Fire resistance estimation method

Abstract

To provide a fire-resistance performance estimation method of a wood steel hybrid member capable of simply estimating the fire-resistance performance of the wood steel hybrid member.SOLUTION: A method for estimating the fire-resistant performance of a wood steel hybrid member 10 including a steel material 12 and a wood covering material 14 for fire-resistant covering of the steel material 12, the method comprising: a pseudo member temperature rise coefficient is calculated from the shape and cross-sectional dimensions of the steel material 12 and the tree species and coating thickness of the woody coating material 14, and the fire resistance performance of the wood steel hybrid member 10 is estimated based on the calculated pseudo member temperature rise coefficient.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for estimating fire resistance of a wood-steel hybrid member made of wood and steel. [Background technology]

[0002] The applicant of the present patent has previously developed composite members that combine steel members and wood members (see, for example, Patent Document 1). In particular, to ensure one-hour fire resistance, the applicant has developed a wood-steel hybrid beam, which is a structural member in which a steel beam is fire-resistant-coated with wood (hereinafter referred to as a wood coating material) (see, for example, Patent Document 2). This wood coating material burns at about 0.7 to 1.0 mm / min during a fire, but stops burning after the fire, thereby suppressing the temperature rise of the steel beam that supports the load and preventing collapse. It is considered that the fire resistance performance of members such as a wood-steel hybrid beam, such as the burning properties of the wood coating material, whether or not the fire stops after the fire, and the temperature transition of the steel, varies depending on the species and coating thickness of the wood coating material, and the shape and cross-sectional dimensions of the steel.

[0003] Meanwhile, when sprayed rock wool or calcium silicate boards are used as fireproof coating materials for steel, a method has been proposed in the fireproof performance verification method in which the member temperature rise coefficient is calculated from the shape and cross-sectional dimensions of the steel and the type and thickness of the fireproof coating material, and the maximum temperature of the steel in the event of a fire is estimated (see, for example, Non-Patent Document 1). It is said that the larger the member temperature rise coefficient, the more likely the temperature of the steel will rise. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-084037 A [Patent Document 2] Patent application No. 2020-148315 (currently unpublished) [Non-patent literature]

[0005] [Non-Patent Document 1] The Building Center of Japan et al., "2001 Edition: Explanation of Fire Resistance Verification Method and Calculation Examples and Explanations," pp.85-109, pp.173-188, 2001 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, in developing the above-mentioned wood-steel hybrid beam, the applicant of the present patent created multiple test specimens using the species and thickness of the wood covering material and the cross-sectional dimensions of the steel as parameters, and confirmed the performance of each specification through fire resistance tests. However, when developing a member with specifications different from the specifications whose performance was confirmed in the fire resistance tests (specifically, specifications with different species and thickness of the wood covering material, different shapes and cross-sectional dimensions of the steel, etc.), it is costly and time-consuming to conduct a fire resistance test each time. For this reason, there has been a demand for a method that can easily estimate the fire resistance performance of wood-steel hybrid members without relying on fire resistance tests.

[0007] The present invention has been made in consideration of the above, and aims to provide a method for estimating the fire resistance of a wood-steel hybrid component, which can easily estimate the fire resistance of a wood-steel hybrid component. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, the method for estimating the fire resistance of a wood-steel hybrid component of the present invention is a method for estimating the fire resistance of a wood-steel hybrid component comprising a steel material and a wood covering material that provides a fire-resistant covering for the steel material, and is characterized in that a pseudo component temperature rise coefficient is calculated from the shape and cross-sectional dimensions of the steel material and the tree species and covering thickness of the wood covering material, and the fire resistance of the wood-steel hybrid component is estimated based on the calculated pseudo component temperature rise coefficient.

[0009] In addition, the method for estimating the fire resistance of a wood-steel hybrid component according to the present invention is characterized in that, in the above-mentioned invention, the pseudo component temperature rise coefficient is calculated as an index showing how easily the temperature of steel material coated with an inorganic fire-resistant coating material rises, by assuming that the thermal resistance coefficient calculated based on the heat transfer coefficient of the steel material surface and the thermal conductivity of the fire-resistant coating material is 1. Effect of the Invention

