土木工程类外文文献翻译.d

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1、-1 中文翻译摘要：为了研究连续型拓扑优化理论在实际工程中的应用，该文给出了一种多层钢框架支撑体系连续型拓扑优化设计方法。基于灵敏度分析，探讨了连续体构造在多工况荷载作用下、同时受应力和多位移约束的拓扑优化删除准则。为保证拓扑优化结果的合理性，提出了设计区域平均厚度的概念。在该文给出的优化设计方法中，首先在不考虑位移约束的情况下对无支撑钢框架进展优化设计，然后在有位移约束的条件下采用渐进构造优化算法和删除准则对支撑体系进展连续型拓扑优化设计，并将获得的支撑最优拓扑构形转化成相应的杆件。通过一个3跨12层钢框架支撑体系的拓扑优化设计实例验证了该文给出的钢框架支撑体系连续型拓扑优化设计方法的有效性

2、。关键词：钢框架；支撑体系；连续型；拓扑优化；渐进构造优化1.1钢筋混凝土素混凝土是由水泥、水、细骨料、粗骨料碎石或；卵石、空气，通常还有其他外加剂等经过凝固硬化而成。将可塑的混凝土拌合物注入到模板内，并将其捣实，然后进展养护，以加速水泥与水的水化反响，最后获得硬化的混凝土。其最终制成品具有较高的抗压强度和较低的抗拉强度。其抗拉强度约为抗压强度的十分之一。因此，截面的受拉区必须配置抗拉钢筋和抗剪钢筋以增加钢筋混凝土构件中较弱的受拉区的强度。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，需要对构造设计的根本原理进展修改。将钢筋混凝土这种非均质截面的两种组成局部按一定比例适当

3、布置，可以最好的利用这两种材料。这一要求是可以到达的。因混凝土由配料搅拌成湿拌合物，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，可以作为任何构造体系的主要构件。浇筑混凝土所需要的技术取决于即将浇筑的构件类型，诸如：柱、梁、墙、板、根底，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、墙等构件，当模板清理干净后应该在其上涂油，钢筋外表的锈及其他有害物质也应该被去除干净。浇筑根底前，应将坑底土夯实并用水浸湿6英寸，以免土壤从新浇的混凝土中吸收水分。一般情况下，除使用混凝土泵浇筑外，混凝

4、土都应在水平方向分层浇筑，并使用插入式或外表式高频电动振捣器捣实。必须记住，过分的振捣将导致骨料离析和混凝土泌浆等现象，因而是有害的。水泥的水化作用发生在有水分存在，而且气温在50F以上的条件下。为了保证水泥的水化作用得以进展，必须具备上述条件。如果枯燥过快则会出现外表裂缝，这将有损与混凝土的强度，同时也会影响到水泥水化作用的充分进展。设计钢筋混凝土构件时显然需要处理大量的参数，诸如宽度、高度等几何尺寸，配筋的面积，钢筋的应变和混凝土的应变，钢筋的应力等等。因此，在选择混凝土截面时需要进展试算并作调整，根据施工现场条件、混凝土原材料的供给情况、业主提出的特殊要求、对建筑和净空高度的要求、所用的

5、设计规*以及建筑物周围环境条件等最后确定截面。钢筋混凝土通常是现场浇注的合成材料，它与在工厂中制造的标准的钢构造梁、柱等不同，因此对于上面所提到的一系列因素必须予以考虑。对构造体系的各个部位均需选定试算截面并进展验算，以确定该截面的名义强度是否足以承受所作用的计算荷载。由于经常需要进展屡次试算，才能求出所需的截面，因此设计时第一次采用的数值将导致一系列的试算与调整工作。选择混凝土截面时，采用试算与调整过程可以使复核与设计结合在一起。因此，当试算截面选定后，每次设计都是对截面进展复核。手册、图表和微型计算机以及专用程序的使用，使这种设计方法更为简捷有效，而传统的方法则是把钢筋混凝土的复核与单纯的

