1、<p><b>　　外文原稿2</b></p><p>　　The Twelfth East Asia-Pacific Conference on Structural Engineering and Construction</p><p>　　Design of Building Structures to Improve their Resistanc

2、e</p><p>　　to Progressive Collapse</p><p>　　D A Nethercota</p><p>　　a Department of Civil and Environmental Engineering, Imperial College London</p><p>　　Abstract：It is

3、 rare nowadays for a “new 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 w

4、ays to accommodate its consideration within our normal frameworks for structural design-can be so regarded. Beginning with illustrations drawn from around the world over several decades and culminating in the highly pub

5、lic WTC collapses, those features essential fo</p><p>　　2011 Published by Elsevier Ltd. </p><p>　　Keywords: Composite structures; Progressive Collapse; Robustness; Steel structures; Structural d

6、esign</p><p>　　1. Introduction </p><p>　　Over time various different structural design philosophies have been proposed, their evolutionary nature reflecting：</p><p>　　*Growing conc

7、ern to ensure adequate performance. </p><p>　　*Improved scientific knowledge of behaviour. </p><p>　　* Enhanced ability to move from craft based to science based and thus from prescriptive to

8、 quantitatively justified approaches</p><p>　　This can be traced through concepts such as: permissible stress, ultimate strength, limit states and performance based. As clients, users and the general public

9、 have become increasingly sophisticated and thus more demanding in their expectations, so it became necessary for designers to cover an ever increasing number and range of structural issues–mostly through consideration o

10、f the “reaching this condition would be to a greater or lesser extent unacceptable” approach. Therefore issues not pre</p><p>　　To take a specific example: designing adequate fire resistance into steel fram

11、ed buildings began (once the need had been recognised) with simple prescriptive rules for concrete encasement of vulnerable members but it has, in recent years, evolved into a sophisticated discipline of fire engineering

12、, 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 alternative</p><p&

13、gt;　　Prior to the Ronan Point collapse in London in 1968 the terms robustness, progressive collapse,</p><p>　　disproportionate collapse etc., were not part of Structural Engineering vocabulary. The consequen

14、ces of the damage done to that 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

15、system built schemes, demolition of several completed buildings, temporary removal of gas in high rise construction and the formation of the Standing Committee on Structural Safety. E</p><p>　　Subsequent inc

16、idences of progressive collapse such as the Murragh Building and the World Trade Centre brought increased attention to the actual phenomenon and issues of how it might reasonably be taken into account for those structura

17、l 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 d

18、emands are used appropriately. Arguably, a dis</p><p>　　This paper will review current approaches to design to resist progressive collapse and contrast these with work undertaken over the past seven years at

19、 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 des

20、cribed and results presented to illustrate how it is leading to a better understanding of both the mechanics of progressive colla</p><p>　　2.Design to resist progressive collapse</p><p>　　The tw

21、o most frequently used design approaches intended to address the issue of progressive collapse are:</p><p>　　*Providing tying capacity </p><p>　　*Checking alternate load paths</p><

22、p>　　Figure 1: Tie Forces in a Frame Structure</p><p>　　The first is essentially prescriptive and consists of ensuring that beams, columns, connections and floor (or roof) can act together to provide a spe

23、cified 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 a

24、pproach is simple to appreciate, requires minimal structural calculation and, in situations where the original provisions are found</p><p>　　In its most frequently used form the alternative load path approac

25、h presumes the instantaneous loss of a single column and then requires that the ability of the resulting damaged structure to bridge the loss be demonstrated by suitable calculation (Gudmundsson and Izzuddin 2010). The a

26、pproach 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 </p

27、><p>　　3. Essential features of progressive collapse</p><p>　　Three features have previously (Nethercot 2010) being identified as essential components of any reasonably realistic approach to design

28、 against progressive collapse:</p><p>　　*Events take place over a very short timescale and the actual failure is therefore dynamic.</p><p>　　*It involves gross deformations, generating large s

29、trains, leading to inelastic behaviour as well as change of geometry effects.</p><p>　　*Failure essentially corresponds to an inability of the structure in its damaged state to adopt a new position of equil

