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Volume 46 (1997)
- Issue 1+2 Pages 1-
Volume 46, Issue 1+2
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Paper
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Takeshi SAGA1997 Volume 46 Issue 1+2 Pages 1-11
Published: 1997
Released on J-STAGE: August 18, 2011
JOURNAL FREE ACCESSIn order to clarify the firebreak method and evacuation planning of big fire in a built-up area of wooden houses, it is important to discuss the estimative method of temperature fields on the fire gas flow and the general behavior of the flame on big fire.
This study purposes to obtain a method of estimating the temperature distribution of fire gas flow in city fire under strong wind.
The author has considered fire spread and burning behavior, and then attempted to assume a plane heat source as the experimental model of burning area. In this paper, equations for temperature distributions downwind from this heat source are discussed by theoretical consideration. These formulas are derived by determining several parameters appearing in this model, and shown as the function of dimensionless temperature (Ψ), dimensionless velocity (Λ), Froude number (Fr), and ratio (X/D) of downwind distance (X) to wide (D) of a plane heat source.
Several formulas derived in this paper are discussed by experimental consideration.
In order to examine the relation between theory and experiment, measurements of temperature and velocity are performed in a wind tunnel which is placed a square vessel for burning alcohol.
The validity and limitation of equations are clarified by this wind tunnel test.View full abstractDownload PDF (931K) -
Akiko MURATA1997 Volume 46 Issue 1+2 Pages 13-25
Published: 1997
Released on J-STAGE: August 18, 2011
JOURNAL FREE ACCESSFollowing the Hyogoken-nambu Earthquake, many collapsed buildings spread fire extensively, and collapsed buildings on narrow streets prevented the fire-brigade from passing. This indicated that characteristics of the area including building density and width of the street, related to the fire damage.
In this paper, we discuss the relation between the fire damage following the Hyogoken-nambu Earthquake and the characteristics of each ward in Kobe City.
We surveyed the characteristics of the area of fire damage using papers and reports on the Earthquake as reference. Statistic data corresponding to the characteristics were selected based on the survey results, and the correlation between fire damage and statistics of each ward in Kobe City was analyzed.
Conclusions are as follows:
(1) Factors which can mitigate damage are trees near buildings or streets, various water supplies, and fire fighting by residents. Factors which spread fire are the remoteness to water supply and the closeness to hazardous material factories.
(2) Characteristics of the area which have high fire risk are described as follows: high density of old small houses, high ratio of the elderly living alone, low ratio of the growth of population, high density of hazardous material factories, and high number of building fires per year.
(3) Comparison of statistics related to fire damage indicates that some cities such as the 23 wards in Tokyo have similar risk to Kobe City.View full abstractDownload PDF (1234K) -
Katsuhiro KINOSHITA, Norimichi WATANABE1997 Volume 46 Issue 1+2 Pages 27-31
Published: 1997
Released on J-STAGE: August 18, 2011
JOURNAL FREE ACCESSElectric wires and distributing utensils collected at the fire scene may leave the marks showing the phenomenon of tracking, arcing and short circuits that may take place. In cases when the cause of making the marks may be clear, it turns out to be a very important clue for proving the cause of the fire. When an organic material is heated, it forms finally hexagonal crystals called graphite. There are many kinds of the carbons because amorphous carbon varies continuously to graphite. The degree of graphitization could be known by measuring distance between 002-surfaces in the crystal by using X-ray diffraction. The authors carried out the analysis of the crystal structure to clear the degree of graphitization by X-ray diffraction for the carbonized organic insulating materials being heated at various temperatures by an electric heating furnace, and the observation of the shape of the carbonized materials by SEM.
The results obtained are summarized as follows:
(1) The diffraction peak of carbonized organic insulating materials produced by tracking is closer to 3.354 Å than those of materials carbonized by the electric heating furnace. The influence of artificial additives on the diffraction peak for the materials carbonized by tracking is smaller than those of materials carbonized by the furnace.
