Structural member for water storage tank

Abstract

To provide a structural member for a water storage tank that can improve strength of legs of the structural member for the water storage tank without increasing mass.SOLUTION: A structural member for a water storage tank that secures a storage space of the water storage tank and constitutes a juxtaposed laminated structure by placing a plurality of structural members in a juxtaposed and laminated state, comprises a base and a plurality of legs 40 erected on the base, wherein the legs 40 are hollow, and when a ratio of a diameter of a circumcircle B at a base end portion 44 forming the hollow of the legs 40 to a diameter of an inscribed circle A at the base end portion 44 forming the hollow of the legs 40 is defined as E, and a ratio of a diameter of a circumcircle D at a tip portion 45 forming the hollow of the legs 40 to a diameter of an inscribed circle C at the tip portion 45 forming the hollow of the legs 40 is defined as F, F / E is 1.00 to 1.30.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a structural member for a water storage tank.

Background Art

[0002] A rainwater storage facility is a facility for storing rainwater. For the installation of a rainwater storage facility, a pit is dug in a road, park, parking lot, etc. or a planned site thereof, and a plurality of structural members for water storage tanks (hereinafter also referred to as "structural members") are arranged in the horizontal and vertical directions to form a structure. Then, the surrounding is covered with a permeable or water-impermeable sheet and further backfilled with soil. Since this rainwater storage facility has a water storage tank that forms a large void inside, it can store rainwater. In addition, the arranged structural members can support the load of a facility constructed above. As such a structural member, there is a configuration including a base and a plurality of legs erected on the base (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the legs of the structural member are required to have improved strength in order to support the load of a facility constructed above. And to improve the strength, for example, it is conceivable to increase the wall thickness of the legs. However, when the wall thickness of the legs is increased, the mass of the legs increases. For this reason, the overall mass of the structural member, and thus the manufacturing cost of the structural member, also increases.

[0005] Therefore, an object of the present invention is to improve the strength of a structural member for a water storage tank without increasing the mass.

Means for Solving the Problems

[0006] In order to solve the above problems, a structural member for a water storage tank is provided, which includes a base and a plurality of legs erected on the base, and forms a juxtaposed and laminated structure by juxtaposing and laminating a plurality of them to secure a storage space of the water storage tank. The legs are hollow. When the ratio of the diameter of the circumscribed circle B to the diameter of the inscribed circle A at the base end of the hollow of the leg is E, and the ratio of the diameter of the circumscribed circle D to the diameter of the inscribed circle C at the tip end of the hollow of the leg is F, F / E is 1.00 to 1.30.

[0007] Also, when the ratio of the diameter of the inscribed circle A to the diameter of the inscribed circle C is G, and the ratio of the diameter of the circumscribed circle B to the diameter of the circumscribed circle D is H, G / H is 1.00 to 1.30. E is 1.0 to 1.4, and F is 1.2 to 1.6.

[0008] G is 1.3 to 1.7, and H is 1.2 to 1.5. The cross-section of the leg is formed in a line-symmetric shape. On the outer peripheral surface of the leg, convex portions protruding in the radial direction and concave portions recessed with respect to the convex portions are alternately formed in the circumferential direction, and the convex portions and the concave portions are formed over the entire height direction of the leg.

[0009] A structural member for a water storage tank is provided, which includes a base and a plurality of legs erected on the base, and forms a juxtaposed and laminated structure by juxtaposing and laminating a plurality of them to secure a storage space of the water storage tank. The legs are hollow. When the ratio of the diameter of the inscribed circle A to the diameter of the inscribed circle C at the base end of the hollow of the leg is G, and the ratio of the diameter of the circumscribed circle B to the diameter of the circumscribed circle D at the base end of the hollow of the leg is H, G / H is 1.00 to 1.30.

Advantages of the Invention

[0010] According to the present invention, it is possible to improve the strength of the structural member for a water storage tank without increasing the mass.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0012] Hereinafter, Example 1, which is an embodiment of the juxtaposed laminated structure 10 embodying the present invention and the structural member 20 constituting the juxtaposed laminated structure 10, will be described with reference to FIGS. 1 to 6. For convenience of explanation, the juxtaposed laminated structure 10 and the structural member 20 are described with respect to the direction of each component on the assumption that they are installed on a horizontally formed floor surface, for example, a floor surface on which concrete has been placed. In addition, when there are a plurality of components in each figure, reference numerals may be given only to a part of them.

