Fastening structure for fireproof covering material in exterior wall panel

Abstract

A stiffener (30) extending in the vertical direction is embedded in a rear surface (2a) near both side edges of a concrete panel (2) such that a part of the stiffener protrudes to the indoor side. A felt mat-like fireproof covering material (70) superimposed on the indoor side is fastened to the rear surface (2a) of the concrete panel (2) by fasteners (9) composed of a concrete screw and a washer. The fasteners (9) are respectively arranged at a predetermined pitch in vertical rows closer to the end edge side than the stiffener (30) and closer to the center side than the stiffener (30). The fasteners (9) in each row are arranged in a zigzag manner with the left and right heights thereof being different from each other. As a result, hot air flowing into the joints from the outdoor side is prevented from flowing into a ventilation space beyond the stiffeners (30) while ensuring an appropriate ventilation space between the left and right stiffeners (30).

Description

Retention structure of fire-resistant coating material on outer wall panel

[0001] The invention disclosed in the present application relates to a retention structure of a fiber-based fire-resistant coating material on an outer wall panel formed by laminating the fiber-based fire-resistant coating material on the back surface of a plate-shaped concrete panel.

[0002] In a building using a plate-shaped concrete panel as an outer wall material, in order to improve the fire resistance of the outer wall portion, the applicant has invented an outer wall panel in which a fiber-based fire-resistant coating material made of rock wool or glass wool is laminated on the back surface of the concrete panel and disclosed it in Patent Document 1.

[0003] FIGS. 1 to 4 show an embodiment in which the outer wall panel described in the document is used as a curtain wall outer wall material of a steel frame building. The exemplary outer wall panel 1 includes a plate-shaped concrete panel 2, a hat-shaped steel 3 embedded in the concrete panel 2 and partially exposed on the indoor side, an insert nut 4 disposed at an appropriate position in the groove of the hat-shaped steel 3 and embedded in the concrete panel 2, a locking fitting 5 bolted to the insert nut 4 from the indoor side of the hat-shaped steel 3 to lock the outer wall panel 1 to the steel frame beam member X, a fire-resistant coating material 7 covering the back surface 2a of the concrete panel 2 and the exposed portion of the hat-shaped steel 3, and a fixing fitting 8 for fixing the fire-resistant coating material 7 to the hat-shaped steel 3.

[0004] The hat-shaped steel 3 is a stiffening member for reinforcing the rigidity of the concrete panel 2. The hat-shaped steel 3 is arranged at the vicinity of the left and right edges of one concrete panel 2 so as to extend vertically over the entire height of the concrete panel 2. The horizontal distance from the left and right edges of the concrete panel 2 to the centroid of each hat-shaped steel 3 is set to about 100 mm to 150 mm. The hat-shaped steel 3 has a groove in which a bottom plate 31 and a pair of left and right side plates 32 open in a U-shape toward the outdoor side, and a shape in which fin plates 33 project outward from the outdoor side edges of both side plates 32. The fin plates 33 and the middle portions of both side plates 32 are embedded in the concrete panel, and the bottom plate 31 projects inward on the indoor side at a distance of about 15 mm to 18 mm from the back surface 2a of the concrete panel 2.

[0005] The fire-resistant covering material 7 is fastened to the hat-shaped steel 3 with bolts 6 after fastening the locking fittings 5 ​​to the hat-shaped steel 3, and then attached to the bottom plate 31 of the hat-shaped steel 3 so as to cover almost the entire back surface (the dotted area in Figure 2), excluding the upper and lower ends of the exterior wall panel 1. The material of the fire-resistant covering material 7 is rock wool, which has excellent fire resistance, or glass wool, which has excellent heat insulation, and is formed into a felt mat shape with appropriate flexibility. The thickness of the fire-resistant covering material 7 varies depending on the required performance and the part in which it is used, but for example, to ensure 1 hour of fire resistance, a concrete panel 2 with a plate thickness of 55 mm can be covered with 20 mm thick rock wool.

