JP2017150234A - Precautionary maintenance method for existing steel bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a precautionary maintenance method for a steel bridge, by which, with respect to an existing steel bridge, working efficiency is improved and precautionary maintenance may be realized at the field at a low cost, and thereby service life is elongated so that serious accident may be prevented in advance.SOLUTION: A precautionary maintenance method for an existing steel bridge K comprises a first step where a temporary curing installation meeting with requirements for type 1 clean in a coating operation is newly constructed in the existing steel bridge K, and a second step where an operator is present in the temporary curing installation and the operator hits surface of the existing steel bridge K by a large number of shots S at a predetermined speed for improving fatigue strength.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a preventive maintenance method for an existing steel bridge.

  Currently, steel bridges to be newly constructed are subjected to peening treatment of the welded parts of each member in an environment where each member is deferred in the factory in accordance with the current regulations (Japan Road Association: Road Bridge Specification). The prevention of fatigue cracks has been implemented. For example, as a specific peening process, ultrasonic peening or hammer peening is usually employed (see, for example, Patent Document 1). In particular, the reason why the peening process is employed is that the work content is relatively simple and there is no problem of dust scattering on a large scale. As a result, fatigue cracks in the newly installed steel bridge are prevented, and the life of the steel bridge is extended.

JP 2011-106181 A

  However, regarding steel bridges built before the current regulations were enforced (before March 2002), even if the bridges were constructed in accordance with the regulations at the time, there were confirmation items regarding fatigue cracks in the regulations at the time. It is not included and is currently used as a steel bridge without any precautions against fatigue cracks. Therefore, for existing steel bridges constructed under such old laws and regulations, it must be expected that fatigue cracks will occur after many years of use. At present, the portion where the fatigue crack has occurred is treated afterwards by ultrasonic peening or hammer peening.

  Therefore, in order to respond to social demands, the present inventor shall also perform peening treatment on the entire existing steel bridge constructed under the old laws and regulations that have not been protected against fatigue cracks before the occurrence of fatigue cracks. Led to the idea of ensuring the same level of preventive maintenance as the newly constructed steel bridge.

  However, for example, Patent Document 1 proposes an effective treatment for fatigue cracks, but does not disclose any specific manner of construction on the entire existing steel bridge. Not. Here, if the work disclosed in Patent Document 1 is simply applied to the entire existing steel bridge, a huge work amount and a huge construction cost are expected. Therefore, there is no proposal for a concrete configuration among those skilled in the art to peening the existing steel bridges. Therefore, steel bridges built before the above-mentioned revision of the regulations are not yet proposed. Overall, preventive maintenance against fatigue cracks has not yet been taken.

  For reference, the shot peening process included in the peening process is known, but such a process is difficult to apply in an environment other than a factory due to the property that a large amount of fine particles are scattered, and even an entire large existing steel bridge. The idea that this is not very applicable is well rooted among those skilled in the art.

  Therefore, the present invention can improve the work efficiency and preventive maintenance on site at low cost for existing steel bridges that do not take measures against fatigue cracks under the old laws and regulations. An object is to provide a preventive maintenance method for an existing steel bridge that can prolong a life and prevent a serious accident.

  The present invention is a preventive maintenance method for an existing steel bridge, and a first process and a first process for newly constructing a temporary curing facility that satisfies the requirement of one type of keren in a painting operation with respect to an existing steel bridge, After that, a worker is placed in the temporary curing facility, and the worker hits the surface of the existing steel bridge with countless projectiles for improving fatigue strength at a predetermined speed. This is a preventive maintenance method for existing steel bridges.

