JP7787401B2 - Panel material - Google Patents

Description

This disclosure relates to panel materials.

Low heat-conductive steel is known as a steel material used in panel materials such as exterior walls and flooring. Low heat-conductive steel can be produced, for example, by drilling one or more holes in the web of a channel steel stud, which acts as a thermal bridge in an exterior wall.

The holes extend the length of the heat transfer path through the web located between the pair of flanges and reduce the cross-sectional area of the transfer path. As a result, the thermal conductivity of the web decreases, improving the insulating performance of low-heat-transfer steel sections that use channel steel with perforated webs. When comparing channel steel sections of the same shape and dimensions, for example, the insulating performance of low-heat-transfer steel sections that use channel steel with perforated webs is better than that of channel steel sections with non-perforated webs.

In this specification, for the sake of convenience, lip channel steel with a perforated web will be referred to as "low heat transfer steel," and lip channel steel with a non-perforated web will be referred to as "normal steel."

As an example of technology related to low heat transfer steel, Patent Document 1 discloses lip channel steel as a frame material used in panel materials such as building wall materials. In the lip channel steel of Patent Document 1, the cross-sectional area of the web when cut at a plane perpendicular to the material axis is reduced by making the cross-sectional area at the center in the web height direction smaller than the cross-sectional area near the flanges at both ends, thereby reducing the thermal conductivity of the web. Patent Document 1 discloses a technique of drilling holes in the plate surface of the web as an example of a method for reducing the cross-sectional area.

Patent Document 2 also discloses low-heat-conductivity steel sections in which the web of a channel steel structural metal plate is cut and raised at the sides, creating slits in the web to reduce thermal conductivity.

Japanese Patent Application Laid-Open No. 2000-87505 Japanese Patent Application Laid-Open No. 2002-146936

Here, in low-heat-conductivity channel steel, the holes drilled in the web act as cross-sectional defects in the web. This improves the insulating performance of the panel material. However, in terms of structural performance, the bending strength of channel steel with perforated webs is lower than that of channel steel with non-perforated webs. In particular, it has been found that low-heat-conductivity lip channel steel with a plate thickness of 2.3 mm or less is prone to distortional buckling, a phenomenon unique to low-heat-conductivity steel, i.e., localized deformation of the web, when bending loads due to wind pressure, etc., are applied to the flanges from the face material joined to the flanges.

In this regard, Patent Document 1 does not disclose any technology for suppressing buckling, which is specific to low-heat-transfer steel, and improving its strength when a bending load is applied to the channel steel. Therefore, the technology in Patent Document 1 alone cannot solve the problem of reduced strength caused by buckling, which is specific to low-heat-transfer steel, such as lip channel steel with a plate thickness of 2.3 mm or less.

Furthermore, while Patent Document 2 is a technology related to low heat transfer steel sections, the inventors' investigations have revealed that even when side walls are provided, it may not necessarily be possible to fully resolve the problem of reduced strength due to buckling, which is unique to lip channel steel sections made of low heat transfer steel sections. Therefore, there is a need for new technology that can suppress the reduction in strength due to buckling in lip channel steel sections made of low heat transfer steel sections.

In light of the above-mentioned problems, the present disclosure aims to provide a panel material that has improved thermal insulation performance by using lip channel steel with a perforated web and a plate thickness of 2.3 mm or less as low heat transfer steel, and that can suppress the reduction in strength due to buckling that is unique to low heat transfer steel.

A panel material according to one embodiment of the present disclosure comprises a lip channel steel having a web, a pair of flanges, and a pair of lips, the web having holes for improving the thermal insulation performance of the channel steel, the lip channel steel having a plate thickness of 2.3 mm or less, and a face material joined to the plate surface of at least one of the flanges, and the length of the lip continuing from the flange to which the face material is joined is equal to or greater than the effective lip length [mm] defined by the formula (240/√F) × t, where F is the F-value [N/ ^mm2 ] of the lip channel steel and t is the plate thickness [mm] of the lip channel steel.

