Girder flange surface preparation method

Abstract

To provide a chaplet treatment method of a girder flange of a steel girder in a safe and high efficient floor slab replacing work.SOLUTION: A chaplet treatment method 1 of a girder flange removes a removing object 10 including at least any one of concrete pieces 243 attached to an upper flange 241 of a bridge girder 24 with a surface 241a exposed by removing a floor slab of a bridge beam 2, coated with an existing coating film 242, a rusting part 244 formed on the upper flange 241, and an existing coating film 242. The method comprises: a first chaplet treating step 11 of removing the removing object 10 by injecting an abrasive material 315 to the upper flange 241 by a blasting mechanism 31, and recovering the removing object 10 removed from the upper flange 241 by a first recovering mechanism 32; and a second chaplet treatment step 12 of removing the removing object 10 by irradiating the upper flange 241 with pulse laser by a pulse laser irradiation mechanism 41.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for treating the keren of a digit flange.

Background Art

[0002] In recent years, replacement work (specific renewal work) of a concrete floor slab disposed on the upper part of a steel girder has been carried out in bridges such as road bridges that have been in service for a long time. In addition, since many domestic bridges have passed 50 years or more since the start of service, or will pass within several years, replacement work of the concrete floor slab as described above is required for many bridges.

[0003] Generally, in the replacement work of the concrete floor slab of a bridge, when the steel bridge girder disposed under the existing floor slab has no problems with strength and durability due to corrosion or the like, it is often diverted without replacement. At this time, there may be deposits such as residual concrete pieces missing from the existing floor slab remaining on the upper flange surface of the bridge girder on which the existing floor slab was placed after the existing floor slab was removed. In addition, the existing coating film may peel off on the upper flange surface, and the bridge girder surface may be rusted due to long-term exposure.

[0004] Therefore, in the replacement work of the concrete floor slab, a method is generally used in which after removing the existing floor slab, keren treatment is performed to remove and clean the deposits, rusted parts, and existing coating film on the upper flange surface, and after painting the upper flange surface subjected to the keren treatment, a new floor slab is installed. Since it is required that no impurities remain between the newly installed floor slab and the upper flange, keren by an electric tool is adopted for the method of keren treatment of the upper flange surface and the type of keren that specifies the degree of surface finish.

[0005] Conventionally, the surface preparation method for the upper flange surface has mainly involved a two-step surface preparation method using power tools such as disc sanders and grinders, as well as hand tools, to remove any remaining concrete fragments, rusted areas, and existing paint films from the upper flange surface (see, for example, Patent Document 1). Furthermore, any remaining concrete fragments, rusted areas, and existing paint films that are removed from the upper flange surface by the surface preparation process and scattered around the preparation area are collected manually using a broom or similar tool, similar to the removal process described above.

[0006] Another surface preparation method involves using a vacuum blasting device, which removes remaining concrete fragments, rusted areas, and existing paint films from the upper flange surface by blasting with fine-grained abrasive material such as sand, and then sucks up and collects the removed material using a vacuum device. Non-patent document 1 proposes a vacuum blasting device that is equipped with an automatically swinging blasting device and a vacuum device that automatically collects the abrasive material sprayed by the blasting device and the removed surface preparation debris, and which can be moved manually on the bridge girder. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-176420 [Non-patent literature]

[0008] [Non-Patent Document 1] Obayashi Corporation, Flange Blaster™, September 20, 2019, [Retrieved September 3, 2021], Internet<URL https: / / www.obayashi.co.jp / solution_technology / detail / tech_d222.html> [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, existing coatings on bridge girders may contain harmful substances such as lead, chromium, and PCBs. In this case, there are concerns about exposure to the existing coatings during the surface preparation work, such as through the use of power tools and hand tools, and the resulting impact on the health of workers. Furthermore, the use of power tools and hand tools, as well as the spraying of abrasive materials, during the surface preparation work may generate sand and dust, which may spread to the surrounding area, raising concerns about the health of workers and the safety of the work environment. Therefore, there is a challenge in developing a surface preparation method that ensures the health of workers from harmful substances contained in the existing coatings, as well as the health of workers from sand and dust that may be generated at the work site, and that provides a safe work environment.

[0010] Conventional manual surface preparation methods require a large amount of time and effort to prepare the upper flange surface for each cycle of replacing an existing deck slab, due to the small amount of work done per unit time. Furthermore, conventional manual surface preparation methods generate significant noise when using power tools to scrape the upper flange surface, which can limit daily working hours due to noise concerns for neighbors. As a result, there is a problem of longer construction periods for deck slab replacement projects.

[0011] Furthermore, conventional manual surface preparation methods have the drawback that, because they rely on the manual work of each individual worker, variations in the skill level of each worker can lead to inconsistencies in the surface preparation.

[0012] One challenge with vacuum blasting is that abrasive material and materials removed from the upper flange surface can be scattered around after being sprayed onto the upper flange surface, requiring additional time and effort to collect these scattered materials.

[0013] Furthermore, in the surface preparation method using a vacuum blasting device, depending on the degree of deterioration of the upper flange, if abrasive material is sprayed onto the corners of the upper flange surface, the abrasive material and removed harmful substances may scatter through the gaps in the corners. This presents a challenge, as it may require adjusting the amount of abrasive material sprayed and installing protective measures around the corners to prevent scattering, potentially increasing the workload and working time.

[0014] Furthermore, concrete bridge deck replacement projects often involve large-scale traffic restrictions, such as alternating traffic flow by shifting one lane to the opposite lane to ensure two-way traffic, which are implemented for almost the entire duration of the construction. Because such traffic restrictions have a significant impact on traffic volume around the construction site, there is a challenge in shortening the construction period and minimizing the impact on traffic flow.

[0015] Based on the issues mentioned above, there is a potential problem with the health and safety of workers involved in surface preparation work during deck replacement, as well as a potential decrease in the efficiency of the surface preparation work.

[0016] Therefore, the present invention aims to provide a safe and highly efficient method for surface preparation of the girder flanges of steel girders in deck slab replacement work. [Means for solving the problem]

[0017] To achieve the above objective, the girder flange surface preparation method according to the present invention is a surface preparation method for a girder flange that removes objects to be removed, which include concrete fragments adhering to the upper flange of a bridge girder whose surface exposed by removing the bridge deck is painted with an existing coating, rusted areas formed on the upper flange, and at least one of the existing coating, and comprises a first surface preparation step of spraying an abrasive material onto the upper flange with a blasting mechanism to remove the objects to be removed, and recovering the objects removed from the upper flange with a first recovery mechanism, and a second surface preparation step of irradiating the upper flange with a pulsed laser with a pulsed laser irradiation mechanism to remove the objects to be removed.

