橋梁設(shè)計外文翻譯

1、<p>　　附錄 2 外文資料翻譯</p><p><b>　　原文</b></p><p>　　11.7.4 De?ection</p><p>　　11.7.4.1 Dead Load and Creep De?ection</p><p>　　Global vertical de?ections o

2、f segmental box-girder bridges due to the effects of dead load and post-tensioning as well as the long-term effect of creep are normally predicted during the design process by the use of a computer analysis program. The

3、 de?ections are dependent, to a large extent, on the method of construction of the structure, the age of the segments when post-tensioned, and the age of the structure when other loads are applied. It can be expected, t

4、herefore, that the actual de?ect</p><p>　　The de?ections are usually recalculated by the contractor’s engineer, based on the actual construction sequence.</p><p>　　11.7.4.2 Camber Requirements&

5、lt;/p><p>　　The permanent de?ection of the structure after all creep de?ections have occurred, normally 10 to 15 years after construction, may be objectionable from the perspective of riding comfort for t

6、he users or for the con?dence of the general public. Even if there is no structural problem with a span with noticeable sag, it will not inspire public con?dence. For these reasons, a camber will normally be cast into th

7、e structure so that the permanent de?ection of the bridge is nearly zero. It may</p><p>　　11.7.4.3 Global De?ection Due to Live Load</p><p>　　Most design codes have a limit on the allowable

8、 global de?ection of a bridge span due to the effects of live load. The purpose of this limit is to avoid the noticeable vibration for the user and minimize the effects of moving load iMPact. When structures are use

9、d by pedestrians as well as motorists,the limits are further tightened.</p><p>　　11.7.4.4 Local De?ection Due to Live Load</p><p>　　Similar to the limits of global de?ection of bridge spans,

10、 there are also limitations on the de?ection of the local elements of the box-girder cross section. For example, the AASHTO Speci?cations limit the de?ection of cantilever arms due to service live load plus iMPact to &#

11、185;??of the cantilever length,except where there is pedestrian use [1].</p><p>　　11.7.5 Post-Tensioning Layout</p><p>　　11.7.5.1 Exter nal Post-Tensioning</p><p>　　While most con

12、crete bridges cast on falsework or precast beam bridges have utilized post-tensioning in ducts which are fully encased in the concrete section, other innovations have been made in precast segmental construction.Especial

13、ly prevalent in structures constructed using the span-by-span method, post-tensioning has been placed inside the hollow cell of the box girder but not encased in concrete along its length. This is know as external po

14、st-tensioning. External post-tensioning is e</p><p>　　segments. The problems associated with internal tendons are (1) misalignment of the tendons at segment joints, which causes spalling; (2) lack of she

15、athing at segment joints; and (3) tendon pull-through on spans with tight curvature (see Figure 11.39). External prestressing has been used on many projects in Europe, the United States, and Asia and has performed well

16、.</p><p><b>　　11.7.5</b></p><p>　　The provision for the addition of post-tensioning in the future in order to correct unacceptable creep de?ections or to strengthen the structure for

17、 additional dead load, i.e., future wearing surface, is now required by many codes. Of the positive and negative moment post-tensioning, 10% is reasonable. Provisions should be made for access, anchorage attachme

18、nt, and deviation of these additional tendons. External, unbonded tendons are used so that ungrouted ducts in the concrete are not l</p><p>　　11.8 Seismic Considerations</p><p>　　11.8.1 Desi

19、gn Aspects and Design Codes</p><p>　　Due to typical vibration characteristics of bridges, it is generally accepted that under seismic loads,some portion of the structure will be allowed to yield, to dissipat

20、e energy, and to increase the period of vibration of the system. This yielding is usually achieved by either allowing the columns to yield plastically (monolithic deck/superstructure connection), or by providing a yieldi

21、ng or a soft bearing system [6].</p><p>　　The same principles also apply to segmental structures, i.e., the segmental superstructure needs to resist the demands imposed by the substructure. Very few implemen