The inventors investigated the length of the lip that connects to the flange to which the face material is joined and that is subjected to compression when an external bending load is applied to the flange to which the face material is joined, in low-heat-conductive steel sections that use lip channel steel with a perforated web and a plate thickness of 2.3 mm or less. As a result of the investigation, it was found that when the lip length is equal to or greater than the effective lip length [mm], the bending stress increases compared to lip channel steel of the same specifications, except that the lip length is the required lip length.

Here, bending stress refers to the distortional buckling strength of the lip channel steel. The formula for defining the effective lip length is the same as the formula for calculating the effective lip width listed in Table 3.4.4 on page 56 of the "Guidelines for the Design of Lightweight Steel Buildings, Second Edition" (Japan Iron and Steel Federation). Furthermore, as a result of the inventors' research, it was found that in the case of non-perforated ordinary steel sections, even if the lip length is extended beyond the effective lip length, the bending stress of the ordinary steel section does not increase compared to the bending stress when the lip length is the required lip length.

For this reason, the panel material according to one embodiment of the present disclosure can suppress the reduction in strength due to buckling, which is unique to low heat transfer steel, in lip channel steel made of low heat transfer steel with improved thermal insulation performance.

Accordingly, this disclosure provides a panel material with improved thermal insulation performance achieved by using lip channel steel with a perforated web and a plate thickness of 2.3 mm or less as low heat transfer steel, and which can suppress the reduction in strength due to buckling that is unique to low heat transfer steel.

FIG. 1 is a perspective view illustrating a panel material according to an embodiment of the present disclosure. FIG. 2(A) is a front view of the outer surface of the web of the lip channel steel of the frame member according to this embodiment, and FIG. 2(B) is a cross-sectional view taken along line 2B-2B in FIG. 2(A). FIG. 10 is a front view of the outer surface of the web when the slit joints are arranged in series. 10 is a graph illustrating the relationship between the slit ratio and the rate of decrease in the coefficient of overall heat transmission, with different slit arrangement patterns. FIG. 2 is a diagram illustrating an outline of an analytical model of a lip channel steel of a low heat transfer steel according to Example 1. Figure 6(A) is a diagram explaining the cross-sectional deformation at the center of the material axis direction of the analysis model according to Example 1, Figure 6(B) is a diagram explaining the cross-sectional deformation at the center of the material axis direction of the analysis model according to the first comparative example, and Figure 6(C) is a diagram explaining the cross-sectional deformation at the center of the material axis direction of the analysis model according to the second comparative example. FIG. 10 is a diagram illustrating the relationship between displacement and load at the center of each of the analysis models of Example 1, the first comparative example, and the second comparative example. 10 is a graph illustrating the relationship between the ratio of effective lip length to short-term bending strength in the analysis model of Example 2. 10 is a graph illustrating the relationship between the ratio of effective lip length to maximum bending strength in the analysis model of Example 2. 10 is a graph illustrating the relationship between the ratio of effective lip length to short-term bending strength in the analysis model of the second comparative example.

Embodiments of the present disclosure are described below. In the following drawings, identical or similar parts are designated by the same or similar reference numerals. However, the relationship between thickness and planar dimensions in the drawings, and the thickness ratios of each device and component, may differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Furthermore, there are parts in which the dimensional relationships and ratios differ between the drawings.

<Panel material>
First, the panel material according to this embodiment will be described with reference to Figures 1 to 4. As shown in Figure 1, the panel material 10 according to this embodiment includes a lip channel steel 12 as a frame material, a face material 14 joined to the upper flange 12B, and a face material 22 joined to the lower flange 12B. A filler member 24 is disposed between the upper face material 14 and the lower face material 22. Note that in Figure 1, portions of the face materials 14 and 22 are illustratively cut away to make the lip channel steel 12 easier to see.

