Internal surface smoothing structure and internal surface smoothing method for corrugated steel sheets

Abstract

This invention provides a corrugated steel sheet with a smooth inner surface structure and method that reduces the roughness coefficient of the inner surface to ensure flow rate, resulting in improved construction efficiency, shorter construction periods, and high durability. [Solution] In a corrugated steel sheet inner surface smoothing structure 1 that smooths the inner surface of a corrugated steel sheet to reduce the roughness coefficient, a flexible inner surface smoothing sheet 3 is interposed between the corrugated top portion 2a of the corrugated steel sheet 2 and a flat bar 4 on the inner surface of the corrugated steel sheet 2 and bolted together from one side of the inner surface, and bolt holes 32, 33, and 34 are formed in the inner surface smoothing sheet 3 only at positions corresponding to the corrugated top portion 2a.

Description

Technical Field

[0001] The present invention relates to an inner surface smoothing structure and an inner surface smoothing method of a corrugated steel sheet formed into a circular or U-shaped cross section from a corrugated steel sheet processed by corrugation.

Background Art

[0002] In a corrugated pipe used as a drain pipe, in order to increase the flow rate flowing on the inner surface, a method of reducing the roughness coefficient by attaching a paving material made of an asphalt material to the corrugated part of the inner surface of the corrugated shape is used.

[0003] For example, in Patent Document 1, in an asphalt-coated corrugated steel sheet 1 for a water channel in which an asphalt mixture 3 is coated on the inner surface of a curved corrugated steel sheet 2 so as to form a smooth inner surface, as the asphalt mixture 3, an asphalt mixed material containing substantially no aggregate and having 75 ± 2% by weight of blown asphalt and the balance being a filler, 2 to 6 kg of short fibers per 1 m 3 An asphalt-coated corrugated steel sheet 1 using an asphalt mixture 3 in which short fibers are mixed is disclosed (see Claim 1 of the claims of Patent Document 1, paragraphs

[0022] to

[0032] of the specification, FIGS. 1 and 3 of the drawings, etc.).

[0004] However, since the paving material used for the asphalt-coated corrugated steel sheet described in Patent Document 1 uses an asphalt material, it is often affected by temperature. In the hot summer season, it softens, and there is a problem that dents occur at places where it interferes with other members. Further, such an asphalt-coated corrugated steel sheet has a problem that when it is inverted, the corrugated steel sheet and the paving material may be peeled off by gravity. Moreover, the paving material may crack due to impact in the cold winter season, and there is also a problem that care is required for storage at the site and handling during construction.

[0005] In addition, the asphalt-coated corrugated steel sheet described in Patent Document 1 aims to smooth the inner surface, but because chunks of bituminous material are attached, the weight increases significantly, which increases the burden of on-site assembly work. Furthermore, since paving material cannot be attached in advance to the bolted joints where corrugated steel sheets are joined together, it is necessary to fill the grooves of the bolted joints with a local repair material called joint filler after assembly. Moreover, molten asphalt is used to bond the paving material and the corrugated (steel) material, but in order to firmly bond the two, the entire surface of the corrugated material must be lined with asphalt in advance, which is a very time-consuming problem.

[0006] To solve these problems, Patent Document 2 discloses an internally coated corrugated steel sheet in which an auxiliary fitting 3 is attached to the inner surface of a corrugated steel sheet formed by combining corrugated steel sheet materials 2a and 2b into a circular or U-shaped cross section, and an abrasion-resistant paving sheet 1, which is made by impregnating sheet-like glass fibers with thermoplastic resin and cutting it to substantially the same shape as the corrugated steel sheet material, is attached to and covers the auxiliary fitting 3 (see claims 1 and 2 of the claims section of Patent Document 2, paragraphs

[0011] to

[0027] of the specification, Figure 3 of the drawings, etc.).

[0007] Furthermore, Patent Document 3 discloses a method for covering the inner surface of a corrugated steel sheet, in which a fiber-reinforced thermoplastic resin composite material is cut to substantially the same shape as the corrugated steel sheet material, and an abrasion-resistant paving sheet 1 is attached to the lower 1 / 4 to 1 / 2 circumference of the inner surface of the corrugated steel sheet, which is formed by combining corrugated steel sheet materials 2a and 2b to form a circular cross-section, using fastening means 3 (see Claim 1 of the claims, paragraphs

[0010] to

[0027] of the specification, and Figures 1 to 6 of the drawings of Patent Document 3).

[0008] Furthermore, Patent Document 4 discloses a corrugated pipe for drainage, comprising a corrugated pipe body 1 and a flat member 2 provided inside the corrugated pipe body 1, wherein the flat member 2 is provided along the inner wall surface of the corrugated pipe body 1 and the corrugated pipe body 1 is divided into multiple sections in the axial direction (see Claim 1 of the claims, paragraphs

[0015] to

[0019] of the specification, and Figures 1 to 5 of the drawings of Patent Document 4).

[0009] The paving sheets described in Patent Documents 2 and 3, and the flat material described in Patent Document 4, can reduce the roughness coefficient of the inner surface of corrugated steel sheets. However, since the paving sheets described in Patent Documents 2 and 3, and the flat material described in Patent Document 4, are in the form of plates, they need to be fastened to the corrugated steel sheets with bolts. This requires time and effort to fasten all of these bolts on-site, which increases construction costs. In addition, the increased number of bolt fastening points naturally leads to increased costs for processing bolt holes and for the bolts themselves.

[0010] Furthermore, the paving sheets described in Patent Documents 2 and 3 had a problem in that stress concentration occurred in the bolt holes drilled in the sheet fixing part due to external forces such as water flow, and repeated loading by water flow caused the sheet to tear and be damaged from the bolt holes. For this reason, there was a strong need for a sheet fixing part with high durability in conventional paving sheets. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2009-275353 [Patent Document 2] Japanese Patent Application Publication No. 7-158775 [Patent Document 3] Japanese Patent Application Publication No. 8-270840 [Patent Document 4] Japanese Patent Application Publication No. 7-252818 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] Therefore, the present invention was devised in view of the aforementioned problems, and its objective is to provide a corrugated steel sheet with a smooth inner surface structure and a method for smoothing the inner surface, which reduces the roughness coefficient of the inner surface to secure flow rate, improves construction efficiency and shortens the construction period, and has high durability. [Means for solving the problem]

[0013] The inner surface smoothing structure for a corrugated steel sheet according to the first invention is an inner surface smoothing structure for a corrugated steel sheet that smooths the inner surface of a corrugated steel sheet to reduce the roughness coefficient, characterized in that a flexible inner surface smoothing sheet is interposed between the corrugation peaks of the corrugated steel sheet and a flat bar and bolted together, and bolt holes are formed in the inner surface smoothing sheet only at positions corresponding to the corrugation peaks.

