建筑防火設(shè)計(jì)外文翻譯

1、<p><b>　　廣西工學(xué)院鹿山學(xué)院</b></p><p>　　畢業(yè)設(shè)計(jì)（論文）外文翻譯</p><p>　　題 目： 結(jié)構(gòu)特性分析</p><p>　　系 別： 土木工程系 </p><p>　　專業(yè)班級： 土木L084 </p&

2、gt;<p>　　姓 名： 王一帆 </p><p>　　學(xué) 號： 20081617 </p><p>　　指導(dǎo)教師： 琚宏昌 </p><p>　　二〇一二年二月二十四日</p><p>　　Designing Against Fi

3、re Of Buliding</p><p>　　John Lynch </p><p>　　ABSTRACT: </p><p>　　This paper considers the design of buildings for fire safety. It is found that fire and the associ- ated effects o

4、n buildings is significantly different to other forms of loading such as gravity live loads, wind and earthquakes and their respective effects on the building structure. Fire events are derived from the human activities

5、within buildings or from the malfunction of mechanical and electrical equipment provided within buildings to achieve a serviceable environment. It is therefore possib</p><p><b>　　外文文獻(xiàn)：　</b></p

6、><p>　　Designing Against Fire Of Buliding</p><p>　　John Lynch </p><p>　　ABSTRACT: </p><p>　　This paper considers the design of buildings for fire safety. It is found tha

7、t fire and the associ- ated effects on buildings is significantly different to other forms of loading such as gravity live loads, wind and earthquakes and their respective effects on the building structure. Fire events a

8、re derived from the human activities within buildings or from the malfunction of mechanical and electrical equipment provided within buildings to achieve a serviceable environment. It is therefore possib</p><p

9、>　　1 INTRODUCTION</p><p>　　Other papers presented in this series consider the design of buildings for gravity loads, wind and earthquakes.The design of buildings against such load effects is to a larg

10、e extent covered by engineering based standards referenced by the building regulations. This is not the case, to nearly the same extent, in the case of fire. Rather, it is building regulations such as the Building Code o

11、f Australia (BCA) that directly specify most of the requirements for fire safety of buildings with refer</p><p>　　The purpose of this paper is to consider the design of buildings for fire safety from an engi

12、neering perspective (as is currently done for other loads such as wind or earthquakes), whilst at the same time,putting such approaches in the context of the current regulatory requirements.At the outset,it needs to be

13、 noted that designing a building for fire safety is far more than simply considering the building structure and whether it has sufficient structural adequacy.This is because fires can hav</p><p>　　Two situat

14、ions associated with a building are used for the purpose of discussion. The multi-storey office building shown in Figure 1 is supported by a transfer structure that spans over a set of railway tracks. It is assumed that

15、 a wide range of rail traffic utilises these tracks including freight and diesel locomotives. The first situation to be considered from a fire safety perspective is the transfer structure.This is termed Situation 1 and

16、the key questions are: what level of fire resistan</p><p>　　2 UNIQUENESS OF FIRE</p><p>　　2.1 Introduction</p><p>　　Wind and earthquakes can be considered to be “natural” phenom

17、ena over which designers have no control except perhaps to choose the location of buildings more carefully on the basis of historical records and to design building to resist sufficiently high loads or accelerations fo

18、r the particular location. Dead and live loads in buildings are the result of gravity. All of these loads are variable and it is possible (although generally unlikely) that the loads may exceed the resistance of the c&

19、lt;/p><p>　　The nature and influence of fires in buildings are quite different to those associated with other“l(fā)oads” to which a building may be subjected to. The essential differences are described in the foll

20、owing sections.</p><p>　　2.2 Origin of Fire</p><p>　　In most situations (ignoring bush fires), fire originates from human activities within the building or the malfunction of equipment placed

21、 within the building to provide a serviceable environment. It follows therefore that it is possible to influence the rate of fire starts by influencing human behaviour, limiting and monitoring human behaviour and improv

