【正文】 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(jié)構(gòu)（或者說是剪切彈性的）筒。在支撐筒中，剪切構(gòu)件的偏角和對角線的軸心變形有關(guān)，而彎曲構(gòu)件的偏角則與柱子的軸心壓縮和延伸有關(guān)。配置第二層柱的目的是增強抗顛覆能力和增大側(cè)移剛度。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(gòu)件的位置。設(shè)計者已經(jīng)開發(fā)出了很多的技術(shù)，用以減小剪力滯后的影響，這其中最有名的是桁架的應(yīng)用。 在可能的情況下，通過三維概念的應(yīng)用、二維的類比，我們可以進(jìn)行筒體結(jié)構(gòu)的分析。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(shè)計的專門計處機程序進(jìn)行初步分析。 鋼結(jié)構(gòu)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(yīng)用。 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。 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(jìn)行結(jié)構(gòu)分析。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(cè)向力的作用下難以調(diào)動足夠的剛度。正相反，有許多例優(yōu)美的建筑僅得到結(jié)構(gòu)工程師適當(dāng)?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(dǎo)，那么，得以發(fā)展的就只能是好的結(jié)構(gòu)，并非是偉大的建筑。而且，就較高 的建筑物而言，大多數(shù)都是由交互式構(gòu)件組成三維陳列。 5．筒中筒結(jié)構(gòu)。 抗側(cè)向荷載的結(jié)構(gòu)體系 如果忽略一些與建筑材料密切相關(guān)的概念不談，高層建筑里最為常用的結(jié)構(gòu)體系便可分為如下幾類： 1．抗彎矩框架。然而，這些規(guī)范往往要求在框架的某處增設(shè)過多的鋼筋，這就增加了施工的難度。如果在混凝土框架設(shè)計時不進(jìn)行特殊的延性設(shè)計，那么他將很難承受比設(shè)計標(biāo)準(zhǔn)值大很多倍的地震荷載的沖擊。因此，框架結(jié)構(gòu)常被視為最好的高層抗震結(jié)構(gòu)。同時它還能充分利用建筑物內(nèi)在任何情況下都要采用的梁和柱的剛度，但當(dāng)柱子與梁剛性連接時，通過框架受彎來抵抗水平和豎向荷載會使這些柱子的承載能力變得更大。還要求由這些結(jié)構(gòu)分體系提供的剛度在各個方向上應(yīng)大體對稱。在側(cè)向力作用下這些桁架的組合構(gòu) 件受到或拉或壓力。實際上，四片內(nèi)剪力墻可以被聯(lián)結(jié)成矩形，以更有效地抵抗側(cè)向荷載。 但是，剪力墻只能抵抗平行于墻平面的荷載（也就是說不能抵抗垂直于墻的荷載）。 剪力墻結(jié)構(gòu) 在能夠滿足其他功能需求時，高層建筑中采用剪力墻可以經(jīng)濟(jì)地進(jìn)行高層建筑的抗側(cè)向荷載設(shè)計。在設(shè)計構(gòu)件時，盡可能有效地使其加強相互作用力。 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。 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。地震荷載的效應(yīng)更為明顯。 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(jìn)行傳遞，這就要有較大尺寸的墻體或者柱體來進(jìn)行承載。 7. 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。 5. 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。 3. 增加最有效的抗彎構(gòu)件的截面。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冪形式減小變形，因此這一措施非常有效。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。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。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)。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。 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)向里所產(chǎn)生的傾覆力矩和剪力變形要大的多，必要謹(jǐn)慎設(shè)計來保證。 Structural Systems to resist lateral loads Omitting some concepts that are related strictly to the materials of construction, the most monly used structural systems used in highrise buildings can be categorized as follows: frames. frames, including eccentrically braced frames. walls, including steel plate shear walls. structures. structures. structures. or bundledtube systems. Particularly with the recent trend toward more plex forms, but in response also to the need for increased stiffness to resist the forces from wind and earthquake, most highrise buildings have structural systems built up of binations of frames, braced bents, shear walls, and related systems. Further, for the taller buildings, the majorities are posed of interactive elements in threedimensional arrays. The method of bining these elements is the very essence of the design process for highrise buildings. These binations 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 highrise building. Perhaps the most monly used system in lowto mediumrise buildings, the momentresisting frame, is characterized by linear horizontal and vertical members connected essentially rigidly at their joints. Such frames are used as a standalone system or in bination with other systems so as to provide the needed resistance to horizontal loads. In the taller of highrise buildings, the system is likely to be found inappropriate for a standalone system, this because of the difficulty in mobilizing sufficient stiffness under lateral forces. The braced frame, intrinsically stiffer than the moment –resisting frame, finds also greater application to higherrise buildings. The system is characterized by linear horizontal, vertical, and diagonal members, connected simply or rigidly at their joints. It is used monly in conjunction with other systems for taller buildings and as a standalone system in lowto mediumrise buildings. While the use of structural steel in braced frames is mon, concrete frames are more likely to be of the largerscale 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 puter programs. And again, centertocenter dimensions are used monly in the preliminary analysis. The shear wall is yet another step forward along a progression of everstiffer 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 highrise buildings, shear wall systems tend to have a relatively high aspect ratio, that is, their height tends to be large pared 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