[0013] FIG. 1 shows a side view of the juxtaposed laminated structure 10. The juxtaposed laminated structure 10 secures a storage space for a water storage tank by laminating a plurality of structural members 20 while juxtaposing them. In FIG. 1, a plurality of structural members 20 are juxtaposed in the horizontal direction to form the lower stage of the juxtaposed laminated structure 10. Also in the figure, the structural members 20 turned upside down are juxtaposed on the lower-stage structural members 20 to form the middle stage of the juxtaposed laminated structure 10. Further, in the figure, the structural members 20 in the same direction as the lower stage are juxtaposed on the middle stage to form the upper stage of the juxtaposed laminated structure 10.

[0014] (Structural member 20) FIG. 2 shows a perspective view of the structural member 20, FIG. 3 shows a rear perspective view, and FIG. 4 shows a plan view. Also, FIG. 5 shows a partial longitudinal section. As shown in FIGS. 2 to 4, the structural member 20 has a base 30 having a substantially rectangular shape in plan view and four legs 40 erected upward from the four corners of the base 30. The structural member 20 is integrally formed of a synthetic resin such as polypropylene (including recycled materials) for the base 30 and the legs 40. Although the structural member 20 is used in combination after being turned upside down as shown in FIG. 1, when referring to the top and bottom of the structural member 20, it means the orientation in which the base 30 is located below and the legs 40 are located above as shown in FIGS. 2 and 5.

[0015] (Base 30) As shown in FIGS. 2 to 4, the base 30 has a substantially square shape in plan view. The base 30 includes an outer frame portion 31 located on the outer periphery, a frame-shaped rib portion 32 located inside the outer frame portion 31, a flat portion 33, a vertical rib portion 34, and a horizontal rib portion 35 located inside the frame-shaped rib portion 32, and these are integrally formed of resin.

[0016] As shown in FIGS. 2 to 4, the outer frame portion 31 has a square frame shape in plan view. Further, the frame-shaped rib portion 32 is a thin plate shape extending upward from the upper surface of the outer frame portion 31 inside the outer frame portion 31, and has a square frame shape in plan view similar to the outer frame portion 31.

[0017] Inside the inner side surrounded by the frame-shaped rib portion 32, flat portions 33 are respectively formed at the four corners in plan view. Each flat portion 33 is formed at the same height as the upper surface of the outer frame portion 31. A plurality of circular cutout holes 36 penetrating in the vertical direction are formed in each flat portion 33. The purpose of this cutout hole 36 is to reduce the weight of the structural member 20 and ensure the flow of water in the base 30. Leg portions 40 described later are formed in each flat portion 33.

[0018] Inside the inner side surrounded by the outer frame portion 31 and the frame-shaped rib portion 32 of the base 30, a plurality of vertical rib portions 34 spanned in the vertical direction (the vertical direction in FIG. 4) between the opposing frame-shaped rib portions 32 and a plurality of horizontal rib 35 portions spanned in the horizontal direction (the left-right direction in FIG. 4) are formed. As shown in FIG. 5, the lower ends of the outer frame portion 31, the vertical rib portion 34, and the horizontal rib portion 35 are located on the same plane, and the upper ends of the frame-shaped rib portion 32, a part of the vertical rib portion 34, and the horizontal rib portion 35 are located on the same plane.

[0019] As shown in FIG. 4, in the base 30, a plurality of cutout holes 36 for the purpose of reducing the weight of the structural member 20 and ensuring the flow of water in the base 30 are also formed in the portion surrounded by the vertical rib portion 34 and the horizontal rib portion 35. The cutout holes 36 between the vertical rib portion 34 and the horizontal rib portion 35 are basically in a substantially rectangular shape. A part of the cutout holes 36 located surrounded by the horizontal rib portion 35 in FIG. 4 are cutout holes 37 for marks formed in a pentagonal shape with the tip facing the outer frame portion 31. This serves as a mark for aligning the orientation of the structural member 20 when the structural member 20 is arranged.

[0020] As shown in FIGS. 1 to 5, on each flat surface portion 33 of the base 30, leg portions 40 erected upward are formed. The four leg portions 40 only differ in their positions on the base 30, and each leg portion 40 has the same shape. For this reason, although one leg portion 40 will be specifically described below, this description equally applies to the other three leg portions 40.

[0021] (Leg portion 40) FIG. 5 shows a side view showing a partial cross-section of the leg portion 40. Of FIG. 5, the left leg portion 40 shows a side surface, and the right leg portion 40 shows a longitudinal cross-section. As shown in FIGS. 2 to 5, the leg portion 40 has a cylindrical shape with its upper end closed by a tip surface 41. On the side surface of the leg portion 40, concave portions 42 and convex portions 43 are alternately formed in the circumferential direction over the entire height direction in a plan view.

[0022] Also, as shown in FIGS. 3 and 5, a base end portion 44 which is the lower end of the leg portion 40 is located on the same plane as the lower ends of the outer frame portion 31, the vertical rib portion 34, and the horizontal rib portion 35 below the flat surface portion 33. For this reason, the load acting in the vertical direction on the leg portion 40 can be received not only by the base end portion 44 but also by the outer frame portion 31, the vertical rib portion 34, and the horizontal rib portion 35 of the structural member 20.

