Method for removing floor slab

Abstract

To provide a method for shortening the time required to remove a floor slab in a composite beam, and efficiently removing the floor slab.SOLUTION: A method for removing a floor slab includes: a process for forming a gap with the prescribed depth on a floor slab made of reinforced concrete joined to a box girder, with slip preventive members arranged in a row toward the axial direction of the box girder, on both end parts of the box girder in a composite beam in the width direction; a process for inserting an expansion member that expands when pressure is applied to its inside, into the formed gap; and a process for applying pressure to the inside of expansion members inserted into each of a plurality of gaps formed through the repetition of forming processes and inserting processes, in a specified order, expanding the expansion members, breaking the floor slab into block pieces, ripping them from the box girder and removing them. The gaps are formed at least on and between the slip preventive members arranged in a row on both end parts of the box girder in the width direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for removing a deck in a composite girder. [Background technology]

[0002] The decks of bridges such as road bridges need to be removed and replaced with new ones due to deterioration and damage over time. The main girders and deck structures that make up bridges can be either composite or non-composite girders. In composite girders, dowel bars are installed on the girder flanges of the main girders to firmly connect the main girders to the deck constructed on top of them. For this reason, removing the deck of a composite girder is a time-consuming and labor-intensive task.

[0003] Known methods for removing deck slabs in composite girders include cutting the deck slab between the girders with a road cutter, lifting it with a crane, and then manually chipping away the concrete remaining on the girder flanges with a hand breaker or removing it using the water jet (WJ) method (see, for example, Patent Document 1 and Non-Patent Document 1).

[0004] There is also a known method of attaching a wire saw to the side of the main girder, penetrating the wire into the deck, and horizontally cutting the deck above the girder flange (see, for example, Patent Document 2 and Non-Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7008477 [Patent Document 2] JP 2023-34231 A [Non-patent literature]

[0006] [Non-Patent Document 1] Toshinori Amano and 4 others, "Replacement of Deck of Composite Plate Girder Bridge, Ochiaigawa Bridge (Downbound) on Chuo Expressway", Japan Society of Civil Engineers, 75th Annual Conference of Japan Society of Civil Engineers, VI-731, September 2020 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above Patent Documents 1 and 2 and Non-Patent Document 1 do not mention the removal of the deck on the box girder when the main girder of the composite girder is a box girder, so the deck on the box girder will be removed by hand cutting, as in the past. This poses the problem that the deck removal work for the composite girder takes time, and the deck cannot be removed efficiently. [Means for solving the problem]

[0008] The present invention has been made in consideration of the above problems, and is a method for removing a deck slab in a composite girder, A step of forming a gap of a predetermined depth extending in the axial direction of the box girder in a deck slab made of reinforced concrete joined to a box girder having anti-slip members arranged in a row in the axial direction of the box girder at both ends of the box girder in the width direction of the composite girder; A step of inserting an expansion member that expands by applying pressure to the inside of the expansion member into the formed gap; A process of pressurizing and expanding the inside of the expansion members inserted into each of the multiple gaps formed by repeating the forming process and the inserting process in a specified order, splitting the deck into block pieces, and peeling them off from the box girder and removing them; Including, A method for removing a deck is provided in which a plurality of gaps are formed at least on the anti-slip members arranged in a row at both ends in the width direction of the box girder and between the anti-slip members arranged in a row at both ends. Effect of the Invention

[0009] According to the present invention, it is possible to reduce the time required for deck removal work in a composite girder and to remove the deck efficiently. [Brief description of the drawings]

[0010] [Figure 1] A diagram showing an example of a road bridge structure. [Diagram 2] This is a diagram showing a simulated composite box girder that imitates an example of a joint between a main girder and a deck in a road bridge. [Diagram 3] FIG. 4 is a diagram showing an example of an expansion member. [Figure 4] 11 is a flowchart showing an example of a work for removing a deck slab. [Diagram 5] A diagram showing how a slit is formed in the deck and a plate jack is inserted. [Figure 6] FIG. 13 is a diagram showing the state in which initial pressure is applied to a plate jack inserted into a slit formed at approximately the center position. [Figure 7] This diagram shows how water pressure is applied to a plate jack inserted into a slit formed in a dowel reinforcement to remove the cut outer block piece. [Figure 8] This diagram shows how water pressure is applied to a plate jack inserted into a slit formed on the side of a dowel bar to remove the cut outer block piece. [Figure 9] This figure shows how water pressure is applied again to the plate jack inserted into the slit formed at approximately the center to cut it. [Figure 10] A diagram showing the block pieces being lifted by a hoist and removed from the steel plate. [Figure 11] A diagram showing the state of the steel plate after the deck was removed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Figure 1 shows an example of a road bridge structure with two main girders (box girders) and a deck slab. A road bridge is one type of bridge, and other bridges include railway bridges and pedestrian bridges. A bridge is a road structure that is erected over a river or other waterway, leaving space under the girders, and is 2m or longer in length.

