Method for designing floor-slab joint part

Abstract

To provide a design method of a floor slab joint part for designing the floor slab joint part capable of saving labor in construction.SOLUTION: In a method for designing a floor slab joint part 1, a plate anchoring type reinforcement 3 having an anchoring plate 31 at its tip is projected on an end face 21 of each of two concrete floor slabs 2, 2 arranged at a predetermined interval, and the plate anchoring type reinforcement 3 of one concrete floor slab 2 and the plate anchoring type reinforcement 3 of the other concrete floor slab 2 are alternately arranged, and a filling material 4 is filled between the concrete floor slabs 2 to join them. A reinforced layer 41 which is a layer of the filling material 4 in which the plate anchoring type reinforcement 3 is arranged and a non-reinforced layer 42 which is a layer of the filling material 4 in which the plate anchoring type reinforcement 3 is not arranged are respectively modeled into a reinforced layer cross section model and a non-reinforced layer cross section model, a proof stress is calculated for each of the reinforced layer 41 and the non-reinforced layer 42, and the maximum proof stress is determined based on the proof stress of the reinforced layer 41 and the proof stress of the non-reinforced layer 42.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for designing joints between precast decks. [Background technology]

[0002] Precast slabs laid consecutively are connected via filler concrete or filler mortar (hereinafter simply referred to as "filling material") poured at the slab joints. At the joints between precast slabs, it is standard for loop reinforcement to protrude from the end faces of the precast slabs.

[0003] For example, Patent Document 1 discloses a deck joint structure in which the end faces of precast decks with protruding loop reinforcement are butted together with a specified gap between them, distribution bars are arranged to intersect with the loop reinforcement, and filler concrete is poured into the gap between the end faces.A method for calculating the required joint length (joint width) for deck joint structures using loop reinforcement has also been proposed.

[0004] However, with the conventional deck joint structure, after the precast deck is laid, it is time-consuming to place the distribution bars inside the loop reinforcement. Furthermore, because there are limitations on the processing dimensions of the loop reinforcement, considering the overlap of the loop reinforcement, the reduction in the thickness of the precast deck members is also limited. Furthermore, the dimensions of the loop reinforcement increase the gaps between the precast decks, requiring more filler concrete, which takes time to pour and hinders the shortening of the construction period.

[0005] Therefore, there are cases where the joint is rationalized by changing the loop shape. For example, Patent Document 2 discloses a deck slab joint structure in which reinforcing bars protruding from the end faces of deck slabs installed at a predetermined interval are joined together with open lap joints. In the deck slab joint structure of Patent Document 2, anchors with a width larger than the diameter of the reinforcing bars are formed at the tips of the reinforcing bars protruding from the end faces of the deck slab. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-236258 [Patent Document 2] Patent Publication No. 2021-055531 Summary of the Invention [Problem to be solved by the invention]

[0007] The deck joint structure of Patent Document 2 enables labor saving during construction. However, a rational design method for determining the specifications of the joint width and the joint rebars for deck joints that use joint rebars other than loop rebars has not been established. An object of the present invention is to propose a method for designing deck slab joints that enables labor savings during construction. [Means for solving the problem]

[0008] In order to solve such problems, the present invention provides a design method for a deck joint in which plate-fixed reinforcing bars with fixing plates at the ends are protruded from each end face of two concrete decks arranged at a predetermined distance, and the plate-fixed reinforcing bars of one concrete deck and the plate-fixed reinforcing bars of the other concrete deck are arranged so that they alternate, and the concrete decks are joined by filling the gap between them. The design method for deck slab joints of the present invention includes a modeling step in which the reinforced layer, which is the layer of the filler material in which the plate-anchored reinforcing bars are arranged, and the unreinforced layer, which is the layer of the filler material in which the plate-anchored reinforcing bars are arranged, are modeled as a reinforced layer cross-sectional model and an unreinforced layer cross-sectional model, respectively; a reinforced layer strength calculation step in which strain based on displacement is calculated for the reinforced layer cross-sectional model, and the strength of the reinforced layer is calculated based on a determination of whether the filler material will undergo compressive failure due to the force received from the anchoring plate, and whether shear failure will occur; an unreinforced layer strength calculation step in which strain based on displacement is calculated for the unreinforced layer cross-sectional model, and the strength of the unreinforced layer is calculated based on a determination of whether tensile failure will occur along the diagonal of the failure area of ​​the reinforced layer; a maximum strength determination step in which the maximum strength is determined based on the strength of the reinforced layer and the strength of the unreinforced layer; and a comparison step in which the maximum strength is compared with the design load.