30、ibrium without separation of key elements.</p><p>　　Figure 2: Simplified multi-level approach for progressive collapse assessment</p><p>　　Additional features, designed to make the approach attr

31、active for use by practicing Engineers have also been proposed (Nethercot 2010):</p><p>　　*Process should consist of a series of steps broadly similar in concept to those used for “conventional” structural

32、design.</p><p>　　*It should, preferably, be capable of implementation at a variety at levels of complexity–with the choice reflecting the importance of the structure.</p><p>　　*Any required an

33、alysis should utilise familiar techniques; where these require computations beyond “hand methods”, these should be based on the use of available analysis software.</p><p>　　*A realistic and recognisable cri

34、terion of failure should be used.</p><p>　　*Approach should permit study of cause and effect and be suitable for the making of quantitative comparisons.</p><p>　　It was against this background

35、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 subseque

36、ntly been refined (Stylianidis 2010). Although the starting point was column removal, the approach contains a number of distinctive features:</p><p>　　*Although dynamic response is allowed for, only static

37、 analysis is required (Izzuddin et al 2007).</p><p>　　*The approach may be implemented at structure, sub-structure, floor grillage or individual beam level, see Figure 2.</p><p>　　*A realistic

38、 criterion of failure is employed, corresponding to reaching the ductility limits in connections.</p><p>　　*Quantitative comparisons between alternative structural arrangements may readily be made.</p>

39、;<p>　　*The approach may be implemented using only explicit formulae, thereby permitting simple and rapid calculation.</p><p>　　Full details of the method, both in its original form which utilises AD

40、APTIC to perform the calculations and in its simplified form, may be found in the series of Imperial papers (2-12).</p><p>　　*a)First yielding of the tensile components (top bolt row of the support connecti

41、on)</p><p>　　*b)Ultimate capacity of the beam flange at one of the connections (support)</p><p>　　*c)Ultimate capacity of the system (failure of the bottom bolt row of the mid-span connection)

42、</p><p>　　*d)The axial load becomes zero (the deflection of the beam where the axial load changes from compressive to tensile)</p><p>　　*e)The deflection of the beam where the axial load becom

43、es equal to the flange capacity of one of the connections (mid-span connection)</p><p>　　Figure 3: Non-linear static response for a single beam</p><p><b>　　中文翻譯2</b></p><p

44、>　　通過建筑結構設計以改善建筑物的抗倒性</p><p>　　D A Nethercota </p><p>　　土木與環(huán)境工程學院——倫敦帝國學院</p><p>　　摘 要：如今的“新話題”出現(xiàn)在相對成熟的結構工程領域這是一件罕見的事。抗連續(xù)倒塌，或者，更特別的是，了解力學的現(xiàn)象和發(fā)展適當?shù)姆绞剑赃m應我們正常的框架內審議的結構設計，可以這么認為。

45、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計方法進行了綜述。最近的工作是當時的報道，集中精力在過去7年在倫敦大學帝國學院的發(fā)展，在一個能使用各種水平和由設計師一直在發(fā)展適合直接使用的綜合方法。說明性的結果是用來幫助發(fā)現(xiàn)一些關鍵的管理功能，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計概念之間的不同來直接改善抗倒性。</p><p

46、>　　關鍵詞：復合結構，漸進式折疊，魯棒性，鋼鐵結構，結構設計</p><p><b>　　1.引言</b></p><p>　　隨著時間的推移各種不同的結構設計原理被提出,他們發(fā)展的自然回想：</p><p>　　*越來越關注確保足夠的性能。</p><p>　　*改進過的性能的科學知識。</p>

47、<p>　　*加強能力從工藝為基礎的移動科學依據(jù)從而從規(guī)范的定量合理的方法。</p><p>　　這可以通過追蹤的概念,如:容許應力，強度極限，極限狀態(tài)和基礎性能。作為客戶：用戶和公眾已經(jīng)變得越來越復雜,因此要求更高的期望，因此，它成為必要的設計師代替一個永久的越來越多的結構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,基本上復制

48、過去的令人滿意的性能,方式）開始需要顯式的形式的關注：需求評估，模型行為和識別合適的失效準則。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。</p><p>　　舉一個具體的例子：設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)則對混凝土外層脆弱的構件。但是,近年來,發(fā)展成為一個復雜的消防工程學科，關心火災荷載，提供防護系統(tǒng),如灑水裝置，在發(fā)生火災情況下的反應的計算,能夠使定量對比結構

