土木工程畢業(yè)設計中英文翻譯

1、附錄：中英文翻譯英文部分：loadsloads that act on structures are usually classified as dead loads or live loads.dead loads are fixed in location and constant in magnitude throughout the life of the structure.usually the self-weight of a structure is the most important part of the structure and the unit weight of

2、the material.concrete density varies from about 90 to 120 pcf (14 to 19 )for lightweight concrete,and is about 145 pcf (23 )for normal concrete.in calculating the dead load of structural concrete,usually a 5 pcf (1 )increment is included with the weight of the concrete to account for the presence of

3、 the reinforcement.live loads are loads such as occupancy,snow,wind,or traffic loads,or seismic forces.they may be either fully or partially in place,or not present at all.they may also change in location.althought it is the responsibility of the engineer to calculate dead loads,live loads are usual

4、ly specified by local,regional,or national codes and specifications.typical sources are the publications of the american national standards institute,the american association of state highway and transportation officials and,for wind loads,the recommendations of the asce task committee on wind force

5、s.specified live the loads usually include some allowance for overload,and may include measures such as posting of maximum loads will not be exceeded.it is oftern important to distinguish between the specified load,and what is termed the characteristic load,that is,the load that actually is in effec

6、t under normal conditions of service,which may be significantly less.in estimating the long-term deflection of a structure,for example,it is the characteristic load that is important,not the specified load.the sum of the calculated dead load and the specified live load is called the service load,bec

7、ause this is the maximum load which may reasonably be expected to act during the service resisting is a multiple of the service load.strengththe strength of a structure depends on the strength of the materials from which it is made.minimum material strengths are specified in certain standardized way

8、s.the properties of concrete and its components,the methods of mixing,placing,and curing to obtain the required quality,and the methods for testing,are specified by the american concrete insititue(aci).included by refrence in the same document are standards of the american society for testing materi

9、als(astm)pertaining to reinforcing and prestressing steels and concrete.strength also depends on the care with which the structure is built.member sizes may differ from specified dimensions,reinforcement may be out of position,or poor placement of concrete may result in voids.an important part of th

10、e job of the ergineer is to provide proper supervision of construction.slighting of this responsibility has had disastrous consequences in more than one instance.structural safetysafety requires that the strength of a structure be adequate for all loads that may conceivably act on it.if strength cou

11、ld be predicted accurately and if loads were known with equal certainty,then safely could be assured by providing strength just barely in excess of the requirements of the loads.but there are many sources of uncertainty in the estimation of loads as well as in analysis,design,and construction.these

12、uncertainties require a safety margin.in recent years engineers have come to realize that the matter of structural safety is probabilistic in nature,and the safety provisions of many current specifications reflect this view.separate consideration is given to loads and strength.load factors,larger th

13、an unity,are applied to the calculated dead loads and estimated or specified service live loads,to obtain factorde loads that the member must just be capable of sustaining at incipient failure.load factors pertaining to different types of loads vary,depending on the degree of uncertainty associated

14、with loads of various types,and with the likelihood of simultaneous occurrence of different loads.early in the development of prestressed concrete,the goal of prestressing was the complete elimination of concrete ternsile stress at service loads.the concept was that of an entirely new,homogeneous ma

15、terial that woukd remain uncracked and respond elastically up to the maximum anticipated loading.this kind of design,where the limiting tensile stressing,while an alternative approach,in which a certain amount of tensile amount of tensile stress is permitted in the concrete at full service load,is c

16、alled partial prestressing.there are cases in which it is necessary to avoid all risk of cracking and in which full prestressing is required.such cases include tanks or reservious where leaks must be avoided,submerged structures or those subject to a highly corrosive envionment where maximum protect

17、ion of reinforcement must be insured,and structures subject to high frequency repetition of load where faatigue of the reinforcement may be a consideration.however,there are many cses where substantially improved performance,reduced cost,or both may be obtained through the use of a lesser amount of

