須記住翻斗車與自卸卡車之間的區別。翻斗車車斗向前傾翻而司機坐在后方卸載，因此有時被稱為后卸卡車。

　　規范的主要目的是提供一般性的設計原理和計算方法，以便驗算結構的安全度。就目前的趨勢而言，安全系數與所使用的材料性質及其組織情況無關，通常把它定義為發生破壞的條件與結構可預料的最不利的工作條件之比值。這個比值還與結構的破壞概率（危險率）成反比。

　　破壞不僅僅指結構的整體破壞，而且還指結構不能正常的使用，或者，用更為確切的話來說，把破壞看成是結構已經達到不能繼續承擔其設計荷載的“極限狀態”。通常有兩種類型的極限狀態，即：

　　（1）強度極限狀態，它相當于結構能夠達到的最大承載能力。其例子包括結構的局部屈曲和整體不穩定性；某此界面失效，隨后結構轉變為機構；疲勞破壞；引起結構幾何形狀顯著變化的彈性變形或塑性變形或徐變；結構對交變荷載、火災和爆炸的敏感性。

　　（2）使用極限狀態，它對應著結構的使用功能和耐久性。器例子包括結構失穩之前的過大變形和位移；早期開裂或過大的裂縫；較大的振動和腐蝕。

　　根據不同的安全度條件，可以把結構驗算所采用的計算方法分成：

　　（1）確定性的方法，在這種方法中，把主要參數看作非隨機參數。

　　（2）概率方法，在這種方法中，主要參數被認為是隨機參數。

　　此外，根據安全系數的不同用途，可以把結構的計算方法分為：

　　（1）容許應力法，在這種方法中，把結構承受最大荷載時計算得到的應力與經過按規定的安全系數進行折減后的材料強度作比較。

　　（2）極限狀態法，在這種方法中，結構的工作狀態是以其最大強度為依據來衡量的。由理論分析確定的這一最大強度應不小于結構承受計算荷載所算得的強度（極限狀態）。計算荷載等于分別乘以荷載系數的活載與恒載之和。

　　把對應于不乘以荷載系數的活載和恒載的工作（使用）條件的應力與規定值（使用極限狀態）相比較。根據前兩種方法和后兩種方法的四種可能組合，我們可以得到一些實用的計算方法。通常采用下面兩種計算方法：

　　確定性的方法，這種方法采用容許應力。

　　概率方法，這種方法采用極限狀態。

　　至少在理論上，概率法的主要優點是可以科學的考慮所有隨機安全系數，然后將這些隨機安全系數組合成確定的安全系數。概率法取決于：

　　（1）制作和安裝過程中材料強度的隨機分布（整個結構的力學性能數值的分散性）；

　　（2）截面和結構幾何尺寸的不確定性（由結構制作和安裝造成的誤差和缺陷而引起的）；

　　對作用在結構上的活載和恒載的預測的不確定性；

　　所采用的近似計算方法有關的不精確性（實際應力與計算應力的偏差）。

　　此外，概率理論意味著可以基于下面幾個因素來確定允許的危險率，例如：

　　建筑物的重要性和建筑物破壞造成的危害性；

　　（2）由于建筑物破壞使生活受到威脅的人數；

　　（3）修復建筑的可能性；

　　（4）建筑物的預期壽命。

　　所有這些因素均與經濟和社會條件有關，例如：

　　（1）建筑物的初始建設費；

　　（2）建筑物使用期限內的折舊費；

　　（3）由于建筑物破壞而造成的物質和材料損失費；

　　（4）在社會上造成的不良影響；

　　（5）精神和心理上的考慮。

　　就給定的安全系數而論，所有這些參數的確定都是以建筑物的最佳成本為依據的。但是，應該考慮到進行全概率分析的困難。對于這種分析來說，應該了解活載及其所引起的盈利的分布規律、材料的力學性能的分散性和截面的結構幾何尺寸的分散性。此外，由于強度的分布規律和應力的分布規律之間的相互關系是困難的。這些實際困難可以采用兩種方法來克服。第一種方法對材料和荷載采用不同的安全系數，而不需要采用概率準則；第二種方法是引入一些而簡化假設的近似概率方法（半概率方法）。

　　外文翻譯

　　It is this deviation in the composition of a reinforces concrete section from the homogeneity of standard wood or steel sections that requires a modified approach to the basic principles of structural design. The two components of the heterogeneous reinforced concrete section are to be so arranged and proportioned that optimal use is made of the materials involved. This is possible because concrete can easily be given any desired shape by placing and compacting the wet mixture of the constituent ingredients are properly proportioned, the finished product becomes strong, durable, and, in combination with the reinforcing bars, adaptable for use as main members of any structural system.