[0018] With the above configuration, in the first surface preparation process, the first recovery mechanism reduces the generation of sand and dust from blasting work and the scattering of abrasive material and removed material from the upper flange. Therefore, even when the existing coating in the removed material contains harmful substances such as lead, chromium, and PCBs, this surface preparation method for girder flanges ensures the health of workers and a safe working environment. Furthermore, by incorporating a second surface preparation process, the spray range and amount of abrasive material used in the surface preparation process can be reduced, and the surface preparation process using the second process can be carried out without generating any flying debris. As a result, the generation of flying debris from all surface preparation areas can be reduced. When the existing coating contains hazardous substances such as lead, chromium, or PCBs, the amount of waste generated from specific controlled work can be suppressed, making it possible to implement a surface preparation method for girder flanges that further reduces the impact on the health of workers and the safe working environment. Furthermore, by incorporating both a first and second surface preparation process as part of the girder flange surface preparation method, the surface preparation work on the upper flange can be carried out by a nearly automated mechanism with minimal human intervention. As a result, the speed of the surface preparation work is improved, and the working time for surface preparation of the upper flange, which is a time-limited task, can be shortened. Therefore, the work efficiency of the surface preparation work on the upper flange can be improved. Furthermore, by using both the first and second surface preparation processes in combination as a surface preparation method for girder flanges, it is possible to suppress the occurrence of areas that were missed during construction and thus improve the efficiency of the surface preparation work.

[0019] Furthermore, in the above-described girder flange surface preparation method, in the second surface preparation step, the pulsed laser irradiation mechanism may be applied to areas where it is feared that the abrasive material and the object to be removed will scatter if the blast mechanism is applied, and the object to be removed present in those areas may be removed.

[0020] With the above configuration, by setting the areas where scattering of the grinding material or the removed debris is a concern when performing the chamfering process by the blasting mechanism as the target areas of the second chamfering process, it is possible to suppress the scattering of the debris from the chamfering process around the upper flange. Therefore, it is possible to omit the collection work of the debris including areas other than the working floor of the chamfering process and shorten the working time, and the working efficiency of the chamfering process can be further improved. Examples of the areas where scattering is a concern include the ends in the direction perpendicular to the horizontal direction in the traveling direction of the bridge on the upper flange surface, etc.

[0021] Also, in the above chamfering method for the flange, in the first chamfering process, the first collection mechanism may include a classification mechanism for classifying the removed objects collected according to the particle size, and the removed objects may be separated according to the particle size during the collection process.

[0022] With the above configuration, it is possible to easily separate the concrete pieces and the grinding material in the removed objects collected by the first collection mechanism in the first chamfering process. Therefore, the first chamfering process can prevent the mixing of concrete pieces when reusing the collected grinding material, and can be a chamfering process that circulates and uses the grinding material.

[0023] Also, in the above chamfering method for the flange, in the second chamfering process, the removal of the removed objects existing on the upper flange and the collection of the removed objects may be performed substantially simultaneously by a laser suction unit in which the pulse laser irradiation mechanism and the second collection mechanism for collecting the removed objects removed from the upper flange by the irradiation of the pulse laser are integrated.

[0024] With the above configuration, in the second chipping process, removal and recovery from the upper flange of the object to be removed can be performed substantially simultaneously, so that the working efficiency of the second chipping process can be further improved. In addition, since it is possible to prevent the object to be removed removed from the upper flange by the irradiation of the pulsed laser from scattering around, it is possible to perform the chipping process in consideration of the health of the worker and a safe working environment. Further, the second chipping process can be carried out without requiring the work of collecting the scattered matter after the removal of the object to be removed.

Effect of the Invention

[0025] According to the present invention, it is possible to provide a chipping method for the girder flange of a steel girder in a safe and highly efficient floor slab replacement work.

Brief Description of the Drawings

[0026] [Figure 1] It is an explanatory view showing an example of a bridge (road bridge) to which the chipping method for the girder flange according to the embodiment of the present invention is applied. [Figure 2] It is an explanatory view showing a state in which an existing floor slab in a road bridge to which the chipping method for the girder flange according to the embodiment of the present invention is applied has been removed. [Figure 3] It is an explanatory view of the first chipping process in an example of the chipping method for the girder flange according to the embodiment of the present invention. [Figure 4] It is a top view of the blasting mechanism from the viewpoint of A in FIG. 3. [Figure 5] It is a side view of the blasting mechanism from the viewpoint of B in FIG. 3. [Figure 6] It is an explanatory view of the second chipping process in an example of the chipping method for the girder flange according to the embodiment of the present invention. [Figure 7] It is an explanatory view showing the working situation of the chipping process in an example of the chipping method for the girder flange according to the embodiment of the present invention, (a) shows the working situation of the first chipping process 11, and (b) shows the working situation of the second chipping process 12.

Mode for Carrying Out the Invention

[0027] The following describes the girder flange surface treatment method 1 according to an embodiment of the present invention, based on Figures 1 to 7. In this embodiment, the surface preparation method 1 for girder flanges used in the deck replacement work of bridge 2 shown in Figure 1 will be described below (hereinafter, "surface preparation method 1 for girder flanges" will be referred to as "surface preparation method 1"). Bridge 2 is, for example, a road bridge erected on an expressway (hereinafter, "bridge 2" will be referred to as "road bridge 2"). In this embodiment, the direction of travel of road bridge 2 is defined as the bridge axis direction, and the width direction of road bridge 2 perpendicular to the bridge axis direction in a plan view is defined as the bridge width direction.

[0028] The road bridge 2 is a known girder bridge. That is, the superstructure 20 of the road bridge 2 before construction is carried out comprises existing pavement 21, existing deck waterproofing layer 22, existing deck slab 23, and multiple steel bridge girders 24. Multiple bridge girders 24 are arranged at predetermined intervals in the bridge width direction and multiple bridge girders are arranged at predetermined intervals in the bridge axis direction, with the bridge piers in between. The road bridge 2 has a configuration in which the existing deck slab 23 is placed on the upper surface 241a of each upper flange 241 of the multiple bridge girders 24, and the existing deck waterproofing layer 22 and existing pavement 21 are provided on top of the existing deck slab 23. The bridge girders 24 are made of known H-shaped steel members whose entire surface is painted.

