Method for preventing fall of high strength bolt using paint

Abstract

To provide a construction method related to a fall prevention measure for a high-strength bolt using a coating material for more easily preventing the fall of the high-strength bolt due to delayed fracture than before.SOLUTION: A method for preventing a high-strength bolt attached to a predetermined attached object from falling using a coating material, the method including a surface preparation treatment of applying a first coating material to the high-strength bolt and a surface of the attached object around the high-strength bolt, the surfaces of the high-strength bolt and the attached object having been subjected to surface preparation in advance, and a main material treatment of applying a second coating material having waterproof performance onto the first coating material after the surface preparation treatment.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a construction method for preventing high-strength bolts from falling using paint. [Background technology]

[0002] Traditionally, F11T bolts (hereafter simply referred to as "F11T") have been used as a jointing method for steel bridges and other bridges. Numerous cases of F11T bolt breakage due to delayed fracture have been confirmed, making it necessary to replace the bolts, but due to the vast amount of remaining F11T, emergency measures such as fall prevention nets and bolt caps have been implemented. However, recent inspection reports have reported numerous instances of deterioration of fall prevention nets and bolt caps over time, making their maintenance and management a burden.

[0003] Patent document 1 also discloses that an optical fiber cable is arranged in the internal axial direction of the bolt as a material that is resistant to delayed fracture and has high elongation capacity, and the optical fiber cable prevents the bolt from falling off due to delayed fracture. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-172127 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the high-strength bolt described in Patent Document 1 requires an optical fiber cable to be installed inside, resulting in a complex structure.

[0006] An object of the present invention is to provide a method for preventing high-strength bolts from falling using paint, which makes it easier than ever to prevent high-strength bolts from falling due to delayed fracture. [Means for solving the problem]

[0007] In order to solve such problems, the present invention provides a construction method for preventing high-strength bolts from falling off after they have been attached to a specified object, which includes a base treatment in which a first paint is applied to the high-strength bolt, the base of which has been prepared in advance, and the surface of the object around the high-strength bolt, and a main material treatment in which, after the base treatment, a second paint having waterproof properties is applied on top of the first paint.

[0008] In this method, the main material treatment is 1500 to 5000 g / m 2 It is preferable to apply the second coating material in the above amount.

[0009] In this method, it is preferable that the second coating material contains an isocyanate group-containing prepolymer as a resin component.

[0010] In this construction method, it is preferable that the high-strength bolts are F11T or F13T. [Effects of the Invention]

[0011] The method for preventing high-strength bolts from falling using the paint of the present invention makes it possible to prevent high-strength bolts from falling due to delayed fracture more easily than conventional methods. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flowchart showing the flow of a construction method for preventing high-strength bolts from falling using paint in this embodiment. [Figure 2] FIG. 10 is a diagram showing the surface condition of a high-strength bolt that has been treated to prevent falling. [Figure 3] 1 is a table showing the name of the paint, painting method, and application amount used in each step of a construction method for preventing high-strength bolts from falling using paint in one embodiment. [Figure 4]1 is a table showing the classification, components, and blending amounts of the second paint (a paint containing a one-component urethane resin-based waterproofing material) used in the treatment of the main material in one embodiment. [Figure 5] FIG. 1 is a diagram showing an outline of a test device for performing a drop weight test on a high-strength bolt with fall prevention measures. [Figure 6] As a comparative example, this is a chart showing the name of the paint, painting method, and application amount used in each process of repainting the splice joints on a steel bridge. [Figure 7] 1A and 1B are diagrams showing test results of a drop weight test using a testing device. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes a construction method for preventing high-strength bolts from falling using paint according to this embodiment, with reference to the drawings. Please note that the technical scope of the present invention is not limited to the following embodiment, but extends to the inventions set forth in the claims and their equivalents.