(Lip channel steel)
The lip channel steel 12 has a web 12A, a pair of flanges 12B, and a pair of lips 12C. The lip channel steel 12 can be made from a single steel plate by, for example, bending. In the present disclosure, the steel plate has a thickness of 2.3 mm or less.

In this embodiment, the lip channel steel 12 may be formed using a high-strength steel plate of 500 MPa or more. In this specification, "high-strength steel plate" refers to a steel plate (steel material) having an F-value, as a strength, of 500 MPa or more and 1000 MPa or less. In addition, in contrast to "high-strength steel plate," a steel plate having an F-value of less than 500 MPa may be referred to as "normal steel plate." In this embodiment, for example, a steel material may be used in which the F-value of 400 material as a normal steel plate is 280 MPa and the F-value of a high-strength steel plate is 500 MPa, or a steel material in which the F-value of a high-strength steel plate is 500 MPa may be used.

If the F-value, which indicates the strength of the steel plate, exceeds 1000 MPa, the strength becomes too high, resulting in reduced workability when forming the steel plate into lip channel steel 12, for example, by roll forming. For this reason, in this embodiment, the strength of the high-strength steel plate is specified to be 1000 MPa or less. However, in this disclosure, the strength of the high-strength steel plate is not limited to this and can be changed as appropriate.

(lip)
In the present embodiment, the lip lengths L of the pair of lips 12C are equal to each other, but in the present disclosure, the lip lengths of the pair of lips may be different from each other. The "lip length L" is the maximum length of the lip 12C measured in a cross section perpendicular to the material axis direction D of the lip channel steel 12, as shown in FIG. 2(B) .

Here, in this embodiment, it is assumed that the flange 12B, which is joined to the face material 14, is subjected to an external compressive force, i.e., bending, in the out-of-plane direction of the face material 14.

(Surface material)
As shown in FIG. 1 , the face material 14 is a rectangular building component when viewed from the front. The face material 14 is, for example, a plate-shaped base material or gypsum board. In the present embodiment, the face material 14 is an exterior wall material, but the present disclosure is not limited thereto and may be, for example, another panel material such as a flooring material. Furthermore, while the present embodiment illustrates a case in which the face material is joined to both of the pair of flanges 12B, the present disclosure is not limited thereto and may instead be joined to only the upper flange 12B or only the lower flange 12B in FIG. 1 .

Furthermore, the upper face material 14 and the lower face material 22 in Figure 1 may be members having the same function, or may be members having different functions. The face material 14 only needs to be joined to the plate surface of at least one of the flanges 12B by the joining member 20.

(Filling member)
In the present embodiment, the filler member 24 is a heat insulating material such as glass wool or cellulose fiber, but the present disclosure is not limited to this and can be changed as appropriate. Also, the filler member is not essential in the present disclosure.

(Joining member)
The joining members 20 are, for example, screws or the like, and are architectural components that join the flange 12B and the face material 14. In Fig. 1, when the wall surface of the face material 14 is viewed from the front, multiple joining members 20 are arranged linearly along the material axis direction of the lip channel steel 12. Note that in the present disclosure, the number of rows of joining members 20 can be set as desired, such as one row, two rows, or more.

(web)
As shown in FIG. 2(A), in this embodiment, the web 12A is provided with a row of slits 16 arranged linearly at approximately equal intervals G along the material axis direction D. The slits 16 are holes that improve the thermal insulation performance of the channel steel. Three rows of slits 16 are formed at approximately equal intervals G along the vertical direction in FIG. 2(A). Note that the "material axis direction D" is the direction in which the web 12A and flange 12B of the lip channel steel 12 extend along the left-right direction in FIG. 2(A). In other words, the material axis direction D is equal to the longitudinal direction.

