Method for evaluating the thermal insulation performance of void slabs

Abstract

To provide a method for evaluating the heat insulation performance of a void slab that can obtain an evaluation result closer to the actual heat insulation performance of a solid void slab. 【Solution means】 A plurality of voids 14 are evenly spaced at a minimum allowable interval d 14min in the measurement area A 19 of the reinforced concrete 13, and test specimens 19 of a plurality of void slabs with different total thicknesses and void thicknesses are prepared. For each test specimen 19, the heat transfer coefficient in the thickness direction in the measurement area A 19 is actually measured to obtain test specimen measured data λ 19 or U 19 in the void slab 10 which is the actual evaluation object, a plurality of voids 14 are arranged in the reinforced concrete 13 at a minimum allowable interval d 14min or more intervals d 14 The thermal conductivity λ 15 or heat transfer coefficient U 15 in the thickness direction of the void arrangement area 15 is estimated based on the test specimen measured data λ 19 or U 19 to calculate the heat transfer coefficient U 10 in the thickness direction of the entire void slab 10.

Description

[Technical Field]

[0001] This invention relates to a method for evaluating the thermal insulation performance of a void slab in which voids are embedded within reinforced concrete. [Background technology]

[0002] This type of void slab is a concrete slab in which block-shaped voids made of foamed resin such as expanded polystyrene are embedded in concrete, and is used, for example, as a floor slab in a building (see Patent Document 1, etc.). Advantages of using void slabs include a reduction in the amount of concrete poured and a lighter floor slab, and in recent years, attention has also been paid to the improved thermal insulation performance due to the foamed resin used as the void material.

[0003] Patent Document 2 discloses a method for evaluating the thermal insulation performance of a void slab, which involves separating a heating box and a cooling chamber with a void slab and heating the inside of the heating box with a heater to determine the thermal transmittance of the void slab. The void slab test specimen used in the evaluation test is designed to have larger void spacing and smaller void area and thickness than an actual void slab that will be constructed, thereby ensuring that the thermal insulation performance of the actual void slab is higher than the thermal insulation performance obtained from the test specimen. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-017356 [Patent Document 2] Japanese Patent Publication No. 2023-111518 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The evaluation results obtained using the thermal insulation performance evaluation method for void slabs described in the aforementioned Patent Document 2 are lower than the actual thermal insulation performance of void slabs that are actually constructed. The present invention aims to provide a method for evaluating the thermal insulation performance of void slabs that yields evaluation results closer to the actual thermal insulation performance of real void slabs. [Means for solving the problem]

[0006] To solve the aforementioned problems, the method for evaluating the thermal insulation performance of a void slab according to the present invention involves preparing multiple void slab test specimens in which multiple voids are embedded equally and at the minimum permissible intervals within the reinforced concrete of the measurement area, and in which the total thickness and void thickness differ from each other, and obtaining actual test specimen measurement data by measuring the thermal transmittance in the thickness direction in the measurement area for each test specimen. The method is characterized by estimating the thermal conductivity or thermal transmittance in the thickness direction of the void arrangement region in the actual void slab that is the subject of evaluation, where multiple voids are embedded in the reinforced concrete at intervals greater than or equal to the minimum allowable interval, based on the measured data of the test specimen, and then calculating the thermal transmittance in the thickness direction of the entire actual void slab.

[0007] Preferably, the solid void slab has a void arrangement region and a solid region in which no voids are provided within the reinforced concrete, and the solid region includes a plurality of solid regions with different thicknesses. The calculation is performed based on the area ratio of the void-placed region to the total area of ​​the solid void slab, the estimated value of the thermal conductivity or heat transfer coefficient, and the area ratio, thickness, and thermal conductivity of each solid region to the total area.