[0029] The surface preparation method 1 is applied to the upper surface 241a of the upper flange 241, which is exposed as shown in Figure 2, when the existing deck slab 23 of the road bridge 2 is removed during replacement work of the existing deck slab 23. In the replacement work of the existing deck slab 23, a full scaffolding is erected to protect the space between the bridge girders 24 at the target location and serve as a work platform for the work, and a work platform 201 is formed on the bridge girders 24, allowing work to be done with the existing deck slab 23 removed. After the full scaffolding is erected, the existing pavement 21, existing deck slab waterproofing layer 22, and existing deck slab 23, which are located above the bridge girders 24 in the superstructure 20, are removed to expose the upper surface 241a of the upper flange 241. After the upper surface 241a is exposed, surface preparation is performed on the upper surface 241a of the upper flange 241 using the surface preparation method 1.

[0030] After the surface preparation of the upper flange 241 is completed, the prepared upper surface 241a is newly painted to form a new coating, the new deck slab is placed on the bridge girder 24, and the new deck slab waterproofing layer and new pavement are constructed on the new deck slab. In this embodiment, the existing deck slab 23 and the new deck slab are made of reinforced concrete. Alternatively, the existing deck slab 23 and the new deck slab may be made of precast concrete. After the surface preparation of the upper flange 241 is completed, the corners of the upper flange 241 may be rounded to form a new coating.

[0031] The existing deck slab 23 is removed, and the exposed upper surface 241a of the upper flange 241 is painted with the existing coating 242. On the upper surface 241a, there are residual concrete fragments 243 that were missing from the existing deck slab 23 when the existing deck slab 23 was removed, adhering to the upper surface 241a to a thickness of about 2-3 cm, as well as rusted areas 244 that have formed on the upper surface 241a due to the aging deterioration of the bridge girder 24, which have formed on the existing coating 242. The surface preparation method 1 is a flange treatment method that removes and cleans the above-mentioned residual concrete fragments 243, rusted areas 244, and the existing coating 242 on the upper surface 241a, making the upper surface 241a a clean surface free of impurities, and roughening the surface shape of the upper surface 241a to improve the adhesion of the new coating. In this embodiment, the existing coating 242, residual concrete fragments 243, and rusted areas 244 are collectively referred to as the object to be removed 10.

[0032] In the surface preparation method 1, all objects to be removed 10 present on the upper surface 241a are removed without leaving any residue. In this embodiment, the surface preparation method 1 is carried out using a type 2 surface preparation that finishes the surface to the extent that the steel surface is exposed. The surface preparation method 1 comprises a first surface preparation step 11 shown in Figures 3 to 5 and a second surface preparation step 12 shown in Figure 6.

[0033] The first surface preparation process 11 is carried out by a vacuum blasting apparatus 3 equipped with a blasting mechanism 31 and a first recovery mechanism 32, as shown in Figures 3 to 5. The vacuum blasting apparatus 3 according to this embodiment is a vacuum blasting apparatus equipped with a known removal mechanism and recovery mechanism, and is movable by human power.

[0034] The blasting mechanism 31 comprises a spray unit 311, a blasting hose unit 312, a pressurized tank 313, and a cleaning brush 314. The first recovery mechanism 32 comprises a recovery hose unit 321, a recovery tank 322, a dust collection hose unit 323, a dust collection unit 324, a capture filter 325, and an exhaust unit 326.

[0035] The vacuum blasting device 3 includes an air supply unit 33 that supplies compressed air 331 into the blasting mechanism 31 and the first recovery mechanism 32, and a power supply unit 34 that is electrically connected to the air supply unit 33 and drives the air supply unit 33. The air supply unit 33 is, for example, a known air compressor connected to a pressurized tank 313. The power supply unit 34 is a known generator that can be installed at the construction site of the deck replacement work.

[0036] In the first surface preparation step 11, the blasting mechanism 31 sprays abrasive material 315 onto the upper surface 241a of the area to be prepared in the first surface preparation step 11. The abrasive material 315 is a known sandblasting material. The spraying section 311 has an opening shape that covers the upper surface 241a of the area to which the abrasive material 315 is sprayed. One end of the blast hose section 312 penetrates the top 311a of the spraying section 311 and connects to the spraying section 311, and the spraying section 311 is provided with a spray nozzle 311b that sprays the abrasive material 315 in close proximity to the upper surface 241a.

[0037] The pressurized tank 313 stores the abrasive material 315, and has a first openable / closable opening 316 at its lower end that connects to the blast hose section 312, and a second openable / closable opening 317 at its upper end that connects to the recovery tank 322. The lower end of the pressurized tank 313 is connected to the middle section of the blast hose section 312, the upper end of the pressurized tank 313 is connected to the recovery tank 322, and the side wall section close to the top of the pressurized tank 313 is connected to the blast hose section 312 closer to the connection with the pneumatic supply section 33 than to the connection with the lower end.

[0038] The pneumatic supply unit 33 is connected to the pressurized tank 313 via the first connection unit 332 and to the recovery tank 322 via the second connection unit 333, and the supply of pressurized air 331 is controlled by operating the control panel 334. For example, when spraying the abrasive material 315 described later, compressed pressurized air 331 is sent to the pressurized tank 313 via the first connection unit 332. Also, when the object to be removed 10 described later reaches the recovery tank 322, pressurized air 331 is sent to the recovery tank 322 via the second connection unit 333.

[0039] In the blasting mechanism 31, the first opening / closing port 316 is opened and pressurized air 331 is supplied, causing the abrasive material 315 stored in the pressurized tank 313 to reach the spraying section 311 through the blasting hose section 312. When the abrasive material 315 reaches the spraying section 311, it is sprayed at high pressure from between the abrasive brushes 314 provided in the spraying port 311b, abrasively cleaning the object to be removed 10. Through the above mechanism, the object to be removed 10 is removed from the upper surface 241a. The upper surface 241a from which the object to be removed 10 has been removed is cleaned by the abrasive brushes 314, becoming a clean surface free of impurities. The object to be removed 10 and the sprayed abrasive material 315 removed from the upper surface 241a are sucked up and collected by the first recovery mechanism 32. The abrasive brushes 314 are hard brushes that are always in contact with the upper surface 241a during the first surface preparation process 11.

