Method for removing existing fixtures and method for widening deck slabs

Abstract

This invention provides a method for removing existing fasteners from a concrete deck slab, enabling construction in a narrow area at the edge of the deck slab without crushing the concrete, thereby minimizing the impact on the traffic lanes, and allowing for the removal of existing fasteners from the concrete deck slab. [Solution] The method for removing existing fasteners in a concrete floor slab 6 includes a temporary support step of placing a ram chair 21 at the end of the floor slab and temporarily supporting the reaction force of the tension of the existing tension member on the ram chair; a first chipping step of exposing a part of the existing tension member; a transfer step of transferring the reaction force of the tension of the existing tension member from the ram chair to an intermediate anchoring device; and a removal step of removing the ram chair and removing the existing anchoring device and a part of the exposed end of the existing tension member.

Description

Technical Field

[0001] The present invention relates to a method for removing existing fixtures in a concrete floor slab and a floor slab widening construction method for widening a concrete floor slab.

Background Art

[0002] Patent Document 1 discloses an expansion method for an existing prestressed concrete floor slab (PC floor slab) of a bridge. This method includes a step of lifting the existing PC floor slab to expose the existing tensioning material, a step of attaching an intermediate fixture to the exposed existing tensioning material, a step of removing the end portion of the existing tensioning material, and a step of placing concrete in the expansion portion of the existing PC floor slab. When lifting the existing PC floor slab, in order to suppress the crushing of the existing PC floor slab due to the tension of the existing tensioning material, a portion of the existing PC floor slab that is separated from the inner side in the bridge width direction from the end of the floor slab is lifted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an existing PC floor slab, a plurality of inner cables may be arranged to introduce prestress in the bridge axis direction. Therefore, in the method described in Patent Document 1, there is a risk that the portion where the existing PC floor slab is lifted may interfere with a part of the plurality of inner cables. When widening the PC floor slab while the vehicle is in use, it is necessary to ensure the required width of the vehicle running lane (service lane) even during regulation. In this case, since the portion where the existing PC floor slab should be lifted interferes with the vehicle running lane, there is a risk that it may be difficult to widen the PC floor slab.

[0005] In view of the above background, the present invention aims to provide a method for removing existing fasteners from a concrete deck slab, which can remove existing fasteners from a concrete deck slab without crushing the concrete and while minimizing the impact on the traffic lanes, and a deck slab widening method that can widen a concrete deck slab. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides a method for removing existing fasteners in a concrete floor slab (6) into which tension is introduced by tensioning members (8) and anchoring members (9), comprising: a temporary support step (Figure 4) in which a ram chair (21) is placed at the end of the floor slab to temporarily receive the reaction force of the tension from the existing tensioning members from the existing anchoring members to the ram chair; a first chipping step (Figure 5) in which a part of the floor slab is chipped away to expose a part of the existing tensioning members; a transfer step (Figure 6) in which, after the first chipping step, an intermediate anchoring member (41) is attached to the exposed part of the existing tensioning members to transfer the reaction force of the tension from the ram chair to the intermediate anchoring member; and a removal step (Figure 9) in which, after the transfer step, the ram chair is removed and the existing anchoring members and a part of the exposed end of the existing tensioning members are removed.

[0007] According to this embodiment, in the first chipping process, before chipping away a portion of the deck slab, and before the reaction force of the tensioning force of the tensioning members is borne by the intermediate anchoring device, it can be temporarily supported by a ram chair positioned at the end of the deck slab. Therefore, the portion of the deck slab close to the end can be chipped away without considering the crushing of the concrete portion of the deck slab caused by the reaction force of the tensioning force acting on the existing anchoring device. Thus, the existing anchoring device can be removed while minimizing the impact on the traffic lanes.

[0008] In the above embodiment, in the temporary support step, the reaction force of the tension of the existing tensioning member may be temporarily supported from the existing anchoring device to the ram chair by using a connector (20) attached to the existing anchoring device, a tension bar (19) attached to the connector, and a nut (22) attached to the tension bar and in contact with the ram chair.

[0009] In this embodiment, the reaction force of the tension of the existing tensioning member is transmitted to the floor slab via the existing anchoring fixtures, connectors, tension bars, nuts, and ram chairs.

