土木工程專業(yè)畢業(yè)設(shè)計外文翻譯

1、High-Rise BuildingsIn troducti onIt is difficult to defi ne a high-rise buildi ng . One may say that a low-rise build ing ran ges from 1 to 2 stories . A medium-rise buildi ng p robably ran ges betwee n 3 or 4 stories up to 10 or 20 stories or more .Although the basic principles of vertical and hori

2、z on tal subsystem desig n rema in the same for low- , medium- , or high-rise build ings , whe n a build ing gets high the vertical subsystemsbecome a con trolli ng p roblem for two reas ons . Higher vertical loads will require larger colu mns , walls , and shafts . But , more sig nifica ntly , the

3、overtur ning mome nt and the shear deflect ions p roduced by lateral forces are much larger and must be carefully pro vided for .The vertical subsystems in a high-rise buildi ng tran smit accumulated gravity load from story to story , thus requiri ng larger colu mn or wall secti ons to support such

4、loadi ng .In additi on these same vertical subsystems must tran smit lateral loads , such as wi nd or seismic loads , to the foun datio ns. However , in con trast to vertical load , lateral load effects on build ings are not lin ear and in crease rap idly with in crease in height . For example under

5、 wind load , the overturning moment at the base of buildings varies approximately as the square of a buildings may vary as the fourth power of buildings height , other things being equal. Earthquake produces an even more pronoun ced effect.“short ” buildiWhen the structure for a low-or medium-rise b

6、uilding is designed for dead and live load , it is almost an in here nt property that the colu mns , walls , and stair or elevator shafts can carry most of the horiz on tal forces . The p roblem is p rimarily one of shear resista nee . Moderate additi on braci ng for rigid frames in easily be pro vi

7、ded by filli ng certa in pan els ( or eve n all pan els ) without in creas ing the sizes of the colu mns and girders otherwise required for vertical loads.Unfortunately , this is not is for high-rise buildings because the problem is p rimarily resista nee to mome nt and deflect ion rather tha n shea

8、r alone . Sp ecial structural arra ngeme nts will ofte n have to be made and additi onal structural material is always required for the columns , girders , walls , and slabs in order to made a high-rise buildi ngs sufficie ntly resista nt to much higher lateral deformati ons .As p reviously men ti o

9、ned , the qua ntity of structural material required per square foot of floor of a high-rise buildings is in excess of that required for low-rise buildings . The vertical components carrying the gravity load , such as walls , columns , and shafts , will need to be strengthened over the full height of

10、 the build ings . But qua ntity of material required for resisti ng lateral forces is eve n more sig nifica nt .With rei nforced con crete , the qua ntity of material also in creases as the nu mber of stories in creases . But here it should be no ted that the in crease in the weight of material adde

11、d for gravity load is much more sizable tha n steel , whereas for windload the in crease for lateral force resista nee is not that much more since the weight of a concrete buildings helps to resist overturn . On the other hand , the problem of desig n for earthquake forces . Additi onal mass in the

12、upper floors will give rise to a greater overall lateral force un der the of seismic effects .In the case of either concrete or steel design , there are certain basic principles for pro vid ing additi onal resista nee to lateral to lateral forces and deflecti ons in high-rise build ings without too

13、much sacrifire in economy .1.In crease the effective width of the mome nt-resisti ng subsystems . This is very useful because in creas ing the width will cut dow n the overtur n force directly and will reduce deflecti on by the third po wer of the width in crease , other things rema ining cin sta nt

14、 . However , this does require that vertical components of the widened subsystem be suitably connected to actually gain this ben efit.2.Desig n subsystemssuch that the components are made to in teract in the most efficient manner . For example , use truss systems with chords and diagonals efficientl

15、y stressed , place reinforcing for walls at critical locati ons , and op timize stiff ness ratios for rigid frames .3.In crease the material in the most effective resist ing components . For exa mple , materials added in the lower floors to the flan ges of colu mns and conn ect ing girders will dire

16、ctly decrease the overall deflect ion and in crease the mome nt resista nee without con tribut ing mass in the upper floors where the earthquake p roblem is aggravated .4.Arrange to have the greater part of vertical loads be carried directly on the primary moment-resisting components . This will hel