[0006] The fixing bracket 8 is a fitting for fixing the fire-resistant coating material 7 to the bottom plate 31 from the indoor side. The fixing bracket 8 shown in Figure 4 is composed of a retaining bracket 81 that is wider than the bottom plate 31 of the hat-shaped steel 3, and screws 82 for fixing the retaining bracket 81 to the bottom plate 31. The retaining bracket 81 has a rectangular plate portion 81a in front view, and a roughly trapezoidal retaining portion 81c in side view that protrudes from near both ends of the longitudinal edge 81b of the plate portion 81a in a direction perpendicular to the plate portion 81a and holds down the fire-resistant coating material 7. The distance C between the retaining portions 81c is set to a dimension that allows it to straddle the covered portion when the hat-shaped steel 3 exposed to the indoor side is covered with the fire-resistant coating material 7. A screw hole 81d is formed in the center of the plate portion 81a, and four openings 81e are formed around it. These openings 81e have the effect of mitigating the heat generated by the retaining bracket 81 in the event of a fire.

[0007] By adopting such exterior wall panels 1 as the exterior wall material, it is possible to improve the fire resistance of the exterior wall portion with a simple construction method while reducing the thickness and weight of the concrete panels 2.

[0008] Japanese Patent Publication No. 2022-115268

[0009] In the conventional exterior wall panel 1, the concrete panel 2 and the fire-resistant coating material 7 are not in close contact over the entire surface, but are configured to have an appropriate gap between them, which can be used as a ventilation space within the wall. In a typical single-panel fire-resistant wall, in order to prevent flames and heat from spreading from the lower floors to the upper floors, it is necessary to partition the space between the beams and exterior wall materials between floors with mortar or the like, and to install ventilation grilles for ventilation within the wall in the exterior wall material of each floor. However, by connecting the aforementioned ventilation space between the upper and lower floors, it becomes possible to omit the ventilation grilles that would otherwise be installed in the exterior wall of the lower floors.

[0010] However, improving ventilation between the concrete panel 2 and the fire-resistant coating material 7 makes it easier for hot air to enter during a fire, so measures to prevent this are necessary. In particular, the joints where the concrete panels 2 are adjacent to each other have lower heat-shielding performance than the central part of the concrete panel 2, making them weak points where hot air from the outside can easily enter. If the hot air that enters the back side of the concrete panel 2 from these joints wraps around the indoor side of the stiffening material (hat-shaped steel 3) and flows into the central side of the concrete panel 2 (the ventilation space between the left and right stiffening materials), the hot air may rapidly rise to the upper floors due to the chimney effect, and the entire exterior wall may become hot in a short time.

[0011] To ensure adequate ventilation space between the left and right stiffeners while preventing hot air entering through the joints from flowing over the stiffeners into the central ventilation space, one could consider, for example, narrowing the spacing between the aforementioned fixing brackets 8. However, increasing the number of fixing brackets 8 with special shapes like those exemplified would increase material costs and construction labor, which is undesirable.

[0012] The invention disclosed herein was conceived in view of the above circumstances, and provides a fire-resistant coating fastening structure that is cheaper and easier to install than conventional structures, which can secure an appropriate ventilation space between the left and right stiffeners attached to the exterior wall panel, while effectively preventing hot air that has flowed into the joint from the outside side from flowing over the stiffeners into the ventilation space.