[0012] A road bridge 10 is composed of a substructure (subwork) such as piers, and a superstructure (superwork) that is constructed on the subwork and directly supports pedestrians, vehicles, etc. The superstructure includes supports 11 that transmit loads to the subwork, main girders 12 that support the entire superwork and extend vertically from the supports 11 that transmit loads to the subwork via the supports 11, cross girders 13 that connect the main girders 12, and a deck slab 14 that transmits the weight of pedestrians, vehicles, etc. as load to the main girders 12 and cross girders 13.

[0013] The bearing 11 may be a movable bearing that absorbs the rotation and expansion and contraction of the superstructure, or a fixed bearing that absorbs only the rotation of the superstructure, or a seismic isolation bearing that uses laminated rubber or the like for elastic fixation.

[0014] The main girder 12 may be an I-girder, a box girder, etc., depending on the shape of a vertical cross section, and may be a steel girder, a reinforced concrete girder, a PC (prestressed concrete) girder, etc., depending on the material. In the present invention, the main girder 12 is a box girder that is a box-shaped girder with a hollow interior.

[0015] The cross girder 13 is a girder that is installed to extend in the width direction of the bridge in order to distribute the load of the main girder 12. Normally, the load is shared between the main girder 12 and the cross girder 13, but if necessary, a vertical girder may be installed along the axial direction of the bridge, and the load may be shared between the main girder 12, the cross girder 13, and the vertical girder.

[0016] Like the main girders 12 and cross girders 13, the deck 14 may be constructed from materials such as steel, reinforced concrete, and precast concrete. In the present invention, the deck 14 is constructed from reinforced concrete. A deck waterproof layer 15 such as a waterproof sheet is provided on the deck 14 to prevent deterioration due to water intrusion into the deck 14, and asphalt or the like is laid on the deck waterproof layer 15 to perform paving 16.

[0017] On both ends of the bridge in the width direction, a ground cover 17, which is a step higher than the pavement 16, is provided. A protective fence 18 is provided on the ground cover 17 to prevent people, vehicles, etc. from falling off the bridge.

[0018] The deck 14 may be constructed by installing formwork, laying rebar, and pouring concrete after installing the two main girders 12 and cross girders 13, or by using precast reinforced concrete deck members. At this time, to strengthen the connection between the two main girders 12 and cross girders 13 and the deck 14, a row of dowel bars 19 bent into a horseshoe shape (U-shape) or headed rod-shaped stud dowel bars is installed as a slip prevention member at both ends of the girder flange of each main girder 12 (both ends in the width direction of the bridge).

[0019] A plurality of dowel bars 19 are provided in a row at predetermined intervals in the longitudinal direction (axial direction) of the bridge at each end of the girder flange of each main girder 12. Therefore, in Fig. 1, there are two main girders 12, and dowel bars 19 are provided in a row at both ends of each main girder 12, resulting in a total of four rows of dowel bars 19.

[0020] When using precast reinforced concrete deck members, holes are provided at positions corresponding to the dowel bars 19, and after the dowel bars 19 are inserted into the holes, the holes can be filled with mortar or the like to integrate the main girders 12 and deck slab 14. A girder having a structure in which the main girders 12 and deck slab 14 are integrated with the dowel bars 19 is called a composite girder. A composite girder is a girder made by overlapping different materials, and when the deck slab 14 is made of reinforced concrete, the main girders are made of materials other than reinforced concrete or concrete, such as steel.

[0021] When replacing the deck 14 in a composite girder, the pavement 16 and the deck waterproof layer 15 are removed by peeling or the like, and then the deck 14 can be removed by hand cutting or the WJ method or the like, as in conventional techniques.

[0022] However, when a steel box girder is used as the main girder 12, dowel bars 19 are installed in a row on both ends of the girder flange of the box girder in the width direction of the bridge, and not only the area around the dowel bars 19 but also the deck 14 remaining between the dowel bars 19 installed in a row on both ends must be removed by hand cutting, WJ method, etc. This makes it time-consuming to remove the deck 14, and makes it difficult to remove the deck 14 efficiently.

[0023] In view of this, the present invention provides a deck slab removal method that enables the deck slab 14 to be removed efficiently.

