土木工程外文翻譯---建筑防火設(shè)計(jì)（原文）

1、EJSE Special Issue: Loading on Structures (2007) 1 INTRODUCTION Other papers presented in this series consider the design of buildings for gravity loads, wind and earthquakes. The design of buildings against such load

2、 effects is to a large extent covered by engineer- ing based standards referenced by the building regu- lations. This is not the case, to nearly the same ex- tent, in the case of fire. Rather, it is building regulations

3、 such as the Building Code of Australia (BCA) that directly specify most of the require- ments for fire safety of buildings with reference be- ing made to Standards such as AS3600 or AS4100 for methods for determining

4、 the fire resistance of structural elements. The purpose of this paper is to consider the de- sign of buildings for fire safety from an engineering perspective (as is currently done for other loads such as wind or ea

5、rthquakes), whilst at the same time, putting such approaches in the context of the current regulatory requirements. At the outset, it needs to be noted that designing a building for fire safety is far more than simpl

6、y considering the build- ing structure and whether it has sufficient structural adequacy. This is because fires can have a direct in- fluence on occupants via smoke and heat and can grow in size and severity unlike othe

7、r effects im- posed on the building. Notwithstanding these com- ments, the focus of this paper will be largely on de- sign issues associated with the building structure. Two situations associated with a building are us

8、ed 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 a wide range of rail traffic utili

9、ses these tracks including freight and diesel lo- comotives. The first situation to be considered from a fire safety perspective is the transfer structure. This is termed Situation 1 and the key questions are: what le

10、vel of fire resistance is required for this transfer structure and how can this be determined? This situation has been chosen since it clearly falls outside the normal regulatory scope of most build- ing regulations.

11、An engineering solution, rather than a prescriptive one is required. The second fire situa- tion (termed Situation 2) corresponds to a fire Designing Against Fire I. D. Bennetts Noel Arnold and Associates, Melbourne A

12、ustralia I. R. Thomas CESARE, Victoria University, Australia ABSTRACT: This paper considers the design of buildings for fire safety. It is found that fire and the associ- ated effects on buildings is significantly diff

13、erent 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 within buildings or from the ma

14、lfunction of mechanical and electrical equipment provided within buildings to achieve a serviceable environment. It is therefore possible to directly influence the rate of fire starts within buildings by changing human

15、 behaviour, improved maintenance and improved design of me- chanical and electrical systems. Furthermore, should a fire develops, it is possible to directly influence the re- sulting fire severity by the incorporation of

16、 fire safety systems such as sprinklers and to provide measures within the building to enable safer egress from the building. The ability to influence the rate of fire starts and the resulting fire severity is unique t

17、o the consideration of fire within buildings since other loads such as wind and earthquakes are directly a function of nature. The possible approaches for designing a building for fire safety are presented using an exa

18、mple of a multi-storey building constructed over a railway line. The design of both the transfer structure supporting the building over the railway and the levels above the transfer struc- ture are considered in the con

19、text of current regulatory requirements. The principles and assumptions associ- ated with various approaches are discussed. 9EJSE Special Issue: Loading on Structures (2007) tem may assist in the development of other lo

20、ad re- sisting mechanisms (see Section 4.3.5). 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

21、ngth. Such effects are not instanta- neous 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. Heating effects associated with a fi

22、re will not be significant or the rate of loss of capacity will be slowed if: (a) the fire is extinguished (e.g. an effective sprin- kler system) (b) the fire is of insufficient severity – insufficient fuel, and/or (c

23、) the structural elements have sufficient thermal mass and/or insulation to slow the rise in inter- nal temperature Fire protection measures such as providing suffi- cient axis distance and dimensions for concrete elem

24、ents, and sufficient insulation thickness for steel elements are examples of (c). These are illus- trated in Figure 2. The two situations described in the introduction are now considered. 3 FIRES DUE TO TRAINS BELOW BU

25、ILDING 3.1 Possible Approaches What level of fire resistance is required for the transfer structure shown in Figure 1? One approach to answering this question could be to design the transfer structure to resist the

26、most se- vere possible fire until that fire has burnt out. How- ever, if the trains traveling below the building in- clude a range of diesel locomotives and freight cars, it may not be economically feasible to design a

27、gainst the worst possible fire. Another more rational approach would be to design the transfer structural elements against fire such that the probability of failure of the members in the event of fire (many different

28、fires with different probabilities of occurrence) is no greater than that associated with the normal temperature loading conditions. In this approach account must be taken of: (a) the variability associated with lo

29、ads applied to the building, (b) the possible fire train scenarios as characterised by their probability and heating characteristics, and (c) the effect of such fires on the resistance of the transfer members Th

30、is approach is now further described. As the re- sistance of the structural members is reduced, the probability of structural failure is increased. For a particular fire event i, this probability may be de- noted as f

31、fi pgiven the variability associated with the loading and resistance. If the fire events are con- sidered to be independent and the probability of oc- currence of fire event i is denoted as i p , then the overall probabi

32、lity of failure for a given structural element when subject to all possible fire events is: ∑ × =i ffi i tf p p p[1] It can be argued that the fire design is satisfactory if this probability is less than some acce

33、ptably small value acc p – for example, the value adopted for normal temperature design. It is generally accepted that the notional probability of failure of a key structural member subject to gravity loads and de- s

34、igned in accordance with Australian structural and loading standards is about 2 x10-4 over the life of the building. The adoption of such a value would be appropriate on the basis that it is difficult to see why the

35、structure should be safer in fire than under nor- mal temperature conditions. Figure 2 Concrete and Steel Elements determine fire temperature versus timedetermine tempswithin memberdetermine member strengthdetermine c