[0010] According to the method for estimating the fire resistance of a wood-steel hybrid component of the present invention, which is a method for estimating the fire resistance of a wood-steel hybrid component comprising a steel material and a wood covering material that provides fire resistance covering for the steel material, a pseudo component temperature rise coefficient is calculated from the shape and cross-sectional dimensions of the steel material and the tree species and covering thickness of the wood covering material, and the fire resistance of the wood-steel hybrid component is estimated based on the calculated pseudo component temperature rise coefficient, thereby achieving the effect of easily estimating the fire resistance of a wood-steel hybrid component without relying on fire resistance tests. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a member to which an embodiment of the method for estimating the fire resistance of a wood-steel hybrid member according to the present invention is applied, where (1) is a cross-sectional view in the case of three-sided heating, (2) is a cross-sectional perspective view thereof, (3) is a cross-sectional view in the case of four-sided heating, and (4) is a cross-sectional perspective view thereof. [Diagram 2] Figure 2 shows the cross-sections of the test specimens, (1) and (2) are test specimen A, (3) and (4) are test specimen B, and (5) and (6) are test specimen C. Additionally, (1), (3), and (5) are the general beam parts, and (2), (4), and (6) are the cladding attachment parts. [Diagram 3] FIG. 3 is a diagram showing the transition of steel temperature in a hiba wood-steel hybrid beam. [Figure 4] FIG. 4 shows the transition of steel temperature in a larch wood-steel hybrid beam. [Diagram 5] FIG. 5 shows the relationship between the simulated component temperature rise coefficient and the maximum temperature rise value of steel, where (1) is for Hiba and (2) is for Larch. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the method for estimating fire resistance of a wood-steel hybrid member according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment.

[0013] In this embodiment, a pseudo member temperature rise coefficient is calculated from the shape and cross-sectional dimensions of the steel material in the wood-steel hybrid member and the species and thickness of the wood covering material, and the maximum temperature of the steel material and the presence or absence of burning of the wood are estimated. Then, the fire resistance performance of the wood-steel hybrid member is estimated in a simple manner. In this embodiment, the following (1) to (4) are assumed.

[0014] (1) The steel material assumed is an H-shaped steel that is heated from three directions (below, left, and right) (see Figure 1 (1) and (2)), or an H-shaped steel that is heated from four directions (up, down, left, and right) (see Figure 1 (3) and (4)).

[0015] (2) The target species of wood covering material are larch and Japanese cypress.

[0016] (3) The pseudo member temperature rise coefficient (hereinafter referred to as pseudo member temperature rise coefficient) is calculated from the shape and cross-sectional dimensions of the steel material of the wood-steel hybrid member and the coating thickness of the wood coating material. The method for calculating the pseudo member temperature rise coefficient will be described later.

[0017] (4) From the results of multiple fire resistance tests conducted for the purpose of developing a wood-steel hybrid beam that ensures one-hour fire resistance, it has been found that if the pseudo-component temperature rise coefficient is 0.077 or less when larch is used as the wood covering material, and if the pseudo-component temperature rise coefficient is 0.065 or less when Japanese cypress is used as the wood covering material, the maximum temperature of the steel can be estimated and the wood covering material will stop burning. Therefore, these test results will be used to estimate fire resistance performance.

[0018] The wood-steel hybrid component 10 in Figs. 1(1) and (2) is composed of a steel beam 12 made of H-shaped steel and a wooden covering material 14 that covers the bottom, left, and right three sides of the beam. A floor material 16 is provided on the top surface of the steel beam 12. The steel beam 12 and the wooden covering material 14 are fastened with fixing members (not shown), and the surface of the wooden covering material 14 that passes through the fixing members is sealed with filler wood 18. The fixing members are rod-shaped bodies with a head and a threaded portion, and the head is placed on the web of the steel beam 12 and the threaded portion penetrates the web and is screwed into the wooden covering material 14. The wood-steel hybrid component 10A in Figs. 1(3) and (4) is composed of a steel beam 12 made of H-shaped steel and a wooden covering material 14 that covers the top, bottom, left, and right four sides of the beam.

[0019] (Calculation method of pseudo component temperature rise coefficient) Next, a method for calculating the pseudo component temperature rise coefficient in a wood-steel hybrid component will be described. In the fire resistance performance verification method, the component temperature rise coefficient h is used as an index showing how easily the temperature of steel material covered with inorganic fire-resistant coating material (sprayed rock wool 25mm thick or more, or calcium silicate board 20mm thick or more) rises. The component temperature rise coefficient h is calculated using the following formula (1) based on the cross-sectional shapes of the steel material and coating material, and the physical properties of the coating material, and it is said that the higher the component temperature rise coefficient h, the easier the steel material temperature will rise.