[0024] This method may be explained with reference to the road bridge 10 shown in Figure 1, but to make this method easier to understand, it will be explained using a simulated composite box girder as shown in Figure 2. In addition, in the actual road bridge 10, two box girders are installed as shown in Figure 1, but since the deck slabs on both box girders can be removed using the same method, only the removal of the deck slab on one box girder will be explained below.

[0025] The simulated composite box girder includes a plurality of H-shaped steels 20, each of which has an H-shaped cross section cut in the vertical direction, corresponding to one main girder 12 shown in Fig. 1, and an iron plate 21 arranged to connect the upper flanges of the two H-shaped steels 20 installed at both ends of the box girder in the width direction. The iron plate 21 is arranged between the upper flanges of the two H-shaped steels 20a, and a plate 22 is arranged so as to straddle the upper flanges of each H-shaped steel 20a and the lower surface of the iron plate 21, and the plates 22 are connected by welding or the like. The iron plate 21 is supported by the two H-shaped steels 20a and two H-shaped steels 20b whose flanges are lower in height than the two H-shaped steels 20a arranged between them.

[0026] The H-shaped steel 20 is one of the long steel materials formed into a fixed cross-sectional shape, and the two parts of the H-shaped cross section that extend almost parallel are the flanges (upper flange, lower flange), and the part connecting the upper flange and the lower flange is the web. The steel plates 21 are plates with a specified thickness and width, and multiple sheets are laid out and installed in the axial direction of the box girder.

[0027] The simulated composite box girder includes horseshoe-shaped dowel bars 23 welded in a row at regular intervals in the axial direction of the box girder on the upper flanges of two H-shaped steels 20a, which are both ends of the box girder in the width direction, and a deck 25 made of reinforced concrete joined to the upper flanges of the two H-shaped steels 20a and the steel plate 21. The width direction of the box girder corresponds to the width direction of the bridge shown in FIG. 1 (direction perpendicular to the bridge axis), and the axial direction of the box girder corresponds to the axial direction of the bridge shown in FIG. 1. In the example shown in FIG. 2, the thickness of the deck 25 is formed so as to become thicker from one end of the box girder to the other end in the width direction, but it may be a constant thickness, etc.

[0028] The dowel bars 23 are provided as anti-slip members to maintain the unity of the H-shaped steel 20 and steel plate 21, which correspond to the box girder, with the deck slab 25. As the dowel bars 23, in addition to horseshoe-shaped dowel bars, headed studs having a rod-shaped expanded head, perforated steel dowels having multiple holes in a flat plate, etc. may be used.

[0029] The reinforcing bars 24 extend in two rows, upper and lower, as main reinforcements in the axial direction of the box girder, and are arranged at predetermined intervals in the width direction of the box girder. In the example shown in Fig. 2, the interval between the main reinforcements in the upper row is narrow, and the interval between the main reinforcements in the lower row is wide.

[0030] The reinforcing bars 24 are arranged at a predetermined interval in the axial direction of the box girder as shear reinforcement surrounding the outside of the main reinforcement. In the cross section shown in Fig. 2, the reinforcing bars 24 are shown extending in two stages, up and down, in the width direction of the box girder. The reinforcing bars 24 are arranged in a manner that vertically connects the reinforcing bars extending in two stages in the width direction of the box girder.

[0031] Here, a gap (slit) was formed in the deck 25, a plate jack was inserted into the slit as an expansion member, and pressure was applied to the inside of the plate jack.It was found that if dowel lines 23 are present in the cutting depth direction of the slit, a crack will occur along the dowel lines 23, and if dowel lines 23 are not present, a crack will occur along the depth direction of the slit, and an upward rotating force will act on each of the deck (block pieces) that have been split in two by the crack, causing them to peel off from the steel plate 21.

[0032] The present invention was made based on this finding. Therefore, in this method, first, a slit 26 of a predetermined depth and length is formed in the axial direction of the box girder in a deck 25 made of reinforced concrete joined to a steel plate 21 having dowel bars 23 arranged in a row at both ends of the width direction of the box girder of the composite girder.

[0033] If only one slit 26 is formed in the deck 25 between the dowel bars 23 arranged in a row at both ends, even if a plate jack is inserted, expanded, and split into two pieces, each deck 25 cannot be peeled off from the steel plate 21 because it is restrained by the dowel bars 23. Therefore, it is necessary to cut the dowel bars 23.

[0034] Therefore, in order to cut off the dowel lines 23 not only between the dowel lines 23 arranged in a row at both ends, slits are formed toward each of the dowel lines 23 arranged in a row at both ends of the steel plate 21.