6、设计分别进展处理。1.2土方工程由于和土木工程中任何其他工种的施工方法与费用相比拟，土方挖运的施工方法与费用的变化都要快得多，因此对于有事业心的人来说，土方工程是一个可以大有作为的领域。在1935年，目前采用的利用轮胎式机械设备进展土方挖运的方法大多数还没有出现。那是大局部土方是采用窄轨铁路运输，在这目前来说是很少采用的。当时主要的开挖方式是使用正铲、反铲、拉铲或抓斗等挖土机，尽管这些机械目前仍然在广泛应用，但是它们只不过是目前所采用的许多方法中的一小局部。因此，一个工程师为了使自己在土方挖运设备方面的知识跟得上时代的开展，他应当花费一些时间去研究现代的机械。一般说来，有关挖土机、装载机和运输

7、机械的唯一可靠而又最新的资料可以从制造厂商处获得。土方工程或土方挖运工程指的是把地外表过高处的土壤挖去挖方，并把它倾卸到地外表过低的其他地方填方。为了降低土方工程费用，填方量应该等于挖方量，而且挖方地点应该尽可能靠近土方量相等的填方地点，以减少运输量和填方的二次搬运。土方设计这项工作落到了从事道路设计的工程师的身上，因为土方工程的设计比其他任何工作更能决定工程造价是否低廉。根据现有的地图和标高，道路工程师应在设计绘图室中的工作也并不是徒劳的。它将帮助他在最短的时间内获得最好的方案。费用最低的运土方法是用同一台机械直接挖方取土并且卸土作为填方。这并不是经常可以做到的，但是如果能够做到则是很理想的

8、，因为这样做既快捷又省钱。拉铲挖土机。推土机和正铲挖土机都能做到这点。拉铲挖土机的工作半径最大。推土机所推运的图的数量最多，只是运输距离很短。拉铲挖土机的缺点是只能挖比它本身低的土，不能施加压力挖入压实的土壤内，不能在陡坡上挖土，而且挖。卸都不准确。正铲挖土机介于推土机和拉铲挖土机的之间，其作用半径大于推土机，但小于拉铲挖土机。正铲挖土机能挖取竖直陡峭的工作面，这种方式对推土机司机来说是危险的，而对拉铲挖土机则是不可能的。每种机械设备应该进展最适合它的性能的作业。正铲挖土机不能挖比其停机平面低很多的土，而深挖坚实的土壤时，反铲挖土机最适用，但其卸料半径比起装有正铲的同一挖土机的卸料半径则要小很

9、多。在比拟平坦的场地开挖，如果用拉铲或正铲挖土机运输距离太远时，则装有轮胎式的斗式铲运机就是比不可少的。它能在比拟平的地面上挖较深的土但只能挖机械本身下面的土，需要时可以将土运至几百米远，然后卸土并在卸土的过程中把土大致铲平。在挖掘硬土时，人们发现在开挖场地经常用一辆助推拖拉机轮式或履带式，对返回挖土的铲运机进展助推这种施工方法是经济的。一旦铲运机装满，助推拖拉机就回到开挖的地点去帮助下一台铲运机。斗式铲运机通常是功率非常大的机械，许多厂家制造的铲运机铲斗容量为8 m，满载时可达10 m。最大的自行式铲运机铲斗容量为19立方米满载时为25 m，由430马力的牵引发动机驱动。翻斗机可能是使用最为

10、普遍的轮胎式运输设备，因为它们还可以被用来送混凝土或者其他建筑材料。翻斗车的车斗位于大橡胶轮胎车轮前轴的上方，尽管铰接式翻斗车的卸料方向有很多种，但大多数车斗是向前翻转的。最小的翻斗车的容量大约为0.5立方米，而最大的标准型翻斗车的容量大约为4.5m。特殊型式的翻斗车包括容量为4 m的自装式翻斗车，和容量约为0.5 m的铰接式翻斗车。必须记住翻斗车与自卸卡车之间的区别。翻斗车车斗向前倾翻而司机坐在前方卸载，因此有时被称为后卸卡车。1.3构造的平安度规*的主要目的是提供一般性的设计原理和计算方法，以便验算构造的平安度。就目前的趋势而言，平安系数与所使用的材料性质及其组织情况无关，通常把它定义为发

