土木工程外文翻譯---抗側向荷載的結構體系

1、<p>　　Structural Systems to resist lateral loads</p><p>　　Commonly Used structural Systems</p><p>　　With loads measured in tens of thousands kips, there is little room in the design of high

2、-rise buildings for excessively complex thoughts. Indeed, the better high-rise buildings carry the universal traits of simplicity of thought and clarity of expression.</p><p>　　It does not follow that there

3、is no room for grand thoughts. Indeed, it is with such grand thoughts that the new family of high-rise buildings has evolved. Perhaps more important, the new concepts of but a few years ago have become commonplace in tod

4、ay’ s technology.</p><p>　　Omitting some concepts that are related strictly to the materials of construction, the most commonly used structural systems used in high-rise buildings can be categorized as follo

5、ws:</p><p>　　Moment-resisting frames.</p><p>　　Braced frames, including eccentrically braced frames.</p><p>　　Shear walls, including steel plate shear walls.</p><p>　　T

6、ube-in-tube structures.</p><p>　　Tube-in-tube structures.</p><p>　　Core-interactive structures.</p><p>　　Cellular or bundled-tube systems.</p><p>　　Particularly with th

7、e recent trend toward more complex forms, but in response also to the need for increased stiffness to resist the forces from wind and earthquake, most high-rise buildings have structural systems built up of combinations

8、of frames, braced bents, shear walls, and related systems. Further, for the taller buildings, the majorities are composed of interactive elements in three-dimensional arrays.</p><p>　　The method of combining

9、 these elements is the very essence of the design process for high-rise buildings. These combinations need evolve in response to environmental, functional, and cost considerations so as to provide efficient structures th

10、at provoke the architectural development to new heights. This is not to say that imaginative structural design can create great architecture. To the contrary, many examples of fine architecture have been created with onl

11、y moderate support from the structura</p><p>　　While comprehensive discussions of these seven systems are generally available in the literature, further discussion is warranted here .The essence of the desig

12、n process is distributed throughout the discussion.</p><p>　　Moment-Resisting Frames</p><p>　　Perhaps the most commonly used system in low-to medium-rise buildings, the moment-resisting frame, i

13、s characterized by linear horizontal and vertical members connected essentially rigidly at their joints. Such frames are used as a stand-alone system or in combination with other systems so as to provide the needed resis

14、tance to horizontal loads. In the taller of high-rise buildings, the system is likely to be found inappropriate for a stand-alone system, this because of the difficulty in mobilizi</p><p>　　Analysis can be a

15、ccomplished by STRESS, STRUDL, or a host of other appropriate computer programs; analysis by the so-called portal method of the cantilever method has no place in today’s technology.</p><p>　　Because of the i

16、ntrinsic flexibility of the column/girder intersection, and because preliminary designs should aim to highlight weaknesses of systems, it is not unusual to use center-to-center dimensions for the frame in the preliminary

17、 analysis. Of course, in the latter phases of design, a realistic appraisal in-joint deformation is essential.</p><p>　　Braced Frames</p><p>　　The braced frame, intrinsically stiffer than the mo

18、ment –resisting frame, finds also greater application to higher-rise buildings. The system is characterized by linear horizontal, vertical, and diagonal members, connected simply or rigidly at their joints. It is used co

19、mmonly in conjunction with other systems for taller buildings and as a stand-alone system in low-to medium-rise buildings.</p><p>　　While the use of structural steel in braced frames is common, concrete fram

20、es are more likely to be of the larger-scale variety.</p><p>　　Of special interest in areas of high seismicity is the use of the eccentric braced frame.</p><p>　　Again, analysis can be by STRESS

21、, STRUDL, or any one of a series of two –or three dimensional analysis computer programs. And again, center-to-center dimensions are used commonly in the preliminary analysis.</p><p>　　Shear walls</p>

22、<p>　　The shear wall is yet another step forward along a progression of ever-stiffer structural systems. The system is characterized by relatively thin, generally (but not always) concrete elements that provide bot

23、h structural strength and separation between building functions.</p><p>　　In high-rise buildings, shear wall systems tend to have a relatively high aspect ratio, that is, their height tends to be large compa

24、red to their width. Lacking tension in the foundation system, any structural element is limited in its ability to resist overturning moment by the width of the system and by the gravity load supported by the element. Lim

25、ited to a narrow overturning, One obvious use of the system, which does have the needed width, is in the exterior walls of building, where the requ</p><p>　　Structural steel shear walls, generally stiffened

26、against buckling by a concrete overlay, have found application where shear loads are high. The system, intrinsically more economical than steel bracing, is particularly effective in carrying shear loads down through the

