【正文】 assing 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 pression 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 ATamp。T headquarters is an example of an astonishing array of interactive elements: 1. The structural system is 94 ft () wide, 196ft() long, and 601ft () high. 2. Two inner tubes are provided, each 31ft() by 40 ft (), centered 90 ft () 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 momentresisting frame, but with zero shear stiffness for the center50ft () of each of the long sides. 6. A spacetruss hat structure is provided at the top of the building. 7. A similar space truss is located near the bottom of the building 8. The entire assembly is laterally supported at the base on twin steelplate tubes, because the shear stiffness of the outer tube goes to zero at the base of the building. Cellular structures A 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 unmon 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/E For buildings of 12 ft () floortofloor distances and an average pressive stress of 15 ksi (138MPa), the shortening of a column under load is 15 (12)(12)/29,000 or () per story. At 50 stories, the column will have shortened to 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 prestress the lower height columns so as to reconcile the differential deflections of columns in close proximity with the posttensioning of the shorter column simulating the weight to be added on to adjacent, higher columns. 結(jié)構(gòu)系統(tǒng)抵抗橫向荷載 常用的結(jié)構(gòu)體系 與負(fù)載檢測成千上萬 kips ，很少有房的設(shè)計，高層建筑的過于復(fù)雜的想法。事實(shí)上，更好的高層建筑中的普遍特征簡單的思路和清晰的表達(dá)。 但這并不意味著沒有余地大的想法。事實(shí)上，這是與這種大的思想，新的家庭高層建筑的發(fā)展。也許更重要的是，新概念，但在幾年前已經(jīng)司空見慣在當(dāng)今的技術(shù)。 忽略了一些概念，有關(guān)的材料嚴(yán)格的建設(shè)，最常用的結(jié)構(gòu)系統(tǒng)用于高層建筑可歸納如下： 1 .矩抗張。 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 .筒中筒結(jié)構(gòu)。 5 .筒中筒結(jié)構(gòu)。 6 .核心的互動結(jié)構(gòu)。 7 .蜂窩或捆綁管系統(tǒng)。 特別是最近的趨勢更為復(fù)雜的形式，但在反應(yīng)還需要增加剛度抵制軍隊從風(fēng)和地震，最高層建筑結(jié)構(gòu)體系已經(jīng)建立起來的組合 框架，支撐 bents ，剪力墻，和相關(guān)系統(tǒng)。此外，在高建筑物，多數(shù)是由互動元素在三維陣列。 結(jié)合的