【正文】 in the inner ring of columns may be as high, or even higher, than the axial stresses in the outer ring. This seeming anomaly is associated with differences in the shearing ponent of stiffness between the two sys tems. This is easiest to understand where the inner tube is conceived as a braced (, shear stiff) tube while the outer tube is conceived as a framed (, shearflexible) tube. Core Interactive Structures Core interactive structures are a special case of a tubeintube wherein the two tubes are coupled together with some form of three dimensional space frame. Indeed, the system is used often wherein the shear stiffness of the outer tube is zero. The United States Steel Building, P ittsburgh, 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 wou ld 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。 4． 筒中框架。這并不是說富于想象力的結(jié)構(gòu)設(shè)計(jì)就能夠創(chuàng)造出偉大建筑。對于較高的高層建筑，可能會(huì)發(fā)現(xiàn) 該本系不宜作為獨(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。另外，初步分析中常用中心距尺寸。這種體系實(shí)際上比鋼支撐經(jīng)濟(jì)，對于使剪切荷載由位于地面正上方區(qū)域內(nèi)比較高的樓層向下移特別有效。 這種最先在航天器結(jié)構(gòu)中研究的剪力滯后出現(xiàn)后，對筒體結(jié)構(gòu)的剛度是一個(gè)很大的限制。“筒中筒”這個(gè)名字顧名思義就是在建筑物的核心承重部分又被包圍了第二層的一系列柱子，它們 被當(dāng)作是框架和支撐筒來使用。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。當(dāng)然，外柱也傳遞相同的軸向力，這種軸向力低于作用在整個(gè)柱子高度的側(cè)向荷載，因?yàn)檫@個(gè)體系的剪切 剛度接近于零。 在建筑的頂部布置了一個(gè)空間桁架構(gòu)成的“帽式”結(jié)構(gòu)。在第 50 層柱子會(huì)壓縮 94 毫米，小于它未受壓的長度。 主要的結(jié)構(gòu)工作都集中在布置中。 由于外筒的剪切剛度在建筑的底部接近零，整個(gè)建筑基本上由兩個(gè)鋼板筒來支持。美國電話電報(bào)總局就是一個(gè)布置交互式構(gòu)件的生動(dòng)例子。 核心交互式結(jié)構(gòu)： 核心交互式結(jié)構(gòu)屬于兩個(gè)筒與某些形式的三維空間框架相配合的筒中筒特殊情況。這些筒體不是同樣的功能，也就是說，有些筒體是結(jié)構(gòu)的，而有些筒體是用來支撐的。設(shè)計(jì)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。 由于這些墻內(nèi)必然出同一些大孔，使得剪力墻體系分析變得錯(cuò)綜復(fù)雜。該體系的特點(diǎn)是具有相當(dāng)薄的，通常是（而不總是）混凝土的構(gòu)件，這種構(gòu)件既可提供結(jié)構(gòu)強(qiáng)度，又可提供建筑物功能上的分隔。所謂的門架法分析或懸臂法分析在當(dāng)今的技術(shù)中無一席之地，由于柱梁節(jié)點(diǎn)固有柔性，并且由于初步設(shè)計(jì)應(yīng)該力求突出體系的弱點(diǎn)，所以在初析中使用框架的中心距尺寸設(shè)計(jì)是司空慣的。無論如何，要想創(chuàng)造出高層建筑真正非凡的設(shè)計(jì)，兩者都需要最好的。 6． 核心交互結(jié)構(gòu)。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)。 analysis by the so called portal method of th e cantilever method has no place in today’s technology. Because of the intrinsic flexibility of the column/girder intersection, and because preliminary designs should aim to highlight weaknesses of systems, it is not unusual to use center tocenter dimensions for the frame in the preliminary analysis. Of course, in the latter phases of design, a realistic appraisal in joint deformation is essential. Braced Frames The braced frame, intrinsically stiffer than the moment –resisting frame, finds also greater application to higher rise 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