橋梁設計外文翻譯橋梁結(jié)構(gòu)及其設計原理

1、橋梁結(jié)構(gòu)及其設計原理對于橋梁來說，從采用裝配式標準構(gòu)件的小跨徑結(jié)構(gòu)到凈跨徑接近于1000英尺的斜拉梁和連續(xù)箱梁，已經(jīng)證實了預應力混凝土工藝上的方便性，經(jīng)濟上的競爭性，審美上的卓越性。目前，幾乎所有的混凝土橋，甚至跨度較小的橋都是預應力結(jié)構(gòu)的。人們可以采用預制的，現(xiàn)澆式的，或者混合式的施工方法。先張法和后張法預加應力通常在同一個工程中使用。橋梁結(jié)構(gòu)在建橋之前，設計工程師要考慮各種因素，例如最適合場地的橋梁形式（懸索橋，梁橋或拱橋），所用的材料，橋梁所承受的荷載類別，環(huán)境因素例如強風或震動，和最合適的施工方法。橋梁施工中最普遍的施工形式是梁?？缭跍锨系囊粔K板就是一座簡單的梁橋，荷載作用由材料的彎

2、曲應力承擔。一個簡支梁只有兩個支座，任何一個向下的荷載作用均會使梁的底面受拉，頂面受壓。這些應力對支撐荷載起到足夠的力偶矩，即彎矩。根據(jù)靜力學原理，保持梁豎直的反力必定等于將其下壓的荷載作用力。因此，對于一種已知量的材料，厚梁比薄梁產(chǎn)生更大的杠桿作用，所以除了最小的梁-，梁都應作成工字形梁，t梁或中空的箱梁。在簡支梁中，最大彎矩值出現(xiàn)在跨中，并向兩端遞減至0。如果想要建成一座外觀修長，形態(tài)優(yōu)美的橋梁，這一特點就會造成很多不便。懸臂和懸跨通過“鉸”斷開，鉸點把彎矩分成兩部分，一部分在跨中區(qū)域下垂，一部分在內(nèi)力作用下上部受拉，下部受壓。如有必要，可以將副彎矩配置到承擔一般以上的總力矩，以便更好的滿

3、足優(yōu)美的曲面，倫敦的滑鐵盧大橋就是一個例子。英格蘭西部布里斯托附近的埃文毛斯大橋與之相似，但它是一座沒有鉸接的連續(xù)梁橋。這種橋已經(jīng)很普遍，盡管一個橋墩下沉或許會使梁彎曲并增加應力。懸索橋可有較大跨徑，但是有一個嚴重的缺陷，那就是它很柔韌，而且交通荷載可以產(chǎn)生大幅度撓度，尤其當荷載作用在近1/4跨徑時。由于這個原因，幾乎一直都用加勁梁或箱梁來加強纜索。即使這樣，這種形式幾乎不用于鐵路橋上，因為火車比較重，而且它們的荷載要比公路荷載更集中。但是懸索橋解決了最大跨徑的問題，因為作纜索的鋼繩成本廉價，而且其強度比適宜于做梁結(jié)構(gòu)的鋼要大的多。目前中等跨度的橋梁一般均采用一種折中辦法是斜拉橋，這種橋裝有拉

4、索，將搭棧和橋面接了起來。橋梁結(jié)構(gòu)中，拱橋可能被看作是翻過來的懸索橋。雖然拱所施加的是推力，不是拉力，但和懸索橋一樣，拱施加在橋墩（端支撐）的力比簡支梁大的多，這使地面承受一部分力，因此在結(jié)構(gòu)中節(jié)省了材料，但是需要更可靠的基礎。因為這種結(jié)構(gòu)可以使用普通等級鋼，并且將其作成相當大的拱肋或大梁，以保證壓曲抗力，所以撓度問題不大。結(jié)構(gòu)理論與設計（1）橋梁的結(jié)構(gòu)理論中對橋面鋪裝層的計算分析論述接近于零，現(xiàn)在規(guī)范中只給定了厚度的推薦值7，工程界一直在各等級的公路中運用了幾十年。隨著交通量的增大，現(xiàn)在鋪裝與重型、超重型汽車的增多和車速的增快已不相適應。橋面鋪裝層承受車輪荷載的沖擊，橋面鋪裝部分或全部結(jié)構(gòu)的

5、變形，因此橋面鋪裝是一個受力復雜的動力體系，各種形式的主梁及鋪裝本身的構(gòu)造均影響其應力的分布。（2）現(xiàn)行橋規(guī)第3.2.2條規(guī)定：。如無精確的計算方法，箱型梁也可參照t形橋進行處理的【9】。從從多箱梁的設計來看，大部分設計者對箱梁構(gòu)件時按t形梁進行處理的。而箱梁的實際受力雖有近于t梁的一面，又有異于t梁的一面，對于連續(xù)箱梁差別更大。尤其是近年來箱梁的橋面越來越寬，橋跨與橋?qū)捴仍絹碓叫?，箱梁仍按t梁那種長細桿件設計配筋，越來越不適宜了，導致t梁設計的箱梁骨架鋼筋在實際受力狀態(tài)下難以像t梁主筋那樣發(fā)揮應有的作用。所以，設計的假設狀態(tài)與箱梁的實際受力狀態(tài)不一致。（3）隨著材料工業(yè)的發(fā)展，橋梁承重結(jié)構(gòu)