(2) X-ray diffraction may be useful to decide whether or not the materials collected from the fire scene took part in the process of electrical fire.View full abstractDownload PDF (507K) -
Yuichi WATANABE, Sanae MATSUSHIMA, Tokiyoshi YAMADA1997 Volume 46 Issue 1+2 Pages 33-43
Published: 1997
Released on J-STAGE: August 18, 2011
JOURNAL FREE ACCESSIn order to make smoke movement of fire clear in a deep underground parking space, a series of experiments were conducted with the 1/10 scale model of the four stories basement under natural ventilation condition. This model consists of four stories parking spaces of relatively large area compartment and two stairwells having vertical shafts. For understanding the smoke movement and the optical density of the smoke, the concentration of carbon dioxide were measured at many points as a substitute for fire smoke.
As a result, it was found that carbon dioxide gas was distributed over the large parking space of the fire floor by natural convection, and the optical density of the smoke increased all over the parking space with the lapse of time. The smoke was two layered near fire source, which was thicker in upper layer and thinner in lower layer. On the other hand, in the parking rooms apart from the fire source point, the distribution of the optical density were uniform from the ceiling to the floor.
Whereas, the experimental data of carbon dioxide gas concentration were compared between with the prediction by the two layer zone model. The prediction data were larger than the experimental data. But the predictive values normalized by the data near fire source agreed well with the experimental values normalized by that in the parking space, but not in the stairwells.View full abstractDownload PDF (918K) -
Kenjiro YASUNO, Yoshiro NAMBA, Tadahiko NISHITANI, Hideo MATSUOKA1997 Volume 46 Issue 1+2 Pages 45-55
Published: 1997
Released on J-STAGE: August 18, 2011
JOURNAL FREE ACCESSBig fire has often occurred since the dawn of history in Japan. And Japan has the world worst record even in the scale. The big fire that building burn-out area is over 33,000 m2 in the 20's of Showa has occurred numerously. After that we were toward one goal called "the fire prevention of a city". As a result, big fire has not been breaking out since the big fire of Sakata in Showa 51 (1976). And the fire prevention measure has moved to the building fire prevention of large-scale/upper layers buildings from the big fire prevention of city area since this time. However, the occurrence of big fire has not been eradicated at all. The danger of big fire occurrence is still remained under the unfavorable conditions like a large earthquake and a strong leeward. Thereupon we analyzed about the fire spread formula of wooden building both in ordinal and earthquake disaster.
The conclusion is as follows.
(1) We changed the fire spread formula as the expression of K city in eq. (3) from eq. (1) with an easier style. It may express in the eq. (3) from in eq. (1).
(2) Fires of K city and M city are shown to Fig. 4 as an example under G=100m2, v=3 m/sec. If each burn-out area is compared, it is understood that the structure of M city after about 30 years is difficult burning than the building fire of K city.
(3) Applying eq. (3) about the big fire from Showa 21 to Showa 27, Table 2 was obtained. Coefficients a1 and c1 are able to indicate each eq. (8) and eq. (9). The correlation figures of measurement value and prediction values of all fire data of Table 2 were shown to Fig. 9. As multiple coefficient of correlation R=0.983, it is agreeing fairly well.
(4) It was shown like Table 4 and also Fig. 10 about the Sakata big fire. It is able to indicate in eq. (3) and R=0.999. It is thought that the Sakata big fire became difficult to burn more previous big fire of the Showa 20's so that shown in Fig. 11.
(5) About the expression at the time of the Kobe earthquake, we re-examined data a part once again. a1 and c1 are able to indicate each eq. (11) and eq. (12). a1 is almost not change the previous paper of ours.
The relation c1 and xG is eq. (13) and R=0.899. The correlation between burn-out area of prediction value and measurement is about 0.9. It is agreeing fairly well.View full abstractDownload PDF (874K)
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