Structure

Abstract

To provide a structure capable of reducing man-hours required for coating.SOLUTION: The structure 1 is formed by fastening a plurality of metallic members (main girders 10, splice plates 21) to each other by a plurality of high strength bolts 31, and the high strength bolts 31 have a base material 30a made of high tensile strength steel, and a surface coating film 40 formed on a surface of the base material 30a by baking and coating and including a first coating film 41 containing a plurality of flaky zinc pieces and a second coating film 42 formed on the first coating film 41 by baking and coating and containing an epoxy resin and a plurality of flaky aluminum pieces.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to structures such as viaducts on expressways. [Background technology]

[0002] An example of a conventional structure is a bridge, particularly an overpass on a highway. The overpass has multiple main girders arranged in the direction in which the road extends, and the ends of adjacent main girders are connected via high-strength bolt friction joints (see, for example, Patent Document 1).

[0003] High-strength bolt friction joints connect adjacent main girders by placing a splice plate across the adjacent main girders and fastening the main girders and splice plate together with high-strength bolts. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-165187 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the steel frame joint structure described in Patent Document 1 does not state anything about forming a surface coating on the high-strength bolts to improve rust resistance, and when a structure fastened with such high-strength bolts is exposed for a long period of time to a corrosive environment such as salt air (salt water) or acid rain, the high-strength bolts that make up the structure will begin to rust.As this rust progresses, there is concern that the mechanical strength of the high-strength bolts will decrease, and there is also the problem that the aesthetic appearance of the structure will be impaired.

[0006] Therefore, as a means for improving the rust resistance of high-strength bolts, it is useful to form a zinc plating film on the surface of the high-strength bolt by electrogalvanizing or hot-dip galvanizing, for example.

[0007] However, electrogalvanizing is not preferable because hydrogen is generated during plating, which may be absorbed into the base material of the high-strength bolt, causing hydrogen embrittlement.

[0008] Furthermore, in the hot-dip galvanizing method, the temperature of the hot-dip galvanizing bath is about 450 to 500°C, which is higher than the heat treatment (tempering) temperature of high-strength bolts (for example, about 420°C), and this is undesirable because it may reduce the inherent mechanical strength of the high-strength bolts.

[0009] Furthermore, in the case of viaducts on expressways, which are structures, the ends of multiple main girders are fastened together with high-strength bolts to form a single unit. However, even if the surfaces of the main girders, splice plates, and high-strength bolts are each coated with an anti-rust coating, it is expected that the structure after the high-strength bolts are fastened will have many uneven and complexly shaped high-strength bolts, and that there will be areas around the high-strength bolts that are not completely covered with the anti-rust coating. Therefore, it is common practice to further paint the surface of the structure after the high-strength bolts are fastened to improve its anti-rust properties.

[0010] However, with conventional painting, a relatively thick coating must be formed to completely cover the surface of a structure, and as a result, six or more coats of paint are usually applied, resulting in poor work efficiency.

[0011] An object of the present invention is to provide a structure that can reduce the number of painting steps. [Means for solving the problem]

[0012] The structure of the present invention is a structure in which multiple metal members are integrated by fastening them together with multiple high-strength bolts, and the high-strength bolts have a base material made of high-tensile steel, and a surface coating formed on the surface of the base material by baking paint, which first coating film contains multiple scale-like zinc flakes, and a second coating film formed on the first coating film by baking paint, which second coating film contains multiple scale-like aluminum flakes, and the structure has a coating film formed by painting on the surface area including the high-strength bolts after fastening, which contains an aqueous epoxy resin and has a thickness of 175 μm or more and 235 μm or less.

[0013] In addition, in the structure according to the present invention, it is preferable that the high-strength bolt has a pintail portion that is provided at the tip of the male thread portion and that separates from the male thread portion when a torque equal to or greater than a predetermined value is applied.

[0014] In addition, in the structure according to the present invention, it is preferable that a high-concentration zinc powder paint is applied to the fracture surface between the male thread portion and the pintail portion of the high-strength bolt.

[0015] In the structure according to the present invention, the high-strength bolt is preferably a high-strength hexagon bolt. [Effects of the Invention]

[0016] According to the present invention, the first coating film prevents corrosion of the base material of the high-strength bolt, and the second coating film protects the first coating film, so that the joint part including the high-strength bolt and the outer periphery of joint part 20 are protected by the coating film.By improving the rust resistance of the high-strength bolt, it is possible to reduce the number of times it is painted, and it is also possible to reduce the labor required for painting. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a side view of a main part of a structure according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a main part of a joint according to an embodiment of the present invention. [Figure 3]FIG. 1 is a side view of a fastener according to an embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a main portion of a fastener according to one embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view of a main part of a joint portion showing another example of the fastener of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Figures 1 to 4 show one embodiment of the present invention. Figure 1 is a side view of the main part of the structure, Figure 2 is a cross-sectional view of the main part of the joint, Figure 3 is a side view of the fastener, and Figure 4 is a cross-sectional view of the main part of the fastener.

