【正文】 框架結(jié)構(gòu) 在建筑物結(jié)構(gòu)設(shè)計中，用于抵抗豎向和水平荷載的 框架結(jié)構(gòu)，常作為一個重要且標準的型式而被采用。它適用于低層、多層建筑物，亦可用于 70100 層高的高層建筑物。同剪力墻結(jié)構(gòu)相比，這種結(jié)構(gòu)更適合在建筑物的內(nèi)部或者外圍的墻體上開設(shè)矩形孔洞。同時它還能充分利用建筑物內(nèi)在任何情況下都要采用的梁和柱的剛度，但當(dāng)柱子與梁剛性連接時，通過框架受彎來抵抗水平和豎向荷載會使這些柱子的承載能力變得更大。 大多情況下，框架的剛度不如剪力墻，因此對于細長的建筑物將會出現(xiàn)過度變形。但正是因為其柔性，使得其與剪力墻結(jié)構(gòu)相比具有更大的延性，因而地震荷載下不易發(fā)生事故。例如，如果框架局部 出現(xiàn)超應(yīng)力時，那么其延性就會允許整個結(jié)構(gòu)出現(xiàn)倒塌事故。因此，框架結(jié)構(gòu)常被視為最好的高層抗震結(jié)構(gòu)。另一方面，設(shè)計得好的剪力墻結(jié)構(gòu)也不可能倒塌。 對于混凝土框架結(jié)構(gòu)，還存在較大的分歧。的確。如果在混凝土框架設(shè)計時不進行特殊的延性設(shè)計，那么他將很難承受比設(shè)計標準值大很多倍的地震荷載的沖擊。因此，很多人認為它不具備鋼框架所具備的超載能力。不過最新的研究 i和實驗表明，當(dāng)混凝土中放入充分的鋼箍和節(jié)點鋼筋時 ，混凝土框架框架也能表現(xiàn)出很好的延性。新建筑規(guī)范對所謂延性混凝土框架有專門的規(guī)定。然而，這些規(guī)范往往要求在框架的某 處增設(shè)過多的鋼筋，這就增加了施工的難度。盡管這樣，混凝土框架設(shè)計還是具備既經(jīng)濟又實用的特性。 當(dāng)然，還可以在建筑結(jié)構(gòu)設(shè)計中，將框架結(jié)構(gòu)和剪力墻結(jié)構(gòu)結(jié)合起來使用。例如，在房屋建筑上使用框架，而在另一方向上可以使用剪力墻。 結(jié)論 以上所述就是高層建筑最普通的結(jié)構(gòu)形式。在設(shè)計過程中，應(yīng)盡可能經(jīng)濟實用地選擇合理的形式。 Underground Space Utilization The rapid growth of world civilization will have a significant impact on the way humans live in the future. As the global population increases and more countries demand a higher standard of living, the difficulty of doing this is pounded by three broad trends: the conversion of agricultural land to development uses。 the increasing urbanization of the world`s population。 and growing concern for the maintenance and improvement of the environment, especially regarding global warming and the impact of population growth. Underground space utilization, as this chapter describes, offers opportunities for helping address these trends. By moving certain facilities and function underground, surface land in urban areas can be used more effectively , thus freeing space for agricultural and recreational purpose. Similarly, the use of terraced earth sheltered housing. Using underground space also enables humans to live more fortably in densely populated areas while improving the quality of live. On an urban or local level, the use of underground facilities is rising to acmodate the plex demands of today`s society while improving the environment . For example, both urban and rural areas are requiring improved transportation, utility, and recreational services. The state of traffic congestion in many urban areas of the world is at a critical level for the support of basic human living, and it is difficult if not impossible to add new infrastructure at ground level without causing an unacceptable deterioration of the surface environment or an unacceptable relocation of existing land uses and neighborhoods. On a national level in countries around the world, global trends are causing the creation and extension of mining developments and oil or gas recovery at greater depths and in more inaccessible or sensitive locations. Three trends have also led to the developments of improved designs for energy generation and storage systems as well as national facilities for dealing with hazardous waste (including chemical, biological, and radioactive waste ), and improved highspeed national transportation systems .All these developments involve use of the underground . Land Use Pressures Placing facilities underground is a promising method for helping ease land use pressures caused by the growth and urbanization of the world`s population. Although the average population density in the world is not large, the distribution of population is very uneven. A map of population density in the world is not large ,areas of the world are essentially uninhabited . These areas are for the most part deserts ,mountainous regions, or regions of severe cold that do not easily support human habitation. If one examines China ,for example ,the average population density is approximately 100 persons per square kilometer, but the vat majority of the one billionplus population lives on less than 20 percent of the land area. this is the fertile land that can support food production. However, due to population growth, urbanization, and economic growth, this same land must now support extensive transportation systems, industrial and mercial development, and increasing demands for housing, As the population and economy grow, the land available for agriculture shrinks, and the problems of transporting food and raw materials to an urban population increase. By the year 2020 it is estimated that 70 percent of the world`s population will inhabit urban areas. The same trend are evident in Japan, where approximately 80 percent of the land area is mountainous,90 percent of the population lives on the coastal plains, and economic development is concentrated in relatively few economic development is concentrated in relatively few economic centers .The flatlying land is generally the most fertile and is historically the region of settlement . Other factors adding to population density include the traditional building style , which is lowrise , and Japanese law that contain strong provisions for maintenance of access to sunlight .Also ,to retain domestic food production capability , the Japanese government has protected agricultural land from development. The bination of these historical and political factors together with a strong migration of businesses and individuals to the economic centers has created enormous land use pressure. The result is an astronomically high cost of land in city centers (as high as US $500,00 per square meter) and difficulty in an providing housing, transportation, and utility services for the population. Typical business employees cannot afford to live near the city center where they work and may have to mute one to two hours each way from an affordable area. To service the expanding metropolitan area, public agencies must upgrade roads and build new transit lines and utilizes. Land costs for such work are so high that in central Tokyo, the cost of land may represent over 95 percent of the total cost of a project. The problem of land use pressures and related economi