[0014] The inner surface smoothing structure of the corrugated steel sheet according to the second invention is characterized in that, in the invention according to claim 1, the inner surface smoothing sheet is composed of a plurality of inner surface smoothing sheets that match the inner surface dimensions of the corrugated steel sheet, and the inner surface smoothing sheets are overlapped such that the upstream side faces the inner surface.

[0015] The inner surface smoothing structure of the corrugated steel sheet according to the third invention is characterized in that, in the second invention, the uppermost portion of the plurality of inner surface smoothing sheets is fastened with a band-shaped fastener that is bent according to the inner surface shape of the corrugated steel sheet.

[0016] The inner surface smooth structure of the corrugated steel sheet according to the fourth invention is characterized in that, in the second invention, the inner surface smooth sheets are arranged such that the upstream sheet is superimposed on the downstream sheet, and the two sheets are bolted together.

[0017] The inner surface smoothing structure of the corrugated steel sheet according to the fifth invention is, in the second invention, characterized in that the inner surface smoothing sheets are stacked such that the upstream sheet is placed on top of the downstream sheet, and only the downstream sheet is bolted, and the upstream sheet is placed on top of the bolted joint portion of the downstream sheet.

[0018] The inner surface smoothing structure of the corrugated steel sheet according to the sixth invention is, in the fifth invention, characterized in that the corner portion of the upstream sheet is chamfered obliquely so that the overlapping portion does not sag.

[0019] The inner surface smoothing structure of the corrugated steel sheet according to the seventh invention is, in the first invention, characterized in that the inner surface smoothing sheet is bolted to the corrugated steel sheet in an exchangeable manner with L-shaped bolts from one side of the inner surface.

[0020] The inner surface smoothing structure of the corrugated steel sheet according to the eighth invention is, in the second invention, characterized in that the side portion of the inner surface smoothing sheet is fixed to the flange of the corrugated steel sheet.

[0021] The inner surface smoothing structure of the corrugated steel sheet according to the ninth invention is, in the second invention, characterized in that the positions of the bolt holes of each of the plurality of inner surface smoothing sheets are formed to be the same in accordance with the inner surface dimensions of each of the plurality of corrugated steel sheets.

[0022] The inner surface smoothing structure of the corrugated steel sheet according to the tenth invention is, in the first invention, characterized in that the inner surface smoothing sheet is made of a material that is less likely to deteriorate against ultraviolet rays.

[0023] The inner surface smoothing method of the corrugated steel sheet according to the eleventh invention is an inner surface smoothing method of a corrugated steel sheet that smooths the inner surface of a corrugated steel sheet with a waveform to reduce the roughness coefficient, and has an inner surface smoothing sheet mounting step of sandwiching an inner surface smoothing sheet having flexibility and having bolt holes formed only at positions corresponding to the waveform tops of the corrugated steel sheet between a flat bar and the waveform tops and bolt-bonding them.

[0024] The method for smoothing the inner surface of a corrugated steel sheet according to the 12th invention is characterized in that, in the 11th invention, in the step of attaching the inner surface smoothing sheet, each of the plurality of inner surface smoothing sheets adapted to the inner surface dimensions of each steel sheet of the corrugated steel sheet is overlapped and attached so that the upstream side faces the inner surface side.

[0025] The method for smoothing the inner surface of a corrugated steel sheet according to the 13th invention is characterized in that, in the 12th invention, in the step of attaching the inner surface smoothing sheet, the most upstream part of the plurality of inner surface smoothing sheets is fixed by being fastened with a band-shaped fastener bent according to the inner surface shape of the corrugated steel sheet.

[0026] The method for smoothing the inner surface of a corrugated steel sheet according to the 14th invention is characterized in that, in the 12th invention, in the step of attaching the inner surface smoothing sheet, the inner surface smoothing sheets are overlapped such that the upstream sheet is on top of the downstream sheet, and then both sheets are penetrated with bolts and bolted to the corrugated top of the corrugated steel sheet.

[0027] The method for smoothing the inner surface of a corrugated steel sheet according to the 15th invention is characterized in that, in the 12th invention, in the step of attaching the inner surface smoothing sheet, the inner surface smoothing sheets are overlapped such that the upstream sheet is on top of the downstream sheet, and then only the downstream sheet is bolted, and the upstream sheet is overlapped and covered on top of the bolted joint part of the downstream sheet.

[0028] The method for smoothing the inner surface of a corrugated steel sheet according to the 16th invention is characterized in that, in the 11th invention, in the step of attaching the inner surface smoothing sheet, the inner surface smoothing sheet is bolted to the corrugated top of the corrugated steel sheet from one side of the inner surface with an L-shaped bolt so as to be replaceable.

[0029] The method for smoothing the inner surface of a corrugated steel sheet according to the 17th invention is characterized in that, in the 12th invention, in the step of attaching the inner surface smoothing sheet, the side part of the inner surface smoothing sheet is fixed to the flange of the corrugated steel sheet.

[0030] The method for smoothing the inner surface of a corrugated steel sheet according to the 18th invention is characterized in that, in the 11th invention, the positions of the bolt holes in each of the multiple inner surface smoothing sheets are formed to be the same in accordance with the inner surface dimensions of each of the multiple corrugated steel sheets, and in the inner surface smoothing sheet installation step, the upstream sheets are superimposed on the downstream sheets and sequentially bolted together and fixed, so that each of the multiple inner surface smoothing sheets is joined to the same position on each of the multiple corrugated steel sheets. [Effects of the Invention]

[0031] According to Inventions 1 through 18, the roughness coefficient of the inner surface of the corrugated steel sheet can be reduced by the inner surface smoothing sheet, thereby ensuring sufficient flow rate for drainage pipes made of corrugated steel. Furthermore, according to Inventions 1 through 18, compared to conventional methods of attaching a paving material made of bituminous material to the inner surface of the corrugated steel sheet, a lining material is not required, thus reducing construction and manufacturing costs.

[0032] Furthermore, according to Inventions 1 through 18, compared to conventional paving materials made of bituminous material, it is easier to remove the inner smoothing sheet from the corrugated steel sheet, enabling waste disposal and cost recovery through steel scrap. Moreover, according to Inventions 1 through 18, compared to conventional paving materials made of bituminous material, there is no need to bond the paving material to the corrugated steel sheet, ordinary hot-dip galvanized steel sheet can be used for the corrugated steel sheet, inventory management becomes easier, and the unit cost of manufacturing the corrugated steel sheet can be reduced.

[0033] In addition, according to the first to eighteenth inventions, since the inner surface smooth sheet, which has bolt holes formed only at positions corresponding to the peaks of the corrugations of the corrugated steel sheet, is bolted together by bolting from one side of the inner surface, the number of bolted joints can be reduced, resulting in improved construction efficiency and a shorter construction period.