22、tations of segmental struc-tures are found in seismically active California, where most of the research on earthquake-resistant bridges is conducted in the United States. The Pine Valley Creek Bridge, Parrots Ferry Brid

23、ge, and Norwalk/El Segundo Line Overcrossing, all of them being in California, are examples of segmental structure</p><p>　　Some guidance for the seismic design of segmental structures is provided in the la

24、test edition of the AASHTO Guide Speci?cations for Design and Construction of Segmental Concrete Bridges [2], which now contains a chapter dedicated to seismic design. The guide allows precast-segmental const

25、ruction without reinforcement across the joint, but speci?es the following additional require-</p><p>　　ments for these structures:</p><p>　　? For Seismic Zones C and D [1], either cast-in-place

26、 or epoxied joints are required.</p><p>　　? At least 50% of the prestress force should be provided by internal tendons.</p><p>　　? The internal tendons alone should be able to carry 130% of the

27、 dead load.</p><p>　　For other seismic design and detailing issues, the reader is referred to the design literature provided</p><p>　　by the California Department of Transportation, Caltrans, fo

28、r cast-in-place structures [5-8].</p><p>　　11.8.2 Deck/Superstructure Connection</p><p>　　Regardless of the design approach adopted (ductility through plastic hinging of the column

29、or through bearings), the deck/superstructure connection is a critical element in the seismic resistant system. A brief description of the different possibilities follows.</p><p>　　11.8.2.1 Monolithic Dec

30、k/Superstructure Connection</p><p>　　For the longitudinal direction, plastic hinging will form at the top and bottom of the columns. Since most of the testing has been conducted on cast-in-place joints, thi

31、s continues to be the preferred option for these cases. For short columns and for solid columns, the detailing in this area can be readily adapted from standard Caltrans practice for cast-in-place structures, as shown on

32、 Figure 11.40. The joint area is then essentially detailed so it is no different from that of a fully cast-in-p</p><p>　　11.8.2.2Deck/Superstructure Connection via Bearings</p><p>　　Typically,

33、for spans up to 45 m erected with the span-by-span method, the superstructure will be supported on bearings. For action in the longitudinal direction, elastomeric or isolation bearings are preferred to a ?xed-end

34、/expansion-end arrangement, since these better distribute the load between the bearings. Furthermore, these bearings will increase the period of the structure, which results in an overall lower induced force

35、 level (bene?cial for higher-frequency struc</p><p>　　11.8.2.3 Expansion Hinges</p><p>　　From the seismic point of view, it is desirable to reduce the number of expansion hinges (EH) to a

36、minimum. If EHs are needed, the most bene?cial location from the seismic point of view is at midspan. This can be explained by observing Figure 11.43, where the superstructure bending midspan and for an E

37、H at quarterspan. For the latter, it can be seen that the moment at the face The location of expansion hinges within a span, and its characteristics, depends also on </p><p>　　11.8.2.4 Precast

38、 Segmental Piers</p><p>　　Precast segmental piers are usually hollow cross section to save weight. From research in other areas it can be extrapolated that the precast segments of the pier would be joined

39、by means of unbonded prestressing tendons anchored in the footing. The advantage of unbonded over bonded tendons is that for the former, the prestress force would not increase signi?cantly under high column displace-men

40、t demands, and would therefore not cause inelastic yielding of the strand, which would other-wise lea</p><p>　　The detail of the connection to the superstructure and foundation would require some insight in

41、to the dynamic characteristics of such a connection, which entails joint opening and closing providing that dry joints are used between segments. This effect is similar to footing rocking, which is well known to be ben

42、e?cial to the response of a structure in an earthquake. This is due to the period shift and the damping of the soil. The latter effect is clearly not available to th</p><p>　　11.9 Castin

43、g and Erection</p><p>　　11.9.1 Casting</p><p>　　There are obvious major differences in casting and erection when working with cast-in-place</p><p>　　cantilever in travelers

44、 or in handling precast segments. There are also common features, which must be kept in mind in the design stages to keep the projects simple and thereby economic and ef?cient,such as</p><p>　　? Keeping the