  In such a configuration, innumerable projectiles are scattered in large quantities in the second step, but since the second step is executed in a temporary curing facility used with one kind of keren, the periphery of the steel bridge Does not affect the external environment. Furthermore, since the work is performed in the temporary curing facility, the operation of collecting the hit projection material becomes simple. In addition, the surface against which the projectile is hit may be a welded portion of the entire welded joint of the steel bridge, a weld toe portion or a weld heat affected zone, or may be a portion where the cross-sectional shape changes or a corroded portion, All parts where internal tensile stress may occur are included. Therefore, by adopting such a configuration, it is possible to improve fatigue strength with respect to the entire existing steel bridge, for example, to perform preventive maintenance against fatigue cracks before fatigue cracks occur, and to extend the life. . Moreover, the processing to the detail of a steel bridge is also possible compared with ultrasonic peening or hammer peening. Especially for existing steel bridges in coastal areas and cold regions where the corrosive environment is severe, the stress corrosion cracking phenomenon caused by residual hydrogen and salt damage can be suppressed.

  In the above-described configuration, after the second step, the temporary curing equipment used in the second step is continuously used, and the type of keren is changed to the surface of the steel bridge in the temporary curing facility. It is desirable to include the 3rd process of performing painting work based on it.

  By setting it as this structure, the temporary curing equipment used at the 2nd process can be continuously used as it is, and a coating operation can be performed at the 3rd process. For this reason, it is not necessary to prepare facilities such as scaffolding for each individual work, the construction work can be drastically reduced in cost, and the anticorrosion performance can be improved. It can be dramatically shortened.

  The diameter D of the projection material is preferably 50 μm ≦ D ≦ 2 mm.

  By setting it as this structure, a compressive residual stress can be effectively introduce | transduced with respect to the surface of the existing steel bridge.

  Moreover, it is desirable to include the 4th process which collect | recovers the projection material scattered in the said 2nd process with the scattered coating film after a 3rd process in the said temporary curing equipment.

  With this configuration, it is not necessary to collect the projection material immediately after the second step. Therefore, the third step can be performed immediately after the second step, and the construction period can be greatly shortened as a whole.

  Moreover, it is desirable to include the 5th process of classifying the collect | recovered coating film and the collect | recovered projection materials after the said 4th process.

  By adopting such a configuration, it becomes possible to reuse the collected projection material, for example, even when the projection material and the foreign matter including the release coating film are simultaneously collected in the fourth step, thereby reducing the cost. There are advantages you can do.

  The present invention can improve the work efficiency and preventive maintenance on site at low cost for existing steel bridges that are not protected against fatigue cracks under the old laws and regulations. Life expectancy can be prevented and serious accidents can be prevented.

It is a flowchart which shows the procedure of the preventive maintenance of the steel bridge concerning a 1st Example. It is a schematic explanatory drawing explaining the circulation type blasting apparatus concerning a 1st Example. It is explanatory drawing which cuts and shows the separation chamber concerning a 1st Example. It is a schematic explanatory drawing explaining the circulation type blasting apparatus concerning a 2nd Example.

  Hereinafter, the embodiment which materialized the preventive maintenance method of the existing steel bridge concerning the present invention is described in detail. In addition, this invention is not limited to the Example shown below, A design change is possible suitably. For example, in this embodiment, the second step of the present invention is constituted by so-called shot peening processing.

[First Example]
As shown in FIG. 1, as a preventive maintenance procedure for existing steel bridges, dust does not leak to the scaffolding that satisfies the requirements of Class 1 Keren in painting work or to the outside for steel bridges that are subject to preventive maintenance. Temporary curing equipment such as dustproof sheets will be temporarily installed. In addition, advance preparations for installing an apparatus for performing blasting are performed. Such a step (S101) constitutes the first step according to the present invention.

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

  A blast process is first performed using the grit determined in S102 (S103). Specifically, in the temporary curing facility, an operator performs peeling of a coating film or the like to be peeled off from the steel bridge and adjustment of the substrate to be ground adjusted. In addition, although the coating film, rust, etc. peeled off by the blast treatment and used grit are generated as dust, since the dustproof sheet is stretched in S101, the dust does not leak to the outside, and the dust Will accumulate at the work site.

