ISO TR 12468-3-2014 External exposure of roofs to fire - Part 3 Commentary《屋顶外露部分的防火 第3部分 注释》.pdf

1、 ISO 2014 External exposure of roofs to fire Part 3: Commentary Exposition des toitures un feu extrieur Partie 3: Commentaire TECHNICAL REPORT ISO/TR 12468-3 First edition 2014-08-15 Reference number ISO/TR 12468-3:2014(E) ISO/TR 12468-3:2014(E)ii ISO 2014 All rights reserved COPYRIGHT PROTECTED DOC

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4、14 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 ISO 12468-1, test method 1 4 Fire scenarios . 1 5 Evaluation parameters . 5 6 ISO 124682, classification of roofs. 6 Bibliography 7 ISO/TR 12468-3:2014(E) Foreword ISO (the International Organi

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11、his document is ISO/TC 92, Fire safety, Subcommittee SC 2, Fire containment. ISO 12468 consists of the following parts, under the general title External exposure of roofs to fire: Part 1: Test method Part 2: Classification of roofs Part 3: Commentaryiv ISO 2014 All rights reserved ISO/TR 12468-3:201

12、4(E) Introduction This part of ISO 12468 describes the background used in the development and ongoing revision of ISO 12468-1:2013 and ISO 12468-2. Guidance is provided on the use of the test method and classification methods. ISO 2014 All rights reserved v External exposure of roofs to fire Part 3:

13、 Commentary 1 Scope This part of ISO 12468 provides background and guidance on the use and limitations of the external fire exposure to roofs test method, the classification system, and the application of the data obtained. This part of ISO 12468 is designed to be of assistance to code officials, fi

14、re safety engineers, designers of buildings, and other persons responsible for the safety of persons in and around buildings. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated referenc

15、es, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 12468-1:2013, External exposure of roofs to fire Part 1: Test method 3 ISO 12468-1, test method In the development of the test method, an attempt was made

16、 to evaluate as many of the potential sources of external fire exposure a roof system could be subjected to as possible. Once identified, the test method attempted to define tests that simulated the identified possible exposure conditions, while at the same time, utilizing tests that already exist a

17、nd are described in national test methods. The ultimate goal of the test method development was to create an international test procedure which incorporated the most desirable elements of the existing test methods that could be used in national regulations and replace the wide variety of test method

18、s that exist in national regulations. The following are the three levels of fire exposure for roofs defined in ISO 124681:2013: Level A: A large burning brand falling onto the roof from an adjacent building. Level A considers the effect of wind and radiant heat. Level B: A medium burning brand comin

19、g from a fire in a neighbourhood and falling onto the roof. Level B considers the effect of wind but without additional radiant heat. Level C: A small burning brand transported by the wind from a remote fire and falling onto the roof. Level C considers the effect of the wind but without additional r

20、adiant heat. The following presentation starts with a summary background description of some fire scenarios, relevant for test methods regarding external fire exposure to roofs. Then the decisive evaluation parameters for different classification systems, based on test measurements and observations,

21、 are identified. 4 Fire scenarios Figures 1 to 6 show different types of external fire exposure to a roof. TECHNICAL REPORT ISO/TR 12468-3:2014(E) ISO 2014 All rights reserved 1 ISO/TR 12468-3:2014(E) Figure 1 Flying brand from a remote building or from environmental vegetation Figure 2 Radiation ex

22、posure from a fire in a nearby building Figure 3 Direct flame exposure together with radiation exposure from a fire in a nearby building in a dense small house area2 ISO 2014 All rights reserved ISO/TR 12468-3:2014(E) Figure 4 Combined exposure by flying brand and radiation from a nearby building Fi

23、gure 5 Radiation exposure, with or without a simultaneous flame contact, from flames emerging through a roof opening for fire venting or through a window opening in a compartment below the roof ISO 2014 All rights reserved 3 ISO/TR 12468-3:2014(E) Figure 6 Exposure by dripping melted material, flami

24、ng or not, together with sparks and flying brand, orginating from an external fire on the roof of a higher part of the building From the different types of external fire exposure shown in Figures 1 to 6, Level A of ISO 12468-1:2013 may relate to Figure 4, and Level B and Level C of ISO 12468-1:2013

25、may relate to Figure 1. Among the national standard test methods, the German test may simulate external fire exposure represented in Figure 6, the UK and French tests simulate exposure represented in Figure 4, the Scandinavian test and the North American Class C burning brand test simulate exposure

26、represented in Figure 1, and the North American “intermittent flame test” exposure is represented by Figures 3 and 5. The following brand sizes used in ISO 12468-1:2013 approximate the brands used in the North American roof fire test: Level A approximates the Class B brand described in ASTM E108 or

27、ULC S107 (North American tests). Level B is a smaller brand than the Class B brand but is larger than the Class C brand described in ASTM E108 or ULC S107 (North American tests). Level B was added to the test standard in 2012 to address the needs of the regulatory requirements in Japan. Level C appr

