JP7359411B2 - Preventive maintenance method for steel bridges - Google Patents

Description

The present invention relates to a preventive maintenance method for painting the surface of a steel bridge.

Traditionally, preventive maintenance has been carried out on steel bridges, whether newly built or existing ones, to prevent the occurrence of rust, or especially for existing steel bridges, to renew coatings that have become corroded due to aging. has been done. In this way, preventive maintenance requires the removal of rust and old paint films, so in recent years it has become more common to remove rust and paint films by blasting (class 1 keren), and then apply a new coat of paint. (For example, see Patent Document 1.)

In addition, in steel bridges, the strength may vary at welded locations. For example, in the case of a steel road bridge, the entire bridge sways and vibrates when cars pass by or strong winds blow, causing fatigue cracks to form at welded areas where the strength is uneven. A problem arises in which The reality is that it costs a huge amount of money to repair such fatigue cracks.

By the way, for example, Patent Document 2 discloses a method of preventing the occurrence of cracks by applying a primer to structural discontinuities caused by welded joints of a steel structure.

Further, Patent Document 3 discloses a method for improving the fatigue performance of a welded joint in which an ultrasonic peening treatment is performed on the end face of the welded joint and the weld toe at the end of the welded joint.

If the conventional structure described above is applied to the repair of a steel bridge, it is expected that the construction period will be prolonged, and the cost will naturally be enormous. On the other hand, the inventor of the present application has proposed a maintenance painting method for steel structures in which blasting treatment and peening treatment are performed successively, as disclosed in Patent Document 4.

Japanese Patent Application Publication No. 11-207624 JP2006-102738A Japanese Patent Application Publication No. 2006-142367 JP2016-65443A

Under the above-mentioned background circumstances, the conventional construction methods had the following problems. In other words, in a curing space that is enclosed with scaffolding and boarded up to prevent dust from leaking, it is a dark place where no light can reach, making it extremely difficult to visually check the state of fatigue. It becomes complicated. Furthermore, if a peening treatment is subsequently performed on a repaired surface on which many irregularities have been formed by blasting, the irregularities formed at the relevant locations may have been formed by the peening treatment or by the blasting treatment. Another problem is that it becomes impossible to determine whether the In addition, for recently constructed steel bridges, it is possible to conduct unannounced inspections at factories etc. of the parts before construction, but for steel bridges that have already been constructed without prior inspection, Appropriate inspection methods have not been established for old steel bridges.

Therefore, the present invention provides a preventive maintenance method for steel bridges that can significantly shorten the construction period, thereby significantly reducing costs, and furthermore, can appropriately determine whether or not peening treatment has been properly performed. The purpose is to

The present invention (first invention) includes a blasting process in which grit is used as an abrasive to perform a blasting process to condition the surface of a steel bridge, and a method for improving fatigue strength of the portion targeted for surface conditioning. A preventive maintenance method for steel bridges, comprising: a peening process in which a shot peening process is performed using shot for the purpose of the blasting process, and after the blasting process and before the peening process, fluorescent light is applied to the area to be subjected to the peening process. After performing a fluorescent paint application step of applying a paint and the peening step to partially peel off the fluorescent paint applied in the fluorescent paint application step, irradiating the area to which the fluorescent paint was applied with ultraviolet rays, a coverage determination step of calculating coverage based on the fluorescent residual fluorescent paint and determining whether the coverage is equal to or greater than a predetermined reference determination value, and the calculated coverage is equal to or greater than the reference determination value. This is a preventive maintenance method for steel bridges, characterized in that the peening process is completed when the steel bridge is in use.

In the coverage determination step, if the calculated coverage is 90% or more, the peening step is completed, and if the coverage is less than 90%, the fluorescent paint application step is performed again, and then the peening step is performed again. It is desirable to have a configuration in which the coverage determination process is executed and then the coverage determination process is executed again.

Furthermore, in the coverage determination step, the calculated coverage is 90% or more, and then the fluorescent paint application step is performed again, then the peening step is performed again, and then the coverage determination step is performed again. The peening step may be completed when the calculated coverage is 90% or more again.

In such a configuration, when a steel bridge (either a new steel bridge or an existing steel bridge) is transferred from blasting to peening, the base surface formed by blasting may be However, since shot peening treatment can be performed as is, there is no need to perform each construction separately, which can effectively shorten the construction period and reduce costs. To explain in more detail, generally during blasting, scaffolding is erected and dustproof sheets are stretched to prevent dust from leaking outside, but in the present invention, such surroundings are Since peening can be performed continuously without removing equipment, there is no waste in the work process.