[0009] According to this design method for deck joints, the shape and width of deck joints and the specifications of plate-anchored reinforcing bars can be rationally designed according to the site conditions, etc. It is desirable to determine the specifications of the plate-anchored reinforcing bars and the spacing between the concrete deck slabs by changing the structural specifications of the plate-anchored reinforcing bars, the reinforcing pitch of the plate-anchored reinforcing bars, or the spacing between the concrete deck slabs based on the results of the comparison process, and repeating the modeling process, the reinforced layer strength calculation process, the unreinforced layer strength calculation process, the maximum strength determination process, and the comparison process. It is also desirable for the filler to be fiber-reinforced mortar or fiber-reinforced concrete. Furthermore, it is desirable for the anchoring plate to be rectangular. [Effects of the Invention]

[0010] According to the design method for deck slab joints of the present invention, it is possible to rationally design deck slab joints that do not use loop reinforcement. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a perspective view showing a deck joint of the present embodiment. [Figure 2] 1 is a flowchart showing the steps of a design method for a deck joint. [Figure 3] FIG. 1 is a perspective view showing an outline of modeling of a joint. [Figure 4] 1(a) is an explanatory diagram showing the stress state of a cross-sectional model of a reinforced concrete layer, and FIG. 1(b) is an explanatory diagram showing the stress state of a cross-sectional model of a non-reinforced concrete layer. [Figure 5] FIG. 1 is an explanatory diagram of the definition of deformation in a reinforced concrete layer. [Figure 6] FIG. 1 is an explanatory diagram of the definition of deformation in a non-reinforced concrete layer. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this embodiment, bridge deck replacement work will be described. In the deck replacement work of this embodiment, two concrete decks 2 are arranged with a predetermined interval (gap 11) between them, and a filler material 4 is filled in the gap 11 to join them. Figures 1 and 2 show the joint (slab joint 1) between the concrete decks 2.

[0013] The concrete slab 2 is a precast member made of reinforced concrete. Vertical and horizontal reinforcement bars are arranged inside the concrete slab 2. In addition, plate-anchored reinforcing bars 3 protrude from each of the end faces 21 of the two concrete slabs 2, which are spaced apart. The plate-anchored reinforcing bars 3 have anchoring plates 31 at their tips. The end faces 21 of the concrete slab 2 may be formed with shear keys (e.g., recesses or protrusions) to improve the transfer of force between the filler material 4 and the concrete slab 2. The end faces 21 may also be roughened to improve the bond with the filler material 4.

[0014] As shown in Figure 1, in the deck joint 1, plate-fixed reinforcing bars 3 protruding from the end face 21 of one concrete deck 2 and plate-fixed reinforcing bars 3 protruding from the end face 21 of the other concrete deck 2 are arranged alternately (staggered) in a plan view. In this embodiment, the plate-fixed reinforcing bars 3 are arranged so that the plate-fixed reinforcing bars 3 protruding from the end face 21 of the other concrete deck 2 are arranged near the middle of the two plate-fixed reinforcing bars 3, 3 protruding from the end face 21 of one concrete deck 2. In other words, the intervals between the alternately arranged plate-fixed reinforcing bars 3 are equal.