[0013] To achieve the aforementioned objective, the fire-resistant covering material fastening structure for an exterior wall panel of the present invention disclosed herein comprises: a concrete panel erected in the exterior wall portion of a building; a pair of left and right stiffeners embedded near both side edges of the concrete panel, each having a portion protruding more inward than the back surface of the concrete panel, and extending vertically over the entire height of the concrete panel; and a felt mat-like fire-resistant covering material covering the back surface of the concrete panel and the protruding portions of both stiffeners from the indoor side, wherein the fire-resistant covering material is fastened to the back surface of the concrete panel from the indoor side using fasteners. The fire-resistant covering material, which is superimposed on substantially the entire surface of the concrete panel except for predetermined areas near the upper and lower edges, is fastened to the concrete panel so as to straddle the stiffeners by fasteners arranged in a vertical line at predetermined intervals on the edge side of the concrete panel relative to each stiffener, and by fasteners arranged in a vertical line at predetermined intervals on the central side of the concrete panel relative to each stiffener. The fasteners fastened on the edge side and the fasteners fastened on the central side are arranged at different heights from each other, so that at least one fastener on one side is positioned within the adjacent height spacing of one fastener.

[0014] In the fastening structure for the fire-resistant coating material in the exterior wall panel relating to the basic configuration described above, it is more preferable that the back surface of the concrete panel is covered with one or more pieces of the fire-resistant coating material cut to the full width of the concrete panel.

[0015] Furthermore, the fire-resistant coating material fastening structure for the exterior wall panel of the present invention employs an additional configuration in which, at locations where two concrete panels are adjacent with a joint in between, a fire-resistant coating material for the back of the joint is superimposed between the stiffening members of the two adjacent concrete panels.

[0016] In this case, it is more preferable that the fire-resistant coating material for the back of the joint and the fire-resistant coating material covering substantially the entire surface of the concrete panel are overlapped in such a way that their respective joint positions do not coincide with each other.

[0017] As described above, the fastening structure for fire-resistant coatings in exterior wall panels allows for an inexpensive and simple construction method, while ensuring adequate ventilation space between the left and right stiffeners, and effectively preventing hot air flowing from the outside into the joints where the exterior wall panels are adjacent to each other, over the stiffeners, and into that ventilation space.

[0018] This is a partially omitted longitudinal cross-sectional view showing the exterior wall panel described in Patent Document 1, which is the background art of the invention disclosed in this application, installed on a steel-framed building. This is an elevation view of the exterior wall panel in Figure 1, viewed from the back side (indoor side). This is a partially omitted transverse cross-sectional view showing an enlarged view of the area near the stiffener in the section along line A-A in Figure 2. This is a perspective view of the fastening hardware used in the exterior wall panel described in Patent Document 1. This is an elevation view showing the arrangement of fasteners in the exterior wall panel according to an embodiment of the invention disclosed in this application, viewed from the back side (indoor side). This is a partially enlarged transverse cross-sectional view showing the overlapping state of the fire-resistant coating material in the area near the joint in the section along line B-B of the exterior wall panel in Figure 5. This is an elevation view showing another example of the arrangement of fasteners. This is a partially enlarged transverse cross-sectional view showing another example of the overlapping state of the fire-resistant coating material near the joint. This is a partially enlarged transverse cross-sectional view showing yet another example of the overlapping state of the fire-resistant coating material near the joint.

[0019] Preferred embodiments of the invention disclosed in this application will be described below with reference to the drawings. In the embodiments described below, components that are substantially the same as those of the conventional exterior wall panel 1 shown in Figures 1 to 4 will be denoted by the same reference numerals, and their descriptions will be simplified.

[0020] Figures 5 and 6 show an example of an exterior wall panel 10 to which the invention disclosed in this application is applied. Similar to the exterior wall panel 1 described in Patent Document 1 shown in Figures 1 to 4, this exterior wall panel 10 is composed of a plate-shaped concrete panel 2, a stiffening member 30 embedded in the concrete panel 2 with a portion exposed on the indoor side, a locking fitting 5 connected to the stiffening member 30, and a fire-resistant covering material 70 that covers the back surface 2a of the concrete panel 2 and the exposed portion of the stiffening member 30.

