外文翻譯--結(jié)構(gòu)設(shè)計(jì)原理

1、<p><b>　　附錄</b></p><p>　　Philosophy of Structural Design</p><p>　　A structural engineering project can be divided into three phases: planning, design, and construction.</p>

2、;<p>　　Structural design involves determining the most suitable proportions of a structure and dimensioning the structural elements and details of which it is composed. This is the most highly technical and mathem

3、atical phase of a structural engineering project, but it cannot-and certainly should not-be conducted without being fully coordinated with the planning and construction phases of the project. The successful designer is a

4、t all times fully conscious of the various considerations that were involv</p><p>　　Specially, the structural design of any structure first involves the establishment of the loading and other design conditio

5、ns that must be resisted by the structure and therefore must be considered in its design. Then comes the analysis (or computation ) of the internal gross forces (thrust, shears, bending moments, and twisting moments), st

6、ress intensities, strains, deflections, and reactions produced by the loads, temperature, shrinkage, creep, or other design conditions. Finally comes the pro</p><p>　　Depending on the type of structure and t

7、he conditions involved, the stress intensities computed in the analytical model of the actual structure for the assumed design conditions may or may not be in close agreement with the stress intensities produced in the a

8、ctual structure by the actual conditions to which it is exposed. The degree of correspondence is not important, provided that the computed stress intensities can be interpreted in terms of previous experience. The select

9、ion of the service c</p><p>　　The allowable-stress approach has an important disadvantage in that it does not provide a uniform overload capacity for all parts and all types of structures. As a result, there

10、 is today a rapidly growing tendency to base the design on the ultimate strength and serviceability of the structure, with the older allowable-stress approach serving as an alternative basis for design. The newer approac

11、h currently goes under the name of strength design in reinforce-concrete design literature and plastic </p><p>　　Proponents of this latter approach argue that it results in a more realistic design with a mor

12、e accurately provided margin of strength over the anticipated service conditions. These improvements result from the fact that nonelastic and nonlinear effects that become significant in the vicinity of ultimate behavior

13、 of the structure can be accounted for.</p><p>　　In recent decades, there has been a growing concern among many prominent engineers that not only is the term “factor of safety” improper and unrealistic, but

14、worse still a structural design philosophy based on this concept leads in most cases to an unduly conservative and therefore uneconomical design, and in some cases to an unconservative design with too high a probability

15、of failure. They argue that there is no such thing as certainty, either of failure or of safety of a structure but only a </p><p>　　If a good alignment requires a curved bridge-over a part or the total lengt

16、h then all external longitudinal lines or edges of the structure should be parallel to the curved axis, thereby following again the guideline of good order.</p><p>　　The transverse axis of piers or groups of

17、 columns should be rectangular (radial) to the curved axis, unless skew crossings over roads or rivers enforce other directions.</p><p>　　The requirements of traffic design result occasionally in very acute

18、angles or in level branching which cause difficulties for the bridge engineer to find pleasing solutions for the bridges.</p><p><b>　　結(jié)構(gòu)設(shè)計(jì)原理</b></p><p>　　一個(gè)結(jié)構(gòu)設(shè)計(jì)工程可以被分為三個(gè)階段：計(jì)劃、設(shè)計(jì)、施工。

19、</p><p>　　結(jié)構(gòu)設(shè)計(jì)包含確定結(jié)構(gòu)最合適的比例并且測(cè)量單元體的尺寸及其包含的細(xì)部。這是一項(xiàng)結(jié)構(gòu)工程中技術(shù)性和數(shù)學(xué)性最強(qiáng)的一個(gè)階段，但是如果不能全面的與計(jì)劃和施工階段相協(xié)調(diào)的話，它是不能被進(jìn)行的。成功的設(shè)計(jì)者在任何時(shí)候都能全面地考慮到結(jié)構(gòu)初步設(shè)計(jì)中包含的各種因素，同時(shí)還充分考慮到以后施工中可能遇到的各種問題。</p><p>　　尤其，任何一個(gè)結(jié)構(gòu)的結(jié)構(gòu)設(shè)計(jì)首先包括結(jié)構(gòu)所必須抵抗的荷

20、載及其它設(shè)計(jì)因素的確定，因此，在設(shè)計(jì)中必須考慮到。然后開始分析（或計(jì)算）由荷載、收縮、徐變或其它設(shè)計(jì)因素引起的總內(nèi)力（推力、剪力、彎矩和扭矩），應(yīng)力強(qiáng)度、應(yīng)變、變形及反力等。最后是比例的確定和選擇構(gòu)件和連結(jié)件的材料，用來充分的抵抗由設(shè)計(jì)條件帶來的影響效應(yīng)，這種用來評(píng)斷特定的比例是否會(huì)帶來想要的結(jié)構(gòu)的標(biāo)準(zhǔn)反映出你的知識(shí)的積累程度、直覺以及判斷。常見的土木工程結(jié)構(gòu)例如橋梁、建筑，過去的這種做法是在比較應(yīng)力強(qiáng)度以及由使用荷載和其它設(shè)計(jì)因素引起