11、生破坏的条件与构造可预料的最不利的工作条件之比值。这个比值还与构造的破坏概率危险率成反比。破坏不仅仅指构造的整体破坏，而且还指构造不能正常的使用，或者，用更为确切的话来说，把破坏看成是构造已经到达不能继续承当其设计荷载的极限状态。通常有两种类型的极限状态，即：1强度极限状态，它相当于构造能够到达的最大承载能力。其例子包括构造的局部屈曲和整体不稳定性；*此界面失效，随后构造转变为机构；疲劳破坏；引起构造几何形状显著变化的弹性变形或塑性变形或徐变；构造对交变荷载、火灾和爆炸的敏感性。2使用极限状态，它对应着构造的使用功能和耐久性。器例子包括构造失稳之前的过大变形和位移；早期开裂或过大的裂缝；较大的

12、振动和腐蚀。根据不同的平安度条件，可以把构造验算所采用的计算方法分成：1确定性的方法，在这种方法中，把主要参数看作非随机参数。2概率方法，在这种方法中，主要参数被认为是随机参数。此外，根据平安系数的不同用途，可以把构造的计算方法分为：1容许应力法，在这种方法中，把构造承受最大荷载时计算得到的应力与经过按规定的平安系数进展折减后的材料强度作比拟。2极限状态法，在这种方法中，构造的工作状态是以其最大强度为依据来衡量的。由理论分析确定的这一最大强度应不小于构造承受计算荷载所算得的强度极限状态。计算荷载等于分别乘以荷载系数的活载与恒载之和。把对应于不乘以荷载系数的活载和恒载的工作使用条件的应力与规定值

13、使用极限状态相比拟。根据前两种方法和后两种方法的四种可能组合，我们可以得到一些实用的计算方法。通常采用下面两种计算方法：确定性的方法，这种方法采用容许应力。概率方法，这种方法采用极限状态。至少在理论上，概率法的主要优点是可以科学的考虑所有随机平安系数，然后将这些随机平安系数组合成确定的平安系数。概率法取决于：1制作和安装过程中材料强度的随机分布整个构造的力学性能数值的分散性；2截面和构造几何尺寸的不确定性由构造制作和安装造成的误差和缺陷而引起的；对作用在构造上的活载和恒载的预测的不确定性；所采用的近似计算方法有关的不准确性实际应力与计算应力的偏差。此外，概率理论意味着可以基于下面几个因素来确定

14、允许的危险率，例如：建筑物的重要性和建筑物破坏造成的危害性；2由于建筑物破坏使生活受到威胁的人数；3修复建筑的可能性；4建筑物的预期寿命。所有这些因素均与经济和社会条件有关，例如：1建筑物的初始建立费；2建筑物使用期限内的折旧费；3由于建筑物破坏而造成的物质和材料损失费；4在社会上造成的不良影响；5精神和心理上的考虑。就给定的平安系数而论，所有这些参数确实定都是以建筑物的最正确本钱为依据的。但是，应该考虑到进展全概率分析的困难。对于这种分析来说，应该了解活载及其所引起的盈利的分布规律、材料的力学性能的分散性和截面的构造几何尺寸的分散性。此外，由于强度的分布规律和应力的分布规律之间的相互关系是困

15、难的。这些实际困难可以采用两种方法来克制。第一种方法对材料和荷载采用不同的平安系数，而不需要采用概率准则；第二种方法是引入一些而简化假设的近似概率方法半概率方法。2 外文翻译Abstract:To study the application of continuum structural topology optimization methods to real engineering structures,an optimization method for an optimal topology design of multistory steel frame bracing system