6、的改進，使橋梁主梁能以教柔的結(jié)構(gòu)達到受力的要求，高等級公路大跨橋梁的橫向越來越寬。特別在設計計算中側(cè)重于主梁縱向的計算分析，對橋梁橫向剛度重視不足，橫向構(gòu)造措施不力使橋面鋪裝分擔了過多的次內(nèi)力。（4）對于連續(xù)橋梁、拱橋及懸臂橋等橋型構(gòu)造，由于荷載的作用而產(chǎn)生負彎矩或拉力，使橋面鋪裝層受到拉力的總用而產(chǎn)生負彎矩區(qū)裂縫，從而造成橋面鋪裝的損壞。（5）在對高速公路進行交通組織管理中，由于車道功能的不同，人為強制地使橋梁構(gòu)造運營始終處于偏載承擔了比超車道高得多（量值可達三至四倍）的運營應力水平，因此加快了主車道鋪裝層的疲勞。特別是隨著私營運輸業(yè)的發(fā)展，貨運業(yè)主為追求短期經(jīng)濟利益，通過改變車廂構(gòu)造如加長

7、車廂和加高車軸彈簧等使汽車的載重、軸重及輪載成倍增加。這些年車輛對鋪裝層具有嚴重的毀壞作用，并使橋梁結(jié)構(gòu)局部超載，加快了主車道鋪裝層的病害發(fā)展。因此，在設計中應根據(jù)運營中荷載的實際分布情況，在明確了橋梁結(jié)構(gòu)受力的基礎上，對橋面鋪裝成進行受力計算。一般來說，在美國公路橋梁通常滿足美國洲際公路及運輸工作者協(xié)會規(guī)范的荷載、設計和施工要求。鐵路中使用。橋梁的設計和施工以美國鐵道工程師協(xié)會的鐵路工程手冊的規(guī)定為基準。對于人行立交橋和用于其他目的的橋梁的設計要求，可由當?shù)鼗騾^(qū)域性的規(guī)范和規(guī)程確立。美國混凝土協(xié)會規(guī)范的條款常常為參考文獻所采納，而且在大多數(shù)情況中作為其他指導性文件的規(guī)范規(guī)定。在歐洲，以及近年

8、來在西半球，這些要求導致了分段施工的大跨度預應力混凝土箱型梁橋的發(fā)展。在這種橋梁的典型施工中，往往應用滑模技術就地澆注橋墩。然后在橋墩頂部澆注“榔頭”形箱梁節(jié)段，進而在每一個方向用平衡懸臂梁法進行施工。施工或者采用現(xiàn)澆節(jié)段，或者采用預制節(jié)段向前推進，每一節(jié)段都與前面已經(jīng)完成的結(jié)構(gòu)用后張法連接。最后，待跨中閉合的現(xiàn)澆接頭作好以后，再用后張法張拉整個結(jié)構(gòu)以達到完全的整體性。bridges structure theory and designpretested concrete has proved to be technically advantageous, economically comp

9、etitive, and esthetically superior for bridges, from very short span structures using precast standard components to cable-stayed girders and continuous box girders with clear spans of nearly 1000ft.nearly all concrete bridges, even those of relatively short span, are now priestesses. precutting, ca

10、st-in-place construction, or a combination of the two methods may be used. both pre-tensioning and post-tensioning are employed, often on the same project.bridge structurebefore a bridge is built the engineers designing it will have to consider various points such as the best type of bridge for the

11、site-suspension, beam or arch the materials to be used, the sort of loads it must carry, environmental conditions such as high winds or earthquakes, and the most suitable construction methods.the commonest form of bridge construction is the beam .a plank placed across a ditch is a simple beam bridge

12、, and the action of the load is resisted by bending stresses in the material. for a simple supported beam, which are rests on two supports only? any load acting downwards puts the bottom part of the beam in tension and the top part in compression. these stresses develop sufficient lee rage (the tech

13、nical term is bending moment) to support the load. the forces keeping the beam straight must, by a fundamental law of statics, equal the load tending to fold it up. therefore for a given amount of material, a deep beam will give more leverage than a thin one, and material near the top and bottom fac

14、es works to better effect than material in the middle. so for anything more than the smallest bridges, the beam will be fashioned into i-or t-sections or into a hollow box section.in a simple supported beam the maximum bending moment occurs at the centre, diminishing to zero at the ends. this is inc