27、taller floors in the areas immediately above grade. The sys tem has the further advantage of having high ductility a feature of particular importance in areas of high seismicity.</p><p>　　The analysis of she

28、ar wall systems is made complex because of the inevitable presence of large openings through these walls. Preliminary analysis can be by truss-analogy, by the finite element method, or by making use of a proprietary comp

29、uter program designed to consider the interaction, or coupling, of shear walls.</p><p>　　Framed or Braced Tubes</p><p>　　The concept of the framed or braced or braced tube erupted into the techn

30、ology with the IBM Building in Pittsburgh, but was followed immediately with the twin 110-story towers of the World Trade Center, New York and a number of other buildings .The system is characterized by three –dimensiona

31、l frames, braced frames, or shear walls, forming a closed surface more or less cylindrical in nature, but of nearly any plan configuration. Because those columns that resist lateral forces are placed as far </p>&

32、lt;p>　　The analysis of tubular structures is done using three-dimensional concepts, or by two- dimensional analogy, where possible, whichever method is used, it must be capable of accounting for the effects of shear l

33、ag.</p><p>　　The presence of shear lag, detected first in aircraft structures, is a serious limitation in the stiffness of framed tubes. The concept has limited recent applications of framed tubes to the she

34、ar of 60 stories. Designers have developed various techniques for reducing the effects of shear lag, most noticeably the use of belt trusses. This system finds application in buildings perhaps 40stories and higher. Howev

35、er, except for possible aesthetic considerations, belt trusses interfere with nearly e</p><p>　　Tube-in-Tube Structures</p><p>　　The tubular framing system mobilizes every column in the exterior

36、 wall in resisting over-turning and shearing forces. The term‘tube-in-tube’is largely self-explanatory in that a second ring of columns, the ring surrounding the central service core of the building, is used as an inner

37、framed or braced tube. The purpose of the second tube is to increase resistance to over turning and to increase lateral stiffness. The tubes need not be of the same character; that is, one tube could be framed, whil</

38、p><p>　　In considering this system, is important to understand clearly the difference between the shear and the flexural components of deflection, the terms being taken from beam analogy. In a framed tube, the

39、shear component of deflection is associated with the bending deformation of columns and girders (i.e, the webs of the framed tube) while the flexural component is associated with the axial shortening and lengthening of c

40、olumns (i.e, the flanges of the framed tube). In a braced tube, the shear comp</p><p>　　Following beam analogy, if plane surfaces remain plane (i.e, the floor slabs),then axial stresses in the columns of the

41、 outer tube, being farther form the neutral axis, will be substantially larger than the axial stresses in the inner tube. However, in the tube-in-tube design, when optimized, the axial stresses in the inner ring of colum

42、ns may be as high, or even higher, than the axial stresses in the outer ring. This seeming anomaly is associated with differences in the shearing component of st</p><p>　　Core Interactive Structures</p>

43、;<p>　　Core interactive structures are a special case of a tube-in-tube wherein the two tubes are coupled together with some form of three-dimensional space frame. Indeed, the system is used often wherein the shea

44、r stiffness of the outer tube is zero. The United States Steel Building, Pittsburgh, illustrates the system very well. Here, the inner tube is a braced frame, the outer tube has no shear stiffness, and the two systems ar

45、e coupled if they were considered as systems passing in a straight line fr</p><p>　　The space structures of outrigger girders or trusses, that connect the inner tube to the outer tube, are located often at s

46、everal levels in the building. The AT&T headquarters is an example of an astonishing array of interactive elements:</p><p>　　The structural system is 94 ft (28.6m) wide, 196ft(59.7m) long, and 601ft (18

47、3.3m) high.</p><p>　　Two inner tubes are provided, each 31ft(9.4m) by 40 ft (12.2m), centered 90 ft (27.4m) apart in the long direction of the building.</p><p>　　The inner tubes are braced in th

48、e short direction, but with zero shear stiffness in the long direction.</p><p>　　A single outer tube is supplied, which encircles the building perimeter.</p><p>　　The outer tube is a moment-resi

49、sting frame, but with zero shear stiffness for the center50ft (15.2m) of each of the long sides.</p><p>　　A space-truss hat structure is provided at the top of the building.</p><p>　　A similar s

50、pace truss is located near the bottom of the building</p><p>　　The entire assembly is laterally supported at the base on twin steel-plate tubes, because the shear stiffness of the outer tube goes to zero at

51、the base of the building.</p><p>　　Cellular structures</p><p>　　A classic example of a cellular structure is the Sears Tower, Chicago, a bundled tube structure of nine separate tubes. While the