[0020]

number

[0021] Here, Hs: heating circumference of steel [m], As: cross-sectional area of ​​steel [m 2 ], Hi: heating circumference of the coating material [m], Ai: cross-sectional area of ​​the coating material [m 2 ], Hs / As: cross-sectional shape factor of steel [m -1 ], φ=Hi / Hs: Circumference ratio of the part of the coating material and the steel material that is subjected to heat [-], K0,R,C: Constants determined by the physical properties of the coating material and the type of steel material (K0=ht / ρ scs : Basic temperature rise coefficient [m / min] obtained by dividing the heat transfer coefficient of the steel surface by the heat capacity of the steel, R=ht / ki: Thermal resistance coefficient [m-1 ], C=ρ ici / ρ scs : Heat capacity ratio of coating material to steel [-]).

[0022] In formula (1), the values ​​of Hs, As, Hi, Ai, and φ can be determined if the cross-sectional dimensions and shapes of the steel and cladding material are known. On the other hand, the constants K0, R, and C, which are determined by the physical properties of the cladding material and the type of steel, must be identified from test results.

[0023] According to the following reference 1, the basic temperature rise coefficient K0 is uniquely determined by the shape of the steel material and the number of heated surfaces. Therefore, using the values ​​used in the fire resistance performance verification method described in the above non-patent document 1, we will use K0 = 0.00089 when heated from four sides, and K0 = 0.00067 when heated from three sides excluding the top surface.

[0024] [References 1] Junichi Suzuki et al., "Simple Prediction Formula for Temperature Rise of Uncoated Steel in a Fire," Journal of Structural Engineering, Architectural Institute of Japan, Vol. 553, pp. 143-148, 2002

[0025] The heat capacity ratio C is determined by the density and specific heat of the steel and coating material. Therefore, the change in physical properties due to temperature rise is not taken into consideration, and the heat capacity ratio C is calculated based on the physical properties at room temperature.

[0026] The thermal resistance coefficient R is calculated based on the heat transfer coefficient of the steel surface and the thermal conductivity of the covering material, but the value has not been determined when wood is used as the covering material (see Non-Patent Document 1 above). Therefore, for convenience, we will assume that R=1.

[0027] From the above, if the component temperature rise coefficient h calculated assuming R = 1 is defined as the pseudo component temperature rise coefficient h', the following equation (2) is obtained.

[0028]

number

[0029] (Verification by fire resistance test) Based on the results of multiple fire resistance tests conducted with the aim of developing a wood-steel hybrid beam that ensures one-hour fire resistance, we verified the possibility of estimating the steel temperature of a wood-steel hybrid beam and whether or not it will stop burning using the pseudo-component temperature rise coefficient h'.

[0030] The specifications for which the fire resistance tests were conducted are shown in Table 1, and the specifications of the test specimens are shown in Figure 2. Figure 2 (1) and (2) show test specimen A, (3) and (4) show test specimen B, and (5) and (6) show test specimen C. Figures 3 and 4 show the changes in steel temperature for each specification for which the fire resistance tests were conducted. Table 1 also shows the simulated component temperature rise coefficient for each specification for which the fire resistance tests were conducted, the maximum temperature rise from the initial temperature of the steel in the fire resistance tests, and the results of whether or not the wood covering material stopped burning.

[0031] [List of results for pseudo-component temperature rise coefficient, maximum temperature rise value of steel, and whether or not burning has stopped] [Table 1]

[0032] Using the steel temperature obtained in the test, the average steel temperature was calculated for each time point at the top flange, bottom flange, and web, and the temperature rise from the initial temperature was calculated by subtracting the initial temperature. Table 1 shows the maximum temperature rise ΔT (maximum temperature rise) from the initial temperature. For specimens 2, 3, 9, and 13, the wood covering material did not stop burning even after the test was completed (after a total of 25 hours had passed, including 1 hour of heating and 24 hours of cooling), and the steel temperature continued to rise. Therefore, for safety reasons, water was poured onto the specimens after the test was completed to extinguish the fire and cool them down. For specimen 1, the maximum steel temperature exceeded 450°C, and the wood covering material had burned out by the end of the test. In the judgment of burning out, a circle indicates a specimen that stopped burning, and a cross indicates a specimen that did not stop burning or burned out (the maximum steel temperature exceeded 450°C).