[0034] Furthermore, according to the first to eighteenth inventions, since the inner surface smooth sheet is sandwiched between the flat bar and the corrugated top and bolted together, stress does not concentrate in the bolt holes, and the problem of tearing and damage from repeated loads caused by water flow is solved, thereby improving durability.

[0035] Furthermore, according to the first to eighteenth inventions, the side portion of the inner smooth sheet is sandwiched between the flat bar and the corrugated top portion and bolted together, so the inner smooth sheet can be attached sequentially from one side without wrinkles, which also improves construction efficiency and shortens the construction period.

[0036] In particular, according to the second and twelfth inventions, it is possible to prevent water from entering the gap between the inner smooth sheet and the corrugated steel plate, which would cause the inner smooth sheet to lift and peel off.

[0037] In particular, according to the third and thirteenth inventions, the uppermost portions of the multiple inner surface smooth sheets are secured and fixed with band-shaped fasteners that are bent according to the inner surface shape of the corrugated steel sheet. This prevents water from flowing into the gap between the sheet and the corrugated steel sheet body at the intake portion of the uppermost portion of the inner surface smooth sheet, and prevents the inner surface smooth sheet from floating up.

[0038] In particular, according to the fourth and fourteenth inventions, the inner surface smooth sheets are joined by overlapping the upstream sheet on top of the downstream sheet, and then bolting the bolts through both sheets to the corrugated tops of the corrugated steel plate, thereby more reliably preventing the inner surface smooth sheets from lifting up.

[0039] In particular, according to the fifth and fifteenth inventions, the upstream sheet covers the bolt joints of the downstream sheet, which prevents the fixing bolts near the bottom from wearing down or rusting due to the effects of floating debris, thereby improving durability.

[0040] In particular, according to the sixth invention, the corner portion of the upstream sheet is beveled to prevent the overlapping portion from sagging, so the corner portion of the upstream sheet does not sag, eliminating the need to fix the corner portion, and thus shortening the construction period.

[0041] In particular, according to the 7th and 16th inventions, the inner smooth sheet is bolted to the top of the corrugated surface from one side of the inner surface using an L-shaped bolt so that it can be replaced. This makes maintenance work such as replacing the inner smooth sheet easy and quick, and also reduces maintenance costs.

[0042] In particular, according to the eighth and seventeenth inventions, the side portion of the inner surface smooth sheet is fixed to the flange of the corrugated steel sheet, thereby reducing the number of bolt holes to be provided in the corrugated steel sheet and thus reducing manufacturing costs.

[0043] In particular, according to the 9th and 18th inventions, the positions of the bolt holes in each of the multiple inner surface smooth sheets are formed to be the same as the inner surface dimensions of each of the multiple corrugated steel sheets, and the upstream sheets are overlapped and fixed on top of the downstream sheets from the downstream side so that each of the multiple inner surface smooth sheets is joined to the same position on each of the multiple corrugated steel sheets. This reduces manufacturing costs by unifying the types of inner surface smooth sheets and corrugated steel sheets and reducing the number of types that need to be prepared.

[0044] In particular, according to the tenth invention, since the inner surface smooth sheet is made of a material that is less susceptible to degradation by ultraviolet rays, durability can be improved even when the inner surface smooth sheet is used in an open channel. [Brief explanation of the drawing]

[0045] [Figure 1] Figure 1 is a perspective view showing the smooth inner surface structure of a corrugated steel sheet according to the first embodiment of the present invention. [Figure 2] Figure 2 is a perspective view showing the same corrugated steel sheet with a smooth inner surface structure. [Figure 3]Figure 3 is a front view showing the smooth inner surface sheet of the general part of the smooth inner surface structure described above. [Figure 4] Figure 4 is a front view showing the inner surface smooth sheet at the uppermost part of the inner surface smooth structure described above. [Figure 5] Figure 5 is an enlarged view of section A in Figure 1, mainly showing the joint between the corrugated steel sheet and the smooth inner surface sheet. [Figure 6] Figure 6 is a vertical cross-sectional view mainly showing the joint between the corrugated steel sheet and the smooth inner surface sheet at the uppermost part. [Figure 7] Figure 7 is a partially enlarged view showing a modified example of the joint between the corrugated steel sheet and the inner surface smooth sheet described above. [Figure 8] Figure 8 is a perspective view showing the smooth inner surface structure of a corrugated steel sheet according to a second embodiment of the present invention. [Figure 9] Figure 9 is a vertical cross-sectional view along the tube axis showing the smooth inner surface structure of the same object. [Figure 10] Figure 10(a) is a schematic diagram showing an overview of the corrugated steel sheet with the same smooth inner surface structure 1, and Figure 10(b) is a schematic diagram showing another example of the same smooth inner surface structure corrugated steel sheet. [Modes for carrying out the invention]

[0046] The inner surface smoothing structure of a corrugated steel sheet according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0047] <Smooth inner surface structure of corrugated steel sheet> [First Embodiment] First, the inner surface smooth structure 1 of the corrugated steel sheet according to the first embodiment of the present invention (hereinafter also simply referred to as inner surface smooth structure 1) will be described using Figures 1 to 6. As an example of the corrugated steel sheet 2 according to the first embodiment, a steel U-shaped flume, which is suitably used in open channel waterways such as irrigation channels, collection and drainage channels in landslide areas, and temporary drainage channels for civil engineering works, will be described.

[0048] Figure 1 is a perspective view showing the inner surface smoothing structure 1 of the corrugated steel sheet according to this embodiment, and Figure 2 is a perspective view showing the corrugated steel sheet 2 of the inner surface smoothing structure 1. Figure 3 is a front view showing the inner surface smoothing sheet 3 of the general part of the inner surface smoothing structure 1, and Figure 4 is a front view showing the inner surface smoothing sheet 3' of the uppermost part of the inner surface smoothing structure 1. Figure 5 is an enlarged view of part A of Figure 1, mainly showing the joint between the corrugated steel sheet 2 and the inner surface smoothing sheet 3, and Figure 6 is a vertical cross-sectional view mainly showing the joint between the corrugated steel sheet 2 and the uppermost part of the inner surface smoothing sheet 3'.

[0049] As shown in Figure 1, the inner surface smoothing structure 1 of the corrugated steel sheet according to this embodiment consists of a corrugated steel sheet 2 formed into a corrugated shape from a thin steel sheet, and an inner surface smoothing sheet 3 attached to the inner surface of the corrugated steel sheet 2, etc.