52、Sears Tower contains nine nearly identical tubes, the basic structural system has special application for buildings of irregular shape, as the several tubes need not be similar in plan shape, It is not uncommon that some

53、 of the individual tubes one of the strengths and one of the weaknesses of the system.</p><p>　　This special weakness of this system, particularly in framed tubes, has to do with the concept of differential

54、column shortening. The shortening of a column under load is given by the expression</p><p><b>　　△=ΣfL/E</b></p><p>　　For buildings of 12 ft (3.66m) floor-to-floor distances and an av

55、erage compressive stress of 15 ksi (138MPa), the shortening of a column under load is 15 (12)(12)/29,000 or 0.074in (1.9mm) per story. At 50 stories, the column will have shortened to 3.7 in. (94mm) less than its unstres

56、sed length. Where one cell of a bundled tube system is, say, 50stories high and an adjacent cell is, say, 100stories high, those columns near the boundary between .the two systems need to have this differential defl</

57、p><p>　　Major structural work has been found to be needed at such locations. In at least one building, the Rialto Project, Melbourne, the structural engineer found it necessary to vertically pre-stress the lowe

58、r height columns so as to reconcile the differential deflections of columns in close proximity with the post-tensioning of the shorter column simulating the weight to be added on to adjacent, higher columns.</p>&

59、lt;p>　　抗側向荷載的結構體系</p><p><b>　　常用的結構體系：</b></p><p>　　若已測出荷載量達數(shù)千萬磅重，那么在高層建筑設計中就沒有多少可以進行極其復雜的構思余地了。確實，較好的高層建筑普遍具有構思簡單、表現(xiàn)明晰的特點。</p><p>　　這并不是說沒有進行宏觀構思的余地。實際上，正是因為有了這種宏觀的構

60、思，新奇的高層建筑體系才得以發(fā)展，可能更重要的是：幾年以前才出現(xiàn)的一些新概念在今天的技術中已經(jīng)變得平常了。</p><p>　　如果忽略一些與建筑材料密切相關的概念不談，高層建筑里最為常用的結構體系便可分為如下幾類：</p><p><b>　　抗彎矩框架。</b></p><p>　　支撐框架，包括偏心支撐框架。</p><

61、;p>　　剪力墻，包括鋼板剪力墻。</p><p><b>　　筒中框架。</b></p><p><b>　　筒中筒結構。</b></p><p><b>　　核心交互結構。</b></p><p>　　框格體系或束筒體系。</p><p>　　

62、特別是由于最近趨向于更復雜的建筑形式，同時也需要增加剛度以抵抗幾力和地震力，大多數(shù)高層建筑都具有由框架、支撐構架、剪力墻和相關體系相結合而構成的體系。而且，就較高的建筑物而言，大多數(shù)都是由交互式構件組成三維陳列。</p><p>　　將這些構件結合起來的方法正是高層建筑設計方法的本質(zhì)。其結合方式需要在考慮環(huán)境、功能和費用后再發(fā)展，以便提供促使建筑發(fā)展達到新高度的有效結構。這并不是說富于想象力的結構設計就能夠創(chuàng)造出

63、偉大建筑。正相反，有許多例優(yōu)美的建筑僅得到結構工程師適當?shù)闹С志捅粍?chuàng)造出來了，然而，如果沒有天賦甚厚的建筑師的創(chuàng)造力的指導，那么，得以發(fā)展的就只能是好的結構，并非是偉大的建筑。無論如何，要想創(chuàng)造出高層建筑真正非凡的設計，兩者都需要最好的。</p><p>　　雖然在文獻中通?？梢砸姷接嘘P這七種體系的全面性討論，但是在這里還值得進一步討論。設計方法的本質(zhì)貫穿于整個討論。設計方法的本質(zhì)貫穿于整個討論中。</p&

64、gt;<p><b>　　抗彎矩框架：</b></p><p>　　抗彎矩框架也許是低，中高度的建筑中常用的體系，它具有線性水平構件和垂直構件在接頭處基本剛接之特點。這種框架用作獨立的體系，或者和其他體系結合起來使用，以便提供所需要水平荷載抵抗力。對于較高的高層建筑，可能會發(fā)現(xiàn)該本系不宜作為獨立體系，這是因為在側向力的作用下難以調(diào)動足夠的剛度。</p><p

65、>　　我們可以利用STRESS，STRUDL 或者其他大量合適的計算機程序進行結構分析。所謂的門架法分析或懸臂法分析在當今的技術中無一席之地，由于柱梁節(jié)點固有柔性，并且由于初步設計應該力求突出體系的弱點，所以在初析中使用框架的中心距尺寸設計是司空慣的。當然，在設計的后期階段，實際地評價結點的變形很有必要。</p><p><b>　　支撐框架：</b></p><p