[0010] In the above embodiment, in the first chipping process, notches (37) may be formed that allow the upper part of the existing floor slab and the end of the existing floor slab to communicate with the outside.

[0011] According to this embodiment, when workers remove a portion of the end of an existing tensioning member, they do not need to chip away at the cantilevered floor slab again. Therefore, the work in the removal process becomes easier.

[0012] In the above embodiment, in the first chipping step, a recess (61) is formed above the existing floor slab that communicates with the outside, and in the removal step, a groove (62) is formed that is continuous with the recess and connects the end of the existing floor slab to the outside.

[0013] According to this embodiment, the replacement process can be carried out using the end surface of the existing floor slab that defines the recess, thus enabling the replacement process to be performed with a simple configuration.

[0014] In the above embodiment, the intermediate anchoring device includes an anchoring block (43) having a hole (42) for receiving a portion of the existing tensioning material, and a plurality of wedges (44) that are inserted into the hole together with the existing tensioning material, and the replacement step may include a step of press-fitting the wedges toward the hole.

[0015] When the reaction force of the tension from the existing tensioning member is transferred from the ram chair to the intermediate anchoring device, a portion of the reaction force that acted on the ram chair pulls each wedge of the intermediate anchoring device toward the holes in the intermediate anchoring device. As a result, a portion of the tension is released, resulting in so-called set loss. In this embodiment, since each wedge is pre-press-fitted toward the holes in the intermediate anchoring device, set loss can be suppressed.

[0016] In the above embodiment, in the step of press-fitting the wedge toward the hole, the wedge is pressed toward the hole by a jack, and the reaction force of the jack may be transmitted directly or indirectly to the ram chair.

[0017] Since the ram chair is firmly fixed to the floor slab by the reaction force of the existing tensioning material, it can fully receive the reaction force of the jack. In this configuration, the jack can press each wedge of the intermediate anchoring device more strongly toward the hole in the intermediate anchoring device, thereby more effectively suppressing set loss.

[0018] In the above embodiment, the temporary support step may include a step of performing leveling to make the surface of the floor slab in the portion where the ram chair is placed smooth.

[0019] In this embodiment, the reaction force of the tension from the existing tensioning member is effectively transmitted to the floor slab via the ram chair.

[0020] Furthermore, in order to solve the above problems, the present invention provides a floor slab widening method for widening a concrete floor slab, comprising: a method for removing the existing fasteners configured as described above; a connection step (Figure 11) in which, after the removal step, a new tensioning member (50) is connected to the remaining portion of the end of the existing tensioning member; a construction step (Figure 13) in which, after the connection step, concrete is poured on the widening side of the existing floor slab to construct the floor slab widening section (15); and a tensioning step (Figure 13) in which the tensioning force is introduced to the existing tensioning member and the new tensioning member after the construction step.

[0021] According to this aspect, it is possible to lift a portion near the end of the floor slab without considering the crushing of the concrete portion of the floor slab caused by the reaction force of the tension acting on the existing fixture. Therefore, it is possible to widen the concrete floor slab while reducing the impact on the traffic lane.

[0022] In the floor slab widening method of the above aspect, the construction process may include a process of covering the periphery of the intermediate fixture, the periphery of the exposed existing tension member, and the periphery of the newly installed tension member with a sheath (54).

[0023] According to this aspect, each member does not adhere to the placed concrete. Therefore, the operator can easily introduce the tension even after the placed concrete has hardened.

[0024] In the floor slab widening method of the above aspect, a plurality of existing tension members are arranged at intervals in the bridge axis direction, and in this floor slab widening method, for each existing tension member, after the temporary support process, the first suspension process, and the replacement process are performed, and before the connection process, a second suspension process (FIG. 10) of lifting a part of the existing floor slab so as to connect the plurality of parts suspended in the first suspension process may be further provided.

[0025] According to this aspect, it is possible to suppress the alternating arrangement of the existing floor slab and the floor slab widening part in the bridge axis direction. That is, the unevenness caused by the upper surface of the existing floor slab and the upper surface of the floor slab widening part is suppressed. Therefore, it is possible to suppress the discomfort felt by the passengers when the vehicle travels on this.