[0035] The slits 26 include at least three, for example, first and second slits 26a, 26b formed toward approximately the center of each of the dowel bars 23 lined up at both ends of the iron plate 21, and a third slit 26c formed toward the lower iron plate 21 at approximately the center between the dowel bars 23 lined up at both ends of the iron plate 21.

[0036] After the three slits 26a to 26c are formed in the deck 25, a plate jack is inserted into each of the slits 26a to 26c. Then, pressure is applied to the inside of the plate jack to expand the plate jack.

[0037] As a result, the deck 25 is split into four block pieces, and each block piece is peeled off from the upper flange of the H-shaped steel 20a and the steel plate 21, and is also severed from the dowel bars 23. Therefore, each block piece can be lifted and removed outside the site.

[0038] The slit 26 is formed using a cutting device such as a road cutter or wall saw, with a length and width that allows a plate jack to be inserted as an expansion member, a depth that does not reach the lower steel plate 21, and a depth that cuts the lower reinforcing bars of the reinforcing bars 24 arranged in two tiers. If the lower reinforcing bars remain uncut, even if they are split by the expansion of the plate jack, the block pieces will remain connected by the lower reinforcing bars, and the block pieces cannot be removed even if they are split and separated.

[0039] The plate jacks inserted into the first to third slits 26a to 26c are present on the upper surface side of the deck 25, and due to expansion, the width of the upper surface side of the first to third slits 26a to 26c increases, and cracks occur in the cutting depth direction of the first to third slits 26a to 26c. When the cracks in the first and second slits 26a and 26b reach the dowel reinforcement 23, they extend along the outer edge of the dowel reinforcement 23 to the upper flange of the lower H-shaped steel 20a, and in the third slit 26c, the cracks extend in the cutting depth direction until they reach the steel plate 21. As a result, the block is split into two pieces sandwiched between each slit.

[0040] At this time, an upward rotating force acts on the two split block pieces, causing the two block pieces to peel off from the center side of the slit. In order to completely peel off the block pieces, it is necessary to further widen the slit with a plate jack and press the block pieces horizontally to move them horizontally. For this reason, one side of the block pieces needs to be a free surface that is not restricted in its horizontal movement.

[0041] The block pieces at both ends of the width direction of the box girder, which are split by expanding the plate jacks inserted into the first and second slits 26a, 26b, respectively, have free surfaces and can be completely peeled off from the upper flanges of the H-shaped steel 20a. Therefore, the block pieces at both ends of the width direction of the box girder can be lifted as they are by a hoist such as a crane, carried out outside the site, and removed from the steel plate 21 without any special cutting work.

[0042] The two block pieces between the dowel bars 23 arranged in a row at both ends are split by expanding the plate jack inserted into the third slit 26c, and the center side of the two block pieces can be peeled off from the steel plate 21 around the third slit 26c. However, the two block pieces between the dowel bars 23 arranged in a row at both ends are restricted in their horizontal movement by the dowel bars 23, so there is a possibility that they cannot be completely peeled off from the steel plate 21.

[0043] Therefore, a fourth slit 26d and a fifth slit 26e are formed between the first slit 26a and the third slit 26c and between the second slit 26b and the third slit 26c on the side of each dowel bar 23 and adjacent to each dowel bar 23, and a plate jack is inserted into the fourth slit 26d and the fifth slit 26e to expand them. The fourth slit 26d and the fifth slit 26e can be formed at a position spaced apart from each dowel bar 23 toward the center of the box girder in the width direction by a predetermined distance of several centimeters. Specifically, they can be formed at a position spaced apart from the center of the box girder in the width direction of each dowel bar 23 by about 2 to about 10 cm. In the example shown in FIG. 2, the fourth slit 26d and the fifth slit 26e are formed at the boundaries between the upper flanges of the H-shaped steel 20a at both ends and the steel plate 21 between them.

[0044] As a result, the portions adjacent to each dowel bar 23 can be cut out small and removed, and a free surface can be formed on one side of each of the two large block pieces remaining in the center of the box girder. The formation of this free surface makes it possible to move toward the side where the free surface exists, and the plate jack can be expanded to completely detach it from the steel plate 21.

[0045] If the deck 25 is long in the axial direction of the box girder and replacement will take several days, slits (width direction slits) that are perpendicular to the first to fifth slits 26a to 26e and extend in the width direction of the box girder are formed using a road cutter, wall saw, etc., according to the length to be replaced on the day in the axial direction of the box girder. This makes it possible to cut out and remove the deck 25 of the length to be replaced on the day.