[0023] The leg portions 40 are formed with the same wall thickness regardless of the location. Note that the wall thickness of the leg portions 40 may be different depending on the location. Also, the inside of the leg portions 40 is hollow. The leg portions 40 are connected to the flat surface portion 33, and the base 30 and the leg portions 40 are integrally formed. The leg portions 40 are formed in a tapered shape that tapers as it goes upward to the tip.

[0024] Fig. 6(a) shows a perspective view of only the leg portion 40. As shown in the figure, six concave portions 42 formed in the circumferential direction extend over the entire height direction of the leg portion 40. Specifically, the leg portion 40 is formed by forming concave portions 42 of the same shape at each corner based on a regular hexagonal pyramid without a vertex with an inclination angle of 4 degrees. Therefore, the leg portion 40 has the same shape even when rotated by 60 degrees each in the plan view shown in Fig. 4. The inclination angle of the leg portion 40 can be 1 to 10 degrees, and preferably 3 to 6 degrees. Further, the portion that becomes the side of the regular hexagonal pyramid becomes a convex portion 43 that protrudes relatively in the radial direction, and the portion between adjacent convex portions 43 becomes a concave portion 42 that is relatively recessed. The convex portion 43 has a trapezoidal shape in which the width (circumferential direction) becomes narrower as it goes upward in the side view of the leg portion 40. The concave portions 42 and the convex portions 43 are alternately formed in the circumferential direction of the leg portion 40.

[0025] Fig. 6(b) shows an end view of the base end portion 44 of the leg portion 40. As shown in this figure, on the outer peripheral surface of the end face of the base end portion 44 of the leg portion 40, recesses 42 of the same shape are formed at each corner with a regular hexagon as a reference. The recess 42 has two convex arc portions 46 that extend inward in a convex arc shape from both adjacent convex portions 43, a straight line portion 47 of a certain length following each convex arc portion 46, and a concave arc portion 48 that is a concave arc connected to one end of each straight line portion 47. Each convex arc portion 46 has a constant curvature and extends to the tip with this curvature. For this reason, each convex arc portion 46 has a shape in which convex arcs of the same shape are continuous in the height direction of the recess 42. Also, as shown in Fig. 6(b), the distance between both straight line portions 47 becomes narrower as they approach the center of the leg portion 40. The concave arc portion 48 following both straight line portions 47 has a constant curvature and extends to the tip with this curvature. For this reason, the concave arc portion 48 has a shape in which concave arcs of the same shape are continuous in the height direction of the recess 42. This concave arc portion 48 constitutes the bottom of the recess 42. The outer peripheral surface shape of each recess 42 is line-symmetric with respect to a line connecting the center of the leg portion 40 and the lowest point of the recess 42 in plan view. Also, in the recess 42 of the base end portion 44, the two straight line portions 47 are positioned opposite each other. The angle of the intersection point (hereinafter simply referred to as the "intersection angle") of the extensions of both straight line portions 47 in plan view is 120 degrees. The intersection angle is the same angle from the base end portion 44 to the tip end portion 45, and the same applies to Example 2 and below. Note that the numerical value of the intersection angle includes a range of plus or minus 5 degrees including the tolerance. For this reason, the intersection angle of 120 degrees means a range of 115 degrees to 125 degrees including the tolerance. The outer peripheral surface shape and the inner peripheral surface shape of the base end portion 44 are substantially similar shapes.

[0026] FIG. 6(c) shows an end view of the tip portion 45 of the leg portion 40. The tip portion 45 of the leg portion 40 shown in the figure is a portion immediately below the tip surface 41 that covers the tip of the leg portion 40, and is an end view of the leg portion 40 at a position along the lower surface of the tip surface 41. Further, since the leg portion 40 is based on a regular hexagonal pyramid without a vertex with an inclination angle of 4 degrees, concave portions 42 having the same shape are formed at each corner on the outer peripheral surface of the end surface of the tip portion 45 of the leg portion 40 with reference to a regular hexagon. Each concave portion 42 has a line-symmetric shape in plan view similar to that of the base end portion 44. Since the concave portion 42 is formed over the entire height direction of the leg portion 40, the tip portion 45 also has two convex arc portions 46, two straight portions 47, and a concave arc portion 48 connecting the two straight portions 47, which were described earlier for the base end portion 44. The lengths of the two straight portions 47 at the tip portion 45 in FIG. 6(c) are longer than the lengths of the straight portions 47 at the base end portion 44 in FIG. 6(b). For this reason, the plane formed by continuously forming each straight portion 47 in the height direction has a trapezoidal shape with an upper width longer than the lower width. Also, the intersection angle of the opposing straight portions 47 in the concave portion 42 of the tip portion 45 is 120 degrees. Further, the outer peripheral surface shape and the inner peripheral surface shape of the tip portion 45 are substantially similar. Note that when the wall thickness of the leg portion 40 is made different, etc., the outer peripheral surface shape and the inner peripheral surface shape of the tip portion 45 may be different shapes.