As shown in Figure 2(B), "web height HW" is the linear distance in the vertical direction from the end of one flange 12B to the end of the other flange 12B. Furthermore, "flange width WF" is the linear distance in the horizontal direction from the end of the web 12A to the end of the lip 12C in Figure 2(B). Furthermore, "lip length L" is the linear distance in the vertical direction from the end of one flange 12B of the lip 12C to the end of the other lip 12C in Figure 2(B). For example, the lip length L of the upper lip 12C in Figure 2(B) is the linear distance between the upper surface of the upper end, which is located at the same height as the upper surface of the upper flange 12B, and the lower surface of the lower end of this upper lip 12C.

Furthermore, in the present disclosure, the number of rows containing slits 16 is not limited to three rows, but may be one row, or any number of rows of two or more, such as five rows. From the perspective of improving thermal insulation performance, it is desirable to form three or more rows of slits 16.

In addition, in the present disclosure, the spacing G in the material axis direction D between adjacent slits 16 in one row is not limited to being equal, but may be different. Furthermore, the spacing G between adjacent rows in the web height direction is also not limited to being equal, but may be different. Furthermore, in order to avoid stress concentration, it is preferable that the shape of the longitudinal end of the slit 16 be arc-shaped, as shown in Figure 1.

(joint part)
In this embodiment, a connecting portion 18 is formed in the web 12A at a portion where a gap G in the material axis direction D is formed between adjacent linear slits 16 having a constant length M in a row of the web 12A, connecting the plate members of the web 12A in the height direction.

In the present disclosure, the shape and dimensions of the holes drilled in the web 12A are not limited to slits and can be changed as appropriate. Furthermore, in the present disclosure, the number of slits included in one row can be any number as long as it is two or more. In the present disclosure, it is sufficient that at least one connecting portion is formed, as long as the necessary strength as a component is ensured.

In this embodiment, in a plan view of the front surface of the web 12A, the arrangement pattern of the multiple connecting portions 18 included in the three rows of slits 16 is staggered. Specifically, the slits 16 included in each of the three rows are offset so as not to overlap on a straight line along the web height direction.

In other words, if the slits 16 are staggered, when the plate surface of the web 12A is viewed from the front, the path along which heat moves from one flange 12B side to the other flange 12B side is prevented from being the shortest distance equal to the web height HW. Furthermore, when the slits 16 are staggered, it is possible that the connecting portions 18 will also be staggered.

In addition, in this disclosure, "a state in which the slits are staggered" is not limited to a state in which the slits are staggered in all rows of slits 16 formed in the web 12A. In this disclosure, "a state in which the slits are staggered" can also include a state in which the slits are staggered partially in at least one of the material axis direction D and the web height direction.

Note that in the present disclosure, the arrangement pattern of the multiple slits is not limited to a staggered arrangement. As shown in Figure 3, the slits 16 may also be arranged in series so that they overlap on a straight line along the web height direction (the up-down direction in Figure 3).

(Slit ratio)
In the present disclosure, the slit ratio is defined as the sum of the spacings G between adjacent slits 16 in the material axis direction D of the web 12A divided by the sum of the lengths M of the slits 16. Note that in the present disclosure, the "slit spacing" includes both a spacing formed between two slits and a spacing formed between one slit and the other end of the web in the material axis direction.

(Analysis test of heat transmission coefficient reduction rate)
4 illustrates the heat transmission coefficient reduction rate calculated from the results of analyzing the heat transmission coefficient of panel materials using low heat transfer steel of lip channel steel 12 with different slit ratios using finite element numerical analysis (FEM). Specifically, the heat transmission coefficient reduction rate of an analytical model of lip channel steel 12 in which the joints 18 are arranged in a series pattern and the heat transmission coefficient reduction rate of an analytical model of lip channel steel 12 in which the joints 18 are arranged in a staggered pattern are illustrated.

The lip channel steel 12 used in the two analysis models in Figure 4 have the same shape and dimensions, except for the arrangement pattern of the joints 18. Also, in Figure 4, data points for a staggered arrangement of the joints 18 are illustrated by five black circles, and data points for a serial arrangement of the joints 18 are illustrated by seven white circles.

