抗側(cè)向荷載地結(jié)構(gòu)體系外文翻譯

1、外文翻譯一.原文：Structural Systems to resist lateral loadsCommonly Used structural SystemsWith loads measured in tens of thousands kips, there is little room in the desig n of high-rise build ings for excessively complex thoughts. In deed, the better high-rise buildi ngs carry the uni versal traits of simp

2、licity of thought and clarity of expressi on.It does not follow that there is no room for grand thoughts. In deed, it is with such grand thoughts that the new family of high-risebuildingshas evolved. Perhaps more important, the new concepts of but a few years ago have become com mon place in today &

3、#39; s tech no logy.Omitting someconcepts that are related strictly to the materials of con struct ion, the most com monly used structural systems used in high-rise build ings can be categorized as follows:1. Moment-resisting frames.2. Braced frames, including eccentrically braced frames.3. Shear wa

4、lls, 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 resp onse also to the n eed for in creased stiff ness to resist the for

5、cesfrom wind and earthquake, most high-risebuildingshave structuralsystems built up of comb in ati ons of frames, braced ben ts, shear walls, and related systems. Further, for the taller build in gs, the majorities are composed of in teractive eleme nts in three-dime nsional arrays.The method of com

6、b ining these eleme nts is the very esse nee of the desig n process for high-rise build in gs. These comb in ati ons n eed evolve in resp onse to en vir onmen tal, function al, and cost con siderati ons so as to provide efficie nt structures that provoke the architectural development to newheights.

7、This is not to say that imaginative structural desig n can create great architecture. To the con trary, many examples of fine architecture have bee n created with only moderate support from the structural engineer, while only fine structure, not great architecture, can be developed without the geniu

8、s and the leadership of a tale nted architect. In any eve nt, the best of both is n eeded to formulate a truly extraord inary desig n of a high-rise build ing.While comprehe nsive discussi ons of these seve n systems are gen erally available in the literature, further discussion is warranted here .T

9、he esse nee of the desig n process is distributed throughout the discussi on.Mome nt-Resisti ng FramesPerhaps the most commonlyused system in low-to medium-rise buildings, the mome nt-resisti ng frame, is characterized by lin ear horiz on tal and vertical members conn ected esse ntially rigidly at t

10、heir jo in ts. Such frames are used as a sta nd-al one system or in comb in ati on with other systems so as to provide the n eeded resista nee to horiz on tal loads. In the taller of high-rise buildings, the system is likely to be found in appropriate for a sta nd-al one system, this because of the

11、difficulty in mobilizing sufficient stiffness under lateral forces.Analysis can be accomplished by STRESS, STRUDL, or a host of otherappropriate computer programs; an alysis by the so-called portal method of the can tilever method has no place in today' s tech no logy.Because of thein tri nsicfl

12、exibility of thecolu mn/girderin tersecti on, and because prelim inary desig ns 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 desig n, a realistic appraisal in-joint de

13、formati on is esse ntial.Braced FramesThe braced frame, in tri nsicallystiffer tha n the mome nt resisti ngframe, finds also greater applicationto higher-risebuildings.Thesystem is characterized by lin ear horiz on tal, vertical, and diag onal members, connected simply or rigidly at their joints.It

14、is used commonlyin conjunction with other systems for tallerbuildingsand as asta nd-al one system in low-to medium-rise build in gs.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 in terest in areas of high sei

15、smicity is the use of the ecce ntric braced frame.Agai n, an alysis can be by STRESS, STRUDL, or any one of a series of two - or three dimensional analysis computer programs. And again, cen ter-to-ce nter dime nsions are used com mon ly in the prelimi nary an alysis.Shear wallsThe shear wall is yet

16、ano ther step forward along a progressi on ofever-stiffer structural systems. The system is characterized by relatively thin, gen erally (but not always) con crete eleme nts that provide both structural strength and separation between building fun cti ons.In high-rise buildings, shear wall systems t

17、end to have a relatively high aspect ratio, that is, their height tends to be large compared to their width. Lack ing tension in the foun datio n system, any structural element is limited in its ability to resist overturning momentoy the width of the system and by the gravity load supported by the e

18、lement. Limited to a n arrow overt urning, One obvious use of the system, which does have the needed width, is in the exterior walls of building, where the requireme nt for win dows is kept small.Structural steel shear walls, gen erally stiffe ned aga inst buckli ng by a concrete overlay, have found

19、 application where shear loads are high. The system, in tri nsicallymore econo mical tha n steelbrac ing,isparticularly effective in carry ing shear loads dow n through the taller floors in the areas immediately above grade. The sys tem has the further advantage of having high ductility a feature of

20、 particularimportanee inareas of high seismicity.The an alysis of shear wall systems is made complex because of the in evitable prese nce of large ope nings through these walls. Prelimi nary analysis can be by truss-analogy, by the finite element method, or by making use of a proprietary computer pr

21、ogram desig ned to con sider the in teract ion, or coupli ng, of shear walls.Framed or Braced TubesThe con cept of the framed or braced or braced tube erupted into the tech no logy with the IBM Build ing in Pittsburgh, but was followed immediately with the twin 110-story towers of the World Trade Ce