Effect of the Invention

[0026] The present invention can provide a method for removing an existing fixture in a concrete floor slab and a floor slab widening method capable of attaching an intermediate fixture to an existing tension member while suppressing interference with various members arranged inside the existing concrete floor slab and without crushing the concrete.

Brief Description of the Drawings

[0027] [Figure 1] Front view showing the bridge girder of a bridge to which the deck widening method according to the present invention has been applied. [Figure 2] A cross-sectional view showing the end of the cantilevered floor slab. [Figure 3] A plan view showing the state in which temporary support members are placed at the end of the cantilevered floor slab in the floor slab widening method according to the first embodiment. [Figure 4] Plan view showing the temporary support process for the deck widening method according to the first embodiment. [Figure 5] Plan view showing the first chipping process of the deck widening method according to the first embodiment. [Figure 6] Plan view showing the replacement process of the deck widening method according to the first embodiment. [Figure 7] Plan view showing the intermediate fixing device [Figure 8] Plan view showing the process of pressing each wedge into place during the replacement process. [Figure 9] Plan view showing the removal process of the deck widening method according to the first embodiment. [Figure 10] Plan view showing the second demolition process of the deck widening method according to the first embodiment. [Figure 11] Plan view showing the connection process of the deck widening method according to the first embodiment. [Figure 12] A plan view showing the construction process of the deck widening method according to the first embodiment, with the area around the intermediate anchoring device, the area around the exposed existing tensioning material, the area around the connector, and the area around the newly installed tensioning material near the connector covered with a sheath. [Figure 13] Plan view showing the construction process and tensioning process of the deck widening method according to the first embodiment. [Figure 14] A plan view (A) showing the first chipping process of the deck widening method according to the second embodiment, a plan view (B) showing the replacement process of the deck widening method according to the second embodiment, and a plan view (C) showing the process of forming a groove in the removal process of the deck widening method according to the second embodiment. [Modes for carrying out the invention]

[0028] (First Embodiment) The floor slab widening method (hereinafter simply referred to as the "widening method"), which includes a method for removing pre-installed fasteners according to the present invention, will be described below with reference to the drawings.

[0029] As shown in Figure 1, the bridge 1 comprises a bridge girder 2 supported by abutments or piers (not shown). In this embodiment, the bridge girder 2 is a concrete box girder. Specifically, the bridge girder 2 has a pair of left and right webs 3 extending in the direction of the bridge axis, a lower deck (not shown) provided between the lower ends of each web 3, and an upper deck 4 provided between the upper ends of each web 3. The bridge girder 2 also has a pair of cantilevered decks 6 extending outward in the bridge width direction from both ends of the upper deck 4, and a wall parapet 7 provided at the bridge width direction end of each cantilevered deck 6.

[0030] A tensioning force in the bridge width direction is introduced to the cantilevered deck 6. As shown in Figure 2, the cantilevered deck 6 further comprises a plurality of tensioning members 8 (only one is shown in the figure) that extend in the bridge width direction and are spaced apart from each other in the bridge axis direction, and a pair of anchoring devices 9 (only one is shown in the figure) provided at both ends of each tensioning member 8.

[0031] Each anchoring device 9 may have a known configuration, for example, comprising a plate 11 provided at the outer end of the cantilevered slab 6 in the bridge width direction (hereinafter simply referred to as "the end of the cantilevered slab 6"), a grip 12 for receiving the end of the tensioning member 8, and a plurality of wedges 13 inserted into the grip 12 together with the end of the tensioning member 8. The plate 11 is embedded in the cantilevered slab 6 in advance. The outer surface of the plate 11 in the bridge width direction is positioned on the same plane as the outer end surface of the cantilevered slab 6 in the bridge width direction (hereinafter simply referred to as "the end surface of the cantilevered slab 6"). Both ends of each tensioning member 8 pass through through holes (not shown) provided in the corresponding plate 11. The grip 12 is formed in a cylindrical shape. The inner surface of the grip 12 in the bridge width direction is in contact with the outer surface of the plate 11 in the bridge width direction.

[0032] Each tension member 8 is subjected to a tensioning force directed outward in the bridge width direction. With tension applied to each tension member 8, anchoring devices 9 are attached to both ends of each tension member 8, thereby transferring the tension of each tension member 8 to the cantilevered deck slab 6 via the corresponding anchoring devices 9. More specifically, the reaction force of the tension of each tension member 8 is transmitted to the cantilevered deck slab 6 via the corresponding anchoring devices 9.

