外文翻譯---通過建筑結(jié)構(gòu)設(shè)計(jì)以改善建筑物的抗倒性(文件)
【正文】 ght reasonably be taken into account for those structural designs where it was considered appropriate. In doing this it is, of course, essential to include both the risk of a triggering incident and the consequences of a failure so that the resulting more onerous structural demands are used appropriately. Arguably, a disproportionate response in terms of requiring costly additional provisions in cases where the risks/consequences are very low/very minor may be as harmful as failing to address those cases where the risks/consequences are high/severe. This paper will review current approaches to design to resist progressive collapse and contrast these with work undertaken over the past seven years at Imperial College London, where the goal has been the provision of a realistically based method suitable for use in routine design. The essential features of the method will be presented, its use on several examples described and results presented to illustrate how it is leading to a better understanding of both the mechanics of progressive collapse and the ways in which structural engineers can best configure their structures so as to provide enhanced resistance to resist progressive collapse The two most frequently used design approaches intended to address the issue of progressive collapse are:*c Providing tying capacity *c Checking alternate load pathsFigure 1: Tie Forces in a Frame Structure The first is essentially prescriptive and consists of ensuring that beams, columns, connections and floor (or roof) can act together to provide a specified minimum level of horizontal tying resistance。 the best of these–which are likely to be putationally very demanding–have demonstrated their ability to closely replicate actual observed behaviour.3. Essential features of progressive collapse Three features have previously (Nethercot 2010) being identified as essential ponents of any reasonably realistic approach to design against progressive collapse:*c Events take place over a very short timescale and the actual failure is therefore dynamic.*c It involves gross deformations, generating large strains, leading to inelastic behaviour as well as change of geometry effects.*c Failure essentially corresponds to an inability of the structure in its damaged state to adopt a new position of equilibrium without separation of key elements.Figure 2: Simplified multilevel approach for progressive collapse assessment Additional features, designed to make the approach attractive for use by practicing Engineers have also been proposed (Nethercot 2010):*c Process should consist of a series of steps broadly similar in concept to those used for “conventional” structural design.*c It should, preferably, be capable of implementation at a variety at levels of plexity–with the choice reflecting the importance of the structure.*c Any required analysis should utilise familiar techniques。在過去的幾十年，從來自世界各地的插圖畫開始，到高高的世貿(mào)中心倒塌為止，這些功能必不可少的為具有代表性的治療和早期的設(shè)計(jì)方法進(jìn)行了綜述。*c 改進(jìn)過的性能的科學(xué)知識。所以問題不是以前認(rèn)為（或只允許在一個隱式的,基本上復(fù)制過去的令人滿意的性能,方式）開始需要顯式的形式的關(guān)注：需求評估，模型行為和識別合適的失效準(zhǔn)則。不僅導(dǎo)致了在某種意義上不提供防火時明顯的經(jīng)濟(jì)效益,在它給了只有微不足道的好處的時候；它也導(dǎo)致了消防安全通道更好的調(diào)節(jié)原則的理解和明智的行事能力在設(shè)計(jì)適合安排一個合適的評估基礎(chǔ)上的需要。最終，合理設(shè)計(jì)的預(yù)處理的好處是公認(rèn)的，安全的方法來安裝燃?xì)庠O(shè)計(jì)然后開始進(jìn)入工業(yè)?？梢哉f，一個不成比例的反應(yīng)在風(fēng)險/后果是很低/很輕的地方要求昂貴的附加條款的情況下，也許如同未能解決那些情況在風(fēng)險/后果是高/嚴(yán)重的地方一樣有害。圖1，這個來自最近的US Guidance，演示了
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