《专业英语l》PPT课件.ppt

LESSON 2 Introduction to Structural Design Structural Design The structural design of buildings， whether of structural steel or reinforced concrete, requires the determination of the overall proportions and dimensions of the supporting framework and the selection of the cross sections of individual members In most cases the functional design， including the establishment of the number of stories and the floor plan， will have been done by an architect， and the structural engineer must work within the constraints imposed by this design 参考译文 无论钢结构或钢筋混凝土，建筑物的结构设 计需要确定整体比例，支持框架尺寸和选择各个 构件截面。在大多数情况下，包括确定楼层的数 目和平面图的功能设计， 将由建筑师和结构工程 师依据这一设计的限定条件来完成。 framework freimw:k n. 框架，骨架；结构，构架 constraint knstreint n. 约束；强制；局促，态度 不自然 impose impuz vi. 欺骗；利用；施加影响 vt. 强加；以欺骗；征税 Structural Design Ideally， the engineer and architect will collaborate throughout the design process so that the project is completed in an efficient manner In effect， however， the design can be summed up as follows: The architect decides how the building should look： the engineer must make sure that it doesnt fall down Although this is an oversimplification， it affirms the first priority of the structural engineer： safety 参考译文 理想情况下，工程师和建筑师将在整个设计过 程中合作，以便以有效的方式完成项目。不管 怎样，实际上设计可以概括如下： 建筑师决定 建筑物的外观： 工程师必须确保它不会倒。虽 然这是过于简单化，但它阐明了结构工程师的 第一要务： 安全。 collaborate klbreit vi. 合作；勾结，通敌 oversimplification uv,simplifikein n. 过度单纯 化；过分简单化 Structural Design Other important considerations include serviceability (how well the structure performs in terms of appearance and deflection) and economy An economical structure requires an efficient use of materials and construction labor Although this can usually be accomplished by a design that requires a minimum amount of material， savings can often be realized by using slightly more material if it results in a simpler， more easily constructed project 参考译文 其他要考虑的主要因素包括适用性 （如何合理表 现结构的外观和偏差）和节约。一个经济的建筑 需要高效使用材料和施工工时。虽然这通常通过 需要最少建材的设计来实现， 但往往节约可通过 使用稍多的建材而产生一个更简单、更易于施工 的项目来实现。 serviceability ,s:visbiliti n. 可用性，适用性； 使用可靠性；计 可服务性；可维修性 Structural Design A good design requires the evaluation of several framing plans-that is， different arrangements of members and their connections In other words， several alternate designs should be prepared and their costs compared For each framing plan investigated， the individual components must be designed This requires the structural analysis of the frame(s) of the building and the computation of forces and bending moments in the individual members 参考译文 一个好的设计需要对多个设计规划评估 构 件及其连接的不同组合。换句话说，应准备几种 备用设计及其成本比较。 对每个设计规划，都必 须审查其单独组件设计。这就要求有建筑框架的 结构分析和各个构件的力与弯矩的计算。 evaluation i,vljuein n. 评价；审计 评估；估价 ；求值 Bending moment 力 弯矩；力 弯曲力矩； 力 挠矩 Structural Design Armed with this information， the structural designer can then select the appropriate cross section Before any analysis，however， a decision must be made on the building material to be used： it will usually be reinforced concrete， structural steel， or both Ideally， alternate designs should be prepared with each 参考译文 有了这些信息，结构设计者则可以选择适当 的横截面。不过，在任何分析之前必须决定要使 用的建筑材料 ： 通常是钢筋混凝土、 钢结构或 兼有。理想情况下， 每个方案都应准备不同的设 计。 Loads The forces that act on a structure are called loadsThey belong to one of two broad categories：dead load and live load Dead loads are those that are permanent， including the weight of the structure itself， which is sometimes called the self-weight Other dead loads in a building include the weight of nonstructural components such as floor coverings， suspended ceilings with light fixtures， and partitions 参考译文 作用于结构上的力被称为荷载。所有荷载分 属于两大类别： 恒载与活载。恒载是那些永久的 负荷，包括结构本身的重量，有时也称为自重。 建筑物内的其他恒载包括某些非结构构件的重量 ，诸如地板、 有灯具的吊顶、 隔断等。 fixture fikst n. 设备；固定装置；固定于某处不 大可能移动之物 partition p:tin n. 划分，分开；数 分割；隔墙 ；隔离物 vt. 