[0050] (Corrugated steel sheet) Corrugated steel sheet 2 is a steel U-shaped flume formed from a thin steel sheet of 1.6 mm to 7.0 mm thickness, such as hot-rolled mild steel sheet SPHC (steel plate hot commercial) or general structural rolled steel SS400, into a corrugated shape with a predetermined pitch (e.g., 68 mm) and a predetermined wave depth (e.g., 13 mm), as shown in Figures 1 and 2, and then bent into a U-shape or a half-cylindrical shape. Of course, corrugated steel sheet 2 is not limited to a U-shape or half-cylindrical shape, but may be bent into an ellipse, cylindrical shape, or any other shape as appropriate.

[0051] Furthermore, since this corrugated steel sheet 2 does not have a paving material made of bituminous material bonded to it, it can be treated with ordinary hot-dip galvanizing for rust prevention. This ensures durability at a low cost. In addition, there is no need to differentiate between special corrugated steel sheets that are not hot-dip galvanized and ordinary corrugated steel sheets that are hot-dip galvanized, making inventory management easier and reducing the unit cost of manufacturing corrugated steel sheets.

[0052] As shown in Figure 2, the corrugated steel sheet 2 is composed of a U-shaped flume body 20 with a roughly U-shaped cross-section, and a flange 21 that protrudes outward along the upper edge of the U-shaped flume body 20. In addition, elongated holes 22 for bolt connection are drilled in the corrugated peak portion 2a, which is the wavy peak (upper part) of the flange 21.

[0053] (Smooth inner surface sheet) As shown in Figure 3, the inner surface smoothing sheet 3 of the general section is made of a lightweight rubber sheet with a thickness of about 1 to 2 mm (1.5 mm thick in this embodiment) and is a paving sheet that is attached to the inner surface of the corrugated steel plate 2, which is corrugated perpendicular to the water flow and has high water resistance, in order to reduce friction and impact, and smooth the inner surface of the corrugated steel plate 2 to reduce the roughness coefficient.

[0054] However, the inner surface smoothing sheet according to the present invention is not particularly limited to a rubber sheet, as long as it is a sheet-like material that has predetermined strength and flexibility and can reduce the roughness coefficient of the inner surface of the corrugated steel sheet, such as a resin sheet or a cloth sheet. This is because, unlike hardened plate-like materials such as steel sheets or FRP sheets described in the background art, any sheet-like material with predetermined strength and flexibility can reduce the roughness coefficient of the inner surface of the corrugated steel sheet by being pushed along with the flow of fluid circulating within the corrugated steel sheet 2, without needing to be fixed in many places with bolts or the like. However, using a rubber sheet for the inner surface smoothing sheet 3 is preferable because it has predetermined elasticity due to rubber elasticity and does not follow the corrugated shape of the corrugated steel sheet, thus greatly reducing the degree to which the roughness coefficient can be reduced.

[0055] However, when the U-shaped flume corrugated steel plate 2 is used in an open channel, the inner surface smooth sheet 3 is preferably made of a resin sheet that is resistant to degradation from ultraviolet rays, such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), PMMA (polymethyl methacrylate), polycarbonate, PVC (polyvinyl chloride), or a highly weather-resistant rubber material such as EPDM (ethylene propylene rubber), CSM (chlorosulfonated polyethylene), IIR (butyl rubber), CR (chloroprene rubber), ANM, Q (silicone rubber), FFKM, KM (fluororubber), CHR, CHC.

[0056] Furthermore, it is preferable that the inner smooth sheet 3 is made of a material that does not soften or harden at room temperature. This is because it can suppress the occurrence of defects caused by temperature, such as softening in the hot summer months and hardening in winter, leading to cracking upon impact. Here, "room temperature" is assumed to be 20°C, as in the Japanese Industrial Standards, and refers to the range of 20°C ± 15°C, i.e., 5°C to 35°C.

[0057] As shown in Figure 3, the inner surface smoothing sheet 3 is composed of a rectangular sheet body 30 that matches the inner dimensions of the corrugated steel plate 2, such as length, width, and height, and overlapping portions 31 which are protrusions for overlapping the upstream inner surface smoothing sheet 3 onto the downstream inner surface smoothing sheet 3.

[0058] Furthermore, as shown in Figure 3, six bolt holes 32 are drilled on each side of the sheet body 30, with three holes on each side, at positions corresponding to the peaks 2a of the corrugated steel plate 2, for securing it by sandwiching it with flat bars 4. These bolt holes 32 are 21 mm in diameter, for inserting M16 L-shaped bolts 5.

[0059] Furthermore, at the top and bottom of the U-shaped flume body 20 of the seat body 30, there are six bolt holes 33 and 34, three on the top and three on the bottom, corresponding to the peaks 2a of the corrugated steel plate 2, for fastening with M8 one-sided bolts 6. These bolt holes 33 and 34 are 14 mm in diameter holes for inserting the M8 one-sided bolts 6.

[0060] Thus, the positions of the bolt holes 32, 33, and 34 in each inner surface smooth sheet 3 are formed to be the same as the inner surface dimensions of each corrugated steel sheet 2. Therefore, by standardizing the types of inner surface smooth sheets 3 and corrugated steel sheets 2, it becomes unnecessary to prepare multiple types of products with different bolt hole positions, thereby reducing manufacturing costs.

[0061] Furthermore, as shown in Figures 1 and 5, the inner surface smooth sheet 3 is interposed and secured between the corrugated peaks 2a of the corrugated steel plate 2 and the strip-shaped flat bar 4. The inner surface smooth sheets 3, 3 are then arranged so that the upstream side faces the inner surface, with the overlapping portion 31 of the upstream sheet 3a superimposed on the sheet body 30 of the downstream sheet 3b, and only the sheet body 30 of the downstream sheet 3b is bolted to the bottom surface of the corrugated steel plate 2 with one-side bolts 6.

[0062] In other words, the overlapping portion 31 of the upstream sheet 3a is superimposed on the bolted joint to which the downstream sheet 3b is joined, and the one-sided bolts 6 that fasten the downstream sheet 3b to the bottom of the U-shaped flume body 20 are covered by the overlapping portion 31 of the upstream sheet 3a. This prevents the one-sided bolts 6 (fixing bolts) near the bottom of the corrugated steel plate 2 from wearing down or rusting due to the effects of floating debris, thereby improving durability.

[0063] Furthermore, the inner surface smooth sheets 3,3 may be arranged such that the upstream side faces the inner surface, with the overlapping portion 31 of the upstream sheet 3a superimposed on the sheet body 30 of the downstream sheet 3b, and both the upstream sheet 3a and the downstream sheet 3b may be bolted to the U-shaped flume body 20 with one-side bolts 6. This is because bolts are passed through both sheets and bolted to the corrugated top portion 2a of the corrugated steel plate 2, which more reliably prevents the inner surface smooth sheet 3 from lifting up.