16、s is presented.On a sensitivity analysis,an element removal criterion for continuum structures with stress and multi-displacement constraints under multiple lateral loading conditions is proposed.A concept of mean thickness of a design domain is provided to ensure the reasonableness of optimal resul

17、ts.In the proposed optimization method,the optimal design of an unbraced steel frame without displacement constraints is performed firstly,and then the optimal topology of a bracing system for the multistory steel frame considering displacement constraints is obtained by using evolutionary structura

18、l optimization and the given removal criterion,and finally the optima layout of the bracing system is interpreted as bracing members.An e*ample of 3-bay 12-story plane steel frame shows that it is effective for the given optimization method in the optimal design of bracing systems for multistory ste

19、el frames. Key words:steel frame;bracing system;continuum;topology optimization;evolutionary structural optimization2.1 Reinforced ConcretePlain concrete is formed from a hardened mi*ture of cement ,water ,fine aggregate,coarse aggregate (crushed stone or gravel),air,and often other admi*tures. The

20、plasticmi* is placed and consolidated in the formwork,then cured to facilitate the acceleration of the chemical hydration reaction lf the cement/water mi*, resulting in hardened concrete. The finished product has high pressive strength, and low resistance to tension, such that its tensile strength i

21、s appro*imately one tenth lf its pressive strength. Consequently, tensile and shear reinforcement in the tensile regions of sections has to be provided to pensate for the weak tension regions in the reinforced concrete element.It is this deviation in the position of a reinforces concrete section fro

22、m the homogeneity of standard wood or steel sections that requires a modified approach to the basic principles of structural design. The two ponents of the heterogeneous reinforced concrete section are to be so arranged and proportioned that optimal use is made of the materials involved. This is pos

23、sible because concrete can easily be given anydesired shape by placing and pacting the wet mi*ture of the constituent ingredients are properly proportioned, the finished product bees strong, durable,and,in bination with the reinforcing bars, adaptable for use as main members of any structural system

24、.The techniques necessary for placing concrete depend on the type of member to be cast:that is, whether it is a column, a bean, a wall, a slab, a foundation. a mass columns, or an e*tension of previously placed and hardened concrete. For beams, columns, and walls, the forms should be well oiled afte

25、r cleaning them,and the reinforcement should be cleared of rust and other harmful materials. In foundations, the earth should be pacted 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 lay

26、ers which are pacted by means of high frequency power-driven vibrators of either the immersion or e*ternal type, as the case requires, unless it is placed by pumping. It must be kept in mind, however, that over vibration can be harmful since it could cause segregation of the aggregate and bleeding o

27、f the concrete.Hydration of the cement takes place in the presence of moisture at temperatures above 50F. It is necessary to maintain such a condition in order that the chemical hydration reaction can take place. If drying is too rapid, surface cracking takes place.This would result in reduction of

28、concrete strength due to cracking as well as the failure to attain full chemical hydration.It is clear that a large number of parameters have to be dealt with in proportioning a reinforced concrete element, such as geometrical width, depth, area of reinforcement, steel strain,concrete strain, steel

29、stress, and so on. Consequently, trial and adjustment is necessary in the choice of concrete sections, with assumptions based on conditions at site, availability of the constituent materials, particular demands of the owners, architectural and headroom requirements,the applicable codes, and environm

30、ental reinforced concrete is often a site-constructed posite, in contrast to the standard mill-fabricated beam and column sections in steel structures.Atrial section has to be chosen for each critical location in a structural system. The trial section has to be analyzed to determine if its nominal r

31、esisting strength is adequate to carry the applied factored load. Since more than one trial is often necessary to arrive at the required section, the first design input step generates into a series of trial-and-adjustment analyses.The trial-and adjustment procedures for the choice of a concrete sect

32、ion lead to the convergence of analysis and design. Hence every design is an analysis once a trial section is chosen. The availability of handbooks, charts, and personal puters and programs supports this approach as a more efficient, pact, and speedy instructional method pared with the traditional a