21、的應(yīng)力強(qiáng)度的基礎(chǔ)上設(shè)計(jì)的。這種傳統(tǒng)的設(shè)計(jì)被稱作彈性設(shè)計(jì)，因?yàn)樵试S應(yīng)力強(qiáng)度是按照這樣一種理念進(jìn)行選擇的，即材料的拉、壓允許應(yīng)力與屈服強(qiáng)度相同并且不能超過結(jié)構(gòu)的最大應(yīng)力。當(dāng)然，考慮到垮塌的可能性及結(jié)構(gòu)的允許變形，對(duì)允許應(yīng)力強(qiáng)度的選擇可作適當(dāng)?shù)男拚?lt;/p><p>　　根據(jù)結(jié)構(gòu)的類型和所包含的條件，對(duì)于在假定的條件下在實(shí)際結(jié)構(gòu)的分析模型中所計(jì)算得的應(yīng)力強(qiáng)度與在實(shí)際的承載條件下實(shí)際構(gòu)件所產(chǎn)生的應(yīng)力強(qiáng)度可能相似也可能不同

22、。當(dāng)計(jì)算得的應(yīng)力強(qiáng)度可以被先前的經(jīng)驗(yàn)所解釋和肯定時(shí)，這種相似度就不再重要了。使用條件和允許應(yīng)力強(qiáng)度的選擇應(yīng)該相對(duì)垮塌留有一定的安全余地，這種安全余地大小的選擇取決于荷載、分析、設(shè)計(jì)、材料和施工的不確定程度及垮塌將引起的后果。例如：一個(gè)允許抗拉強(qiáng)度為20000磅每立方英寸的結(jié)構(gòu)采用抗拉強(qiáng)度為33000磅每立方英寸的鋼材，則相對(duì)于抗拉屈服強(qiáng)度的安全余地為33000/20000，即1.65。</p><p>　　允許應(yīng)

23、力法有一個(gè)嚴(yán)重的缺陷，也就是它不能為各類結(jié)構(gòu)及其構(gòu)件給出一個(gè)統(tǒng)一的超載能力。因此在今天有這樣一種快速發(fā)展的趨勢(shì)，即把設(shè)計(jì)建立在極限強(qiáng)度和結(jié)構(gòu)實(shí)驗(yàn)基礎(chǔ)之上，將舊的允許應(yīng)力法作為設(shè)計(jì)的一種供選擇的方法。這種新的方法在鋼筋混凝土設(shè)計(jì)文獻(xiàn)和剛結(jié)構(gòu)彈性設(shè)計(jì)文獻(xiàn)中被稱為強(qiáng)度設(shè)計(jì)。當(dāng)在強(qiáng)度設(shè)計(jì)的基礎(chǔ)確定比例時(shí)，參與的實(shí)際荷載會(huì)首先乘以一個(gè)合適的荷載分項(xiàng)系數(shù)（大于1），這個(gè)荷載的大小取決于荷載的不確定度，它在結(jié)構(gòu)的生命周期內(nèi)改變的可能性和荷載的聯(lián)合作用

24、的可能性，頻率以及特殊的聯(lián)合作用的持續(xù)性。當(dāng)這種方法應(yīng)用于鋼筋混凝土設(shè)計(jì)時(shí)，鑒于材料在強(qiáng)度、工藝和尺寸上的不利的變化，結(jié)構(gòu)單元的理論承載力會(huì)由于乘了一個(gè)承載力折減系數(shù)而降低。此時(shí)結(jié)構(gòu)的比例會(huì)由以下主導(dǎo)因素確定，逐步增大的荷載將會(huì)導(dǎo)致（1）疲勞、彎曲或脆斷（2）或在某一內(nèi)部截面產(chǎn)生屈服（3）或使結(jié)構(gòu)產(chǎn)生彈性位移（4）或者使整個(gè)結(jié)構(gòu)處于垮塌的邊緣。</p><p>　　后種方法的支持者聲稱它可以產(chǎn)生一個(gè)更實(shí)際的設(shè)計(jì)以

25、及提供一個(gè)比實(shí)際參與的條件更精確的強(qiáng)度留余。這種改進(jìn)源于這樣一種事實(shí)，即在結(jié)構(gòu)的極限附近的非線形和線形可以得到解釋和說明。</p><p>　　近十幾年來，許多杰出的工程師越來越觀注到安全系數(shù)這種方法的不合適和不切實(shí)際而且基于這一概念的結(jié)構(gòu)的理性設(shè)計(jì)也變的更加糟糕，導(dǎo)致了許多設(shè)計(jì)方案的過度的保守，以至于由此產(chǎn)生的不經(jīng)濟(jì)的設(shè)計(jì)和一些情況下的破壞概率較高的冒險(xiǎn)設(shè)計(jì)。他們宣稱不論是結(jié)構(gòu)的安全或破壞，都不存在確定的事實(shí)，

26、而反之是安全的概率或破壞的概率。因此，他們覺得荷載效應(yīng)的變化和結(jié)構(gòu)抵抗力的變化應(yīng)該應(yīng)用統(tǒng)計(jì)的方法進(jìn)行研究，并且對(duì)結(jié)構(gòu)的耐用性和使用性進(jìn)行估計(jì)。這種方法也許不適用于單個(gè)結(jié)構(gòu)的單元的設(shè)計(jì)，然而它在框架設(shè)計(jì)的規(guī)則和規(guī)定中它是適用的。建設(shè)法規(guī)和特殊規(guī)定高度的認(rèn)同并清楚的說明了設(shè)計(jì)師們所反映的因素和相應(yīng)的可能性。</p><p>　　如果一個(gè)好的線型需要一個(gè)曲線橋——一部分或是全部的長(zhǎng)度，則所有的外部縱向線或結(jié)構(gòu)的邊緣應(yīng)當(dāng)