In analysis test 1, five exterior wall components with different slit ratios were set up as analysis models. Each component was made of low-heat-conductivity lip channel steel 12 (a stud material), with one structural face plate 14, insulation as a filler member 24, and gypsum board as a face plate 22 attached to the other. Specifically, in the shape of the lip channel steel 12 having three rows of slits 16 illustrated in Figure 2(A), the length M and spacing G of the slits 16 were changed to vary the slit ratio. The five joints 18 were all arranged in a staggered pattern. An analysis was then performed using the set analysis models to analyze the respective thermal transmittances.

In addition, a lip channel steel 12 with the same shape and dimensions as the analytical model and a non-perforated web 12A was set as a reference model for comparison. An analysis was then performed on the set reference model to analyze the thermal conductivity of the reference model.

The "Decrease in Heat Transmission Coefficient" on the vertical axis of the graph in Figure 4 is the value obtained by dividing the heat transmission coefficient of the analytical model with slits 16 by the heat transmission coefficient of the reference model. A larger decrease in heat transmission coefficient, i.e., the closer the decrease in heat transmission coefficient is to 1, means that the degree of decrease is small and therefore the thermal insulation performance is not improved. On the other hand, a smaller decrease in heat transmission coefficient means that the degree of decrease is large and therefore the thermal insulation performance is improved.

As can be seen from the data points marked with black circles in Figure 4, when the joints 18 are arranged in a staggered pattern, the reduction in heat transmission coefficient is 85% or less when the slit ratio is 20% or less. In other words, it is possible to improve the insulation performance by 15% or more. On the other hand, when the slit ratio exceeds 20%, the improvement in insulation performance is less than 15%.

Furthermore, from the perspective of thermal insulation performance, a smaller slit ratio is preferable, but if the slit ratio is too small, the strength of the lip channel steel 12 as a structural member, i.e., its structural performance, becomes unstable. For this reason, in this embodiment, the slit ratio is set in the range of 5% or more and 20% or less, which is a range that achieves a good balance between structural performance and thermal insulation performance. Note that in the present disclosure, the slit ratio range is not limited to this and can be changed as appropriate depending on the desired specifications of the lip channel steel 12.

Furthermore, as can be seen from the data points marked with white circles in Figure 4, even when the joints 18 are arranged in series, thermal insulation performance can be effectively improved if the slit ratio is set within the range of 5% or more and 20% or less. However, even with the same slit ratio, the analytical model of lip channel steel 12 with staggered joints 18 has a smaller rate of decrease in thermal transmittance than the analytical model of lip channel steel 12 with serial joints 18, resulting in a greater improvement in thermal insulation performance.

(Lip length)
Next, the lip length L of the lip 12C according to this embodiment will be specifically described. First, in lip channel steel made of ordinary steel, not low heat transfer steel, it is usually sufficient to ensure the required lip length as the lip length L. However, in this embodiment, the lip length L continuing from the flange 12B to which the face plate 14 is joined is set to be longer than the required lip length, i.e., equal to or greater than the effective lip length.

(required lip length)
The required lip length is defined by the following formula based on the description on page 83 of "Guidelines for the Design of Lightweight Steel Buildings, Second Edition" (Japan Iron and Steel Federation).


C _min : Required lip length [mm]
b: Width of flange plate element of lip channel steel etc. [mm]
F: F value of lip channel steel [N/mm ² ]
t: thickness of lip channel steel [mm]

(effective lip length)
The effective lip length is the same as the "effective lip width" described in Table 3.4.4 on page 56 of the "Guidelines for the Design of Lightweight Steel Buildings, Second Edition" (Japan Iron and Steel Federation). Specifically, it is defined by the following formula:

Effective lip length [mm] = (240/√F) × t

The plate thickness t is set in accordance with the design plate thickness described in "(1) Steel Plate Thickness" in the "Guidelines for the Design of Lightweight Steel Buildings, Second Edition," section on page 52, regarding the structural calculation of effective sections. In other words, as a general rule, a plate thickness of 90% of the nominal plate thickness is used.