18、prestress.full predtressed beams may exhibit an undesirable amount of upward camber because of the eccentric prestressing force,a displacement that is only partially counteracted by the gravity loads producing downward deflection.this tendency is aggrabated by creep in the concrete,which magnigies t

19、he upward displacement due to the prestress force,but has little influence on the should heavily prestressed members be overloaded and fail,they may do so in a brittle way,rather than gradually as do beams with a smaller amount of prestress.this is important from the point of view of safety,because

20、suddenfailure without warning is dangeroud,and gives no opportunity for corrective measures to be taken.furthermore,experience indicates that in many cases improved economy results from the use of a combination of unstressed bar steel and high strength prestressed steel tendons.while tensile stress

21、and possible cracking may be allowed at full service load,it is also recognized that such full service load may be infrequently applied.the typical,or characteristic,load acting is likely to be the dead load plus a small fraction of the specified live load.thus a partially predtressed beam may not b

22、e subject to tensile stress under the usual conditions of loading.cracks may from occasionally,when the maximum load is applied,but these will close completely when that load is removed.they may be no more objectionable in prestressed structures than in ordinary reinforced.they may be no more object

23、ionable in prestressed structures than in ordinary reinforced concrete,in which flexural cracks always form.they may be considered a small price for the improvements in performance and economy that are obtained.it has been observed that reinforced concrete is but a special case of prestressed concre

24、te in which the prestressing force is zero.the behavior of reinforced and prestressed concrete beams,as the failure load is approached,is essentially the same.the joint european committee on concrete establishes threee classes of prestressed beams.class 1:fully prestressed,in which no tensile stress

25、 is allowed in the concrete at service load.class 2:partially prestressed, in which occasional temporary cracking is permitted under infrequent high loads.class 3:partially prestressed,in which there may be permanent cracks provided that their width is suitably limited.the choise of a suitable amoun

26、t of prestress is governed by a variety of factors.these include the nature of the loading (for exmaple,highway or railroad bridged,storage,ect.),the ratio of live to dead load,the frequency of occurrence of loading may be reversed,such as in transmission poles,a high uniform prestress would result

27、ultimate strength and in brittle failure.in such a case,partial prestressing provides the only satifactory solution.the advantages of partial prestressing are important.a smaller prestress force will be required,permitting reduction in the number of tendons and anchorages.the necessary flexural stre

28、ngth may be provided in such cases either by a combination of prestressed tendons and non-prestressed reinforcing bars,or by an adequate number of high-tensile tendons prestredded to level lower than the prestressing force is less,the size of the bottom flange,which is requied mainly to resist the c

29、ompression when a beam is in the unloaded stage,can be reduced or eliminated altogether.this leads in turn to significant simplification and cost reduction in the construction of forms,as well as resulting in structures that are mor pleasing esthetically.furthermore,by relaxing the requirement for l

30、ow service load tension in the concrete,a significant improvement can be made in the deflection characteristics of a beam.troublesome upward camber of the member in the unloaded stage fan be avoeded,and the prestress force selected primarily to produce the desired deflection for a particular loading

31、 condition.the behavior of partially prestressed beamsm,should they be overloaded to failure,is apt to be superior to that of fully prestressed beams,because the improved ductility provides ample warning of distress.英譯漢：荷 載作用在結構上的荷載通常分為恒載或活載。在結構的整個使用壽命期間，恒載的位置是固定的，大小是不變的。通常，結構的自重是恒載的最重要部分。它可以根據(jù)結構的尺寸

