外文翻譯---通過建筑結(jié)構(gòu)設(shè)計以改善建筑物的抗倒性

1、外文原稿2The Twelfth East Asia-Pacific Conference on Structural Engineering and Construction Design of Building Structures to Improve their Resistance to Progressive Collapse D A Nethercota a Department of Civil and Environmental Engineering, Imperial College LondonAbstract：It is rare nowadays for a “ne

2、w topic” to emerge within the relatively mature field of Structural Engineering. Progressive collapse-or, more particularly, understanding the mechanics of the phenomenon and developing suitable ways to accommodate its consideration within our normal frameworks for structural design-can be so regard

3、ed. Beginning with illustrations drawn from around the world over several decades and culminating in the highly public WTC collapses, those features essential for a representative treatment are identified and early design approaches are reviewed. More recent work is then reported, concentrating on d

4、evelopments of the past seven years at Imperial College London, where a comprehensive approach capable of being implemented on a variety of levels and suitable for direct use by designers has been under development. Illustrative results are used to assist in identifying some of the key governing fea

5、tures, to show how quantitative comparisons between different arrangements may now be made and to illustrate the inappropriateness of some previous design concepts as a way of directly improving resistance to progressive collapse.2011 Published by Elsevier Ltd. Keywords: Composite structures; Progre

6、ssive Collapse; Robustness; Steel structures; Structural design1. Introduction Over time various different structural design philosophies have been proposed, their evolutionary nature reflecting：*cGrowing concern to ensure adequate performance. *cImproved scientific knowledge of behaviour. *c Enhanc

7、ed ability to move from craft based to science based and thus from prescriptive to quantitatively justified approaches This can be traced through concepts such as: permissible stress, ultimate strength, limit states and performance based. As clients, users and the general public have become increasi

8、ngly sophisticated and thus more demanding in their expectations, so it became necessary for designers to cover an ever increasing number and range of structural issuesmostly through consideration of the “reaching this condition would be to a greater or lesser extent unacceptable” approach. Therefor

9、e issues not previously considered (or only allowed for in an implicit, essentially copying past satisfactory performance, way) started to require explicit attention in the form of: an assessment of demand, modelling behaviour and identification of suitable failure criteria. The treatment of topics

10、such as fatigue, fire resistance, durability and serviceability can all be seen to have followed this pattern. To take a specific example: designing adequate fire resistance into steel framed buildings began (once the need had been recognised) with simple prescriptive rules for concrete encasement o

11、f vulnerable members but it has, in recent years, evolved into a sophisticated discipline of fire engineering, concerned with fire loading, the provision of protective systems such as sprinklers, calculation of response in the event of a fire and the ability to make quantitative comparisons between

12、alternative structural arrangements. Not only has this led to obvious economic benefits in the sense of not providing fire protection where it gave only negligible benefit, it has also led to increased fire safety through better understanding of the governing principles and the ability to act intell

13、igently in designing suitable arrangements based on a proper assessment of need. Prior to the Ronan Point collapse in London in 1968 the terms robustness, progressive collapse,disproportionate collapse etc., were not part of Structural Engineering vocabulary. The consequences of the damage done to t

14、hat 22 storey block of pre-cast concrete apartments by a very modest gas explosion on the 18th floor led to new provisions in the UK Building Regulations, outlawing for many years of so called system built schemes, demolition of several completed buildings, temporary removal of gas in high rise cons

15、truction and the formation of the Standing Committee on Structural Safety. Eventually, the benefits of properly engineered pre-fabrication were recognised, safe methods for the installation of gas were devised and the industry moved on. However, the structural design guidance produced at that time -

16、 that still underpins much present day provision - was essentially prescriptive in nature with no real link to actual performance. Subsequent incidences of progressive collapse such as the Murragh Building and the World Trade Centre brought increased attention to the actual phenomenon and issues of

17、how it might 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

18、 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 appr

19、oaches 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 present

20、ed, 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 resistance2.Design to resis