[0040] In the first recovery mechanism 32, the abrasive material 315 sprayed by the blast mechanism 31 and the object to be removed 10 removed from the upper surface 241a by the abrasive material 315 are sucked up and recovered. The recovery hose section 321, through which the object to be removed 10 and the abrasive material 315 are recovered and moved, has one end connected to the spray section 311. The other end of the recovery hose section 321 is connected to the recovery tank 322. The lower end of the recovery tank 322 is connected to the pressurized tank 313 via the second opening / closing port 317. The recovery tank 322 is connected to the lower end of the dust collection section 324 via the dust collection hose section 323. The dust collection section 324 is provided with a capture filter 325 and an exhaust section 326 above the connection point with the dust collection hose section 323. The dust collection mechanism of the recovery tank 322 may be, for example, a known cyclone type air filter having a filter with performance such as a desired particle removal rate.

[0041] The first recovery mechanism 32 further includes a classification mechanism 35 in the middle of the recovery hose section 321. The classification mechanism 35 includes a gravel removal unit 351 and a small piece sorting unit 352.

[0042] Multiple gravel removal units 351 are provided between the spraying unit 311 and the small piece sorting unit 352. The multiple gravel removal units 351 classify the remaining concrete fragments 243 in the object to be removed 10 from the abrasive material 315 and object to be removed 10 sucked up from the spraying unit 311 multiple times, and recover the larger particle sizes. The abrasive material 315 and object to be removed 10 that have passed through the multiple gravel removal units 351 are sent to the small piece sorting unit 352. The gravel removal units 351 are traps that separate and classify objects based on their weight, for example, as they pass through the recovery hose section 321.

[0043] The small piece sorting unit 352 separates the abrasive material 315 and the object to be removed 10 that have passed through the gravel removal unit 351 into dust in the abrasive material 315 and the object to be removed 10 and small pieces in the object to be removed 10 that have passed through the gravel removal unit 351, and collects the small pieces. The abrasive material 315 and the object to be removed 10 that have passed through the small piece sorting unit 352 are sent to the collection tank 322.

[0044] The classification mechanism 35 captures and recovers residual concrete fragments 243 with particle sizes that cannot be separated from the abrasive material 315 in the recovery tank 322 before moving the abrasive material 315 and the object to be removed 10 to the recovery tank 322. The object to be removed 10 that has passed through the classification mechanism 35 consists of residual concrete fragments 243 which are finer than the abrasive material 315, rusted parts 244, and existing paint film 242. The object to be removed 10, especially the residual concrete fragments 243, is classified by the classification mechanism 35 into gravel, pebbles, dust, etc., according to particle size, and each classified material is processed accordingly.

[0045] The abrasive material 315 and dust from the object to be removed 10 reach the recovery tank 322, where they are separated by a known cyclone-type dust collection mechanism. The recovery tank 322 is supplied with compressed air 331 from the air pressure supply unit 33.

[0046] The reusable abrasive material 315 is stored in the lower part of the recovery tank 322, stored again in the pressurized tank 313 via the second opening / closing port 317, and then moved again to the spraying section 311 by pressurized air 331 and used as an abrasive material sprayed onto the upper surface 241a.

[0047] The dust in the object to be removed 10 is sent to the dust collection hose section 323 by compressed air 331, passes through the dust collection hose section 323 and reaches the dust collection section 324, where it is captured by the capture filter 325. The compressed air 331 that has passed through the capture filter 325 becomes pure air free of impurities and is exhausted from the exhaust section 326 located above the dust collection section 324.

[0048] With the above mechanism, the first surface preparation process 11 is carried out continuously by a circulating system in which the abrasive material 315 is repeatedly sprayed onto the upper surface 241a through the second opening / closing port 317 located between the pressurized tank 313 and the recovery tank 322. As a result, dust from the remaining concrete fragments 243 and the abrasive material 315 are hardly scattered, eliminating the need for manual collection of scattered materials.

[0049] The spray unit 311 is equipped with a first moving mechanism 36 that allows it to be manually moved by the worker 5a in accordance with the worker's movement as the worker 5a performs the spraying of the abrasive material 315 in the first surface preparation process 11. The pressurized tank 313, the recovery tank 322, and the pneumatic supply unit 33 are integrated by being mounted on a base 37, and are equipped with a second moving mechanism 38 on the base 37 so as to be able to move in accordance with the first moving mechanism 36. In addition, the small piece sorting unit 352 is equipped with a third moving mechanism 353 that allows it to move in accordance with the movement of the first moving mechanism 36. With the above configuration, the vacuum blasting device 3 can be manually moved on its upper surface 241a in accordance with the worker 5a's movement of their work area. The first moving mechanism 36, the second moving mechanism 38, and the third moving mechanism 353 are, for example, casters for movement provided on the lower part of the spray unit 311, the base 37, and the small piece sorting unit 352.

[0050] The second surface preparation process 12 is performed by a laser suction unit 4, which integrates a pulsed laser irradiation mechanism 41 and a second recovery mechanism 42, as shown in Figure 6. In the second surface preparation process 12, the pulsed laser irradiation mechanism 41 irradiates the object to be removed 10 with laser light, thereby removing the object to be removed 10 from the upper surface 241a without striking the object against the upper flange 241, and the second recovery mechanism 42 suctions and recovers it. The second surface preparation process 12 is applied to areas on the upper surface 241a where the first surface preparation process 11 is difficult to apply. For example, these include the ends 241c of the upper surface 241a in the bridge axis direction and bridge width direction, the periphery of holes drilled in the upper flange 241, and protruding parts such as bolt heads that protrude from the upper flange 241.

[0051] The pulsed laser irradiation mechanism 41 includes a scanner head 411, a dust collection port 412, a transmission tube 413, a laser light oscillation unit 414, and a storage unit 415. The laser light oscillation unit 414 oscillates laser light 4a in a pulsed manner. Hereinafter, the laser light 4a emitted from the laser light oscillation unit 414 will be referred to as the pulsed laser 4a. The laser light oscillation unit 414 is electrically connected to the power supply unit d.