[0033] Figure 5 shows a graph of the relationship between the pseudo-component temperature rise coefficient h' and the maximum temperature rise value ΔT of steel, shown in Table 1. Figure 5 (1) shows the case where Japanese cypress was used as the wooden covering material, and (2) shows the case where larch was used as the wooden covering material. In the figure, circles indicate test specimens where the fire stopped, and crosses indicate test specimens where the fire did not stop. The figure also shows the equation for the regression line and correlation coefficient R obtained by regression analysis of the results of test specimens that stopped burning in the fire resistance test, with the pseudo-component temperature rise coefficient h' set to x and the maximum temperature rise value ΔT of steel set to y.

[0034] As shown in Figure 5, for both Japanese cypress and larch specimens that stopped burning in the fire resistance tests, the greater the pseudo-component temperature rise coefficient, the greater the maximum temperature rise value of the steel. Therefore, if the specifications are such that the fire will stop, it is possible to estimate the maximum temperature rise value of the steel by calculating the pseudo-component temperature rise coefficient from the specifications of the wood covering material and the cross-sectional dimensions of the steel beam.

[0035] In addition, considering that the wood-steel hybrid beam using Japanese cypress did not stop burning in test specimen 9 because the length of the filler wood was short, it is estimated that the beam will stop burning if the pseudo-component temperature rise coefficient is 0.065 or less.

[0036] On the other hand, in the case of the larch wood-steel hybrid beam, observation of the specimen after testing suggested that the reason why specimen 13 did not stop burning was possibly due to poor construction of the filler wood. Assuming that there is no poor construction of the filler wood, it is estimated that the larch wood-steel hybrid beam will stop burning if the simulated member temperature rise coefficient is 0.077 or less.

[0037] According to this embodiment, by calculating the pseudo component temperature rise coefficient, it is possible to easily estimate the maximum temperature of the steel material of a wood-steel hybrid beam using Japanese cypress and larch and whether or not the wood covering material will stop burning. Therefore, it is possible to easily estimate the fire resistance performance of a wood-steel hybrid beam without conducting a fire resistance test. This also reduces the cost and effort required for fire resistance testing and improves the efficiency of component development.

[0038] In addition, by accumulating fire resistance test data when other tree species are used as wood covering materials, it will be possible to increase the variety of tree species that can be estimated using the pseudo component temperature rise coefficient.

[0039] In the above embodiment, the steel material is an H-shaped steel, but the present invention is not limited to this. For example, by accumulating fire resistance test data for steel material of other shapes, such as square steel, it is possible to expand the variations in steel material shapes that can be estimated by the pseudo-member temperature rise coefficient.

[0040] As described above, the method for estimating the fire resistance of a wood-steel hybrid component of the present invention is a method for estimating the fire resistance of a wood-steel hybrid component comprising a steel material and a wood covering material that provides a fire-resistant covering for the steel material, and calculates a pseudo component temperature rise coefficient from the shape and cross-sectional dimensions of the steel material and the tree species and covering thickness of the wood covering material, and estimates the fire resistance of the wood-steel hybrid component based on the calculated pseudo component temperature rise coefficient, so that the fire resistance of the wood-steel hybrid component can be easily estimated without relying on fire resistance tests. [Industrial Applicability]

[0041] As described above, the fire resistance estimating method according to the present invention is useful for evaluating the fire resistance of wood-steel hybrid components, and is particularly suitable for simply estimating the fire resistance. [Explanation of symbols]

[0042] 10,10A Wood-steel hybrid material 12 Steel beam 14 Wood cladding 16 Flooring 18 Buried Wood

Claims

[Claim 1] A method for estimating the fire resistance of a wood-steel hybrid member having a steel material and a wood covering material that covers the steel material, comprising: The method calculates an approximate component temperature rise coefficient from the shape and cross-sectional dimensions of the steel material and the species and thickness of the wood covering material, and estimates the fire resistance of the wood-steel hybrid component based on the calculated approximate component temperature rise coefficient. This method is characterized in that the pseudo component temperature rise coefficient is calculated as an index showing how easily the temperature of steel material covered with an inorganic fire-resistant coating material rises, and is calculated by assuming that the thermal resistance coefficient, which is calculated based on the heat transfer coefficient of the steel material surface and the thermal conductivity of the fire-resistant coating material, is 1.

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