[0014] <Present Embodiment> Figure 1 is a flowchart showing the flow of a construction method (hereinafter referred to as "this construction method") for preventing high-strength bolts from falling using paint according to this embodiment. The high-strength bolts that are the target of this construction method according to this embodiment are, for example, F11T or F13T. A huge number of F11T or F13T bolts remain in steel bridges and other structures, and it is necessary to prevent these high-strength bolts from falling when they suffer delayed fracture and break.

[0015] Delayed fracture is a phenomenon in which a material subjected to a certain stress suddenly breaks after a certain period of time has passed. The fracture occurs brittlely with little apparent plastic deformation, and it is said that it is difficult to accurately predict when the material will break.

[0016] The construction method according to the present embodiment can prevent high-strength bolts used in joints of steel bridges from falling when they break due to delayed fracture. This construction method will be described below.

[0017] First, the surfaces of the steel plates that make up the steel bridge and the high-strength bolts attached to the steel plates are subjected to surface preparation (Step S11). Surface preparation involves removing rust, dust, oil, and other contaminants that have adhered to the surfaces of the steel plates and the heads of the high-strength bolts, and smoothing the surfaces.

[0018] Next, the surfaces of the high-strength bolts and the steel plate surrounding the high-strength bolts that have been subjected to surface preparation (step S11) are primed by applying a first paint (step S12). The primed surface treatment is a process for improving adhesion to the second paint used in the main material treatment (step S13).

[0019] For the surface treatment, a paint containing, for example, a water-based organic zinc-rich paint is used as the first paint, and a total of 100 to 600 g / m is applied by brush. 2 As the first paint, a paint containing a water-based organic zinc-rich paint was used, but the present invention is not limited to this, and for example, an epoxy resin paint or a urethane resin paint may be used, and the epoxy resin paint or the urethane resin paint may be either a one-component or two-component type, and may be water-based or solvent-based.

[0020] The surface preparation may be carried out in multiple coats. For example, in the first step of the surface preparation, a paint containing a water-based organic zinc-rich paint is applied with a brush at a rate of 100 to 300 g / m. 2 After the paint applied in the first step has dried and hardened, in the second step, a paint containing a water-based organic zinc-rich paint is similarly applied with a brush at a rate of 100 to 300 g / m 2 Apply in an amount of 1000 and cure.

[0021] Next, a main material treatment is carried out (step S13) in which a second paint having waterproof properties is applied over the first paint on the surface of the steel plate and the surface of the high-strength bolts that have been subjected to the surface treatment (step S12). The main material treatment carried out in step S13 is a so-called waterproof treatment. In the main material treatment, it is preferable to use a paint as the second paint that can form a coating film that is not only waterproof but also excellent in load resistance. Here, the coating film formed by the second paint has an elongation rate at break of 80% or more, preferably 130 to 1000%, and a tensile strength of 8 N / mm 2 or more, preferably 12 to 50 N / mm 2 and the tear strength is preferably 40 N / mm or more, and more preferably 60 to 200 N / mm. When such physical properties are present, the coating material also has excellent water resistance and load resistance. As a coating material capable of forming a coating film with excellent water resistance and load resistance, an oil-based coating material (non-aqueous coating material) called a one-component urethane resin waterproofing material or a two-component urethane resin paint is preferred, with a one-component urethane resin waterproofing material being more preferred. A one-component urethane resin waterproofing material or a two-component urethane resin paint contains a resin component, a pigment component, a solvent component, and an additive component, each in a predetermined proportion.

[0022] The reason for waterproofing with the second paint is to prevent hydrogen embrittlement, which is one of the causes of delayed fracture. Hydrogen embrittlement is a phenomenon in which high-strength bolts become brittle due to a reaction between the steel material of the bolt and hydrogen when used in corrosive environments such as outdoors or underwater.

[0023] For main material treatment, the total application amount is 1500 to 5000 g / m 2 For example, in the third step of the main material treatment, the second paint (a one-component urethane resin waterproofing paint or a two-component urethane resin paint) is applied with a brush at a rate of 750 to 2500 g / m 2 Then, after the paint in the third step has dried and hardened, in the fourth step, the second paint (one-component urethane resin waterproofing paint or two-component urethane resin paint) is similarly applied with a brush at an amount of 750 to 2500 g / m 2 Apply the amount of this as the second layer of the main material and allow to harden.