[0064] However, once the one-sided bolt 6 is tightened, it undergoes plastic deformation and cannot be removed. For this reason, considering maintenance work such as replacing the inner smooth sheet 3, it is preferable that the inner smooth sheet 3 is joined to the bottom of the U-shaped flume body 20 with the aforementioned L-shaped bolt 5 so that it can be replaced from one side of the inner surface. This is because the L-shaped bolt 5 fits into the valleys of the outer surface of the corrugated shape of the corrugated steel plate 2 and can be tightened or loosened by rotating it from one side of the inner surface. In other words, by fixing the corrugated steel plate 2 to the bottom of the U-shaped flume body 20 with the L-shaped bolt 5, maintenance work such as replacing the inner smooth sheet 3 can be performed easily and quickly, and maintenance costs can be reduced.

[0065] As shown in Figures 1, 5, and 3, the corner portion 35 of the upstream sheet 3a is beveled to prevent the overlapping portions of the sides of the U-shaped flume body 20 from sagging. Therefore, the corner portion 35 of the upstream sheet 3a does not sag, eliminating the need to fix the corner portion 35, which in turn shortens the construction period.

[0066] Furthermore, as shown in Figure 4, the inner surface smooth sheet 3' at the uppermost part of the inner surface smooth structure 1 has substantially the same configuration as the aforementioned inner surface smooth sheet 3, but it also has multiple bolt holes 36 drilled in it for fastening and securing with a band-shaped fastener 7 of a predetermined width. These bolt holes 36 are 22 mm in diameter holes for inserting M20 thread bolts 8.

[0067] As shown in Figures 6 and 1, the smooth inner surface sheet 3' at the uppermost part is secured with a band-shaped fastener 7 of a predetermined width, the upstream end of which is bent into a U-shape according to the inner surface shape of the U-shaped flume body 20. The fastener 7 may be made of stainless steel or a resin plate to prevent rusting.

[0068] As shown in Figure 6, this mountain bolt 8 has a specially shaped bolt head 80 that fits into the valley portion 2b, which is the back surface of the corrugated peak portion 2a of the corrugated steel sheet 2. The fastener 7 and the upstream end of the inner smooth sheet 3' are sandwiched between a turtle washer 81 and a regular flat washer 82 corresponding to the valley portion 2b and secured by tightening with a nut 83. This prevents water from flowing into the gap between the inner smooth sheet 3' and the U-shaped flume body 20 (corrugated sheet body) of the corrugated steel sheet 2 at the intake portion, which is the upstream end of the inner smooth sheet 3' at the uppermost part, and prevents the inner smooth sheet 3' and the downstream inner smooth sheet 3 from floating up.

[0069] In the configuration shown in Figure 1, the example illustrates a case where almost the entire inner surface of the U-shaped flume body 20 is covered with the inner surface smoothing sheet 3. However, depending on the design water volume of the drain pipe, it is also acceptable to cover only the lower part of the U-shaped flume body 20. This is because if the amount of water flowing through the drain pipe is small, covering only the lower part is sufficient.

[0070] Furthermore, as shown in Figures 1 and 5, we have described the case in which the inner smooth sheet 3 is fastened to the side portions on both sides of the inner surface of the U-shaped flume body 20 with flat bars 4. However, as shown in Figure 7, the side portions of the inner smooth sheet 3 may also be fixed to the flange 21 of the corrugated steel plate 2 with L-shaped bolts 5 using the aforementioned flat bars 4. This is because the inner smooth sheet 3 can be fixed using the elongated holes 22 formed in the flange 21 without having to drill bolt holes in the side portions of the U-shaped flume body 20. Figure 7 is a partially enlarged view showing a modified example of the joint between the corrugated steel plate 2 and the inner smooth sheet 3.

[0071] [Second Embodiment] Next, the inner surface smooth structure 1' (hereinafter also simply referred to as inner surface smooth structure 1') of the corrugated steel sheet according to the second embodiment of the present invention will be described using Figures 8 to 10. As an example of the corrugated steel sheet 2' according to the second embodiment, a corrugated pipe made of steel sheet, which is corrugated perpendicular to the pipe direction and is suitably used in underground waterways such as irrigation channels, collection and drainage channels in landslide areas, and temporary drainage channels for civil engineering works, will be described.

[0072] Figure 8 is a perspective view showing the inner surface smooth structure 1' of the corrugated steel sheet according to this embodiment, and Figure 9 is a vertical cross-sectional view along the pipe axis showing the inner surface smooth structure 1'. Figure 10(a) is a schematic diagram showing the outline of the corrugated steel sheet with the inner surface smooth structure 1', and Figure 10(b) is a schematic diagram showing another example of the corrugated steel sheet with the inner surface smooth structure 1'.

[0073] The inner surface smoothing structure 1' of the corrugated steel sheet according to the second embodiment consists of a corrugated steel sheet 2' formed into a corrugated shape from a thin steel sheet, and the aforementioned inner surface smoothing sheet 3 attached to the inner surface of the corrugated steel sheet 2'.

[0074] (Corrugated steel sheet) Corrugated steel sheet 2', like the aforementioned corrugated steel sheet 2, is a corrugated steel sheet made by bending corrugated steel sheets, formed from 1.6 mm to 7.0 mm thick thin steel sheets such as hot-rolled mild steel sheet SPHC (steel plate hot commercial) or general structural rolled steel material SS400, into a corrugated shape with a predetermined pitch (e.g., 68 mm) and a predetermined wave depth (e.g., 13 mm), as shown in Figures 8 and 9, into a half-cylindrical shape, and then combining these to form a cylindrical shape. Of course, it goes without saying that corrugated steel sheet 2' may also be bent into an elliptical or cylindrical shape as appropriate to achieve a predetermined shape.

[0075] As shown in Figures 8 and 9, the corrugated steel sheet 2' is composed of a semi-cylindrical arc-shaped steel sheet 20' and a flange 21' that is bent and raised along the edge of the end of the arc-shaped steel sheet 20' and protrudes outward. In addition, elongated holes 22' for bolt connection are drilled in the corrugated peak portion 2a' of the wavy peak (upper part) of the flange 21'.

[0076] Furthermore, the corrugated steel sheet 2' is not limited to the form shown in Figure 10(a), where a flange 21' is created by bending the end of a semicircular section (arc-shaped steel sheet 20') and joining the upper and lower sections with bolts. It may also be a corrugated steel sheet 2' formed by combining several arc-shaped sections 20'', each with a circumference divided into multiple arcs, to create a cross-section, and then joining each section in a lap method with bolts to form a cylindrical shape, as shown in Figure 10(b).