15、onvenient if a slender, graceful appearance is wanted. the cantilever and suspended span arrangement has the cantilevers and suspended spans separated by hinges , which divides the bending moment into two parts, sagging as before in the midspan regions and hogging (tension at the top ,compression at

16、 the bottom ) over the inner supports . the if desired, the hogging may be arranged to take more than half the total moment, which fits well with a graceful curved profile-waterloo bridge in london is an example . the avon mouth bridge near bristol in western england is similar, but is a continuous

17、girder bridge with no hinges. this is now common practice, despite the fact that if one pier sinks slightly this bends the beam and adds to the stresses.the suspension bridge can cover a vast span but has serious drawback: it is very flexible and traffic loading may produce a large deflection, parti

18、cularly when it acts near the quarter point of the span. for this reason a stiffening beam or box girder is almost always provided to supplement the cables. even so, this type is rarely used for railway bridges as trains are heavier, and their loading more concentrated, than road traffic. sustention

19、 bridges are, however, the solution for the longest spans, since wire for the cables can be produced cheaply with much greater strength than the steel suitable for beam construction. a compromise which is now popular for intermediate spans is the cable stayed bridge which has stays joining the tower

20、s and deck.in bridge construction the arch could be considered to be a sustention bridge turned upside down. like the sustention bridge the arch puts a much larger force on the abutments (the end supports) than a simple beam does, although it pushes rather than pulls. this makes the ground do part o

21、f the work, thereby saving material in the structure, but it requires reliable foundations. flexibility is less of a problem in this type of construction because ordinary grade steel is used and built up into a relatively large arched rib or girder to ensure resistance to buckling.structure theory a

22、nd design(1)bridge structure holds tier of calculation with in theory to bridge floor shop , gives the recommendation value having fixed thickness7 , the project boundary has applied several tens year to every grade highway always middle . already is out of keeping with the fact the volume of traffi

23、c enhancing, active shop hold increasing with the heavy type, increasing by and speed of a vehicle surpassing the heavy type automobile with quickly. the bridge floor lays the impingement pretending bear carriage wheel load tier directly, the bridge floor lays the deformation having loaded the part

24、or all participation betokening girder construction, bridge floor shop pretends to be a main beam accepting the strenuously complicated driving force system, various form and the distribution laying the structure pretending to be self affect whose strain equally therefore.（2）bridges currently in eff

25、ect:.the regulation also may consult the t shape beam if there being accurate reckoning ;the box shape beam handle 9 .judging from a lot of box beams design , the most designer is to handle to box beam component be in progress according to t shape beam . box beam reality accepts but a force though h

26、aving one aspect bordering on the t beam, one aspect having being different from the t beam, the with regard to continuous box beam difference are bigger. especially box beam bridge floor is in recent years more and more broad ,ratio of bay and bridge width is more and more small , does that long th

27、in member still design the box beam according to t beam matching tendon , push down with regard to more and more no proper , leading to ? the box beam framework reinforced bar that the beam designs is difficult to bring the due effect into play like t beam host tendon under actual strenuously circum

28、 stances .therefore, the hypothesis states designing that box beam reality accept force state disaccords.（3）with material, development of industry, architectural bearing bridge improvement, make bridge host liang neng more and more broad reaching the request accepting a force, big advanced level hig

29、hway transverse direction across bridge with softer structure. stiffness attaches importance to bridge transverse direction deficiency , disadvantageous messenger of transverse direction structure measure bridge floor shop pretends to have shared more than the correct or required number time of inte

30、rnal forces especially in the analysis designing that the middle secretly scheming against puts particular emphasis on the calculation in main beam direction .（4）to bridge type structure such as continuous beam bridge , arch bridge and cantilever beam bridge , effect because of load but produce nega

31、tive curved regulation or pulling force , make the bridge floor lay the effect pretending to accept pulling force tier but produce the breakdown shouldering the curved regulation area rift , bringing about bridge floor shop dress thereby .（5）manages middle in the organization who carries out traffic

32、 on the express highway , different since the lane is functional , person has been to compel a field to make bridge structure be in motion and do business all the time in insisting to be loaded with state , has made host lane shop horizontal holding the strain having born ratio overtaking daogaodedu

33、o (magnitude but having amounted to three till quitter) to be in motion and do business with , has accelerated the host lane therefore laying the strain installing a tier .especially with the development of private carrying trade , the freight proprietor is to run after short-term economy benefit ,

34、the load , axle load on rail and wheel by changing compartment structure if lengthening a compartment and heightening axle spring and so on uses an automobile are loaded with to increase by several times . these vehicles are had to shop dress tire destroying an effect gravely, are make bridge struct

35、ure part overload and, have accelerated the host lane shop the disease installing a tier development. therefore, should distribute condition according to the reality that the vehicle loads in being in motion and doing business in design, pretend to be in progress tier being secretly schemed against by the force on the basis having made clear that bridge structure accepts a force, to bridge floor shop.in the unit states, highway bri