Deck replacement structure and deck replacement method

Abstract

To provide a floor slab replacing structure and a floor slab replacing method that suppress opening at a construction joint part of a replacing part constructed on an existing floor slab to prevent it from becoming a structural weak point.SOLUTION: A floor slab replacing structure 1 includes: a preceding replacing layer 3 formed on an upper surface of an existing floor slab 2; a following replacing layer 4 formed on the upper surface of the existing floor slab 2 in a state where an end surface 41 is abutted to an end surface 31 of the preceding replacing layer 3; and a reinforcement material 5 provided across the preceding replacing layer 3 and the following replacing layer 4. On the end surface 31 of the preceding replacing layer 3, a step with a lower side protruding toward the following replacing layer 4 side is formed. The end surface 41 of the following replacing layer 4 has an upper side protruding toward the preceding replacing layer 3 side to engage with the step formed on the end surface 31 of the preceding replacing layer 3. Furthermore, the reinforcement material 5 is a lattice-shaped face material parallel to the upper surface of the existing floor slab 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a deck replacement structure and a deck replacement method. [Background technology]

[0002] In road bridges that use reinforced concrete decks, fatigue deterioration due to traffic loads, etc. can occur in the existing decks. Furthermore, because the existing decks were constructed based on the design standards at the time of construction, there are cases where the amount of rebar is insufficient or the deck thickness is insufficient compared to current design standards. Therefore, repairs to the existing deck may be required to ensure that the structure complies with current design standards. One method of repairing existing decks is the deck replacement method, which involves pouring new steel fiber reinforced concrete on top of the existing concrete deck to increase its thickness and integrate it, thereby restoring or improving the deck's load-bearing capacity (see, for example, Patent Document 1). Patent document 2 also discloses a deck replacement method in which the concrete forming the top surface of an existing deck (top surface concrete) is removed and fiber-reinforced concrete with a dense matrix is ​​poured to the same thickness as the area from which the concrete was removed. In the deck replacement method, when continuously pouring fiber-reinforced concrete on an existing deck, construction joints must be created at regular intervals, but the bridging effect of the steel fibers contained in the steel fiber-reinforced concrete cannot be expected at the construction joints, and there is a risk of gaps occurring. Therefore, the standard practice for construction joints is to use an adhesive applied to the edge (vertical) surface of the previously formed replacement layer (thickened concrete layer or replacement concrete layer) to integrate it with the subsequent replacement layer (see Non-Patent Document 1). However, adhesive alone can cause gaps in the construction joints due to the tensile force acting on them, which can allow water and salt to seep in, accelerating the deterioration of the deck slab. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-149244 [Patent Document 2] Japanese Patent Publication No. 2020-172751 [Non-patent literature]

[0004] [Non-Patent Document 1] “Design Guidelines Volume 2 Bridge Maintenance Edition”, July 2019, East Japan Expressway Co., Ltd., Central Japan Expressway Co., Ltd., West Japan Expressway Co., Ltd., p.5-30~5-33 Summary of the Invention [Problem to be solved by the invention]

[0005] The objective of the present invention is to propose a deck replacement structure and a deck replacement construction method that suppresses the opening of the construction joints of replacement parts constructed on an existing deck, thereby preventing them from becoming structural weaknesses. [Means for solving the problem]

[0006] The deck replacement structure of the present invention for solving the above problem comprises a leading replacement layer formed on the top surface of the existing deck, a following replacement layer formed on the top surface of the existing deck in a state where it is butted against the end face of the leading replacement layer, and a reinforcing material provided across the leading replacement layer and the following replacement layer. The end face of the leading replacement layer has a step formed on its lower side protruding toward the following replacement layer, and the end face of the following replacement layer has an upper side protruding toward the leading replacement layer so as to engage with the step formed on the end face of the leading replacement layer. The reinforcing material is a lattice-shaped surface material parallel to the top surface of the existing deck. The preceding and succeeding replacement layers are preferably made of fiber-reinforced concrete or fiber-reinforced mortar, and the reinforcing material is preferably carbon fiber-reinforced plastic or aramid fiber-reinforced plastic.

