【正文】 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。 the trusses are placed often at mechanical floors, mush to the disapproval of the designers of the mechanical systems. Nevertheless, as a costeffective structural system., the belt truss works well and will likely find continued approval from designers. Numerous studies have sought to optimize the location of these trusses, with the optimum location very dependent on the number of trusses provided. Experience would indicate, however, that the location of these trusses is provided by the optimization of mechanical systems and by aesthetic considerations, as the economics of the structural system is not highly sensitive to belt truss location.TubeinTube StructuresThe tubular framing system mobilizes every column in the exterior wall in resisting overturning and shearing forces. The term ‘tubeintube’ is largely selfexplanatory in that a second ring of columns, the ring surrounding the central service core of the building, is used as an inner framed or braced tube. The purpose of the second tube is to increase resistance to over turning and to increase lateral stiffness. The tubes need not be of the same character。附件2:外文翻譯Structural systems to resist Lateral loadsCommonly Used Structural SystemsWith loads measured in tens of thousands kips, there is little room in the design of highrise buildings for excessively plex thoughts. Indeed, the better highrise buildings carry the universal traits of simplicity of thought and clarity of expression.It does not follow that there is no room for grand thoughts. Indeed, it is with such grand thoughts that the new family of highrise buildings has evolved. Perhaps more important, the new concepts of but a few years ago have bee mon place in today’s technology.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:Momentresisting frames.Braced frames, including eccentrically braced frames.Shear walls, including steel plate shear walls.Tubeintube structures.Tubeintube structures.Coreinteractive structures.Cellular 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. There 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 gr