[0052] The second recovery mechanism 42 comprises a recovery hose section 421 and the recovery tank 322, dust collection hose section 323, dust collection section 324, capture filter 325, and exhaust section 326 of the first recovery mechanism 32. The dust collection tank 422 is electrically connected to the power supply section 34. The dust collection port 412 and the recovery tank 322 are connected via the recovery hose section 421. The second recovery mechanism 42 also includes a classification mechanism 35 in the middle of the recovery hose section 421. The classification mechanism 35 includes a gravel removal unit 351, a small piece sorting unit 352, and a third moving mechanism 353, similar to those provided in the first surface preparation process 11. The second recovery mechanism 42 is configured by replacing the recovery hose section 321 of the first recovery mechanism 32 with the recovery hose section 421, closing the first opening / closing port 316 and the second opening / closing port 317 of the blast mechanism 31, and omitting the connection configuration by the blast hose section 312.

[0053] The scanner head 411 has a lens 411a. The lens 411a has a specific focal length and is located at the tip of the scanner head 411. The lens 411a is selected according to the distance to the object being illuminated and the shape of the object being illuminated.

[0054] The dust collection port 412 is connected to the recovery hose section 421 of the second recovery mechanism 42 when the pulse laser irradiation mechanism 41 is driven. The transmission tube 413 is connected to the laser light oscillation unit 414 and the scanner head 411. The transmission tube 413 is, for example, a known fiber optic cable for laser transmission.

[0055] In the second surface preparation process 12, the laser suction unit 4 directly irradiates the object to be removed 10 on the upper surface 241a with a pulsed laser 4a. The object to be removed 10 at the end 241c targeted in the second surface preparation process 12 is composed of fine impurities and existing coatings 242, and there are areas where the laser light absorption rate is high. Furthermore, since the upper surface 241a is a steel surface, the reflectivity of the laser light is high, so some of the reflected pulsed laser 4a further irradiates the heated object to be removed 10, causing the object to be removed 10 to heat up easily.

[0056] The above mechanism promotes the absorption of the pulsed laser 4a to areas of the object to be removed 10 that have a high absorption rate of laser light, thereby increasing the absorption efficiency. By continuously irradiating with the pulsed laser 4a, the object to be removed 10 begins to peel off from the upper surface 241a. The object to be removed 10, which has begun to peel off, is further heated by continuous irradiation with the pulsed laser 4a. Subsequently, due to the difference in thermal expansion between the object to be removed 10 and the upper surface 241a, wrinkles form at the bonding surface between the two, and the object to be removed 10 peels off from the upper surface 241a.

[0057] Furthermore, the object to be removed 10, which has been detached as described above, further absorbs the reflected light from the upper surface 241a. As a result, thermal energy is continuously applied to the object to be removed 10 that has absorbed the laser light, causing it to sublimate and generate particles (fumes) that are finer than dust, causing the object to be removed 10 to detach and be removed from the upper surface 241a.

[0058] The heating effect of laser irradiation is maximized when the focal length of lens 411a matches the distance from lens 411a to the object to be removed 10 from which the laser beam is irradiated, and decreases when they do not match. Therefore, at distances where the laser beam is not in focus, even if, for example, a worker's hand is irradiated, it will cause almost no damage, thus enabling safe construction.

[0059] The remaining concrete fragments 243 have a high reflectivity of laser light and are less likely to absorb the pulsed laser 11a. Therefore, when the pulsed laser 4a is irradiated onto the existing coating 242 or rusted area 244 below and removed from the upper surface 241a, they are not decomposed into a fume-like state but are removed and recovered in the form of concrete shells.

[0060] In the second surface preparation process 12, the fume-like material to be removed 10 and the remaining concrete fragments 243 in the state of concrete shells, which have been peeled off from the upper surface 241a by the laser suction unit 4, reach the classification mechanism 35 through the dust collection port 412 and the recovery hose section 421. In the classification mechanism 35, the remaining concrete fragments 243 are captured and collected according to their particle size. The fume-like material to be removed 10 that has passed through the classification mechanism 35 reaches the recovery tank 322, passes through the dust collection hose section 323 by the air pressure supply section 33 to the dust collection section 324, and is collected by the capture filter 325. The pressurized air 331 that has passed through the capture filter 325 is exhausted from the exhaust section 326.

[0061] In the second surface preparation process 12, fumes generated by the irradiation of the pulsed laser 4a, regardless of their type (metallic, chemical, etc.), must not be exposed to the environment. Therefore, the laser suction unit 4 has a storage section 415 that surrounds the irradiation area of ​​the pulsed laser 4a and stores it from the outside. By storing the irradiation area of ​​the pulsed laser 4a, fumes generated by the irradiation of the pulsed laser 4a can be sucked up and collected without scattering into the surroundings.

[0062] The second surface preparation process 12 removes the object to be removed 10 by directly irradiating it with a pulsed laser 4a, and then sucks up and collects the generated fumes and the remaining concrete fragments 243 that are removed. Therefore, since this is not a surface preparation method that uses abrasive materials or other objects, the second surface preparation process 12 is a method that produces less flying debris.

[0063] The laser suction unit 4, through the second movement mechanism 38 and the third movement mechanism 353, allows the second recovery mechanism 42 to be moved manually on the upper surface 241a in accordance with the movement of the work area of ​​the worker 5b in the second surface preparation process 12.

[0064] Based on the above, surface preparation method 1 is a surface preparation method that uses the vacuum blasting device 3 and the laser suction unit 4 in combination. In surface preparation method 1, the removal of the object to be removed 10 and the suction and recovery of the object to be removed 10 are performed simultaneously in the first surface preparation step 11 and the second surface preparation step 12, respectively. However, if there is no concern about the scattering of the removed object to be removed 10 or abrasive material 315 during the surface preparation work, the method is not limited to the above, and the timing of the removal of the object to be removed 10 and the suction and recovery of the object to be removed 10 may be set arbitrarily.