17、p stabilize the build ings aga inst ten sile overtu rning forces by p reco mp ress in gthe major overturn-resisti ng components .5.The local shear in each story can be best resisted by strategic pl aceme nt if solid walls or the use of diagonal members in a vertical subsystem . Resist ing these shea

18、rs solely by vertical members in bending is usually less econo mical , since achiev ing sufficie nt bending resista nee in the colu mns and conn ect ing girders will require more material and con struct ion en ergy tha n using walls or diago nal members .6.Sufficie nt horiz on tal dia phragm acti on

19、 should be pro vided floor . This will help to bring the various resist ing eleme nts to work together in stead of sep arately .7.Create mega-frames by joining large vertical and horizontal components such as two or more elevator shafts at multistory intervals with a heavy floor subsystems , or by u

20、se of very dee p girder trusses .Remember that all high-rise build ings are esse ntially vertical can tilevers which are supported at the ground . When the above principles are judiciously applied , structurally desirable schemes can be obta ined by walls , cores , rigid frames, tubular con struct i

21、on , and other vertical subsystems to achieve horiz on tal stre ngth and rigidity . Some of these app licati ons will now be described in subseque nt secti ons in the followi ng .Shear-Wall SystemsWhen shear walls are comp atible with other fun cti onal requireme nts , they can be economically utili

22、zed to resist lateral forces in high-rise buildings . For example , ap artme nt build ings n aturally require many sep arati on walls . Whe n some of these are desig ned to be solid , they can act as shear walls to resist lateral forces and to carry the vertical load as well . For buildi ngs up to s

23、ome 20storise , the use of shear walls is com mon .If give n sufficie nt len gth ,such walls can econo mically resist lateral forces up to 30 to 40 stories or more .However , shear walls can resist lateral load only the plane of the walls ( i.e .not in a direti on perpen dicular to them ) . There fo

24、re ,it is always n ecessary to pro vide shear walls in two perpen dicular directi ons can be at least in sufficie nt orie ntati on so that lateral force in any direct ion can be resisted .In additi on , that wall layout should reflect con siderati on of any torsi onal effect .In desig n p rogress ,

25、two or more shear walls can be conn ected to from L-sha ped or cha nn el-sha ped subsystems .In deed internal shear walls can be conn ected to from a rectangular shaft that will resist lateral forces very efficiently . If all external shear walls are continuously connected , then the whole buildings

26、 acts as tube , and conn ected , the n the whole buildi ngs acts as a tube , and is excelle nt Shear-Wall Seystems resist ing lateral loads and torsi on .Whereas con crete shear walls are gen erally of solid type with openings whe n necessary, steel shear walls are usually made of trusses . These tr

27、usses can have single diagonals , “X” diagona|sor “ K” arrangenhs . A trussed wall will have its members act esse ntially in direct tension or comp ressi on un der the acti on of view , and they offer some opportunity and deflection-limitation point of view , and they offer some opportunity for pene

28、tration between members . Of course , the inclined members of trusses must be suitable p laced so as not to in terfere with requireme nts for wion dows and for circulati on service pen etrati ons though these walls .As stated above , the walls of elevator , staircase ,and utility shafts form n atura

29、l tubes and are com monly empio yed to resist both vertical and lateral forces . Since these shafts are no rmally recta ngular or circular in cross-sect ion , they can offer an efficie nt means for resist ing mome nts and shear in all directi ons due to tube structural action . But a p roblem in the

30、 desig n of these shafts is pro vided sufficie nt stre ngth around door openings and other pen etrati ons through these eleme nts . For rein forced concrete construction , special steel reinforcements are placed around such opening .In steel con struct ion , heavier and more rigid conn ecti ons are

31、required to resist rack ing at the openings .In many high-rise build ings , a comb in ati on of walls and shafts can offer excelle nt resista nee to lateral forces whe n they are suitably located ant conn ected to one ano ther . It is also desirable that the stiff ness offered these subsystems be mo