[0008] Preferably, a predetermined number of structural reinforcements are placed between the main surfaces of adjacent voids in the test specimen, in a plan view. The aforementioned minimum permissible spacing is set based on the required distance between adjacent structural reinforcements and the required distance between a void and the structural reinforcement immediately adjacent to it. [Effects of the Invention]

[0009] According to the thermal insulation performance evaluation method of the present invention, it is possible to obtain evaluation results that are closer to the actual thermal insulation performance of a real void slab. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a plan view showing an example of a real void slab to be evaluated by the thermal insulation performance evaluation method according to one embodiment of the present invention, with the voids embedded inside indicated by solid lines. [Figure 2] Figure 2 is a cross-sectional view taken along the line II-II in Figure 1. [Figure 3] Figure 3 is a cross-sectional view taken along the line III-III in Figure 1. [Figure 4] Figure 4 is a plan view of one of the test specimens used in the thermal insulation performance evaluation method, along the line IV-IV in Figure 5(a), with the voids embedded inside indicated by solid lines. [Figure 5] Figures 5(a) to 5(c) are side cross-sectional views of test specimens with different thicknesses. [Figure 6] Figure 6 is a cross-sectional view along the line VI-VI in Figure 4. [Figure 7] Figure 7 is a front cross-sectional view of the test building during the process of acquiring actual measurement data of the test specimen in the thermal insulation performance evaluation method described above. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described below with reference to the drawings. As shown in Figure 1, in this embodiment, the thermal insulation performance of a void slab constituting the floor slab 2 of a reinforced concrete building 1 such as an office building, apartment building, factory, or warehouse is evaluated. The void slab that is actually being evaluated is referred to as the actual void slab 10. As shown in Figure 2, the actual void slab 10 is made of reinforced concrete 13 consisting of concrete 11 and structural reinforcement 12, and includes a plurality of voids 14. The structural reinforcement 12 includes mutually orthogonal main reinforcement 12a and distribution reinforcement 12b.

[0012] As shown in FIG. 1, the solid void slab 10 has a void arrangement region 15 and a solid region 16. As shown in FIGS. 1 and 2, in the void arrangement region 15, a plurality of voids 14 are embedded in the reinforced concrete 13 at equal intervals. The void 14 is composed of a rectangular block in plan view made of a foamed resin such as styrofoam. As shown in FIG. 2, the outer peripheral portion 14e of the void 14 has a thickness that decreases toward the outer edge 14ec, and the cross section is triangular or trapezoidal. The interval d between the voids 14 in the solid void slab 10 14 (FIG. 1) is the allowable minimum interval d described later 14min (FIG. 6) or more (d 14 ≧d 14min ), preferably approximately equal to the allowable minimum interval d 14min (d 14 ≒d 14min ). As shown in FIGS. 1 and 3, the void arrangement region 15 extends outward in plan view by half of the void interval d 14 (d 14 / 2) from the outermost void 14B arranged. In FIG. 3, the boundary between the void arrangement region 15 and the solid region 16 is virtually indicated by a dashed line BL.

[0013] As shown in FIG. 2, a plurality of (for example, n = 3) reinforcing bars 12 are arranged in parallel in the reinforcement height on the upper surface side or the bottom surface side between adjacent voids 14 of the solid void slab 10. The number of reinforcing bars (n) between these voids is set so as to ensure the strength of the void arrangement region 15. The number of reinforcing bars (n) between the voids may be n = 2, or may be n = 4 or more. n = 1 may also be possible.

[0014] As shown in FIG. 1, no void 14 is provided in the solid region 16 in the reinforced concrete 13. As shown in FIGS. 1 and 3, the solid region 16 includes a plurality (for example, three) of solid region portions 16a, 16b, 16c having different thicknesses from each other. In FIG. 3, the illustration of the reinforcing bar 12 is omitted.

[0015] As shown in Figure 1, the solid region 16a is formed, for example, on the outer periphery of the floor slab 2 or near the beam 3. As shown in Figure 3, the thickness t of the solid region 16a 16a The thickness t of the void placement region 15 15 This is equivalent to the above. The upper and lower surfaces of the void arrangement region 15 and the solid region 16a are flush and continuous with each other.

[0016] As shown in Figure 1, the solid region 16b constitutes, for example, the bathroom floor portion 2b of the floor slab 2. As shown in Figure 3, the thickness t of the solid region 16b 16b The thickness t of the void placement region 15 15 and the thickness t of the solid region 16a 16a Equivalent to or lower than that.

