【正文】 The range of particle sizes encountered in soils is very wide: from around 200mm down to the colloidal size of some clays of less than 11 . 在各種土中所遇到的粒徑范圍很大，大到 200mm 小到小于 的一些粘土膠粒。 9 Lesson 3 New words 1. col`loidal 膠狀的，膠體的， `colloid 膠體 2. sieve n,v. 篩，過篩，過濾 3. sample . 樣品，取樣 specimen 4. mesh 網(wǎng)孔，網(wǎng)格，分網(wǎng)格 5. `cumulative a. 積累的； cumulate, cumulation 6. grading n. 級配，等級； grade 7. sedimentation n. 沉淀 。 As with model building codes, design specifications are written in a legal format by nonprofit anizations. 如同一般建筑規(guī)范，設(shè)計(jì)規(guī) 程由非贏利組織編寫。 Design specifications represent what is considered to be good engineering practice based on their latest research. 根據(jù) 其最新研究，設(shè)計(jì)規(guī)程結(jié)出認(rèn)為是好的工程作法。 Design specifications In contrast to building codes, design specifications give more specific guidance for the design of 8 structural members and their connections. 與建筑規(guī)范不同，設(shè)計(jì)規(guī)程給出結(jié)構(gòu)構(gòu)件及其連接的更具體的指南。 Of particular importance to the structural engineer is the prescription of minimum live loads for buildings. 對結(jié)構(gòu)工程師特別重要的是建筑物的最小活荷載規(guī)定。 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. 建筑規(guī)范具有法律效力，由政府部位發(fā) 布，如城市、縣、對于大的城區(qū)，如聯(lián)合政府。在許多情況下，必須研究活荷載作用在一給定的結(jié)構(gòu)構(gòu)件的各個位置以便不會漏掉每個可能的破壞情形。Examples of live load include furniture, equipment, and occupants of buildings. 活荷載包括家具、設(shè)置和建筑物的居住者。 Live loads, which can also be gravity loads, are those that are not as permanent as dead loads. 活載也可以是重力荷載，它們是那些不如恒載那樣永久的荷載。 Other dead loads in a building include the weight of nonstructural ponents such as floor coverings, suspended ceilings with light fixtures, and partitions. 其它建筑物恒載包括非結(jié)構(gòu)構(gòu)件的重量，如樓面面層、帶有燈具的吊頂以及隔墻。 7 Loads The forces the act on a structure are called loads. They belong to one of two broad categories, dead load and live load. 作用在結(jié)構(gòu)物上的各種力稱為荷載，它們屬于一兩種廣義類型，恒載和活載。其它要考慮的因素 包括適用性（就外觀和撓曲而言其工作性能如何）。 the engineer must make sure that it doesn?t fall down. 建筑師確定建筑物的外觀，工程師必須確保其不會倒塌。 Ideally, the engineer and architect will collaborate throughout the design process so that the project is pleted in an efficient manner. 在理想狀態(tài)下，工程師和建筑師將在整個設(shè)計(jì)過程中 協(xié)同工作從而高效地完成設(shè)計(jì)工作。 consolidation 19. prescription n. 規(guī)定，命令，藥方； prescribe 20. municipality n. 市政當(dāng)局，直轄市， municipal government 21. specification n. 詳述，規(guī)格 , 規(guī)范； specify 22. mandate n. 書面命令，委托， Phrases and expressions 1. functional design 功能設(shè)計(jì) 2. bending moment 彎矩 3. dead load 4. live load 5. nonstructural ponents 非結(jié)構(gòu)構(gòu)件 6. force due to gravity 7. gravity load 8. building code 6 9. design specifications 設(shè)計(jì)規(guī)程 10. nonprofit anization 非贏利組織，弄 nongovernment anization 11. the National Building Code 12. the Uniform Building Code 13. the Standard Building Code 14. Building Officials and Code Administrators International (BOCA) 國際建筑公務(wù)員與法規(guī)管理人員聯(lián)合會 15. AISC 美國鋼結(jié)構(gòu)學(xué)會 American Institute of Steel Construction 16. AASHTO 美國公路和運(yùn)輸工作者協(xié)會 American Association of State Highway and Transportation Officials 17. AREA 美國鐵道工程協(xié)會 the American Railway Engineering Association 18. AISI 美國鋼鐵學(xué)會 American Iron and Steel Institute Introduction to Structural Design Structural design The structural design of building, 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. 