22、ing the design of equipment and its maintenance. This is not the case for the usual loads applied to a building.</p><p>　　2.3 Ability to Influence</p><p>　　Since wind and earthquake are direct

23、ly functions of nature, it is not possible to influence such events to any extent. One has to anticipate them and design accordingly. It may be possible to influence the level of live load in a building by conducting aud

24、its and placing restrictions on contents. However, in the case of a fire start, there are many factors that can be brought to bear to influence the ultimate size of the fire and its effect within the building. It is kno

25、wn that occupants with</p><p>　　Fire fighting equipment, such as extinguishers and hose reels, is generally provided within buildings for the use of occupants and many organisations provide training for st

26、aff in respect of the use of such equipment.</p><p>　　The growth of a fire can also be limited by automatic extinguishing systems such as sprinklers, which can be designed to have high levels of effectiven

27、ess.Fires can also be limited by the fire brigade depending on the size and location of the fire at the time of arrival.</p><p>　　2.4 Effects of Fire</p><p>　　The structural elements in the

28、 vicinity of the fire will experience the effects of heat. The temperatures within the structural elements will increase with time of exposure to the fire, the rate of temperature rise being dictated by the thermal re

29、sistance of the structural element and the severity of the fire. The increase in temperatures within a member will result in both thermal expansion and,eventually,a reduction in the structural resistance of the member.

30、 Differential thermal expansi</p><p>　　With the exception of the development of forces due to restraint of thermal expansion, fire does not impose loads on the structure but rather reduces stiffness and stre

31、ngth. Such effects are not instantaneous but are a function of time and this is different to the effects of loads such as earthquake and wind that are more or less instantaneous.</p><p>　　Heating effects ass

32、ociated with a fire will not be significant or the rate of loss of capacity will be slowed if:</p><p>　　(a) the fire is extinguished (e.g. an effective sprinkler system)</p><p>　　(b) the fire i

33、s of insufficient severity – insufficient fuel, and/or</p><p>　　(c)the structural elements have sufficient thermal mass and/or insulation to slow the rise in internal temperature</p><p>　　Fire p

34、rotection measures such as providing sufficient axis distance and dimensions for concrete elements, and sufficient insulation thickness for steel elements are examples of (c). These are illustrated in Figure 2. </p>

35、;<p>　　The two situations described in the introduction are now considered.</p><p>　　3 FIRE WITHIN BUILDINGS</p><p>　　3.1 Fire Safety Considerations</p><p>　　The implicat

36、ions of fire within the occupied parts of the office building (Figure 1) (Situation 2) are now considered. Fire statistics for office buildings show that about one fatality is expected in an office building for every 10

37、00 fires reported to the fire brigade. This is an order of magnitude less than the fatality rate associated with apartment buildings. More than two thirds of fires occur during occupied hours and this is due to the great

38、er human activity and the greater use of service</p><p>　　A relatively small fire can generate large quantities of smoke within the floor of fire origin. If the floor is of open-plan construction with few pa

39、rtitions, the presence of a fire during normal occupied hours is almost certain to be detected through the observation of smoke on the floor. The presence of full height partitions across the floor will slow the spread o

40、f smoke and possibly also the speed at which the occupants detect the fire. Any measures aimed at improving housekeeping, fir</p><p>　　For multi-storey buildings, smoke detection systems and alarms are

41、 often provided to give “automatic” detection and warning to the occupants. An alarm signal is also transmitted to the fire brigade.</p><p>　　Should the fire not be able to be controlled by the occupants on

42、 the fire floor, they will need to leave the floor of fire origin via the stairs. Stair enclosures may be designed to be fire-resistant but this may not be sufficient to keep the smoke out of the stairs. Many buildi

43、ngs incorporate stair pressurisation systems whereby positive airflow is introduced into the stairs upon detection of smoke within the building. However, this increases the forces required to open the stair do<

44、/p><p>　　From a fire perspective, it is common to consider that a building consists of enclosures formed by the presence of walls and floors.An enclosure that has sufficiently fire-resistant boundaries (i.e. wa