[0024] In this case, the main material treatment involves applying the second paint (a paint containing a one-component urethane resin waterproofing material) in a total of 1500 to 5000 g / m2 through the third and fourth steps. 2 As an example of the main material treatment, the second paint can be applied in three separate steps, with the amount applied per step being 600 to 1600 g / m. 2 By setting the total application amount to 1800~4800g / m 2 can be adjusted to.

[0025] Next, a topcoat treatment is performed (step S141) in which a paint to form a surface protective layer is applied over the second paint on the surface of the steel plate and the surface of the high-strength bolt that have been subjected to the main material treatment (step S13). The surface protective layer is formed to improve the corrosion resistance, weather resistance, etc. of the surface of the steel plate and the surface of the high-strength bolt, and generally corresponds to a primer coating film, intermediate coating film, or topcoat coating film in the paint industry. The surface protective layer may be a topcoat coating film alone, or it may be a laminate of multiple layers of primer coating films and topcoats. It may also have two or more layers of each of primer coating films, intermediate coating films, or topcoat coating films. In this specification, the paint to form the primer coating film is referred to as the third paint, the paint to form the intermediate coating film is referred to as the fourth paint, and the paint to form the topcoat coating film is referred to as the fifth paint.

[0026] The paint used to form the surface protective layer is, for example, at least one selected from the group consisting of acrylic resin paints, urethane resin paints, epoxy resin paints, chlorinated polyolefin paints, silicone resin paints, and fluororesin paints, and the paint is preferably formed into a coating film consisting of 1 to 4 layers, and may be a water-based paint, a solvent-based paint, or a solventless paint. The primer paint and intermediate paint can be provided for the purpose of improving adhesion between the main material layer and the topcoat paint, and are preferably formed from a urethane resin paint or an epoxy resin paint. The topcoat paint can be provided for the purpose of imparting weather resistance, and is preferably formed from a urethane resin paint, a silicone resin paint, or a fluororesin paint.

[0027] FIG. 2 is a diagram showing the surface condition of a high-strength bolt that has been treated with fall prevention measures using the above-mentioned method. This FIG. 2 shows the surface condition after all of the first through fifth paints have been applied and cured to the surface 31a of the steel plate and the surface of the high-strength bolt using the above-mentioned method. In the following description, the entire paint consisting of the first through fifth paints may be referred to as fall prevention paint 40. As can be seen from FIG. 2, the fall prevention paint 40 is thickly applied to the surface 31a of the steel plate and the surface of the high-strength bolt.

[0028] In this way, in the construction method of this embodiment, the second paint (a paint containing a one-component urethane resin waterproofing material or a two-component urethane resin paint) having the above-mentioned physical properties is applied in a total amount of 1500 to 5000 g / m 2 With this coating amount, the head 32h of the high-strength bolt 32 and the surface 31a (FIG. 2) of the steel plate 31 in the vicinity thereof can be coated thicker than in the past. The coating amount of the second coating material is 1600 to 4500 g / m 2 It is preferable that the thickness is 1800 to 2250 g / m 2 This makes it possible to maintain the state in which the high-strength bolt 32 is attached to the surface 31a of the steel plate 31 even if the high-strength bolt 32 breaks due to delayed fracture, and to prevent the high-strength bolt 32 from falling off.

[0029] <One Example> Figure 3 is a chart showing the name of the paint, painting method, and application amount used in each step of this method in one example. One example of the present invention will be explained below using Figure 3. In this method, in the first step of surface preparation, the first paint containing a water-based organic zinc-rich paint is applied with a brush at 250 g / m2 onto the surface of the steel plate and the surface of the high-strength bolts that have been subjected to surface preparation. 2 After the first paint has dried and hardened, in the second step, the first paint containing the water-based organic zinc-rich paint is applied with a brush at a rate of 250 g / m. 2 Therefore, in the surface preparation, a total of 500g / m is applied in two steps. 2The first paint containing the water-based organic zinc-rich paint is applied to the surface of the high-strength bolt 32 and the surface 31a of the steel plate 31 around the high-strength bolt 32, and then cured.