[0033] In the widening method according to this embodiment, the cantilevered floor slab 6 is widened by providing a floor slab widening section 15 (see Figure 1) at one end of the cantilevered floor slab 6.

[0034] First, the worker removes the wall railing 7. Next, the worker temporarily supports the temporary support member 18 from the existing anchoring fixture 9 to the reaction force of the tension of each existing tension member 8 (temporary support step). As shown in Figure 3, in this embodiment, the temporary support member 18 has a tension bar 19 including screw threads (not shown), a connector 20 that connects the tension bar 19 and the existing anchoring fixture 9, a ram chair 21 for supporting the tension bar 19, and a nut 22 that screws onto the tension bar 19.

[0035] The tension bar 19 is formed in a cylindrical shape. The tension bar 19 is positioned on the same axis as the existing tension member 8.

[0036] The connector 20 may have a known configuration, for example, comprising a first sleeve 24 that receives the grip 12 of an existing fixture 9, and a plurality of wedges (not shown) that are inserted into the first sleeve 24 together with the grip 12 of the existing fixture 9. The first sleeve 24 is formed in a cylindrical shape. The connector 20 also has a cylindrical second sleeve 26 that can be connected to the first sleeve 24. The first sleeve 24 and the second sleeve 26 may be connected, for example, by screwing together a threaded portion (not shown) formed on the inner circumferential surface of the first sleeve 24 and a threaded section (not shown) formed on the outer circumferential surface of the second sleeve 26.

[0037] The second sleeve 26 is attached to the inner end of the tension bar 19 in the bridge width direction. The tension bar 19 and the second sleeve 26 may be connected by screwing the threads of the tension bar 19 into a threaded portion (not shown) formed on the inner circumferential surface of the second sleeve 26.

[0038] The Ram Chair 21 may have a known configuration, for example, a disc-shaped seat 31 positioned at a distance from the end face of the cantilevered floor slab 6, and a plurality of legs 32 extending from the seat 31 toward the end face of the cantilevered floor slab 6. The tip of each leg 32 extends in a direction parallel to the end face of the cantilevered floor slab 6. The seat 31 has a through hole 33 that penetrates in the bridge width direction. The through hole 33 has a circular cross-section and is sized to allow the tension bar 19 to pass through.

[0039] The inner diameter of the nut 22 is approximately equal to the inner diameter of the through hole 33 of the seat portion 31. In this embodiment, the outer diameter of the nut 22 is larger than the inner diameter of the through hole 33. That is, the nut 22 can abut against the portion of the seat portion 31 surrounding the through hole 33. In other embodiments, the nut 22 may abut against the seat portion 31 via a plate (not shown).

[0040] As shown in Figure 4, in the temporary support process, the worker attaches one temporary support member 18 to one existing tension member 8. Specifically, first, the worker performs leveling to smooth the surface around the existing anchoring device 9 on the end face of the cantilevered floor slab 6. In this embodiment, non-shrink mortar is used as the leveling material 35 for leveling. Then, the worker inserts the existing anchoring device 9 into the first sleeve 24 of the connector 20 together with the wedge of the connector 20. This attaches the first sleeve 24 to the existing anchoring device 9. The worker screws the threaded portion of the second sleeve 26 onto the threads of the tension bar 19 and attaches the tension bar 19 to the second sleeve 26. Then, the worker connects the first sleeve 24 and the second sleeve 26. In this way, the existing anchoring device 9 is connected to the tension bar 19 via the connector 20. After that, the worker places the ram chair 21 on the end face of the cantilevered floor slab 6. Specifically, the worker inserts the tension bar 19 through the through hole 33 in the seat 31 of the ram chair 21 and brings the tip of the leg 32 of the ram chair 21 into contact with the unevenness adjustment material 35. Then, the worker uses a jack (not shown) to tension the tension bar 19 outward in the bridge width direction. This tensions the existing tension member 8 outward in the bridge width direction via the connector 20 and the existing anchoring device 9. After that, the worker screws the nut 22 onto the threads at the outer end of the tension bar 19 in the bridge width direction and brings the nut 22 into contact with the seat 31 of the ram chair 21. As a result, the reaction force of the tension of the existing tension member 8 is transmitted to the cantilevered slab 6 via the existing anchoring device 9, connector 20, tension bar 19, nut 22, and ram chair 21. Therefore, the reaction force of the tension of the existing tension member 8 can be temporarily supported by the ram chair 21 from the existing anchoring device 9. By performing leveling adjustments, the reaction force of the tension from the existing tension members 8 is effectively transmitted to the cantilevered floor slab 6 via the ram chair 21. The worker prepares multiple temporary support members 18 and performs a temporary support process on the multiple existing tension members 8.