[0021] The stiffening member 30 can be a hat-shaped steel 3 similar to the exterior wall panel 1 described in Patent Document 1, but in the exemplary embodiment, a channel steel with a U-shaped cross-section is used. The channel steel is integrated with the concrete panel 2 by welding a pair of left and right side plates 32 to a mesh panel 34 placed inside the concrete panel 2, and by having the bottom plate 31 protrude further inward than the back surface 2a of the concrete panel 2. Locking fittings 5 ​​are attached to appropriate locations near the upper and lower ends of the stiffening member 30, and these locking fittings 5 ​​are locked to an exterior wall mounting rail connected to a steel beam member X (see Figure 1).

[0022] As the fire-resistant coating material 70, a fibrous coating material identical or similar to the fire-resistant coating material 7 used in the exterior wall panel 1 described in Patent Document 1 can be used. The fire-resistant coating material 70 in the exemplary form is assumed to be a long roll type material in which rock wool is formed into a felt mat and a high-density nonwoven fabric is attached to one side thereof. The fire-resistant coating material 70 is cut from the long roll so that the length of one sheet extends to the full width of the concrete panel 2, and the cut length is overlapped on the back surface 2a of the concrete panel 2 in the width direction of the concrete panel 2. In other words, it is basically desirable not to overlap the fire-resistant coating material 70 in the width direction of the concrete panel 2.

[0023] Then, multiple fire-resistant covering materials 70 are joined together seamlessly along the height direction of the concrete panel 2, covering almost the entire surface (between the upper and lower locking fittings 5 ​​in the example configuration: the thin dotted area in Figure 5), excluding predetermined areas near the upper and lower edges of the concrete panel 2. If the total height of the concrete panel 2 is approximately 3 m and the roll width (working width) of the fire-resistant covering material 70 is 900 mm to 1000 mm, then three fire-resistant covering materials 70 will be joined together in the height direction on one concrete panel 2. The upper and lower edges of the joined fire-resistant covering materials 70 are joined together, for example, by tape adhesion.

[0024] If the roll width of the fire-resistant coating material 70 is greater than the width of the concrete panel 2, the fire-resistant coating material 70 may be cut to match the height of the concrete panel 2, so that one sheet covers almost the entire back surface 2a of the concrete panel 2.

[0025] In this exterior wall panel 10, the fire-resistant coating material 70 is not fixed to the stiffener 30 by fixing brackets 8 as shown in Figure 4, but rather is fastened to the back surface 2a of the concrete panel 2 using fasteners 9 consisting of concrete screws 91 and washers 92, for example. The essential part of the invention disclosed in this application lies in the arrangement of the fasteners 9. The fastening positions of the fasteners 9 are indicated by white circles in Figure 5.

[0026] The fire-resistant covering material 70 is fastened to the concrete panel 2 so as to straddle the stiffener 30 by a plurality of fasteners 9 arranged in a vertical line at predetermined intervals on the outside of the stiffener 30 (on the edge side of the concrete panel 2) and a plurality of fasteners 9 arranged in a vertical line at predetermined intervals on the inside of the stiffener 30 (on the center side of the concrete panel 2). In other words, the fasteners 9 are arranged in a vertical line on both the left and right sides of the stiffener 30, along the length direction of the stiffener 30. At this time, a feature of this invention is that the fasteners 9 fastened on the edge side of the concrete panel 2 and the fasteners 9 fastened on the center side of the concrete panel 2 are arranged in a zigzag or staggered pattern with different heights on the left and right sides.

[0027] When the step difference between the back surface 2a of the concrete panel 2 and the bottom plate 31 of the stiffener 30 is about 15 mm to 18 mm, and the horizontal distance from the edge of the concrete panel 2 to the center of the stiffener 30 is about 100 mm to 150 mm, it is preferable that the separation dimension D1 (see Figure 6) between the placement line of the fastener 9 and the side plate 32 of the stiffener 30 is set to about 30 mm to 60 mm on the edge side of the concrete panel 2 relative to the stiffener 30. In the example embodiment, each fire-resistant covering material 70 is fastened at a total of three locations: one near the upper edge, one near the lower edge, and one in between. In this case, the vertical spacing P between adjacent fasteners 9 is about 400 mm to 450 mm.