  Subsequently, the shot determined in S102 is loaded in place of the grit to the blasting apparatus that has injected the grit, and the shot is switched to enable injection. Here, temporary scaffolding and temporary curing equipment for dust-proof sheets are used continuously without being removed.

  Then, an infinite number of shots (projection materials) are hit at a predetermined speed using a blasting device replaced with the shots on the blasted portion (that is, the base adjustment portion) formed of the ground surface formed by the blast processing. (S104). Such shot peening treatment improves the fatigue strength and stress corrosion cracking resistance of the substrate. This process constitutes the second process according to the present invention. The used shot generated by the shot peening process is accumulated as dust on the work site as it is mixed with the used grit in S103. By the way, the shot peening process may be performed on all the ground surfaces on which the blasting process has been performed, or may be performed appropriately on the periphery of the welded part, a part where the strength is uneasy, or the like.

  The shot is composed of spherical particles, and the diameter D is preferably 50 μm ≦ D ≦ 2 mm. If the diameter D is less than 50 μm, sufficient compressive residual stress cannot be applied to the steel bridge. On the other hand, if the diameter D exceeds 2 mm, the amount of plastic deformation on the surface of the steel bridge becomes excessive, and the improvement in resistance to fatigue, stress corrosion cracking, etc. becomes insufficient.

  Thereafter, the ground surface on which the blasting process and the shot peening process have been performed is confirmed (S105). Such confirmation includes not only visual confirmation but also comparison using, for example, an ISO8501 blast photo book, or roughness confirmation using a surface roughness measuring instrument. As a result, it is confirmed whether an unexfoliated coating film remains, or whether the roughness of the ground surface is within the specification, and an appropriate process is performed on an insufficient portion. For example, the base adjustment is performed using a hand tool or the like in a portion where the blasting process cannot be performed.

  In this way, the final finish coating for forming the final coating film is performed on the portion where the ground surface has been confirmed (S106). This process constitutes the third process according to the present invention. Such coating is generally applied in layers such as undercoating as an anticorrosion coating, intermediate coating for protecting the anticorrosion coating, and topcoating as the final finish coating. .

  When the painting is completed, the confirmation (S107) is performed. Such confirmation includes not only confirmation of the film thickness after the coating has dried, but also confirmation of the wet film thickness using a wetness gauge during the painting operation, for example. Further, such confirmation is performed not only after the top coat which is the final finish paint, but also during the undercoat and intermediate coats.

  When the painting operation is completed by the confirmation, the site is cleaned up (S108). Specifically, the preventive maintenance is completed by collecting the scaffold, dustproof sheet, and the like, and withdrawing the blast-shot peening injection device.

  In addition to the above procedure, a dust collecting step is executed (S110). Specifically, the used grit generated in the blasting process (S103), the used shot generated in the shot peening process (S104), and dust containing exfoliation and rust generated in each process are separated. While collecting.

  Since the collected used grit and used shot are both iron (metal) abrasives specified in JIS Z 0310: 2004, even if they collide with a steel bridge at the time of use, they are like Almandite garnet or iron slag. And can be reused. Among them, high-carbon cast steel can be reused about 600 times, and is very economical and can greatly reduce the amount of waste by separating it from foreign materials including peeled coatings and others. it can.

  Hereinafter, it is possible to inject the grit and the shot with a common device, and also to collect the used grit, the used shot, the peeled coating film, and the like, and to circulate the blasting device 1 This will be described as an example.