21、t progressive collapse The two most frequently used design approaches intended to address the issue of progressive collapse are:*cProviding tying capacity *cChecking alternate load pathsFigure 1: Tie Forces in a Frame Structure The first is essentially prescriptive and consists of ensuring that beam

22、s, columns, connections and floor (or roof) can act together to provide a specified minimum level of horizontal tying resistance; the actual values required are normally related to the vertical loading. Figure 1, which is taken from recent US Guidance (SEI 2010), illustrates the principle. The appro

23、ach is simple to appreciate, requires minimal structural calculation and, in situations where the original provisions are found to be inadequate, can be made to work by providing more substantial connections and/or additional reinforcement in floor slabs In an interesting recent development, that re

24、cognizes the link to the generation of catenary action, US Guidance has restricted the use of tying between the structural members to situations in which it can be demonstrated that the associated connections can carry the required forces whilst undergoing rotations of 0.2 radiance. Where this is no

25、t possible, tying should act through the floors and the roof. However, recent studies (Nethercot et al 2010a; Nethercot et al 2010b) have suggested that tying capacity correlates poorly with actual resistance to progressive collapse. Moreover, being prescriptive, it does not permit the meaningful co

26、mparison of alternative arrangements - a fundamental feature of structural design. In its most frequently used form the alternative load path approach presumes the instantaneous loss of a single column and then requires that the ability of the resulting damaged structure to bridge the loss be demons

27、trated by suitable calculation (Gudmundsson and Izzuddin 2010). The approach may be implemented at varying levels of sophistication in terms of the analysis; for example, recent thinking in the United States (SEI 2010) makes provision for any of: linear static, non-linear static or non-linear dynami

28、c analysis and provides some guidance on the use of each. It may also be used as the basis for more sophisticated numerical studies of particular structures and particular incidents e.g. forensic work; the best of thesewhich are likely to be computationally very demandinghave demonstrated their abil

29、ity to closely replicate actual observed behaviour.3. Essential features of progressive collapse Three features have previously (Nethercot 2010) being identified as essential components of any reasonably realistic approach to design against progressive collapse:*cEvents take place over a very short

30、timescale and the actual failure is therefore dynamic.*cIt involves gross deformations, generating large strains, leading to inelastic behaviour as well as change of geometry effects.*cFailure essentially corresponds to an inability of the structure in its damaged state to adopt a new position of eq

31、uilibrium without separation of key elements.Figure 2: Simplified multi-level approach for progressive collapse assessment Additional features, designed to make the approach attractive for use by practicing Engineers have also been proposed (Nethercot 2010):*cProcess should consist of a series of st

32、eps broadly similar in concept to those used for “conventional” structural design.*cIt should, preferably, be capable of implementation at a variety at levels of complexitywith the choice reflecting the importance of the structure.*cAny required analysis should utilise familiar techniques; where the

33、se require computations beyond “hand methods”, these should be based on the use of available analysis software.*cA realistic and recognisable criterion of failure should be used.*cApproach should permit study of cause and effect and be suitable for the making of quantitative comparisons. It was agai

34、nst this background that the studies at Imperial College London have been undertaken. An approach incorporating the three essential features but observing the five desirable features was originally developed (Vlassis 2007); it has subsequently been refined (Stylianidis 2010). Although the starting p

35、oint was column removal, the approach contains a number of distinctive features:*cAlthough dynamic response is allowed for, only static analysis is required (Izzuddin et al 2007).*cThe approach may be implemented at structure, sub-structure, floor grillage or individual beam level, see Figure 2.*cA

36、realistic criterion of failure is employed, corresponding to reaching the ductility limits in connections.*cQuantitative comparisons between alternative structural arrangements may readily be made.*cThe approach may be implemented using only explicit formulae, thereby permitting simple and rapid cal