[0027] Here, as shown in FIG. 7(a), a circle inscribed in the inner peripheral surface of the base end portion 44 of the leg portion 40 is defined as the inscribed circle A, and a circle circumscribed about the outer peripheral surface of the base end portion 44 is defined as the circumscribed circle B. Also, as shown in FIG. 7(b), a circle inscribed in the inner peripheral surface of the tip portion 45 is defined as the inscribed circle C, and a circle circumscribed about the outer peripheral surface of the tip portion 45 is defined as the circumscribed circle D. The following relationships are preferable for these.

[0028] Let the ratio of the diameter of the circumscribed circle B to the diameter of the inscribed circle A be E, and the ratio of the diameter of the circumscribed circle D to the diameter of the inscribed circle C be F. When F / E is in the range of 1.00 to 1.30. Also, let the ratio of the diameter of the inscribed circle A to the diameter of the inscribed circle C be G, and the ratio of the diameter of the circumscribed circle B to the diameter of the circumscribed circle D be H. When G / H is in the range of 1.00 to 1.30. Further, the above-mentioned E is 1.0 to 1.4 and the above-mentioned F is 1.2 to 1.6. The above-mentioned G is 1.3 to 1.7 and the above-mentioned H is 1.2 to 1.5. When the relationship between the diameters of the inscribed circles A to D at the base end portion 44 and the tip end portion 45 of the leg portion 40 satisfies these conditions, even when a load is applied to the leg portion 40 from above, the displacement of the leg portion 40 is small and the strength is large.

[0029] Next, Examples 2 to 5 will be described. Since each example has the same base 30 as Example 1 and the shape of the leg portion 40 is different, only the leg portion 40 different from Example 1 will be described.

[0030] Example 2 Fig. 8(a) shows a perspective view of only the leg portion 40 of Example 2. As shown in the figure, the outer shape of the leg portion 40 has six-shaped recesses 42 formed in the circumferential direction extending throughout the height direction. Specifically, the leg portion 40 is formed by forming recesses 42 of the same shape at each corner based on a regular hexagonal pyramid without a vertex with an inclination angle of 4 degrees. For this reason, the leg portion 40 has the same shape even when rotated by 60 degrees in the plan view shown in Fig. 4. Also, the portion that becomes the side of the regular hexagonal pyramid becomes a convex portion 43 that protrudes relatively in the radial direction, and the portion between adjacent convex portions 43 becomes a recessed portion 42 that is relatively recessed. The recessed portions 42 and the convex portions 43 are alternately formed in the circumferential direction of the leg portion 40. A tip end face 41 that covers the tip end of the leg portion 40 is formed on the tip end face of the leg portion 40.

[0031] Fig. 8(b) shows an end view of the base end portion 44 of the leg portion 40. As shown in the figure, on the outer peripheral surface of the end face of the base end portion 44 of the leg portion 40, concave portions 42 of the same shape are formed at each corner with a regular hexagon as a reference. The outer peripheral surface shape of each concave portion 42 is line-symmetric in plan view as in the first embodiment. Further, the concave portion 42 has two convex arc portions 46 that extend inward in a convex arc from both adjacent convex portions 43, a straight line portion 47 of a certain length following each convex arc portion 46, and a concave arc portion 48 that is a concave arc connected to one end of each straight line portion 47. The concave arc portion 48 constitutes the bottom of the concave portion 42. In the concave portion 42 of the base end portion 44, the two straight line portions 47 are located opposite to each other. The intersection angle of both straight line portions 47 is 80 degrees. The wall thickness of the leg portion 40 is the same regardless of the location. The outer peripheral surface shape and the inner peripheral surface shape of the base end portion 44 are substantially similar. Each convex arc portion 46 has a constant curvature and extends to the tip with this curvature. Therefore, each convex arc portion 46 has a shape in which convex arcs of the same shape are continuous in the height direction of the concave portion 42. Further, the concave arc portion 48 has a constant curvature and extends to the tip with this curvature. Therefore, the concave arc portion 48 has a shape in which concave arcs of the same shape are continuous in the height direction of the concave portion 42. This point is the same as in the first embodiment, and the same applies to the third and subsequent embodiments.