45、length of segments equal and segments straight, even in curved bridges;</p><p>　　? Maintaining constant cross section dimensions as much as possible;</p><p>　　? Minimizing the number of diaphra

46、gms and stiffeners, and avoiding dowels through form-</p><p><b>　　work.</b></p><p>　　11.9.1.1 Cast-in-Place Cantilevers</p><p>　　The conventional form traveler supp

47、orts the weight of the fresh concrete of the new segment by means of longitudinal beams or frames extending out in cantilever from the last segment. These beams are tied down to the previous segment. A counterwe

48、ight is used when launching the traveler forward. The main beams are subjected to some de?ections, which may produce cracks in the joint between the old and new segments. Jacking of the form during casting is sometimes n

49、eeded to avoid these cr</p><p>　　? De?ection of traveler frame under the weight of the concrete segment;</p><p>　　? De?ection of the concrete cantilever arm during construction under the weigh

50、t of segment plus post-tensioning;</p><p>　　? De?ection of cantilever arms after construction and before continuity;</p><p>　　? Short- and long-term de?ections of the continuous structure;</

51、p><p>　　? Short- and long-term pier shortenings and foundation settlements.The sum of the various de?ection values for the successive sections of the deck allows the construc-</p><p>　　tion of a ca

52、mber diagram to be added to the theoretical pro?le of the bridge. A construction camber for setting the elevation of the traveler at each joint must also be developed.</p><p>　　11.9.1.2 Precast Segments&l

53、t;/p><p>　　Opposite to the precast girder concept where the bridge is cut longitudinally in the precast segmental methods, the bridge is cut transversally, each slice being a segment. Segments are cast in a cas

54、ting yard one at a time. Furthermore, the new segment is cast against the previously cast segment so that the faces in contact match perfectly. This is the match-cast principle. When the segments are reassembled at

55、the bridge site, they will take the same relative position with regard to the adj</p><p>　　concrete, but, even so, the strength of the epoxy is not considered in the structural behavior of the joint. The req

56、uired shear capacity is generally provided by shear keys, single or multiple, in com-bination with longitudinal post-tensioning.With the introduction of external post-tensioning, where the tendons are installed in PE du

57、cts,outside the concrete but inside the box girder, the joints are relieved of the traditional requirement of watertightness and are left dry. The introductio</p><p>　　11.9.1.3 Casting Methods</p&

58、gt;<p>　　There are two methods for casting segments. The ?rst one is the long-line method, where all the segments are cast in their correct position on a casting bed that reproduces the span. The second meth

59、od, used most of the time, is the short-line method, where all segments are cast in the same place in a stationary form, and against the previously cast segment. After casting and initial curing, the previously cast seg

60、ment is removed for storage, and the freshly cast segment is moved into plac</p><p>　　11.9.1.4 Geometry Control</p><p>　　A pure translation of each segment between cast and match-cast position

61、results in a straight bridge(Figure 11.45). To obtain a bridge with a vertical curve, the match-cast segment must ?rst be translated and given a rotation ??in the vertical plane (Figure 11.46). Practicall

62、y, the bulkhead is left ?xed and the mold bottom under the conjugate unit adjusted. To obtain a horizontal curvature, the conjugate unit is given a rotation ???in the horizontal plane (see Figur</p>

63、<p>　　11.9.2 Erection</p><p>　　The type of erection equipment depends upon the erection scheme contemplated during the design process; the local conditions, either over water or land; the speed

64、 of erection and overall construction schedule. It falls into three categories, independent lifting equipment such as cranes,deck-mounted lifting equipment such as beam and winch or swivel crane, and launching girder equ

65、ipment.The principle of the method is to erect or cast the pier segment ?rst, then to place typical segments o</p><p>　　weights of 70 tons; the two bridge structures are 27.5 m apart with different elevation

66、s and longi-tudinal slopes. This system is a re?nement of the ?rst type of gantry applied to twin decks with variable geometry.Normally, the balanced cantilever method is used for spans from 60 to 110 m, with a lau