49、安排之間選擇。不僅導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；它也導致了消防安全通道更好的調節(jié)原則的理解和明智的行事能力在設計適合安排一個合適的評估基礎上的需要。</p><p>　　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層預制混凝土公寓建筑導致了新的英國建筑法規(guī)誕生。取締了多年來所謂

50、的系統(tǒng)構建方案，拆除了幾個完整的建筑物，排除高層建筑物里的臨時瓦斯和建立建構安全方面的常務委員會。最終，合理設計的預處理的好處是公認的，安全的方法來安裝燃氣設計然后開始進入工業(yè)。然后，結構設計指導在當時產(chǎn)生——仍然決定了很多現(xiàn)在的條款——是自然本質上的處方式,沒有真正的鏈接到實際的性能。</p><p>　　后來，連續(xù)倒塌的發(fā)生率如同Murragh Building和世貿中心帶來增加如何合理地考慮那些結構的設計實

51、際現(xiàn)象和問題的關注，它被認為是合適的。在這樣做,當然,至關重要的風險,包括一個觸發(fā)事件和失敗的結果,所以更繁重的結構要求被適當?shù)厥褂??？梢哉f，一個不成比例的反應在風險/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險/后果是高/嚴重的地方一樣有害。</p><p>　　本文將回顧當前用來設計抵制連續(xù)倒塌的方法和對比過去七年在倫敦大學帝國理工學院進行的這些工作，那里的目標是提供一個依

52、據(jù)于實際方法適合用在常規(guī)設計。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果來說明它是如何導致更好的連續(xù)倒塌的機制的原理和結構工程師的方式能最好的配置結構,以提供增強的抗性。</p><p>　　2.設計抵抗連續(xù)倒塌</p><p>　　兩種最常用設計方法旨在解決連續(xù)倒塌這一問題：</p><p><b>　　*提供綁扎能力</b>&

53、lt;/p><p>　　*檢查交替的荷載通道</p><p>　　圖1:領帶部隊在一個框架結構</p><p>　　首先，本質上的規(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的。圖1，這個來自最近的US Guidance，演示了原理。這個方法對于觀察是簡單的，只需要很少的結構計算和在最初

54、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，認識到鏈式反應的連接的生成，US Guidance已經(jīng)限制可以展示相關的連接可以攜帶所需的彈性元件同時進行0.2光輝的旋轉的情況的結構構件之間的綁扎的使用。這是不可能的，連系材料應該通過樓板和屋蓋。無論如何，近代研究（Nethercot et al 2010a; Nethercot et al 2010b）都建議綁扎力相關較弱和實

55、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——結構設計的一個基本特征。</p><p>　　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，然后需要這作為結果的被損傷的構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

56、析制定規(guī)定和為各自的使用提供一些指導。它也可以被使用作為基點為特定結構或特定工作（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?？量痰摹呀?jīng)證明了他們的能力去緊密地復制的真實的可觀察的特性。</p><p>　　3.抗連續(xù)倒塌的基本特性</p><p>　　三個特征已經(jīng)預先被鑒證出作為任何合理的現(xiàn)實的方法去設計對抗連續(xù)倒塌的必要部分：</p><p>

57、　　*事件發(fā)生在非常短的時間段內和正在的失敗是因此動態(tài)。</p><p>　　*它包括總變形，發(fā)生大應變，導致非彈性行為和幾何效果的改變一樣。</p><p>　　*失敗基本上對應于在受損狀態(tài)下構件的無能通過一個新的沒有關鍵元素的分離的平衡位置</p><p>　　圖2:簡化的多層次評估方法抗連續(xù)倒塌</p><p>　　附加裝置也有人

58、提出，為了讓這種方法被工程師使用。</p><p>　　*程序應該由一序列的在概念中廣泛相似于那些用于“傳統(tǒng)”的結構設計的步驟構成</p><p>　　*從實際出發(fā)，合理的，能夠實現(xiàn)在一個復雜水平上的一個品種——伴隨選擇反映結構的重要性。</p><p>　　*任何必需的驗定都應該利用熟悉的技術；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。&