[0032] Fig. 8(c) shows an end view of the tip portion 45 of the leg portion 40. The tip portion 45 of the leg portion 40 shown in the figure is a portion directly below the tip surface 41 that covers the tip of the leg portion 40, and is an end view of the leg portion 40 at a position along the lower surface of the tip surface 41. Also, since the leg portion 40 is based on a regular hexagonal pyramid without a vertex with an inclination angle of 4 degrees, concave portions 42 having the same shape are formed at each corner of the outer peripheral surface of the end face of the tip portion 45 of the leg portion 40 with reference to a regular hexagon. Each concave portion 42 has a line-symmetric shape in plan view as in Example 1. Since the concave portion 42 is formed over the entire height direction of the leg portion 40, the tip portion 45 also has two convex arc portions 46, two straight portions 47, and a concave arc portion 48 connecting both straight portions 47, which were described for the base end portion 44 earlier. Also, in the concave portion 42 of the tip portion 45, the intersection angle of the opposing straight portions 47 is 80 degrees. Further, the outer peripheral surface shape and the inner peripheral surface shape of the tip portion 45 are substantially similar. The lengths of both straight portions 47 at the tip portion 45 in Fig. 8(c) are longer than the lengths of the straight portions 47 at the base end portion 44 in Fig. 6(b). For this reason, the plane formed by continuously forming each straight portion 47 in the height direction has a trapezoidal shape with an upper width longer than the lower width. This point is the same as in Example 1, and the same applies to Example 3 and below.

[0033] Example 3 Fig. 9(a) shows a perspective view of only the leg portion 40 of Example 3. As shown in the figure, the external shape of the leg portion 40 has six-shaped concave portions 42 formed in the circumferential direction extending over the entire height direction. Specifically, the leg portion 40 is formed with concave portions 42 having the same shape at each corner with reference to a regular hexagonal pyramid without a vertex with an inclination angle of 4 degrees. For this reason, the leg portion 40 has the same shape even when rotated by 60 degrees in plan view as shown in Fig. 4. Also, the portion that becomes the side of the regular hexagonal pyramid becomes a convex portion 43 that protrudes relatively in the radial direction, and the portion between adjacent convex portions 43 becomes a concave portion 42 that is relatively recessed. The concave portions 42 and the convex portions 43 are alternately formed in the circumferential direction of the leg portion 40. A tip surface 41 that covers the tip of the leg portion 40 is formed on the tip end face of the leg portion 40.

[0034] Fig. 9(b) shows an end view of the base end portion 44 of the leg portion 40. As shown in this figure, on the outer peripheral surface of the end face of the base end portion 44 of the leg portion 40, recesses 42 of the same shape are formed at each corner with a regular hexagon as a reference. The outer peripheral surface shape of each recess 42 is line-symmetric in plan view, similar to that of the first embodiment. Further, the recess 42 has two convex arc portions 46 that extend inward in a convex arc from both adjacent convex portions 43, a straight line portion 47 of a certain length following each convex arc portion 46, and a concave arc portion 48 that is a concave arc connected to one end of each straight line portion 47. The concave arc portion 48 constitutes the bottom of the recess 42. In the recess 42 of the base end portion 44, the two straight line portions 47 are positioned opposite to each other. The intersection angle of both straight line portions 47 is 75 degrees. The wall thickness of the leg portion 40 is the same regardless of the location. The outer peripheral surface shape and the inner peripheral surface shape of the base end portion 44 are substantially similar.

[0035] Fig. 9(c) shows an end view of the tip end portion 45 of the leg portion 40. The tip end portion 45 of the leg portion 40 shown in this figure is a portion immediately below the tip end face 41 that covers the tip of the leg portion 40, and is an end view of the leg portion 40 at a position along the lower surface of the tip end face 41. Further, since the leg portion 40 is based on a regular hexagonal pyramid without a vertex with an inclination angle of 4 degrees, on the outer peripheral surface of the end face of the tip end portion 45 of the leg portion 40, recesses 42 of the same shape are also formed at each corner with a regular hexagon as a reference. Each recess 42 is line-symmetric in plan view, similar to that of the first embodiment. Since the recess 42 is formed over the entire height direction of the leg portion 40, the tip end portion 45 also has the two convex arc portions 46, the two straight line portions 47, and the concave arc portion 48 connected to both straight line portions 47, which were described for the base end portion 44 earlier. In the recess 42 of the tip end portion 45, the intersection angle of the opposing straight line portions 47 is also 75 degrees. Also, the outer peripheral surface shape and the inner peripheral surface shape of the tip end portion 45 are substantially similar.