33、pproach of treating the analysis of reinforced concrete separately from pure design.2.2EarthworkBecause earthmoving methods and costs change more quickly than those in any other branch of civil engineering, this is a field where there are real opportunities for the enthusiast. In 1935 most of the me

34、thods now in use for carrying and e*cavating earth with rubber-tyred equipment did not e*ist. Most earth was moved by narrow rail track, now relatively rare, and the main methods of e*cavation, with face shovel, backacter, or dragline or grab, though they are still widely used are only a few of the

35、many current methods. To keep his knowledge of earthmoving equipment up to date an engineer must therefore spend tine studying modern machines. Generally the only reliable up-to-date information on e*cavators, loaders and transport is obtainable from the makers.Earthworks or earthmoving means cuttin

36、g into ground where its surface is too high ( cuts ), and dumping the earth in other places where the surface is too low ( fills). Toreduce earthwork costs, the volume of the fills should be equal to the volume of the cuts and wherever possible the cuts should be placednear to fills of equal volume

37、so as to reduce transport and double handlingof the fill. This work of earthwork design falls on the engineer who lays out the road since it is the layout of the earthwork more than anything else which decides its cheapness. From the available maps ahd levels, the engineering must try to reach as ma

38、ny decisions as possible in the drawing office by drawing cross sections of the earthwork. On the site when further information bees available he can make changes in jis sections and layout,but the drawing lffice work will not have been lost. It will have helped him to reach the best solution in the

39、 shortest time.The cheapest way of moving earth is to take it directly out of the cut and drop it as fill with the same machine. This is not always possible, but when it canbe done it is ideal, being both quick and cheap. Draglines, bulldozers and face shovels an do this. The largest radius is obtai

40、ned with the dragline,and the largest tonnage of earth is moved by the bulldozer, though only over short distances.The disadvantages of the dragline are that it must dig below itself, it cannot dig with force into pacted material, it cannot dig on steep slopws, and its dumping and digging are not ac

41、curate.Face shovels are between bulldozers and draglines, having a larger radius of action than bulldozers but less than draglines. They are anle to dig into a vertical cliff face in a way which would be dangerous tor a bulldozer operator and impossible for a dragline. Each piece of equipment should

42、 be level of their tracks and for deep digs in pact material a backacter is most useful, but its dumping radius is considerably less than that of the same escavator fitted with a face shovel.Rubber-tyred bowl scrapers are indispensable for fairly level digging where the distance of transport is too

43、much tor a dragline or face shovel. They can dig the material deeply ( but only below themselves ) to a fairly flat surface, carry it hundreds of meters if need be, then drop it and level it roughly during the dumping. For hard digging it is often found economical to keep a pusher tractor ( wheeled

44、or tracked ) on the digging site, to push each scraper as it returns to dig. As soon as the scraper is full,the pusher tractor returns to the beginning of the dig to heop to help the nest scraper.Bowl scrapers are often e*tremely powerful machines;many makers build scrapers of 8 cubic meters struck

45、capacity, which carry 10 m heaped. The largest self-propelled scrapers are of 19 m struck capacity ( 25 m heaped )and they are driven by a tractor engine of 430 horse-powers.Dumpers are probably the monest rubber-tyred transport since they can also conveniently be used for carrying concrete or other

46、 building materials. Dumpers have the earth container over the front a*le on large rubber-tyred wheels, and the container tips forwards on most types, though in articulated dumpers the direction of tip can be widely varied. The smallest dumpers have a capacity of about 0.5 m , and the largest standa

47、rd types are of about 4.5 m . Special types include the self-loading dumper of up to 4 m and the articulated type of about 0.5 m . The distinction between dumpers and dump trucks must be remembered .dumpers tip forwards and the driver sits behind the load. Dump trucks are heavy, strengthened tipping

48、 lorries, the driver travels in front lf the load and the load is dumped behind him, so they are sometimes called rear-dump trucks. 2.3 Safety of StructuresThe principal scope of specifications is to provide general principles and putational methods in order to verify safety of structures.The safety