The arrangement of the effective cross section of the bending member is set in accordance with the arrangement shown in Figure 3.4.5 on page 55 of the "Guidelines for the Design of Lightweight Steel Buildings, Second Edition," and in accordance with the description in "(6) Effective Section Modulus Ze of Bending Members" on page 56. In other words, when calculating the allowable stress of bending members, the arrangement of the effective cross section of the bending member differs depending on whether the flange 12B on the compression side of the lip channel steel 12 subjected to strong axis bending is evaluated with an ineffective portion equivalent to that on the compression side, or whether the entire plate element is considered effective.

Next, Examples 1 and 2, which were carried out on the lip channel steel 12 of the panel material 10 according to this embodiment, in which the lip length L was set to be equal to or greater than the effective lip length, will be described with reference to Figures 5 to 9.

Example 1: Relationship between displacement and load
In Example 1, an analysis was performed using FEM to measure the resistance strength of the lip channel steel 12 to a compressive force acting along the out-of-plane direction. Note that, since bending is the dominant load acting on low heat-transfer steel, it is assumed here that the force acting on the lip channel steel 12 of low heat-transfer steel does not include a compressive force along the material axis direction D, i.e., an axial force.

Specifically, an analytical model was set up as shown in Figure 5. The length in the material axis direction D of the analytical model was 3900 mm, the web height was 100 mm, the flange width WF was 50 mm, and the plate thickness was 1.6 mm. In Example 1, the lip length L was set as one of four parameters: 10 mm, 20 mm, 30 mm, and 40 mm.

In the analysis, it was assumed that the face plate 14 was joined to the upper flange side of the lip channel steel of the analytical model in Figure 5. Furthermore, the lip channel steel was divided into four equal parts in the material axis direction D, and a four-point bending test was performed in which a forced vertical displacement from top to bottom in Figure 7 was set at two points on both ends, applying force to the central part sandwiched between the two central points. Furthermore, displacement of the central part in the flange width direction was restrained to prevent lateral buckling. Furthermore, as a boundary condition, one end of the lip channel steel in the material axis direction D was set to be pin-supported, and the other end was set to be roller-supported.

A load was then applied to each of the set analysis models, and the deformation state at the center in the material axis direction D was analyzed. The bending strength of each model was also measured based on the analysis results. Below, the analysis results for a lip channel steel 12 in which the lip length L is equal to or greater than the effective lip length will be described as Example 1. The analysis results for a lip channel steel 12 in which the lip length L is less than the effective lip length will be described as Comparative Example 1.

In addition, the same analysis and measurements as in Example 1 and Comparative Example 1 were also performed on a regular section steel, which was a lip channel steel having a non-perforated web 12A, as Comparative Example 2. The specifications of the lip channel steel in Comparative Example 2 were the same as those of the lip channel steel 12 in Example 1, except that it was non-perforated and the lip length L was 12 mm.

In Figures 6(A) to 6(C), the cross-sectional shape of the center in the material axis direction D before a compressive force is applied from above is shown by a dashed line, and the state of the cross-sectional shape deflected and deformed downward at the maximum yield strength after a compressive force is applied from above is shown by a solid line. Figure 6(A) illustrates the cross-sectional shape of the analytical model for Example 1, which has a lip length L equal to or greater than the effective lip length. Figure 6(B) illustrates the cross-sectional shape of the analytical model for Comparative Example 1, which has a lip length L less than the effective lip length. Figure 6(C) illustrates the cross-sectional shape of the analytical model for Comparative Example 2 of ordinary steel.

As shown in Figures 6(A) and 6(B), buckling deformation in Example 1 was suppressed more than in the case of the first comparative example. In the analytical model for the second comparative example illustrated in Figure 6(C), although the central portion in the material axis direction D was bent downward, the overall cross-sectional shape was not significantly deformed. As a result, buckling deformation like that in Example 1 and the first comparative example hardly occurred.