[0030] Next, in the third step of the main material treatment, a second paint (a paint containing a one-component urethane resin-based waterproofing material) is applied by brushing on the first paint (a paint containing a water-based organic zinc-rich paint) on the surface 31a of the steel plate 31 and the surface of the high-strength bolt 32, which have been subjected to the surface treatment. 2 After the second paint on the first main layer has dried and hardened, in the fourth step, the second paint (a paint containing a one-component urethane resin waterproofing material) is applied with a brush at a rate of 900 g / m. 2 Therefore, the main material treatment is divided into two steps, with a total of 1800g / m 2 The second paint containing the one-component urethane resin waterproofing material is applied to the surface of the high-strength bolt 32 and the surface 31a of the steel plate 31 around the high-strength bolt 32, and then cured.

[0031] Figure 4 is a chart showing the classification, components, and blending amounts of the second paint (a paint for a one-component urethane resin-based waterproofing material) used in the treatment of the main material in one embodiment. The one-component urethane resin-based waterproofing material contains a resin component, a pigment component, a solvent component, and an additive component. The resin component contains 85.5% isocyanate group-containing prepolymer and 3.5% latent hardener. The pigment component contains 5.0% titanium oxide and 0.5% silica. The solvent component contains 5.2% propylene glycol monomethyl ether acetate. The additive component contains 0.1% tin catalyst, 0.1% ultraviolet absorber, and 0.1% aminosilane coupling agent. The second paint shown in Figure 4 was applied in two steps in the treatment of the main material, totaling 1800 g / m. 2 The physical properties of the coating film formed to a thickness of 190% at break and 17N / mm 2The elongation at break, tensile strength, and tear strength were measured in accordance with JIS A 6021:2022 "Waterproof coating materials for architecture" (23°C, relative humidity 50%).

[0032] Next, in the fifth step of the topcoat treatment, the third to fifth paints are applied by brush to the second paint on the surface 31a of the steel plate 31 and the surface of the high-strength bolt 32, which have been subjected to the main material treatment, at a rate of 120 g / m. 2 Apply in an amount of 1000 and cure.

[0033] Fig. 5 is a diagram showing an outline of a test device for conducting a drop weight test on a high-strength bolt that has been treated with a fall prevention paint to prevent it from falling. A drop weight test was conducted using the test device 20 shown in Fig. 5 on a high-strength bolt 32, which was the test object in which a fall prevention paint 40 consisting of first to fifth paints had been applied to the high-strength bolt 32 and to the surface 31a of the steel plate 31 surrounding the high-strength bolt 32, to evaluate the protrusion protection performance of the high-strength bolt 32.

[0034] This test device 20 is a device for evaluating whether or not a high-strength bolt 32 has protrusion protection performance that prevents fragments of the high-strength bolt 32 from protruding and falling from the surface 31a of the steel plate 31 to which it is attached when delayed fracture occurs in the high-strength bolt 32. The test device 20 reproduces the state in which the high-strength bolt 32 protrudes from the surface 31a of the steel plate 31 when a weight 22 is dropped from above and hits the high-strength bolt 32. Therefore, the steel plate 31 and the high-strength bolt 32 are not threadedly connected, and are fixed together only by the fall-prevention paint 40.