[0036] Embodiment 4 Fig. 10(a) shows a perspective view of only the leg portion 40 of Example 4. As shown in this figure, the external shape of the leg portion 40 has an 8-shaped recess 42 formed in the circumferential direction extending throughout the height direction. Specifically, the leg portion 40 is formed by forming recesses 42 of the same shape at each corner based on a regular octagonal pyramid without a vertex with an inclination angle of 4 degrees. Therefore, the leg portion 40 has the same shape even when rotated by 45 degrees in the plan view shown in Fig. 4. Also, the portion that becomes the side of the regular octagonal pyramid becomes a convex portion 43 that protrudes relatively in the radial direction, and the recess 42 is relatively recessed between adjacent convex portions 43. The recess 42 and the convex portion 43 are alternately formed in the circumferential direction of the leg portion 40. A tip end face 41 that covers the tip end of the leg portion 40 is formed on the tip end face of the leg portion 40.

[0037] Fig. 10(b) shows an end view of the base end portion 44 of the leg portion 40. As shown in this figure, the outer peripheral surface of the end face of the base end portion 44 of the leg portion 40 forms recesses 42 of the same shape at each corner based on a regular octagon. The outer peripheral surface shape of each recess 42 is line-symmetric in the plan view as in Example 1. Also, the recess 42 has two convex arc portions 46 that extend inward in a convex arc from both adjacent convex portions 43, a straight line portion 47 of a certain length following each convex arc portion 46, and a concave arc portion 48 that is a concave arc connected to one end of each straight line portion 47. The concave arc portion 48 constitutes the bottom of the recess 42. In the recess 42 of the base end portion 44, the two straight line portions 47 are positioned opposite to each other. The intersection angle of both straight line portions 47 is 65 degrees. The wall thickness of the leg portion 40 is the same regardless of the location. The outer peripheral surface shape and the inner peripheral surface shape of the base end portion 44 are substantially similar shapes.

[0038] FIG. 10(c) shows an end view of the tip portion 45 of the leg portion 40. The tip portion 45 of the leg portion 40 shown in the figure is a portion directly below the end face 41 covering the tip of the leg portion 40, and is an end view of the leg portion 40 at a position along the lower surface of the end face 41. Further, since the leg portion 40 is based on a regular octagonal pyramid without a vertex with an inclination angle of 4 degrees, concave portions 42 having the same shape are formed at each corner of the outer peripheral surface of the end face of the tip portion 45 of the leg portion 40 with reference to a regular octagon. Each concave portion 42 has a line-symmetric shape in plan view as in the first embodiment. Since the concave portion 42 is formed over the entire height direction of the leg portion 40, the tip portion 45 also has two convex arc portions 46, two straight portions 47, and a concave arc portion 48 connecting the two straight portions 47, which were described above for the base end portion 44. Also, in the concave portion 42 of the tip portion 45, the intersection angle of the opposing straight portions 47 is 65 degrees. Further, the outer peripheral surface shape and the inner peripheral surface shape of the tip portion 45 are substantially similar.

[0039] Embodiment 5 FIG. 11(a) shows a perspective view of only the leg portion 40 of Embodiment 5. As shown in the figure, the external shape of the leg portion 40 has an 8-shaped concave portion 42 formed in the circumferential direction and extending over the entire height direction. Specifically, the leg portion 40 is formed with concave portions 42 having the same shape at each corner with reference to a regular octagonal pyramid without a vertex with an inclination angle of 4 degrees. For this reason, the leg portion 40 has the same shape even when rotated by 45 degrees in plan view as shown in FIG. 4. Further, the portion that becomes the side of the regular octagonal pyramid becomes a convex portion 43 that protrudes relatively in the radial direction, and the portion between adjacent convex portions 43 becomes a concave portion 42 that is relatively recessed. The concave portions 42 and the convex portions 43 are alternately formed in the circumferential direction of the leg portion 40. An end face 41 covering the tip of the leg portion 40 is formed on the tip end face of the leg portion 40.

[0040] Fig. 11(b) shows an end view of the base end portion 44 of the leg portion 40. As shown in this figure, on the outer peripheral surface of the end face of the base end portion 44 of the leg portion 40, recesses 42 of the same shape are formed at each corner with a regular octagon as a reference. The outer peripheral surface shape of each recess 42 is line-symmetric in plan view as in the first embodiment. Further, the recess 42 has two convex arc portions 46 that extend inward in a convex arc from both adjacent convex portions 43, a straight portion 47 of a certain length following each convex arc portion 46, and a concave arc portion 48 that is a concave arc connected to one end of each straight portion 47. The concave arc portion 48 constitutes the bottom of the recess 42. In the recess 42 of the base end portion 44, the two straight portions 47 are positioned opposite to each other. The intersection angle of both straight portions 47 is 90 degrees. The wall thickness of the leg portion 40 is the same regardless of the location. The outer peripheral surface shape and the inner peripheral surface shape of the base end portion 44 are substantially similar.

