Joining structure of composite floor slab

Abstract

To provide a joint structure of a composite floor slab capable of suppressing the occurrence of de-bonding and cracking of a boundary surface between concrete and a filling material of the composite floor slab.SOLUTION: A first reinforcing bar 12 extended from the end face 15a of a concrete part 15 of each composite floor slab 10 and buried in a filling concrete 19 between the concrete parts 15 has a diameter-expanded fixing part 12a at a tip end part, and since the tip side is formed to be bent obliquely downward in the bridge-axis direction, the fixing part 12a can be positioned on the center side in the vertical direction where tensile stress is smaller than that on the upper surface side of the filling concrete 19, the occurrence of de-bonding and cracking on the boundary surface between the concrete part 15 and the filling concrete 19 due to the stress concentration on the fixing part 12a can be suppressed, and the durability of the joint part of the composite floor slab 10 can be improved.SELECTED DRAWING: Figure 8

Description

Technical Field

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[0001] The present invention relates to a joining structure of a composite floor slab used for bridges such as general roads and highways.

Background Art

[0002] Conventionally, as a composite floor slab used for bridge erection, for example, a steel bottom plate manufactured in a factory is fixed on the main girder at the site, and reinforcing bars are arranged on the bottom plate and concrete is placed to construct the floor slab (see, for example, Patent Document 1). In the construction using such a composite floor slab, since concrete can be placed directly on the bottom plate, there is no need to use a formwork, and the efficiency of on-site work can be improved. However, in the construction method of placing concrete for the entire floor slab at the site, since the placement of concrete at the site and a long curing period are required, the shortening of the construction period could not be sufficiently achieved.

[0003] Also, there is known a method of improving the efficiency of on-site construction and shortening the construction period by using a precast composite floor slab manufactured integrally with concrete in a factory in advance (see, for example, Patent Document 2). In this construction method, the composite floor slab is installed on the main girder, and packing concrete is placed between the end faces of adjacent composite floor slabs. In order to ensure the load transmission force between the composite floor slabs, a plurality of reinforcing bars are extended from the end face of the composite floor slab into the packing portion, and the bonding strength between the composite floor slab and the packing concrete is increased by each reinforcing bar.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the joint structure of the aforementioned precast composite floor slab, a radially enlarged anchoring section is formed at the tip of the reinforcing bar extending from the end face of the concrete, and the anchoring section increases the tensile bearing pressure of the reinforcing bar against the infill concrete. However, when bending stress occurs in each composite floor slab and tensile force is applied to the reinforcing bar in the infill concrete, stress concentrates at the anchoring section of the reinforcing bar, which may cause delamination at the boundary between the concrete of the composite floor slab and the infill concrete, or cracks in the infill concrete originating from the anchoring section of the reinforcing bar.

[0006] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a joint structure for a composite floor slab that can suppress the occurrence of peeling and cracking at the interface between the concrete and the filling material of the composite floor slab. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a composite floor slab joining structure in which the ends of the bottom plates of composite floor slabs, formed by placing reinforcing bars extending in a predetermined direction on a steel bottom plate and pouring concrete, are connected, the ends of the reinforcing bars are placed between the concrete end faces of adjacent composite floor slabs, and a filling material is filled between the concrete end faces to join the composite floor slabs in a predetermined direction, wherein the reinforcing bars placed between the concrete end faces have a radially enlarged anchoring portion at their tip, and the tip is formed to bend diagonally downward with respect to the predetermined direction. Furthermore, the anchoring portion is formed to be located on the vertically central side where the tensile stress is smaller than on the upper surface side of the gap-filling material, and adjacent reinforcing bars in a direction perpendicular to the predetermined direction are arranged so that wide and narrow spacings between reinforcing bars alternate. It is.

[0008] As a result, the ends of the reinforcing bars placed between the concrete end faces of each composite deck slab are formed so that their tips are bent diagonally downward with respect to the bridge axis. This positions the anchoring point on the vertical center side, where the tensile stress is smaller than on the upper side of the infill material, thereby suppressing the occurrence of spalling and cracking at the interface between the concrete of the composite deck slab and the infill material due to stress concentration at the anchoring point. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the occurrence of peeling and cracking at the interface between the concrete and the filling material of the composite floor slab, thereby improving the durability of the joint of the composite floor slab. [Brief explanation of the drawing]

