Calculation method for thermal insulation performance of void slab and design method for void slab

Abstract

To properly calculate heat insulation property of a void slab.SOLUTION: A heat insulation property calculation method for void slab 1 includes: fixing a peripheral part 1C of the void slab 1 having a first principal surface 1A and a second principal surface 1B with a frame member 32; attaching a heating box 34 to a first surface 32A of the frame member 32 so that a first space 36 is formed by the first principal surface 1A of the void slab 1, the frame member 32 and the heating box 34; attaching a cooling chamber 35 to a back surface 32B of the first surface 32A of the frame member 32 so that a second space 37 is formed by the second principal surface 1B of the void slab 1, the frame member 32, and the cooling chamber 35; installing the void slab 1, the frame member 32, the heating box 34, and the cooling chamber 35 in a thermo-hygrostat chamber 39; heating the first space 36 with a heater 38 installed inside the heating box 34; and determining heat transmission coefficient of the void slab 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for calculating the thermal insulation performance of a void slab and a method for designing a void slab. [Background technology]

[0002] Void slabs are sometimes used for the purposes of soundproofing and weight reduction. Patent Document 1 discloses a void slab in which foamed plastic is embedded in a concrete skeleton. Patent Document 2 discloses a void slab in which a form material made of foamed plastic is embedded in a concrete skeleton, with the inside of the form material being hollow. Patent Document 2 also describes that such void slabs have excellent heat insulation properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-168677 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-175196 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the spread of ZEH (Zero Energy House) has been desired to promote energy conservation. To realize ZEH, it is important to improve the thermal insulation performance of houses. Void slabs have superior thermal insulation performance compared to solid concrete slabs because they contain materials (foamed plastic, air, etc.) with lower thermal conductivity than concrete. However, it is currently not possible to properly evaluate the thermal insulation performance of void slabs.

[0005] An object of the present invention is to provide a method for appropriately calculating the thermal insulation performance of a void slab. [Means for solving the problem]

[0006] The method for calculating the thermal insulation performance of a void slab of the present invention is to calculate the thermal insulation performance of a void slab having a first main surface and a second main surface which is the reverse side of the first main surface. This is a method for calculating the thermal insulation performance of a test void slab that simulates the void slab to be designed. Fixing the void slab with a peripheral frame member; Test specimen Attaching the heating box to a first surface of the frame member so that a first space is formed by the first main surface of the void slab, the frame member, and the heating box; Test specimen attaching a cooling chamber to a back surface of the first surface of the frame member such that a second space is formed by the second main surface of the void slab, the frame member, and the cooling chamber; Test specimen placing the void slab, the frame member, the heating box, and the cooling chamber in a constant temperature and humidity room; and heating the first space with a heater installed inside the heating box; Test specimen and determining the thermal conductivity of the void slab. The void slab to be designed has an area where no voids are provided, the void slab of the test specimen is rectangular and has four voids, and when the void slab of the test specimen is divided into three equal areas along one central axis, two voids are located in the areas at both ends of the void slab of the test specimen, and the area where no voids are provided of the void slab to be designed corresponds to the central area of ​​the void slab of the test specimen. [Effects of the Invention]

[0007] According to the present invention, a method for appropriately calculating the thermal insulation performance of a void slab can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a conceptual diagram showing a typical application example of a void slab. [Figure 2] 1 is a conceptual diagram of a test device used to evaluate the thermal insulation performance of a void slab. [Figure 3] FIG. 1 is a conceptual diagram showing an example of a void slab test specimen. DETAILED DESCRIPTION OF THE INVENTION

[0009] Below, we will explain embodiments of a method for calculating the thermal insulation performance of a void slab and a method for designing a void slab with reference to the drawings. In the following explanation and drawings, the extension direction of the main reinforcement bars is referred to as the X direction, the extension direction of the distribution reinforcement bars as the Y direction, and the direction perpendicular to the X and Y directions (vertical direction) as the Z direction. Figure 1(a) is a plan view of a typical void slab, Figure 1(b) is a cross-sectional view taken along line AA in Figure 1(a), and Figure 1(c) is a cross-sectional view taken along line BB in Figure 1(a). A void slab 1 is installed in a rectangular area surrounded by columns 2 and beams 3. The void slab 1 is rectangular with long sides (parallel to the Y direction) and short sides (parallel to the X direction) and contains multiple voids 4 arranged in a grid pattern. The voids 4 are formed from foamed plastic such as bead-processed polystyrene foam, but this is not limited to this as long as it has the strength required for a molding material and a thermal conductivity lower than that of concrete.

