【正文】 ot be in conflict in terms of form. For example, a linear function demands a linear structure, and therefore it would be improper to roof a bowling alley with a dome. Similarly, a theater must have large, unobstructed spans but a fine restaurant probably should not. Stated simply, the structure must be appropriate to the function it is to shelter. [9] Second, the structure must be fireresistant. It is obvious that the structural system must be able to maintain its integrity at least until the occupants are safely out. Building codes specify the number of hours for which certain parts of a building must resist the heat without collapse. The structural materials used for those elements must be inherently fireresistant or be adequately protected by fireproofing materials. The degree of fire resistance to be provided will depend upon a number of items, including the use and occupancy load of the space, its dimensions, and the location of the building. [10] Third, the structure should integrate well with the building39。s structure, because the untrained viewer cannot distinguish between real and perceived safety. 第 4 頁 Reading Material A Structural Planning and design The building designer needs to understand the behavior of physical structures under load. An ability to intuit or feel structural behavior is possessed by those having much experience involving structural analysis, both qualitative and quantitative. The consequent knowledge of how forces, stresses, and deformations build up in different materials and shapes is vital to the development of this ” sense” 。 those due to gravitational attraction and those resulting from other natural causes and elements. Gravity loads can be further classified into two groups: live load and dead load. Building live loads include people and most movable objects within the structure or on top of it. Snow is a live load. So is a grand piano, a safe, or a water bed. Appendix O provides some typically remended live loads for various types of occupancy within building structures. Research bears out that these figures represent probable maximum values for live loads during the lifetime of a structure. Such loads are seldom realized. What is more likely is an unexpected change in the use of the space. One can sense the problems that might result if an abandoned school is purchased for use as a warehouse (to store bowling balls). Dead loads, on the other hand, generally include the immovable objects in a building. The walls (both interior and exterior), floors, mechanical and electrical equipment, and the structural elements themselves are examples of dead loads. The snow map of Appendix N gives the maximum snow load that can reasonably be expected in various parts of the United States. Like the liveload values, such large snowfalls seldom occur. Nevertheless, we must design for some level of probability and should not fet such occurrences as the more than500millimeter snowfall that hit the southeastern United States in 1974, resulting in many small building failures. Natural forces not due to gravity that act on buildings are provided by wind and earthquakes. Wind load is a lateral load that varies in intensity with height. (Hurricanes and tornadoes present special design problems, and local building codes often require certain types of resistive construction.) A probable wind pressure map is given in Appendix 第 7 頁 N. Earthquakes are also treated as lateral loads (at least for preliminary design purposes), but it is well known that buildings in earthquakes are subjected to vertical forces as well. Design methods are not fully developed for disaster loadings such as tornadoes and earthquakes, and research continues in these areas. One final type of load is an impact load, usually due to moving equipment, which occurs within or on the structure. Most structural materials can withstand a sudden and temporary load of higher magnitude than a load that is applied slowly. For this reason, the specified permissible stress magnitudes are substantially increased when such loads govern the design. No permanent damage is done by moderate impact load provided that it does not occur repeatedly. (An earthquake is a good example of a severe and repeating impact load.) All the tables and maps referred to in this text, as part of the appendices, provide rough data onl