[0028] On the central side of the concrete panel 2 relative to the stiffener 30, it is preferable that the distance D2 (see Figure 6) between the placement line of the fastener 9 and the stiffener 30 is set to be approximately the same as, or slightly larger than, the distance D1 between the placement line of the fastener 9 and the stiffener 30 on the edge side as described above. In the example embodiment, the fastener 9 on the central side of the stiffener 30 is fastened at two points at the midpoint height of the three fastening positions of the fastener 9 on the edge side. In this case, the vertical spacing Q between adjacent fasteners 9 is approximately 400 mm to 450 mm, the same as P, and the distance R from that position to the upper or lower edge of the fire-resistant coating material 70 is approximately 230 mm to 300 mm.

[0029] Further towards the center of the concrete panel 2, no additional fastening is generally performed. As a result, a ventilation space S (see Figure 6) is formed between the fasteners 9, which are arranged in a row on the central side of the left and right stiffeners 30, allowing the fire-resistant coating material 70 to be appropriately separated from the back surface 2a of the concrete panel 2. In addition, to facilitate the formation of the ventilation space S, a suitable spacer may be inserted between the back surface 2a on the central side of the concrete panel 2 and the fire-resistant coating material 7.

[0030] By adopting this arrangement of fasteners 9, the lifting of the fire-resistant coating material 70 on both the left and right sides of the stiffener 30 is suppressed almost uniformly along the length of the stiffener 30, improving the adhesion of the fire-resistant coating material 70 to the concrete panel 2 and the stiffener 30. As a result, hot air that flows into the back surface 2a side of the concrete panel 2 from the joints where the concrete panels 2 are adjacent to each other is blocked by the stiffener 30 and does not flow into the ventilation space S formed on the central side of the stiffener 30.

[0031] By further narrowing the vertical spacing between adjacent fasteners 9, or by aligning the height of each fastener on the edge side and the center side, the number of fasteners 9 can be increased, thereby improving the adhesion of the fire-resistant coating material 70 to the portion spanning the stiffening material 30. However, increasing the number of fasteners 9 also increases the labor involved in construction. Therefore, as shown in the example, by arranging the fasteners 9 in a zigzag or staggered pattern on both sides of the stiffening material 30, it is possible to minimize the number of fasteners 9 and significantly reduce the labor involved in construction while ensuring a practically sufficient level of heat shielding effect.

[0032] Figure 7 shows another example of the arrangement of the fasteners 9. On the edge side of the concrete panel 2 relative to the stiffener 30, the arrangement is the same as shown in Figure 5, and the vertical spacing P of the fasteners 9 is approximately 400 mm to 450 mm. On the other hand, on the central side of the concrete panel 2 relative to the stiffener 30, the fasteners 9 are placed at four locations that divide the height of each fire-resistant covering material 70 into five equal parts. In this case, the vertical spacing T of the central fasteners 9 is approximately 180 mm to 200 mm, so that two central fasteners 9 are placed within the vertical spacing of the edge fasteners 9. Thus, the spacing of the fasteners 9 placed on the edge side of the concrete panel 2 relative to the stiffener 30 may be different from the spacing of the fasteners 9 placed on the central side of the concrete panel 2 relative to the stiffener 30, and the density relationship between them may also be reversed. Furthermore, it is preferable to fasten the fire-resistant coating material 70 at the edges of the concrete panel 2, including the areas near the corners of the upper and lower edges, as this makes it less likely for the corners of the fire-resistant coating material 70 to peel or lift up.