[0077] (Smooth inner surface sheet) The inner surface smooth sheet 3 according to the second embodiment has substantially the same configuration as the inner surface smooth sheet 3 described above, and consists of a lightweight rubber sheet with a thickness of about 1 to 2 mm (1.5 mm thick in this embodiment). Although this inner surface smooth sheet 3 has dimensional differences according to the difference in the inner surface dimensions of the corrugated steel plate 2 and the corrugated steel plate 2' described above, the bolt holes 32, 33, and 34 are formed similarly, so a detailed explanation is omitted.

[0078] Furthermore, as shown in Figures 8 and 9, the smooth inner surface sheet 3 of this smooth inner surface structure 1' is interposed and secured between the corrugated peaks 2a', which are the wavy peaks on the inner surface of the corrugated steel plate 2', and the aforementioned flat bar 4. The smooth inner surface sheets 3, 3 are then joined together by overlapping the overlapping portion 31 of the upstream sheet 3a onto the sheet body 30 of the downstream sheet 3b, with the upstream side facing the inner surface. Only the sheet body 30 of the downstream sheet 3b is bolted to the bottom surface of the corrugated steel plate 2' with one-side bolts 6.

[0079] In other words, as shown in Figure 9, the overlapping portion 31 of the upstream sheet 3a is superimposed on the bolted joint to which the downstream sheet 3b is joined, and the one-side bolts 6 that fasten the downstream sheet 3b to the bottom of the arc-shaped steel plate 20' are covered by the overlapping portion 31 of the upstream sheet 3a. This prevents the one-side bolts 6 (fixing bolts) near the bottom of the corrugated steel plate 2 from wearing down or rusting due to the effects of floating debris, thereby improving durability.

[0080] Furthermore, the inner surface smooth sheets 3,3 may be joined together such that the upstream side faces the inner surface, with the overlapping portion 31 of the upstream sheet 3a superimposed on the sheet body 30 of the downstream sheet 3b, and both the upstream sheet 3a and the downstream sheet 3b bolted to the arc-shaped steel plate 20' with one-side bolts 6. This is because the bolts penetrate both sheets and bolt them to the corrugated top portion 2a of the corrugated steel plate 2, which more reliably prevents the inner surface smooth sheet 3 from lifting up.

[0081] However, once this one-sided bolt 6 is tightened, it deforms plastically and cannot be removed. For this reason, considering maintenance work such as replacing the inner smooth sheet 3, it is preferable that the bolts that fasten the downstream sheet 3b to the bottom of the arc-shaped steel plate 20' are also joined to the inner smooth sheet 3 using the aforementioned L-shaped bolt 5 so that they can be replaced from one side of the inner surface. This is because the L-shaped bolt 5 fits into the valleys of the outer surface of the corrugated shape of the corrugated steel plate 2 and can be tightened or loosened by rotating from one side of the inner surface. In other words, by fixing the corrugated steel plate 2 to the bottom of the arc-shaped steel plate 20' with the L-shaped bolt 5, maintenance work such as replacing the inner smooth sheet 3 can be performed easily and quickly, and maintenance costs can be reduced.

[0082] Furthermore, as shown in Figures 9, 5, and 3, the corner portion 35 of the upstream sheet 3a is beveled to prevent the overlapping portions on both sides of the arc-shaped steel plate 20' from sagging. As a result, the corner portion 35 of the upstream sheet 3a does not sag, eliminating the need to fix the corner portion 35, which in turn shortens the construction period.

[0083] Furthermore, as shown in Figures 8 and 5, the smooth inner surface sheet 3' at the uppermost part is secured with a band-shaped fastener 7 of a predetermined width, the upstream end of which is bent into an arc shape corresponding to the inner surface shape of the arc-shaped steel plate 20'. The fastener 7 may be made of stainless steel or resin to prevent rusting.

[0084] As shown in Figure 6, this bolt 8 for mountain applications has a specially shaped bolt head 80 that fits into the valley portion 2b, which is the back surface of the corrugated peak portion 2a of the corrugated steel sheet 2. The fastener 7 and the upstream end of the inner smooth sheet 3' are sandwiched between a turtle washer 81 and a regular flat washer 82 corresponding to the valley portion 2b and secured by tightening with a nut 83. This prevents water from flowing into the gap between the inner smooth sheet 3' and the arc-shaped steel sheet 20' (corrugated sheet body) of the corrugated steel sheet 2 at the intake portion, which is the upstream end of the inner smooth sheet 3' at the uppermost part, and prevents the inner smooth sheet 3' and the downstream inner smooth sheet 3 from floating up.

[0085] In the configuration shown in Figure 8, the example illustrates a case where almost the entire inner surface of the lower arc-shaped steel plate 20' is covered with the inner surface smoothing sheet 3. However, depending on the design water volume of the drain pipe, it is also acceptable to cover only the lower part of the arc-shaped steel plate 20'. This is because if the amount of water flowing through the drain pipe is small, covering only the lower part is sufficient.

[0086] Furthermore, as shown in Figures 8 and 9, the case in which the inner surface smooth sheet 3 is fastened to the inner surface side portions of the arc-shaped steel plate 20' with flat bars 4 has been described. However, the side portions of the inner surface smooth sheet 3 may also be fixed by sandwiching the inner surface smooth sheet 3 between the flanges 21', 21' of the corrugated steel plate 2' without using flat bars 4 (not shown). This is because the inner surface smooth sheet 3 can be fixed using the elongated holes 22' formed in the flanges 21' without having to drill bolt holes in the side portions of the arc-shaped steel plate 20', thus eliminating the need for flat bars 4.

[0087] <Method for smoothing the inner surface of corrugated steel sheets> Next, a method for smoothing the inner surface of a corrugated steel sheet according to an embodiment of the present invention will be described with reference to Figures 1 to 10.

[0088] (Corrugated steel sheet assembly and installation process) First, in the method for smoothing the inner surface of a corrugated steel sheet according to this embodiment, a corrugated steel sheet assembly and installation step is performed in which the corrugated steel sheet is assembled and installed.

[0089] For example, in the case of the aforementioned smooth inner surface structure 1, a groove is excavated and a corrugated steel plate 2 consisting of a U-shaped flume body 20 is inserted into the excavated groove to be installed as an open channel (see Figure 2, etc.).

[0090] In the case of the aforementioned smooth inner surface structure 1', the flanges 21' of the two upper and lower half-cylindrical arc-shaped steel plates 20' are bolted together to assemble the corrugated steel plate 2', which is then inserted into the excavated horizontal hole and installed as a culvert (see Figure 8).

[0091] (Inner surface smoothing sheet installation process) Subsequently, in the method for smoothing the inner surface of corrugated steel sheets according to this embodiment, an inner surface smoothing sheet mounting step is performed in which the aforementioned inner surface smoothing sheet 3 is attached to the inner surface of the corrugated steel sheets 2, 2'.