[0046] The first to fifth slits 26a to 26e are formed by a cutting device such as a road cutter or a wall saw, and a plate jack is inserted into them. Here, a description will be given using a plate jack as the expansion member, but the expansion member is not limited to the plate jack.

[0047] As shown in Fig. 3, the plate jack 30 is made by welding special steel plates into a bag shape, and can be expanded by supplying pressurized water or other fluid inside. The plate jack 30 is generally about 1 m long and about 2 to 3 mm thick, and expands to a thickness of about 20 to 30 mm when a fluid such as water pressurized to about 4 to 6 MPa is supplied inside. Any fluid such as water or air may be used as long as it can expand the plate jack 30. In the following description, the fluid is assumed to be water.

[0048] The plate jack 30 has a connection port 31 that connects to a water pressure unit (e.g., a pump) as a pressurizing means for pressurizing and supplying water, and water pressurized to a predetermined pressure is supplied to the inside by the water pressure unit. This allows the plate jack 30 to expand by applying water pressure to the inside of the plate jack 30 inserted into the first to fifth slits 26a to 26e in a specified order. The expansion of the plate jack 30 increases the width of the first to fifth slits 26a to 26e, splitting the deck 25 and peeling it off from the upper flange of the H-shaped steel 20a and the steel plate 21. If a width-direction slit is formed, a crack occurs along the width-direction slit during this peeling, and a predetermined length (the length to be replaced on the day) is cut out in the axial direction of the box girder.

[0049] It is preferable to insert the plate jack 30 into each of the first to fifth slits 26a to 26e before applying pressure to the plate jack 30. This is to prevent a previously formed slit 26 from being crushed while applying pressure to the plate jack 30 in one slit 26, making it impossible to insert the plate jack 30.

[0050] The peeled deck 25 can be lifted as individual block pieces by a hoist such as a crane, carried off-site, and cut into smaller pieces off-site. Note that the block pieces do not have to be cut into smaller pieces. Width direction slits can be formed as necessary, and if the axial length of the box girder is short, width direction slits do not have to be formed.

[0051] The work of removing the deck 25 and the procedure of the work will be described in detail with reference to Figs. 4 to 11. This work starts from step 100 of the flow chart shown in Fig. 4, and first, a road cutter is placed at a predetermined position on the deck 25. The road cutter includes a blade as a disk-shaped member having a plurality of blades on its outer periphery, and an electric motor for rotating the blade. Here, the slit 26 is formed using a road cutter as a cutting device, but as long as the slit 26 can be formed, it is not limited to a road cutter and may be a wall saw or the like. When forming a width direction slit, a width direction slit is formed in the deck 25 using a road cutter or the like at a length to be replaced on the day before this work.

[0052] In step 101, the blade of the road cutter is rotated to form a slit 26 of a predetermined depth from the upper surface of the deck 25 to the lower steel plate 21 in a predetermined length in the axial direction of the box girder, and in step 102, a plate jack 30 is inserted into the formed slit. The slit 26 has a cutting depth that does not reach the lower steel plate 21 of the deck 25, and is set to a cutting depth for cutting the lower reinforcing bar 24 of the upper and lower two levels of reinforcing bars 24 embedded in the deck 25. Therefore, if the depth from the upper surface of the deck 25 to the top of the dowel bar 23 is shallower than the depth of the lower reinforcing bar 24, the dowel bar 23 is also cut, and a slit 26 of a predetermined cutting depth is formed.

[0053] In step 103, it is determined whether the required number of slits 26 have been formed in the width direction of the box girder. If the required number of slits 26 have not been formed, the process returns to step 101, and the formation of the slits 26 and the insertion of the plate jacks 30 are repeated. The required number of slits 26 is, for example, at least three, the first to third slits 26a to 26c shown in FIG. 2, and preferably five in total, including the fourth slit 26d and the fifth slit 26e.

[0054] Fig. 5 is a diagram showing the state after the slits 26 are formed and the plate jack 30 is inserted. Fig. 5 is a diagram showing the deck slab 25 as seen from diagonally above, with the direction from the lower right to the upper left being the axial direction of the box girder and the direction from the lower left to the upper right being the width direction of the box girder (direction perpendicular to the axis). Dowel bars 23 are arranged in a row in the axial direction of the box girder at both ends in the width direction of the box girder, and first and second slits 26a, 26b extending in the axial direction of the box girder are formed above the approximate center positions of the dowel bars 23.