[0017] As shown in Figure 1, a solid region 16c (stepped region) is provided between the solid regions 16a and 16b. As shown in Figure 3, the thickness t of the solid region 16c 16c The thickness t of the void placement region 15 15 and the thickness t of the solid region 16a 16a It is larger. An upper surface step 16d is formed between the upper surfaces of the solid regions 16b and 16c. A bottom surface step 16e is formed between the bottom surfaces of the solid regions 16a and 16c.

[0018] This section explains how to evaluate the thermal insulation performance of a real void slab 10. As shown in Figures 4 and 5, first, multiple void slab test specimens 19 are prepared. As shown in Figures 5 and 6, each test specimen 19 contains reinforced concrete 13 and multiple voids 14, similar to an actual void slab. Note that the reinforcement bars 12 are not shown in Figures 5(a) to 5(c).

[0019] As shown in Figure 4, at least measurement area A of the test specimen 19 19 Within the reinforced concrete 13, multiple voids 14 are evenly spaced at the minimum permissible interval d 14minThey are embedded in the ground. As shown in Figure 6, a predetermined number (e.g., n=3) of reinforcing bars 12 are arranged in a row between adjacent voids 14 of the test specimen 19, for example, at the reinforcement height on the upper side.

[0020] As shown in Figure 6, the minimum allowable distance d between two adjacent voids 14 14min This mainly refers to the required spacing distance d between multiple structural reinforcing bars 12 (e.g., n=3) arranged side by side between these voids 14. 12min , and the required separation distance d between each void 14 and the structural reinforcement 12C immediately adjacent to it. 10min It is set based on this.

[0021] Required spacing distance d between reinforcing bars 12min The concrete cover and diameter φ of the reinforcing bar 12 12 , derived from the size of the coarse aggregate in the reinforced concrete 13, preferably d 12min = 25 mm or more, more preferably d 12min = Approximately 25mm to 35mm. Required spacing distance d between void reinforcement bars. 10min This is the required shortest distance from the outer surface 14ea, including the slope of the outer periphery 14e of the void 14, to the outer surface of the nearest structural reinforcement 12C, preferably d 10min =20mm or more, more preferably d 10min It is approximately 20mm to 25mm.

[0022] These required separation distances d 12min d 10min , rebar diameter φ 12 Considering the number of reinforcing bars between voids n (e.g., n=3), the minimum allowable spacing d between the opposing ends of adjacent voids 14 is determined. 14min Preferably d 14min = Approximately 115mm to 135mm, more preferably d 14min It is approximately 125mm.

[0023] As illustrated in Figures 5(a) to 5(c), the total thickness t of multiple test specimens 19 19 (t 19A ,t 19B ,t 19C) are different from each other. Also, the thickness t of the voids 14 in multiple test specimens 19 14 They are different from each other. The thickness t of void 14. 14 The larger the test specimen 19, the greater the total thickness t. 19 The size is large. The total thickness t of each test specimen 19 19 The thickness t of the void 14 in the test specimen 19 14 More preferably, it should be about 100mm to 115mm larger.

[0024] As shown in Figure 7, the thermal transmittance U in the thickness direction (vertical direction in Figure 7) for each of the 19 test specimens prepared is 19 (W / m 2 The measurement of (K) will be taken in the test building 30. The test building 30 is a two-story building, and the first floor is a low-temperature room 31 maintained at a constant low temperature (for example, around 0°C) by an air conditioner 33.

[0025] In the center of the second-floor slab 32 (first-floor ceiling slab) of the test building 30, a rectangular opening 32c is formed, sized to match the test specimen 19.

[0026] The test specimen 19 is placed horizontally within the opening 32c of the second-floor slab 32. The outer perimeter of the test specimen 19 is placed on the step 32d at the edge of the opening 32c, thereby closing the opening 32c with the test specimen 19. A heat-insulating box 34 with an open bottom is placed over the test specimen 19.