[0035] As shown in FIG. 5 , the testing apparatus 20 includes two fixed bases 21, a weight 22, and a support base 23. The fixed bases 21 are two H-shaped steel beams spaced a predetermined distance apart to match the width of the steel plate 31. The weight 22 is, for example, a spherical or block-shaped metal mass that is dropped from a predetermined height above the fixed bases 21. The weight 22 is naturally dropped in the vertical direction indicated by arrow E from a predetermined height on the opposite side of the steel plate 31 from the fixed bases 21. The support base 23 is a cylindrical body that is arranged on the fixed bases 21 so that the weight 22 collides with the central axis of the high-strength bolt 32 when dropped. Specifically, the weight 22 is placed on the support base 23 above the fixed base 21, at a height of, for example, 32 cm from the fixed base 21. However, this is not limited to this, and the weight 22 may be dropped from a height of 32 cm from the fixed base 21 by an operator.

[0036] In the high-strength bolt 32 being the test object, the head 32h of the high-strength bolt 32 is exposed from the surface 31a of the steel plate 31. In addition, in the high-strength bolt 32, the shank 32s of the high-strength bolt 32 is inserted through a through-hole in the steel plate 31, and the shank 32s and the nut 33 attached to the end of the shank 32s are exposed from the back surface 31b. In this case, the high-strength bolt 32 is simply inserted through the through-hole in the steel plate 31 and is not screwed together, but is fixed to the surface 31a of the steel plate 31 only by the fall prevention paint 40. The thickness of the steel plate 31 is 16 mm.

[0037] In this test device 20, the formula for calculating the energy when a vertical PC steel rod protrudes was applied as the energy that protrudes from the steel plate 31 when the high-strength bolt 32 breaks due to delayed fracture. In this case, the required performance of the high-strength bolt 32 was set to be that the high-strength bolt 32 would not protrude from the surface 31a of the steel plate 31 even when a weight 22 weighing 5 kg was dropped from a support stand 23 with a height of 32 cm.

[0038] The calculation formula for energy W when the high-strength bolt 32 protrudes from the surface 31a of the steel plate 31 is given by the following formula (1). W=(N 2L) / (4EA)………………………………………………………………(1) Here, as shown in the table below, N means axial force, and for example, the standard axial force for F11T is set to 238kN, which is the design axial force x 1.1. L means the thickness of the fastening member, and is set to 85mm, which is the thickness of the fastening member for M22 (bolt diameter 22mm). E is the elastic modulus, and the elastic modulus of steel is 205kN / mm 2 A is the cross-sectional area of ​​the high-strength bolt 32, and the cross-sectional area of ​​M22 (bolt diameter 22 mm) is 380.1 mm 2 It was decided. [Table 1]

[0039] This energy calculation formula (1) can be replaced with the following formula (2) according to the law of conservation of energy. W=mgh…………………………………………………………………………………(2) m: mass of weight = 5 kg, g: gravitational acceleration (m / s 2 ), h: Fall height of the weight (mm) By modifying this equation (2), the height h to which the weight 22 is dropped in the testing device 20 can be calculated using the following equation (3). h=W / mg…………………………………………………………………………(3)

[0040] From this, the height h from which the weight 22 is dropped in the testing device 20 can be calculated to be approximately 32 cm.

[0041] In one example of this method, the main material treatment (Fig. 3) is carried out in the third and fourth steps, where a second oil-based paint called a one-component urethane resin waterproofing material is applied at a rate of 900 g / m. 2 Apply the amount of paint (first main layer) and let it harden. Then, apply 900g / m 2 This allows the fall prevention paint 40 having the above-mentioned properties to be applied to both the head 32h of the high-strength bolt 32 and the surface 31a of the steel plate 31 in a total amount of 1800 g / m2 Thus, with this application amount, it is possible to apply a thicker coating than in the comparative example (FIG. 6). Thus, with this construction method of one embodiment, even when an impact from the weight 22 is applied to the high-strength bolt 32, it is possible to prevent the high-strength bolt 32 from protruding from the surface 31a of the steel plate 31.