45、lls and floors) is considered to constitute a fire compartment and to be capable of limiting the spread of fire to an adjacent compartment. However, the ability of such boundaries to restrict the spread of fire can be se

46、verely limited by the need to provide natural lighting (windows)and access ope</p><p>　　By far the most effective measure in limiting fire spread, other than the presence of occupants, is an effective sprin

47、kler system that delivers water to a growing fire rapidly reducing the heat being generated and virtually extinguishing it.</p><p>　　3.2 Estimating Fire Severity</p><p>　　In the absence of mea

48、sures to extinguish developing fires, or should such systems fail; severe fires can develop within buildings.</p><p>　　In fire engineering literature, the term “fire load” refers to the quantity of combusti

49、bles within an enclosure and not the loads (forces) applied to the structure during a fire. Similarly, fire load density refers to the quantity of fuel per unit area. It is normally expressed in terms of MJ/m2 or kg/m2

50、of wood equivalent. Surveys of combustibles for various occupancies (i.e offices, retail, hospitals, warehouses, etc)have been undertaken and a good summary of the available data is given in FC</p><p>　　The

51、rate at which heat is released within an enclosure is termed the heat release rate (HRR) and normally expressed in megawatts (MW). The application of sufficient heat to a combustible material results in the generation of

52、 gases some of which are combustible. This process is called pyrolisation.</p><p>　　Upon coming into contact with sufficient oxygen these gases ignite generating heat. The rate of burning(and therefore of he

53、at generation) is therefore dependent on the flow of air to the gases generated by the pyrolising fuel.This flow is influenced by the shape of the enclosure (aspect ratio), and the position and size of any potential open

54、ings. It is found from experiments with single openings in approximately cubic enclosures that the rate of burning is directly proportional to A h where A is</p><p>　　The use of the word ‘opening’ in relatio

55、n to real building enclosures refers to any openings present around the walls including doors that are left open and any windows containing non fire-resistant glass.It is presumed that such glass breaks in the event o

56、f development of a significant fire. If the windows could be prevented from breaking and other sources of air to the enclosure limited, then the fire would be prevented from becoming a severe fire.</p><p>

57、　　Various methods have been developed for determining the potential severity of a fire within an enclosure.These are described in SFPE (2004). The predictions of these methods are variable and are mostly based on estim

58、ating a representative heat release rate (HRR) and the proportion of total fuel ? likely to be consumed during the primary burning stage (Figure 4). Further studies of enclosure fires are required to assist with the dev

59、elopment of improved models, as the behaviour is very complex.</p><p>　　3.3 Role of the Building Structure</p><p>　　If the design objectives are to provide an adequate level of safety for the

60、occupants and protection of adjacent properties from damage, then the structural adequacy of the building in fire need only be sufficient to allow the occupants to exit the building and for the building to ultimately de

61、form in a way that does not lead to damage or fire spread to a building located on an adjacent site.These objectives are those associated with most building regulations including the Building Code of Aus</p><

62、p>　　3.3.1 Non-Structural Consequences</p><p>　　Since fire can produce smoke and flame, it is important to ask whether these outcomes will threaten life safety within other parts of the building before th

63、e building is compromised by a loss of structural adequacy? Is search and rescue by the fire brigade not feasible given the likely extent of smoke? Will the loss of use of the building due to a severe fire result in majo

64、r property and income loss? If the answer to these questions is in the affirmative, then it may be necessary to minimise the</p><p>　　3.3.2 Other Fire Safety Systems</p><p>　　The presence of ot

65、her systems (e.g. sprinklers) within the building to minimise the occurrence of a serious fire can greatly reduce the need for the structural elements to have high levels of fire resistance. In this regard, the uncertain

66、ties of all fire-safety systems need to be considered. Irrespective of whether the fire safety system is the sprinkler system, stair pressurisation, compartmentation or the system giving the structure a fire-resistance l

67、evel (e.g. concrete cover), there is an un</p><p>　　3.3.3 Height of Building</p><p>　　It takes longer for a tall building to be evacuated than a short building and therefore the structure of a