Furthermore, since the fluorescent paint application step is performed after the blasting step, the effectiveness of the peening treatment can be appropriately determined in the coverage determination step without being affected by the unevenness of the steel bridge surface formed in the blasting step. can do. In particular, if the coverage is 90% or more, it can be determined that the fatigue strength has been sufficiently improved, and if the coverage is less than 90%, it can be determined that the fatigue strength has not been sufficiently improved, and the fatigue strength can be determined to be improved again. Returning to the fluorescent paint application step, fatigue strength can be appropriately improved.

In addition, when calculating coverage, appropriate measurements are possible because fluorescent paint is used, which makes it easy to distinguish even in dark places such as a curing space.

Note that the preventive maintenance in the present invention includes maintenance work performed on a newly constructed steel bridge or an existing steel bridge to prevent corrosion. Further, blasting, grit, and shot are each defined in JIS Z 03120:2004 "General rules for blasting methods for substrate preparation." Specifically, blasting is ``impacting an abrasive material with large kinetic energy on the surface of the steel material to be treated, cutting and hitting the surface of the steel material finely, thereby removing oxides or deposits on the surface of the steel material, and polishing the steel material. "Cleaning and roughening the surface." Grit is a particle that, before use, has an angular shape with ridge angles, and the rounded portion is less than half of the particle size. Shot is "a spherical particle with a major axis within twice the minor axis, without any angles, fractured surfaces, or other sharp surface defects before use." Further, in the blasting process, the "abrasive material" has the same meaning as the above-mentioned "abrasive material". Furthermore, in JIS B 2711:2013 "Shot peening of springs", shot peening is defined as "improving fatigue strength and stress corrosion cracking resistance by bombarding the surface layer of a spring with near-spherical hard particles at high speed. A cold working method that applies compressive residual stress to the surface and work hardens the surface. However, the surface treatment method of shot peening performed on metal materials other than springs is common, and the shot peening applied to steel bridges in the present invention has the same content. That is, in the present invention, grit corresponds to the abrasive material used for blasting, and shot corresponds to the hard particles used for shot peening. Note that a so-called steel cut wire may be employed as the grit. Moreover, a so-called round cut wire may be employed as the shot.

Further, the present invention (second invention) is a preventive maintenance method for steel bridges, which includes a peening process of performing shot peening treatment using shot to improve fatigue strength of already painted steel bridges, After the paint film of the steel bridge is partially peeled off by the peening process, a coverage determination step of calculating coverage based on the paint film and determining whether the coverage is equal to or higher than a predetermined reference determination value. The peening process is completed when the calculated coverage is equal to or higher than the standard judgment value, and when the calculated coverage is less than the standard judgment value, the peening process is performed on the part to be performed. Then, the peening process is performed again to partially peel off the fluorescent paint applied in the fluorescent paint application process, and then the area to which the fluorescent paint was applied is removed. The steel bridge is characterized in that the coverage is calculated based on the residual fluorescent paint that irradiates with ultraviolet rays, and the peening process is completed when the calculated coverage is equal to or higher than the reference judgment value. This is a preventive maintenance method.

Here, depending on the situation at the site, it may be better to perform the blasting treatment and the peening treatment in reverse, but by adopting the above configuration, the first fluorescent paint application in the peening process of the first invention of the present invention can be performed in the opposite manner. It becomes possible to omit the process.

The steel bridge preventive maintenance method of the present invention can accurately and appropriately calculate coverage and perform preventive maintenance even in a dark place.

FIG. 2 is a flow diagram showing a procedure for preventive maintenance of a steel bridge according to an example. FIG. 2 is a schematic explanatory diagram illustrating a coverage determination process according to an example. FIG. 1 is a schematic explanatory diagram illustrating a circulating blasting device according to an embodiment.

Hereinafter, embodiments embodying the preventive maintenance method for steel bridges according to the present invention will be described in detail. Note that the present invention is not limited to the embodiments shown below, and design changes can be made as appropriate.

[First example]
(Advance preparation)
As shown in Figure 1, as a preventive maintenance (repainting) procedure for an existing steel bridge (steel structure), first scaffolding is temporarily installed on the steel bridge that is the target of preventive maintenance. At the same time, preliminary preparations are made (S101) such as installing a dustproof sheet to prevent dust from leaking to the outside, curing unpainted areas, and installing equipment for blasting and shot peening.