66、>　　支撐框架實際上剛度比抗彎矩框架強，在高層建筑中也得到更廣泛的應用。這種體系以其結點處鉸接或則接的線性水平構件、垂直構件和斜撐構件而具特色，它通常與其他體系共同用于較高的建筑，并且作為一種獨立的體系用在低、中高度的建筑中。</p><p>　　尤其引人關注的是，在強震區(qū)使用偏心支撐框架。</p><p>　　此外，可以利用STRESS，STRUDL，或一系列二維或三維計算機分析程

67、序中的任何一種進行結構分析。另外，初步分析中常用中心距尺寸。</p><p><b>　　剪力墻：</b></p><p>　　剪力墻在加強結構體系剛性的發(fā)展過程中又前進了一步。該體系的特點是具有相當薄的，通常是（而不總是）混凝土的構件，這種構件既可提供結構強度，又可提供建筑物功能上的分隔。</p><p>　　在高層建筑中，剪力墻體系趨向于具

68、有相對大的高寬經(jīng)，即與寬度相比，其高度偏大。由于基礎體系缺少應力，任何一種結構構件抗傾覆彎矩的能力都受到體系的寬度和構件承受的重力荷載的限制。由于剪力墻寬度狹狹窄受限，所以需要以某種方式加以擴大，以便提從所需的抗傾覆能力。在窗戶需要量小的建筑物外墻中明顯地使用了這種確有所需要寬度的體系。</p><p>　　鋼結構剪力墻通常由混凝土覆蓋層來加強以抵抗失穩(wěn)，這在剪切荷載大的地方已得到應用。這種體系實際上比鋼支撐經(jīng)濟

69、，對于使剪切荷載由位于地面正上方區(qū)域內(nèi)比較高的樓層向下移特別有效。這種體系還具有高延性之優(yōu)點，這種特性在強震區(qū)特別重要。</p><p>　　由于這些墻內(nèi)必然出同一些大孔，使得剪力墻體系分析變得錯綜復雜。可以通過桁架模似法、有限元法，或者通過利用為考慮剪力墻的交互作用或扭轉(zhuǎn)功能設計的專門計處機程序進行初步分析。</p><p>　　框架或支撐式筒體結構：</p><p&

70、gt;　　框架或支撐式筒體最先應用于IBM公司在Pittsburgh的一幢辦公樓，隨后立即被應用于紐約雙子座的110層世界貿(mào)易中心摩天大樓和其他的建筑中。這種系統(tǒng)有以下幾個顯著的特征：三維結構、支撐式結構、或由剪力墻形成的一個性質(zhì)上差不多是圓柱體的閉合曲面，但又有任意的平面構成。由于這些抵抗側向荷載的柱子差不多都被設置在整個系統(tǒng)的中心，所以整體的慣性得到提高，剛度也是很大的。</p><p>　　在可能的情況下，

71、通過三維概念的應用、二維的類比，我們可以進行筒體結構的分析。不管應用那種方法，都必須考慮剪力滯后的影響。</p><p>　　這種最先在航天器結構中研究的剪力滯后出現(xiàn)后，對筒體結構的剛度是一個很大的限制。這種觀念已經(jīng)影響了筒體結構在60層以上建筑中的應用。設計者已經(jīng)開發(fā)出了很多的技術，用以減小剪力滯后的影響，這其中最有名的是桁架的應用?？蚣芑蛑问酵搀w在40層或稍高的建筑中找到了自己的用武之地。除了一些美觀的考慮

72、外，桁架幾乎很少涉及與外墻聯(lián)系的每個建筑功能，而懸索一般設置在機械的地板上，這就令機械體系設計師們很不贊成。但是，作為一個性價比較好的結構體系，桁架能充分發(fā)揮它的性能，所以它會得到設計師們持續(xù)的支持。由于其最佳位置正取決于所提供的桁架的數(shù)量，因此很多研究已經(jīng)試圖完善這些構件的位置。實驗表明：由于這種結構體系的經(jīng)濟性并不十分受桁架位置的影響，所以這些桁架的位置主要取決于機械系統(tǒng)的完善，審美的要求，</p><p>

73、<b>　　筒中筒結構：</b></p><p>　　筒體結構系統(tǒng)能使外墻中的柱具有靈活性，用以抵抗顛覆和剪切力?！巴仓型病边@個名字顧名思義就是在建筑物的核心承重部分又被包圍了第二層的一系列柱子，它們被當作是框架和支撐筒來使用。配置第二層柱的目的是增強抗顛覆能力和增大側移剛度。這些筒體不是同樣的功能，也就是說，有些筒體是結構的，而有些筒體是用來支撐的。</p><p>