68、 tall building may need to have a higher level of fire resistance. The implications of collapse of tall buildings on adjacent properties are also greater than for buildings of only several storeys.</p><p>　　

69、3.3.4 Limited Extent of Burning</p><p>　　If the likely extent of burning is small in comparison with the plan area of the building, then the fire cannot have a significant impact on the overall stability o

70、f the building structure. Examples of situations where this is the case are open-deck carparks and very large area building such as shopping complexes where the fire-effected part is likely to be small in relation to ar

71、ea of the building floor plan.</p><p>　　3.3.5 Behaviour of Floor Elements</p><p>　　The effect of real fires on composite and concrete floors continues to be a subject of much research.Experim

72、ental testing at Cardington demonstrated that when parts of a composite floor are subject to heating, large displacement behaviour can develop that greatly assists the load carrying capacity of the floor beyond that whic

73、h would predicted by considering only the behaviour of the beams and slabs in isolation.These situations have been analysed by both yield line methods that take into acco</p><p><b>　　中文譯文：</b>&l

74、t;/p><p><b>　　建筑防火設(shè)計(jì)</b></p><p><b>　　拉格夫</b></p><p>　　摘要：這篇論文主要研究建筑的防火設(shè)計(jì)，火作用于建筑與重力荷載,風(fēng)荷載,地震力等作用于建筑物結(jié)構(gòu)上有很大不同?；鹗怯扇祟惢顒踊蛘邫C(jī)械故障，建筑物內(nèi)的電器引起的</p><p><b&g

75、t;　　1.介紹</b></p><p>　　其他論文，考慮建筑物的設(shè)計(jì)的重力荷載，風(fēng)和地震等一系列問題。建筑物針對這些負(fù)載的影響的設(shè)計(jì)是相當(dāng)大的程度上涵蓋了工程的標(biāo)準(zhǔn)參照了建筑法規(guī)。幾乎在同一程度上，萬一發(fā)生火災(zāi)，事實(shí)并非如此。相反，正是如澳大利亞建筑法那樣的法規(guī)明確了建筑防火安全的標(biāo)準(zhǔn)，如用as3600,as4100的方法確定耐火構(gòu)件。</p><p>　　本文的目的就是要

76、從工程角度考慮建筑設(shè)計(jì)消防安全，（如目前所做的風(fēng)力或地震等其他荷載），同時(shí)將這種方法應(yīng)用于當(dāng)前規(guī)范要求的環(huán)境之中。首先需要指出的是，設(shè)計(jì)一幢防火大樓只考慮建設(shè)結(jié)構(gòu)或者是否有足夠的結(jié)構(gòu)性是遠(yuǎn)遠(yuǎn)不夠的。這是因?yàn)榛鹂梢灾苯油ㄟ^煙霧和熱量影響住戶，還可以蔓延增加嚴(yán)重性，而其它對樓房的影響不具備這一特征。 盡管有這些評論，本文的大部分重點(diǎn)仍將集中于建筑結(jié)構(gòu)的設(shè)計(jì)問題。</p><p>　　本文將選擇一棟大樓的兩種情況作為討

77、論的對象。圖1所示的多層辦公樓利用了轉(zhuǎn)換結(jié)構(gòu)，跨過了一條鐵路路軌。這是在假定了廣泛的軌道交通利用這些軌道基礎(chǔ)上，考慮到了運(yùn)費(fèi)和內(nèi)燃機(jī)車。我們將從從消防安全角度考慮第一種情況，即轉(zhuǎn)換結(jié)構(gòu)。這是被稱為情況1，其中的關(guān)鍵問題是: 哪一級耐火要求用這種轉(zhuǎn)換結(jié)構(gòu)？這種轉(zhuǎn)換結(jié)構(gòu)又如何確定？這種情況已經(jīng)選定，因?yàn)樗@然不屬于大多數(shù)建筑法規(guī)的正常的監(jiān)管范圍。我們需要的是一項(xiàng)工程性的而不是指令性的解決辦法。第二種火災(zāi)形勢（稱為情況2）相應(yīng)的消防局內(nèi)不同層