67、nching girder. One full, typical cycle of erection is placing segments, installing and stressing post-tensioning tendons, and launching the truss to its next position. It takes about 7</p><p><b&

68、gt;　　譯文</b></p><p><b>　　11.7.4 撓度</b></p><p>　　11.7.4.1 恒載和徐變</p><p>　　部分箱梁的整體變形是由恒載和后加張力造成的，也包括在設(shè)計過程中用電腦分析軟件正常算出的徐變的長期影響。在很大程度上，撓度取決于結(jié)構(gòu)的構(gòu)造，后張是各部分的齡期和使用荷載作用時結(jié)構(gòu)的齡期。

69、因此，可以認(rèn)為，由于假定的改變，結(jié)構(gòu)的實際撓度會和設(shè)計的不同。在實際結(jié)構(gòu)的基礎(chǔ)上，工程師通常會重新計算撓度。</p><p>　　11.7.4.2 起拱需要</p><p>　　通常10年到15年，所有徐變撓度全部產(chǎn)生后的結(jié)構(gòu)永久變形會令使用者行駛不舒適或者令公眾失去信心。即使結(jié)構(gòu)沒有明顯的缺陷，也不會提升公眾的信心。因此，結(jié)構(gòu)通常會做成拱形，從而是變形接近零。如果在建造過程中必須有一個缺

70、陷，那么忽視起拱就更合適了。</p><p>　　11.7.4.3 活載引起的整體變形</p><p>　　由于活載的影響，大多數(shù)設(shè)計規(guī)范對橋跨的整體變形都有限制。這種限制的目的是避免對使用者的明顯震動和盡量減小活載的影響。對于行人和駕駛員使用的結(jié)構(gòu)，這種限制更嚴(yán)格。</p><p>　　11.7.4.4 活載引起的局部變形</p><p>

71、　　類似于對橋跨整體變形的限制，局部的箱梁橫截面也有變形限制。比如，AASHTO規(guī)范規(guī)定除了行人使用情況外，懸臂梁撓度取決于活載撓度加上橋跨的。</p><p>　　11.7.5 后張布置</p><p>　　11.7.5.1 外部后張</p><p>　　當(dāng)大多數(shù)混凝土橋使用支架建造或者現(xiàn)澆梁橋使用充滿混凝土截面的預(yù)應(yīng)力鋼束是，其他新方法已經(jīng)用于現(xiàn)澆部分結(jié)構(gòu)。特變

72、盛行于逐跨施工法的結(jié)構(gòu)中，后張拉置于箱梁箱室中而不是沿混凝土結(jié)構(gòu)的長度布置。這就是外部后張。外部后張很容易在結(jié)構(gòu)的任何時期檢查，消除內(nèi)部鋼筋的問題和避免在各現(xiàn)澆塊間使用昂貴的環(huán)氧膠黏劑。內(nèi)部鋼筋的問題是在結(jié)合處未對準(zhǔn)引起開裂的鋼筋；在結(jié)合部分缺乏覆蓋物；以一定曲率穿過橋跨的鋼筋(見圖 11.39)。外部預(yù)應(yīng)力已經(jīng)用于歐洲，美國和亞洲的項目，并且用的很好。</p><p>　　圖11.36 內(nèi)部鋼筋的問題</

73、p><p>　　為了糾正不合理的徐變變形和在恒載增加時加固結(jié)構(gòu)而增加的預(yù)應(yīng)力的供應(yīng)，換言之令人討厭的外邊，現(xiàn)在為很多規(guī)章所需求。對后張拉的正面和負(fù)面的彎矩，10%是合理的。規(guī)定應(yīng)該適用于入口，錨固處和增加鋼筋的偏差。外部未粘接鋼筋被使用著，從而保證混凝土中的管道不是開著的。</p><p>　　11.8 關(guān)于地震的考慮</p><p>　　11.8.1 設(shè)計方面和設(shè)計規(guī)

