Liwcbi土木工程畢業(yè)論文中英文翻譯.doc

秋風清，秋月明,落葉聚還散,寒鴉棲復驚。一、科技資料原文：Structural Systems to resist lateral loadsCommonly Used structural SystemsWith loads measured in tens of thousands kips, there is little room in the design of high-rise buildings for excessively complex thoughts. Indeed, the better high-rise buildings carry the universal traits of simplicity of thought and clarity of expression.It does not follow that there 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 today s technology.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 follows:1. Moment-resisting frames.2. Braced frames, including eccentrically braced frames.3. Shear walls, including steel plate shear walls.4. Tube-in-tube structures.5. Tube-in-tube structures.6. Core-interactive structures.7. Cellular or bundled-tube systems.Particularly with the 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 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.The method of combining 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 that 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 only moderate support from the structural engineer, while only fine structure, not great architecture, can be developed without the genius and the leadership of a talented architect. In any event, the best of both is needed to formulate a truly extraordinary design of a high-rise building.While comprehensive discussions of these seven systems are generally available in the literature, further discussion is warranted here .The essence of the design process is distributed throughout the discussion.Moment-Resisting FramesPerhaps the most commonly used system in low-to medium-rise buildings, the moment-resisting frame, is 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 resistance 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 mobilizing sufficient stiffness under lateral forces. Analysis can be accomplished 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 todays technology.Because of the intrinsic 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 analysis. Of course, in the latter phases of design, a realistic appraisal in-joint deformation is essential.Braced FramesThe braced frame, intrinsically stiffer than the moment 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 commonly in conjunction with other systems for taller buildings and as a stand-alone system in low-to medium-rise buildings.While the use of structural steel in braced frames is common, concrete frames are more likely to be of the larger-scale variety.Of special interest in areas of high seismicity is the use of the eccentric braced frame.Again, analysis can be by STRESS, 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. Shear wallsThe 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 both structural strength and separation between building functions.In high-rise buildings, shear wall systems tend to have a relatively high aspect ratio, that is, their height tends to be large compared 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. Limited 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 requirement for windows is kept small.Structural steel shear walls, generally stiffened 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 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.The analysis of shear 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 computer program designed to consider the interaction, or coupling, of shear walls.Framed or Braced TubesThe concept of the framed or braced or braced tube erupted into the technology 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 dimensional 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 as possible from the cancroids of the system, the overall moment of inertia is increased and stiffness is very high.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 lag.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 shear 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. However, except for possible aesthetic considerations, belt trusses interfere with nearly every building function associated with the outside wall; the trusses are placed often at mechanical floors, mush to the disapproval of the designers of the mechanical systems. Nevertheless, as a cost-effective structural system, the belt truss works well and will likely find continued approval from designers. Numerous studies have sought to optimize the location of these trusses, with the optimum location very dependent on the number of trusses provided. Experience would indicate, however, that the location of these trusses is provided by the optimization of mechanical systems and by aesthetic considerations, as the economics of the structural system is not highly sensitive to belt truss location.Tube-in-Tube StructuresThe tubular framing system mobilizes every column in the exterior wall in resisting over-turning and shearing forces. The termtube-in-tubeis 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 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, while the other could be braced.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 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 columns (i.e, the flanges of the framed tube). In a braced tube, the shear component of deflection is associated with the axial deformation of diagonals while the flexural component of deflection is associated with the axial shortening and lengthening of columns.Following beam analogy, if plane surfaces remain plane (i.e, the floor slabs),then axial stresses in the columns of the 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 columns 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 stiffness between the two systems. This is easiest to under-stand where the inner tube is conceived as a braced (i.e, shear-stiff) tube while the outer tube is conceived as a framed (i.e, shear-flexible) tube.Core Interactive StructuresCore 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 shear 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 are coupled if they were considered as systems passing in a straight line from the “hat” structure. Note that the exterior columns would be improperly modeled if they were considered as systems passing in a straight line from the “hat” to the foundations; these columns are perhaps 15% stiffer as they follow the elastic curve of the braced core. Note also that the axial forces associated with the lateral forces in the inner columns change from tension to compression over the height of the tube, with the inflection point at about 5/8 of the height of the tube. The outer columns, of course, carry the same axial force under lateral load for the full height of the columns because the columns because the shear stiffness of the system is close to zero. The space structures of outrigger girders or trusses, that connect the inner tube to the outer tube, are located often at several levels in the building. The AT&T headquarters is an example of an astonishing array of interactive elements:1. The structural system is 94 ft (28.6m) wide, 196ft(59.7m) long, and 601ft (183.3m) high.2. 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.3. The inner tubes are braced in the short direction, but with zero shear stiffness in the long direction.4. A single outer tube is supplied, which encircles the building perimeter.5. The outer tube is a moment-resisting frame, but with zero shear stiffness for the center50ft (15.2m) of each of the long sides.6. A space-truss hat structure is provided at the top of the building.7. A similar space truss is located near the bottom of the building8. 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 the base of the building.Cellular structuresA classic example of a cellular structure is the Sears Tower, Chicago, a bundled tube structure of nine separate tubes. While the 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 of the individual tubes one of the strengths and one of the weaknesses of the system.This special weakness of this system, particularly in framed tubes, has to do with the concept of differential column shortening. The shortening of a column under load is given by the expression=fL/EFor buildings of 12 ft (3.66m) floor-to-floor distances and an average 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 unstressed 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 deflection reconciled. 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 lower 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.二、原文翻譯：抗側向荷載的結構體系常用的結構體系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。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。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：1 抗彎矩框架。2 支撐框架，包括偏心支撐框架。3 剪力墻，包括鋼板剪力墻。4 筒中框架。5 筒中筒結構。6 核心交互結構。7 框格體系或束筒體系。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。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。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。 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。設計方法的本質貫穿于整個討論。設計方法的本質貫穿于整個討論中?？箯澗乜蚣芸箯澗乜蚣芤苍S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動足夠的剛度。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。支撐框架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。尤其引人關注的是，在強震區(qū)使用偏心支撐框架。此外，可以利用STRESS，STRUDL，或一系列二維或三維計算機分析程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。剪力墻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。在高層建筑中，剪力墻體系趨向于具有相對大的高寬經(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。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，對于使剪切荷載由位于地面正上方區(qū)域內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。由于這些墻內必然出同一些大孔，使得剪力墻體系分析變得錯綜復雜?？梢酝ㄟ^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功能設計的專門計處機程序進行初步分析框架或支撐式筒體結構：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。在可能的情況下，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。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。框架或支撐式筒體在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