[0007] The deck replacement method of the present invention includes a removal step of removing the top surface concrete of the existing deck, a formwork installation step of installing a formwork on the existing deck after the removal step, a first pouring step of pouring replacement concrete on one side of the formwork to form a preceding replacement layer, a formwork removal step of removing the formwork, and a second pouring step of pouring replacement concrete on the other side of the preceding replacement layer to form a succeeding replacement layer. The formwork includes a first formwork placed on the top surface of the existing deck and a second formwork placed above the first formwork. The other end face of the second formwork protrudes to the other side beyond the other end face of the first formwork. In the formwork installation step, a reinforcing member consisting of a lattice-shaped surface material protruding to one side and the other side of the formwork is interposed between the first formwork and the second formwork.

[0008] According to this deck replacement structure and deck replacement method, the reinforcing material installed horizontally in the construction joint between the preceding and succeeding replacement layers ensures the strength against the tensile force acting on the construction joint, thereby suppressing the opening of the construction joint and ultimately preventing water and salt from penetrating through the construction joint. In addition, since a step including a surface parallel to the top surface of the existing deck or a horizontal plane is formed in the construction joint between the preceding replacement layer and the succeeding replacement layer, water and salt are less likely to penetrate than in conventional joints where vertical surfaces are butted together.

[0009] Waterproofing can be further improved by providing an adhesive application process in which adhesive is applied to the upper surface (a surface parallel to the upper surface of the existing deck slab or a horizontal surface) of the protruding portion of the end of the preceding replacement layer formed by removing the second formwork before the second pouring process. In addition, by placing a cushioning material between the underside of the first formwork and the top surface of the existing deck slab, it is possible to prevent gaps from forming between the uneven existing deck slab and the first formwork, and to prevent replacement concrete (fresh concrete) from leaking outside the formwork when pouring. Furthermore, if a surface material having multiple recesses or multiple protrusions is fixed to the end face and bottom face of one side of the second formwork before the first pouring step, multiple protrusions and recesses will be formed on the end face of the preceding replacement layer (the abutment surface with the succeeding replacement layer), further improving the bonding between the preceding replacement layer and the succeeding replacement layer. In addition, a paving process may be provided in which a base layer is formed directly on the upper surfaces of the preceding replacement layer and the following replacement layer, and a surface layer is formed on the upper surface of the base layer. Since the construction joint between the preceding replacement layer and the following replacement layer has excellent waterproofing properties, by forming the base layer directly without providing a waterproof layer on the upper surface of the construction joint, the effort and cost associated with constructing a waterproof layer can be eliminated. [Effects of the Invention]

[0010] According to the deck replacement structure and deck replacement method of the present invention, it is possible to suppress the opening of the construction joints of the replacement part constructed on the existing deck, thereby preventing them from becoming structural weaknesses. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are diagrams showing a deck slab replacement structure according to an embodiment of the present invention, in which (a) is a longitudinal section and (b) is an AA section. [Figure 2] 1 is a flowchart showing the steps of the deck replacement method. [Figure 3] This is a cross-sectional view showing each step of the deck replacement method, where (a) is the removal step, (b) is the formwork installation step, and (c) is the first pouring step. [Figure 4] 4 is a cross-sectional view showing each step of the deck replacement method following FIG. 3, where (a) is the formwork removal step, (b) is the second concrete pouring step, and (b) is the paving step. [Figure 5] FIG. [Figure 6] 10 is a photograph showing the experimental results. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this embodiment, a slab replacement structure 1 is described for an existing road bridge, in which a deteriorated portion (top surface concrete) on the top of an existing slab 2 is removed and fiber-reinforced concrete is poured into this removed portion to repair the existing slab 2. Figure 1 shows the slab replacement structure 1 of this embodiment. As shown in Figure 1(a), the deck replacement structure 1 of this embodiment comprises a preceding replacement layer 3 formed on the upper surface of the existing deck slab 2, a succeeding replacement layer 4 formed on the upper surface of the existing deck slab 2 in a state of abutting against the end face 31 of the preceding replacement layer 3, and a reinforcing material 5 provided across the preceding replacement layer 3 and the succeeding replacement layer 4.