[0010] As shown in Figures 1(b) and 1(c), the void 4 is located approximately in the center of the thickness direction (Z direction) of the void slab 1, and the void 4 is surrounded above, below, and on the sides by concrete structures (referred to as the upper portion 5, lower portion 7, and side portion 6, respectively). Main reinforcement 8 and distribution reinforcement 9 are arranged in the upper portion 5 and lower portion 7, respectively. The main reinforcement 8 is arranged parallel to the short sides of the void slab 1 (X direction), and the distribution reinforcement 9 is arranged parallel to the long sides of the void slab 1 (Y direction). Truss reinforcement 10 is arranged in the side portion 6 and lower portion 7. Truss reinforcement 10 is arranged between adjacent voids 4 in the X direction, but not between adjacent voids 4 in the Y direction. Therefore, the spacing between voids 4 is larger in the X direction than in the Y direction. A predetermined spacing is secured between the void 4 and the beam 3 extending in the Y direction so that truss reinforcement 10 can be placed. A gap of at least 1 / 3 of the void slab thickness is secured between the void 4 and the beam 3 extending in the X direction. The void slab 1 is a semi-precast structure. The lower part 7 (including reinforcement) and truss reinforcement 10 of the void slab 1 are fabricated in a factory, and after the void 4 is placed and the remaining reinforcement is arranged on site, the side part 6 and upper part 5 are poured with concrete.

[0011] Thus, in the area where voids 4 exist, void slab 1 has a three-layer structure: upper concrete portion 5, foam plastic void 4, and lower concrete portion 7. Because the thermal conductivity of voids 4 is much lower than that of concrete (for example, the thermal conductivity of concrete is 1.6 W / m·K, while that of bead-type polystyrene foam is 0.043 W / m·K), the thermal conductivity of the area where voids 4 exist is lower than that of solid concrete, providing excellent insulation. However, regardless of the presence or absence of voids 4, the insulation performance (heat transfer coefficient) of void slab 1 has traditionally been evaluated as if voids 4 did not exist. For example, the Japan Housing Performance Evaluation and Labeling Association (JHA) requires that voids 4 be treated as concrete when calculating the heat transfer coefficient.

[0012] For this reason, in conventional housing, especially apartment buildings, even when void slab 1 is used, an insulation layer separate from void slab 1 is often installed, such as by spraying insulation material onto void slab 1. However, the actual insulation performance of void slab 1 is superior to that of a solid concrete slab, and if its inherent insulation performance can be incorporated into the design, it is expected to make a great contribution to the realization of ZEH. Furthermore, it may become unnecessary to install an insulation layer, or the insulation layer may be able to be made thinner, which could lead to cost reductions and improved workability.

[0013] Therefore, in this embodiment, we propose a method for evaluating the thermal insulation performance of a void slab 1 and a design method for the void slab 1 using the same. Figure 2 shows the concept of a test device 31 used to evaluate the thermal insulation performance of the void slab 1. The test method complies with the calibrated hot box method of Japanese Industrial Standards A-1420:1999, "Method for Measuring the Thermal Insulation Properties of Building Components - Calibrated Hot Box Method and Protected Hot Box Method." The main surfaces of the void slab 1, i.e., the two surfaces perpendicular to the thickness direction Z of the void slab 1, are designated as the first main surface 1A and the second main surface 1B (the back surface of the first main surface 1A). First, the peripheral portion 1C of the void slab 1, i.e., the surfaces other than the first main surface 1A and the second main surface 1B, are fixed with a frame member 32. The frame member 32 has an opening 33 to which the void slab 1 is fixed, and the peripheral portion 1C of the void slab 1 is fitted along the inner periphery of the opening 33. The outside of the opening 33 is the frame surface of the frame member 32, and the frame surface is made up of a first surface 32A and a second surface 32B (the back surface of the first surface 32A).

