【導(dǎo)讀】確實(shí)，較好的高層建筑普遍具有構(gòu)思簡單、表現(xiàn)明晰的特點(diǎn)。這并不是說沒有進(jìn)行宏觀構(gòu)思的余地。今天的技術(shù)中已經(jīng)變的一般了。支撐框架，包括偏心支撐框架。剪力墻，包括鋼板剪力墻。而且，對于那些較高的建筑物來說，大多數(shù)都是由交互式構(gòu)件組成三。其結(jié)合方式需要在。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)該體系不宜作為獨(dú)。立體系，這是因?yàn)樵趥?cè)向力的作用下難以調(diào)動(dòng)足夠的剛度。的中心距尺寸設(shè)計(jì)是司空見慣的。尤其引人關(guān)注的是，在強(qiáng)震區(qū)使用偏心支撐框架。比，其高度偏大。不管應(yīng)用哪種方法，都必須考慮剪力滯后的影響。開發(fā)出了很多的技術(shù)，用以減小剪力滯后，這其中最有名的就是桁架的應(yīng)用。由于其最佳位置正。配置第二層柱的目的是增強(qiáng)抗傾覆能力和增大側(cè)移剛。心壓力就會與中心筒柱的軸心壓力相差甚遠(yuǎn)，而且穩(wěn)定的大于中心筒。這種反常的現(xiàn)象是由于兩種體系中的剪切構(gòu)件的剛度不同。者說是剪切彈性的）筒。

　　

【正文】 e wherein the two tubes are coupled together with some form of threedimensional 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 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 zoo. 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: The structural system is 94 ft () wide, 196ft() long, and 601ft() high. Two inner tubes are provided, each 32ft() by 40 ft() centered 90 ft() apart in the long direction of the building. The inner tubes are braced in the short direction, but with zero shear stiffness in the long direction. A single outer tube is supplied, which encircles the building perimeter. The outer tube is a momentresisting frame, but with zero shear stiffness for the center50ft () of each of the long sides. A spacetruss hat structure is provided at the top of the building. A similar space truss is located near the bottom of the building. 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 ??? EfL For building of 12ft() floortofloor distances and an average pressive stress of 15ksi(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.