78、次的建設(shè)和涵蓋了建筑法規(guī)。選擇這種情況是因?yàn)樗鼘⒋俪晒こ虒W(xué)方法的討論以及如何把這些建設(shè)規(guī)章相銜接,因?yàn)閮煞N工程和指令性的辦法皆是可行的。</p><p><b>　　2.火災(zāi)的獨(dú)特性</b></p><p><b>　　2.1介紹</b></p><p>　　設(shè)計(jì)師無法控制風(fēng)和地震等"自然"的現(xiàn)象，因而

79、只能根據(jù)歷史記載更合理的選擇建筑物的位置，或者提高建筑的負(fù)荷能力。 建筑物的荷載由重力產(chǎn)生。 所有這些載荷是可變的，而且有可能突破阻力中的關(guān)鍵構(gòu)件，造成結(jié)構(gòu)性破壞（盡管不常見）。</p><p>　　火災(zāi)的性質(zhì)及其對建筑物影響與其他荷載有很大的不同。關(guān)鍵的的不同將在以下章節(jié)加以描述。</p><p><b>　　2.2火災(zāi)根源</b></p><p

80、>　　在大多數(shù)情況下（叢林大火排除在外），火災(zāi)源于人們在建筑內(nèi)的活動或置于建筑中的設(shè)備故障?？梢酝ㄟ^影響人類活動來影響火災(zāi)發(fā)生頻率，如限制和監(jiān)測人類行為和改進(jìn)設(shè)備的設(shè)計(jì)及維護(hù)保養(yǎng)。對于正常荷載而言則不可以這樣做。</p><p><b>　　2.3影響能力</b></p><p>　　由于風(fēng)與地震是自然界的直接功能，人類不可能對其活動產(chǎn)生任何程度的影響。人們只能

81、預(yù)測并據(jù)此設(shè)計(jì)?？梢酝ㄟ^審計(jì)和限制容積的方法來影響建筑物的活荷載。然而在火災(zāi)發(fā)生之初，可以通過影響其他一些因素來影響火災(zāi)的最終規(guī)模及其對建筑的影響程度。建筑物中的住戶會經(jīng)常發(fā)現(xiàn)火苗并在其蔓延之前將其撲滅。據(jù)估計(jì)，只有不到五分之一的火災(zāi)需要報(bào)警，大多數(shù)的火災(zāi)都在起火的房間中得到了控制。在填滿東西的空間里，嗅覺線索(臭味)可以為火災(zāi)的發(fā)生提供強(qiáng)有力的證據(jù)。煙霧偵測系統(tǒng)的安裝，將進(jìn)一步提高的檢測到火災(zāi)的可能性，住戶可以在第一時(shí)間采取行動。&l

82、t;/p><p>　　滅火器材，如滅火器，滅火喉轆，通常是在建筑物中供使用，也有不少機(jī)構(gòu)人員提供如何使用防火器材方面的培訓(xùn)。 </p><p>　　火災(zāi)的蔓延受自動滅火系統(tǒng)的影響，如自動灑水可設(shè)計(jì)成具有高效益?；馂?zāi)也可由消防隊(duì)員來控制，這要是火災(zāi)的規(guī)模、發(fā)生地點(diǎn)及消防隊(duì)員的到達(dá)時(shí)間而定。 </p><p><b>　　2.4火災(zāi)的影響</b><

83、;/p><p>　　火災(zāi)的熱效應(yīng)存在于火災(zāi)的周圍，這將對周邊建筑產(chǎn)的構(gòu)成材料產(chǎn)生影響。建筑材料的溫度會隨著暴露于火災(zāi)時(shí)間的增長而升溫，溫度的升高程度取決于隔熱材料和火勢。溫度的升高會導(dǎo)致材料的熱膨脹，并最終導(dǎo)致整個(gè)結(jié)構(gòu)的破壞。不同程度的熱膨脹會導(dǎo)致材料彎曲變形。重大軸向擴(kuò)張將被安置在鋼構(gòu)件,不論是整體或局部屈曲或屈服的局部地區(qū)。這些效應(yīng)將會對支柱產(chǎn)生破壞性影響，但組成樓面的橫梁可以協(xié)助產(chǎn)生其他負(fù)荷抵御機(jī)制（見4.3.