建筑結(jié)構(gòu)設(shè)計(jì)，不論是鋼結(jié)構(gòu)還是鋼筋混凝土結(jié)構(gòu)，都需要確定其支承結(jié)構(gòu)的整體比例和尺寸以及各構(gòu)件的截面尺寸。 assess, assessment 5. fixture vt. fix, fixture 固定設(shè)備，固定物，夾具 6. partition vt. n 分割，劃分， make apart。 5 Lesson 2 Introduction to structural design New words 1. framework frame+work=frame 構(gòu)架，框架 。 Obviously, all columns must be free to deform axially. 顯然，所有柱必須在軸向自由變形 。 The pinnedend condition is one that requires that the member be restrained from lateral translation, but not rotation, at the ends. 鉸結(jié)條件要求約束構(gòu)件兩端不發(fā)生側(cè)移，但并不約束 轉(zhuǎn)動。 As mentioned previously, some accidental moment will be present, but in most cases it can be neglected. 如前所述，可能偶然會存在一些彎矩，但在大多數(shù)情況下都可被忽略。 3. The column is pinned at both ends. 柱在兩端鉸結(jié)。 Effective Length（計(jì)算長度） Both the Euler and tangent modulus equations are based on the following assumptions: 歐拉和切線模量方程都是基于如下假定： 1. The column is perfectly straight, with no initial crookedness. 柱完全豎直，無初始彎曲。 If the stress at which buckling occurs is greater than the proportional limit of the material, the relation between stress and strain is not linear, and the modulus of elasticity E can no longer be used. 如果屈曲發(fā)生時的應(yīng)力大于材料的比例極限，應(yīng)力應(yīng)變關(guān)系就不再是線性的，也不能再用彈性模量 E。 Thus, the minimum moment of inertia and radius of gyration of the cross section should be used in and . 因此，應(yīng)在方程 和 中采用截面的最小慣性矩和最小回轉(zhuǎn)半徑。 If the critical load is divided by the crosssectional area, the critical buckling stress is obtained: 如果將屈曲荷載除以截面面積，便可得到以下屈曲應(yīng)力： 22)/( rL EAPF crcr ??? () This is the pressive stress at which buckling occur about the axis corresponding to r. 這便是繞相應(yīng)于 r 的軸發(fā)生屈曲時的壓應(yīng)力。歐拉公式的有效性（正確性）已由許多試驗(yàn) 充分 證實(shí)。 This remarkable relationship was first formulated by Swiss mathematician Leonhard Euler and published in 1975. 此著名公式是瑞士數(shù)學(xué)家歐拉于 1975 年提 出的。 If the member is so slender (a precise definition of slenderness will be given shortly) that the stress just before buckling is below the proportional limit— that is, the member is still elastic— the critical buckling load is given by 如果構(gòu)件如此細(xì)長（隨后將會給出細(xì)長程度的精確定義）以致即將屈曲時的應(yīng)力低于比例極限 — 即，構(gòu)件仍是彈性的，臨界屈曲荷載如下式給出： 3 22LEIPcr ?? () where E is the modulus of elasticity of the material, I is the moment of inertia of the crosssectional area with respect to the minor principal axis, and L is the length of the member between points of support. 式中 E 為材料彈性模量， I 為關(guān)于截面副主軸的慣性矩， L 為支座間的距離。 For these stocky members and for more slender columns before they buckle, t