  As shown in FIG. 2, the circulating blast apparatus 1 includes an apparatus main body 2 that is installed adjacent to a work site α of a steel bridge K that is a work target. Furthermore, the apparatus main body 2 includes a pressure feeding hose 4, and an injector 3 is connected to the tip of the pressure feeding hose 4. Grit g and shot s are ejected from the injector 3. Moreover, the said apparatus main-body part 2 comprises the suction hose 5, and the front-end | tip of this suction hose 5 is arrange | positioned at the work site (alpha). As a result, the used grit g ′ generated at the work site α, the used shot s ′, and the dust X composed of the foreign matter D including the peeled coating film, rust, and the like can be sucked through the suction hose 5. it can. In order to prevent the dust X from leaking outside, a dustproof sheet (not shown) is stretched on the work site α, and a blower, a dust collector, and the like are also installed as appropriate.

  As shown in FIG. 2, 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 blast apparatus 1. More specifically, the grit hopper tank 10 has a function of storing grit g and used grit g ′ (hereinafter, a mixture thereof is referred to as grit G). The shot hopper tank 20 has a function of storing shots s and used shots s' (hereinafter, a mixture thereof is referred to as shot S). The grit hopper tank 10 is connected to a grit pressure tank 11 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 pressure tank 11 and the shot pressure tank 21 via a dry compressed air pipe 31. The dry compressed air supply means 30 includes an air compressor and an air dryer for supplying dry compressed air. Further, the dry compressed air pipe 31 is provided with a switching valve 32 so that the dry compressed air can be selectively supplied to the grit pressurizing tank 11 or the shot pressurizing tank 21, and shot instead of the grit. Can be loaded in such a way that it can be jetted.

  The pressure feeding hose 4 is connected to the grit pressure tank 11 and the shot pressure tank 21. And by this structure, the grit G or the shot S is injected from the injector 3 through the pumping hose 4 by the air pressure by the dry compressed air supplied from the dry compressed air supply means 30, and the steel bridge K to be operated In addition, blast processing or shot peening processing can be executed. In addition, the injection device (blast-shot peening injection device) according to the present invention is configured by the circulating blast device 1 having the functions so far.

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

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

  Here, as shown in FIG. 3, the separation chamber 40 has a channel 41 that is horizontally long and airtight, and an inlet 42 on the upstream side (left side in FIG. 3) of the channel 41. Is provided. In addition, a reflection plate 43 that is inclined with respect to the flow path direction of the flow path 41 is attached to the downstream side. Further, a discharge portion 44 is provided below the reflecting plate 43. In addition, a used grit collection unit 45 is disposed on the upstream side with respect to the discharge unit 44, and a used shot collection unit 46 is disposed on the upstream side of the used grit collection unit 45. The discharge part 44 is connected to the dust hose 51 and is connected to the air suction device 60 via the dust recovery part 50, and the air flow in the separation chamber 40 takes the suction port 42 upstream. The discharge part 44 is located downstream.

  Here, the dust X introduced into the flow path 41 from the suction hose 5 via the suction port 42 is maintained in the flow path 41 while maintaining a predetermined speed by the air suction force of the air suction device 60. move on. Then, the foreign matter D such as a peeled coating film or rust having a low specific gravity is directly discharged to the discharge portion 44 along the air flow in the flow path 41. The discharged foreign matter D is introduced into the dust collecting unit 50 through the dust hose 51 and accumulated in the dust collecting unit 50, and is discharged into the waste bag 52 at a desired timing and processed as industrial waste. .

  In addition, the used grit g ′ and the used shot s ′ are iron (metal-based) abrasives, and therefore have a high specific gravity. It goes straight according to inertia and collides with the reflector 43. At this time, the used shot s' rebounds most efficiently because it has a spherical shape as described above. On the other hand, since the used grit g 'has an angular shape, the rebound is smaller than that of the used shot s'. Based on the difference in the rebounding distance, the used grit collection part 45 is provided near the reflector 43 near the lower part of the flow path 41 and closer to the suction port 42 than the discharge part 44. The used shot collection unit 46 is provided farther from the reflector 43 (closer to the suction port 42) than the used grit collection unit 45. With this configuration, the foreign matter including the used grit g ′, the used shot s ′, and the peeled coating film by using only the air suction force of the air suction device 60 without using a mechanical operation such as a vibration sieve. It becomes possible to sort each D. The used grit g 'thus separated is returned to the grit hopper tank 10 below the sorting chamber 40 and reused. Similarly, the used shot s ′ is also returned to the shot hopper tank 20 below the sorting chamber 40 and reused. In this way, the grid G and the shot S can be circulated and used continuously.