22、nter, NewYork and a number of other buildings.The system is characterized by threedimensional frames, braced frames, or shear walls, forming a closed surface more or less cylindricalin nature, but of nearly any planconfiguration.Because those columns that resist lateral forces areplaced as far as po

23、ssible from the can croids of the system, the overall mome nt of in ertia is in creased and stiff ness is very high.The an alysis of tubular structures is done using three-dime nsio nalconcepts, or by two- dimensional analogy, where possible, whichever method is used, it must be capable of accountin

24、g for the effects of shear lag.The presenee 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.Desig ners have developed various tech niq ues for reduc i

25、ng the effects of shear lag, most no ticeably the use of belt trusses. This system finds application in buildings perhaps 40stories and higher. However, except for possible aesthetic considerations,belt trusses interferewith nearlyevery buildingfunction associated with the outside wall; the trusses

26、areplaced oftenat mechanical floors, mush to the disapproval of thedesig ners of the mecha ni cal systems. Nevertheless, as a cost-effective structuralsystem, the belt trussworks well and will likely findcontinued approvalfrom designers.Numerous studies have sought tooptimize the location of these t

27、russes, with the optimum location very depe ndent on the nu mber of trusses provided. Experie nee would in dicate, however, that the location of these trusses is providedby theoptimizatio n of mecha ni cal systems and by aesthetic con siderati ons, as the econo mics of the structural system is not h

28、ighly sen sitive to belt truss locati on.Tube-i n-Tube StructuresThe tubular framing system mobilizes every column in the exterior wall in resist ing over-turni ng and sheari ng forces. The term tube-i n-tube 'is largely self-expla natory in that a sec ond ring of colu mns, the ring surrounding

29、the central service core of the building, is used as an inner framed or braced tube. The purpose of the sec ond tube is to in crease resista nce to over turni ng and to in crease lateral stiff ness. The tubes need not be of the samecharacter; that is, one tube could be framed, while the other could

30、be braced.In con sideri ng this system, is importa nt to un dersta nd clearly the differe nce betwee n the shear and the flexural comp onents of deflecti on, the terms being taken from beam analogy. In a framed tube, the shear comp onent of deflect ion is associated with the bending deformati on of

31、columns and girders (i.e, the webs of the framed tube) while the flexural comp onent is associated with the axial shorte ning and len gthe ning of columns (i.e, the flanges of the framed tube). In a braced tube, the shear comp onent of deflect ion isassociated with the axial deformati on ofdiago nal

32、s while the flexural comp onent of deflecti on is associated with the axial shorte ning and len gthe ning of colu mns.Follow ing beama nalogy, if pla ne surfaces rema in pla ne (i.e, the floor slabs),thenaxial stresses in the columns of the outer tube, being fartherform the neutral axis, will be sub

33、stantially 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 maybe as high, or eve n higher, tha n the axial stresses in the outer ring. This seem ing ano maly is associated with differe nces in the

34、sheari ng comp onent of stiff ness betwee n the two systems. This is easiest to un der-sta nd where the inner tube is conceived as a braced (i.e, shear-stiff) tube while the outer tube is con ceived as a framed (i.e, shear-flexible) tube.Core Interactive StructuresCore in teractive structures are a

35、special case of a tube-i n-tubewherein the two tubes are coupled together with some form of three-dime nsio nal space frame. I ndeed, the system is used ofte n wherein the shear stiff ness of the outer tube is zero. The Un ited States SteelBuilding, Pittsburgh, illustrates the system very well. Here

36、, the inner tube is a braced frame, the outer tube has no shear stiff ness, and the two systems are coupled if they were con sidered as systems pass ing in a straight line from the “ hat ” structure. Note that the exterior columns would be improperly modeled if they were con sidered as systems pass

37、ing in a straight line from the “ hat ” to the foundations;these columns areperhaps 15% stiffer as they follow the elastic curve ofthe braced core.Note also that the axial forces associated with the lateral forces in the inner colu mns cha nge from tension to compressi on over the height of the tube

38、, with the in flecti on point at about5/8 of theheight of the tube. The outer colu mns, of course, carry the same axial force un der lateral load for the full height of the colu mns because the colu mns because the shear stiff ness of the system is close to zero.The space structures of outrigger gir

39、ders or trusses, that connect the inner tube to the outer tube, are located often at several levels in the building.The AT&Theadquarters is an example of an astonishingarray ofin teractive eleme nts:1. The structural system is 94 ft (28.6m) wide, 196ft(59.7m) Iong, and 601ft (183.3m) high.2. Two

40、 inner tubes are provided, each 31ft(9.4m) by 40 ft (12.2m),cen tered 90 ft (27.4m) apart in the long direct ion of the buildi ng.3. The inner tubes are braced in the short directi on, but with zero shear stiffness in the long direct ion.4. A singleouter tube is supplied, which encirclesthe building

41、perimeter.5. The outer tube is a moment-resisting frame, but with zero shearstiffness for the cen ter50ft (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

42、is laterally supported at the base on twinsteel-plate tubes, because the shear stiffness of the outer tube goes to zero at the base of the buildi ng.Cellular structuresA classic example of a cellular structure is the Sears Tower,Chicago, a bun dled tube structure of nine separate tubes. While theSears Tower contains nine nearly identical tubes,