[0013] The preceding replacement layer 3 is made of fiber-reinforced concrete poured on the top surface (the area where concrete has been removed) of the existing deck slab 2. A step is formed on the end face (end) 31 of the preceding replacement layer 3, with the lower portion 32 (the portion below the reinforcing material 5) protruding further toward the succeeding replacement layer 4 than the upper portion 33. The succeeding replacement layer 4 is made of fiber-reinforced concrete of the same composition as the preceding replacement layer 3, and is poured onto the top surface (the area where concrete has been removed) of the existing deck slab 2. A step is formed on the end surface (end) 41 of the succeeding replacement layer 4, with the upper portion 43 (the portion above the reinforcing material 5) protruding further toward the preceding replacement layer 3 than the lower portion 32. The protruding length of the upper portion 43 of the succeeding replacement layer 4 is equal to the protruding length of the lower portion 32 of the preceding replacement layer 3. In other words, the step on the end surface 41 of the succeeding replacement layer 4 is formed to engage with the step on the end surface 31 of the preceding replacement layer 3. As shown in Figures 1(a) and (b), the reinforcement 5 is a lattice-shaped surface material parallel to the top surface of the existing deck slab 2. The reinforcement 5 is made of carbon fiber reinforced plastic (CFRP). One end of the reinforcement 5 is embedded in the preceding replacement layer 3, and the remaining part of the reinforcement 5 is embedded in the succeeding replacement layer 4. The reinforcement 5 is placed on the top surface of the lower part 32 of the preceding replacement layer 3.

[0014] The construction method (slab replacement method) for the slab replacement structure 1 will be explained below. Figure 2 shows the steps of the slab replacement method. As shown in Figure 2, the slab replacement method includes a removal process S1, a formwork installation process S2, a first pouring process S3, a formwork removal process S4, an adhesive application process S5, a second pouring process S6, and a paving process S7. Figures 3 and 4 show each process of the slab replacement method. As shown in Figure 3(a), the removal process S1 is a process of removing the deteriorated portion 21 on the upper surface of the existing deck slab 2. Specifically, after cutting away a few centimeters of the upper surface of the existing deck slab 2, the cut surface is cut away using a water jet or the like. Prior to cutting away the existing deck slab 2, the pavement 8 laid on top of the existing deck slab 2 is cut away.

[0015] The formwork installation step S2 is a step of installing a formwork 6 on the existing deck 2. As shown in Figure 3(b), the formwork 6 has a first formwork 61 placed on the top surface of the existing deck slab 2 from which the deteriorated portion 21 has been removed, and a second formwork 62 placed above the first formwork 61. One end face of the second formwork 62 (the right side in Figure 3(b)) protrudes to one side beyond one end face of the first formwork 61. When installing the formwork 6, the reinforcing material 5 is interposed between the first formwork 61 and the second formwork 62. The reinforcing material 5 has a width (length in the direction perpendicular to the construction joint) greater than that of the formwork 6, and both ends of the reinforcing material 5 protrude to one side and the other side of the formwork 6 (left side in Figure 3(b)), respectively. Furthermore, when installing the formwork 6, a buffer material 7 is interposed between the underside of the first formwork 61 and the top surface of the existing deck slab 2. The buffer material 7 is not limited to any material as long as it can absorb unevenness on the top surface of the existing deck slab 2 and prevent poured concrete from flowing out, and for example, a closed-cell sponge material or a resin-based elastic plate material (e.g., a rubber plate) can be used. A textured surface material 63 having a plurality of recesses or protrusions formed thereon is fixed to one end face and bottom face of the second formwork 62. The textured surface material 63 may be made of, for example, a polypropylene mesh material or a net-woven cloth.