[0065] As shown in Figure 7, in the first surface preparation step 11, the central part 241b of the upper surface 241a is prepared along the bridge axis direction of the road bridge 2. In the second surface preparation step 12, similarly, the end portion 241c of the upper flange 241 is prepared along the bridge axis direction of the road bridge 2. In the surface preparation method 1, the first surface preparation step 11 is performed as a preceding primary surface preparation, and the second surface preparation step 12 is performed as a subsequent secondary surface preparation. Thus, the surface preparation of the upper surface 241a is performed in two stages. When moving from the first surface preparation step 11 to the second surface preparation step 12, the recovery hose section 321 is replaced with the recovery hose section 421, and the recovery mechanism is moved from the first recovery mechanism 32 to the second recovery mechanism 42. In this embodiment, the end portion 241c corresponds to the peripheral edge of the upper surface 241a in plan view. In other words, the boundary areas between adjacent bridge girders 24, etc., due to bridge piers, etc., are included in the scope of the second surface preparation process 12. Furthermore, in the surface preparation work, the equipment used in the first surface preparation process 11 and the second surface preparation process 12 may be installed on the upper flange 241, or on the work platforms 201 provided on both sides of the upper flange 241 in the bridge width direction.

[0066] In the above embodiment, the power supply unit 34 may be configured such that a generator is provided in both the vacuum blasting device 3 and the laser suction unit 4. Furthermore, the first recovery mechanism 32 and the second recovery mechanism 42 may be configured independently, with common components such as the classification mechanism 35 and the recovery tank 322 provided in both.

[0067] The end portion 241c is a location where, in the vacuum blasting device 3 used in the first surface preparation process 11, there is concern that the sprayed abrasive material 315 and the removed object 10 may scatter around the upper flange 241. Furthermore, if there are other locations besides the end portion 241c where there is concern that the abrasive material 315 and the removed object 10 may scatter if the first surface preparation process 11 is applied, surface preparation will be carried out by the second surface preparation process 12. Locations other than the end portion 241c where scattering is a concern include, for example, locations close to the space around the periphery of a hole drilled in the upper flange 241.

[0068] In the first surface preparation process 11 and the second surface preparation process 12, when the object to be removed 10 is recovered by the first recovery mechanism 32 and the second recovery mechanism 42, dust and other particles generated by the spraying of abrasive material 315 and irradiation with pulse laser 4a are simultaneously sucked up and recovered in addition to the object to be removed 10.

[0069] With the above configuration, in the surface preparation method 1, the movement and starting of the vacuum blasting device 3 and the laser suction unit 4 are performed manually, while the removal, suction, and recovery of the object to be removed 10, which is the surface preparation work, are performed by a nearly automated mechanism with almost no manual work.

[0070] After the surface preparation of the upper flange 241 is completed by the first surface preparation process 11 and the second surface preparation process 12, the upper surface 241a is painted to form a new coating, the new deck slab is placed on the bridge girder 24, and the new deck slab waterproofing layer and new pavement are constructed on the new deck slab.

[0071] Next, the operation and effects of the girder flange surface treatment method 1 according to the embodiment of the present invention described above will be explained with reference to the drawings.

[0072] In the replacement work of the existing deck slab 23 shown in Figures 1 and 2, the existing deck slab 23 is removed and the upper surface 241a is treated with a surface preparation method 1. As shown in Figure 7, the surface preparation method 1 is carried out by a preceding first surface preparation step 11 and a subsequent second surface preparation step 12.

[0073] As shown in Figures 3 to 5, in the first surface preparation step 11, surface preparation is performed on the central part 241b by spraying abrasive material 315 from the spraying unit 311. The material to be removed 10 removed from the central part 241b is sucked up and collected by the first collection mechanism 32. Of the collected material to be removed 10, the classification mechanism 35 collects the remaining concrete fragments 243 with larger particle sizes, and these are separated from the abrasive material 315 by the collection tank 322. On the upper surface 241a, fine irregularities are formed by the spraying of the abrasive material 315, increasing the surface area and improving the adhesion of the new coating film.

[0074] In the first surface preparation process 11, the vacuum blasting device 3 is moved along the bridge axis direction, and surface preparation is continuously performed on the central section 241b in the bridge axis direction. In addition, the abrasive brush 314 is used to move and work on the central section 241b without leaving any fine sand, dust, or debris. The above first surface preparation process 11 is performed on the central section 241b of the upper flange 241 of all bridge girders 24.

[0075] As shown in Figure 6, in the second surface preparation step 12, the edges 241c are prepared by directly irradiating the object to be removed 10 with a pulsed laser 4a. The object to be removed 10 is continuously heated by the directly irradiated and reflected pulsed laser 4a, and peels off from the upper surface 241a. The peeled object to be removed 10 further absorbs the reflected light from the upper surface 241a and is decomposed into fine fumes. In addition, if the remaining concrete fragments 243 are removed by irradiating the lower existing coating 242 or rusted area 244 with the pulsed laser 4a, they are removed in the form of concrete shells. The removed fume-like object to be removed 10 and remaining concrete fragments 243 are sucked up and collected by the second recovery mechanism 42 and separated by the classification mechanism 35. The fume-like object to be removed 10 is collected in the dust collection tank 422.

[0076] The second surface preparation process 12 involves manually moving the laser suction unit 4 along the bridge axis direction to continuously perform surface preparation on the end portion 241c extending in the bridge axis direction. The above second surface preparation process 12 is performed on the end portion 241c of the upper flange 241 of all bridge girders 24.

[0077] Using the surface preparation method 1 described above, surface preparation is carried out on the upper surfaces 241a of all bridge girders 24. After the surface preparation is completed, the new deck slab is placed on the bridge girders 24, and a new deck waterproofing layer and pavement are installed on the new deck slab to complete the replacement work of the existing deck slab 23.

[0078] In the first surface preparation process 11, the material to be removed 10, which has been removed from the upper surface 241a by the first recovery mechanism 32 described above, is sucked up and recovered without scattering. Therefore, even when the existing coating 242 in the material to be removed contains harmful substances such as lead, chromium, and PCBs, the scattering of the material to be removed 10 is suppressed, and a surface preparation method that ensures the health of workers and a safe working environment can be achieved.

[0079] Furthermore, by including a second surface preparation process 12, the spray range, spray volume, and generation of airborne particles of the abrasive material 315 in the first surface preparation process 11 can be suppressed. When the existing coating contains harmful substances such as lead, chromium, or PCBs, the amount of specific controlled waste generated can be suppressed, thus enabling a surface preparation method that further reduces the impact on the health of workers and the safe working environment.