74、范</p><p>　　由于典型的振動特性的橋梁,人們普遍認(rèn)為在地震荷載作用下,一些部分的結(jié)構(gòu)將被允許屈服以消散能量,并提高振動系統(tǒng)的周期。通常情況下,這種屈服通常是柱子產(chǎn)生可塑性屈服(巨大的板或者上部結(jié)構(gòu)連接)或者軟支撐系統(tǒng)屈服達(dá)到的[6]。</p><p>　　同樣的原理也適用于節(jié)段性結(jié)構(gòu),即分段上層建筑的需要承擔(dān)子結(jié)構(gòu)產(chǎn)生的需求。很少在地震活躍的加利福利亞發(fā)現(xiàn)節(jié)段性結(jié)構(gòu)，那兒有美國大

75、多數(shù)的抗震研究。節(jié)段性結(jié)構(gòu)的例子華彬溪橋,鸚鵡渡輪等都在加利福利亞，然而，這些橋都被適當(dāng)?shù)牟糠旨訌姟?lt;/p><p>　　一些節(jié)段性結(jié)構(gòu)抗震設(shè)計的知道提供在最新版本的AASHTO的設(shè)計與施工節(jié)段性混凝土橋梁規(guī)范[2]中,該規(guī)范有一章致力于抗震設(shè)計。該規(guī)范允許裝配式預(yù)制結(jié)構(gòu)不需要在結(jié)合處加強，但對這些結(jié)構(gòu)指定的下列附加的要求：</p><p>　　對于地震帶C和D，必須使用就地澆筑或者環(huán)氧粘

76、接劑。</p><p>　　內(nèi)部鋼筋至少要有50%的預(yù)應(yīng)力。</p><p>　　內(nèi)部鋼筋應(yīng)該能夠承擔(dān)130%的恒載。</p><p>　　對于其他抗震設(shè)計和細(xì)化問題,讀者應(yīng)參考加州交通部提供的現(xiàn)澆結(jié)構(gòu)的設(shè)計資料[5-8]。</p><p>　　11.8.2 板和上部結(jié)構(gòu)連接</p><p>　　無論什么設(shè)計方法(通過

77、鉸接或通過軸承)，板/上部結(jié)構(gòu)連接在抗震中是一個關(guān)鍵要素。下面的是不同可能的一個簡短描述。</p><p>　　11.8.2.1 整體板和上部結(jié)構(gòu)連接</p><p>　　在縱向，柱的頂部和底部將形成塑性鉸。由于大多數(shù)的測試都是在就地澆筑的連接處進行的，在這些情況下這都是首選。對短柱和實心柱,在這一地區(qū)的詳細(xì)標(biāo)準(zhǔn)可以很容易從加利福利亞運輸部對于現(xiàn)澆結(jié)構(gòu)的實驗中實現(xiàn)，如圖11.40所示。然后

78、聯(lián)合區(qū)從本質(zhì)詳細(xì)情況是和現(xiàn)澆橋相同的。特別是一個加利福利亞運輸部對一個墩的加固可以用預(yù)應(yīng)力鋼絞線詳細(xì)表述,如下所示。大跨度和高大的圓柱、空心柱部分會更合適。在這種情況下,應(yīng)該小心地主柱界限,并根據(jù)文獻(xiàn)[3或7]提供結(jié)合處的剪力。</p><p>　　圖11.40 板/墩的現(xiàn)澆接頭</p><p>　　圖11.41 預(yù)應(yīng)力現(xiàn)澆墩</p><p>　　11.8.2.2

79、板/上部結(jié)構(gòu)通過軸承連接</p><p>　　通常情況下對于跨越到45米逐跨施工法，上層建筑將會通過軸承支撐。在縱向上,橡膠或隔震支座優(yōu)先安排桿的一端/或者膨脹的一端,因為這些更好的分配軸承間的荷載。此外,這些軸承將增加結(jié)構(gòu)的齡期,從而在整體上減小感應(yīng)力(對高頻結(jié)構(gòu)有益),隔離軸承也會提供一些結(jié)構(gòu)阻尼。</p><p>　　在橫方向，軸承也許能通過剪切變形轉(zhuǎn)移上部結(jié)構(gòu)間的荷載；然而，在某些

