【正文】 ound that Euler?s equation did not give reliable results for stocky, or less slender, pression members. 早期的研究者很快發(fā)現(xiàn)對短柱或不太細長的受壓構件，歐拉公式并不能給出可靠的結果， This is because of the small slenderness ratio for members of this type, which results in a large buckling stress (from ). 這是因為這種構件的長細比較小，從而產(chǎn)生較高的屈曲應力。 For to be valid, the member must be elastic, and its ends must be free to rotate but not translate laterally. This end condition is satisfied by hinges or pins. 要使方程 成立，構件必須是彈性的，且其兩端必須能自由轉動，但不能側向移動。受壓構件也存在于桁架和支撐系統(tǒng)中。 slenderness 7. buckle 壓曲，屈曲； buckling load 8. stocky stout 9. convincingly convince, convincing, convincingly 10. stub 樹樁， 短而粗的東西； stub column 短柱 11. curvature 曲率； curve, curvature 12. detractor detract draw or take away。 divert。 Column Theory （柱理論） Consider the long, slender pression member shown in . 考慮如圖 所示的長柱 If the axial load P is slowly applied, it will ultimately reach a value large enough to cause the member to bee unstable and assume the shape indicated by the dashed line. 如果慢慢增加軸向荷載 P，它最終將達到一個足夠大的值使該柱變得不穩(wěn)定 (失穩(wěn) )，如圖中虛線所示。 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)學家歐拉于 1975 年提 出的。 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)生時的應力大于材料的比例極限，應力應變關系就不再是線性的，也不能再用彈性模量 E。 The pinnedend condition is one that requires that the member be restrained from lateral translation, but not rotation, at the ends. 鉸結條件要求約束構件兩端不發(fā)生側移，但并不約束 轉動。 consolidation 19. prescription n. 規(guī)定，命令，藥方； prescribe 20. municipality n. 市政當局，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 功能設計 2. bending moment 彎矩 3. dead load 4. live load 5. nonstructural ponents 非結構構件 6. force due to gravity 7. gravity load 8. building code 6 9. design specifications 設計規(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) 國際建筑公務員與法規(guī)管理人員聯(lián)合會 15. AISC 美國鋼結構學會 American Institute of Steel Construction 16. AASHTO 美國公路和運輸工作者協(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. 建筑結構設計，不論是鋼結構還是鋼筋混凝土結構，都需要確定其支承結構的整體比例和尺寸以及各構件的截面尺寸。 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. 作用在結構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。在許多情況下，必須研究活荷載作用在一給定的結構構件的各個位置以便不會漏掉每個可能的破壞情形。 Design specifications represent what is considered to be good engineering practice based on their latest research. 根據(jù) 其最新研究，設計規(guī)程結出認為是好的工程作法。When the width of this size band is very narrow the soil will be termed poorlygraded, if it is wide the soil is said to be wellgraded. 當這一粒徑范圍非常小時，稱這種土級配較差，而當其較大時，稱這種土級配良好。 From these figures the particlesize distribution for the soil is plotted as a semilogarithmic curve () known as grading curve. 根據(jù)這些數(shù)據(jù)，以半對數(shù)曲線的形 式描出該土的粒徑分布圖，即所謂的級配曲線。 A process of sedimentation is normally carried out for this purpose. 通常必須用沉降法實現(xiàn)此目的。 Grading Characteristics The grading curve is a graphical representation of the particlesize distribution and is therefore useful in itself as a means of describing the soil. 級配曲線是粒徑分布的一種圖形表達，因而可用來作為描述土的手段。 只有 30%土樣通過的最大粒徑； D60= maximum size of the smallest 60 percent of the sample；只有 60%土樣通過的最大粒徑； From these characteristic sizes, the following grading characteristics are defined: 根據(jù)這些特征粒徑，定義出如下級配特征： Effective size 有效粒徑 Uniformity coefficient 均勻系數(shù) 19 Coefficient of gradation 級配系數(shù) Lesson 4 New Words 1. undergo [??nd????u] vt. 經(jīng)歷 , 遭受 , 忍受 。 sustainable development 18. fatigue [f??ti:?]n. 疲乏 , 疲勞 , , vi.疲勞 strength 21 試驗物 。 As concrete continues to dry, water evaporates and the volume of the restrained cement paste changes, causing concrete to shrink, probably due to the capillary tension that develops in the water remaining in concrete. 隨著混凝土的不斷變干，水分蒸發(fā)，受約束水泥漿的體積也變化，導致了混凝土的收縮，這多半是由于殘留在混凝土中的水的毛細張力所致。 and shape of specimen. As shrinkage takes place in a reinforced concrete member, tension stresses develop in the concrete, and equal pressive develop in the steel. These stresses are added to those developed by the loading action. Therefore, cracks may develop in concrete when a high percentage of steel is used. Proper distribution of reinforcement, by producing better distribution of tensile stresses in concrete, can 26 reduce differential internal stresses. 試件的尺寸和形狀：當收縮在鋼筋混 凝土構件中發(fā)生時，混凝土中產(chǎn)生拉應力，同樣大小的壓力產(chǎn)生于鋼筋中，這些力與荷載引起的力相迭加。鋼筋的合理分布、會使混凝土中的拉應力分布更有利，可減小內部應力差。 Many factors influence the shrinkage of concrete caused by the variations in moisture conditions. 許多因素都會影響因水分環(huán)境發(fā)生變化而產(chǎn)生的混凝土收縮。 water content 2. cement paste 水泥漿 mortar 3. capillary tension 毛細管張力，微張力 4. gradation of aggregate 骨 料 級配 coarse fine (crushed stone, gravel) 5. The British Code PC100 英國混凝土規(guī)范 PC100。 ascribe ， impute ， credit， assign， refer 4. shrinkage shrink 10. distribution [?distri?bju:??n]n. 分配 , 分發(fā) distribute distributor 11. upwind [??p?wind]adj. 逆風的 adv. 逆 風 地