[0019] The structure 1 of the present invention is, for example, an elevated bridge on a highway, and is a steel plate girder bridge whose main components are made of steel. The structure 1 has a plurality of main girders 10 as a plurality of metal components arranged along the extension direction of the highway, and joints 20 that connect adjacent end sides of the main girders 10 to each other.

[0020] Each of the multiple main girders 10 is formed by assembling steel plates to have an I-shaped cross section. Insertion holes 10a are formed at both ends of the main girders 10 in the extension direction, through which male threads of high-strength bolts, which will be described later, are inserted.

[0021] The joint portion 20 has a splice plate 21 arranged on the side of the main girder 10 so as to span adjacent main girders 10, and a fastener 30 for fastening the end side of the main girder 10 to the splice plate 21.

[0022] The splice plate 21 is a rectangular steel plate, and has an insertion hole 21a through which the male thread portion of a high-strength bolt of the fastener 30, which will be described later, is inserted.

[0023] The fastener 30 includes a high-strength bolt 31 , a nut 32 into which the male thread of the high-strength bolt 31 is threaded, and a washer 33 disposed between the nut 32 and the splice plate 21 .

[0024] The high-strength bolt 31 is a torsion-type high-strength bolt made of high-tensile steel with improved tensile strength, and allows for control of the tightening torque. The high-strength bolt 31 has a head 31a, a male thread portion 31b extending from the head 31a, and a pintail portion 31c provided at the tip of the male thread portion 31b.

[0025] Here, a surface coating 40 is formed on the outer surface of each of the fasteners 30, namely, high-strength bolt 31, nut 32, and washer 33. The surface coating 40 is formed on the surface of the base material 30a exposed to the outside by subjecting the outer surface of each fastener 30 to a blasting process such as sandblasting and a degreasing process. As shown in Fig. 4, the surface coating 40 has a first coating film 41 containing zinc that is formed by baking paint on the surface of the base material 30a, and a second coating film 42 that is formed by baking paint on the first coating film 41 and contains epoxy resin and aluminum.

[0026] The first coating film 41 is formed, for example, by baking a paint containing a silicate resin and a plurality of flaky zinc flakes onto the surface of the base material 30a at 250°C. The first coating film 41 has a thickness dimension t1 of, for example, 9 μm. Since the first coating film 41 contains zinc, which has a greater ionization tendency than the material of the base material 30a, when a scratch occurs on the surface of the fastener 30, the zinc dissolves first, thereby providing a sacrificial anticorrosion function that suppresses the progression of corrosion of the base material 30a.

[0027] The second coating film 42 is formed, for example, by baking a paint containing epoxy resin and a plurality of scaly aluminum flakes onto the outer surface of the first coating film 41 at 200 degrees Celsius. The second coating film 42 has a thickness t2 of, for example, 4 μm. By covering the outer surface of the first coating film 41, the second coating film 42 protects the first coating film 41 and prevents scratches on the outer surface of the fastener 30.

[0028] Furthermore, when the high-strength bolt 31 fastens the end of the main girder 10 to the splice plate 21, the pintail portion 31c is broken and separated from the male thread portion 31b. A high-concentration zinc powder paint, known as a water-based organic zinc-rich paint, is applied to the fracture surface of the male thread portion 31b.

[0029] In addition, a wax containing a polymer compound and a surfactant is applied to the female thread portion of the nut 32 on top of the above-mentioned surface coating 40, making it easier to fit the nut 32 onto the male thread portion 31b of the high-strength bolt 31.

[0030] At the installation site, the structural body 1 having the above configuration is installed by inserting the male threaded portion 31b of the high-strength bolt 31 into the insertion hole 10a of the main girder 10 and the insertion hole 21a of the splice plate 21, inserting a washer 33 into the tip of the male threaded portion 31b, and screwing in the nut 32. This forms joints 20 between adjacent main girders 10, connecting multiple main girders 10. Because the outer peripheral portions of the joints 20 in the main girders 10 of the structural body 1 and the joints 20 including the fasteners 30 have complex shapes with many irregularities, a coating is further formed by painting at the installation site. The coating is formed with a thickness of 175 μm to 235 μm and contains a water-based epoxy resin. This prevents rust from forming on the outer peripheral portions of the joints 20 in the main girders 10 and on the joints 20.

[0031] As long as the coating film contains an aqueous epoxy resin, it may be, for example, a laminate of a coating film made of an aqueous epoxy resin paint and a coating film made of an aqueous fluororesin paint. Alternatively, the coating film may be formed by applying multiple coats of aqueous epoxy resin paint one on top of the other. For example, the coating film may be formed by applying two undercoats containing an aqueous epoxy resin paint to a thickness of 60 μm, applying an intermediate coat containing an aqueous epoxy resin paint to a thickness of 30 μm on the outer surface of the undercoats, and then applying a top coat containing an aqueous fluororesin paint to a thickness of 25 μm on the outer surface of the intermediate coat.