[0041] As shown in Figure 5, the worker then chips away a portion of the cantilevered slab 6 (the portion enclosed by the dashed line in Figure 2) to expose a portion of the existing tension members 8 (first chipping step). In the first chipping step, the worker forms a notch 37 through which the upper part and the end of the cantilevered slab 6 communicate with the outside. The notch 37 is formed in a U-shape with the top open when viewed in the bridge width direction. In other embodiments, the notch 37 may be formed so that the upper part, lower part, and end of the cantilevered slab 6 communicate with the outside. The worker may remove the sheath covering the exposed existing tension members 8 as needed. The worker then performs the first chipping step on each of the existing tension members 8 that have undergone the temporary support step.

[0042] As shown in Figure 6, the worker then attaches the intermediate anchoring device 41 to the exposed portion of the existing tensioning member 8, thereby transferring the reaction force of the tension from the ram chair 21 to the intermediate anchoring device 41 (transfer process).

[0043] As shown in Figure 7, in this embodiment, the intermediate anchoring device 41 includes an anchoring block 43 with a hole 42 for receiving the existing tensioning material 8, and a plurality of wedges 44 that are inserted into the hole 42 together with the existing tensioning material 8.

[0044] The anchoring block 43 has two halves 45 (only one is shown in the figure) and a number of bolts 46 that connect the two halves 45 to each other.

[0045] Each split block 45 is roughly rectangular in shape. Each split block 45 has multiple bolt holes (not shown) extending in the vertical direction. Each bolt hole is provided so that it can be screwed into a corresponding bolt 46. When two split blocks 45 are stacked vertically, each bolt hole in one split block 45 aligns with the corresponding bolt hole in the other split block 45. With the two split blocks 45 stacked vertically, the two split blocks 45 are joined together by screwing the bolts 46 corresponding to each bolt hole into them.

[0046] Furthermore, each half-block 45 has a groove (not shown) that is recessed inward from one of its upper or lower surfaces. Each groove is formed along the bridge width direction. Each groove is semicircular in cross-section. The radius of each groove is configured to decrease from the outside to the inside in the bridge width direction. When two half-blocks 45 are stacked vertically, the groove provided in one half-block 45 faces the groove provided in the other half-block 45. This forms a hole 42.

[0047] As shown in Figure 6, in the replacement process, first, the worker places the bearing plate 48 on the portion of the exposed existing tension member 8 that is embedded in the cantilevered deck slab 6. Then, the worker places one of the split blocks 45 below the existing tension member 8. At this time, the inner surface of one of the split blocks 45 in the bridge width direction should be in contact with the bearing plate 48. The worker also receives a portion of the existing tension member 8 into a groove provided in one of the split blocks 45. Then, the worker places the other split block 45 on top of the first split block 45. After that, the worker connects the two split blocks 45 to each other by screwing in bolts 46 corresponding to each bolt hole. After that, the worker inserts each wedge 44 into the hole 42 of the anchoring block 43 from the outside in the bridge width direction (see Figure 8). In this way, the intermediate anchoring device 41 is attached to the existing tension member 8.

[0048] As shown in Figure 8, after the intermediate anchoring device 41 is attached to the existing tensioning member 8, the worker presses each wedge 44 of the intermediate anchoring device 41 into the holes 42 of the intermediate anchoring device 41. Specifically, the worker places multiple jacks 49 between the intermediate anchoring device 41 and the plate 11 of the existing anchoring device 9. Then, the worker uses each jack 49 to press each wedge 44 into the holes 42 of the intermediate anchoring device 41. At this time, the reaction force of the jacks 49 is transmitted to the ram chair 21 of the temporary support member 18 via the plate 11 of the existing anchoring device 9. The worker may, if necessary, place spacers or bearing plates between each jack 49 and the plate 11 of the existing anchoring device 9 to receive the reaction force of each jack 49.