32、re-or-less symmertrical in all direct ions .Rigid-Frame SystemsIn the desig n of architectural build ings , rigid-frame systems for resist ing vertical and lateral loads have long bee n acce pted as an imp orta nt and sta ndard means for designing building . They are empioyed for low-and medium mean

33、s for designing build ings . They are empio yed for low- and medium up to high-rise build ing p erha ps 70 or 100 stories high . Whe n comp ared to shear-wall systems , these rigid frames both with in and at the outside of a buildi ngs . They also make use of the stiff ness in beams and colu mns tha

34、t are required for the build ings in any case , but the colu mns are made stron ger whe n rigidly conn ected to resist the lateral as well as vertical forces though frame bending .Freque ntly , rigid frames will not be as stiff as shear-wall con struct ion , and therefore may p roduce excessive defl

35、ecti ons for the more sle nder high-rise buildi ngs desig ns . But because of this flexibility , they are ofte n con sidered as being more ductile and thus less susce ptible to catastr op hic earthquake failure whe n comp ared with ( some ) shear-wall desig ns . For exa mple , if over stress ing occ

36、urs at certa in p orti ons of a steel rigid frame ( i.e., near the joi nt ) , ductility will allow the structure as a whole to deflect a little more , but it will by no means colla pse eve n un der a much larger force tha n exp ected on the structure . For this reas on , rigid-frame con struct ion i

37、s considered by some to be a “ best ” seisresisting type for high-rise steel buildings . On the other hand ,it is also unlikely that a well-designed share-wall system would colla pse.In the case of con crete rigid frames ,there is a diverge nee of opinion .It true that if a con crete rigid frame is

38、desig ned in the conven ti onal manner , without sp ecial care to produce higher ductility , it will not be able to withstand a catastrophic earthquake that can p roduce forces several times lerger tha n the code desig n earthquake forces . therefore , some believe that it may not have additi onal c

39、ap acity p ossessed by steel rigid frames . But moder n research and exp erie nee has in dicated that con crete frames can be desig ned to be ductile , whe n sufficie nt stirr ups and joinery rein forceme nt are designed in to the frame . Modern buildings codes have specifications for the so-called

40、ductile con crete frames . However , at p rese nt , these codes ofte n require excessive rein forceme nt at certa in points in the frame so as to cause con gesti on and result in construction difficulties 。 Even so , concrete frame design can be both effective and econo mical。Of course , it is also

41、p ossible to comb ine rigid-frame con structi on with shear-wall systems in one buildings , For example , the buildings geometry may be such that rigid frames can be used in one directi on while shear walls may be used in the other directi on。SummaryAbove states is the high-rise con struct ion ordin

42、 ariest structural style. In the desig n p rocess, should the economy p ractical choose the reas on able form as far as p ossible.高層建筑前沿高層建筑的定義很難確定?？梢哉f 2-3層的建筑物為底層建筑，而從 3-4 層地10層或20層的建筑物為中層建筑，高層建筑至少為 10層或者更多。盡管在原理上，高層建筑的豎向和水平構(gòu)件的設(shè)計同低層及多層建筑的設(shè)計沒什么區(qū)別，但使豎向構(gòu)件的設(shè)計成為高層設(shè)計有兩個控制性的因素：首先，高層建筑需要較大的柱體、墻體和井筒；更重要的是側(cè)向

43、里所產(chǎn)生的傾覆力矩和剪 力變形要大的多，必要謹慎設(shè)計來保證。高層建筑的豎向構(gòu)件從上到下逐層對累積的重力和荷載進行傳遞，這就要有較大尺寸的墻體或者柱體來進行承載。 同時，這些構(gòu)件還要將風(fēng)荷載及地震荷載 等側(cè)向荷載傳給基礎(chǔ)。但是，側(cè)向荷載的分布不同于豎向荷載，它們是非線性的， 并且沿著建筑物高度的增加而迅速地增加。 例如，在其他條件都相同時，風(fēng)荷載 在建筑物底部引起的傾覆力矩隨建筑物高度近似地成平方規(guī)律變化，而在頂部的側(cè)向位移與其高度的四次方成正比。地震荷載的效應(yīng)更為明顯。對于低層和多層建筑物設(shè)計只需考慮恒荷載和部分動荷載時，建筑物的柱、 墻、樓梯或電梯等就自然能承受大部分水平力。所考慮的問題主要

