痛苦。
261. 266. The life span and response of brakes have been vastly improved. .制动器的使用寿命和灵敏度有了很大提高。
262. Modern tires have been developed with tread patterns design for draining. 新式轮胎的胎面带有排水的花纹。
263. The importance of safety in all modes of transportation, especially highway safety is well recognized. 对所有现代运输的安全重要性，特别是高速公路的安全性，大家已经形成了共识。
264. Today, engineers agree that proper embankment construction requires that the soil be spread in layers, moistured or dried to something near an optimum moisture content, and compacted. 现在，工程师一致认为合理的路堤施工要求土壤分层摊铺，洒湿或晾干至接近最佳含水量并压实。
265. The obligations that a contractor accepts when he submits a tender are determined by the form of the invitation to tender. 承包人在提交标书时他所应负的责任是邀标书中规定的。 266. Forces that might pull the structure around must have sufficient strength to counterbalance that weight. 建筑物四周是受力必须与反方向的力平衡。
267. Since the structures designed by civil engineers are intended to be stationary or stable, these forces must be kept in balance. 土木工程师设计的目的就是使建筑物的结构稳定，所以建筑物上的各方力都必须平衡。
268. Bridges, tunnels and skyscrapers under construction can also be dangerous places to work. 在桥梁、隧道、摩天大楼、地下建筑中工作也同样存在危险。
269. Many of these great buildings built in earlier ages were poorly constructed and sometimes collapsed with considerable loss of life. 许多早期的建筑物建筑水平不高，有时甚至会倒塌造成巨大的人员伤亡。
270. Highway pavements are divided into two main categories: rigid pavements and flexible pavements. 公路路面分为两个主要类别：刚性路面和柔性路面。
271. Flexible pavements are further divided into three subgroups: high type, intermediate type.
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And low type. 柔性路面进一步分为三小类：高级，中级和低级路面。
272. Traffic loads are transferred by the wearing surface to the underlying supporting materials through the interlocking of aggregates, the frictional effect of granular materials, and the cohesion of the fine materials. 交通荷载经由磨耗层转移到下卧支撑材料上，这是通过集料的嵌锁作用，粒料的磨擦作用和细料的粘结作用。
273. High-type pavements have wearing surfaces that adequately support the expected traffic load without visible distress due to fatigue and are not susceptible to weather conditions. 高级路面的磨耗层能有效承担预期的车辆荷载，而不会出现明显的疲劳破坏，并且不易受到天气的影响。
274. The Portland cement concrete commonly used for rigid pavements consists of Portland cement, coarse aggregate, fine aggregate, and water. 普遍用于刚性路面的波特兰水泥混凝土是由波特兰水泥，粗料，细料和水组成。
275. Rigid highway pavements can be divided into three general types: plain concrete pavements, simply reinforced concrete pavements, and continuously reinforced concrete pavements. 刚性路面可以分成三大类：素混凝土路面，普通钢筋混凝土路面和连续配筋混凝土路面。 276. The surface course of a road pavement should be capable of withstanding high tire pressure, resisting the abrasive forces due to traffic, providing a skid-resistant driving surface, and preventing the penetration of surface water into the underlying layers. 高级路面的磨耗层应该能够承受高的轮胎压力，能够抵抗车辆的摩擦力，提供良好的抗滑表面，并能阻止表面水渗入下承层。
277. But traffic patterns on the arterials are complex, since the road way must carry two through movements and accommodate four left turns, two of which must use the inside lanes of the arterial or separate turning lanes. 但是干线上的交通运行却很复杂，因为车道必须承担两个方向的直行交通并容纳四个左转弯，其中两个必须使用干线的内侧车道或者专用的转弯车道。
278. Flow on the freeway is uninterrupted, except for problems that may develop at points where ramp traffic enters or leaves. 除了在匝道交通进入或离开的地点可能存在问题外，高速公
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路上的交通流不受干扰。
279. Advance signing for exits of freeways should be uniform. 出口处的预告标志应该是统一的。
280. Long radius horizontal curves and long vertical curves will result in the higher running speed. 大半径平曲线和竖曲线将导致更高的行车速度。
281. A level is only used for measuring the vertical heights of objects. 水准仪只用于测量物体的垂直高度。
282. In a prestressed concrete beam, a compressive force prestresses concrete prior to the application of loads. 在预应力混凝土梁中，负载施加之前就有压力预先增强混凝土。 283. Cracking is irrecoverable in reinforced concrete. 开裂在钢筋混凝土中是不可逆的。 284. The steel in reinforced concrete member does not prevent the concrete from cracking. 钢筋混凝土构件中的钢不会阻止混凝土开裂。
285. The normal steel does not exert any force of its own on the member, contrary to the action of prestressing steel. 普通钢筋不会施加任何自身的力于构件之上，这与预应力钢筋相反。 286. The geometry of prestressed section is usually composed of flanged sections with thin webs. 预应力截面的几何设计通常是由薄腹翼边梁组成。
287. Many scientists contribute a great deal to art and science of design of prestressed concrete. 很多科学家对于预应力混凝土的设计原理做出了很多贡献。
288. The extensive use of prestressed structures has been due in no small measures to the advances in the technology. 预应力结构的广泛使用很大程度上归功于技术的进步。 289. They argue that there is no such thing as certainty, either of failure or safety of a structure but only a probability of failure or a probability of safety. 他们讨论认为，无论是对于结构的破坏还是结构的安全，不存在一种确定性，存在的仅仅是一种破坏和安全的可能性。 290. This traditional design is called elastic design because allowable stress intensities are chosen in accordance with the concept that the stress or strain corresponding to the yield point of the material should not be exceeded at the most highly stressed points of the structure. 这种传统的设计称为弹性设计，因为允许应力强度是根据以下概念相一致来选择的，即相应于材
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料屈服点的应力或应变，即使在结构最高应力点处也不可能超限。
291. The student who is preparing to be a civil engineer may deal with such subjects as geodetic surveying. 一个想成为土木工程师的学生可能需要学习大地测量等课程。
292. Civil engineers were necessary in the design and construction of such structures as launching pads. 设计和建筑像发射台这样的建筑需要土木工程师的参与。
293. In the engineering curriculum, a current trend is to require students to take course in social science. 在工程课程中，当今一个潮流就是要选修社会科学课程。
294. Research is one of the most important aspects of scientific and engineering practice. 研究是科研和工程实践中最重要的方面之一。
295. Numerous publications have been prepared on the subject of road design and control for highway safety. 有关道路设计及其安全控制问题，已出版了众多著作。
296. The relationship between engineering and society is getting closer. 工程学和社会学的关系变得越来越密切。
297. Young engineer may choose to go into environmental or sanitary engineering. 年轻的工程师可以选择环境或环卫工程。
298. On-the- job training can be acquired that will demonstrate his or her ability to translate theory into practice to the supervisors. 在职培训将使主管人了解他(她)将理论运用于实践的能力。
299. The civil engineer may work in research, design, maintenance, even in sales or management. 土木工程师可以从事研究、设计、养护甚至于销售或管理工作。
300. As we have seen, civil engineers work on many different kinds of structures. 正如我们所知，土木工程师可以从事有关建筑方面的多种工作。
301. These great buildings were not the product of knowledge of mathematics and physics. 这些伟大的建筑物不是数学和物理知识的产物。
302. Steel and concrete complement each other in another way. 钢筋和混凝土可以在另一方面互补。
303. Acid corrodes steel, whereas concrete has an alkaline chemical reaction, the opposite of acid.
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