[0049] As shown in Figure 9, the worker then removes each jack 49 and ram chair 21, and removes the existing anchoring devices 9 and a portion of the exposed ends of the existing tensioning members 8 (removal process). Specifically, the worker releases the tension force introduced into the tension bar 19 of the temporary support member 18, and then removes the temporary support member 18. This completes the method for removing the existing tensioning members and anchoring devices 9 in the concrete cantilevered slab 6. After that, the worker cuts and removes a portion of the exposed ends of the existing tensioning members 8 using a cutting tool. As a result, the reaction force of the tension of the existing tensioning members 8 is transferred from the ram chair 21 to the intermediate anchoring devices 41. The worker prepares multiple intermediate anchoring devices 41 and performs the transfer process and removal process on each of the existing tensioning members 8 that have undergone the first chipping process.

[0050] Because the notch 37 exposes the end of the existing tensioning member 8, the worker does not need to chip away at the cantilevered floor slab 6 again when removing a portion of the end of the existing tensioning member 8. Therefore, the work in the removal process is made easier.

[0051] When the reaction force of the tension from the existing tensioning member 8 is transferred from the ram chair 21 to the intermediate anchoring device 41, a portion of the reaction force of the tension acting on the ram chair 21 pulls each wedge 44 of the intermediate anchoring device 41 toward the holes 42 of the intermediate anchoring device 41. As a result, a portion of the tension is released, resulting in so-called set loss. Set loss can be suppressed by pre-pressing each wedge 44 of the intermediate anchoring device 41 toward the holes 42 of the intermediate anchoring device 41 during the transfer process. Since the ram chair 21 is firmly fixed to the end of the cantilevered floor slab 6 by the reaction force of the existing tensioning member 8, it can fully receive the reaction force of the jack 49. Therefore, the jack 49 can press each wedge 44 of the intermediate anchoring device 41 toward the holes 42 of the intermediate anchoring device 41 more strongly, thereby more effectively suppressing set loss.

[0052] As shown in Figure 10, the worker then chips away a portion of the cantilevered deck slab 6 so that the multiple notches 37 formed in the first chipping process are continuous in the direction of the bridge axis (second chipping process).

[0053] As shown in Figure 11, the worker then connects the new tension members 50 to the remaining ends of each existing tension member 8 (connection step). In the connection step, the worker connects the existing tension members 8 and the new tension members 50 to each other via a connector 51. In this embodiment, the area around the new tension members 50 other than the ends is covered with a sheath 52.

[0054] The connector 51 may have a known configuration, for example, comprising a cylindrical coupler (not shown), a first sleeve (not shown) attached inside one end of the coupler, and a second sleeve (not shown) positioned inside the other end of the coupler. The connector 51 also has a plurality of first wedges (not shown) inserted into the first sleeve and a plurality of second wedges (not shown) inserted into the second sleeve. The existing tension member 8 is inserted into the first sleeve along with the plurality of first wedges. The first sleeve and the coupler are connected by screwing together threads (not shown) formed on the outer circumference of the first sleeve and threads (not shown) formed on the inner circumference of the other end of the coupler. The new tension member 50 is inserted into the second sleeve along with the plurality of second wedges. After the second sleeve is positioned inside the other end of the coupler, a cover member is attached inside the other end of the coupler. In this way, the existing tension member 8 and the new tension member 50 are connected to each other via the connector 51.

[0055] Next, the worker constructs the widened section 15 of the deck on the side of the end of the cantilevered deck 6 (construction process). Specifically, as shown in Figure 12, the worker first covers the area around the intermediate anchoring device 41, the area around the exposed existing tensioning material 8, the area around the connector 51, and the area around the newly installed tensioning material 50 near the connector 51 with a sheath 54. In this embodiment, the sheath 54 has an inlet (not shown) and an outlet (not shown) for filling the inside of the sheath 54 with filler material.

