Joining structure of composite floor slab

Abstract

To provide a junction structure of composite slabs that can suppress occurrence of cracks in filling concrete even if a bending moment occurs in filled portions between individual composite slabs.SOLUTION: Since reinforcing members 19 that generate resistance force in space next to filling concrete 20 are buried in the filling concrete 20 between individual composite slabs 10 so as to restrict upward movement of the end side of first reinforcing bars 12, even if bending moment occurs in the filling concrete 20, it is possible to suppress the rise of the end parts of the first reinforcing bars 12. Therefore, it is possible to effectively suppress occurrence of cracks in the filling concrete 20 above the first reinforcing bars 12, and it is possible to improve durability of junctions of the composite slabs.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a joint 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 construction, for example, a steel bottom plate manufactured in a factory is fixed on the main girder at the site, and reinforcement 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 achieved sufficiently.

[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. However, in order to ensure the load transmission force between the composite floor slabs, a plurality of reinforcement 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 reinforcement 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 aforementioned precast composite floor slab joint structure, when a bending moment occurs in the gap between each composite floor slab, a force is applied to the overlapping portion of the reinforcing bars extending from the end face of each composite floor slab, causing the end of each reinforcing bar to rise from a horizontal position like scissors, which could lead to the occurrence of horizontal cracks in the concrete gap above the reinforcing bars.

[0006] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a joint structure for composite floor slabs that can suppress the occurrence of cracks in the infill concrete even when a bending moment occurs in the infill portion between each composite floor slab. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a steel base plate extending in a predetermined direction multiple In a composite floor slab joining structure in which the ends of the bottom plates of composite floor slabs formed by arranging reinforcing bars 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 gap-filling material is filled between the concrete end faces to join composite floor slabs in a predetermined direction, the structure includes a reinforcing member embedded in the gap-filling material that generates resistance between itself and the gap-filling material to restrict the upward movement of the ends of the reinforcing bars, Each of the aforementioned reinforcing bars is arranged such that the spacing between them is alternating between wide and narrow sections in a horizontal direction perpendicular to the predetermined direction. The reinforcing member extends in a horizontal direction perpendicular to the reinforcing bars such that a portion of it is located above the reinforcing bars, and is bent downwards so that both ends in the longitudinal direction are located below the reinforcing bars, and is formed to generate vertical resistance between itself and the filler material, with the bent portion of the reinforcing member positioned at the wider sections of the reinforcing bars. It is.

[0008] As a result, reinforcing members that create resistance between the filling material and the filling material are embedded in the gaps between each composite floor slab, restricting the upward movement of the ends of the reinforcing bars. Therefore, even if a bending moment occurs in the filling material, the upward movement of the ends of the reinforcing bars is suppressed. [Effects of the Invention]

[0009] According to the present invention, even when a bending moment occurs in the filling material, the upward movement of the reinforcing bars at the ends within the filling material can be suppressed, thereby effectively preventing the occurrence of cracks in the filling material above the reinforcing bars and improving the durability of the joints 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] Cross-sectional view in the direction of the arrow on line XX [Figure 10] Cross-sectional view in the direction of line XX, showing a modified example of the first embodiment. [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] Cross-sectional view in the direction of the arrow on the YY line [Figure 13] Cross-sectional view in the direction of the YY line showing a modified example of the second embodiment. [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 1 and is erected by being joined to other composite deck slabs 10 in the direction of the bridge axis.

[0013] The composite bed slab 10 is composed of a steel bottom plate 11 forming the bottom surface of the bed slab body, a plurality of first reinforcing bars 12 as force-distributing 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 part 15 placed on the bottom plate 11. The bottom plate 11 is connected to the bottom plates 11 of other composite bed slabs 10 by bolts 16 and attachment 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. The bolt insertion holes 11a are arranged at intervals in a direction perpendicular to the bridge axis, and are 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 part 15 or in the filling concrete 20 described later are provided on the bottom plate 11.