[0080] With the combined first surface preparation process 11 and the second surface preparation process 12 described above, the only manual work required in surface preparation method 1 is the movement of the vacuum blasting device 3 and the operation of the equipment. This surface preparation method 1 allows the surface preparation work on the upper surface 241a of the upper flange 241 to be carried out by a nearly automated mechanism with minimal human intervention. Therefore, the speed of the surface preparation work can be improved, and the time required for surface preparation of the upper flange 241, which has limited working time, can be reduced, thereby improving the efficiency of the surface preparation work on the upper flange 241. Furthermore, by carrying out the surface preparation work by a nearly automated mechanism using surface preparation method 1, the labor required for the surface preparation work can also be reduced.

[0081] The surface preparation method 1 is implemented in a two-stage configuration, with the first surface preparation step 11 being carried out first, followed by the second surface preparation step 12. This allows for multiple visual checks of the completed surface top 241a during the process. Furthermore, if any material to be removed 10 remains in the central section 241b or at the boundary between the central section 241b and the end section 241c after the first surface preparation step 11 is completed, the subsequent second surface preparation step 12 can be performed simultaneously with the end section 241c. Thus, by configuring the surface preparation method 1 in a two-stage configuration, it is possible to suppress the need for rework due to omissions in the removal, suction, or recovery of material to be removed 10 after all surface preparation steps are completed, thereby reducing additional work time and labor. As a result, the work efficiency of the surface preparation work can be further improved. In addition, since omissions in the removal, suction, and recovery of material to be removed 10 can be suppressed, a surface preparation surface free of impurities can be formed on the surface top 241a.

[0082] In the surface preparation method 1, the second surface preparation step 12 is applied to the end portion 241c, thereby avoiding the application of the first surface preparation step 11 to areas where there is concern about scattering when the abrasive material 315 is sprayed. As a result, the generation of scattered material at the end portion 241c is reduced, and the surface preparation work can be carried out without soiling the area around the end portion 241c. In addition, tasks such as collecting scattered material and cleaning can be omitted in parallel with the surface preparation work, further improving the efficiency of the surface preparation work.

[0083] In the surface preparation method 1, the first surface preparation step 11 uses a first recovery mechanism 32 to perform suction and recovery, thereby reducing the scattering of abrasive material 315, the object to be removed 10, sand dust, and fine dust caused by blasting. Furthermore, in the second surface preparation step 12, the second recovery mechanism 42 performs suction and recovery, thereby reducing the scattering of the object to be removed 10, which has been decomposed into a fume-like form by pulse laser irradiation. As described above, by performing suction and recovery of scattered materials simultaneously with the removal of the object to be removed 10 in the first surface preparation step 11 and the second surface preparation step 12, the generation of scattered materials is suppressed, and the work of collecting scattered materials as in conventional methods can be omitted, allowing for a transition to the next step. In addition, since the generation of dust and sand dust can be suppressed, the working environment can be improved.

[0084] Furthermore, in the surface preparation method 1, the recovered residual concrete fragments 243 and abrasive material 315 are classified and separated according to their particle size by a classification mechanism 35, and residual concrete fragments 243 with a particle size larger than that of the abrasive material 315 are captured by the classification mechanism 35. With the above mechanism, residual concrete fragments 243 with a large particle size in the object to be removed 10, which are difficult to separate from the abrasive material 315 in the recovery tank 322, can be reliably separated and recovered. In addition, in the first surface preparation process 11, the object to be removed 10 and abrasive material 315 can be easily separated by compressed air 331 in the recovery tank 322, preventing residual concrete fragments 243 from being mixed into the abrasive material 315 when the recovered abrasive material 315 is reused, and enabling the abrasive material 315 to be recycled.

[0085] Furthermore, the surface preparation method 1 allows for the simultaneous removal and recovery of the object to be removed 10 from its upper surface 241a in the second surface preparation process 12, thereby improving the work efficiency of the second surface preparation process 12. In addition, since the object to be removed 10 removed from its upper surface 241a is simultaneously sucked up and recovered, scattering into the surrounding area is prevented, making the surface preparation work more considerate of the health of workers and the safe working environment. Moreover, the second surface preparation process 12 can be carried out without the need for the recovery of scattered debris after the removal of the object to be removed 10.

[0086] In the surface preparation method 1, the abrasive material 315 and the object to be removed 10 are sucked up and recovered by the first recovery mechanism 32 and the second recovery mechanism 42 in the first surface preparation process 11 and the second surface preparation process 12, and this is performed simultaneously with the removal work on the upper surface 241a side of the upper flange 241, rather than the lower surface side. Therefore, the object to be removed 10 can be sucked up and recovered without scattering due to falling to the lower part of the upper flange 241, and the surface preparation work can be performed with high work efficiency without requiring recovery work to be carried out to the lower part of the upper flange 241.

[0087] Furthermore, by using the first surface preparation process 11 and the second surface preparation process 12 in combination, the working time of the first surface preparation process 11, which generates significant noise due to the operation of the blast mechanism 31, can be reduced. In addition, since the second surface preparation process 12 is performed by irradiating with a pulsed laser, there is no impact of objects being struck, and therefore no significant noise is generated. Thus, by using the first surface preparation process 11 and the second surface preparation process 12 in combination, noise reduction measures can also be taken to mitigate noise pollution around the work site.

[0088] Furthermore, since the surface preparation method 1 performs surface preparation on the end portion 241c in the second surface preparation step 12, surface preparation can be performed without applying a large load such as by spraying abrasive material 315, and breakage of the end portion 241c during the surface preparation work can be prevented.

[0089] Furthermore, in the second surface preparation process 12, the laser suction unit 4 decomposes the material to be removed 10 into fumes finer than dust and removes them from the upper surface 241a, making it easier for the second recovery mechanism 42 to recover them. In addition, the mechanism removes the material to be removed 10 on the upper surface 241a by peeling and sublimating it off the upper surface 241a due to the irradiation of a pulsed laser, so that surface preparation can be performed on the end surface 241c without any residue of the material to be removed 10.

[0090] Furthermore, in the first surface preparation step 11 and the second surface preparation step 12 of the surface preparation method 1, surface preparation is carried out on the upper surface 241a in a simple and uniform manner in the direction of the bridge axis, so there is no influence due to differences in the work ability of the workers. In addition, the surface preparation method 1 can be carried out by simple and uniform work without requiring any special skills.