数 分割；分隔；区分 Dead load 恒载；静负荷 Live load 动荷；活负载；有效负载 Loads All of the loads mentioned thus far are forces due to gravity and are referred to as gravity loads, live loads，which can also be gravity loads， are those that are not as permanent as dead loadsThis type may or may not be acting on the structure at any given time，and the location may not be fixed 参考译文 迄今为止所提到的所有负荷均源于重力，故称之 为重力荷载，活荷载也可以是重力荷载，是那些 不像恒载那样永久的荷载。这种类型的荷载可能 会在任何给定时间作用于结构，也可能不会 ； 其作用位置也可能不固定。 be referred to as 被称为 Loads Examples of live load include furniture， equipment, and occupants of buildings In general， the magnitude of a live load is not as well defined as that of a dead load， and it usually must be estimated In many cases， a given structural member must be investigated for various positions of the live load so that a potential failure situation is not overlooked 参考译文 活荷载的例子包括家具、 设备和建筑物的住客。 一般情况下，活荷载的大小无法像恒载那样定义 ，通常必须估计。在许多情况下，必须对给定的 结构构件进行处在不同活载作用位置时的检验， 使潜在的破坏不被忽视。 occupants kju:pnts n. 居住者；购买者；租赁 人（occupant的复数） Loads If the live load is applied slowly and is not removed and reapplied an excessive number of times. the structure can be analyzed as if the loads were static. If the load is applied suddenly, as would be the case when the structure supports a moving crane. we must account for the effects of impact. If the load is applied and removed many times over the life of the structure. fatigue stress becomes a problem. and we must account for its effects. Impact loading occurs in relatively few buildings, notably industrial buildings, and fatigue loading is rare, with thousands of load cycles over the life of the structure required before fatigue becomes a problem 参考译文 如果活荷载缓慢地施加且未被移除，并且重 复施加次数极多，可以按荷载类似于静止来分析 结构。 如果突然施加荷载，就像结构支撑一台移 动起重机的情况， 我们就必须考虑冲击影响。如 果负载施加移除次数超过了结构寿命，疲劳应力 成为一个问题，并且我们必须考虑其影响。相对 较少的建筑物会有冲击荷载，主要是工业建筑， 在疲劳成为问题之前，超越结构寿命成千上万次 的疲劳荷载周期很少予以考虑。 Loads Wind exerts a pressure or suction on the exterior surfaces of a building; because of its transient nature, it properly belongs in the category of live loads. Because of the relative complexity of determining wind loads, however, wind is usually considered a separate category of loading. Since lateral loads are most detrimental to tall structures， wind loads are usually not as important for low buildings， but uplift on light roof systems can be critical. Although wind is present most of the time, wind loads of the magnitude considered in design are infrequent and are not considered to be fatigue loads 参考译文 风会对建筑物的外表面产生压力或吸力；由于其短暂的 性质适合于归类为活载。不过，由于确定风荷载相对复 杂， 风通常被认为另一类荷载。由于侧向荷载对高层结 构最不利，风荷载对于低的建筑通常并不重要，但对轻 型屋面系统上的隆起可能非常重要。虽然风在大多数时 间存在， 但风荷载在设计中考虑的很少，并不被认为是 疲劳荷载。 exert iz:t vt. 运用，发挥；施以影响 transient trnzint, -si-, -nt, tr:n- adj. 短暂的； 路过的 n. 瞬变现象；过往旅客；候鸟 Loads 2Earthquake actions are another special category and need to be considered only in those geographic locations where there is a reasonable probability of occurrence A structural analysis of the effects of an earthquake requires an analysis of the structures response to the ground motion produced by the earthquake Simpler methods are sometimes used in which the effects of the earthquake are simulated by a system of horizontal loads, similar to those resulting from wind pressure, acting at each floor level of the building 参考译文 地震作用是另一个特殊的类别，只需要在那些有 一定发生概率的地理位置考虑。地震影响的结构 分析需要分析结构对地震产生的地面运动的响应 。有时，更简单的方法使用一个横向荷载系统模 拟，类似于作用在建筑物各层的风压力那样。 Loads 2Earthquake actions are another special category and need to be considered only in those geographic locations where there is a reasonable probability of occurrence. A structural analysis of the effects of an earthquake requires an analysis of the structures response to the ground motion produced by the earthquake. Simpler methods are sometimes used in which the effects of the earthquake are simulated by a system of horizontal loads, similar to those resulting from wind pressure, acting at each floor level of the building 参考译文 地震作用是另一个特殊的类别，只需要在那些有 一定发生概率的地理位置考虑。