28、oximates the Class C brand described in ASTM E108 or ULC S107 (North American tests).4 ISO 2014 All rights reserved ISO/TR 12468-3:2014(E) 51 01 52 0 C (m) 0 0 2 4 6 8 10 12 14 16 P (kW/m ) max 2 Key a Maximum heat flux exposure (ISO 124681, Level A). Figure 7 Level of radiation exposure to roof fro

29、m nearby fire exposure as represented by Figure 4 Figure 7 gives a representative illustration of the level of the radiation exposure to a roof of a building from a fire in a nearby building as represented by Figure 4, relevant for the test method ISO 12468-1, Level A. The curves are showing the cal

30、culated maximum radiation at the base of the roof with a specified pitch as a function of the distance between the two buildings. The radiation exposure is caused by a fully developed compartment fire, comprising one compartment (dash-line curve) or two adjacent compartments (full-line curve) and ha

31、ving a size characteristic of fires in a multi-storey office building or dwelling-house. For comparison, the figure also includes the level of the maximum total heat flux to which the test specimen shall be exposed according to the test method ISO 12468-1, Level A. The calculated maximum radiation (

32、P max ) to the base of a roof on a building from a fire in a nearby building as a function of the distance (C) between the two buildings is plotted in Figure 7. The thermal exposure from the nearby building is characterized by a fully developed fire in a compartment with the opening factor Ah/A tot=

33、 0,06 m 1/2and surrounding structures of aerated concrete with the density 500 kg m 3 . The fire load density is 170 MJ m 2surrounding area. The area of the window openings of the compartment facing on to the exposed roof is 5 1,5 m 2 . The pitch of the roof is 30 and the base of the roof is located

34、 at the same level as the lower edge of the window openings of the compartment(s) in fire. The dash-line curve refers to a fire in one compartment and the full-line curve to a fire simultaneously in two adjacent compartments. 5 Evaluation parameters Measurements and observations, prescribed in the t

35、est method ISO 12468-1, enable the following evaluation parameters to be used in the classification systems described in ISO 12468-2: a) maximum length of external fire spread in any direction related to a defined measuring zone; ISO 2014 All rights reserved 5 ISO/TR 12468-3:2014(E) b) occurrence of

36、 any burning material (flaming droplets or debris) falling from the exposed surface, within a prescribed period of time, if any; c) time of fire penetration, within a prescribed period of time, as defined. Combining the performance criteria prescribed in ISO 12468-1:2013 and the measurements and obs

37、ervations specified in the test methods points out the following performance parameters to be applied as obligatory in the classification system. fire penetration, determined by measurements and observations according to ISO 12468-1:2013, 11.3; fire spread over the external surface of the roof, expr

38、essed by the maximum length upwards and downwards according to ISO 12468-1:2013, 11.2; flaming droplets or debris falling from the exposed surface over the eaves, determined by observations according to ISO 12468-1:2013, 11.2.2. 6 ISO 124682, classification of roofs Six classifications have been est

39、ablished for roof systems, two based on the Level A exposure conditions, two based on the Level B exposure conditions, and two based on the Level C exposure conditions in ISO 12468-1:2013. The classes are described as follows: Test Level A Level B Level C Test Result Large brand, radiation, and wind

40、 Medium brand and wind Small brand and wind Class A1 A2 B1 B2 C1 C2 Fire penetration of openings None None within 15 min None within 30 min None within 15 min None within 30 min None within 15 min External fire spread Does not reach the limits of the measuring zone within 30 min Does not reach the l

41、imits of the measuring zone within 15 min Does not reach the limits of the measuring zone within 30 min Does not reach the limits of the measuring zone within 15 min Does not reach the limits of the measuring zone within 30 min Does not reach the limits of the measuring zone within 15 min Falling or

42、 flam- ing droplets or debris None within 30 min None within 15 min None within 30 min None within 15 min None within 30 min None within 15 min The classification system was developed to address the needs of countries building regulatory systems (building codes). The system is flexible enough to per

43、mit the regulation of roofs exposed to an external fire exposure of varying degrees of severity and varying degrees of expected performance. The most fire resistant roofs are classified as Class A1; the least fire resistant roofs are classified as Class C2.6 ISO 2014 All rights reserved ISO/TR 12468

44、-3:2014(E) Bibliography 1 ISO 12468-2, External exposure of roofs to fire Part 2: Classification of roofs 2 ISO 13943, Fire safety Vocabulary 3 ASTM E108, Standard Test Method for Fire Tests of Roof Coverings 4 CAN/ULC-S107, Methods of Fire Tests of Roof Coverings ISO 2014 All rights reserved 7 ISO/TR 12468-3:2014(E) ISO 2014 All rights reserved ICS 13.220.50;91.060.20 Price based on 7 pages