Figure 7 also illustrates the relationship between the vertical displacement δy at the center of the material axis direction D and the load P for Example 1, Comparative Example 1, and Comparative Example 2. The low heat-transfer steel with a lip length L of 10 mm illustrated by the dotted line in Figure 7 is the lip channel steel of Comparative Example 1. The low heat-transfer steel with a lip length L of 20 mm illustrated by the dashed-dotted line in Figure 7, the low heat-transfer steel with a lip length L of 30 mm illustrated by the thin solid line, and the low heat-transfer steel with a lip length L of 40 mm illustrated by the thick solid line are the lip channel steel 12 of Example 1. The lip channel steel illustrated by the dashed line in Figure 7 is the lip channel steel of a normal section steel of Comparative Example 2.

As shown in Figure 7, the low heat transfer steel with a lip length L of 20 mm according to Example 1 was able to withstand a maximum load of approximately 85% of the maximum load of normal steel. Furthermore, the maximum load for the low heat transfer steel with a lip length L of 30 mm according to Example 1 and the maximum load for the low heat transfer steel with a lip length L of 40 mm according to Example 1 were both greater than the maximum load for normal steel. It was found that the lip channel steel 12 according to Example 1 was able to suppress a decrease in yield strength due to cross-sectional defects, even when the low heat transfer steel had a perforated web 12A.

Example 2: Relationship between short-term bending strength increase rate and lip length
Next, in Example 2, the short-term bending strength of the lip channel steel 12 when the lip length L was changed was analyzed using the finite strip method (FSM). The specifications of the analytical model were set to be the same as those in Example 1 except for the lip length L. Also, as shown in Fig. 8, in Example 2, the plate thickness of the analytical model was set to three different types: 1.2 mm, 1.6 mm, and 2.3 mm.

The vertical axis of the graph in Figure 8 represents the rate of increase in short-term bending strength. To calculate the rate of increase in short-term bending strength, first calculate the allowable bending stress from the buckling strength calculated by the FSM. Then, multiply the calculated allowable bending stress by the section modulus of the effective cross-sectional area to calculate the short-term bending strength. This value is then divided by the short-term bending strength calculated from an analytical model with an effective lip length. The ratio to the effective lip length, set on the horizontal axis of the graph in Figure 8, is the value obtained by dividing the lip length L by the effective lip length.

As shown in Figure 8, in Example 2, it was found that the rate of increase in short-term bending strength increased as the lip length L increased beyond the effective lip length, regardless of whether the plate thickness t was 1.2 mm, 1.6 mm, or 2.3 mm. In other words, it was found that the low heat transfer steel of the lip channel steel 12 according to this embodiment can achieve the effect of increasing bending strength when the plate thickness t is 1.2 mm or more and 2.3 mm or less.

Furthermore, as shown in Figure 9, a similar effect was also confirmed by analysis using FEM (finite element method). As shown in Figure 9, for plate thicknesses t of 1.2 mm, 1.6 mm, and 2.3 mm, the increase in maximum bending strength increases as the lip length L increases beyond the effective lip length. Therefore, it can be seen that the maximum bending strength can be increased when the plate thickness t of the lip channel steel 12 made of low heat transfer steel is 1.2 mm or more and 2.3 mm or less.

Meanwhile, as shown in Figure 10, a similar analysis of short-term bending strength was performed using an analytical model of ordinary section steel having a perforated web 12A. The analytical model of ordinary section steel in Example 2 illustrated in Figure 10 has the same specifications as the second comparative example described in Example 1. In the case of ordinary section steel in the second comparative example, it was found that the longer the lip length L is than the effective lip length, the smaller the short-term bending strength becomes, in contrast to Example 2.