[0033] In the fire-resistant coating fastening structure disclosed in this application, the aforementioned configuration in which a plurality of fasteners 9 are fastened in a vertical row on both the left and right sides of the stiffening member 30, with their heights differing from each other, and are "arranged in a zigzag or staggered pattern," also includes the configuration shown in Figure 7, in which at least one fastener 9 on one side is positioned within the height-direction adjacent spacing of fasteners 9 on the other side. In practical terms, it is preferable to have about 1 to 3 fasteners for balance. In this case, one side and the other side are not fixed over the entire length of a single stiffening member 30. For example, as in the upper and lower joints of the fire-resistant coating 70 in the configurations shown in Figures 5 and 7, the adjacent spacing and height relationship of the left and right fasteners 9 may be reversed in the middle of the length of the stiffening member 30. Furthermore, the arrangement of the fasteners 9 may differ between the left and right edges of a single concrete panel 2, or between the left and right edges of adjacent concrete panels separated by a joint.

[0034] Furthermore, the fire-resistant coating fastening structure disclosed in this application employs a configuration in which a fire-resistant coating 71 for the back of the joint is applied between the stiffeners 30 of the two adjacent concrete panels 2 that are separated by a joint M, in order to reliably prevent the inflow of hot air from the joint between the concrete panels 2. The fire-resistant coating 71 for the back of the joint can be the same material as the aforementioned fire-resistant coating 70 that covers substantially the entire back surface 2a of the concrete panel 2, but it is preferable to use a slightly thinner material (about 20 mm) so that it fits easily into the recess on the back of the joint surrounded by the step difference between the concrete panel 2 and the stiffener 30.

[0035] In the configuration shown in Figure 6, for each of two adjacent concrete panels 2, a fire-resistant coating material 71 for the back of the joint, cut to a width that extends to the center of the joint M, is superimposed on the edge side of the concrete panel 2 beyond the stiffener 30 and temporarily fixed in place beforehand using adhesive or double-sided tape. When these concrete panels 2 are erected adjacent to each other with the joint M in between, the side edges of the fire-resistant coating material 71 for the back of the joint on the left and right are butted together along the joint M, sealing the back of the joint. A fire-resistant coating material 70 that covers almost the entire surface of the concrete panel 2 is superimposed on the indoor side and fastened together as a single unit of two layers with fasteners 9. At this time, it is desirable to offset the joint positions (the positions where the side edges abut) of the fire-resistant coating material 70 that covers almost the entire surface of the concrete panel 2 and the joint positions (same as above) of the fire-resistant coating material 71 for the back of the joint from left to right so that they do not coincide.

[0036] Similarly, when multiple fire-resistant coatings 71 for the back of the joints are joined together along the height of the concrete panel 2, it is desirable to position them so that the joint positions do not coincide with the joint positions of the fire-resistant coatings 70 that cover almost the entire surface of the concrete panel 2, by offsetting them vertically. These considerations can further improve the effect of preventing hot air from entering through the joints M.

[0037] Furthermore, as shown in Figure 8, the fire-resistant covering material 71 for the back of the joint may be cut to a width that matches the distance between the stiffeners 30 of two adjacent concrete panels 2, and then applied to seamlessly cover the space between the two stiffeners 30, straddling the joint M.

[0038] Furthermore, as shown in Figure 9, a fire-resistant covering material 70 cut to a width sufficiently larger than the distance between the stiffeners 30 of two adjacent concrete panels 2 can be prepared and overlapped with the fire-resistant covering material 71 for the back of the joint so as to straddle both stiffeners 30, thereby preventing the joints of the fire-resistant covering material 70 from being joined near the joints M. This fire-resistant covering material 70 may extend to an area not shown in the width direction of the concrete panel 2, but in the example embodiment, another fire-resistant covering material 72 covering the central side of the concrete panel 2 is overlapped and fastened with fasteners 9 near the edge of the fire-resistant covering material 70 that straddles the stiffeners 30, on the central side of the concrete panel 2 than each stiffener 30. In this embodiment, a ventilation space S is formed between the fire-resistant covering material 72 overlapped on the central side and the back surface 2a of the concrete panel 2. For example, even if the width of the concrete panel 2 is large, the fire-resistant coating material 70, 72 may be spliced ​​together in the middle section in the width direction, and the invention disclosed in this application also includes such forms.

