土木工程畢業(yè)設(shè)計(jì)中英文翻譯

1、精選優(yōu)質(zhì)文檔-傾情為你奉上專心-專注-專業(yè)222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 inlocation and constant in magnitude throughout the life of the structure.Usually the self-weight of astructure is the most important part of the structure a

2、nd the unit weight of the material.Concrete densityvaries from about 90 to 120 pcf (14 to 19 KN/m )for lightweight concrete,and is about 145 pcf (23KN/m )for normal concrete.In calculating the dead load of structural concrete,usually a 5 pcf (1KN/m )increment is included with the weight of the concr

3、ete to account for the presence of 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 calcula

4、te dead loads,live loads are usuallyspecified by local,regional,or national codes and specifications.Typical sources are the publications ofthe American National Standards Institute,the American Association of State Highway andTransportation Officials and,for wind loads,the recommendations of the AS

5、CE Task Committee on Wind Forces.Specified live the loads usually include some allowance for overload,and may include measuressuch as posting of maximum loads will not be exceeded.It is oftern important to distinguish between thespecified load,and what is termed the characteristic load,that is,the l

6、oad that actually is in effect undernormal 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

7、 called the service load,becausethis is the maximum load which may reasonably be expected to act during the service resisting is a multiple of the service load.S trengthT he strength of a structure depends on the strength of the materials from which it is made.Minimummaterial strengths are specified

8、 in certain standardized ways.The properties of concrete and itscomponents,the methods of mixing,placing,and curing to obtain the required quality,and the methods fortesting,are specified by the American Concrete Insititue(ACI).Included by refrence in the same documentare standards of the American S

9、ociety for Testing Materials(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 fromspecified dimensions,reinforcement may be out of position,or poor placement of concrete may result invoids.

10、An important part of the job of the ergineer is to provide proper supervision ofconstruction.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 ac

11、t onit.If strength could be predicted accurately and if loads were known with equal certainty,then safelycould be assured by providing strength just barely in excess of the requirements of the loads.But there aremany sources of uncertainty in the estimation of loads as well as in analysis,design,and

12、 construction.These 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.Lo

13、ad factors,larger than unity,are applied tothe calculated dead loads and estimated or specified service live loads,to obtain factorde loads that themember must just be capable of sustaining at incipient failure.Load factors pertaining to different typesof loads vary,depending on the degree of uncert

14、ainty associated 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 completeelimination of concrete ternsile stress at service loads.The concept was that of an entirelynew

15、,homogeneous material that woukd remain uncracked and respond elastically up to the maximumanticipated loading.This kind of design,where the limiting tensile stressing,while an alternativeapproach,in which a certain amount of tensile amount of tensile stress is permitted in the concrete at full serv

16、ice load,is called partial prestressing.There are cases in which it is necessary to avoid all risk of cracking and in which full prestressing isrequired.Such cases include tanks or reservious where leaks must be avoided,submerged structures orthose subject to a highly corrosive envionment where maxi

17、mum protection of reinforcement must beinsured,and structures subject to high frequency repetition of load where faatigue of the reinforcementmay be a consideration.However,there are many cses where substantially improved performance,reduced cost,or both maybe obtained through the use of a lesser am

18、ount of prestress.Full predtressed beams may exhibit anundesirable amount of upward camber because of the eccentric prestressing force,a displacement that isonly partially counteracted by the gravity loads producing downward deflection.This tendency isaggrabated by creep in the concrete,which magnig

19、ies the upward displacement due to the prestressforce,but has little influence on the should heavily prestressed members be overloaded and fail,they maydo so in a brittle way,rather than gradually as do beams with a smaller amount of prestress.This isimportant from the point of view of safety,becaus

20、e suddenfailure without warning is dangeroud,and givesno opportunity for corrective measures to be taken.Furthermore,experience indicates that in many casesimproved 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 recognizedthat such full service load may be infrequently applied.The typical,or characteristic,load acting is likelyto be the dead load plus a small fraction of the specified live load.Thus a partially predtressed beam maynot be s

22、ubject to tensile stress under the usual conditions of loading.Cracks may from occasionally,whenthe maximum load is applied,but these will close completely when that load is removed.They may be nomore objectionable in prestressed structures than in ordinary reinforced.They may be no moreobjectionabl

23、e in prestressed structures than in ordinary reinforced concrete,in which flexural cracksalways 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 concrete in w

24、hichthe 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 is allo

25、wed 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 amount of pre

26、stress is governed by a variety of factors.These include thenature of the loading (for exmaple,highway or railroad bridged,storage,ect.),the ratio of live to deadload,the frequency of occurrence of loading may be reversed,such as in transmission poles,a highuniform prestress would result ultimate st

27、rength 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 berequired,permitting reduction in the number of tendons and anchorages.The necessary flexural strengthmay be p

28、rovided in such cases either by a combination of prestressed tendons and non-prestressedreinforcing bars,or by an adequate number of high-tensile tendons prestredded to level lower than theprestressing force is less,the size of the bottom flange,which is requied mainly to resist the compressionwhen

29、a beam is in the unloaded stage,can be reduced or eliminated altogether.This leads in turn tosignificant simplification and cost reduction in the construction of forms,as well as resulting in structuresthat are mor pleasing esthetically.Furthermore,by relaxing the requirement for low service load te

30、nsion inthe concrete,a significant improvement can be made in the deflection characteristics of abeam.Troublesome upward camber of the member in the unloaded stage fan be avoeded,and the prestressforce selected primarily to produce the desired deflection for a particular loading condition.The behavi