[0092] Specifically, an inner surface smoothing sheet 3 is sandwiched between the flat bar 4 and the corrugated top portion 2a, and the U-shaped flume body 20 (arc-shaped steel plate 20') of the corrugated steel plate 2 is bolted together by fastening it with L-shaped bolts 5 from one side of the inner surface.

[0093] In this process, the inner surface smoothing sheets 3, which are matched to the inner surface dimensions of each steel plate, such as the U-shaped flume body 20 of the corrugated steel plates 2,2' and the arc-shaped steel plate 20', are overlapped and attached so that the upstream side faces the inner surface.

[0094] In other words, the overlapping portion 31 of the upstream sheet 3a is placed on top of the sheet body 30 of the downstream sheet 3b so that the upstream side is the inner side, and only the sheet body 30 of the downstream sheet 3b is bolted to the bottom surface of the corrugated steel plate 2 with one-side bolts 6.

[0095] Then, the overlapping portion 31 of the upstream sheet 3a is placed on top of the one-sided bolts 6 to which the downstream sheet 3b is joined, and the one-sided bolts 6 that fasten the downstream sheet 3b to the bottom of the U-shaped flume body 20 and the arc-shaped steel plate 20' are covered with the overlapping portion 31 of the upstream sheet 3a. This prevents the one-sided bolts 6 (fixing bolts) near the bottom of the corrugated steel plate 2.2' from wearing down or rusting due to the effects of floating debris, thereby improving durability.

[0096] However, the inner surface smooth sheets 3,3 may be arranged such that the upstream side faces the inner surface, with the overlapping portion 31 of the upstream sheet 3a superimposed on the sheet body 30 of the downstream sheet 3b, and both sheets, the upstream sheet 3a and the downstream sheet 3b, are bolted to the U-shaped flume body 20 or the arc-shaped steel plate 20' by passing the bolts through both sheets. This is because bolting the bolts through both sheets to the corrugated top portion 2a of the corrugated steel plate 2 can more reliably prevent the inner surface smooth sheet 3 from lifting up.

[0097] However, once this one-sided bolt 6 is tightened, it deforms plastically and cannot be removed. For this reason, considering maintenance work such as replacing the inner smooth sheet 3, it is preferable that the bolts used to fasten the downstream sheet 3b to the bottom of the U-shaped flume body 20 and the arc-shaped steel plate 20' are also L-shaped bolts 5 as described above, so that they can be replaced from one side of the inner surface. This is because the L-shaped bolt 5 fits into the valleys on the outer surface of the corrugated shape of the corrugated steel plate 2, and tension is applied even when rotated from one side of the inner surface, allowing it to be tightened or loosened. In other words, by fixing the corrugated steel plate 2 to the bottom of the U-shaped flume body 20 and the arc-shaped steel plate 20' with L-shaped bolts 5, maintenance work such as replacing the inner smooth sheet 3 can be performed easily and quickly, and maintenance costs can be reduced.

[0098] Furthermore, in this process, as shown in Figure 7, the side portion of the inner smooth sheet 3 can be fixed by bolting it to the flange 21 of the corrugated steel plate 2 with the aforementioned flat bar 4 and L-shaped bolts 5, or by sandwiching the inner smooth sheet 3 between the flanges 21', 21' of the corrugated steel plate 2' without using the flat bar 4 (not shown). This is because the inner smooth sheet 3 can be fixed using the elongated holes 22, 22' formed in the flanges 21, 21' without drilling bolt holes in the side portion of the U-shaped flume body 20 or the arc-shaped steel plate 20'.

[0099] According to the inner surface smoothing structure 1,1' and the inner surface smoothing method for corrugated pipes according to the embodiments of the present invention described above, the inner surface smoothing sheet 3,3' can reduce the roughness coefficient of the inner surface of the corrugated steel plate 2,2', thereby ensuring the flow rate of the drain pipe made of corrugated steel plate 2,2'.

[0100] Furthermore, according to the inner surface smoothing structure 1,1' of the corrugated pipe and the inner surface smoothing method of the corrugated pipe according to this embodiment, a lining material is not required compared to the conventional method of attaching a paving material made of bituminous material to the inner surface of a corrugated steel plate, thus reducing construction and manufacturing costs.

[0101] Furthermore, according to the inner surface smoothing structure 1,1' of the corrugated pipe and the inner surface smoothing method of the corrugated pipe according to this embodiment, the side portion of the inner surface smoothing sheet 3 is sandwiched between the flat bar 4 and the corrugated tops 2a, 2a' and bolted together, so the inner surface smoothing sheet 3 can be installed sequentially from one side without wrinkles forming, which also improves construction efficiency and shortens the construction period.

[0102] Furthermore, according to the inner surface smoothing structure 1,1' of the corrugated pipe and the inner surface smoothing method of the corrugated pipe according to this embodiment, the upstream end of the inner surface smoothing sheet 3' at the uppermost part is secured with a band-shaped fastener 7 that is bent according to the inner surface shape of the U-shaped flume body 20 or the arc-shaped steel plate 20'. This prevents water from flowing into the gap between the sheet and the U-shaped flume body 20 or the arc-shaped steel plate 20' of the corrugated steel plate 2,2' at the uppermost intake part of the inner surface smoothing sheet 3, and prevents the inner surface smoothing sheet 3,3' from floating up.

[0103] In addition, the inner surface smoothing structure 1,1' of the corrugated pipe and the inner surface smoothing method of the corrugated pipe according to this embodiment make it easier to remove the inner surface smoothing sheets 3,3' from the corrugated steel plates 2,2' compared to conventional paving materials made of bituminous material, and enable cost recovery through waste disposal and steel scrap.

[0104] Furthermore, according to the inner surface smoothing structure 1,1' of the corrugated pipe and the inner surface smoothing method of the corrugated pipe according to this embodiment, compared to conventional paving material made of bituminous material, there is no need to bond the paving material to the corrugated steel sheet, and ordinary hot-dip galvanized steel sheet can be used for the corrugated steel sheet 2,2', inventory management becomes easier and the unit cost of manufacturing the corrugated steel sheet can be reduced.

[0105] Although the internal smoothing structures 1 and 1' of the corrugated pipe according to the embodiment of the present invention and the internal smoothing method of the corrugated pipe according to the embodiment of the present invention have been described in detail above, the embodiments described above or illustrated are merely examples of embodiments that have been materialized in carrying out the present invention. Therefore, the technical scope of the present invention should not be interpreted as being limited by these embodiments.