[0055] A third slit 26c extending in the axial direction of the box girder is formed in the approximate center between the dowel bars 23 arranged in a row at both ends of the box girder in the width direction. A fourth slit 26d extending in the axial direction of the box girder is formed on the side of the dowel bars 23 between the first slit 26a and the third slit 26c, and a fifth slit 26e extending in the axial direction of the box girder is formed between the second slit 26b and the third slit 26c.

[0056] A plate jack 30 is inserted into each of the first to fifth slits 26a to 26e. Each plate jack 30 is connected to a water pressure unit using a hose or the like so that water pressure can be applied to the inside of the plate jack 30 at any time. The hose may be provided with a valve, and water at a predetermined water pressure can be supplied and the supply can be stopped by opening and closing the valve.

[0057] The first to fifth slits 26a to 26e may be formed in any order. The plate jack 30 is inserted into the first to fifth slits 26a to 26e that have been formed.

[0058] Referring again to FIG. 4, in step 104, in the designated order, first, a water pressure of about 3 MPa is applied as an initial pressure into the plate jack 30 inserted into the third slit 26c formed at approximately the center of the deck 25 in the width direction of the box girder, causing the plate jack 30 to expand, causing a crack to occur in the cutting depth direction of the third slit 26c, splitting the deck 25 into two block pieces, and pushing apart the two block pieces, causing a part of each block piece to peel off from the steel plate 21. Here, for example, about half of the joint surface between each block piece and the steel plate 21 is peeled off. This is one example, and the degree of peeling is not limited to about half.

[0059] FIG. 6 is a diagram showing a state where water pressure is applied to the plate jack 30 inserted into the third slit 26c formed at the approximate center position of the deck 25 in the width direction of the box girder among the multiple slits 26 formed. The third slit 26c is formed from the upper surface of the deck 25 toward the lower iron plate 21 with a cutting depth that does not reach the lower iron plate 21. For this reason, the plate jack 30 inserted into the third slit 26c is installed on the upper surface side of the deck 25, and when it expands at that position, a crack occurs in the cutting depth direction of the third slit 26c, and the width of the third slit 26c on the upper surface side of the deck 25 increases. When the width of the third slit 26c increases, a force that rotates upward acts on the block pieces on both sides of the third slit 26c, and the block pieces that are cracked and split into two peel off from the iron plate 21 from the center side around the third slit 26c.

[0060] Referring again to FIG. 4, in step 105, hydraulic pressure is applied to the plate jack 30 inserted into the first and second slits 26a, 26b formed on the dowel reinforcement 23, causing it to expand and generate cracks along the dowel reinforcement 23, and the block pieces located outside the first and second slits 26a, 26b in the width direction of the box girder are lifted and removed.

[0061] 7 is a diagram showing the state in which water pressure is applied to a plate jack 30 inserted into a first slit 26a formed on the dowel reinforcement 23 of the deck 25 in the width direction of the box girder. When the plate jack 30 inserted into the first slit 26a is expanded, a crack 32 occurs along the outer edge of the dowel reinforcement 23, and the crack 32 extends in a direction inclined with respect to the cutting depth direction of the slit 26a. Therefore, when the deck 25 is removed, concrete remains on the steel plate 21 in a mountain shape with a substantially triangular cross section.

[0062] When the plate jack 30 is expanded, the width of the first slit 26a increases, the crack 32 extends to the iron plate 21, and a force that rotates the block pieces 33a and 33b upward through the first slit 26a acts on the block pieces 33a and 33b, causing the block pieces 33a and 33b to peel off from the iron plate 21. At this time, because the widthwise slits have been formed first, cracks are generated along the widthwise slits, and the block pieces 33a and 33b are cut out to a predetermined length. This also applies to the block pieces 33c to 33e.

[0063] Block piece 33b exists in a form in which both sides in the width direction of the box girder are sandwiched between block pieces 33a and 33c, and only a portion of it has detached from the upper flange of H-shaped steel 20a, so it cannot be lifted and removed as it is.

[0064] On the other hand, since one side surface of the block piece 33a is a free surface, it is completely peeled off from the upper flange of the H-shaped steel 20a.

[0065] Therefore, a hoisting fixture 34 can be attached to, for example, the upper surface of the block piece 33a, and the block piece 33a can be lifted by a hoist using a wire rope 35 and carried out of the site. The hoisting fixture is, for example, a U-shaped shackle with an anchor.

[0066] 4 again, in step 106, hydraulic pressure is applied to the plate jack 30 inserted into the fourth and fifth slits 26d, 26e formed on the sides of the dowel reinforcement 23, causing it to expand, generating cracks in the cutting depth direction of the fourth and fifth slits 26d, 26e, and lifting and removing the block pieces located outside the fourth and fifth slits 26d, 26e in the width direction of the box girder. If the fourth and fifth slits 26d, 26e are not formed on the sides of the dowel reinforcement 23, the process can proceed directly to step 107.