(investigation)
Thereafter, the type and thickness of the old paint applied to the steel bridge, the condition of the steel bridge, etc. are investigated (S102). Then, based on the survey results, the type of grit and shot to be used, the injection speed, etc. are determined. Here, the selected grit (non-spherical shape) and shot (spherical shape) are both defined in JIS Z 0310:2004.

(Blasting process)
Then, using the grit determined in S102, a blasting process is first performed (S103). Specifically, the coating film and the like to be peeled off in the steel bridge is removed and the surface condition of the portion to be surface conditioned is performed. Note that the paint film, rust, etc. that peeled off during the blasting process, and used grit are generated as dust, but since a dustproof sheet is installed in step S101, the dust does not leak outside, and the dust is removed from the work. It accumulates on the spot. Note that the blasting process is basically performed on the entire area that will be painted in the painting process described later. Moreover, the blasting process constitutes the blasting process according to the present invention.

(Fluorescent paint application process)
After the blasting process, a fluorescent paint is applied to the area to be shot peened (S104). As the fluorescent paint, for example, known fluorescent paints such as Roihi Color Neo (manufactured by Shinroihi Co., Ltd.) can be suitably used. Note that the step S104 of applying the fluorescent paint constitutes the fluorescent paint applying step according to the present invention.

Subsequently, the shot determined in step S102 is loaded into the blasting device that has sprayed the grit, and the shot determined in step S102 is loaded to enable the blasting device to spray the grit. At this point, the temporary scaffolding and dustproof sheets will continue to be used without being removed.

(peening process)
Then, shot peening treatment is performed on the blasted portion (namely, substrate adjustment portion) of the base surface formed by the blasting process using the blasting device replaced with the shot (S105). Such treatment improves the fatigue strength and stress corrosion cracking resistance of the base surface. Note that the used shot generated by the shot peening process continues to accumulate as dust at the work site, mixed with the used grit in S103. Furthermore, the fluorescent paint applied in the fluorescent paint application process also peels off when the shot is applied. Incidentally, the shot peening treatment may be performed on all the base surfaces subjected to the above-mentioned blasting treatment, or it may be performed partially on the vicinity of welding points or on areas where the strength is uncertain. Note that the shot peening treatment constitutes the peening process according to the present invention.

(Coverage determination process)
When the peening process is completed, the shot-peened area is irradiated with ultraviolet rays, and coverage is calculated based on the residual fluorescent paint that fluoresces (S106). For calculating coverage, for example, a coverage checker (a simple coverage measuring device manufactured by Toyo Seiko Co., Ltd.) can be suitably applied.

Specifically, as shown in Figure 2, the remote camera section C of the coverage checker CC is directed toward the substrate surface, and ultraviolet rays are irradiated from the tip of the remote camera section C to remove the fluorescent paint remaining on the substrate surface. The emitted fluorescence is received by the remote camera section C. Information on the received light is then displayed on the display D of the coverage checker device CC, allowing the calculated coverage to be confirmed.

In this embodiment, coverage calculation is performed twice for the same region. Specifically, the calculated coverage is 90% or more (more than the standard judgment value) (first time), then the fluorescent paint application process is performed again, then the peening process is performed again, and then the coverage is again performed. Execute the determination process. Then, when the calculated coverage is 90% or more again (second time), it is determined that compressive residual stress has been applied, the peening process is completed, and the process moves to S107. On the other hand, if a value less than 90% (less than the reference determination value) is calculated even once, it is determined that the shot peening process is insufficient and the process moves to S104. Note that the step of calculating the coverage constitutes the coverage determining step according to the present invention.

As mentioned above, by using fluorescent paint to judge coverage, it is possible to improve coverage especially in curing spaces with intricate structures such as steel bridges, and where sunlight cannot reach due to dust-proof sheets, etc. Coverage calculation can be performed appropriately. In particular, shot peening treatment is often applied to welded parts of steel materials (e.g. corners and corner parts), where visual confirmation tends to be difficult. Therefore, this configuration has a very advantageous effect.

(Basic confirmation)
After passing through the coverage determination step, a final confirmation of the base surface that has been subjected to the blasting process and the shot peening process is performed (S107). In this embodiment, since the portions subjected to the shot peening treatment have been confirmed in advance in the coverage determination process, the base material confirmation is mainly performed on the portions subjected to the blasting treatment. Such final confirmation includes not only visual confirmation, but also comparison using an ISO8501 blast photo book, or roughness confirmation using a surface roughness measuring device, for example. This allows it to be confirmed whether there is any unpeeled paint remaining or whether the roughness of the base surface is within the specifications, and appropriate treatment can be carried out on any insufficient areas. For example, in areas where blasting cannot be performed, the surface is adjusted using hand tools.