[0056] Subsequently, the workers assemble formwork (not shown) on the end side of the cantilevered slab 6. The formwork contains each intermediate anchoring device 41, each exposed existing tensioning member 8, each connecting device 51, and each newly installed tensioning member 50. In addition, plates 57 for the new anchoring devices 56 are placed on the formwork so that new anchoring devices 56 can be installed on each of the newly installed tensioning members 8. After that, the workers pour concrete into the formwork. As shown in Figure 13, the widened section 15 of the slab is constructed as the poured concrete hardens.

[0057] Next, the worker applies tension to each of the existing tension members 8 and each of the newly installed tension members 50 (tensioning process). The worker uses a known jack (not shown) or the like to tension the ends of each of the newly installed tension members 50 outwards in the bridge width direction. As a result, the tension applied to each of the newly installed tension members 50 is also applied to the existing tension members 8 via the corresponding connectors 51. With tension applied to each of the existing tension members 8 and each of the newly installed tension members 50, the worker attaches the new anchoring devices 56 corresponding to the ends of each of the newly installed tension members 50. The new anchoring devices 56 may have the same configuration as the existing anchoring devices 9. As a result, the reaction force of the tension applied to each of the newly installed tension members 50 is transmitted to the widened section 15 of the deck via the corresponding new anchoring devices 56.

[0058] Since the area around the intermediate anchoring device 41, the area around the exposed existing tensioning member 8, the area around the connector 51, and the area around the newly installed tensioning member 50 near the connector 51 are covered with the sheath 54, each member does not adhere to the poured concrete. Therefore, even after the poured concrete has hardened, tension can be easily introduced into each of the existing tensioning members 8 and each of the newly installed tensioning members 50.

[0059] In the second chipping process, a portion of the cantilevered deck slab 6 is chipped away, which prevents the cantilevered deck slab 6 (existing deck slab section) and the deck widening section 15 (new deck slab section) from being alternately arranged in the bridge axis direction. In other words, irregularities caused by the upper surfaces of the cantilevered deck slab 6 and the deck widening section 15 are suppressed. Therefore, discomfort felt by occupants when a vehicle travels over it can be reduced.

[0060] Afterward, the worker fills the inside of the sheath 54 with a filler material (not shown). The filler material may be, for example, non-shrink mortar or epoxy resin. The cantilevered floor slab 6 is then widened. The worker may then install a new railing 59 (see Figure 1) above the end of the widened floor slab section 15.

[0061] In the widening method described above, before chipping away a portion of the cantilevered slab 6 in the first chipping process, and before the reaction force of the tension from the existing tensioning member 8 is borne by the intermediate anchoring device 41, it can be temporarily supported by the ram chair 21 positioned at the end of the cantilevered slab 6. Therefore, the portion of the cantilevered slab 6 close to the end can be chipped away without considering the crushing of the concrete portion of the cantilevered slab 6 caused by the reaction force of the tension acting on the existing anchoring device 9. Consequently, the impact on the traffic lane can be reduced.

[0062] (Second Embodiment) Next, a second embodiment of the widening method will be described with reference to Figure 14. Elements identical or similar to those in the first embodiment of the widening method will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0063] As shown in Figure 14(A), in the first chipping process, a recess 61 is formed above the cantilevered slab 6, which communicates with the outside. The recess 61 is formed in a rectangular shape in plan view. As shown in Figure 14(B), in the subsequent replacement process, the worker places an intermediate anchoring device 41 in the recess 61 and transfers the reaction force of the tension force acting on the ram chair 21 to the intermediate anchoring device 41. As shown in Figure 14(C), in the subsequent removal process, the worker forms a groove 62 that is continuous with the recess 61 and connects the end of the cantilevered slab 6 to the outside. The dashed line in Figure 14(C) is a virtual line indicating the end side of the cantilevered slab 6 that defines the recess 61.

[0064] In the widening method according to the second embodiment, it is necessary to form a groove 62 in the removal process, but when pressing each wedge 44 of the intermediate anchoring device 41 with a jack 49, the reaction force can be transmitted to the end surface of the cantilevered floor slab 6 that defines the recess 61. In other words, since there is no need to prepare spacers or bearing plates to receive the reaction force of each jack 49, the replacement process can be carried out with a simple configuration.