[0067] 8 is a diagram showing the state where water pressure is applied to the plate jack 30 inserted into the fifth slit 26e formed on the side of the dowel reinforcement 23 of the deck slab 25 in the width direction of the box girder. In step 105, the plate jack 30 inserted into the second slit 26b is expanded to split it into two block pieces, and the outer block piece is removed. At this time, the other split block piece 33d has no free surface, so it may be in a partially peeled state and not completely peeled off from the steel plate 21.

[0068] Therefore, in step 106, water pressure is applied to the plate jack 30 inserted into the fifth slit 26e to cause it to expand, thereby completely detaching the block piece 33d from the iron plate 21. After detachment, a hoisting fixture 34 is attached to, for example, the upper surface of the block piece 33d, and the block piece 33d can be lifted with a hoist using a wire rope 35 and carried out of the site.

[0069] Referring again to FIG. 4, in step 107, water pressure is again applied to the plate jack 30 inserted into the third slit 26c formed in approximately the center between the dowel bars 23 of the deck slab 25 in the width direction of the box girder, causing it to expand and generate a crack in the cutting depth direction of the third slit 26c, and the block piece split into two is peeled off from the steel plate 21 and lifted and removed.

[0070] 9 is a diagram showing the state where water pressure is applied again to the plate jack 30 inserted into the third slit 26c formed in the approximate center of the deck slab 25 in the width direction of the box girder. In step 104, a water pressure of about 3 MPa was applied to generate a crack in the cutting depth direction of the third slit 26c, causing it to peel off by about half, but in step 107, water pressure is applied again to completely peel off the split block pieces 33c and 33e from the steel plate 21.

[0071] Fig. 10 is a diagram showing a state in which a block piece is lifted by a hoist and removed from the iron plate 21. Block piece 33e shown in Fig. 9 is attached with a hoisting fixture 34 and is lifted by a hoist such as a crane using a wire rope 35. The lifted block piece 33e is carried out of the site.

[0072] 4 again, once the deck 25 has been removed from the upper flange of the H-shaped steel 20a and from the steel plate 21, the process proceeds to step 108, where the concrete remaining on the steel plate 21, such as around the dowel bars 23, is removed by hand chipping using a hand breaker, WJ method, or the like. Then, in step 109, the work ends.

[0073] Fig. 11 is a diagram showing the state of the upper flange of the H-shaped steel 20a and the steel plate 21 after the deck 25 has been removed. In a composite girder in which the deck 25 is made of reinforced concrete and the H-shaped steel 20 and steel plate 21 corresponding to the box girder are made of different steel materials, the concrete can be peeled off from the steel material by the expansion of the plate jack, so almost no concrete remains on the steel material. Therefore, as shown in Fig. 11, almost no concrete remains on the steel plate 21, and only the concrete 36 formed when the dowel reinforcement 23 was cut remains in a mountain shape on the upper flange of the H-shaped steel 20a.

[0074] In this way, since the amount of concrete 36 remaining on the box girder is small, the work time required for removing it by hand chipping, WJ method, etc. can be significantly reduced.

[0075] Since the plate jack 30 is not made of an expandable material, once it is expanded, it will not contract even if the application of water pressure is stopped. Therefore, the expanded plate jack 30 can be pressed using a press machine such as a hydraulic press to return it to its original flat state.

[0076] The hoisting fittings 34 may be attached to the block pieces before lifting, or may be attached to predetermined positions on the deck slab 25 before splitting into each block piece after the first to fifth slits 26a to 26e are formed and the plate jack 30 is inserted. This is because before the first to fifth slits 26a to 26e are formed, the hoisting fittings 34 get in the way and the first to fifth slits 26a to 26e cannot be formed with the road cutter.

[0077] Before being lifted, the block pieces are cut off from above the box girder and are unstable, making it difficult to attach the lifting hardware 34. For this reason, it is desirable to attach the lifting hardware 34 to each block piece after forming the first to fifth slits 26a to 26e and inserting the plate jack 30, and before splitting the block pieces.

[0078] The simulated composite box girder shown in Figure 2 was 4m wide and 2m long, and the time taken by two workers to remove the deck 25 by hand and by this method was measured. The manual removal took 400 minutes, while the method took only 174 minutes, a reduction of 226 minutes, to less than half the time.

