JP2024037285A - Joint structure of composite floor slab - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a joint structure for synthetic deck slabs used, for example, in bridges such as general roads and expressways.

Conventionally, for example, composite deck slabs used for constructing bridges were constructed by fixing a steel bottom plate manufactured in a factory onto the main girder on site, placing reinforcing bars on the bottom plate, and pouring concrete. There is a known method for constructing a computer (see, for example, Patent Document 1). In construction using such synthetic floor slabs, concrete can be poured directly onto the bottom plate, so there is no need to use formwork, and on-site work can be made more efficient. However, the construction method of pouring concrete for the entire floor slab on site requires pouring concrete on site and a long curing period, so it has not been possible to sufficiently shorten the construction period.

Furthermore, a method is known in which the efficiency of on-site construction and the shortening of the construction period are improved by using a precast composite floor slab that is manufactured integrally with concrete in advance at a factory (see, for example, Patent Document 2). In this construction method, composite deck slabs are installed on the main girder, and filler concrete is placed between the end faces of adjacent composite deck slabs, ensuring the ability to transfer the load between the composite slabs. In order to do this, a plurality of reinforcing bars are extended from the end face of the composite deck slab into the filler part, and each reinforcing bar increases the bonding strength between the composite deck slab and the filler concrete.

Patent No. 4106317 JP2020-63617A

By the way, in the joint structure of the precast composite deck slab, a radially expanded anchoring portion is formed at the tip of the reinforcing bars extending from the end face of the concrete, and the anchoring portion reduces the bearing force in the tensile direction of the reinforcing bars against the filler concrete. I'm trying to increase that. However, when bending stress occurs in each composite slab and tensile force is applied to the reinforcing bars in the filler concrete, stress concentrates on the anchorage of the reinforcing bars, causing separation at the boundary between the concrete in the composite deck and the filler concrete. There was a risk that cracks would occur in the filler concrete starting from the anchorage of the reinforcing bars.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a synthetic floor slab that can suppress the occurrence of peeling and cracking at the interface between the concrete and filler of the synthetic floor slab. The purpose of this invention is to provide a joint structure for this purpose.

In order to achieve the above object, the present invention connects the ends of the bottom plate of a composite deck slab formed by placing reinforcing bars extending in a predetermined direction on a steel bottom plate and pouring concrete. A composite floor slab in which the composite floor slabs are joined in a predetermined direction by arranging the end side of the reinforcing bars between the concrete end faces of adjacent composite floor slabs and filling a filler between the concrete end faces. In the joint structure, the reinforcing bars arranged between the end faces of the concrete have a radially expanded anchoring part at the tip, and are formed so that the tip side is bent diagonally downward with respect to the predetermined direction. has been done.

As a result, the end side of the reinforcing bars placed between the concrete end faces of each composite slab is formed so that the tip side is bent diagonally downward with respect to the bridge axis direction, so that the filler The anchoring portion is located on the center side in the vertical direction where the tensile stress is lower than that on the upper surface side, and the occurrence of peeling and cracking at the interface between the concrete and the filler material of the synthetic deck slab due to stress concentration on the anchoring portion is suppressed.

According to the present invention, it is possible to suppress the occurrence of peeling and cracking at the interface between the concrete and the filler of the synthetic deck, and therefore it is possible to improve the durability of the joint of the synthetic deck.

A plan view of a synthetic floor slab showing the first embodiment of the present invention Plan of main parts of composite slab Side cross-sectional view of main parts of composite deck slab Side cross-sectional view showing the joining process of synthetic floor slabs Side cross-sectional view showing the joining process of synthetic floor slabs Side cross-sectional view showing the joining process of synthetic floor slabs Side cross-sectional view showing the joining process of synthetic floor slabs Side cross-sectional view showing the bonded state of composite deck slabs Schematic side cross-sectional view showing the joints of composite deck slabs Schematic side sectional view showing a comparative example of joints of synthetic floor slabs A side sectional view of a joint part of a synthetic floor slab showing a second embodiment of the present invention A side sectional view of a joint part of a synthetic floor slab showing a third embodiment of the present invention

1 to 9 show a first embodiment of the present invention, and show a composite deck slab used for bridges such as general roads and expressways, for example.

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

The composite deck 10 includes a steel bottom plate 11 forming the bottom surface of the deck body, a plurality of first reinforcing bars 12 as distribution bars extending in the bridge axis direction, and a plurality of main reinforcing bars extending in the direction perpendicular to the bridge axis. , a plurality of stiffeners 14 fixed on the bottom plate 11 , and a concrete section 15 cast on the bottom plate 11 . 11 and are connected by bolts 16 and attachment plates 17.

