C5It is this devintion in the composition of a reinforced concerte section from the bornogeneity of standard wood or steel sections that requires a modified approach to the basic principles of sctuctural design. The two components of the beterogeneous reinforced concrete section are to be so arranged and proportioned that optmal use is made of the materials involved. This is possible because concrete can easily be given any desired shape by placing and compacting the wet mixture of the constituent ingredients into suitable forms in which the plastic mass hardens. If the various ingredients are properly proportioned, the finished product becomes strong, durable,and ,in combination with the reinforcing bars, adaptable for use as main members of any structural system.由于钢筋混凝土截面在均质性上与标准的木材或钢的截面存在着差异，因此，需要对结构设计的基本原理进行修改。将钢筋混凝土这种非均质截面的两种组成部分按一定比例适当布置，可以最好地利用这两种材料。这一要求是可以达到的，因混凝土由配料搅拌成湿拌混合物，经过振捣并凝固硬化，可以做成任何一种需要的形状。如果拌制混凝土的各种材料配合比恰当，则混凝土制成品的强度较高，经久耐用，配置钢筋后，可以作为任何结构体系的主要构件。The techniques necessary for placing concrete depend on the type of member to be cast: that is ,whether it is a column, a beam, a wall, a slab, a foundation, a mass concrete dam, or an extension of previously placed and hardened concrete. For beams, columns, and walls ,the forms should be well oiled after cleaning, and the reinforcement should be cleard of rust and other harmful materials. In foundations, the earth should be compacted and thoroughly moistened to about 6 in , in depth to avoid absorption of the moisture present in the wet concrete. Concrete should always be placed in horizontal layers which are compacted by means of high-frequency power-driven vibrators of either the immersion or external type, as the case requires, unless it is placed by pumping. It must be kept in mind, however ,that overvibration can be harmful since it could cause segregation of the aggregate and bleeding of the concrete.浇筑混凝土所需的技术取决于即将浇筑的构件类型，例如：柱、梁、墙、板、基础，大体积混凝土水坝或者继续延长已浇筑完毕并且已经凝固的混凝土等。对于梁柱强等构件，当模板清理干净后应该在上面涂油，钢筋表面的铁锈及其他的有害物质也应该清除干净。浇筑基础前，应将底部土夯实并用水浸湿 6 英才，以免土壤从新浇混凝土中吸收水分。一般情况下，除了使用混凝土泵浇筑外，混凝土都应在水平方向分层浇筑，并使用插入式或表面式高频电动振捣器振实。必须记住，过分的振捣将导致骨料分离和混凝土泌水等现象，因此是有害的。C4 Almost any reasonable structure can be built and safely supported if there is unlimited financing. Unfortunately, in the real situation this is seldom , if ever, the case, and the foundation engineer has the dilemma of making a decision under much less than the ideal condition. Also, even though the mistake may be buried, the results from the error are not and can show up relatively soon-and probably before any statute of limitations expires. The are reported cases where the foundation defects (such as cracked walls or broken mechanical fixtures) have shown up years later-also cases where the defects have shown up either during construction of the superstructure or immediately thereafter.几乎任何合理的结构物只要经费不受限制，总是可以建造的很安全。不巧的是，在实际中这种情况如果有的话，也是非常少见的，基础工程师总是出在比理想情况差很多的窘境下作出决定。此外，即使错误可以被掩埋，但错误造成的后果不会被掩埋，并且能够较快地显示出来而且可能是在一些新法规所规定的期限到期之前出现失效。已经有过这样事例报道，基础的缺陷（例如引起墙体开裂或机械装置损坏）是在几年之后才显示出来的，但是在有的事例中，基础的缺陷是在上不结构施工中或紧随其后显示出来的。Since the substructure is buried, of is beneath the superstructure, in such a configuration that access will be difficult should foundation inadequacies develop after the superstructure is in place, it is common practice to be conservative. A one or two percent overdesign in these areas produces a larger potential investment retum than in the superstructure.由于下部结构是埋藏在地下或者是在上部结构的下面，所以在这样的部位，当上部结构就位之后，如果基础中的缺陷扩展，那么检修将很困难，因此通常在设计上都比较保守。在这些部位保守设计 1%或 2%则会在投资上取得比在上部结构中更大的潜在收益。C3Now our buildings are fashionable, speculative, and either of geometric and sculptured intricacy, or anonymous and componented. There is a multitude of structural gymnastics and immature material innovations. At one end of the spectrum the public buildings, and universities and prestige commercial buildings (all very self-consciously designed) and at the other, the component assembled buildings, providing the social needs of schools, housing, offices, work and industrial buildings.现在我们的建筑有的新颖时髦，有的还属于探索性的，有呈现几何图形的，有精细雕刻的，也有毫无特色的，以及组建装配的。形形色色的结构绝技与有待完善的用料革新同时并存。一端是公共建筑、大专院校和名声显赫的商业大厦（设计上全都是各有特色） ，另一端是组件装配的建筑，为社会提供诸如学校、住宅、办公楼、厂房已经工业建筑等需要。This dichotomy of basic approach to design and construction remains with us, and highlights some of the disparities of the social and technical goals of the times. We have in the world of building reached one of the great divides-straddled between contradictions:Simple tent enclosures high indoor performance Solid walls light frameworks Privacy communityLow density high density Vehicle pedestrianIn this great dilemma and confusion of interests we must now try to get our design and performance priorities right.我们仍然面临着设计和施工基本方法的这种局面。这一局面突出了我们这个社会在技术和目标之间的差异。在建筑领域中，我们已经达到了一个分水岭处于在两难矛盾之中：简便住所 高性能住所 坚固性实心墙体 轻便型框架结构 保护隐私 利用交流低密度 高密度 车辆用到 人行通道 在这种进退两难的混乱中，我们必须优先考虑设计和使用性能两个重点之间的关系。C2Engineers must be willing to undergo a conti