[0079] Therefore, by adopting this method, it is possible to shorten the time required to remove the deck of a box girder composite girder and to remove the deck efficiently.

[0080] So far, the deck removal method of the present invention has been described in detail with reference to the embodiment shown in the drawings, but the present invention is not limited to the above-mentioned embodiment and can be modified within the scope of what a person skilled in the art can imagine, such as other embodiments, additions, modifications, deletions, etc., and any aspect is included in the scope of the present invention as long as it achieves the functions and effects of the present invention.

[0081] Therefore, not only when the dowel bars 23 are arranged in two rows on the box girder, but also when they are arranged in three or more rows, slits 26 can be formed at least between the dowel bars 23 and above the dowel bars 23, plate jacks 30 can be inserted into each of the slits 26, the plate jacks 30 can be expanded, the dowel bars 23 can be split into individual block pieces, the block pieces can be peeled off from the box girder, and the peeled block pieces can be lifted and removed. In this case, like the fourth and fifth slits 26d and 26e shown in Figure 2, further slits 26 can be formed on the sides of the dowel bars 23 arranged in a row, the plate jacks 30 can be inserted, and the plate jacks 30 can be expanded. [Explanation of symbols]

[0082] 10...Road bridge 11...Support 12…Main digit 13…Horizontal girder 14…Floor slab 15…Floor slab waterproof layer 16...Pavement 17...Earth cover 18...protective fence 19…Gibber muscle 20, 20a, 20b…H section steel 21...Iron plate 22…board 23…Gibber muscle 24…Reinforced concrete 25…Floor slab 26...Slit 26a…First slit 26b…Second slit 26c…Third slit 26d…4th slit 26e…5th slit 30…Board jack 31...Connection port 32…Crack 33, 33a to 33e: Block pieces 34…Hanging hardware 35…Wire rope 36…Concrete

Claims

1. A method for removing a deck slab in a composite girder, comprising: forming a gap of a predetermined depth extending in the axial direction of the box girder in a floor slab made of reinforced concrete joined to the box girder, the floor slab having anti-slip members arranged in a row in the axial direction of the box girder at both ends of the box girder in the width direction of the composite girder; A step of inserting an expansion member that expands by applying pressure to the inside of the expansion member into the formed gap; a step of pressurizing and expanding the interior of the expansion member inserted into each of the plurality of gaps formed by repeating the forming step and the inserting step in a specified order, splitting the deck into block pieces, and peeling them off from the box girder and removing them; Including, A method for removing a deck slab, wherein the multiple gaps are formed at least on the anti-slip members arranged in a row at both ends of the box girder in the width direction, and between the anti-slip members arranged in a row at both ends.

2. A method for removing a deck as described in claim 1, wherein in the removal process, in the specified order, first, the expansion member inserted into the gap formed between the shear stop members is expanded, then the expansion member inserted into the gap formed on the shear stop members is expanded, and finally, the expansion member inserted into the gap formed between the shear stop members is expanded again.

3. The method for removing a deck as described in claim 1, wherein the gaps formed between the anti-slip members lined up at both ends include a gap formed at a central position between the anti-slip members lined up at both ends, and a gap formed between the anti-slip members lined up at both ends at a position spaced a predetermined distance from the anti-slip members lined up at each end.

4. A method for removing a deck as described in claim 3, wherein in the removal step, in the specified order, first, the expansion member inserted into the gap formed in the central position is expanded, then the expansion member inserted into the gap formed on the anti-slip member is expanded, then the expansion member inserted into the gap formed at a position a predetermined distance away from the anti-slip member is expanded, and finally, the expansion member inserted into the gap formed in the central position is expanded again.

5. The composite girder has two of the box girders, The deck removal method according to claim 1 or 3, wherein the forming step, the inserting step, and the removing step are performed for each of the two box girders.

6. The deck removal method according to claim 1 or 3, further comprising the step of forming a second gap of a predetermined depth extending in the width direction of the box girder in the deck on the box girder between the anti-slip members.

7. The reinforcing bars embedded in the deck are arranged vertically in two tiers, one above the other, The deck removal method according to claim 1 or 3, wherein in the step of forming the gap, a gap is formed that is deep enough to extend from the top surface of the deck beyond the lower rebar and not reach the box girder.

8. The method for removing a deck slab described in claim 1 or 3, wherein in the removing step, each time the block piece is peeled off from the box girder, the block piece peeled off from the box girder is lifted and removed from the box girder.

9. The method for removing a deck slab according to claim 1 or 3, further comprising a step of pressurizing water by a pressurizing means and supplying the water into the expansion member.

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