【正文】 e of the second tube is to inc rease resistance to over turning and to increase lateral stiffness. The tubes need not be of the same character。 Structural Systems to resist lateral loads 抗側(cè)向荷載的結(jié)構(gòu)體系 Structural Systems to resist lateral loads Commonly Used structural Systems With loads measured in tens of thousands kips, there is little room in the design of highrise buildings for exc essively plex thoughts. Indeed, the better high rise 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 high rise buildings has evolved. Perhaps more important, the new concepts of but a few years ago have bee monplace in today’ s technology. Omitting some concepts that are related strictly to the materials of construction, the most monly used structural systems used in high rise buildings can be categorized as follows: 1. Momentresisting frames. 2. Braced frames, including eccentrically braced frames. 3. Shear walls, including steel plate shear walls. 4. Tubeintube structures. 5. Tubeintube structures. 6. Coreinteractive structures. 7. 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 buildin gs 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 three dimensional arrays. The method of bining these elements is the very essence of the design process for high rise buildings. These binations need evolve in response to environmental, functional, and cost considerations so as to provide efficient structures that provoke the architectural development t o 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, no t 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 high rise building. While prehensive discussions of these seven systems are generally available in the literature, further discussion is warranted here .The essence of the design process is distributed throughout the discussion. MomentResisting Frames Perhaps the most monly used system in low to mediumrise build ings, the momentresisting frame, is characterized by linear horizontal and vertical members connected essentially rigidly at their joints. Such frames are used as a stand alone system or in bination with other systems so as to provide the needed resist ance to horizontal loads. In the taller of high rise buildings, the system is likely to be found inappropriate for a stand alone system, this because of the difficulty in mobilizing sufficient stiffness under lateral forces. Analysis can be acplished by STRESS, STRUDL, or a host of other appropriate puter programs。 analysis by the so called portal method of the cantilever method has no place in today’s technology. Because of the intrinsic flexibility of the column/girder intersection, and because pre liminary designs should aim to highlight weaknesses of systems, it is not unusual to use center tocenter dimensions for th