49、 factor , which according to modern trends is independent of the nature and bination of the materials used, can usually be defined as the ratio between the conditions. This ratio is alsoproportional to the inverse of the probability ( risk ) of failure of the structure. Failure has to be considered

50、not only as overall collapse of the structure but also as unserviceability or, according to a more precise. mon definition. As the reaching of a limit state which causes the construction not to acplish the task it was designed for. There are two categories of limit state :(1)Ultimate limit sate, whi

51、ch corresponds to the highest value of the load-bearing capacity. E*amples include local buckling or global instability of the structure; failure of some sections and subsequent transformation of the structure into a mechanism; failure by fatigue; elastic or plastic deformation or creep that cause a

52、 substantial change of the geometry of the structure; and sensitivity of the structure to alternating loads, to fire and to e*plosions.(2)Service limit states, which are functions of the use and durability of the structure. E*amples include e*cessive deformations and displacements without instabilit

53、y; early or e*cessive cracks; large vibrations; and corrosion.putational methods used to verify structures with respect to the different safety conditions can be separated into:(1)Deterministic methods, in which the main parameters are considered as nonrandom parameters.(2)Probabilistic methods, in

54、which the main parameters are considered as random parameters.Alternatively, with respect to the different use of factors of safety, putational methods can be separated into:(1)Allowable stress method, in which the stresses puted under ma*imum loads are pared with the strength of the material reduce

55、d by given safety factors.(2)Limit states method, in which the structure may be proportioned on the basis of its ma*imum strength.This strength, as determined by rationalanalysis, shall not be less than that required to support a factored load equal to the sum of the factored live load and dead load

56、 ( ultimate state ).The stresses corresponding to working ( service ) conditions with unfactored live and dead loads are pared with prescribed values ( service limit state ) . From the four possible binations of the first two and second two methods, we can obtain some useful putational methods. Gene

57、rally, two binations prevail:(1)deterministic methods, which make use of allowable stresses.(2)Probabilistic methods, which make use of limit states.The main advantage of probabilistic approaches is that, at least in theory, it is possible to scientifically take into account all random factors of sa

58、fety, which are then bined to define the safety factor.probabilistic approaches depend upon : (1)Random distribution of strength of materials with respect to the conditions of fabrication and erection ( scatter of the values of mechanical properties through out the structure );(2)Uncertainty of the

59、geometry of the cross-sectionsand of the structure ( faults and imperfections due to fabrication and erection of the structure );(3)Uncertainty of the predicted live loads and dead loads acting on the structure;(4)Uncertainty related to the appro*imation of the putational method used ( deviation of

60、the actual stresses from puted stresses ).Furthermore, probabilistic theories mean that the allowable risk can be based on several factors, such as :(1)Importance of the construction and gravity of the damage by its failure;(2)Number of human lives which can be threatened by this failure;(3)Possibil

61、ity and/or likelihood of repairing the structure;(4)Predicted life of the structure.All these factors are related to economic and social considerations such as：(1)Initial cost of the construction; (2)Amortization funds for the duration of the construction; (3)Cost of physical and material damage due

62、 to the failure of the construction; (4)Adverse impact on society; (5)Moral and psychological views. The definition of all these parameters, for a given safety factor, allows construction at the optimum cost. However, the difficulty of carrying out a plete probabilistic analysis has to be taken into

63、 account. For such an analysis the laws of the distribution of the live load and its induced stresses, of the scatter of mechanical properties of materials, and of the geometry of the cross-sections and the structure have to be known. Furthermore, it is difficult to interpret the interaction between

64、 the law of distribution of strength and that of stresses because both depend upon the nature of the material, on the cross-sections and upon the load acting on the structure. Thesepractical difficulties can be overe in two ways. The first is to apply different safety factors to the material and to the loads, without necessarily adopting the probabilistic criterion. The second is an appro*imate probabilistic method which introduces some simplifying assumptions ( semi-probabilistic methods ) . z.