[0041] Fig. 11(c) shows an end view of the tip end portion 45 of the leg portion 40. The tip end portion 45 of the leg portion 40 shown in this figure is a portion immediately below the tip end face 41 that covers the tip of the leg portion 40, and is an end view of the leg portion 40 at a position along the lower surface of the tip end face 41. Further, since the leg portion 40 is based on a regular octagonal pyramid without a vertex with an inclination angle of 4 degrees, recesses 42 of the same shape are also formed at each corner of the outer peripheral surface of the end face of the tip end portion 45 of the leg portion 40 with a regular octagon as a reference. Each recess 42 is line-symmetric in plan view as in the first embodiment. Since the recess 42 is formed over the entire height direction of the leg portion 40, the tip end portion 45 also has two convex arc portions 46, two straight portions 47, and a concave arc portion 48 connected to both straight portions 47, which were described for the base end portion 44 earlier. Also in the recess 42 of the tip end portion 45, the intersection angle of the opposing straight portions 47 is 90 degrees. Further, the outer peripheral surface shape and the inner peripheral surface shape of the tip end portion 45 are substantially similar.

[0042] Next, the strength test for the leg portion 40 of each of the above embodiments will be described. Regarding only the leg portions 40 of each embodiment, the outer dimensions of the base end portions 44 were all set to 129 mm (distance between the outer peripheral surfaces of the opposing sides of the polygonal pyramid that forms the leg portion 40) × 219 mm (height of the leg portion 40), and leg portions 40 made of recycled polypropylene with a mass of 326 g were created using 3DCAD. Since the shapes of each embodiment were different, the wall thickness of the leg portion 40 including the tip surface 41 of each embodiment was made different, and the mass of the leg portion 40 was made the same regardless of the difference in shape. The wall thickness of the leg portion 40 is the same regardless of location.

[0043] Next, as shown in Fig. 12(a) with a perspective view, Fig. 12(b) with an end view of the base end portion 44, and Fig. 12(c) with an end view of the tip end portion 45, a leg portion 40 with the corners of a regular square pyramid without a vertex and an inclination angle of 4 degrees chamfered was used as a comparative example. This comparative example also had the outer dimensions of the base end portion 44 all set to 129 mm (distance between the outer peripheral surfaces of the opposing sides of the polygonal pyramid that forms the leg portion 40) × 219 mm (height), and the material used was recycled polypropylene with a mass of 326 g, adjusted to match the embodiment. The wall thickness of the leg portion 40 is the same regardless of location. The basic shape of the leg portion 40, the presence or absence of the recess 42, the intersection angle of the straight portion 47 in the recess 42, and the wall thickness of the leg portion 40 in each embodiment and comparative example are shown below in Table 1.

[0044]

Table 1

[0045]

Table 2

[0046]

Table 3

[0047] According to the above embodiment, the following effects can be obtained. (1) The leg portion 40 was such that when the ratio of the diameter of the circumscribed circle B to the diameter of the inscribed circle A at the base end portion 44 was E and the ratio of the diameter of the circumscribed circle D to the diameter of the inscribed circle C at the tip end portion 45 was F, F / E was 1.00 to 1.30. Thereby, the strength of the leg portion 40 of the structural member 20 for the water storage tank can be improved without increasing the mass.

[0048] (2) The leg portion 40 was such that when the ratio of the diameter of the inscribed circle A to the diameter of the inscribed circle C was G and the ratio of the diameter of the circumscribed circle B to the diameter of the circumscribed circle D was H, G / H was 1.00 to 1.30. Thereby, the strength can be improved similarly.

[0049] (3) The leg portion 40 was such that E was 1.0 to 1.4 and F was 1.2 to 1.6. Thereby, the strength of the leg portion 40 can be improved similarly. (4) The leg portion 40 was such that G was 1.3 to 1.7 and H was 1.2 to 1.5. Thereby, the strength of the leg portion 40 can be improved similarly.

[0050] (5) The end face (cross-section) of the leg portion 40 is formed in a line-symmetric shape in plan view. Thereby, unevenness in displacement generated in the circumferential direction of the leg portion 40 during loading can be reduced. (6) On the outer peripheral surface of the leg portion 40, concave portions 42 and convex portions 43 that protrude in the radial direction are alternately formed in the circumferential direction. The concave portions 42 and the convex portions 43 are formed over the entire height direction of the leg portion 40. Thereby, unevenness in displacement generated in the height direction of the leg portion 40 during loading can be reduced.