[0016] As shown in FIG. 3(c), the first pouring step S3 is a step of pouring replacement concrete C onto one side of the formwork 6 to form the preliminary replacement layer 3. Steel fiber reinforced concrete is used for the replacement concrete C. In the first pouring step S3, the replacement concrete C is poured while wrapping around one end of the reinforcing material 5 (the portion protruding on one side of the formwork 6). The formwork removal step S4 is a step of removing the formwork 6 (including the buffer material 7), as shown in FIG. 4(a). The formwork removal step S4 is performed after the replacement concrete C has hardened and developed the strength required for the preceding replacement layer 3 (strength that allows the formwork 6 to be removed). When the formwork 6 is removed, the preceding replacement layer 3 is formed, with the lower portion 32 protruding more than the upper portion 33, as shown in FIG. 4(a). The upper surface 32a of the lower portion 32 and the tip surface 33a of the upper portion 33 of the preceding replacement layer 3 have unevenness formed by removing the uneven surface material 63.

[0017] The adhesive application step S5 is a step of applying adhesive to the end face of the preceding replacement layer 3. The adhesive is applied to the adhesive area 31a (see FIG. 4(a)). Specifically, the adhesive is applied to the upper surface (horizontal surface) 32a of the protruding portion (lower portion 32) at the end of the preceding replacement layer 3 formed by removing the second formwork 62, and to the tip surface (vertical portion) 33a of the upper portion 33. An epoxy resin adhesive is used as the adhesive. In this embodiment, the adhesive is applied to the end face 31 (adhesive area 31a) of the preceding replacement layer 3, but the method for applying the adhesive is not limited thereto and may be, for example, spraying. Note that before applying the adhesive, a primer may be applied to the adhesive area 31a and then the adhesive is applied. As shown in FIG. 4(b), the second pouring step S6 is a step of pouring replacement concrete C on the other side of the preceding replacement layer 3 to form the subsequent replacement layer 4. In the second pouring step S6, the replacement concrete C is poured while encasing the other end of the reinforcing material 5 (the portion protruding from the preceding replacement layer 3). For the replacement concrete C, steel fiber reinforced concrete of the same composition as the steel fiber reinforced concrete used to form the preceding replacement layer 3 is used. As shown in Figure 4(c), the paving step S7 is a step of forming a pavement 8 on the preceding replacement layer 3 and the succeeding replacement layer 4. The pavement 8 is formed by forming a base layer 81 directly on the top surfaces of the preceding replacement layer 3 and the succeeding replacement layer 4, and then forming a surface layer 82 on top of this base layer 81. The construction of the pavement 8 is carried out after the preceding replacement layer 3 and the succeeding replacement layer 4 have been cured.

[0018] According to the deck replacement structure 1 and deck replacement method of this embodiment, the reinforcing material 5 laid horizontally across the construction joint between the preceding replacement layer 3 and the succeeding replacement layer 4 ensures the strength against the tensile force acting on the construction joint. This prevents the construction joint from opening, which in turn prevents water and salt from penetrating through the construction joint. In addition, since a step including a horizontal plane is formed in the construction joint between the preceding replacement layer 3 and the succeeding replacement layer 4, water and salt are less likely to penetrate than in conventional construction joints where vertical surfaces are butted together. Since adhesive is applied to the upper surface (horizontal surface) 32a of the lower portion 32 of the preceding replacement layer 3, water penetration through the construction joints is prevented, further improving waterproofing. The upper surface 32a of the lower portion 32 of the preceding replacement layer 3 and the tip surface 33a of the upper portion 33 are uneven surfaces formed by the uneven surface material 63, so the contact area with the end surface 41 of the following replacement layer 4 is increased, further improving bonding. In addition, the unevenness formed on the contact surfaces makes it difficult for moisture to penetrate. As described above, according to the deck replacement structure 1 and deck replacement method of this embodiment, the waterproofing of the construction joints is excellent, so the base layer 81 can be formed directly without providing a waterproof layer on the top surface of the construction joints. Therefore, the effort and cost associated with constructing a waterproof layer can be saved. Furthermore, in this embodiment, a lightweight, corrosion-resistant material (carbon fiber reinforced plastic material) is used as the reinforcing material 5, so that even if moisture or salt penetrates, the material will not corrode. A buffer material 7 is interposed between the underside of the first formwork 61 and the top surface of the existing deck slab 2, which prevents gaps from forming between the uneven existing deck slab 2 and the first formwork 61, and prevents replacement concrete C (fresh concrete) from flowing outside the formwork 6.