[0027] A heater 36 is provided in the insulated box 34, and the inside of the insulated box 34 is an insulated chamber 35. The open bottom of the insulated chamber 35 is closed by the test specimen 19. The portion of the test specimen 19 facing the insulated chamber 35 is the measurement area A. 19 (Dotted line in Figure 4) This represents the area of ​​the heating chamber 35 and thus the measurement area A. 19 The area of ​​this is smaller than the area of ​​the opening 32c.

[0028] The heater 36 maintains the internal temperature of the insulated chamber 35 at, for example, about 20°C. Preferably, the output of the fans 37 and 38 of the heating chamber 35 and the low-temperature chamber 31 is adjusted so that the surface heat transfer resistance on both the upper and lower surfaces of the test specimen 19 is constant. After allowing heat transfer to stabilize sufficiently over several hours to tens of hours, the heat transfer coefficient in the thickness direction of the test specimen 19 is measured using the power supplied to the heater 36 in the steady state. For multiple test specimens 19 (Figures 5(a) to (c)) with different void thicknesses, the thermal transmittance is measured for each specimen to obtain actual test specimen data.

[0029] Preferably, the net measured thermal conductivity λ of each test specimen 19, excluding surface heat transfer on both the upper and lower surfaces. 19 Or the net measured heat transfer coefficient U 19 Determine the net measured heat transfer coefficient λ 19 Or the net measured heat transfer coefficient U 19 This will be used as the actual measurement data for the test specimen. Net measured heat transfer coefficient λ 19 and the net measured heat transfer coefficient U 19 It can be expressed by the following formula. λ 19 =t 19 / (R 19 -R0) (1) U 19 =λ 19 / t 19 =1 / (R 19 -R0) (2) In equations 1 and 2, t 19 This is the thickness of test specimen 19. R 19 This is the reciprocal of the thermal resistance of test specimen 19, i.e., the measured thermal transmittance. R0 is the sum of the surface heat transfer resistance on the upper surface and the surface heat transfer resistance on the lower surface of the test specimen 19, for example, R0 = 0.22(m 2 It is (K) / W.

[0030] Based on the experimental specimen measurement data obtained in this way, the heat transfer coefficient or thermal transmittance in the thickness direction of the void arrangement region 15 in the actual void slab 10 is estimated, and furthermore, the thermal transmittance U in the thickness direction of the entire actual void slab 10 is estimated. 10 Calculate the amount.

[0031] Specifically, when the thickness of the void 14 in the actual void slab 10 is the same as the thickness of the void 14 in any of the test specimens 19, the measured data λ 19 or U 19 of that test specimen 19 is used as the estimated value λ 15 or the estimated value U 15 of the heat transfer coefficient in the thickness direction of the void arrangement region 15 of the actual void slab 10 (λ 19 = λ 15 or U 19 = U 15 ).

[0032] When the thickness of the void 14 in the actual void slab 10 is different from the thickness of the void 14 in any of the test specimens 19, the measured data λ 19 or U 19 of one or more test specimens 19 with a thickness approximating that of the void 14 in the actual void slab 10 is used to estimate the heat transfer coefficient U 15 in the thickness direction of the void arrangement region 15 of the actual void slab 10. An approximate curve or approximate equation showing the correlation between the void thickness and the heat transfer coefficient λ, or the correlation between the void thickness and the heat transfer coefficient U, is obtained from the measured data λ 19 or U 19 of multiple test specimens 19, and the heat transfer coefficient λ 15 or the heat transfer coefficient U 15 in the thickness direction of the void arrangement region 15 of the actual void slab 10 may be estimated from the approximate curve or approximate equation.