[0010] [Figure 1] Plan view of a composite floor slab showing a first embodiment of the present invention [Figure 2] Plan view of the main parts of the composite floor slab [Figure 3] Side cross-sectional view of the main part of the composite floor slab [Figure 4] Side cross-sectional view showing the joining process of composite floor slabs. [Figure 5] Side cross-sectional view showing the joining process of composite floor slabs. [Figure 6] Side cross-sectional view showing the joining process of composite floor slabs. [Figure 7] Side cross-sectional view showing the joining process of composite floor slabs. [Figure 8] Side cross-sectional view showing the joint state of the composite floor slab. [Figure 9] Schematic side cross-sectional view showing the joint of the composite floor slab. [Figure 10] A schematic side cross-sectional view showing a comparative example of a composite floor slab joint. [Figure 11] Side cross-sectional view of the joint portion of a composite floor slab showing a second embodiment of the present invention. [Figure 12] Side cross-sectional view of the joint of a composite floor slab showing a third embodiment of the present invention. [Modes for carrying out the invention]

[0011] Figures 1 to 9 show a first embodiment of the present invention, which, for example, shows a composite deck slab used in bridges on public roads and expressways.

[0012] The composite deck slab 10 shown in the figure is installed on the main girder 20 and is erected by being joined to other composite deck slabs 10 in the direction of the bridge axis.

[0013] The composite bridge deck 10 is composed of a steel bottom plate 11 forming the bottom surface of the bridge deck body, a plurality of first reinforcing bars 12 as force distribution bars extending in the bridge axis direction, a plurality of second reinforcing bars 13 as main reinforcing bars extending in a direction perpendicular to the bridge axis, a plurality of supplementary stiffening members 14 fixed on the bottom plate 11, and a concrete portion 15 placed on the bottom plate 11. The bottom plate 11 is connected to the bottom plates 11 of other composite bridge decks 10 by bolts 16 and attaching plates 17.

[0014] The bottom plate 11 is made of a flat steel plate, and a plurality of bolt insertion holes 11a for inserting bolts 16 are provided on both ends in the bridge axis direction. Each bolt insertion hole 11a is arranged at intervals in a direction perpendicular to the bridge axis, and is provided so as to penetrate the bottom plate 11 in the thickness direction. Further, a plurality of studs 11b to be embedded in the concrete portion 15 or in the filling concrete 19 described later are provided on the bottom plate 11.

[0015] Each first reinforcing bar 12 is arranged in a direction perpendicular to the bridge axis so as to be located above the bottom plate 11, and both ends thereof extend outside the concrete portion 15. Fixing portions 12a for fixing to the filling concrete described later are provided at the ends of each first reinforcing bar 12, and the fixing portions 12a are formed so as to expand in the radial direction of the first reinforcing bar 12. Further, the tip side of each first reinforcing bar 12 is formed so as to bend obliquely downward with respect to the bridge axis direction. Each first reinforcing bar 12 is provided so as to be alternately arranged one by one in a direction perpendicular to the bridge axis with each first reinforcing bar 12 of other adjacent composite bridge decks 10 as shown in FIG. 2. In this case, each first reinforcing bar 12 is arranged such that the first reinforcing bar 12 of one composite bridge deck 10 and the first reinforcing bar 12 of the other composite bridge deck 10 form wide intervals A1 and narrow intervals A2 alternately, and the bolts 16 are located below the wide intervals A1.

[0016] Each second reinforcing bar 13 is arranged in the bridge axis direction so as to be located above the bottom plate 11, and is arranged above each first reinforcing bar 12.

[0017] Each stiffening member 14 is made of steel (for example, channel steel) extending in a direction perpendicular to the bridge axis and is arranged at intervals from one another in the direction of the bridge axis.

[0018] The concrete section 15 is cast onto the base plate 11 using formwork in a factory or the like, forming a floor slab that spans the entire width of the base plate 11. The concrete section 15 contains embedded first reinforcing bars 12, second reinforcing bars 13, stiffeners 14, and studs 11b, with the ends of the base plate 11 and the ends of the first reinforcing bars 12 extending horizontally outward from the end face 15a of the concrete section 15. In this case, each first reinforcing bar 12 is positioned above the vertical center of the concrete section 15. The concrete section 15 is also provided with multiple holes 15b through which shear prevention members of the main girder 20 are inserted.

[0019] The bolts 16 are high-strength bolts and are temporarily fixed to the base plate 11 before the composite floor slab 10 is brought to the construction site. At that time, as shown in Figure 3, the bolts 16 are inserted from below into the bolt insertion holes 11a of the base plate 11 and temporarily fixed to the base plate 11 by screwing in temporary fixing nuts 16a from above the base plate 11. For the temporary fixing nuts 16a, for example, a ring-shaped member made of synthetic resin with a thickness smaller than that of the splice plate 17 is used.