[0015] In this embodiment, the plate-mounted reinforcing bar 3 is formed by fixing a rectangular steel plate (anchoring plate 31) to the tip of the reinforcing bar 32. The anchoring plate 31 is 40 mm long x 70 mm wide (the width is at least twice the diameter of the reinforcing bar) and 16 mm thick. The method for fixing the anchoring plate 31 is not limited, and it may be fixed by, for example, welding, friction welding, or gas pressure welding. Furthermore, if the reinforcing bar 32 is threaded, the reinforcing bar 32 may be screwed into a nut fixed to the anchoring plate 31 or into a screw hole formed in the anchoring plate 31. Note that the anchoring plate 31 is not limited to a rectangular shape and may be, for example, a circle, an ellipse, or a polygon other than a rectangle. Furthermore, the dimensions of the anchoring plate 31 may be determined appropriately.

[0016] Fiber reinforced mortar is used as the filler 4. The specifications (mixture, design standard strength, etc.) of the fiber reinforced mortar are not limited, but in this embodiment, the design standard strength of the fiber reinforced mortar is 40 N / mm 2 As a result, 2.3 vol.% of steel fibers are mixed in. The type (mixture, strength, amount of mixed fibers, etc.) of the fiber reinforced mortar (filling material 4) is not limited.

[0017] The structure of the joint (slab joint 1) between concrete slabs 2 in slab replacement work is determined by the following design method. The design method for the slab joint 1 of this embodiment will be described below. Figure 2 shows the design method for the slab joint 1. As shown in Figure 2, the design method for the slab joint 1 includes a specification setting process S1, a modeling process S2, a reinforced reinforcement layer strength calculation process S3, a non-reinforced reinforcement layer strength calculation process S4, a maximum strength determination process S5, and a comparison process S6. In the specification setting step S1, the specifications of the deck joint 1 (size of the gap between the concrete decks 2, gap between the plate-fixed reinforcing bars 3, reinforcing bar diameter, dimensions of the fixing plate 31, etc.) are set.

[0018] The modeling step S2 is a step of modeling the joint. Figure 3 shows a modeled deck joint 1. In the deck joint 1, the ultimate stress state differs between the filler 4 between the anchor plates 31 and the filler 4 on the surface side where no anchor plates 31 are installed. Therefore, the stress state model used in the joint strength equation is considered by dividing it into a reinforced layer 41, which is a layer of filler 4 where plate-anchored reinforcing bars 3 are installed, and an unreinforced layer 42, which is a layer of filler 4 where plate-anchored reinforcing bars 3 are not installed, as shown in Figure 3. In this embodiment, the reinforced layer 41 is modeled as a reinforced layer cross-sectional model, and the unreinforced layer 42 is modeled as a unreinforced layer cross-sectional model.

[0019] The stress state is shown in Figure 4. As shown in Figure 4(a), it is assumed that in the reinforced layer 41, the filler material 4 is subjected to force from the anchor plate 31, resulting in uniform compression and shear deformation. On the other hand, in the non-reinforced layer 42, it is assumed that uniform cracks occur along the diagonal of the fracture area of ​​the reinforced layer 41, as shown in Figure 4(b). It is assumed that the member is in a plane stress state.

[0020] In this embodiment, the reinforcing bar layer 41 is a layer in the middle in the height (thickness) direction of the deck slab joint 1, and has a height from the upper end to the lower end of the anchoring plate 31. On the other hand, the non-reinforcing bar layer 42 is a layer from the upper surface of the reinforcing bar layer 41 to the upper surface of the filler material 4, and a layer from the lower surface of the reinforcing bar layer 41 to the lower surface of the filler material 4. In this embodiment, it is modeled as a three-layer structure in which the non-reinforcing bar layers 42 are arranged above and below the reinforcing bar layer 41. Note that when the plate-anchored reinforcing bars 3 are arranged in two levels, upper and lower, the upper and lower levels are inspected or designed independently.