80、不肯能的情況下，能如圖11.42所示的提供剪力鍵。應(yīng)該指出的是,地震高發(fā)區(qū),對于有高墩和軟弱下部結(jié)構(gòu)的建筑，軸承更加為人所需，整體板和上部結(jié)構(gòu)連接是必需的。</p><p>　　對于結(jié)構(gòu)上加軸承的方法，上部結(jié)構(gòu)的力可以很容易控制，因為軸承的要求從分析中滿足，他們就能用于上部結(jié)構(gòu)和下部結(jié)構(gòu)。上部結(jié)構(gòu)必須抵抗最后的合力(使用適當(dāng)?shù)臏p力因素),而在下部結(jié)構(gòu)中可以產(chǎn)生屈服。</p><p>　　圖

81、11.42 板/頓軸承連接</p><p>　　11.8.2.3 膨脹鉸鏈</p><p>　　從地震的觀點來看,我們希望將膨脹鉸鏈(EH)的數(shù)量降到最低。如果EH是必需的,從地震的觀點看，最有利的位置是中跨。這可以通過觀察圖11.43來解釋，上部結(jié)構(gòu)彎曲時,造成柱的塑料鏈接(Mp),已經(jīng)繪制了中跨有塑性鉸鏈和四分之一跨有塑性鉸鏈的情況。 對于后者,我們可以看到柱面在四分之三Mp范圍變化，

82、但是中跨有鉸鏈時，只能在二分之一范圍變化。</p><p>　　膨脹鉸鏈在一個跨度的位置及其特性,也依賴于基礎(chǔ)的剛度和上部結(jié)構(gòu)到墩的連接類型。表11.1提出了選擇膨脹鉸鏈位置的一般準(zhǔn)則。</p><p>　　圖11.43 地震中中跨和四分之一跨有鉸鏈的縱向上部結(jié)構(gòu)</p><p>　　表11.1 部分橋梁中膨脹鉸鏈的位置</p><p>　　

83、11.8.2.4 預(yù)制節(jié)段墩</p><p>　　預(yù)制節(jié)段性橋墩通常挖孔減輕重量。從其他方面的研究推斷墩的預(yù)制節(jié)段可以通過未粘接的錨固的預(yù)應(yīng)力鋼筋連接。粘接鋼筋上未粘接的優(yōu)勢在于以前，預(yù)應(yīng)力不會再高柱位移要求中顯著增長，因此不會引起導(dǎo)致預(yù)應(yīng)力損失的非彈性屈服。</p><p>　　上部結(jié)構(gòu)和基礎(chǔ)連接的細(xì)節(jié)需要洞察這個連接的動態(tài)特點，這就需要接頭的開端和結(jié)尾有干燥的接頭用于各部分。 這個影響

84、類似于從所周知的有利于回應(yīng)地震中結(jié)構(gòu)的基礎(chǔ)搖擺。后者影響顯然不適用于現(xiàn)澆柱,但適用于彎矩轉(zhuǎn)換。</p><p>　　如果上部柱段是設(shè)計用來連接到上部結(jié)構(gòu)，加固屈服是有望的。在這種情況下，期望的塑性鉸鏈長度應(yīng)該用空間關(guān)系[3,5]詳細(xì)延展。</p><p>　　11.9 澆筑和安裝</p><p><b>　　11.9.1 澆筑</b></

85、p><p>　　在運輸現(xiàn)澆構(gòu)件和處理現(xiàn)澆節(jié)段時，澆筑和安裝有明顯的不同。但也有共同特點，就是必須記住設(shè)計階段應(yīng)保證方案簡單，經(jīng)濟和效率。比如：</p><p>　　·保持各段的長度相等和直，曲線橋也如此</p><p>　　·始終盡量保證橫截面尺寸</p><p>　　·盡量減少橫隔板和加勁肋的數(shù)量，并且模板中出現(xiàn)銷