37、culation.Full details of the method, both in its original form which utilises ADAPTIC to perform the calculations and in its simplified form, may be found in the series of Imperial papers (2-12).*a)First yielding of the tensile components (top bolt row of the support connection)*b)Ultimate capacity

38、of the beam flange at one of the connections (support)*c)Ultimate capacity of the system (failure of the bottom bolt row of the mid-span connection)*d)The axial load becomes zero (the deflection of the beam where the axial load changes from compressive to tensile)*e)The deflection of the beam where

39、the axial load becomes equal to the flange capacity of one of the connections (mid-span connection)Figure 3: Non-linear static response for a single beam 中文翻譯2通過建筑結(jié)構(gòu)設(shè)計以改善建筑物的抗倒性D A Nethercota 土木與環(huán)境工程學(xué)院倫敦帝國學(xué)院摘 要：如今的“新話題”出現(xiàn)在相對成熟的結(jié)構(gòu)工程領(lǐng)域這是一件罕見的事?？惯B續(xù)倒塌，或者，更特別的是，了解力學(xué)的現(xiàn)象和發(fā)展適當(dāng)?shù)姆绞?，以適應(yīng)我們正常的框架內(nèi)審議的結(jié)構(gòu)設(shè)計，可以這么認為。在

40、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)計方法進行了綜述。最近的工作是當(dāng)時的報道，集中精力在過去7年在倫敦大學(xué)帝國學(xué)院的發(fā)展，在一個能使用各種水平和由設(shè)計師一直在發(fā)展適合直接使用的綜合方法。說明性的結(jié)果是用來幫助發(fā)現(xiàn)一些關(guān)鍵的管理功能，去展示如何定量比較安排現(xiàn)在可能使和說明赫爾墨斯的一些以前的設(shè)計概念之間的不同來直接改善抗倒性。關(guān)鍵詞：復(fù)合結(jié)構(gòu)，漸進式折疊，魯棒性，鋼鐵結(jié)構(gòu)，結(jié)構(gòu)設(shè)計1.引言隨著時間的推移各種不同的結(jié)構(gòu)設(shè)計原理被提出,他們發(fā)展的自然回想：*c越來越關(guān)注確保足夠的性能。*c改進過的性能的科學(xué)知識。*c加強能

41、力從工藝為基礎(chǔ)的移動科學(xué)依據(jù)從而從規(guī)范的定量合理的方法。這可以通過追蹤的概念,如:容許應(yīng)力，強度極限，極限狀態(tài)和基礎(chǔ)性能。作為客戶：用戶和公眾已經(jīng)變得越來越復(fù)雜,因此要求更高的期望，因此，它成為必要的設(shè)計師代替一個永久的越來越多的結(jié)構(gòu)性問題的范圍的主要是通過考慮達到這個條件將或多或少受到不可接受的方法。所以問題不是以前認為（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。論題的處理比如疲勞，耐火性，耐久性和適用性都可以被看作是這個模式。舉一個具體的例子：設(shè)計充分耐火鋼框架建筑開始(已經(jīng)被認可的)和簡單的法定規(guī)則對混凝

42、土外層脆弱的構(gòu)件。但是,近年來,發(fā)展成為一個復(fù)雜的消防工程學(xué)科，關(guān)心火災(zāi)荷載，提供防護系統(tǒng),如灑水裝置，在發(fā)生火災(zāi)情況下的反應(yīng)的計算,能夠使定量對比結(jié)構(gòu)安排之間選擇。不僅導(dǎo)致了在某種意義上不提供防火時明顯的經(jīng)濟效益,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)計適合安排一個合適的評估基礎(chǔ)上的需要。在羅南點于1968年在倫敦坍塌之前，魯棒性原則，抗連續(xù)性倒塌，非比例破壞等是不屬于工程詞匯里的。這棟在18層發(fā)生瓦斯爆炸被破壞的22層預(yù)制混凝土公寓建筑導(dǎo)致了新的英國建筑法規(guī)誕生。取締了多年來所謂的系統(tǒng)構(gòu)建方案，拆除了幾個完整的建筑物，排除高層建筑物