84、5節(jié)）。</p><p>　　除了由于火災(zāi)發(fā)身而產(chǎn)生的阻止熱膨脹的力量外，火災(zāi)不會使建筑物的荷載增加，而是降低其硬度和剛度。這種效果不是瞬間的，而是一個(gè)時(shí)間的函數(shù),這不同于地震、風(fēng)等或多或少都具有瞬間性的荷載。</p><p>　　在以下情況中，火災(zāi)的熱效應(yīng)將不顯著或者蔓延的速度放慢：</p><p>　?。ㄒ唬┗鸨粨錅?例如一個(gè)有效的自動噴水滅火系統(tǒng)) </

85、p><p>　　（二）大火的助燃物不足</p><p>　?。ㄈ┙Y(jié)構(gòu)材料具有很好的隔熱性能，可以有效減慢內(nèi)部溫度的升高</p><p>　　情況（三）中闡述的諸如提供足夠的水平距離和水泥材料的尺寸、足夠的鋼構(gòu)件厚度等防火措施，都在圖二中加體現(xiàn)出來。</p><p>　　介紹中提到的兩種情況都已闡述完畢。</p><p>

86、<b>　　3建筑物內(nèi)的火災(zāi)</b></p><p>　　3.1消防安全因素 </p><p>　　現(xiàn)在考慮在辦公樓的使用區(qū)域發(fā)生的火災(zāi)（見圖1）（情形2）?；馂?zāi)統(tǒng)計(jì)數(shù)據(jù)顯示,大約平均向消防隊(duì)報(bào)警的每千起辦公樓火災(zāi)中死亡一人。這個(gè)死亡率低于公寓火災(zāi)的死亡率。三分之二以上的火災(zāi)發(fā)生在建筑物正在被使用的時(shí)候，這是由建筑物內(nèi)大量的人類活動及服務(wù)所致。正常工作時(shí)間之外產(chǎn)生的火

87、源蔓延到其他地方的可能性是正常工作時(shí)間內(nèi)產(chǎn)生的火源的兩倍。</p><p>　　一團(tuán)相對來說較小的或可以在火災(zāi)發(fā)生的樓層產(chǎn)生濃重的煙霧。如果樓是開放式的設(shè)計(jì)隔間比較少，則在樓房正常使用時(shí)間很容易發(fā)現(xiàn)火源產(chǎn)生的煙霧從而很容易找到火源。填滿了隔間的樓層將會延緩煙霧的擴(kuò)散，從而會推遲樓層中的人發(fā)現(xiàn)火災(zāi)的時(shí)間。提高消防意識和消防反應(yīng)，將有利于減少在被使用的時(shí)間的重大火災(zāi)的發(fā)生。</p><p>　

88、　多層建筑物中的煙霧偵測系統(tǒng)和警報(bào)器，可以提供給“自動”檢測和報(bào)警。 報(bào)警信號也傳送給消防隊(duì)。</p><p>　　當(dāng)火勢太大樓中住戶無法應(yīng)對的時(shí)候，他們必須經(jīng)樓梯離開著火的樓層。樓梯罩可以設(shè)計(jì)為防火的但這可能不足以阻止延誤進(jìn)入樓梯。許多建筑物配有樓梯加壓系統(tǒng)，系統(tǒng)可以在發(fā)現(xiàn)煙霧后將氣流引入樓道。然而，這大大增加了打開樓梯門需要的力量，使得越來越難以進(jìn)入樓梯。</p><p>　　從消防角