(Painting)
A final finish coating is applied to the part where the base surface has been confirmed in this way to form a final coating film (S108). In addition, such coatings are generally applied in multiple layers, such as an undercoat as a rust-preventive coating, an intermediate coat to protect the rust-preventive coating, and a topcoat as a final finishing coat. .

(Painting confirmation)
When the painting is completed, confirmation thereof is performed (S109). Such confirmation includes not only checking the film thickness after the coating has dried, but also, for example, checking the wet film thickness using a wetness gauge during the painting operation. Further, such confirmation is performed not only after the top coat, which is the final finishing coat, but also during the undercoat and intermediate coat.

(tidying up)
When the painting work is completed according to the above-mentioned confirmation, the site is cleaned up (S110). Specifically, the preventive maintenance will be completed by collecting the scaffolding, dustproof sheets, etc., and removing the blast-shot peening injection equipment.

(collect)
In addition to the above procedure, a dust collection step is executed (S111). Specifically, the used grit generated in the blasting process (S103), the used shot generated in the shot peening process (S105), and the dust containing flakes and rust generated in each process are separated. We will collect it.

The collected used grit and used shot are both iron (metallic) abrasives specified in JIS Z 0310:2004, so even if they collide with a steel bridge during use, they will not be abrasive like almandite garnet or steel slag. It does not need to be crushed and can be reused. Among them, high-carbon cast steel can be reused approximately 600 times, making it extremely economical, and by separating it from peeled paint and other foreign matter, the amount of waste can be significantly reduced. .

Below, we will explain a circulating blasting device 1 that can spray grit and shot with a common device, and can collect and separate used grit, used shot, peeled paint, etc. This will be explained as an example.

As shown in FIG. 3, the circulating blasting apparatus 1 includes an apparatus main body part 2 installed adjacent to a work site α of a steel bridge K to be worked. Further, the device main body 2 includes a pressure hose 4, and an injector 3 is connected to the tip of the pressure hose 4. The injector 3 injects grit g and shot s. Further, the device main body 2 includes a suction hose 5, and the tip of the suction hose 5 is disposed at the work site α. As a result, dust X consisting of used grit g', used shot s', and foreign matter D including peeled paint films, rust, etc. generated at the work site α can be sucked through the suction hose 5. can. In order to prevent the dust X from leaking outside, a dustproof sheet (not shown) is stretched over the work site α, and blowers, dust collectors, etc. are also installed as appropriate.

Further, as shown in FIG. 3, a grit hopper tank 10 and a shot hopper tank 20 are disposed adjacent to each other in the apparatus main body 2 of the circulating blasting apparatus 1. More specifically, the grit hopper tank 10 has a function of storing grit g and used grit g' (hereinafter, a mixture thereof will be referred to as grit G). Further, the shot hopper tank 20 has a function of storing shots s and used shots s' (hereinafter, a mixture thereof will be referred to as shots S). Furthermore, a grit pressurizing tank 11 is connected to the grit hopper tank 10 for pressure-feeding the grit G stored in the grit hopper tank 10 to the work site α. Similarly, the shot hopper tank 20 is connected to a shot pressurizing tank 21 for pressure-feeding the shot S stored in the shot hopper tank 20 to the work site α.

Further, a dry compressed air supply means 30 is connected to the grit pressurized tank 11 and the shot pressurized tank 21 via a dry compressed air pipe 31. The dry compressed air supply means 30 is composed of an air compressor and an air dryer for supplying dry compressed air. Further, the dry compressed air piping 31 is equipped with a switching valve 32, which allows dry compressed air to be selectively fed to the grit pressurizing tank 11 or the shot pressurizing tank 21, and shot instead of grit. It can be loaded and sprayed at will.

Further, the pressure feeding hose 4 is connected to the grit pressure tank 11 and the shot pressure tank 21. With this configuration, the grit G or shot S is injected from the injector 3 via the pressure hose 4 by the air pressure of the dry compressed air supplied from the dry compressed air supply means 30, and the steel bridge K to be worked on. It is now possible to perform blasting or shot peening. Note that an injection device (blast-shot peening injection device) is constituted by the circulation blasting device 1 having the conventional functions.

Dust X including used grit g', used shot s', and foreign matter D such as peeled paint film deposited at the work site α is sucked all together from one end of the suction hose 5. The dust X sucked by the suction hose 5 reaches the separation chamber 40 arranged above the grit hopper tank 10 and the shot hopper tank 20.