[0033] The heat transfer coefficient U 10 in the thickness direction of the entire actual void slab 10 is calculated based on the area ratio r 10 of the void arrangement region 15 to the total area S 15 of the actual void slab 10 and the estimated value λ 15 or the estimated value U 15 of the heat transfer coefficient, as well as the area ratios r 10 of each solid region part 16a, 16b, 16c to the total area S 16a , r 16b , r 16c and the thicknesses t 16a , t 16b , t 16cAnd the calculation is performed based on the thermal conductivity λ0. Specifically, for example, according to the following formula, the heat transfer coefficient U in the thickness direction of the entire solid void slab 10 10 is calculated. U 10 =(r 15 ×(λ 15 / t 15 ))+(r 16a ×(λ0 / t 16a ))+(r 16b ×(λ0 / t 16b ))+(r 16c ×(λ0 / t 16c )) (3) The heat transfer coefficient λ 15 and the heat transfer coefficient U 15 satisfy the following relational expression. U 15 =λ 15 / t 15 (4)

[0034] Let the areas of the void arrangement region 15 and each solid region part 16a, 16b, 16c be S 15 [[ID=##**WARN**##]]The tag ` 16a ` is not closed. ,S 16b ,S 16c respectively. Then, the area ratios r 15 ,r 16a ,r 16b ,r 16c are respectively expressed by the following formulas. r 15 =S 15 / S 10 (5) r 16a =S 16a / S 10 (6) r 16b =S 16b / S 10 (7) r 16c =S 16c / S 10 (8)

[0035] For the heat conductivity λ0 of each solid region part 16a, 16b, 16c, the specified heat conductivity of reinforced concrete (1.6 W / mK) can be applied. That is, λ0 = 1.6 W / mK (9) ​That is the case.

[0036] In this way, it is possible to obtain thermal insulation performance evaluation results that are closer to the actual thermal insulation performance of the actual void slab 10.

[0037] The present invention is not limited to the embodiments described above, and various modifications can be made without departing from its spirit. For example, the number of solid regions with different thicknesses in the solid region 16 of the actual void slab 10 is not limited to three; it may be two, four or more, or any number of solid regions. Depending on the number of solid regions, the thermal transmittance U in the thickness direction of the entire actual void slab 10 is calculated using the following formula. 10 Calculate the amount. U 10 =(r 15 ×(λ 15 / t 15 ))+Σ(r 16x ×(λ0 / t 16x )) (10) Here, r 16x This is the total area S of the actual void slab 10. 10 This is the area ratio of each solid region to t. 16x This represents the thickness of each solid region. [Industrial applicability]

[0038] This invention can be applied, for example, to the construction of floor slabs in reinforced concrete structures. [Explanation of Symbols]

[0039] 1. Reinforced concrete building 10 Real void slab 11 Concrete 12 Structural reinforcement 13 Reinforced concrete 14 Void 15 Void placement area 16. Solid Area 16a, 16b, 16c Solid region 19 Test specimens A 19 measurement area 30 Test Building 31 Cold room 34 Heat insulation box 35 Warming room 36 Heater

Claims

1. Multiple voids are embedded in the reinforced concrete of the measurement area at equal and minimum permissible intervals, and multiple void slab test specimens are prepared, each with a different total thickness and void thickness. The thermal transmittance in the thickness direction within the measurement area is measured for each test specimen to obtain actual test specimen data. A method for evaluating the thermal insulation performance of a void slab, characterized by estimating the thermal conductivity or thermal transmittance in the thickness direction of a void arrangement region in an actual void slab, which is the subject of evaluation, where multiple voids are embedded in reinforced concrete at intervals greater than or equal to the minimum allowable interval, based on the measured data of the test specimen, and calculating the thermal transmittance in the thickness direction of the entire actual void slab.

2. The solid void slab has a void arrangement region and a solid region in which no voids are provided within the reinforced concrete, and the solid region includes a plurality of solid regions with different thicknesses. The method for evaluating thermal insulation performance according to claim 1, wherein the calculation is performed based on the area ratio of the void arrangement region to the total area of ​​the actual void slab and the estimated value of the thermal conductivity or thermal transmittance, and the area ratio, thickness, and thermal conductivity of each solid region to the total area.

3. In the aforementioned test specimen, a predetermined number of structural reinforcements are placed between the main surfaces of adjacent voids in a plan view. The thermal insulation performance evaluation method according to claim 1 or 2, wherein the minimum allowable spacing is set based on the required distance between adjacent structural reinforcements and the required distance between a void and the structural reinforcement closest to it.

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