43、里的臨時瓦斯和建立建構(gòu)安全方面的常務(wù)委員會。最終，合理設(shè)計的預(yù)處理的好處是公認的，安全的方法來安裝燃氣設(shè)計然后開始進入工業(yè)。然后，結(jié)構(gòu)設(shè)計指導(dǎo)在當(dāng)時產(chǎn)生仍然決定了很多現(xiàn)在的條款是自然本質(zhì)上的處方式,沒有真正的鏈接到實際的性能。后來，連續(xù)倒塌的發(fā)生率如同Murragh Building和世貿(mào)中心帶來增加如何合理地考慮那些結(jié)構(gòu)的設(shè)計實際現(xiàn)象和問題的關(guān)注，它被認為是合適的。在這樣做,當(dāng)然,至關(guān)重要的風(fēng)險,包括一個觸發(fā)事件和失敗的結(jié)果,所以更繁重的結(jié)構(gòu)要求被適當(dāng)?shù)厥褂?。可以說，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/嚴重的地

44、方一樣有害。本文將回顧當(dāng)前用來設(shè)計抵制連續(xù)倒塌的方法和對比過去七年在倫敦大學(xué)帝國理工學(xué)院進行的這些工作，那里的目標(biāo)是提供一個依據(jù)于實際方法適合用在常規(guī)設(shè)計。方法的基本特征將被提交，它被使用在幾個例子的描述和結(jié)果來說明它是如何導(dǎo)致更好的連續(xù)倒塌的機制的原理和結(jié)構(gòu)工程師的方式能最好的配置結(jié)構(gòu),以提供增強的抗性。2.設(shè)計抵抗連續(xù)倒塌兩種最常用設(shè)計方法旨在解決連續(xù)倒塌這一問題：*c提供綁扎能力*c檢查交替的荷載通道圖1:領(lǐng)帶部隊在一個框架結(jié)構(gòu)首先，本質(zhì)上的規(guī)范和包括確保梁，柱，樓梯和樓板（或者屋蓋）可以聯(lián)合起來提供一個規(guī)定的低級的水平聯(lián)系抗力等級；垂直荷載的實際值要求是通常有相關(guān)的。圖1，這個來自最近

45、的US Guidance，演示了原理。這個方法對于觀察是簡單的，只需要很少的結(jié)構(gòu)計算和在最初的規(guī)定被發(fā)現(xiàn)是不充分的的情況下，能通過提供更多的實質(zhì)性的連接或在一個有趣的近代發(fā)展中水泥樓板中施加額外加固，認識到鏈?zhǔn)椒磻?yīng)的連接的生成，US Guidance已經(jīng)限制可以展示相關(guān)的連接可以攜帶所需的彈性元件同時進行0.2光輝的旋轉(zhuǎn)的情況的結(jié)構(gòu)構(gòu)件之間的綁扎的使用。這是不可能的，連系材料應(yīng)該通過樓板和屋蓋。無論如何，近代研究（Nethercot et al 2010a; Nethercot et al 2010b）都建議綁扎力相關(guān)較弱和實際抗力去抗連續(xù)倒塌。此外，它被規(guī)范不允許有意義的替代安排的比較結(jié)構(gòu)設(shè)

46、計的一個基本特征。在其最頻繁使用的形式替代負載路徑方法假定一個單柱的瞬時損耗，然后需要這作為結(jié)果的被損傷的構(gòu)件的能力去渡過這個損失已經(jīng)被合適的計算證明（Gudmundsson and Izzuddin 2010）。該方法可以在分析方面的高度化的不同程度被實現(xiàn)；比如，在美國最近的研究為線性靜力分析，非線性靜態(tài)或非線性動態(tài)分析制定規(guī)定和為各自的使用提供一些指導(dǎo)。它也可以被使用作為基點為特定結(jié)構(gòu)或特定工作（如法醫(yī)）的更精致的數(shù)字的研究；最好的這些可能是計算非常苛刻的已經(jīng)證明了他們的能力去緊密地復(fù)制的真實的可觀察的特性。3.抗連續(xù)倒塌的基本特性三個特征已經(jīng)預(yù)先被鑒證出作為任何合理的現(xiàn)實的方法去設(shè)計對抗