[0019] The following shows the results of an experiment conducted on the deck replacement structure 1 of this embodiment. In this experiment, in order to confirm the effect of suppressing openings in the construction joints of the deck replacement structure 1 of this embodiment, a test specimen 10 was created in which the base 20 (existing deck 2) and the replacement layer 11 were integrated, and the test specimen 10 was placed so that the replacement layer 11 was on the tensile side, and a bending strength test was conducted in accordance with JISA1106. The test specimen 10 is shown in Figure 5. Table 1 shows the materials used in the experiment, Table 2 shows the mix proportions of the base concrete that constitutes the base 20, and Table 3 shows the mix proportions of the replacement concrete that constitutes the replacement layer 11.

[0020] [Table 1]

[0021] [Table 2]

[0022] [Table 3]

[0023] First, the base 20 was formed using base concrete with the mix shown in Table 2. The base 20 had a width of 10 cm, a height of 6 cm, and a length of 40 cm. Next, replacement concrete with the mix shown in Table 3 was poured onto the top surface of the base 20 to form the replacement layer 11 (the preceding replacement layer 30 and the following replacement layer 40). The replacement layer 11 had a width of 10 cm, a height of 4 cm, and a length of 40 cm. The replacement layer 11 consisted of the preceding replacement layer 30 and the following replacement layer 40, and had a construction joint (the boundary between the preceding replacement layer 30 and the following replacement layer 40) in the center of its length. A step was formed in the construction joint so that the lower portion 32 of the preceding replacement layer 30 protruded toward the following replacement layer 40, and a reinforcing material 5 was arranged across the preceding replacement layer 30 and the following replacement layer 40. The reinforcing material 5 is a lattice-shaped surface material made of carbon fiber reinforced plastic with a thickness of 4 mm and a nominal cross-sectional area of ​​26.4 mm. 2, tensile strength is 1400N / mm 2 The upper surface 32a of the lower portion 32 of the preceding re-cast layer 30 and the tip surface 33a of the upper portion 33 are uneven surfaces, and the following re-cast layer 40 was formed with adhesive applied to the upper surface 32a of the lower portion 32 and the tip surface 33a of the upper portion 33. A primer was applied before the adhesive was applied. The upper surface 32a of the lower portion 32 of the preceding re-cast layer 30 and the tip surface 33a of the upper portion 33 are formed with a plurality of uneven surfaces by the uneven surface material 63.

[0024] The bending test was carried out on the specimen 10 in accordance with JISA1106 "Test method for bending strength of concrete." In the experiment, a load P was applied so that a tensile force was applied to the replacement layer 11 side. The test results (photograph) are shown in Figure 6. In the photograph of Figure 6, the base 20 is on top and the replacement layer 11 is on the bottom. As a result of the test, the specimen 10 (replacement layer 11) fractured at a position (outside the trisection point of the specimen 10) away from the construction joint (the center of the specimen 10: around 20 cm), as shown in Figure 6. In other words, the construction joint of the specimen 10 was not a weak spot. From the above experiments, it was confirmed that the deck slab replacement structure 1 of this embodiment can suppress openings in the construction joints even when a tensile force is applied.