[0014] First, the heating box 34 and the cooling chamber 35 are attached to the frame member 32. The heating box 34 is attached to the first surface 32A of the frame member 32 so that a first space 36 is formed by the first main surface 1A of the void slab 1, the frame member 32, and the heating box 34. Similarly, the cooling chamber 35 is attached to the second surface 32B of the frame member 32 so that a second space 37 is formed by the second main surface 1B of the void slab 1, the frame member 32, and the cooling chamber 35. A heater 38 and an air circulation fan (not shown) are installed inside the heating box 34. A first thermometer T1 is attached to the first main surface 1A of the void slab 1. Similarly, a second thermometer T2 is attached to the second main surface 1B. The first and second thermometers T1 and T2 are attached to the same positions on the first main surface 1A and the second main surface 1B. A third thermometer T3 is attached near the first thermometer T1 inside the heating box 34. Similarly, a fourth thermometer T4 is attached near the second thermometer T2 inside the cooling chamber 35. Nine or more of each of the first to fourth thermometers T1 to T4 are provided, for example, in a 3 x 3 grid pattern, but only one of each is shown in Figure 2. A fifth thermometer T5 and a sixth thermometer T6 are attached to the inner surfaces of the heating box 34 and the cooling chamber 35, respectively. Multiple fifth thermometers T5 and multiple sixth thermometers T6 can also be provided. The first and second thermometers T1 and T2 measure the surface temperature of the void slab 1, the third and fourth thermometers T3 and T4 measure the air temperature near the surface of the void slab 1, and the fifth and sixth thermometers T5 and T6 measure the surface temperatures of the inner walls of the heating box 34 and the cooling chamber 35, respectively.

[0015] Next, the void slab 1, frame member 32, heating box 34, and cooling chamber 35 are placed in a constant temperature and humidity room 39, and the first space 36 is heated by a heater 38. From the measured values ​​of the thermometers T1 to T6, the heat reflux rate U of the void slab 1 (hereinafter also referred to as the test piece) is calculated as follows: U=φ I / A(T ni -T ne ) where φ I =φ P -φ3-φ4 φ Pis the amount of heat supplied to the heating box 34 (the amount of heat of the heater 38) φ3 is the heat loss from the peripheral wall of the heating box 34 φ4 is the heat loss on the side of the test piece φ3 and φ4 are determined in advance using a calibration plate with the same thermal resistance and thickness as the test piece. A is the heat transfer area of ​​the test piece (the plane area of ​​the void slab 1), T ni is the environmental temperature on the heated side (first space 36 side) of the test specimen, T ne is the ambient temperature on the cooling side of the test specimen (the second space 37 side). The ambient temperature is determined using the measurements from the first to sixth thermometers T1 to T6 in accordance with "Appendix A (Regulations) Heat Transfer at Surfaces and Ambient Temperature" of the Japanese Industrial Standard A-1420:1999 "Method for Measuring the Thermal Insulation of Building Components - Calibrated Hot Box Method and Protected Hot Box Method." The measurements from the first to fourth thermometers T1 to T4 are used as a weighted average based on the area of ​​each thermometer's control area (usually a rectangular area passing through the midpoint between adjacent thermometers).

[0016] It is preferable to create a test specimen with worse thermal insulation performance (higher heat transfer coefficient) than the actual Void Slab 1. The main factors that affect the thermal insulation performance of Void Slab 1 are the void area ratio (the ratio of the total planar area of ​​voids 4 to the heat transfer area A of the test specimen) and the void thickness (Z-direction dimension). These may take on various values ​​when applied to an actual building. Therefore, by setting the void area ratio and void thickness of the test specimen smaller than the void area ratio and void thickness predicted for application, testing is not necessary when applying the test specimen. In other words, if the void area ratio and void thickness of the test specimen Void Slab 1 are smaller than the void area ratio and void thickness of the design target Void Slab 1, the heat transfer coefficient determined for the test specimen can be used to evaluate the thermal insulation performance of the design target Void Slab 1.

[0017] Figure 3(a) shows a plan view of a void slab 1, an example of a test specimen. Figure 3(b) shows a cross-section along line AA in Figure 3(a). Figure 3(c) shows a cross-section along line BB in Figure 3(a). The void slab 1 is rectangular and contains four voids 4. Two voids 4 are located at both ends of the long side. In other words, when the void slab 1 is divided into three equal parts A1 to A3 along the long axis (Y axis), two voids 4 are located in the two end regions A1 and A3. The void slab 1 may also be square, but in this case, the central axis of one of the voids is used as the long axis. Because the void slab 1 of the test specimen is roughly equivalent to replacing the voids 4 in the central region A2 with concrete, the void area ratio is significantly smaller than that of the typical void slab 1 shown in Figure 1.