[0039] The fastener 9 is not limited to the combination of concrete screw 91 and washer 92 as illustrated. For example, it is also possible to use a fastener with the following configuration: a thumbtack-shaped insertion member is prepared, comprising a flat base plate of an appropriate shape and a puncture pin protruding perpendicular to the surface of the base plate from its center; the base plate is bonded to a predetermined position on the concrete panel; a fire-resistant coating material 70 is pressed against the puncture pin protruding inward; and a retaining cap, which also serves to protect the tip of the puncture pin that has penetrated the fire-resistant coating material, is fitted onto the puncture pin. Such a fastener, like the fastener 9 consisting of a combination of concrete screw 91 and washer 92, is extremely inexpensive and easy to use.

[0040] The fastening structure for fire-resistant coatings in exterior wall panels described above is a labor-saving construction method that uses simple fastening devices, while ensuring adequate ventilation space between the left and right stiffeners, and effectively preventing hot air flowing from the outside into the joints where the exterior wall panels are adjacent to each other, over the stiffeners, and into that ventilation space.

[0041] Furthermore, the technical scope of the invention disclosed in this application should not be interpreted restrictively by the exemplary embodiments, but rather conceptually based on the claims. The names of the components used in the claims and specification are for convenience to facilitate a concrete understanding of the invention, and the names do not unnecessarily limit the concept or properties of the components. When implementing the invention disclosed in this application, the detailed shape, dimensions, structure, material, quantity, combination form with other elements, relative positional relationship, etc., of components not specifically identified in the claims may be modified as appropriate, within the scope of using a substantially equivalent operating principle to that of the exemplary embodiment, or within the scope of obtaining substantially equivalent or better effects than those of the exemplary embodiment.

[0042] 10 Exterior wall panel 2 Concrete panel 2a Back side 30 Stiffener 31 Bottom plate 32 Side plate 5 Locking hardware 70 Fire-resistant coating material 71 Fire-resistant coating material for joint backing 9 Fasteners 91 Concrete screws 92 Washers M Joint S Ventilation space

Claims

1. An exterior wall panel comprising: a concrete panel erected in the exterior wall portion of a building; a pair of left and right stiffeners embedded near both side edges of the concrete panel, each having a portion that protrudes further inward than the back surface of the concrete panel, and extending vertically over the entire height of the concrete panel; and a felt mat-like fire-resistant covering material that covers the back surface of the concrete panel and the protruding portions of the two stiffeners from the indoor side, wherein the fire-resistant covering material is fastened to the back surface of the concrete panel from the indoor side using fasteners, the fire-resistant covering material, which is overlapped over substantially the entire surface of the concrete panel except for predetermined areas near the upper and lower edges, is fastened to the concrete panel so as to straddle the stiffeners by fasteners arranged in a vertical line at predetermined intervals on the edge side of the concrete panel closer to each stiffener, and fasteners arranged in a vertical line at predetermined intervals closer to the center of the concrete panel closer to each stiffener, A fastening structure for fire-resistant coating material in an exterior wall panel, characterized in that each fastener attached to the edge side and each fastener attached to the central side are at different heights, and at least one fastener on the other side is positioned within the adjacent spacing in the height direction of one of the fasteners.

2. The fastening structure for a fire-resistant coating material in an exterior wall panel according to claim 1, characterized in that the back surface of the concrete panel is covered with one or more pieces of the fire-resistant coating material cut to the full width of the concrete panel.

3. A fastening structure for fire-resistant coating material in an exterior wall panel according to claim 1 or 2, characterized in that, at locations where two concrete panels are adjacent with a joint in between, a fire-resistant coating material for the back of the joint is superimposed between the stiffening members of the two adjacent concrete panels.

4. A fastening structure for fire-resistant coating material in an exterior wall panel as described in claim 3, characterized in that the fire-resistant coating material for the back of the joint and the fire-resistant coating material covering substantially the entire surface of the concrete panel are overlapped in such a way that their respective joint positions do not coincide with each other.

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