地震影响的结构 分析需要分析结构对地震产生的地面运动的响应 。有时，更简单的方法使用一个横向荷载系统模 拟，类似于作用在建筑物各层的风压力那样。 Loads Snow is another live load that is treated as a separate category. Adding to the uncertainty of this load is the complication of drift, which can cause much of the load to accumulate over a relatively small area Other types of live load are often treated as separate categories. such as hydrostatic pressure and soil pressure. but the cases enumerated above are the ones ordinarily encountered in the design of buildings 参考译文 雪是另一个被视为一个单独类别的活荷载。增加 此负载的不确定性是负载的漂移，其可能会导致 在相对较小的区域内更多荷载积累。 其他类型的活载往往被视为独立的类别，如静水 压力和土壤的压力，但以上列举的在建筑设计中 通常为遇到的个案。 Building Codes Buildings must be designed and constructed according to the provisions of a building code, which is a legal document containing requirements related to such things as structural safety, fire safety, plumbing, ventilation, and accessibility to the physically disabled. A building code has the force of law and is administered by a governmental entity such as a city, a county, or, for some large metropolitan areas, a consolidated government 参考译文 建筑物必须依据建筑法规的规定设计和建造，这 一法律文件包含了相关的要求，诸如结构安全、 消防安全、 水暖、 通风和伤残人士的辅助功能 。建筑规范具有法律效力，而由一个政府实体， 如县市，或为一些大都市区的政府管理。 building code 建筑法规 plumbing plmi n. 铅工业；铅管品制造 v. 探究；垂直悬挂；用铅锤测量；灌铅以增重（ plumb的现在分词） 卫生管道工程；水管设施；波导设备；水管装置 ventilation ,ventilein n. 通风设备；空气流通 Building Codes Building codes do not give design procedures, but they do specify the design requirements and constraints that must be satisfied. Of particular importance to the structural engineer is the prescription of minimum live loads for buildings. Although the engineer is encouraged to investigate the actual loading conditions and attempt to determine realistic values, the structure must be able to support these specified minimum loads 参考译文 建筑法规不指定设计程序，但规定设计要求和所 必须满足的约束。对结构工程师特别重要的是建 筑物最低活载的规定。尽管鼓励工程师调查实际 加载条件并尝试确定实际的数值， 结构必须能够 支撑这些指定的最小负荷。 prescription priskripn n. 药方；指示；惯例 adj. 凭处方方可购买的 Building Codes Although some large cities write their own building codes, many municipalities will adopt a “model” building code and modify it to suit their particular needs. Model codes are written by various nonprofit organizations in a form that is easily adopted by a governmental unit. Currently, there are three national model codes: the BOCA National Building Code, the Uniform Building Code, and the Standard Building Code. A related document, similar in form to a building code, is ASCE 7-98. Minimum Design Loads for Buildings and Other Structures. This standard is intended to provide load requirements in a format suitable for adoption by a building code 参考译文 虽然一些大城市制定自己的建筑规范，许多城市 将采用建筑法规的“模式“并进行修改，以适合其 特定需要。这些法规模型以政府单位易于接受的 形式由各种非营利组织编写。目前，有三个国家 的模型规范： 博卡国家建筑标准、 统一的建筑 法规和标准建设规范。 类似于建筑规范的相关文 件是 ASCE 7 98，建筑物和其他结构最小 设计荷载。这一标准旨在以建筑规范适合采用的 格式提出负载要求。 Design Specifications In contrast to building codes, design specifications give more specific guidance for the design of structural members and their connections. They present the guidelines and criteria that enable a structural engineer to achieve the objectives mandated by a building code. Design specifications represent what is considered to be good engineering practice based on their latest research 参考译文 相对于建筑规范，设计规范给设计结构构件和其 连接更具体的指导。其中提出的指导方针和标准 ，使结构工程师来达到建筑规范强制规定的目标 。设计规范代表了建立在最新研究的基础上被认 为是良好的工程实践。 mandate mndeit n. 命令，指令；委托管理；授 权；受命进行的工作 vt. 托管；授权 guidelines gaid,linz n. 指导方针 Design Specifications They are periodically revised and updated by supplements or by completely new editions. As with model building codes, design specifications are written in a legal format by nonprofit organizations. They have no legal standing on their own, but by presenting design criteria and limits in the form of legal mandates and prohibitions, they can easily be adopted, by