[0042] <Comparative Example> Figure 6 is a chart showing the name of the paint, painting method, and application amount used in each step of a conventional construction method as a comparative example. In this case, the comparative example is a conventional construction method in which only water-based paint is applied in multiple coats, without using the fall prevention paint 40 containing the second paint having the above-mentioned physical properties as in the present construction method of one embodiment. Furthermore, the conventional construction method (comparative example) can be applied not only by brush but also by spray.

[0043] In the conventional construction method (comparison example), the primer treatment is carried out in four steps from the first to fourth primer coat layers. The primer treatment is carried out by spraying or brushing a paint containing a water-based epoxy resin at 200 g / m each. 2 Apply the paint in four coats at a rate of 200g / m. 2 The coating amount must be applied in four separate steps, requiring a total of eight steps.

[0044] 7A and 7B show test results (A) and (B) of a drop weight test using the test apparatus 20. Fig. 7A shows a state in which a high-strength bolt 32 coated with fall-prevention coating 40 according to one embodiment of the present invention is subjected to an impact from a weight 22 dropped from a height of 96 cm (height h × 3), but the high-strength bolt 32 does not protrude from the surface 31a of the steel plate 31. In this way, the applicant confirmed that the high-strength bolt 32 does not protrude from the surface 31a of the steel plate 31, even when the weight 22 is dropped from a support stand 23 with a height of 96 cm (32 cm × 3) using the test apparatus 20.

[0045] Furthermore, as shown in Figure 7(B), when a high-strength bolt 32 coated with the paint used in the comparative example construction method was impacted by a weight 22 dropped from a height of 96 cm (height h x 3) in the test device 20, it was confirmed that the high-strength bolt 32 protruded from the surface 31a of the steel plate 31.

[0046] In this way, in the method of the comparative example, no main material treatment was carried out, and the paint containing the water-based epoxy resin was applied in four steps from the first to fourth undercoat layers, totaling 800 g / m 2 In one example, the coating amount of the second coating material having the above-mentioned properties was 1800 g / m 2 As a result, in the construction method of the comparative example, the high-strength bolts 32 protrude from the surface 31a of the steel plate 31 as shown in Fig. 7(B), and it is difficult to obtain the same protrusion protection performance as in the construction method of the present embodiment.

[0047] Furthermore, in the application method of this construction method of one embodiment, waterproofing treatment is performed using an oil-based second paint called a one-component urethane resin-based waterproofing material as a main material treatment, which is not used in the construction method of the comparative example, and therefore it is expected that hydrogen embrittlement, which is one of the causes of delayed fracture of high-strength bolts 32, can be suppressed.

[0048] <Other embodiments> Although a preferred embodiment has been described above, this embodiment is not limited to the above example. In this embodiment, the high-strength bolts to be applied are F11T or F13T, but the present invention is not limited to this and various other high-strength bolts, such as F10T and S10T, may also be applied.

[0049] It should be understood that those skilled in the art can make various changes, substitutions, and alterations to the present invention without departing from the spirit and scope of the present invention. The above-described embodiments and modifications may be implemented in any suitable combination within the scope of the present invention. [Explanation of symbols]

[0050] 31 Steel plate 32 High-strength bolt 40 Fall-prevention coating

Claims

1. A construction method for preventing high-strength bolts from falling using paint to prevent high-strength bolts attached to a predetermined object from falling, a surface preparation step of applying a first paint to the surface of the high-strength bolt and the surface of the object to be attached around the high-strength bolt, the surface of which has been prepared in advance; After the base treatment, a main material treatment is performed by applying a second paint having waterproof properties on the first paint. A construction method for preventing high-strength bolts from falling using paint, characterized by the above.

2. The main material treatment is 1500 to 5000 g / m ２ The second paint is applied in an amount of A construction method for preventing high-strength bolts from falling, using the paint according to claim 1.

3. The second coating material contains an isocyanate group-containing prepolymer as a resin component. A construction method for preventing high-strength bolts from falling, using the paint according to claim 1 or 2.

4. A construction method for preventing high-strength bolts from falling using the paint described in any one of claims 1 to 3, wherein the high-strength bolts are F11T or F13T.

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