Specifically, as shown in Figure 10, in ordinary steel sections, when the lip length L is shorter than the effective lip length, the longer the lip length L, the greater the short-term bending strength. However, when the lip length L reaches the effective lip length, the peak strength of the lip channel steel is reached and local buckling occurs. Furthermore, once the lip length L exceeds the effective lip length, it has been confirmed that the longer the lip length L is than the effective lip length, the greater the tendency for the short-term bending strength to decrease. In other words, in the case of ordinary steel sections, there is no need to extend the lip length L beyond the effective lip length.

(Action and effect)
In the low heat transfer steel using the lip channel steel 12 according to this embodiment, the lip length L continuing from the flange 12B, to which the face material 14 is joined and which is subjected to compression, is equal to or greater than the effective lip length. Therefore, in this embodiment, the bending strength is increased compared to a lip channel steel made of low heat transfer steel with the same specifications, except that the lip length L is the required lip length. As a result, the panel material 10 according to this embodiment can suppress the decrease in strength due to buckling, which is unique to low heat transfer steel, in the lip channel steel 12 made of low heat transfer steel with improved thermal insulation performance.

In addition, in this embodiment, the lip lengths L of the pair of lips 12C are equal to each other, so the cross-sectional shape of the lip channel steel 12 is symmetrical compared to when the pair of lip lengths L are different from each other. As a result, the panel material 10 using the lip channel steel 12 is well-balanced as a building component and has excellent design and construction properties.

In addition, in this embodiment, the slit ratio, defined by dividing the sum of the spacing G of the slits 16 in the material axis direction D of the web 12A by the sum of the lengths of the slits 16, is 5% or more and 20% or less. This makes it possible to realize a lip channel steel 12 made of low heat transfer steel with ensured thermal insulation performance.

Furthermore, when the multiple slits 16 are arranged in a staggered pattern, the distance between the joints 18 that form the heat path is longer than when the multiple slits 16 are arranged in series, resulting in higher thermal insulation performance for the panel material 10. This allows for a better balance between structural performance and thermal insulation performance.

In addition, in this embodiment, the low heat transfer steel of the lip channel steel 12 is formed using high-strength steel plate with an F-value of 500 MPa or more. By using high-strength steel plate for the low heat transfer steel, it is possible to achieve a yield strength equal to or greater than that of regular steel plate, even if the plate thickness is thinner than that of regular steel plate.

<Other embodiments>
Although the present disclosure has been described by the above embodiments, this description does not limit the present disclosure, and it should be understood that various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from the present disclosure.

For example, the present disclosure can be constructed by partially combining the configurations shown in Figures 1 to 10. The present disclosure includes various embodiments not described above, and the technical scope of the present disclosure is defined only by the invention-specific matters of the claims that are appropriate from the above description.

10 Panel material 12 Lip channel steel 12A Web 12B Flange 12C Lip 14 Face material 16 Slit 18 Joint 20 Joint member 22 Face material 24 Filler member D Material axis direction G Spacing HW Web height L Lip length M Slit length WF Flange width t Plate thickness δy Displacement

Claims (5)

a lip channel steel having a plate thickness of 2.3 mm or less, the lip channel steel having a web, a pair of flanges , and a pair of lips, the lip channel steel improving the heat insulating performance of the channel steel and having holes in the web that cause local deformation of the web in response to a bending load applied to the flanges ;
a face material joined to the plate surface of at least one of the flanges,
The length of the lip continuing from the flange to which the face material is joined is equal to or greater than the effective lip length [mm] defined by the formula (240/√F) × t, where F is the F-value [N/mm ² ] of the lip channel steel and t is the plate thickness [mm] of the lip channel steel.
Panel material. The pair of lips have equal lengths.
The panel material of claim 1. the hole is a slit,
A slit ratio defined by dividing the sum of the slit intervals in the material axis direction of the web by the sum of the slit lengths is 5% or more and 20% or less.
The panel material according to claim 1 or 2. When the plate surface of the web is viewed from the front, the plurality of slits are arranged in a staggered pattern.
The panel material of claim 3. The lip channel steel is formed using a high-strength steel plate having an F value of 500 MPa or more.
The panel material according to any one of claims 1 to 4.