[0018] In particular, not installing void 4 in the longitudinal center allows for evaluation based on the actual floor slab configuration. The reason for this is as follows: Actual floor slabs have areas where voids cannot be installed, such as the sleeve installation area, the beam edge, and slab step areas. Solid concrete slabs are installed in these areas. Figure 1 shows an example of area 11, which is a concrete slab for installing sleeves. Because the test specimen simulates only a portion of the actual floor slab, it is desirable for the test specimen to have thermal insulation performance equivalent to or lower than the area with the lowest thermal insulation performance in the actual floor slab. By imagining an imaginary area 12 located in the Y-axis center of area 11 and aligning the shape of the test specimen to this area 12, we can more accurately simulate the void-defect areas in the actual floor slab and enable maintenance evaluation from the perspective of thermal insulation performance. In other words, area A2 in Figure 3 can be said to faithfully simulate the area without voids based on the actual floor slab. Furthermore, since the missing portion of the void 4 is located at the center in the Y direction, the same void can be used for the four voids 4, and the fabrication of the test specimen is easy.

[0019] Table 1 shows the specifications and thermal conductivity of the test specimen Void Slab 1. i is the thermal conductivity U of the concrete part C1 (see Figure 3(b)) iaThe thermal conductivity U of the hollow part C2 (see Figure 3(b)) which has a three-layer structure of void 4 and concrete ib Since it is a weighted average according to the area ratio of U i =U ia +U ib = 1.6 × 0.6 + 0.98 × 0.4 = 1.35 (W / m 2 ·K). The thermal conductivity of a plain concrete slab without voids is 1.6 (W / m 2 void area ratio is greater than 40% and the void thickness is greater than 100 mm, the thermal transmittance U i is 1.35 (W / m 2 ·K), but by using this conservative value, there is no need to measure the thermal conductivity using void slab 1 each time.

[0020] [Table 1]

[0021] As explained above, this embodiment makes it possible to incorporate the thermal insulation performance of void slabs, which has not been evaluated until now, into the design. This eliminates the need for additional construction work such as spraying thermal insulation material. Furthermore, even if a material with higher thermal insulation performance is used as the void material, by evaluating it according to this embodiment, it becomes possible to incorporate that thermal insulation performance into the design. [Explanation of symbols]

[0022] 1. Void Slab 1A First principal surface 1B Second main surface 1C Periphery 31 Test equipment 32 Frame members 32A First Side 32B Second Side 34 Heating box 36 First Space 35 Cooling chamber 37 Second Space 39 Constant temperature and humidity room

Claims

1. A method for calculating the thermal insulation performance of a void slab of a test specimen simulating a void slab to be designed, the test specimen having a first main surface and a second main surface that is the back side of the first main surface, Fixing the peripheral portion of the void slab of the test specimen with a frame member; Attaching the heating box to a first surface of the frame member so that a first space is formed by the first main surface of the void slab of the test specimen, the frame member, and the heating box; Attaching the cooling chamber to a rear surface of the first surface of the frame member so that a second space is formed by the second main surface of the void slab of the test specimen, the frame member, and the cooling chamber; placing the void slab of the test specimen, the frame member, the heating box, and the cooling chamber in a constant temperature and humidity room; heating the first space with a heater installed inside the heating box; and determining the thermal transmittance of the void slab of the test specimen; A method for calculating the insulation performance of a void slab, wherein the void slab to be designed has an area where no voids are provided, the void slab of the test specimen is rectangular, the void slab of the test specimen has four voids, when the void slab of the test specimen is divided into three equal areas along one central axis, two of the voids are located in the areas at both ends of the void slab of the test specimen, and the area where no voids are provided of the void slab to be designed corresponds to the area in the center of the void slab of the test specimen.

2. Measuring the thermal transmittance of the void slab of the test specimen by the thermal insulation performance calculation method according to claim 1; Evaluating the thermal insulation performance of the void slab to be designed based on the measured heat transmittance; and A void slab design method, wherein the void slab to be designed has a larger void area ratio and void thickness than the void slab of the test specimen.

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