44、是抗剪問題。 對于現(xiàn)代的鋼架系統(tǒng)支撐設(shè)計，如無特殊承載需要，無需加大柱和梁的尺寸，而 通過增加板就可以實現(xiàn)。還有抵抗力矩和不幸的是，對于高層建筑首先要解決的不僅僅是抗剪問題， 抵抗變形問題。高層建筑中的柱、梁、墻及板等經(jīng)常需要采用特殊的結(jié)構(gòu)布置和 特殊的材料，以抵抗相當(dāng)高的側(cè)向荷載以及變形。如前所述，在高層建筑中每平方英尺建筑面積結(jié)構(gòu)材料的用量要高于低層建 筑。支撐重力荷載的豎向構(gòu)件，如墻、柱及井筒，在沿建筑物整個高度方向上都 應(yīng)予以加強。用于抵抗側(cè)向荷載的材料要求更多。對于鋼筋混凝土建筑，雖著建筑物層數(shù)的增加，對材料的要求也隨著增加。應(yīng)當(dāng)注意的是，因混凝土材料的質(zhì)量增加而帶來的建筑物自重增加

45、，要比鋼結(jié)構(gòu)增加得多，而為抵抗風(fēng)荷載的能力而增加的材料用量卻不是呢么多，因為混凝土自身的重量可以抵抗傾覆力矩。不過不利的一面是混凝土建筑自重的增加， 將會 加大抗震設(shè)計的難度。在地震荷載作用下，頂部質(zhì)量的增加將會使側(cè)向荷載劇增。無論對于混凝土結(jié)構(gòu)設(shè)計，還是對于鋼結(jié)構(gòu)設(shè)計，下面這些基本的原則都有 助于在不需要增加太多成本的前提下增強建筑物抵抗側(cè)向荷載的能力。增加抗彎構(gòu)件的有效寬度。由于當(dāng)其他條件不變時能夠直接減小扭 矩，并以寬度增量的三次幕形式減小變形，因此這一措施非常有效。 但是必須保證加寬后的豎向承重構(gòu)件非常有效地連接。在設(shè)計構(gòu)件時，盡可能有效地使其加強相互作用力。例如，可以采用 具有有效應(yīng)

46、力狀態(tài)的弦桿和桁架體系；也可在墻的關(guān)鍵位置加置鋼 筋；以及最優(yōu)化鋼架的剛度比等措施。增加最有效的抗彎構(gòu)件的截面。例如，增加較低層柱以及連接大梁的 翼緣截面，將可直接減少側(cè)向位移和增加抗彎能力，而不會加大上層 樓面的質(zhì)量，否則，地震問題將更加嚴重。通過設(shè)計使大部分豎向荷載，直接作用于主要的抗彎構(gòu)件。這樣通過 預(yù)壓主要的抗傾覆構(gòu)件，可以使建筑物在傾覆拉力的作用下保持穩(wěn) 定。通過合理地放置實心墻體及在豎向構(gòu)件中使用斜撐構(gòu)件，可以有效地抵抗每層的局部剪力。但僅僅通過豎向構(gòu)件進行抗剪是不經(jīng)濟的，因 為使柱及梁有足夠的抗彎能力，比用墻或斜撐需要更多材料和施工工 作量。每層應(yīng)加設(shè)充足的水平隔板。這樣就會使各種抗力構(gòu)件更好地在一起 工作，而不是單獨工作。在中間轉(zhuǎn)換層通過大型豎向和水平構(gòu)件及重樓板形成大框架，或者采用深梁體系。應(yīng)當(dāng)注意的是，所有高層建筑的本質(zhì)都是地面支撐的懸臂結(jié)構(gòu)。如何合理地 運用上面所提到的原則，就可以利用合理地布置墻體、核心筒、框架、筒式結(jié)構(gòu) 和其他豎向結(jié)構(gòu)分體系，使建筑物取得足夠的水平承載力和剛度。 這些原理的應(yīng)用做介