[0051] Note that the above-described embodiment may be modified as follows. (1) The shape of the leg portion 40 is not limited to the above-described embodiment and may be appropriately changed. (2) The shape of the tip end face 41 of the leg portion 40 may be made concave and convex vertically, and may be a shape in which the tip end faces 41 of the leg portions 40 inverted vertically fit together. Thereby, the leg portions 40 of the structural members 20 inverted vertically can be engaged with each other with concavo-convexity to strengthen the vertical connection.

[0052] (3) A through hole communicating with the inside of the leg portion 40 may be formed in the tip end face 41. Thereby, water can also be stored in the leg portion 40. (4) Although four leg portions 40 are formed on one structural member 20, five or more leg portions may be formed.

[0053] (5) Although the base 30 of the structural member 20 is square in plan view, it is not limited thereto and may be rectangular. (6) The straight portion 47 in the end view of the concave portion 42 may be a curved portion.

[0054] (7) The wall thickness of the leg portion 40 does not have to be the same regardless of the location. For example, regarding the convex portion 43, the wall thickness of the base end portion 44 may be thinner than the wall thickness of the tip end portion 45, specifically, about 1 / 2 to 1 / 3 of the wall thickness.

[0055] · The resin material used for the structural member 20 is not particularly limited. For example, as material properties, virgin materials or recycled materials with a flexural modulus of 1000 to 5000 MPa, preferably 1000 to 2500 MPa, can be used. Further, talc or the like can be added to the resin material as necessary.

[0056] · The thickness of the tip surface 41 may be made thinner than other parts of the leg portion 40. Since the tip surface 41 has little influence on the strength of the leg portion 40, the thickness can be made thinner with respect to the concave portion 42 and the convex portion 43.

[0057] · Reinforcing ribs may be formed inside the leg portion 40. For example, triangular reinforcing ribs spanning the lower surface of the tip surface 41 and the inner peripheral surface of the concave portion 42 or the convex portion 43 may be formed. · Also, in the circumferential direction of the leg portion 40, the thickness of the convex arc portion 46 and the concave arc portion 48 may be made thicker than that of the convex portion 43 and the straight portion 47.

[0058] · Regarding the convex arc portion 46 and the concave arc portion 48, the curvature of the concave side surface may be made relatively small so that the cross section of the convex arc portion 46 and the concave arc portion 48 becomes thicker toward the center of the arc.

Explanation of reference numerals

[0059] A… inscribed circle B… circumscribed circle C… inscribed circle D… circumscribed circle 10… juxtaposed laminated structure 20… structural member 30… base 40… leg portion 42… concave portion 43… convex portion 44… base end portion 45… tip end portion

Claims

1. A structural member for a water storage tank, comprising a base and a plurality of legs erected on the base, and configured to form a juxtaposed and laminated structure by ensuring a storage space of the water storage tank in a state where a plurality of them are juxtaposed and laminated, wherein the legs are hollow, and when the ratio of the diameter of the circumscribed circle B at the base end of the hollow of the leg to the diameter of the inscribed circle A at the base end of the hollow of the leg is E, and the ratio of the diameter of the circumscribed circle D at the tip end of the hollow of the leg to the diameter of the inscribed circle C at the tip end of the hollow of the leg is F, F / E is 1.00 to 1.

30. A structural member for a water storage tank.

2. The structural member for a water storage tank according to claim 1, wherein when the ratio of the diameter of the inscribed circle A to the diameter of the inscribed circle C is G, and the ratio of the diameter of the circumscribed circle B to the diameter of the circumscribed circle D is H, G / H is 1.00 to 1.

30.

3. The structural member for a water storage tank according to claim 1, wherein E is 1.0 to 1.4 and F is 1.2 to 1.

6.

4. The structural member for a water storage tank according to claim 2, wherein G is 1.3 to 1.7 and H is 1.2 to 1.

5.

5. The structural member for a water storage tank according to any one of claims 1 to 4, wherein the cross section of the leg is formed in a line-symmetric shape.

6. The structural member for a water storage tank according to any one of claims 1 to 4, wherein a convex portion protruding in the radial direction and a concave portion recessed with respect to the convex portion are alternately formed in the circumferential direction on the outer peripheral surface of the leg, and the convex portion and the concave portion are formed over the entire height direction of the leg.

7. A structural member for a water storage tank, comprising a base and a plurality of legs erected on the base, and configured to form a juxtaposed and laminated structure by ensuring a storage space of the water storage tank in a state where a plurality of them are juxtaposed and laminated, wherein the legs are hollow, and when the ratio of the diameter of the inscribed circle A at the base end of the hollow of the leg to the diameter of the inscribed circle C at the tip end of the hollow of the leg is G, and the ratio of the diameter of the circumscribed circle B at the base end of the hollow of the leg to the diameter of the circumscribed circle D at the tip end of the hollow of the leg is H, G / H is 1.00 to 1.

30. A structural member for a water storage tank.

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