Fire Science and Technology
Online ISSN : 1882-0492
Print ISSN : 0285-9521
ISSN-L : 0285-9521
Volume 23 , Issue 5
Showing 1-2 articles out of 2 articles from the selected issue
  • Takao Wakamatsu, Kayoko Mizuno, Tatsuaki Tanaka
    2004 Volume 23 Issue 5 Pages 338-400
    Published: 2004
    Released: October 20, 2007
    JOURNALS FREE ACCESS
    Steel is often used as an assembly of main structure such as columns and beams on external walls of buildings. Such steel structural members lose their structural function when the temperature of the steel rises due to spouting hot gas or radiation heating via openings, such as windows, upon fire in a neighboring compartment. This paper presents a calculation model for predicting temperature properties of steel structural members upon fire heating and proposes it as a practical tool for evaluation of fire resistance. Establishing a model of three-dimensional heat flow analysis is focused on considering a heat flow toward an axis of a member. Spouting hot gas and radiation heating through openings are taken into consideration as a heat source upon modeling. Firstly, spouting hot gas properties and radiation heating through openings were formulated in order to model their heating impact on temperature of members. Then a model of three-dimensional heat flow analysis (the model of calculating temperature), involving these results as main components, was created. This model also helps the practical prediction of temperature properties of steel structural members that local heating brings about.
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  • Masayuki Mizuno, Kazunori Harada, Takao Wakamatsu
    2004 Volume 23 Issue 5 Pages 402-462
    Published: 2004
    Released: October 20, 2007
    JOURNALS FREE ACCESS
    The Japanese Ministry of Construction's Notification 1441 (2000) on "Verification Method for Egress Safety from a Fire Floor" is composed of a set of prescribed characteristic input values for fire load density, occupant density, etc., coupled with a set of simplified formulae to calculate fire and evacuation behavior. The nominal egress time margin is calculated by combining these values and formulae with building design variables, such as room area and ceiling height. To clarify the degree of safety implemented in the verification method, the stochastic variability in input values and uncertainties in calculation formulae have been examined. Based on existing research and survey results, variability and uncertainty are expressed in terms of probability density functions. The target levels of egress from a fire room and a fire floor were also discussed in this study. The calculation method was analyzed using the methods of Reliability Engineering. The Limit State Function was selected as the difference between the nominal time margin of egress safety and the actual, stochastic time margin of egress safety. By examining the safety level of Limit State Function, the Target Safety Index and the Acceptable Probabity of Failure implied in the Verification Method is clarified for typical office building in Japan. This work has clarified that: (1) Two variables which contain inevitable stochastic variation (Fire Load Density and Occupant Density) are recognized as Type A variables, and six variables which contain uncertainties due to the incompleteness of the prediction method (Walking Velocity, Specific Flow Rate, Time to Start the Evacuation, Fire Growth Rate over combustible contents, Fire Growth Rate over lining materials, and Smoke Filling Time) are recognized as Type B variables. (2) The coefficients of variation are large in both Type A and Type B variables, ranging from 13 to 235 %. There is a need to reduce the uncertainties associated with Type B variables. (3) The Partial Safety Factors vary in the range of - 0.45 to 4.97. (4) The implied safety index of the calculation method is in the range of 1 to 3 depending on the method of smoke control and floor area on the condition of egress from a fire room, and in the range of 2 to 3 it is fairly independent on the method of smoke control and floor area on the condition of egress from a fire floor. (5) In comparison with Type A variability, the effect of Type B uncertainties (prediction error) is not negligible. (6) Possible combination of partial safety factors are proposed by 0.2, 2-6, 0.9 for fire load density, escape start time and smoke filling time on the condition of egress from a fire room for typical office buildings with single side corridor in Japan, and by 0.7, 4.8, 2.6 and 0.9 for fire load density, escape start time, fire growth rate and smoke filling time on the condition of egress from a fire floor.
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