31、orof 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.2KN/m2KN/m英譯漢：荷 載作用在結(jié)構(gòu)上的荷載通常分為恒載或活載。在結(jié)構(gòu)的整個(gè)使用壽命期間，恒載的位置是固定的，大小是不變的。通常，結(jié)構(gòu)的自重是恒載的最重要部分。它可以根據(jù)結(jié)構(gòu)的尺寸和材料的單位重量進(jìn)行精確

32、計(jì)算?；炷恋拿芏仁亲兓?，對(duì)于輕質(zhì)混凝土大約從 90120pcf（1419 ），對(duì)于標(biāo)準(zhǔn)混凝土大 約為 145pcf（23KN/m2）。在計(jì)算結(jié)構(gòu)混凝土的恒載時(shí)，考慮到鋼筋的存在，通常除了混凝土的重量以外還計(jì)入 5pcf（1 ）的增加量。荷載就是諸如居住、雪、風(fēng)、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(huì)變化的。計(jì)算恒載時(shí)工程師的職責(zé)，然而活載通常由當(dāng)?shù)氐?、地區(qū)的或國(guó)家的規(guī)范和準(zhǔn)則所規(guī)定。標(biāo)準(zhǔn)的來源是美國(guó)國(guó)家標(biāo)準(zhǔn)學(xué)會(huì)、美國(guó)州際公路與運(yùn)輸工作者協(xié)會(huì)主辦的刊物，對(duì)于風(fēng)荷載采用美 國(guó)土木工程學(xué)會(huì)風(fēng)力專題委員會(huì)的建議。規(guī)定活載通常包含某些容許的超載，并可

33、以明顯的或隱含地計(jì)入動(dòng)態(tài)影響?；钶d可以采用標(biāo)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(huì)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(shí)際起作用的荷載，它可能很小。例如在計(jì)算結(jié)構(gòu)的長(zhǎng)期撓度時(shí)，重要的是特征荷載，而不是規(guī)定荷載。計(jì)算得到的荷載和規(guī)定活載的和稱為使用荷載，因?yàn)檫@是在結(jié)構(gòu)使用壽命期間可預(yù)料到的要作用在其上的最大荷載。使用荷載乘以一個(gè)系數(shù)就是計(jì)算荷載，即破壞荷載，它就是結(jié)構(gòu)必須恰 好能承受的荷載。強(qiáng)度結(jié)構(gòu)的強(qiáng)度取決于建造它的材料的強(qiáng)度。材料的最小強(qiáng)度都以一些標(biāo)準(zhǔn)的方式來規(guī)定。美國(guó)混凝土學(xué)會(huì)對(duì)混凝土的性質(zhì)及其成分、

34、滿足質(zhì)量要求的拌和、澆筑和養(yǎng)生方法以及試驗(yàn)方法均作了規(guī)定。在同一文件中，作為參考也列入了美國(guó)材料試驗(yàn)協(xié)會(huì)關(guān)于普通鋼筋、預(yù)應(yīng)力鋼筋和混凝 土的標(biāo)準(zhǔn)。強(qiáng)度也取決于結(jié)構(gòu)施工的精心程度。構(gòu)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(dòng)，或者由于混凝土澆筑得不好可能會(huì)造成空洞。工程師工作的重要職責(zé)是要保證應(yīng)有 的施工監(jiān)督。工程師的失職曾經(jīng)不止一次產(chǎn)生了造成巨大損失的后果。結(jié)構(gòu)安全度安全性要求結(jié)構(gòu)的強(qiáng)度足以承受可以預(yù)料到的，作用在結(jié)構(gòu)上的全部荷載。如果強(qiáng)度能夠精確地預(yù)先計(jì)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(qiáng)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(huì)導(dǎo)致在荷載的估算以及

35、分析、設(shè)計(jì)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(chǔ)備。近些年來，工程師們已經(jīng)開始認(rèn)識(shí)到結(jié)構(gòu)安全度這個(gè)問題在實(shí)質(zhì)上就是概率統(tǒng)計(jì)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(diǎn)。荷載和強(qiáng)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(gòu)件在開始破壞時(shí)恰好能承受的計(jì)算荷載。對(duì)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(shí)出現(xiàn)的不確定程度。在預(yù)應(yīng)力混凝土發(fā)展的早期，預(yù)加應(yīng)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(yīng)力。這曾經(jīng)是一種全新的勻質(zhì)材料的概念，認(rèn)為這種材料能夠不開裂并且保持彈性工作狀態(tài)，直至達(dá)到其最大的設(shè)計(jì)荷載。在全部使用荷載作用下，混凝土的極限拉應(yīng)力值為零的這種設(shè)計(jì)，通常稱為之全預(yù)應(yīng)力設(shè)計(jì)；而另一種在全部荷載作用下容許混凝土內(nèi)產(chǎn)生一定大小的拉應(yīng)力的設(shè) 計(jì)方法，稱為部分預(yù)應(yīng)力設(shè)計(jì)。有些場(chǎng)合必須避免任何產(chǎn)生裂縫的危險(xiǎn)，此時(shí)需要采用預(yù)應(yīng)力。這些場(chǎng)合包括：不能產(chǎn)生滲漏的容器或水庫(kù)，必須保證具有最大鋼筋保護(hù)層的水下結(jié)構(gòu)和在強(qiáng)腐蝕環(huán)境中的結(jié)構(gòu)，必須考慮 鋼筋疲勞問題的承受高頻重復(fù)荷載的結(jié)構(gòu)。但是，在許多場(chǎng)合中，只要施加少量的預(yù)應(yīng)力就可以顯著地改善結(jié)構(gòu)的工作性能，降低造價(jià)，或者