86、釘</p><p>　　11.9.1.1 現(xiàn)澆懸臂梁</p><p><b>　　傳統(tǒng)起重機</b></p><p>　　傳統(tǒng)形式的起重機通過縱梁或者最后一段外伸框架的形式支撐新鮮混凝土。這些梁連接以前的片段。有個平衡力推動起重機向前。主梁受到可能在新老部分連接處產(chǎn)生裂縫的變形。灌注期間需要頂起模板來避免這些裂縫。起重機的重量大概是一個節(jié)段重量

87、的60%。建造的比例通常是一個一個起重機一個節(jié)段。預(yù)應(yīng)力混凝土固定塊用于加速后張法施工。在寒冷天氣，可以通過各種加熱裝置來加速固化。</p><p><b>　　結(jié)構(gòu)曲面控制</b></p><p>　　最關(guān)鍵的實際問題是現(xiàn)澆施工撓度控制。施工前后有五類撓度：</p><p>　　·混凝土節(jié)段重量下起重機支架的撓度</p>

88、<p>　　·建造時施加后張節(jié)段的重量下懸臂梁的撓度</p><p>　　·懸臂梁建造后到連接前得撓度</p><p>　　·連續(xù)構(gòu)建的短期和長期撓度</p><p>　　·長期和短期墩縮短和基礎(chǔ)沉降</p><p>　　板的連續(xù)截面的各種撓度的總和允許給橋假想外形加一個拱形圖。在每個連接

89、處設(shè)置起重機標(biāo)高也必須得到發(fā)張。</p><p>　　11.9.1.2 預(yù)制塊</p><p>　　橋縱向分塊來預(yù)制大梁的觀念相反的，橋被橫向分割，每一塊是一個節(jié)段。各節(jié)段一塊一塊的在澆筑場地澆筑。而且新階段是引著前面節(jié)段澆筑的，以便兩面能更好的連接。這就是配合澆筑原則。當(dāng)各部分在橋址重新組裝是，他們會依照和澆筑時相同的位置關(guān)系。節(jié)段的集合精確性是絕對的重點，并且充分的測量方法必須用來保證

90、接下來的幾何關(guān)系。</p><p>　　是實施粘接，達(dá)到用環(huán)氧樹脂覆蓋相接節(jié)段一面或者兩面的前提。環(huán)氧樹脂在組裝節(jié)段時充當(dāng)潤滑劑，并且它保證結(jié)構(gòu)完成時連接處的水密性。完全水密性是內(nèi)部鋼筋腐蝕防護必須的。環(huán)氧樹脂材料的抗拉強度比鋼筋的大，但即使如此，環(huán)氧樹脂的抗拉強度在連接處結(jié)構(gòu)行為也不考慮。所需的抗剪能力基本由剪力鍵提供。</p><p>　　通過外部后張的采用，鋼筋安裝在聚乙烯管內(nèi)部，混

91、凝土外面和箱梁內(nèi)部，連接處達(dá)到傳統(tǒng)的保證水密性的要求?；炷羶?nèi)干燥連接的外部鋼筋的采用打打提高了現(xiàn)澆的效果。</p><p>　　11.9.1.3 澆筑方法</p><p>　　有兩種澆筑節(jié)段的方法。第一種是長線法，即在復(fù)制跨度的床位上按正確的位置澆筑所有的節(jié)段。第二種方法是短線法，大多數(shù)時間用這種方法，即所有的節(jié)段在一個靜止的地方挨著前一個節(jié)段澆筑。澆筑和初步加工后，前面的節(jié)段移到倉庫，

92、而新的節(jié)段移到那個位置。(見圖11.44)</p><p>　　11.9.1.4 幾何控制</p><p>　　筑和配合澆筑位置簡單平移造就一座直橋(見圖11.45)。要讓橋獲得垂直的弧度，配合澆筑在垂直方向平移并有一個轉(zhuǎn)動角a(見圖11.46)。實際上在隔離壁是保持直的。要獲得水平彎曲，連接單元在水平面有一個轉(zhuǎn)角b(見圖11.47)。要獲得不同的超高，連接單元要繞頂板中建的水平軸線轉(zhuǎn)動(