74、;　　在考慮這種筒體時，清楚的認識和區(qū)別變形的剪切和彎曲分量是很重要的，這源于對梁的對比分析。在結構筒中，剪切構件的偏角和柱、縱梁（例如：結構筒中的網(wǎng)等）的彎曲有關，同時，彎曲構件的偏角取決于柱子的軸心壓縮和延伸（例如：結構筒的邊緣等）。在支撐筒中，剪切構件的偏角和對角線的軸心變形有關，而彎曲構件的偏角則與柱子的軸心壓縮和延伸有關。</p><p>　　根據(jù)梁的對比分析，如果平面保持原形（例如：厚樓板），那么外層

75、筒中柱的軸心壓力就會與中心筒柱的軸心壓力相差甚遠，而且穩(wěn)定的大于中心筒。但是在筒中筒結構的設計中，當發(fā)展到極限時，內(nèi)部軸心壓力會很高的，甚至遠遠大于外部的柱子。這種反常的現(xiàn)象是由于兩種體系中的剪切構件的剛度不同。這很容易去理解，內(nèi)筒可以看成是一個支撐（或者說是剪切剛性的）筒，而外筒可以看成是一個結構（或者說是剪切彈性的）筒。</p><p><b>　　核心交互式結構：</b></p&

76、gt;<p>　　核心交互式結構屬于兩個筒與某些形式的三維空間框架相配合的筒中筒特殊情況。事實上，這種體系常用于那種外筒剪切剛度為零的結構。位于Pittsburgh的美國鋼鐵大樓證實了這種體系是能很好的工作的。在核心交互式結構中，內(nèi)筒是一個支撐結構，外筒沒有任何剪切剛度，而且兩種結構體系能通過一個空間結構或“帽”式結構共同起作用。需要指出的是，如果把外部的柱子看成是一種從“帽”到基礎的直線體系，這將是不合適的；根據(jù)支撐核心

77、的彈性曲線，這些柱子只發(fā)揮了剛度的15%。同樣需要指出的是，內(nèi)柱中與側向力有關的軸向力沿筒高度由拉力變?yōu)閴毫Γ瑫r變化點位于筒高度的約5/8處。當然，外柱也傳遞相同的軸向力，這種軸向力低于作用在整個柱子高度的側向荷載，因為這個體系的剪切剛度接近于零。</p><p>　　把內(nèi)外筒相連接的空間結構、懸臂梁或桁架經(jīng)常遵照一些規(guī)范來布置。美國電話電報總局就是一個布置交互式構件的生動例子。</p><

78、p>　　結構體系長59.7米，寬28.6米，高183.3米。</p><p>　　布置了兩個筒，每個筒的尺寸是9.4米×12.2米，在長方向上有27.4米的間隔。</p><p>　　在短方向上內(nèi)筒被支撐起來，但是在長方向上沒有剪切剛度。</p><p>　　環(huán)繞著建筑物布置了一個外筒。</p><p>　　外筒是一個瞬時抵抗

79、結構，但是在每個長方向的中心15.2米都沒有剪切剛度。</p><p>　　在建筑的頂部布置了一個空間桁架構成的“帽式”結構。</p><p>　　在建筑的底部布置了一個相似的空間桁架結構。</p><p>　　由于外筒的剪切剛度在建筑的底部接近零，整個建筑基本上由兩個鋼板筒來支持。</p><p>　　框格體系或束筒體系結構：</p&

80、gt;<p>　　位于美國芝加哥的西爾斯大廈是箱式結構的經(jīng)典之作，它由九個相互獨立的筒組成的一個集中筒。由于西爾斯大廈包括九個幾乎垂直的筒，而且筒在平面上無須相似，基本的結構體系在不規(guī)則形狀的建筑中得到特別的應用。一些單個的筒高于建筑一點或很多是很常見的。事實上，這種體系的重要特征就在于它既有堅固的一面，也有脆弱的一面。</p><p>　　這種體系的脆弱，特別是在結構筒中，與柱子的壓縮變形有很大的

81、關系，柱子的壓縮變形有下式計算：</p><p><b>　　△=ΣfL/E</b></p><p>　　對于那些層高為3.66米左右和平均壓力為138MPa的建筑，在荷載作用下每層柱子的壓縮變形為15（12）/29000或1.9毫米。在第50層柱子會壓縮94毫米，小于它未受壓的長度。這些柱子在50層的時候和100層的時候的變形是不一樣的，位于這兩種體系之間接近于邊緣