  In addition to the configuration described above, the present invention can be modified as appropriate. For example, the switching valve 32 may be provided in the work site α so that the worker H at the work site α can perform switching operation, or may be remotely operable. Further, the injector 3 and the suction hose 5 may be separate or may be integrated (vacuum blast type). Further, the dry compressed air supply means 30 may be provided separately for the grit pressurization tank 11 and the shot pressurization tank 21, respectively. Further, the pressure feeding hose 4 may be provided separately for grit and shot. Similarly, the injector 3 may be divided into a grit and a shot. Moreover, the separation chamber 40 does not need to be disposed immediately above the grit hopper tank 10 and the shot hopper tank 20, and the position is not particularly limited. In addition, the method for realizing the airtight space in the flow path 41 is not particularly limited. For example, the hopper tanks 10 and 20 may be in an airtight state while communicating with the grit hopper tank 10 and the shot hopper tank 20, or a dedicated tank for temporarily storing the grit G or the shot S may be disposed at a desired timing. Thus, the grid G and the shot S may be supplied to the hopper tanks 10 and 20. In addition, it is desirable to be able to supply a new product when the grit amount or shot amount in the circulating blast device 1 is less than a specified value. Further, the apparatus main body 2 may be placed on a vehicle and movable, for example. Further, the separation means may have another structure, and may be separated using a centrifugal separator. Further, in the preventive maintenance method according to the present invention, if the temporary curing equipment is shared, a dedicated device that projects only the shot as a device that projects the shot, and a dedicated device that projects only the grit as the device that projects the grit Each of the devices may be used.

[Second Example]
On the other hand, a circulating blast device 81 according to another embodiment will be described below. The circulating blast device 81 uses a stainless steel grit and a stainless steel shot, and is used in an environment where salt is attached when sprayed onto a bridge or the like. The example of this another example is the same as the above example except that stainless steel grit g and shot s are used and cleaning devices 85 and 86 and drying devices 87 and 88 are provided. Therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 4, the apparatus main body portion 82 of the circulating blast apparatus 81 is provided with salt cleaning devices 85 and 86 and drying devices 87 and 88, which are arranged vertically. Specifically, a grit salt cleaning device 85 and a drying device 87 are disposed directly under the grit hopper tank 10, and a shot salt cleaning device 86 and a drying device 88 are disposed directly under the shot hopper tank 20. ing. The salt cleaning devices 85 and 86 constitute a salt cleaning means. The drying devices 87 and 88 constitute a drying means.

  The salt cleaning devices 85 and 86 perform washing with fresh water, respectively, store a predetermined amount of used grit g ′ and used shot s ′ in a predetermined tank, and eject fresh water to wash in the tank. To remove salt adhering to the surface. Thereafter, the stored used grit g 'and the used shot s' are transferred down to the drying devices 87 and 88, respectively. The drying devices 87 and 88 are for drying with hot air. The used grit g ′ and the used shot s ′ flowing down from the salt content cleaning devices 85 and 86 are stored and dried by exposing them to hot air for a predetermined time. Thereby, the water | moisture content adhering with the said salt content washing | cleaning apparatuses 55 and 56 is skipped. Thereafter, the stored used grit g ′ and the used shot s ′ are transferred to the grit pressurizing tank 11 and the shot pressurizing tank 21, respectively, and transferred.

  In the case of using such a circulation type blasting device 81 of another example, since the water is washed by the salt content washing devices 85 and 86, stainless steel having excellent corrosion resistance is used for the grit g and the shot s. Even in the grit g and the shot s of these stainless steels, the shape thereof is the same as that of the metal grinding material of the above-described embodiment, and those according to JIS Z 0310: 2004 are preferable except for the material.