[0106] In particular, in the internal smooth structure 1,1' of the corrugated pipe, L-shaped bolts 5 and one-sided bolts 6 were given as examples of bolts for bolting the internal smooth sheet 3 to the corrugated steel plates 2,2', illustrating so-called one-sided bolts in a broad sense that can be bolted from the inside of the corrugated steel plates 2,2'. However, depending on the construction procedure and site conditions, it may be possible to tighten nuts etc. from the outside, in which case the bolts for bolting the internal smooth sheet 3 to the corrugated steel plates 2,2' are not limited to one-sided bolts in a broad sense. However, it goes without saying that one-sided bolts make construction easier. Furthermore, this one-sided bolt concept includes rivets etc. that can mechanically join the internal smooth sheet 3 to the corrugated steel plates 2,2' with one-sided construction. [Explanation of symbols]

[0107] 1,1': (of corrugated steel sheet) smooth inner surface structure 2,2': Corrugated steel sheet 2a,2a': waveform top 2b: Tanibe 20: U-shaped flume body 20': Arc-shaped steel plate 20": Arc-shaped section 21,21': Flange 22,22': Long hole 3,3': Smooth inner surface sheet 30: Seat body 31: Overlapping section 32, 33, 34: Bolt holes 35: Corner section 36: Bolt holes 4: Flat bar 5: L-shaped bolt 6: One-sided bolt 7: Fasteners 8: Bolts for mountain climbing 80: Bolt head 81: Turtle Washer 82: Flat Washer 83: Nut

Claims

1. A corrugated steel sheet inner surface smoothing structure that smooths the inner surface of a corrugated steel sheet to reduce the roughness coefficient, A flexible, smooth-surfaced sheet is interposed between the corrugated top of the corrugated steel plate and a flat bar on the inner surface of the corrugated steel plate and bolted together. The inner smooth sheet has bolt holes formed only at positions corresponding to the peaks of the corrugations. A corrugated steel sheet characterized by a smooth inner surface structure.

2. The inner surface smoothing sheet is composed of a plurality of inner surface smoothing sheets that match the inner surface dimensions of the corrugated steel plate, and the inner surface smoothing sheets are overlapped so that the upstream side faces the inner surface. The inner surface smooth structure of a corrugated steel sheet according to claim 1, characterized by the above.

3. The uppermost portion of each of the multiple inner surface smooth sheets is secured with a band-shaped fastener that is bent according to the inner surface shape of the corrugated steel sheet. The inner surface smooth structure of the corrugated steel sheet according to claim 2, characterized by the above.

4. The aforementioned smooth inner surfaces of the sheets are arranged such that the upstream sheet is placed on top of the downstream sheet, and the two sheets are bolted together. The inner surface smooth structure of the corrugated steel sheet according to claim 2, characterized by the above.

5. The aforementioned smooth inner surfaces of the sheets are arranged such that the upstream sheet is placed on top of the downstream sheet, and only the downstream sheet is bolted together, with the upstream sheet placed on top of the bolted joint of the downstream sheet. The inner surface smooth structure of the corrugated steel sheet according to claim 2, characterized by the above.

6. The corners of the upstream sheet are beveled at an angle so that the overlapping portions do not sag. The inner surface smooth structure of a corrugated steel sheet according to claim 5, characterized by the above.

7. The aforementioned smooth inner surface sheet is bolted to the corrugated steel plate from one side of the inner surface using L-shaped bolts, making it replaceable. The inner surface smooth structure of a corrugated steel sheet according to claim 1, characterized by the above.

8. The side portion of the inner smooth sheet is fixed to the flange of the corrugated steel plate. The inner surface smooth structure of the corrugated steel sheet according to claim 2, characterized by the above.

9. The positions of the bolt holes in each of the multiple inner surface smooth sheets are formed to be the same as the inner surface dimensions of each of the multiple corrugated steel sheets. The inner surface smooth structure of the corrugated steel sheet according to claim 2, characterized by the above.

10. The aforementioned smooth inner surface sheet is made of a material that is resistant to degradation from ultraviolet light. The inner surface smooth structure of a corrugated steel sheet according to claim 1, characterized by the above.

11. A method for smoothing the inner surface of a corrugated steel sheet to reduce the roughness coefficient, The process involves attaching an inner surface smooth sheet, which is flexible and has bolt holes formed only at positions corresponding to the peaks of the corrugations of the corrugated steel sheet, by sandwiching it between a flat bar and the peaks of the corrugations and bolting them together. A method for smoothing the inner surface of a corrugated steel sheet, characterized by the following.

12. In the process of attaching the inner surface smoothing sheets, multiple inner surface smoothing sheets, each matching the inner surface dimensions of each corrugated steel sheet, are attached by overlapping them so that the upstream side faces the inner surface. A method for smoothing the inner surface of a corrugated steel sheet according to claim 11, characterized by the above.

13. In the process of attaching the inner surface smooth sheet, the uppermost portion of the multiple inner surface smooth sheets is fastened and secured with a band-shaped fastener that is bent according to the inner surface shape of the corrugated steel plate. A method for smoothing the inner surface of a corrugated steel sheet according to claim 12, characterized by the above.

14. In the process of attaching the inner surface smooth sheet, the inner surface smooth sheets are joined by overlapping the upstream sheet on top of the downstream sheet, and then bolting the two sheets through each other to the corrugated top of the corrugated steel plate. A method for smoothing the inner surface of a corrugated steel sheet according to claim 12, characterized by the above.

15. In the process of installing the smooth inner surface sheet, the smooth inner surface sheets are joined by overlapping the upstream sheet on top of the downstream sheet, bolting only the downstream sheet, and then overlapping and covering the bolted joint of the downstream sheet with the upstream sheet. A method for smoothing the inner surface of a corrugated steel sheet according to claim 12, characterized by the above.

16. In the process of attaching the inner surface smooth sheet, the inner surface smooth sheet is bolted to the top of the corrugation of the corrugated steel plate from one side of the inner surface using L-shaped bolts so that it can be replaced. A method for smoothing the inner surface of a corrugated steel sheet according to claim 11, characterized by the above.

17. In the above-mentioned process of attaching the inner surface smooth sheet, the side portion of the inner surface smooth sheet is fixed to the flange of the corrugated steel plate. A method for smoothing the inner surface of a corrugated steel sheet according to claim 12, characterized by the above.

18. The positions of the bolt holes in each of the multiple inner surface smooth sheets are formed to be the same as the inner surface dimensions of each of the multiple corrugated steel sheets. In the process of attaching the inner surface smoothing sheets, the inner surface smoothing sheets are joined to the same position on each of the multiple corrugated steel plates by sequentially bolting the upstream sheets onto the downstream sheets, starting from the downstream side. A method for smoothing the inner surface of a corrugated steel sheet according to claim 11, characterized by the above.

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