[0065] This concludes the description of the specific embodiments, but the present invention is not limited to the above embodiments and can be broadly modified and implemented. In this embodiment, a floor slab widening section 15 is provided on one of the pair of cantilevered floor slabs 6, but floor slab widening sections 15 may be provided corresponding to each cantilevered floor slab 6. The specific configuration, arrangement, quantity, material, or procedure of each member or part can be changed as appropriate, as long as it does not depart from the spirit of the present invention. Furthermore, not all of the components shown in the above embodiment are necessarily essential and can be selected as appropriate. [Explanation of symbols]

[0066] 6: Extruded floor slab (floor slab) 8: Tensioning material (existing tensioning material) 9: Fixing device (existing fixing device) 15: Widening section of the deck 19: Tension bar 20: Connectors 21: Lamb Chair 22: Nut 37: Notch 41: Intermediate fixing device 44: Wedge 50: Tensioning material (newly installed tensioning material) 54: Sheath 61: Recess 62: Groove

Claims

1. A method for removing pre-installed fasteners in a concrete slab in which tensioning force has been introduced by tensioning material and anchoring device, A temporary support step involves placing a ram chair at the end of the floor slab and temporarily supporting the reaction force of the tension from the existing tensioning member to the ram chair from the existing anchoring device, A first chipping step involves chipping away a portion of the aforementioned floor slab to expose a portion of the existing tensioning member, After the first lifting process, an intermediate anchoring device is attached to the exposed portion of the existing tensioning material, and the reaction force of the tensioning force of the existing tensioning material is transferred from the ram chair to the intermediate anchoring device in a transfer process, A method for removing an existing fastener, comprising: a replacement step, a removal step, after which the ram chair is removed and a portion of the existing fastener and the exposed end of the existing tensioning material are removed.

2. In the aforementioned temporary receiving process, A method for removing an existing fastener according to claim 1, wherein the reaction force of the tension of the existing tensioning member is temporarily received by the existing fastener and the ram chair by using a connector to be attached to the existing fastener, a tension bar attached to the connector, and a nut attached to the tension bar and in contact with the ram chair.

3. In the first chipping process described above, The method for removing pre-installed fasteners according to claim 2, wherein a notch is formed in which the upper part of the existing floor slab and the end of the existing floor slab communicate with the outside.

4. In the first chipping process described above, A recess is formed above the existing floor slab that communicates with the outside. In the removal process, The method for removing a pre-installed fastener according to claim 2, wherein a groove is formed that is continuous with the recess and connects the end of the existing floor slab to the outside.

5. The aforementioned intermediate fixing device is A fixing block having a hole formed to receive a portion of the existing tensioning member, It has a plurality of wedges that are inserted into the hole together with the existing tensioning member, The method for removing a previously attached device according to claim 1, wherein the replacement step includes the step of pressing the wedge toward the hole.

6. In the step of pressing the wedge toward the hole, the wedge is pressed toward the hole by a jack, The method for removing a pre-installed fastener according to claim 5, wherein the reaction force of the jack is transmitted directly or indirectly to the ram chair.

7. The method for removing pre-installed fixtures according to claim 1, wherein the temporary support step includes a step of performing leveling to make the surface of the portion of the floor slab on which the ram chair is placed smooth.

8. A method for removing a pre-attached device according to any one of claims 1 to 7, After the removal step, a connection step is performed in which a new tensioning member is connected to the remaining portion of the end of the existing tensioning member. After the connection step, a construction step is performed to construct the widened section of the existing deck by pouring concrete on the widening side of the deck, A slab widening method comprising, after the construction step, a tensioning step of introducing the tensioning force to the existing tensioning members and the newly installed tensioning members.

9. The floor slab widening method according to claim 8, wherein the construction step includes covering the area around the intermediate anchoring device, the area around the exposed existing tensioning material, and the area around the newly installed tensioning material with a sheath.

10. The existing tensioning members are arranged in multiple locations with gaps between them in the direction of the bridge axis. This deck widening method is, The floor slab widening method according to claim 8, further comprising a second chipping step in which, after the temporary support step, the first chipping step, and the support replacement step are performed for each existing tensioning member, and before the connection step, a portion of the existing floor slab is chipped away in the first chipping step to make a continuous line.

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