[0032] Here, the results of a salt spray resistance test in which the above-mentioned structure 1 was continuously sprayed with salt water will be described.

[0033] The salt spray resistance test was a neutral salt spray test as specified in JIS Z 2371. In the salt spray resistance test, neutral salt water with a sodium chloride concentration of 5% was continuously sprayed onto the structure 1 for 2016 hours in an environment of 35 degrees Celsius.

[0034] As a result of the salt spray resistance test, it was confirmed that the structure 1 including the high-strength bolts 31 did not rust even after 2000 hours had passed, and had high rust resistance.

[0035] Thus, according to the structure of this embodiment, a structure 1 is formed by integrating multiple metal components (main girder 10, splice plate 21) by fastening them together with multiple high-strength bolts 31, and the high-strength bolt 31 has a base material 30a made of high-tensile steel, and a surface coating 40 formed on the surface of the base material 30a by baking paint and consisting of a first coating film 41 containing multiple scale-like zinc flakes, and a second coating film 42 formed on the first coating film 41 by baking paint and containing multiple scale-like aluminum flakes, and the structure 1 has a coating film formed by painting on the surface area including the high-strength bolt 31 after fastening, which is 175 μm or more and 235 μm or less and contains an aqueous epoxy resin.

[0036] As a result, the first coating film 41 prevents corrosion of the base material 30a of the high-strength bolt 31, and the second coating film 42 protects the first coating film 41, and the surface area including the high-strength bolt 31 is protected by the coating film.By improving the rust resistance of the high-strength bolt 31, it is possible to reduce the number of times it is painted, and therefore the labor required for painting can be reduced.

[0037] Moreover, it is preferable that the high-strength bolt 31 has a pintail portion 31c provided at the tip of the male thread portion 31b, which separates from the male thread portion 31b when a torque equal to or greater than a predetermined value is applied.

[0038] As a result, when the nut 32 is screwed onto the male threaded portion 31b of the high-strength bolt 31 and tightened with a special tool, the pintail portion 31c breaks and separates when a predetermined torque is applied, making it possible to visually confirm that the tightening torque is appropriate, making construction management easier.

[0039] In addition, it is preferable that the fracture surface between the male thread portion 31b and the pintail portion 31c of the high-strength bolt 31 is coated with a high-concentration zinc powder paint.

[0040] This makes it possible to reliably prevent corrosion on the fractured surface of the tip of the male thread portion 31b with a single coating, thereby reducing the number of painting steps required.

[0041] In the above embodiment, the main girders 10 and the splice plates 21 are fastened together by the high-strength bolts 31 at the joints 20 provided between adjacent main girders 10, but the present invention is not limited to this. For example, multiple metal members constituting a truss in a bridge may be fastened together by the high-strength bolts of this embodiment, or multiple members constituting a column of a building may be connected vertically, or columns and beams may be connected together by the high-strength bolts of this embodiment.

[0042] In addition, while the embodiment described above illustrates a torsion-type high-strength bolt having a pintail portion at the tip of the male thread portion, the present invention is not limited to this. For example, the high-strength bolt may be a high-strength hex bolt 34 having a hexagonal head portion 34a and a male thread portion 34b without a pintail portion, as shown in Fig. 5. [Explanation of symbols]

[0043] 1 structure 10 Main digit 20 Joint 21 Connection plate 30 Fasteners 30a base material 31 High-strength bolt 31b Male thread part 31c pintail 34 High strength hex bolt 40 Surface coating 41 First coating 42 Second Coating

Claims

1. A structure in which a plurality of metal members are integrated by fastening them together with a plurality of high-strength bolts, The high strength bolt is a base material made of high-tensile steel; a surface coating comprising a first coating film formed on the surface of the substrate by baking coating and containing a plurality of scale-like zinc flakes, and a second coating film formed on the first coating film by baking coating and containing an epoxy resin and a plurality of scale-like aluminum flakes; The structure is provided with a coating film having a thickness of 175 μm or more and 235 μm or less, which is formed by painting on a surface region including the high-strength bolt after fastening and contains an aqueous epoxy resin. structure.

2. The high-strength bolt has a pintail portion provided at the tip of the male thread portion, which separates from the male thread portion when a torque equal to or greater than a predetermined value is applied. The structure of claim 1 .

3. A high-concentration zinc powder paint is applied to the fracture surface between the male thread portion and the pintail portion of the high-strength bolt. The structure of claim 2 .

4. The high-strength bolt is a hexagon bolt. The structure of claim 1 .

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