47、連續(xù)倒塌的必要部分：*c事件發(fā)生在非常短的時間段內(nèi)和正在的失敗是因此動態(tài)。*c它包括總變形，發(fā)生大應(yīng)變，導(dǎo)致非彈性行為和幾何效果的改變一樣。*c失敗基本上對應(yīng)于在受損狀態(tài)下構(gòu)件的無能通過一個新的沒有關(guān)鍵元素的分離的平衡位置圖2:簡化的多層次評估方法抗連續(xù)倒塌附加裝置也有人提出，為了讓這種方法被工程師使用。*c程序應(yīng)該由一序列的在概念中廣泛相似于那些用于“傳統(tǒng)”的結(jié)構(gòu)設(shè)計的步驟構(gòu)成*c從實際出發(fā)，合理的，能夠?qū)崿F(xiàn)在一個復(fù)雜水平上的一個品種伴隨選擇反映結(jié)構(gòu)的重要性。*c任何必需的驗定都應(yīng)該利用熟悉的技術(shù)；這里需要的計算多于“手工”，是基于可用的分析軟件的使用的計算。*c一個現(xiàn)實的知名的破壞的準(zhǔn)則應(yīng)

48、該被使用。*c方法應(yīng)該允許原因和結(jié)果研究和適用于定量判斷的制定。 正是在這樣的背景之下,倫敦帝國學(xué)院的研究正在進行。一個結(jié)合了三個基本特征但是觀察五個理想功能的方法最初被開發(fā)（Vlassis 2007）；它后來被開發(fā)的跟精確（Stylianidis 2010）。盡管出發(fā)點是柱移動，但該方法包含一些獨特的特性：*c雖然動態(tài)反應(yīng)是被允許的，但是只有靜態(tài)分析是必需的（Izzuddin et al 2007）。*c該方法可以實現(xiàn)在結(jié)構(gòu)，亞結(jié)構(gòu)，地板格柵或單梁的標(biāo)準(zhǔn)（見圖2）.*c一個現(xiàn)實的破壞標(biāo)準(zhǔn)被采用，對應(yīng)于在連接中到達延性限制。*c定量對比替代結(jié)構(gòu)安排可能容易就能做出。*c該方法可以實現(xiàn)只使用顯式

49、公式，從而允許簡單和快速計算。該方法的完整細節(jié)，無論是原來利用ADAPTIC執(zhí)行計算的形式還是在它的簡化形式，應(yīng)該都能在帝國文件中被找到（2-12）。 圖3：單梁的非線性靜力反應(yīng)*a)首先拉力組件的產(chǎn)生（支撐連接的頂級螺栓排）*b)其中的一個連接（支撐）的光束翼緣的總功率*c)系統(tǒng)的總功率（底部中跨連接的螺栓行的破壞）*d)軸向載荷變成零（在軸向載荷從抗壓到抗拉變化的地方的梁的撓度）*e)一個連接的翼緣力在軸向荷載變相等的地方的梁的撓度參考文獻1 Gudmundsson GV and Izzuddin BA. The Sudden Column Loss Idealisation for Di

50、sproportionate Collapse Assessment. The Structural Engineer; 2010. 88 pp. 22-26. 2 Izzuddin BA, Vlassis AG, Elghazouli AY, and Nethercot DA. Assessment of Progressi ve Collapse of Multi-Storey Buildings. Proceedings ICE Structures and Buildings; 2007, Vol. 160. No. SB4 pp. 197-206. 3 Izzuddin BA, Vlassis AG, Elghazoul