　　The techniques necessary for placing concrete depend on the type of member to be cast: that is, whether it is a column, a bean, a wall, a slab, a foundation. a mass columns, or an extension of previously placed and hardened concrete. For beams, columns, and walls, the forms should be well oiled after cleaning them, and the reinforcement should be cleared of rust and other harmful materials. In foundations, the earth should be compacted and thoroughly moistened to about 6 in. in depth to avoid absorption of the moisture present in the wet concrete. Concrete should always be placed in horizontal layers which are compacted by means of high frequency power-driven vibrators of either the immersion or external type, as the case requires, unless it is placed by pumping. It must be kept in mind, however, that over vibration can be harmful since it could cause segregation of the aggregate and bleeding of the concrete.

　　Hydration of the cement takes place in the presence of moisture at temperatures above 50°F. It is necessary to maintain such a condition in order that the chemical hydration reaction can take place. If drying is too rapid, surface cracking takes place. This would result in reduction of concrete strength due to cracking as well as the failure to attain full chemical hydration.

　　It is clear that a large number of parameters have to be dealt with in proportioning a reinforced concrete element, such as geometrical width, depth, area of reinforcement, steel strain, concrete strain, steel stress, and so on. Consequently, trial and adjustment is necessary in the choice of concrete sections, with assumptions based on conditions at site, availability of the constituent materials, particular demands of the owners, architectural and headroom requirements, the applicable codes, and environmental reinforced concrete is often a site-constructed composite, in contrast to the standard mill-fabricated beam and column sections in steel structures.

　　A trial section has to be chosen for each critical location in a structural system. The trial section has to be analyzed to determine if its nominal resisting strength is adequate to carry the applied factored load. Since more than one trial is often necessary to arrive at the required section, the first design input step generates into a series of trial-and-adjustment analyses.

　　The trial-and –adjustment procedures for the choice of a concrete section lead to the convergence of analysis and design. Hence every design is an analysis once a trial section is chosen. The availability of handbooks, charts, and personal computers and programs supports this approach as a more efficient, compact, and speedy instructional method compared with the traditional approach of treating the analysis of reinforced concrete separately from pure design.

　　Because earthmoving methods and costs change more quickly than those in any other branch of civil engineering, this is a field where there are real opportunities for the enthusiast. In 1935 most of the methods now in use for carrying and excavating earth with rubber-tyred equipment did not exist. Most earth was moved by narrow rail track, now relatively rare, and the main methods of excavation, with face shovel, backacter, or dragline or grab, though they are still widely used are only a few of the many current methods. To keep his knowledge of earthmoving equipment up to date an engineer must therefore spend tine studying modern machines. Generally the only reliable up-to-date information on excavators, loaders and transport is obtainable from the makers.

　　Earthworks or earthmoving means cutting into ground where its surface is too high ( cuts ), and dumping the earth in other places where the surface is too low ( fills). Toreduce earthwork costs, the volume of the fills should be equal to the volume of the cuts and wherever possible the cuts should be placednear to fills of equal volume so as to reduce transport and double handlingof the fill. This work of earthwork design falls on the engineer who lays out the road since it is the layout of the earthwork more than anything else which decides its cheapness. From the available maps ahd levels, the engineering must try to reach as many decisions as possible in the drawing office by drawing cross sections of the earthwork. On the site when further information becomes available he can make changes in jis sections and layout,but the drawing lffice work will not have been lost. It will have helped him to reach the best solution in the shortest time.

　　The cheapest way of moving earth is to take it directly out of the cut and drop it as fill with the same machine. This is not always possible, but when it canbe done it is ideal, being both quick and cheap. Draglines, bulldozers and face shovels an do this. The largest radius is obtained with the dragline,and the largest tonnage of earth is moved by the bulldozer, though only over short distances.The disadvantages of the dragline are that it must dig below itself, it cannot dig with force into compacted material, it cannot dig on steep slopws, and its dumping and digging are not accurate.

　　Face shovels are between bulldozers and draglines, having a larger radius of action than bulldozers but less than draglines. They are anle to dig into a vertical cliff face in a way which would be dangerous tor a bulldozer operator and impossible for a dragline. Each piece of equipment should be level of their tracks and for deep digs in compact material a backacter is most useful, but its dumping radius is considerably less than that of the same escavator fitted with a face shovel.

　　Rubber-tyred bowl scrapers are indispensable for fairly level digging where the distance of transport is too much tor a dragline or face shovel. They can dig the material deeply ( but only below themselves ) to a fairly flat surface, carry it hundreds of meters if need be, then drop it and level it roughly during the dumping. For hard digging it is often found economical to keep a pusher tractor ( wheeled or tracked ) on the digging site, to push each scraper as it returns to dig. As soon as the scraper is full,the pusher tractor returns to the beginning of the dig to heop to help the nest scraper.

　　Bowl scrapers are often extremely powerful machines;many makers build scrapers of 8 cubic meters struck capacity, which carry 10 m heaped. The largest self-propelled scrapers are of 19 m struck capacity ( 25 m heaped )and they are driven by a tractor engine of 430 horse-powers.