[0020] The splice plate 17 is made of a steel plate extending perpendicular to the bridge axis and is formed to rest on the upper surface of the end side of each bottom plate 11 across adjacent composite deck plates 10. The splice plate 17 is provided with a plurality of bolt insertion holes 17a through which bolts 16 are inserted, and the bolt insertion holes 17a are formed with an inner diameter larger than the outer diameter of the temporary fixing nuts 16a.

[0021] The composite floor slab 10, constructed as described above, is manufactured in a factory or similar facility and then transported to the construction site. At that time, high-strength bolts 16 are temporarily fixed to the bottom plate 11 of the composite floor slab 10.

[0022] The joining process of the composite floor slab 10 will be explained below with reference to Figures 4 to 8.

[0023] First, the composite deck slabs 10 that have been delivered to the site are installed on the main girders 20 so as shown in Figure 5, positioned in one direction along the bridge axis, relative to the composite deck slabs 10 that have been previously installed on the main girders 20 as shown in Figure 4. At this time, the bottom plates 11 of the composite deck slabs 10 are butted together in the direction along the bridge axis with a small gap between them, and a gap-filling area is formed between the concrete sections 15 of each composite deck slab 10. In addition, anti-slip members (not shown) for the main girders 20 are placed in the holes 15b of the concrete section 15.

[0024] Next, as shown in Figure 6, a splice plate 17 is placed on the upper end surface of the bottom plate 11 of each composite floor slab 10, and a nut 16b is screwed onto the bolt 16 that is pre-fixed to the bottom plate 11 and temporarily tightened. At this time, since the temporary fixing nut 16a is placed inside the bolt insertion hole 17a of the splice plate 17, the temporary fixing nut 16a does not interfere with the nut 16b.

[0025] In this case, in adjacent composite floor slabs 10, as shown in Figure 2, the bolts 16 are located below the wide spacing A1 between each first reinforcing bar 12. Therefore, as shown in Figure 7, the nuts 16b are tightened onto the bolts 16 using a tightening tool 30 (for example, a shear wrench with a long socket) that can be inserted through the wide spacing A1 from above each first reinforcing bar 12.

[0026] Subsequently, as shown in Figure 8, multiple reinforcing bars 18 extending perpendicular to the bridge axis are placed on the first reinforcing bars 12 located in the infill areas between each concrete section 15, spaced apart in the bridge axis direction, and infill concrete 19 is poured into the infill areas between each concrete section 15 as infill material. For example, fast-setting concrete is used for the infill concrete 19. As a result, each first reinforcing bar 12 in the infill area becomes integrated with the infill concrete 19, and the bonding strength between each composite deck slab 10 is increased by the adhesion force and bearing pressure (force resisting horizontal shear force) generated between each first reinforcing bar 12 and the infill concrete 19. At that time, the adhesion force and bearing pressure are further increased by the anchoring portion 12a provided at the end of each first reinforcing bar 12, so as shown in Figure 3, the length L of the overlapping portion in the bridge axis direction between the first reinforcing bars 12 of each composite deck slab 10 can be made shorter than when reinforcing bars without anchoring portions 12a are used.

[0027] Furthermore, by filling the holes 15b in the concrete section 15 with non-shrink mortar, the shear-preventing member (not shown) of the main girder 20 and the concrete section 15 are integrated.

[0028] Here, as shown in Figure 9, when a load F is applied to each composite slab 10, and bending stress is generated in the infill concrete 19, a tensile force P is applied to the first reinforcing bar 12 within the infill concrete 19. At this time, since the tip of the first reinforcing bar 12 is bent diagonally downward with respect to the bridge axis direction, the height distance D from the anchoring portion 12a at the tip to the upper surface of the infill concrete 19 becomes longer compared to the case where the tip of the first reinforcing bar 12 is not bent, as shown in the comparative example in Figure 10. As a result, the anchoring portion 12a is located on the vertical center side where the tensile stress is smaller than on the upper surface side of the infill concrete 19, thus suppressing the peeling of the interface between the end face 15a of the concrete portion 15 of the composite slab 10 and the infill concrete 19 (especially the upper part of the first reinforcing bar 12) and the occurrence of cracks originating from the anchoring portion 12a due to stress concentration at the anchoring portion 12a. In this case, it is preferable to ensure a horizontal distance C of, for example, 10 mm to 60 mm between the boundary and the anchoring portion 12a in order to prevent peeling.

[0029] As described above, according to this embodiment, the first reinforcing bar 12, which extends from the end face 15a of the concrete portion 15 of each composite deck slab 10 and is embedded in the infill concrete 19 between the concrete portions 15, has an enlarged anchoring portion 12a at its tip, and is formed so as to bend diagonally downward with respect to the bridge axis direction. Therefore, the anchoring portion 12a can be positioned on the vertical center side where the tensile stress is smaller than on the upper side of the infill concrete 19, thereby suppressing the occurrence of peeling and cracking at the interface between the concrete portion 15 and the infill concrete 19 due to stress concentration at the anchoring portion 12a, and improving the durability of the joint of the composite deck slab 10.