32、和材料的單位重量進行精確計算?；炷恋拿芏仁亲兓模瑢τ谳p質混凝土大約從90120pcf（1419 ），對于標準混凝土大約為145pcf（23 ）。在計算結構混凝土的恒載時，考慮到鋼筋的存在，通常除了混凝土的重量以外還計入5pcf（1 ）的增加量。荷載就是諸如居住、雪、風、車輛荷載或地震力等荷載。它們可能全部或部分地出現(xiàn)，或者根本不出現(xiàn)。這些荷載的位置也是會變化的。計算恒載時工程師的職責，然而活載通常由當?shù)氐?、地區(qū)的或國家的規(guī)范和準則所規(guī)定。標準的來源是美國國家標準學會、美國州際公路與運輸工作者協(xié)會主辦的刊物，對于風荷載采用美國土木工程學會風力專題委員會的建議。規(guī)定活載通常包含某些容許的超載，

33、并可以明顯的或隱含地計入動態(tài)影響?；钶d可以采用標明樓板或橋梁最大荷載那樣的措施在某種程度上加以控制，但是也不能肯定這些荷載不會被超過。將規(guī)定荷載和所謂特征荷載區(qū)別開來往往是很重要的，也就是說，后者是正常使用情況下實際起作用的荷載，它可能很小。例如在計算結構的長期撓度時，重要的是特征荷載，而不是規(guī)定荷載。計算得到的荷載和規(guī)定活載的和稱為使用荷載，因為這是在結構使用壽命期間可預料到的要作用在其上的最大荷載。使用荷載乘以一個系數(shù)就是計算荷載，即破壞荷載，它就是結構必須恰好能承受的荷載。強度結構的強度取決于建造它的材料的強度。材料的最小強度都以一些標準的方式來規(guī)定。美國混凝土學會對混凝土的性質及其成分

34、、滿足質量要求的拌和、澆筑和養(yǎng)生方法以及試驗方法均作了規(guī)定。在同一文件中，作為參考也列入了美國材料試驗協(xié)會關于普通鋼筋、預應力鋼筋和混凝土的標準。強度也取決于結構施工的精心程度。構建的大小可能與規(guī)定的尺寸有所不同，鋼筋的位置可能發(fā)生移動，或者由于混凝土澆筑得不好可能會造成空洞。工程師工作的重要職責是要保證應有的施工監(jiān)督。工程師的失職曾經(jīng)不止一次產生了造成巨大損失的后果。結構安全度安全性要求結構的強度足以承受可以預料到的，作用在結構上的全部荷載。如果強度能夠精確地預先計算出來而且荷載也可以同樣確切地知道的話，則所提供的強度只要稍微超過荷載的要求就能保證安全?？墒怯性S多因素會導致在荷載的估算以及分

35、析、設計和施工等方面的不確定性。這些不確定因素要求具有安全儲備。近些年來，工程師們已經(jīng)開始認識到結構安全度這個問題在實質上就是概率統(tǒng)計問題，因此許多現(xiàn)行規(guī)范的安全規(guī)定都反映了這一觀點。荷載和強度分別加以考慮。將大于1的荷載系數(shù)乘以算得到的恒載和估算或規(guī)定的使用活載，可以得到構件在開始破壞時恰好能承受的計算荷載。對于不同類型的荷載，荷載系數(shù)是不相同的，它取決于各種不同荷載和不同荷載可能同時出現(xiàn)的不確定程度。在預應力混凝土發(fā)展的早期，預加應力的目的是要完全消除在使用荷載作用下混凝土中的拉應力。這曾經(jīng)是一種全新的勻質材料的概念，認為這種材料能夠不開裂并且保持彈性工作狀態(tài)，直至達到其最大的設計荷載。在全部使用荷載作用下，混凝土的極限拉應力值為零的這種設計，通常稱為之全預應力設計；而另一種在全部荷載作用下容許混凝土內產生一定大小的拉應力的設計方法，稱為部分預應力設計。有些場合必須避免任何產生裂縫的危險，此時需要采用預應力。這些場合包括：不能產生滲漏的容器或水庫，必須保證具有最大鋼筋保護層的水下結構和在強腐蝕環(huán)境中的結構，必須考慮鋼筋疲勞問題的承受高頻重復荷載的結構。但是，在許多場合中，只要施加少量的預應力就可以顯著地改善結構的工作性能，降低造