[0021] The reinforcing bar layer strength calculation step S3 is a step of calculating the strength of the reinforcing bar layer 41. In the reinforcing bar layer strength calculation step S3, first, the strain based on the displacement is calculated for the reinforcing bar layer cross-sectional model. The deformation field in the reinforcing bar layer cross-sectional model can be defined as shown in FIG. 5. FIG. 5 is an explanatory diagram of the definition of the deformation of the reinforcing bar layer 41. The strain ε in the fracture region of the reinforcing bar layer cross-sectional model x ,ε y ,γ xy is given by Equations 1 to 3. xy is the engineering shear strain, where x1, x2, and θ are given geometrically as in Equations 4 to 6.

[0022]

number

[0023] From Mohr's strain circle, the principal strain is given by Equation 7. By substituting Equations 1 to 6 into Equation 7, Equation 8 is obtained. From Equation 8, the strain ε 1,3 Calculate.

[0024]

number

[0025] Next, the principal stress σ is calculated using the calculated strain. 1,3 Calculate the principal stress σ 1,3 is given by Equations 9 and 10. In addition, the internal work W tcis given by Equation 11, assuming a linear elastic body.

[0026]

number

[0027] Next, the principal stress σ 1,3 is used to determine whether the filler material 4 will undergo compression failure due to the force received from the anchor plate 31, and whether it will undergo shear failure. For compression failure, the failure criterion is set as the point at which the minimum principal stress reaches the compressive strength. For shear failure, the failure criterion is set as the point at which the Mohr stress edge contacts the failure criterion shown in Equation 12. If it is determined that compression failure will occur, a flag (compression failure flag) is set to indicate that the maximum strength has been reached due to compression failure. If it is determined that shear failure will occur, a flag (shear failure flag) is set to indicate that the maximum strength has been reached due to shear failure.

[0028]

number

[0029] Then, the strength of the reinforcing bar layer 41 is calculated based on the judgment result. c is given by Equation 13. G is the volume of the destruction area (mm 3 ) External force work W ex and internal work W c are equal, the formula 14 is given. From the above, the external force F1 in the reinforcing bar layer 41 when the displacement u is applied is calculated.

[0030]

number

[0031] The unreinforced layer strength calculation step S4 is a step of calculating the strength of the unreinforced layer 42. The deformation field in the unreinforced layer cross-sectional model can be defined as shown in Figure 6. Figure 6 is an explanatory diagram of the definition of the deformation of the unreinforced layer 42. In the unreinforced layer strength calculation step S4, first, the strain based on the displacement is calculated for the unreinforced layer cross-sectional model. The strain in the failure region of the unreinforced layer 42 is given by equations 15, 16, and 17. Here, the displacement u is equal to the displacement u in the failure region of the reinforced layer cross-sectional model. From the Mohr strain circle shown in Equation 2, the principal strain ε 1,3 is given by Equation 18.

[0032]

number

[0033] Next, the calculated strain is used to calculate the principal stress σ 1,3 Calculate the principal stress σ 1,3 is given by Equations 9 and 10. In addition, the internal work W tc is given by Equation 11, assuming a linear elastic body.

[0034]

number

[0035] Next, the principal stress σ 1,3 , and determines whether tensile failure will occur along the diagonal of the fracture area of ​​the reinforcing bar layer 41. If tensile failure is determined to occur, a flag indicating the occurrence of a crack (crack occurrence flag) is set. Here, the failure criterion at the time of crack occurrence is set to the point when the maximum principal stress reaches the tensile strength, and calculations are performed. On the other hand, steel fibers are mixed into the filler material 4, and the tensile stress in the direction perpendicular to the crack continues even after the crack occurs. Therefore, the minimum principal stress after the crack occurs is calculated assuming that the tensile strength is maintained.