93、見圖11.48)。</p><p>　　所有的這些連接單元的調(diào)整總結(jié)為獲得橋的幾何方面的期望。</p><p>　　圖11.44 典型短線預(yù)制操作</p><p>　　圖11.47 平曲線橋</p><p>　　圖11.48 帶超高的橋</p><p><b>　　11.9.2 安裝</b><

94、;/p><p>　　安裝設(shè)備的類型取決于設(shè)計節(jié)段的安裝方案構(gòu)思，當(dāng)?shù)厮懬闆r，安安裝速度和總體建造安排。分成三部分，獨立的其中設(shè)備，比如吊車；旋轉(zhuǎn)導(dǎo)纜器，比如卷揚機；梁拽進裝置。</p><p>　　11.9.2.1 懸臂平衡法</p><p>　　這種方法的原則是先豎起或澆筑橋墩節(jié)段，然后從墩的一邊一個一個放置典型節(jié)段，或者從兩邊同時進行。每個新的預(yù)制節(jié)段都通過臨時的

95、齒眼和前面的一個連接，知道懸臂鋼筋安裝和受力。懸臂端連接處的閉合施工到位并且連續(xù)鋼筋安裝和受力。</p><p>　　為了實施建造計劃，各節(jié)段必須在適當(dāng)?shù)奈恢门e起和安裝。最簡單的方法是用起重機，不管是在陸地上還是駁船上。很多橋當(dāng)還沒有特別的起重設(shè)備時都是用起重機建立的。這種方法很慢。通常一天放置兩到四段。這種方法用于相對較短的橋。另一種好的方法是在最后個豎立節(jié)段使用卷揚機。卷揚機安裝在適合節(jié)段的梁上。卷揚機從下面

96、的貨車或者駁船上直接拾起節(jié)段。放置好節(jié)段后，梁和卷揚機系統(tǒng)向前移動來拾起下一個節(jié)段。通常梁卷揚機系統(tǒng)放置在每個懸臂端。這種方法同樣很慢，但是，這不需要就地使用又貴又重的卷揚機，特別是在節(jié)段很重的時候。</p><p>　　當(dāng)橋很長但建造時間安排很短時，最好的方法是用頂推法，該法能充分利用預(yù)制節(jié)段從而加快建造速度。</p><p>　　這種建造方法有兩種基本的自頂推構(gòu)臺。第一種類型是一種比典

97、型跨度稍微長一點的構(gòu)臺(見圖11.49)。懸臂施工過程中，中心支腿依賴于橋墩而后部支腿依賴于前面豎起跨的懸臂端，該支腿必須承受相對運動。在拽進前，前跨必須保證連續(xù)。然后，中心支腿想懸臂端移動，該支腿必須承受構(gòu)架和橋墩節(jié)段重量的和。這個階段控制著構(gòu)臺的設(shè)計，必須保證盡量輕。</p><p>　　第二種類型構(gòu)臺有典型跨兩倍的長度(見圖11.50)。支腿在建造和下一跨推進期間的反應(yīng)通常作用在橋墩上，所以在懸臂端沒有集中

98、的建造荷載。每個建造周期由所有類型懸臂節(jié)段和下一個懸臂段的安裝，同時不改變構(gòu)架的位置。</p><p>　　構(gòu)臺類型可以根據(jù)橫截面劃分：帶有入口型支腿的簡單構(gòu)架，帶有跨越構(gòu)架的雙推進構(gòu)臺。在夏威夷橋的雙線箱梁是通過兩條平行線建造的，但又有獨立的構(gòu)架(見圖11.51)，典型跨度是100.0米，節(jié)段重量70噸；兩座橋結(jié)構(gòu)以不同的高度和縱坡相距27.5米。這個體系是第一種構(gòu)臺的改良。</p><p&