[0015] Each of the first reinforcing bars 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 part 15. Fixing parts 12a for fixing to the filling concrete described later are provided at the ends of each of the first reinforcing bars 12, and the fixing parts 12a are formed so as to expand in the radial direction of the first reinforcing bar 12. Each of the first reinforcing bars 12 is provided so as to be alternately arranged one by one in a direction perpendicular to the bridge axis with the first reinforcing bars 12 of other adjacent composite bed slabs 10 as shown in FIG. 2. In this case, the first reinforcing bars 12 are arranged such that the first reinforcing bars 12 of one composite bed slab 10 and the first reinforcing bars 12 of the other composite bed slab 10 form wide intervals A1 and narrow intervals A2 alternately, and the bolts 16 are positioned below the wide intervals A1.

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

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

[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 temporarily 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, which serve as main reinforcement bars 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 from each other in the direction of the bridge axis. Multiple reinforcing members 19 extending perpendicular to the bridge axis are also placed, and infill concrete 20, made of high-strength concrete, is poured into the infill areas between each concrete section 15 as infill material. As a result, each first reinforcing bar 12 in the infill area becomes integrated with the infill concrete 20, and the bonding force and bearing pressure (force resisting horizontal shear force) generated between each first reinforcing bar 12 and the infill concrete 20 increases the bonding strength between each composite deck slab 10. In this case, the anchoring portion 12a provided at the end of each first reinforcing bar 12 further increases the adhesion force and bearing pressure. 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] The reinforcing member 19 consists of a U-shaped member having bent portions 19a that extend downward at both ends in the longitudinal direction (perpendicular to the bridge axis), and is arranged to straddle multiple first reinforcing bars 12 as shown in Figure 9. The reinforcing member 19 can be formed from various materials such as deformed steel bars, round steel, FRP, wire, cable, wire mesh, fiber mesh, etc., as long as the bent portions 19a provide vertical resistance to the infill concrete 20. Furthermore, each reinforcing member 19 is arranged in the direction perpendicular to the bridge axis so that the bent portions 19a are close to each other, and is provided in multiple rows with intervals in the direction of the bridge axis. In this case, each reinforcing member 19 is arranged so that the bent portion 19a is located between the wide intervals A1 of the first reinforcing bars 12. In addition, multiple types of members with different lengths in the direction perpendicular to the bridge axis may be used for each reinforcing member 19, but they may all be members of the same length.

[0028] 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 1 and the concrete section 15 are integrated.

[0029] Here, when a bending moment is generated in the infill concrete 20 due to the load on each composite floor slab 10, a force is applied to the overlapping portions of the first reinforcing bars 12 extending from the end faces 15a of each composite floor slab 10, causing each end of the first reinforcing bar 12 to rise up from a horizontal position like scissors. At that time, the resistance force between the reinforcing member 19 embedded in the infill concrete 20 and the infill concrete 20 restricts the upward movement of the end of the first reinforcing bar 12.

[0030] As described above, according to this embodiment, a reinforcing member 19 that generates resistance between itself and the infill concrete 20 between each composite floor slab 10 is embedded in the infill concrete 20 so as to restrict the upward movement of the end side of the first reinforcing bar 12. Therefore, even if a bending moment occurs in the infill concrete 20, the upward movement of the end side of the first reinforcing bar 12 can be suppressed. This effectively suppresses the occurrence of cracks in the infill concrete 20 above the first reinforcing bar 12, and improves the durability of the joint of the composite floor slab.

[0031] Furthermore, a part of the reinforcing member 19 is First Reinforcement bars 12 Since it is positioned above the first reinforcing bar 12 and the other parts are positioned below the first reinforcing bar 12, the part positioned below the first reinforcing bar 12 can generate sufficient resistance between it and the infill concrete 20.

[0032] In this case, the reinforcing member 19 extends in a direction perpendicular to the first reinforcing bar 12 and is formed to have bent portions 19a that bend downward on both ends in the longitudinal direction. Therefore, the reinforcing member 19 can be placed on the first reinforcing bar 12 so as to straddle it, and the work of placing the reinforcing member 19 on site can be easily carried out.

[0033] Furthermore, in addition to high-strength concrete, various high-performance concretes such as short-fiber reinforced concrete, ultra-high-strength fiber-reinforced concrete, latex-modified rapid-setting concrete, non-porous concrete, geopolymer concrete, and geopolymer cement concrete can be used for the infill concrete 20, thereby further enhancing the crack prevention effect of the infill concrete 20.