Further, a dust hose 51 is attached to the separation chamber 40, and a dust collection section 50 as a peelable coating film collection section is connected to the dust hose 51. Further, an air suction device 60 as a dust suction means is connected to the dust collection section 50. Therefore, the dust X can be sucked by the air suction force of the air suction device 60.

In the separation chamber 40, the dust X is separated into used grit g', used shot s', and foreign matter D including peeled paint film. The discharged foreign matter D is introduced into the dust collection section 50 via the dust hose 51, is deposited in the dust collection section 50, and is discharged into a waste bag 52 at a desired timing to be treated as industrial waste. .

In addition to the configuration described above, the present invention can be modified in design as appropriate. For example, when performing shot peening treatment using shot to improve fatigue strength on a steel bridge that has already been painted, the preventive maintenance method may be performed using the following procedure. First, after the coating film of the steel bridge is partially peeled off by the shot peening process, coverage is calculated based on the coating film. Then, it is determined whether the coverage is equal to or greater than the reference determination value, and when the calculated coverage is equal to or greater than the reference determination value, the peening step is completed. On the other hand, if the calculated coverage is less than the reference determination value, a fluorescent paint application step of applying a fluorescent paint to the area to be subjected to the peening step is performed. Then, the peening process is performed again, and after the fluorescent paint applied in the fluorescent paint application process is partially peeled off, ultraviolet rays are irradiated to the area where the fluorescent paint was applied, and the residual fluorescent paint becomes fluorescent. to calculate coverage. If the calculated coverage is equal to or greater than the reference determination value, the peening process is completed, and then the blasting process is performed. As described above, depending on the on-site situation, it may be better to perform the blasting treatment and the peening treatment in reverse, but by adopting such a configuration, the initial fluorescent paint in the peening process of the first invention of the present invention can be It becomes possible to omit the coating process.

Further, for example, the present invention (first invention) may be applied to a newly constructed steel bridge.

C Remote camera section CC Coverage checker device D Display G Grit S Shot K Steel bridge

Claims (4)

A blasting process that uses grit as an abrasive material to condition the steel bridge surface;
a peening step in which shot peening is performed on the portion to be subjected to the substrate preparation using a shot to improve fatigue strength;
A preventive maintenance method for steel bridges, including:
After the blasting step and before the peening step, a fluorescent paint application step of applying a fluorescent paint to the portion where the surface is unevenly formed by the blasting step and the portion where the peening step is to be performed;
After the peening process is performed and the fluorescent paint applied in the fluorescent paint application process is partially peeled off, the area coated with the fluorescent paint is irradiated with ultraviolet rays, and coverage is determined based on the fluorescent residual fluorescent paint. a coverage determination step of calculating and determining whether the coverage is equal to or higher than a predetermined reference determination value;
including;
The calculated coverage is
Completing the peening step when the value is equal to or higher than the reference judgment value;
If it is less than the standard judgment value, the fluorescent paint application process is executed again, then the peening process is executed again, and then the coverage judgment process is executed again.
A preventive maintenance method for steel bridges characterized by: In the coverage determination step,
If the calculated coverage is 90% or more, the peening step is completed,
2. The preventive maintenance method for steel bridges according to claim 1, wherein if the coverage is less than 90%, the fluorescent paint application step is performed again, then the peening step is performed again, and then the coverage determination step is performed again. In the coverage determination step,
If the calculated coverage is 90% or more, then perform the fluorescent paint application process again, then perform the peening process again, and then perform the coverage determination process again, so that the calculated coverage is 90% again. 3. The preventive maintenance method for steel bridges according to claim 2, wherein the peening step is completed when the above conditions are met. A preventive maintenance method for steel bridges, which includes a peening process in which a shot peening treatment is performed on an already painted steel bridge using shot to improve fatigue strength,
After the paint film of the steel bridge is partially peeled off by the peening process, a coverage determination step of calculating coverage based on the paint film and determining whether the coverage is equal to or higher than a predetermined reference determination value. including;
The peening process is completed when the calculated coverage is greater than or equal to the standard judgment value, and when the calculated coverage is less than the standard judgment value, fluorescent paint is applied to the area to be subjected to the peening process. Then, the peening process is performed again, and after the fluorescent paint applied in the fluorescent paint application process has partially peeled off, ultraviolet rays are applied to the area where the fluorescent paint was applied. Preventive maintenance of a steel bridge, characterized in that coverage is calculated based on residual fluorescent paint that fluoresces after irradiation, and the peening process is completed when the calculated coverage is equal to or higher than the reference judgment value. Construction method.

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