[0036] Then, based on the determination result, the bearing strength of the non-reinforced reinforced layer 42 is calculated. As with the reinforced reinforced reinforced layer 41, the external force F2 in the non-reinforced reinforced reinforced layer 42 when a displacement u is applied is calculated from Equations 19 and 20.

[0037]

number

[0038] In the maximum strength determination step S5, the maximum strength is determined based on the strength of the reinforced layer 41 and the strength of the non-reinforced layer 42. First, the acting force F (= F1 + F2) of the plate-anchored reinforcing bar 3 is calculated by summing the external forces F1 and F2 at each cross section at the time when one of the failure criteria (compression failure, shear failure, or crack occurrence) set for each layer is reached.

[0039] Next, the crack occurrence flag is judged. That is, if the crack occurrence flag is set in the non-reinforced layer strength calculation step S4, the external force F2 at that time is determined to be the crack occurrence load. Next, the maximum strength flag is judged. That is, if the compression failure flag or shear failure flag is set in the reinforced layer strength calculation step S3, the external force F1 at that time is determined to be the maximum strength F u If the maximum strength flag is not set, the process returns to the specification setting step.

[0040] In the comparison process S6, the maximum strength F u and the design load. Depending on the results of the comparison process S6 (e.g., when the design load exceeds the maximum strength), the process returns to the specification setting process S1, and the conditions of the deck joint 1 (structural specifications of the plate-anchored reinforcing bars, reinforcing pitch of the plate-anchored reinforcing bars, or spacing between concrete deck slabs, etc.) are changed, and the modeling process S2, the reinforced reinforced layer strength calculation process S3, the unreinforced reinforced layer strength calculation process S4, the maximum strength determination process S5, and the comparison process S6 are repeated.

[0041] Next, the construction procedure for the deck joint 1 will be explained. First, the concrete deck 2 is laid. The concrete deck 2 is laid by placing one concrete deck 2 in a predetermined position and then suspending the other concrete deck 2 from above. At this time, a gap 11 of a predetermined size is formed between the end faces 23 of adjacent concrete deck slabs 2. In addition, the plate-anchored reinforcing bars 3 protruding from the end face 21 of one concrete deck slab 2 are arranged between the plate-anchored reinforcing bars 3 protruding from the end face 21 of the other concrete deck slab 2.

[0042] Once the concrete slab 2 has been laid, the sides and bottom of the gap 11 are covered with formwork (not shown) as necessary. Note that the formwork on the bottom of the gap 11 may be omitted if there is no risk of fiber-reinforced mortar leaking out from below the gap 11, such as when a main girder is installed below the gap 11.

[0043] Once the gap 11 is covered with formwork, the gap 11 is filled with filler material 4. It is desirable to manufacture the filler material 4 on-site. The filler material 4 is cured, and once it has reached the required strength, the formwork is removed (see Figure 1).

[0044] According to the design method of the deck slab joint 1 of this embodiment, the shape and width of the deck slab joint 1 and the specifications of the plate-anchored reinforcing bars 3 and the like can be rationally designed according to the site conditions and the like. In addition, the reinforced layer 41 in which plate-fixed reinforcing bars 3 are arranged and the unreinforced layer 42 on the surface side where plate-fixed reinforcing bars 3 are not arranged are modeled separately for strength calculation, allowing for rational design.

[0045] Furthermore, according to the deck joint 1 of this embodiment, the plate-anchored reinforcing bars 3 with anchoring plates 31 formed at their ends are arranged, which makes it possible to shorten the anchoring length of the plate-anchored reinforcing bars 3, thereby reducing the gaps 11 between the concrete deck slabs 2 (end faces 23). This reduces the amount of filler material to fill the gaps 11, shortening the time required for pouring the filler material 4 and ultimately shortening the construction period.