  Another example of the circulating blasting device 81 described above is suitable for use in cold regions where a paint containing salt is used to prevent freezing or rust. That is, when the circulation type blasting device 81 is used for a steel bridge in a cold region, the used grit g ′ generated by the blasting process adheres to the salt contained in the paint, and further the shot peening process. There is also a concern that the used salt s ′ generated in step 1 may adhere to the salt. The used grit g ′ and the used shot s ′ are sucked together with the foreign matter D and separated in the separation chamber 40. The used grit g ′ is freed of salt attached to the surface by the cleaning device 85, and then the moisture attached by the cleaning device 85 is blown off by the drying device 87. After that, it can be used again. Similarly, the used shot s ′ is salt-removed by the cleaning device 85 and then dried by the drying device 87. After that, it can be used again. As described above, according to the circulation type blasting device 81 of another example, salt attached to the used grit g ′ and the used shot s ′ can be removed and used again, so that it can be suitably used in a cold district. .

  In addition, in this Example of another example, a salt cleaning apparatus and a drying apparatus are not limited to the structure mentioned above, It can change suitably. For example, it is also possible to apply an apparatus that can execute a salt cleaning process and a drying process in a single unit. In this apparatus, a configuration in which a belt conveyor for transfer is provided between a site where the salt content cleaning process is performed and a site where the drying process is performed is preferable. In this configuration, the salt washing process and the drying process can be sequentially performed in the process of being transferred by the belt conveyor. Further, even in the above-described another example, it is possible to adopt a configuration in which a belt conveyor is used as a transfer unit from the salt content cleaning device to the drying device. Furthermore, in the above-described another example, the salt content cleaning device and the drying device can be disposed only in the path for the used grit collection unit of the separation chamber. In this case, only the used grit with much salt content can be washed and dried to remove the salt content.

  In addition, although the shot defined in JIS Z 03120: 2004 "Blast processing method general rule for base material adjustment" is suitable as a projection material in this invention, another structure may be sufficient. Specifically, the shot is “a spherical particle having a major axis (ridge angle), a crushing surface, or other sharp surface defects and having a major axis within twice the minor axis before use”. Moreover, in JIS B 2711: 2013 “Spring shot peening”, shot peening is “improvement of fatigue strength and stress corrosion cracking resistance by hitting the surface layer of the spring with spherical hard particles at high speed. “A cold working method that gives compressive residual stress to the surface and hardens the surface.”

S shot (projection material)
K steel bridge

Claims (5)

A preventive maintenance method for an existing steel bridge,
A first step of constructing a new temporary curing facility that satisfies the requirements of Class 1 Keren in an existing steel bridge;
After the first step, an operator is placed in the temporary curing facility, and the operator hits the surface of an existing steel bridge with countless projectiles for improving fatigue strength at a predetermined speed. Two steps,
The preventive maintenance method of the existing steel bridge characterized by including this. After the second step, the temporary curing equipment used in the second step is continuously used, and the painting work is performed on the surface of the steel bridge in the temporary curing facility based on the type 1 keren. The preventive maintenance method of the existing steel bridge of Claim 1 including 3 processes. 3. The preventive maintenance method for an existing steel bridge according to claim 1, wherein the projection material has a spherical shape and a diameter D of 50 μm ≦ D ≦ 2 mm.   The said temporary curing equipment WHEREIN: The 4th process of collect | recovering the projection material scattered by the said 2nd process after the 3rd process with the scattered coating film is included in any one of Claims 1 thru | or 3. Preventive maintenance method for existing steel bridges.   The preventive maintenance method of the existing steel bridge of Claim 4 including the 5th process of classifying the collect | recovered coating film and the collect | recovered projection material after the said 4th process.

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