89、度看，人們普遍認(rèn)為樓房就是用水泥和墻隔開的小隔間。一個(gè)房間如果有防火的墻壁和地板則可以將火勢限制在房間之內(nèi)而不向相鄰房間蔓延。然而，由于房間的采光及與相鄰隔間的通道等因素的影響，這種防火房間的效用受到了限制。在火勢較大的情況下也可以通過窗戶蔓延。限制窗口大小和幾何形狀可以降低火災(zāi)蔓延的可能性，但不排除火災(zāi)縱向蔓延的情況。 </p><p>　　迄今為止限制火災(zāi)蔓延的最有效措施，除了在場的住戶救火之外，就是安裝一個(gè)

90、有效的自動噴水滅火系統(tǒng)，從而可以向正在蔓延的火災(zāi)自動噴水，以降低溫度從而撲滅大火。</p><p>　　3.2估算火災(zāi)嚴(yán)重程度</p><p>　　如果缺少救火措施或者救火機(jī)制失靈，猛烈的大火就會在樓內(nèi)蔓延。 </p><p>　　在消防工程文獻(xiàn)中，所謂“火荷載”指的是發(fā)生火災(zāi)時(shí)，房間內(nèi)的易燃物的數(shù)量，而不是指對建筑結(jié)構(gòu)的荷載。同樣，火災(zāi)荷載密度是指每單位面積燃料數(shù)

91、量。它通常用等量木材的MJ/m2 或kg/m2來表示。對各類住戶（如辦公室，零售商店，醫(yī)院，倉庫等）的可燃物調(diào)查已經(jīng)進(jìn)行過，對這些數(shù)據(jù)的總結(jié)記載在FCRC （1999）中。正如我們料到的那樣，火災(zāi)荷載密度參差不齊。如國際消防工程指引（2005）等雜志提供了消防負(fù)荷數(shù)據(jù)計(jì)算的均值和80分值。后者的火災(zāi)荷載密度水平，有時(shí)被視為典型火災(zāi)荷載密度。</p><p>　　熱釋放的速度被稱為熱釋放率（HRR），通常用兆瓦（M

92、W）表示。對可燃物施以足夠的熱量可以產(chǎn)生可燃的氣體。這一過程叫做可燃?xì)饣?</p><p>　　當(dāng)接觸到足夠的氧氣時(shí)，這些氣體燃燒產(chǎn)生熱。燃燒的速度（同時(shí)也是熱量散發(fā)的速度）取決于產(chǎn)生的可燃?xì)怏w流動的速度。這種流動是房間構(gòu)造影響（寬高比），位置和大小有潛力可挖。結(jié)果發(fā)現(xiàn)，實(shí)驗(yàn)用單開口約立方外殼率的燃燒是成正比為H那里是一個(gè)地區(qū)的開放和H是高度開放。據(jù)悉，深罩單開孔，燃燒將會出現(xiàn)最初最接近啟用移動潛回圈地一旦燃料

93、最接近開口進(jìn)食（托馬斯等，2005）。會預(yù)見到房間內(nèi)將發(fā)生顯著的溫度變化。</p><p>　　所用的字“開啟”指指墻上的任何開口，包括敞開的門或者不含防火材料的玻璃。這種玻璃可以在大火災(zāi)的蔓延中破碎。如果窗戶可以防破碎，空氣中的任何物質(zhì)都無法進(jìn)入著火房間的話，火勢就不會發(fā)展為大火災(zāi)。</p><p>　　決定火災(zāi)潛在嚴(yán)重性的各種方法都已經(jīng)建立。這些都在SFPE (2004) 中有所描述。

94、這些方法的有效性不同，而且大多基于估算一個(gè)代表性的熱釋放率（HRR），總?cè)剂系谋壤?也假設(shè)在初級燃燒階段（如圖4）。由于實(shí)際情況復(fù)雜，進(jìn)一步的研究仍需進(jìn)行以適應(yīng)不斷改進(jìn)的模型。</p><p><b>　　3.3建筑結(jié)構(gòu)</b></p><p>　　如果設(shè)計(jì)的目標(biāo)是為使用者提供足夠的安全水準(zhǔn)，同時(shí)也要保證相鄰財(cái)產(chǎn)的安全。樓房的設(shè)計(jì)必須能使人們在大火發(fā)生時(shí)及時(shí)逃離現(xiàn)場并

