【正文】 (從根本上說(shuō) ,是以鐵為主要成分并含有少量碳元素的合金 ),直到出現(xiàn)能夠限制其特殊用途 (如制造刀刃 )的費(fèi)勞力的鑄造方法 ,才被鑄造出來(lái)。 結(jié)構(gòu)鋼和混凝土的使用是傳統(tǒng)的施工方式產(chǎn)生的主要變化。另一種更常用的方法是將鋼筋置于與成品構(gòu)件外形相符的模板底部 ,然后在鋼筋周?chē)鷿沧⒒炷痢? 7 預(yù)應(yīng)力混凝土是鋼筋混凝土的一種改良方式。因此它們可以在拉力與壓力同時(shí)存在的條件下共同工作。 磚和磚之間是由砂漿或者焦油狀的瀝青或其它粘合物 粘結(jié)在一起。這樣就可以依據(jù)全局設(shè)計(jì)方案，確定并解決各分體系的相互影響以及設(shè)計(jì)難題。 these preliminarylevel decisions may also result in feedback that calls for refinement or even major change in schematic concepts. 2 When the designer and the client are satisfied with the feasibility of a design proposal at the preliminary level, it means that the basic problems of overall design are solved and details are not likely to produce major change .The focus shifts again ,and the design process moves into the final level .At this stage the emphasis will be on the detailed development of all subsystem specifics . Here the role of specialists from various fields, including structural engineering, is much larger, since all detail of the preliminary design must be worked out. Decisions made at this level may produce feedback into Level II that will result in changes. However, if Levels I and II are handled with insight, the relationship between the overall decisions, made at the schematic and preliminary levels, and the specifics of the final level should be such that gross redesign is not in question, Rather, the entire process should be one of moving in an evolutionary fashion from creation and refinement (or modification) of the more general properties of a totalsystem design concept, to the fleshing out of requisite elements and details. To summarize: At Level I, the architect must first establish, in conceptual terms, the overall spaceform feasibility of basic schematic options. At this stage, collaboration with specialists can be helpful, but only if in the form of overall thinking. At Level II, the architect must be able to identify the major subsystem requirements implied by the scheme and substantial their interactive feasibility by approximating key ponent properties .That is, the properties of major subsystems need be worked out only in sufficient depth to very the inherent patibility of their basic formrelated and behavioral interaction . This will mean a somewhat more specific form of collaboration with specialists then that in level I .At level III ,the architect and the specific form of collaboration with specialists then that providing for all of the elemental design specifics required to produce biddable construction documents . Of course this success es from the development of the Structural Material. The principal construction materials of