　　Dumpers are probably the commonest rubber-tyred transport since they can also conveniently be used for carrying concrete or other building materials. Dumpers have the earth container over the front axle on large rubber-tyred wheels, and the container tips forwards on most types, though in articulated dumpers the direction of tip can be widely varied. The smallest dumpers have a capacity of about 0.5 m , and the largest standard types are of about 4.5 m . Special types include the self-loading dumper of up to 4 m and the articulated type of about 0.5 m . The distinction between dumpers and dump trucks must be remembered .dumpers tip forwards and the driver sits behind the load. Dump trucks are heavy, strengthened tipping lorries, the driver travels in front lf the load and the load is dumped behind him, so they are sometimes called rear-dump trucks.

　　The principal scope of specifications is to provide general principles and computational methods in order to verify safety of structures. The “ safety factor ”, which according to modern trends is independent of the nature and combination of the materials used, can usually be defined as the ratio between the conditions. This ratio is also proportional to the inverse of the probability ( risk ) of failure of the structure.

　　Failure has to be considered not only as overall collapse of the structure but also as unserviceability or, according to a more precise. Common definition. As the reaching of a “ limit state ” which causes the construction not to accomplish the task it was designed for. There are two categories of limit state :

　　(1)Ultimate limit sate, which corresponds to the highest value of the load-bearing capacity. Examples include local buckling or global instability of the structure; failure of some sections and subsequent transformation of the structure into a mechanism; failure by fatigue; elastic or plastic deformation or creep that cause a substantial change of the geometry of the structure; and sensitivity of the structure to alternating loads, to fire and to explosions.

　　(2)Service limit states, which are functions of the use and durability of the structure. Examples include excessive deformations and displacements without instability; early or excessive cracks; large vibrations; and corrosion.

　　Computational methods used to verify structures with respect to the different safety conditions can be separated into:

　　(1)Deterministic methods, in which the main parameters are considered as nonrandom parameters.

　　(2)Probabilistic methods, in which the main parameters are considered as random parameters.

　　Alternatively, with respect to the different use of factors of safety, computational methods can be separated into:

　　(1)Allowable stress method, in which the stresses computed under maximum loads are compared with the strength of the material reduced by given safety factors.

　　(2)Limit states method, in which the structure may be proportioned on the basis of its maximum strength. This strength, as determined by rational analysis, shall not be less than that required to support a factored load equal to the sum of the factored live load and dead load ( ultimate state ).

　　The stresses corresponding to working ( service ) conditions with unfactored live and dead loads are compared with prescribed values ( service limit state ) . From the four possible combinations of the first two and second two methods, we can obtain some useful computational methods. Generally, two combinations prevail:

　　(1)deterministic methods, which make use of allowable stresses.

　　(2)Probabilistic methods, which make use of limit states.

　　The main advantage of probabilistic approaches is that, at least in theory, it is possible to scientifically take into account all random factors of safety, which are then combined to define the safety factor. probabilistic approaches depend upon :

　　(1) Random distribution of strength of materials with respect to the conditions of fabrication and erection ( scatter of the values of mechanical properties through out the structure );

　　(2) Uncertainty of the geometry of the cross-section sand of the structure ( faults and imperfections due to fabrication and erection of the structure );

　　(3) Uncertainty of the predicted live loads and dead loads acting on the structure;

　　(4)Uncertainty related to the approximation of the computational method used ( deviation of the actual stresses from computed stresses ).

　　Furthermore, probabilistic theories mean that the allowable risk can be based on several factors, such as :

　　(1) Importance of the construction and gravity of the damage by its failure;

　　(2)Number of human lives which can be threatened by this failure;

　　(3)Possibility and/or likelihood of repairing the structure;

　　(4) Predicted life of the structure.

　　All these factors are related to economic and social considerations such as：

　　(1) Initial cost of the construction;

　　(2) Amortization funds for the duration of the construction;

　　(3) Cost of physical and material damage due to the failure of the construction;

　　(4) Adverse impact on society;

　　(5) Moral and psychological views.

　　The definition of all these parameters, for a given safety factor, allows construction at the optimum cost. However, the difficulty of carrying out a complete probabilistic analysis has to be taken into account. For such an analysis the laws of the distribution of the live load and its induced stresses, of the scatter of mechanical properties of materials, and of the geometry of the cross-sections and the structure have to be known. Furthermore, it is difficult to interpret the interaction between the law of distribution of strength and that of stresses because both depend upon the nature of the material, on the cross-sections and upon the load acting on the structure. These practical difficulties can be overcome in two ways. The first is to apply different safety factors to the material and to the loads, without necessarily adopting the probabilistic criterion. The second is an approximate probabilistic method which introduces some simplifying assumptions ( semi-probabilistic methods ) .

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