[0034] In the first embodiment described above, the bent portion 19a of the reinforcing member 19 was shown to be formed to extend only downward. However, as shown in the modified example of the bent portion 19b in Figure 10, it may also be formed in a roughly rectangular shape, bending downward and with its lower end bending horizontally (in a direction perpendicular to the first reinforcing bar 12). This allows resistance to be obtained not only from the downward-extending portion of the bent portion 19b but also from the horizontally-extending portion, thereby more effectively restricting the upward movement of the end of the first reinforcing bar 12.

[0035] Figures 11 and 12 show a second embodiment of the present invention, and components equivalent to those in the previous embodiment are denoted by the same reference numerals.

[0036] In this embodiment, instead of the reinforcing bars 18 that serve as the main reinforcement embedded in the infill concrete 20, a reinforcing member 21 made of reinforcing bars (deformed steel bars) equivalent to those of the main reinforcement is provided.

[0037] Each reinforcing member 21 is a U-shaped member having bent portions 21a at both ends in the longitudinal direction (perpendicular to the bridge axis) that extend downward, and is arranged to straddle multiple first reinforcing bars 12 as shown in Figure 12. Each reinforcing member 21 is arranged perpendicular to the bridge axis and is provided in multiple rows spaced apart in the bridge axis direction. In this case, each reinforcing member 21 is positioned such that its bent portion 21a is located between the wide spacing A1 of the first reinforcing bars 12. Furthermore, the reinforcing members 21 in each row are positioned offset from each other in the direction perpendicular to the bridge axis.

[0038] According to this embodiment, similar to the first embodiment, a reinforcing member 21 that generates resistance between the reinforcing member 21 and the infill concrete 20 between each composite floor slab 10 is embedded in the infill concrete 20 so as to restrict the upward movement of the end side of the first reinforcing bar 12. Therefore, even if a bending moment occurs in the infill concrete 20, the upward movement of the end side of the first reinforcing bar 12 can be suppressed. As a result, the occurrence of cracks in the infill concrete 20 above the first reinforcing bar 12 can be effectively suppressed, and the durability of the joint of the composite floor slab can be improved.

[0039] Furthermore, since the main reinforcing bars embedded in the infill concrete 20 and the reinforcing members 21 can be used interchangeably, there is no need to separately provide reinforcing bars for the main reinforcing bars, thus improving the efficiency of the reinforcing bar placement work.

[0040] In the second embodiment described above, the bent portion 21a of the reinforcing member 21 was shown to extend only downward. However, as shown in the modified example of the bent portion 21b in Figure 13, it may also be formed in a roughly rectangular shape, bending downward and with its lower end bending horizontally (in a direction perpendicular to the first reinforcing bar 12). This allows for resistance between the reinforcing member 21b and the infill concrete 20 not only from the downward-extending portion of the bent portion 21b but also from the horizontally-extending portion, thereby more effectively restricting the upward movement of the end portion of the first reinforcing bar 12.

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

[0042] 10...Composite floor slab, 11...Bottom plate, 12...First reinforcing bar, 15...Concrete section, 15a...End face, 19...Reinforcement member, 19a,19b...Bent section, 20...Infill concrete, 21...Reinforcement member, 21a,21b...Bent section.

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 multiple 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 member is embedded in the aforementioned filler material and provides resistance between itself and the filler material so as to restrict the upward movement of the end of the reinforcing bar. Each of the aforementioned reinforcing bars is arranged such that wide and narrow sections are alternately placed in a horizontal direction perpendicular to the predetermined direction. The reinforcing member extends horizontally perpendicular to the reinforcing bar so that a portion of it is located above the reinforcing bar, and is bent downward so that both ends in the longitudinal direction are located below the reinforcing bar, and is formed to generate vertical resistance between itself and the filler material. The bent portion of the reinforcing member is positioned in the area where the reinforcing bars are spaced further apart. A composite floor slab joining structure characterized by the following features.

2. The reinforcing member is formed so that both ends in the longitudinal direction are bent downward and also bent horizontally perpendicular to the reinforcing bars. The composite floor slab joining structure according to feature 1.

3. The composite floor slab comprises a plurality of reinforcing bars arranged at intervals from each other in a horizontal direction perpendicular to the predetermined direction, The reinforcing member is placed in place of the reinforcing steel embedded in the aforementioned gap filler material, and the reinforcing member is formed from steel equivalent to that of the reinforcing steel. A composite floor slab joining structure according to claim 1 or 2.

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