95、且是火災(zāi)不蔓延到周邊建筑。這些目標(biāo)是與大多數(shù)建筑法規(guī)包括澳大利亞建筑法（BCA）相一致。 還有一些避免建筑受到重大損害等的其他目標(biāo)。在考慮上述各項(xiàng)目標(biāo)的同時(shí)，涉及建筑的耐火設(shè)計(jì)時(shí)還要考慮一下因素。</p><p>　　3.3.1非結(jié)構(gòu)性后果</p><p>　　因?yàn)榛馂?zāi)產(chǎn)生煙霧和火焰，在建筑的結(jié)構(gòu)損毀之前，這些煙霧會不會危害到建筑內(nèi)其他地方的人的生命安全？是不是濃厚的煙霧以致于消防隊(duì)的搜索

96、和救援都不可行？會不會由于嚴(yán)重的火災(zāi)造成的重大財(cái)產(chǎn)和收入損失致使整個(gè)建筑無法使用？如果這些問題的答案是肯定的，那么我們應(yīng)該考慮如何避免重大火災(zāi)的發(fā)生，而不是簡單地將建筑設(shè)計(jì)為具有強(qiáng)耐火能力結(jié)構(gòu)。低層購物中心兩級互聯(lián)的大空隙就是一個(gè)例子。</p><p>　　3.3.2其它防火安全系統(tǒng)</p><p>　　建筑內(nèi)的其他防火系統(tǒng)(如灑水器)的建設(shè)，可以有效降低嚴(yán)重火災(zāi)的發(fā)生的頻率，也可以大大降

97、低將建筑設(shè)計(jì)為高層次的耐火能力必要。在這方面，要對所有的防火系統(tǒng)加以考慮。無論防火安全系統(tǒng)是自動噴水滅火系統(tǒng)，樓梯間加壓， 區(qū)隔化或是使構(gòu)架具有耐火等級（例如加蓋混凝土蓋板），都具有不確定性?？梢缘玫疥P(guān)于自動噴水系統(tǒng)的一些數(shù)據(jù)（因?yàn)檫@些數(shù)據(jù)比較容易收集），但其他防火系統(tǒng)的數(shù)據(jù)不是那么現(xiàn)成。這容易使設(shè)計(jì)師和建筑規(guī)范制定者認(rèn)為到只有灑水系統(tǒng)都受到不確定性的影響。在實(shí)際中就會發(fā)現(xiàn)，自動噴水系統(tǒng)效用突出，可以設(shè)計(jì)成具有高水準(zhǔn)的防火系統(tǒng)。<

98、/p><p>　　3.3.3建筑物高度</p><p>　　高層建筑較矮建筑來說膠南疏散人群，因此，高層建筑的結(jié)構(gòu)需要具有較高的耐火等級。高層建筑倒塌的可能性也高于只有幾層的矮建筑。</p><p>　　3.3.4燃燒的有限程度</p><p>　　如果可能燃燒的程度比預(yù)計(jì)的要輕，那么大火就不會對建筑結(jié)構(gòu)的穩(wěn)定性有顯著的影響。這樣的例子有露天停車

99、場和面積較大的建筑。</p><p><b>　　3.3.5地板材料</b></p><p>　　大火對復(fù)合或水泥地板的影響仍然是一個(gè)值得研究的話題?？ǘ☆D實(shí)驗(yàn)測試表明，當(dāng)部分復(fù)合地板受熱氣炙烤時(shí)，就會發(fā)生較大位移。這些情況已按雙方屈服線方法研究過，同時(shí)考慮到影響力膜(Bailey, 2004)和有限元技術(shù)。事實(shí)上，該方法說明，沒有必要為了達(dá)到高耐火等級的要求而研究所