[0091] Furthermore, in the second surface preparation step 12, the surface preparation work using the laser suction unit 4 allows for the irradiation of a pulsed laser without being limited by the shape of the area to be removed. The second surface preparation step 12 allows for the desired surface preparation work to be performed even on fine details such as the end portion 241c, holes drilled in the upper flange 241, and protruding parts such as bolt heads, where scattering is a concern when the first surface preparation step 11 is applied. Therefore, the second surface preparation step 12 eliminates the burden of adjusting the amount of abrasive material sprayed to suppress the scattering of harmful substances from gaps such as the corners of the upper flange 241, and the installation of scattering prevention measures around the corners, thereby improving the efficiency of the surface preparation work.

[0092] Furthermore, by using the first surface preparation process 11 and the second surface preparation process 12 in combination, the working time for surface preparation can be shortened. As a result, it becomes possible to shorten the overall construction period for the replacement of the existing deck slab 23, and to shorten the period during which large-scale traffic restrictions such as alternating traffic restrictions are implemented during the construction period, thereby minimizing the impact on traffic flow.

[0093] Although embodiments of the girder flange surface preparation method according to the present invention have been described above, the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the invention. For example, in the above embodiment, the pulse laser irradiation mechanism 41 is applied to areas where scattering is a concern in the second surface preparation step 12, but this configuration is not limited to areas where scattering around the upper flange 241 is not possible. For example, in a configuration where multiple bridge girders 24 are arranged in close proximity and parallel to each other, and there is no risk of scattering of abrasive material 315 or objects to be removed 10, the entire flat surface of the upper surface may be prepared using a vacuum blasting device, and details such as splice parts may be prepared using a laser suction unit.

[0094] In the above embodiment, the existing coating 242, the remaining concrete fragments 243, and the rusted portion 244 are collectively treated as the object to be removed 10. However, the configuration is not limited to the above and may be determined according to each surface preparation site. For example, any two of the existing coating 242, the remaining concrete fragments 243, and the rusted portion 244 may be treated as the object to be removed 10, or any one of them may be treated as the object to be removed 10. Furthermore, the objects of work in the first surface preparation process 11 and the second surface preparation process 12 are not limited to the above configuration and may be determined according to each surface preparation site. For example, the process may involve removing any two of the existing paint film 242, remaining concrete fragments 243, and rusted areas 244, or it may involve removing any one of them.

[0095] Furthermore, in the above embodiment, in the first surface preparation process 11, the vacuum blasting device 3 is equipped with a first moving mechanism 36, a second moving mechanism 38, and a third moving mechanism 353, making it movable by the operator 5a. Similarly, the laser suction unit 4 is equipped with a fourth moving mechanism 44 and a third moving mechanism 353, making it movable by the operator 5b. The above configuration is not limited to this one, however, as long as the vacuum blasting device 3 and the laser suction unit 4 can be made movable on the upper surface 241a. For example, the first moving mechanism 36, the second moving mechanism 38, the third moving mechanism 353, and the fourth moving mechanism 44 may be equipped with electric devices such as motors and electrically connected to the power supply unit 34, thereby making the vacuum blasting device 3 and the laser suction unit 4 movable by power supply.

[0096] Furthermore, in the above embodiment, a first recovery mechanism 32 is provided in the first surface preparation process 11, and a second recovery mechanism 42 is provided in the second surface preparation process 12. In addition to the above configuration, the surface preparation method 1 may have a configuration in which the two recovery mechanisms are integrated, or it may have a configuration in which the connection with the recovery mechanism is switched for each process that is carried out.

[0097] Furthermore, in the above embodiment, the vacuum blasting device 3 is equipped with a classification mechanism 35 in the first surface preparation step 11. However, if the remaining concrete fragments 243 adhering to the upper surface 241a are fine enough to be separated from the abrasive material 315 in the recovery tank 322, the first recovery mechanism 32 may be configured without a classification mechanism 35.

[0098] Furthermore, in the above embodiment, the pulse laser irradiation mechanism 41 and the second recovery mechanism 42 are integrated as a laser suction unit 4, but the pulse laser irradiation mechanism 41 and the second recovery mechanism 42 may be separate components for suctioning and recovering the object to be removed 10. Also, although the first recovery mechanism 32 provided in the vacuum blast device 3 and the second recovery mechanism 42 provided in the laser suction unit 4 are separate components, they may be the same recovery mechanism. [Explanation of Symbols]

[0099] Surface preparation method for single-girder flanges (surface preparation method) 2. Road bridges (bridge structures) 4. Laser suction unit 11. First surface preparation process 12. Second surface preparation process 23 Existing deck slab (deck slab) 24 Bridge girders 31. Blast mechanism 32 First Recovery Organization 35 Classification mechanism 41. Pulse laser irradiation mechanism 42 Second Recovery Mechanism 241 Upper flange 241a Top surface (front surface) 242 Existing coating 243 Remaining concrete fragments (concrete fragments) 244 Rusted area

Claims

1. A method for removing objects from a girder flange, comprising removing concrete fragments adhering to the upper flange of a bridge girder whose surface is exposed by removing the bridge deck and is painted with an existing coating, rusted areas formed on the upper flange, and at least one of the existing coating, wherein the girder flange is a surface to be removed. A first surface preparation step involves using a blasting mechanism to spray abrasive material onto the upper flange to remove the object to be removed, and then using a first recovery mechanism to recover the object removed from the upper flange. A second surface preparation step involves irradiating the upper flange with a pulsed laser using a pulsed laser irradiation mechanism to remove the material to be removed, Equipped with, A method for scraping girder flanges, wherein in the second scraping step, the pulsed laser irradiation mechanism is applied to areas where it is feared that the abrasive material and the object to be removed will scatter if the blast mechanism is applied, and the object to be removed present in those areas is removed.

2. In the first scraping process, the first recovery mechanism includes a classification mechanism for classifying the recovered material to be removed according to its particle size, and separates the material to be removed according to its particle size during the recovery process. The method for surface preparation of a girder flange as described in claim 1.

3. In the second surface preparation process, a laser suction unit is used, which integrates the pulsed laser irradiation mechanism and a second recovery mechanism for recovering the material to be removed from the upper flange by the irradiation of the pulsed laser. This unit allows for the removal of the material to be removed from the upper flange and the recovery of the removed material to be performed substantially simultaneously. The method for surface preparation of a girder flange according to claim 1 or 2.

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