第一单元 In terms of architecture, the structure of a building is and does much more than that. It is an inseparable part of the building form and to varying degrees is a generator of that form. Used skillfully, the building structure can establish or reinforce orders and rhythms among the architectural volumes and planes. It can be visually dominant or recessive. It can develop harmonies or conflicts. It can be both confining and emancipating. And, unfortunately in some cases, it cannot be ignored. It is physical.从建筑学方面来说，建筑结构并非仅仅如此，它是建筑风格一个不可分割的部分，并且在不同程度上体现了建筑风格。巧妙熟练地设计建筑结构能够在建筑空间和平面上建立或加强格调和韵律。它做到直观上的显性和隐形，能够发展和谐体或对照体，同时它是局限的和开放的，并且在（某些情况下）一点是不可忽略的，也就是它的实际性。
The requirement of strength means that the materials selected to resist the stresses generated by the loads and shapers of the structure(s) must be adequate. Indeed, a “factor of Safety” is usually provided so that under the anticipated loads, a given material is not stressed to a level even close to its rupture point. The material property called stiffness is considered with the requirement of strength. Stiffness is different from strength in that it directly involves how much a structure strains or deflects under load. A material that is very strong but lacking in stiffness will deform too much to be of value in resisting the forces applied. 强度要求意味着选择合适的材料来承受由荷载引起的应力和保持适当结构形状。的确，提供一个安全系数以便在预计荷载作用下，所使用的材料不会接近破坏应力。被称为刚度的材料特性需要与强度要求一起考虑。刚度不同于强度，它直接体现了结构在荷载作用下的应变
打小和变形长度。强度高，刚度低的材料在外力作用下变形过大失去使用价值。
第二单元Concrete is a man-made conglomerate stone composed of essentially four ingredients: Portland cement, water, sand, and coarse aggregate. The cement and water combine to make a paste that binds the sand and stones together. Ideally, the aggregates are graded so that the volume of paste is at a minimum, merely surrounding every piece with a thin layer. Most structural concrete is stone concrete, but structural lightweight concrete (roughly two-thirds the density, of stone concrete) is becoming increasingly popular.混凝土是一种主要由四种成分组成的人造组合石材：水泥，水，砂和粗骨料。水和水泥组合成水泥砂浆，将砂，石粘结在一起。理想情况下，级配良好使水泥浆体积最小，粘结薄薄一层。大多数结构混凝土是碎石混凝土，但轻质混凝土（碎石混凝土密度的2/3）越来越得到普及。
The compressive strength of a given concrete is a function of the quality and proportions of its constituents and the manner in which the fresh concrete is cured. (Curing is the process of hardening during which time the concrete must be prevented from “drying out”, as the presence of water is necessary for the chemical action to progress. Coarse aggregate that is hard and well graded is particularly essential for quality concrete. The most important factor governing the strength, however, is the percentage of water used in the mix. A minimum amount of water is
needed for proper hydration of the cement. Additional water is needed for handing and placing the concrete, but excess amounts cause the strength to drop markedly.
给定混凝土的抗压强度是组成成分的质量和比例以及新浇混凝土养护方法的函数。（养护是硬化过程，在这期间必须防止混凝土过干，因为水的存在是一个进行化学反应所必须的）级配良好的粗骨料对混凝土质量是至关重要的。然而，决定强度的最重要的因素是配料的含水率，最小量的水分是水泥适当水化所必须的，另外的水对操作和浇筑混凝土是必须的，但过量的水会导致强度明显下降。
第三单元The subject of mechanics of materials cuts broadly across all branches of the engineering profession with remarkably many applications. Its methods are needed by designers of offshore structures, by civil engineers in the design of bridges and buildings; by mining engineers and architectural engineers, each of whom is interested in structures; by nuclear engineers in the design of reactor components; by mechanical and chemical engineers, who rely upon the methods of this subject for the design of machinery and pressure vessels, by metallurgists, who need the fundamental concepts of this subject in order to understand how to improve existing materials further, finally, by electrical engineers, who need the methods of this subject because of the importance of the mechanical engineering phases of many portions of electrical equipment. Mechanics of materials has characteristic methods all its own. It is a
definite discipline and one of the most fundamental subjects of an engineering curriculum, standing alongside such other basic subjects as fluid mechanics, thermodynamics, and basic electricity.
材料力学这门学科广泛贯穿于工程领域，在工程领域的所有分支都有重要的应用。海洋结构设计需要应用材料力学方法。土木工程师设计桥梁和建筑也需要采矿工程师和建筑师都对结构感兴趣，原子能设计师设计反应堆构件需要，机械和化学工程师依赖这门学科方法设计机械和压力容器，冶金学家运用基本概念弄清怎样进一步完善现有的材料，最后，是电器工程师需要这些学科方法，因为电器设备的许多部分运用了工程力学的重要原理。材料力学拥有自身的特性，它是一种特定学科，并且是工程学的最基础课程之一，并肩像流体力学，热力学，基础电学这些其它的基础学科。
The behavior of a member subjected to forces depends not only on the fundamental laws of Newtonian mechanics that govern the equilibrium of the forces but also on the physical characteristics of the materials of which the member is fabricated. The necessary information regarding the latter comes from the laboratory where materials are subjected to the action of accurately known forces and the behavior of test specimens is, observed with particular regard to such phenomena as the occurrence of breaks, deformations, etc. Determination of such phenomena is a vital part of the subject, but this branch of the subject is left to other books. Here the end results of such investigations are of interest, and this course
is concerned with the analytical or mathematical part of the subject in contradistinction to experimentation. For the above reasons, it is seen that mechanics of materials is a blended science of experiment and Newtonian postulates of analytical mechanics. From the latter is borrowed the branch of the science called statics, a subject with. Which the reader of this book is presumed to be familiar ,and on which the subject of this book primarily depends.受荷载杆件的性能不仅依赖牛顿力学基本定律控制力的平衡，而且依赖组合构件材料的物理学性能。与后者有关的必要信息来自于实验室，于此，材料收到准确已知的外力作用和试验样品试件断裂，变形等现象作了特别仔细地观察。对这些现象的确定是学科中至关重要的部分，但是，这一学科分支的研究留给其他的文献。我们感兴趣的是最后的研究结果，这门课程正是关于分析和数学部分与实验的对照。通过以上原因，由此可见，材料力学是一门实验和牛顿定律分析力学相结合的综合性学科。后者是来源于一个力学的分支，一个这本书的读者认为相似，并且，这本书以此为据的学科。 第四单元When members are adequately reinforced, as in Fig.4-la, the concrete cracks at a torque equal to or only somewhat larger than in an unreinforced member. The cracks form a spiral pattern. In actuality, a great number of such spiral cracks develop at close spacing. Upon cracking, the torsional resistance of the concrete drops to about half of that of the uncracked member, the remainder being now resisted by reinforcement. This redistribution of internal resistance is reflected in the