[0025] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be modified as appropriate within the scope of the invention. In the above embodiment, the thickness of the preceding replacement layer 3 and the succeeding replacement layer 4 is described as being the same as the thickness of the removed portion of the existing deck slab 2, so that the thickness of the deck is the same before and after the renovation, but the thickness of the preceding replacement layer 3 and the succeeding replacement layer 4 may be greater or less than the thickness of the removed portion of the existing deck slab 2. In the above embodiment, the preceding replacement layer 3 and the succeeding replacement layer 4 are described as being made of fiber-reinforced concrete, but the materials constituting the preceding replacement layer 3 and the succeeding replacement layer 4 are not limited to this and may be made of, for example, fiber-reinforced mortar. In the above embodiment, a case has been described in which carbon fiber reinforced plastic (CFRP) is used for the reinforcing material 5, but the material constituting the reinforcing material 5 is not limited to this, and for example, aramid fiber reinforced plastic (AFRP) may also be used. The uneven surface material 63 may be used as needed. After removing the deteriorated portion 21 on the upper surface of the existing deck slab 2 (after the removal process S1), the upper surface of the removed existing deck slab 2 may be moistened or adhesive may be applied before pouring the steel fiber concrete (replacement concrete C) (before the first pouring process S3 and the second pouring process S6). [Explanation of symbols]

[0026] 1 Floor slab replacement structure 2 Existing deck 3. Leading replacement layer 31 End face 4 Latest replacement layer 41 End face 5 Reinforcement 6. Formwork 61 First Formwork 62 Second Formwork 63 Textured surface material 7 Cushioning material 8. Pavement 81 Base layer 82 Surface layer

Claims

1. A preceding replacement layer formed on the top surface of the existing deck slab; A subsequent replacement layer formed on the top surface of the existing deck slab with its end face abutting against the end face of the preceding replacement layer; A deck replacement structure comprising a reinforcing material provided across the preceding replacement layer and the following replacement layer, The end surface of the preceding replacement layer has a step formed on the lower side protruding toward the following replacement layer, The end surface of the following replacement layer protrudes upward toward the preceding replacement layer so as to engage with a step formed on the end surface of the preceding replacement layer, A deck replacement structure characterized in that the reinforcing material is a lattice-shaped surface material parallel to the upper surface of the existing deck.

2. The deck replacement structure according to claim 1, characterized in that the preceding replacement layer and the following replacement layer are made of fiber-reinforced concrete or fiber-reinforced mortar.

3. 3. The deck replacement structure according to claim 1, wherein the reinforcing material is made of carbon fiber reinforced plastic material or aramid fiber reinforced plastic material.

4. a removal process of removing the top surface concrete of the existing deck slab; a formwork installation process for installing a formwork on the existing floor slab; A first pouring step of pouring replacement concrete on one side of the formwork to form a preceding replacement layer; a formwork removal step of removing the formwork; A second pouring step of pouring replacement concrete on the other side of the preceding replacement layer to form a subsequent replacement layer, The formwork includes a first formwork placed on the upper surface of the existing floor slab after the removal process, and a second formwork placed above the first formwork, One end surface of the second formwork protrudes to one side more than one end surface of the first formwork, A deck replacement method characterized in that, in the formwork installation process, a reinforcing material consisting of a lattice-shaped surface material extending on one side and the other side of the formwork is interposed between the first formwork and the second formwork.

5. A deck replacement method as described in claim 4, characterized in that it includes an adhesive application process for applying adhesive to the upper surface of the protruding portion of the end of the preceding replacement layer formed by removing the second formwork before the second pouring process.

6. A deck replacement method as described in claim 4 or claim 5, characterized in that a buffer material is interposed between the underside of the first formwork and the upper surface of the existing deck after the removal process.

7. A deck replacement method described in any one of claims 4 to 6, characterized in that before the first pouring step, a surface material having multiple recesses or multiple protrusions formed thereon is fixed to the end face and bottom face on one side of the second formwork.

8. A deck replacement method according to any one of claims 4 to 7, characterized in that it includes a paving process in which a base layer is formed directly on the upper surfaces of the preceding replacement layer and the following replacement layer, and a surface layer is formed on the upper surface of the base layer.

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