LESSON 15 High-Rise Buildings,Background Knowledge,本单元涉及的课程：高层建筑结构 高层建筑经过长期的发展，其主要材料为钢材、钢筋混凝土，主要结构体系为框架结构、剪力墙结构体系、框架剪力墙结构(筒体)体系、筒体结构和巨型结构等。 本课文主要涉及了高层建筑的受力特点 、设计理念等。,Part 1 The First Development of Tall Building,Plan for War Office, England, 1857,New Words and Expression of Part 1,Paragraph 1 shaft n. 电梯井 the overturning moment 倾覆力矩；倾翻力矩 the shear deflection 剪力变形,It is difficult to define a high-rise building. A mid-rise building generally less than 10 stories (28m). Thus a high-rise building is one that has at least 10 stories or more. Although the basic principles of vertical and horizontal subsystem design remain the same for mid-, or high-rise buildings, when a building gets high the vertical subsystems become a controlling problem for two reasons.,Paragraph 1 (the vertical subsystems is controlling problem for high-rise buildings),Higher vertical loads will require larger columns, walls, and shafts. But, more significantly, the overturning moment and the shear deflections produced by lateral forces are much larger and must be carefully provided for.,Paragraph 1 (the vertical subsystems is controlling problem for high-rise buildings),The vertical subsystems in a high-rise building transmit accumulated gravity load from story to story, thus requiring larger column or wall sections to support such loading. In addition, these same vertical subsystems must transmit lateral loads, such as wind or seismic actions, to the foundations.,Paragraph 2 (lateral load effects applied on the vertical subsystems ),However, in contrast to vertical load, lateral load effects on buildings are not linear and increase rapidly with increase in height.,For example, under wind load, the overturning moment at the base of a building varies approximately as the square of the height of the building, and the lateral deflection at the top of a building may vary as the fourth power of building height, other things being equal. Earthquake produces an even more pronounced effect.,Paragraph 2 (lateral load effects applied on the vertical subsystems ),在风荷载作用下，建筑基础处的倾覆力矩大致是随建筑高度的二次方变化，建筑物顶部的水平挠度随建筑高度的四次方变化。,power n. 幂 the power of four, the fourth power 四次方,When the structure for a mid-rise building is designed for dead and live load, it is almost an inherent property that the columns, walls, and stair or elevator shafts can carry most of the horizontal forces. The problem is primarily one of shear resistance. .,Paragraph 3 (shear resistance of a mid-rise building ),问题主要是剪力抵抗。,Moderate additional bracing for rigid frames in “short” buildings can easily be provided by filling certain panels (or even all panels) without increasing the sizes of the columns and girders otherwise required for vertical loads.,additional bracing 附加的支撑,Paragraph 3 (shear resistance of a mid-rise building ),如无特殊竖向承载需要，（矮建筑中）框架体系无需加大柱和梁的尺寸，只通过设置某些填充墙板（或全部填充墙）就可以轻易地实现中等强度的附加支撑（以抵抗剪力）。,Unfortunately, this is not so for high rise buildings because the problem is primarily resistance to moment and deflection rather than shear alone. Special structural arrangements will often have to be made and additional structural material is always required for the columns, girders, walls, and slabs in order to make a high rise building sufficiently resistant to much higher lateral loads and deformations,Paragraph 4 (Resistance to moment and deflection，and shear for high-rise buildings ),为了使高层建筑对更高的水平荷载与变形有足够的抵抗能力，常常需要做特殊的结构布置、且柱、主梁、墙、板需要额外的结构材料。,As previously mentioned, the quantity of structural material required per square foot of floor of a high-rise building is in excess of that required for a low rise building. The vertical components carrying the gravity load, such as walls, columns, and shafts, will need to be strengthened over the full height of the building.,Paragraph 5 (how the weight of structural steel increases as the number of stories increases),in excess of 超过；较为多,But quantity of materials required for resisting lateral forces is even more significant. The graph shown in Fig. 25. 1 illustrates how the weight of structural steel in pounds per square feet of floor increases as the number of stories increases from 1 up to 100.,图25.1说明了当楼层从1增加到100时，楼板每平方英尺结构用钢重量的增长。,Paragraph 5 (how the weight of structural steel increases as the number of stories increases),Note that by using optimum structural systems with suitable width and arrangement, the additional material required for lateral force resistance can be controlled such that, even for buildings of 100 stories, the total structural weight of steel may be only about 34 pounds per square foot, whereas it is noted previously, some buildings quite a bit shorter require much more structural steel.,Paragraph 5 (how the weight of structural steel increases as the number of stories increases),现在意识到，经过合适的尺度和布局进行结构体系优化，抵抗水平力所需要的额外材料可以控制到如下程度：即使100层，结构钢材总重也可以是34磅每平方英尺，然而，以前认为某些建筑中缺少相当多的结构钢材。,Curve A in Fig. 25.1 represents the average unit weight of a conventional frame with increasing numbe