[0031] Furthermore, although the above embodiment shows the composite deck slabs 10 being joined together in the direction of the bridge axis, it can also be applied when joining them in a direction perpendicular to the bridge axis.

[0032] Figure 11 shows a second embodiment of the present invention, and components equivalent to those in the first embodiment are denoted by the same reference numerals.

[0033] In this embodiment, the end faces 15c of the concrete portion 15 of each composite floor slab 10 are formed to have an uneven surface. As a result, the interface between the infill concrete 19 filled between the end faces 15c of the concrete portion 15 and the concrete portion 15 becomes uneven, and the adhesion force of the interface is increased.

[0034] According to this embodiment, the adhesion force at the interface between the concrete portion 15 and the infill concrete 19 can be increased, thereby suppressing the peeling of the interface between the concrete portion 15 and the infill concrete 19 of the composite floor slab 10 (especially the upper portion of the first reinforcing bar 12) due to stress concentration at the anchoring portion 12a, and preventing the occurrence of cracks originating from the anchoring portion 12a, thereby improving the durability of the joint of the composite floor slab 10.

[0035] In the second embodiment described above, the entire end face of the concrete portion 15 is shown to be formed in an uneven manner. However, it is also possible to form an uneven manner only on the upper portion of the first reinforcing bar 12 on the end face of the concrete portion 15.

[0036] Figure 12 shows a third embodiment of the present invention, and components equivalent to those in the first embodiment are denoted by the same reference numerals.

[0037] In this embodiment, adhesive 15d is applied to the end face of the concrete portion 15 of each composite floor slab 10. As a result, the filler concrete 19 that is filled between the end faces of the concrete portions 15 is bonded to the end faces of the concrete portions 15 by the adhesive 15d, and the adhesion force at the interface between the concrete portions 15 and the filler concrete 19 is increased.

[0038] According to this embodiment, the adhesion force at the interface between the concrete portion 15 and the infill concrete 19 can be increased, thereby suppressing the peeling of the interface between the concrete portion 15 and the infill concrete 19 of the composite floor slab 10 (especially the upper portion of the first reinforcing bar 12) due to stress concentration at the anchoring portion 12a, and preventing the occurrence of cracks originating from the anchoring portion 12a, thereby improving the durability of the joint of the composite floor slab 10.

[0039] In the second embodiment described above, the adhesive 15d is applied to the entire end face of the concrete portion 15. However, the adhesive may be applied only to the upper portion of the first reinforcing bar 12 on the end face of the concrete portion 15.

[0040] Furthermore, in the second and third embodiments, similar to the first embodiment, the tip of the first reinforcing bar 12 is formed to bend diagonally downward with respect to the bridge axis direction. However, at least one of the inventions of the second and third embodiments can also be applied to cases where the tip of the first reinforcing bar 12 is not bent.

[0041] Furthermore, the above embodiments are merely examples of the present invention, and the present invention is not limited to those described above. [Explanation of symbols]

[0042] 10... Composite floor slab, 11... Base plate, 12... First reinforcing bar, 12a... Anchorage section, 15... Concrete section, 15a, 15c... End faces, 15d... Adhesive, 19... Infill concrete.

Claims

1. In a composite floor slab joining structure in which the ends of the bottom plates of a composite floor slab, formed by placing reinforcing bars extending in a predetermined direction on a steel bottom plate and pouring concrete, are connected, the ends of the reinforcing bars are placed between the concrete end faces of adjacent composite floor slabs, and a filling material is filled between the concrete end faces to join the composite floor slabs in a predetermined direction, The reinforcing bars placed between the end faces of the concrete have a radially expanding anchoring portion at their tip, and are formed so as to bend diagonally downward with respect to the predetermined direction, and the anchoring portion is positioned on the vertically central side where the tensile stress is lower than on the upper side of the filler material. The reinforcing bars adjacent to each other in a direction perpendicular to the predetermined direction are arranged such that wide and narrow spacings between them alternate. A composite floor slab joining structure characterized by the following features.

2. At least the upper portion of the reinforcing bars on the end face of the concrete is formed to have an uneven surface. The composite floor slab joining structure according to feature 1.

3. At least the upper portion of the reinforcing bar on the end face of the concrete and the gap-filling material are bonded together with adhesive. A composite floor slab joining structure according to claim 1 or 2.

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