[0046] The reinforcing bars 32 protruding from the end face 23 are straight and do not require bending. This eliminates the cost required for bending the plate-anchored reinforcing bars 3. Furthermore, because there is no need to consider bending the plate-anchored reinforcing bars 3, there is greater freedom in setting the thickness of the concrete slab 2, such as making the thickness 2 220 mm or less. By thinning the concrete slab 2, it becomes easier to handle and the amount of filler material 4 to be filled in the gaps 11 can be reduced, which shortens the construction period.

[0047] Furthermore, by using fiber-reinforced mortar as the filler 4 to fill the gaps 11, the filler 4 exhibits high tensile resistance, making it possible to omit the use of distribution reinforcement. As a result, there is no need to place distribution reinforcement in the narrow gaps 11, which reduces the amount of work required during construction compared to conventional joint structures.

[0048] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each component can be appropriately modified without departing from the spirit of the present invention. In the above embodiment, the spacing between the plate-fixed reinforcing bars 3 protruding from the opposing end faces 23 and arranged alternately is equal, but the spacing between the plate-fixed reinforcing bars 3 protruding from the opposing end faces 23 does not necessarily have to be equal.

[0049] The filler 4 (fiber reinforced mortar) may be manufactured on-site, or may be manufactured in a plant outside the site and delivered. Furthermore, the filler 4 is not limited to fiber reinforced mortar, and fiber reinforced concrete may be used as long as workability and filling properties are ensured. [Explanation of symbols]

[0050] 1 Floor slab joint 11 Gap 2 Concrete deck 21 End face 3 Plate-anchored reinforcing bars 31 Fixing plate 32 Reinforced concrete 4 Filling material 41 Reinforced concrete layer 42 Unreinforced concrete layer S1 Specification setting process S2 Modeling process S3 Reinforced layer strength calculation process S4 Non-reinforced layer strength calculation process S5 Maximum proof stress determination process S6 Comparison process

Claims

1. A design method for a deck joint in which plate-fixed reinforcing bars with fixing plates at their tips are protruding from the end faces of two concrete decks arranged at a predetermined interval, and the plate-fixed reinforcing bars of one concrete deck and the plate-fixed reinforcing bars of the other concrete deck are arranged so as to alternate, and filler material is filled between the concrete decks to join them, a modeling step of modeling a reinforced layer, which is a layer of the filler material in which the plate-fixed reinforcing bars are arranged, and a non-reinforcing layer, which is a layer of the filler material in which the plate-fixed reinforcing bars are not arranged, into a reinforced layer cross-sectional model and a non-reinforcing layer cross-sectional model, respectively; a reinforcing bar layer strength calculation step of calculating strain based on displacement of the reinforcing bar layer cross-sectional model, and calculating the strength of the reinforcing bar layer based on a determination of whether the filler material will undergo compressive failure due to the force received from the anchoring plate and a determination of whether the filler material will undergo shear failure; a non-reinforced layer strength calculation step of calculating strain based on displacement for the non-reinforced layer cross-sectional model and calculating the strength of the non-reinforced layer based on a determination of whether tensile failure occurs along the diagonal of the failure area of ​​the reinforced layer; a maximum strength determination step of determining a maximum strength based on the strength of the reinforced reinforcement layer and the strength of the non-reinforced reinforcement layer; A method for designing a deck slab joint, characterized by carrying out a comparison process of comparing the maximum strength with a design load.

2. A design method for a deck joint as described in claim 1, characterized in that the structural specifications of the plate-anchored reinforcing bars, the reinforcing pitch of the plate-anchored reinforcing bars, or the spacing between the concrete deck slabs are changed depending on the results of the comparison process, and the modeling process, the reinforced reinforced layer strength calculation process, the unreinforced reinforced layer strength calculation process, the maximum strength determination process, and the comparison process are repeated.

3. 2. The design method for a deck joint according to claim 1, wherein the filler material is fiber-reinforced mortar or fiber-reinforced concrete.

4. The design method for a deck joint according to claim 1, wherein the anchor plate is rectangular.

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