59、lt;/p><p>　　*一個現(xiàn)實的知名的破壞的準則應該被使用。</p><p>　　*方法應該允許原因和結果研究和適用于定量判斷的制定。</p><p>　　正是在這樣的背景之下,倫敦帝國學院的研究正在進行。一個結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

60、柱移動，但該方法包含一些獨特的特性：</p><p>　　*雖然動態(tài)反應是被允許的，但是只有靜態(tài)分析是必需的（Izzuddin et al 2007）。</p><p>　　*該方法可以實現(xiàn)在結構，亞結構，地板格柵或單梁的標準（見圖2）.</p><p>　　*一個現(xiàn)實的破壞標準被采用，對應于在連接中到達延性限制。</p><p>　　

61、*定量對比替代結構安排可能容易就能做出。</p><p>　　*該方法可以實現(xiàn)只使用顯式公式，從而允許簡單和快速計算。</p><p>　　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，應該都能在帝國文件中被找到（2-12）。</p><p>　　圖3：單梁的非線性靜力反應</p><p>　　*a)首

62、先拉力組件的產(chǎn)生（支撐連接的頂級螺栓排）</p><p>　　*b)其中的一個連接（支撐）的光束翼緣的總功率</p><p>　　*c)系統(tǒng)的總功率（底部中跨連接的螺栓行的破壞）</p><p>　　*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）</p><p>　　*e)一個連接的翼緣力在軸向荷載變相等的地方的梁

63、的撓度</p><p><b>　　參考文獻</b></p><p>　　[1] Gudmundsson GV and Izzuddin BA. The Sudden Column Loss Idealisation for Disproportionate Collapse Assessment. The Structural Engineer; 2010. 88

64、 pp. 22-26. </p><p>　　[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. 16

65、0. No. SB4 pp. 197-206. </p><p>　　[3] Izzuddin BA, Vlassis AG, Elghazouli AY, and Nethercot DA. Progressive Collapse of Multi-Storey Buildings due to Sudden Column Loss - Part I Simplified Assessment Fr

66、amework, Engineering Structures; 2008, Vol. 30, No. 5, pp. 1308-1318. </p><p>　　[4] Izzuddin BA, Vlassis AG, Elghazouli AY, and Nethercot DA. Progressive Collapse of Multi-Storey Buildings due to Sudden

67、Column Loss - Part II, Applications Engineering Structures; 2008, Vol. 30, No. 5 pp. 1424 – 1438. </p><p>　　[5] Nethercot DA. Utilising Strength, Stiffeners and Ductility in Enhancing the Robustness of

68、Steel Composite Frame Structures , in Congresso de Construcao Metalica e Mistro, ed L da Silva el, Lisbon; 2009, pp. 1-3 -1-19. </p><p>　　[6] Nethercot DA. Progressive Collapse Analysis of Steel and Compo

69、site Frame Structures. AIAS Maratea; 2010, 7 – 10 Sept, pp. 5-15. </p><p>　　[7] Nethercot DA, Stylianidis P, Izzuddin BA, and Elghazouli AY. Enhancing the Robustness of Steel and Composite Buildings, ICAS

70、S’09 Hong Kong; 2009, pp. 105-122. </p><p>　　[8] Nethercot DA, Stylianidis P, Izzuddin BA, and Elghazouli AY. Resisting Progressive Collapse by the Use of Tying Resistance, 4th International Conference on

71、Steel & Composite Structures Sydney Australia; 2010a </p><p>　　[9] Nethercot DA, Blundell D, and Stylianidis P. Progressive Collapse Behaviour of Bare Steel Frames, Ivanyi Conference; 2010b </p&g

72、t;<p>　　[10] SEI Disproportionate Collapse Standards and Guidance Committee. Design Procedures, Draft Committee Document; 2010 [11] Stylianidis PM, PhD Thesis, Department of Civil and Environmental Engineering,

73、 Imperial College London, in Preparation; 2010 </p><p>　　[12] Vlassis AG. Progressive Collapse Assessment of Tall Buildings; PhD Thesis, Department of Civil and Environmental Engineering, Imperial College