The bottom plate 11 is made of a flat steel plate, and a plurality of bolt insertion holes 11a through which bolts 16 are inserted are provided at both ends in the bridge axis direction. The bolt insertion holes 11a are arranged at intervals from each other in the direction perpendicular to the bridge axis, and are provided so as to penetrate the bottom plate 11 in the thickness direction. Furthermore, a plurality of studs 11b are provided on the bottom plate 11 to be buried in the concrete portion 15 or in the filler concrete 19 described later.

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 to the outside of the concrete part 15. An anchoring section 12a is provided at the end of each first reinforcing bar 12 for anchoring it to filler concrete, which will be described later, and the anchoring section 12a is formed to expand in the radial direction of the first reinforcing bar 12. . Further, the tip side of each first reinforcing bar 12 is formed to be bent diagonally downward with respect to the bridge axis direction. As shown in FIG. 2, each of the first reinforcing bars 12 is arranged alternately with each of the first reinforcing bars 12 of other adjacent composite deck slabs 10 in the direction perpendicular to the bridge axis. In this case, each of the first reinforcing bars 12 is such that the first reinforcing bars 12 of one composite deck slab 10 and the first reinforcing bars 12 of the other composite deck slab 10 are separated from each other by a wide interval A1 and a narrow interval A2. The bolts 16 are arranged so as to be located below a wide distance A1.

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.

Each of the stiffeners 14 is made of a steel material (for example, channel steel) that extends in the direction perpendicular to the bridge axis, and is arranged at intervals from each other in the bridge axis direction.

The concrete portion 15 is poured onto the bottom plate 11 using a formwork in a factory or the like, and forms a slab portion extending over the entire width of the bottom plate 11 on the bottom plate 11. A first reinforcing bar 12, a second reinforcing bar 13, a stiffener 14, and a stud 11b are buried in the concrete part 15, and the end side of the bottom plate 11 and the end side of the first reinforcing bar 12 are buried in the concrete part 15. It extends horizontally outward from the end surface 15a. In this case, each first reinforcing bar 12 is arranged above the vertical center of the concrete portion 15. Further, the concrete portion 15 is provided with a plurality of holes 15b through which the anti-slip members of the main girder 20 are inserted.

The bolts 16 are made of high-strength bolts, and are temporarily fixed to the bottom plate 11 before the synthetic floor slab 10 is transported to the construction site. At this time, the bolts 16 are inserted into the bolt insertion holes 11a of the bottom plate 11 from below as shown in FIG. 3, and are temporarily fixed to the bottom plate 11 by screwing the temporary fixing nuts 16a from above the bottom plate 11. . For example, a ring-shaped member made of synthetic resin and having a thickness smaller than that of the attachment plate 17 is used as the temporary fixing nut 16a.

The attachment plate 17 is made of a steel plate extending in the direction perpendicular to the bridge axis, and is formed so as to be placed on the upper surface of the end side of each bottom plate 11 across the bottom plates 11 of the mutually adjacent synthetic deck slabs 10. The attachment plate 17 is provided with a plurality of bolt insertion holes 17a through which the bolts 16 are inserted, and the bolt insertion holes 17a are formed to have an inner diameter larger than the outer diameter of the temporary fixing nut 16a.

The composite floor slab 10 configured as described above is manufactured in a factory or the like and then transported to a construction site. At this time, high-strength bolts 16 are temporarily fixed to the bottom plate 11 of the composite floor slab 10 in advance.

Hereinafter, the joining process of the composite deck 10 will be explained with reference to FIGS. 4 to 8.

First, the composite deck slab 10 delivered to the site is positioned on one side in the bridge axis direction as shown in FIG. It is installed on the main girder 20 so that At this time, the bottom plates 11 of the composite deck slabs 10 are butted against each other in the bridge axis direction with a slight interval between them, and a fill area is formed between the concrete parts 15 of each composite deck slab 10. Furthermore, a slip prevention member (not shown) for the main girder 20 is disposed within the hole 15b of the concrete portion 15.

Next, as shown in FIG. 6, a splicing plate 17 is placed on the upper surface of the end of the bottom plate 11 of each composite floor slab 10, and nuts 16b are screwed onto the bolts 16 temporarily fixed to the bottom plate 11 in advance. Tighten. At this time, since the temporary fixing nut 16a is arranged in the bolt insertion hole 17a of the attachment plate 17, the temporary fixing nut 16a does not interfere with the nut 16b.

Here, in the composite floor slabs 10 that are adjacent to each other, the bolts 16 are located below the wide interval A1 between each of the first reinforcing bars 12 as shown in FIG. The nut 16b is fully tightened to the bolt 16 using a tightening tool 30 (for example, a shear wrench with a long socket) that can be inserted through a wide distance A1 from above the reinforcing bar 12.

After this, as shown in FIG. 8, a plurality of reinforcing bars 18 extending in the direction perpendicular to the bridge axis are placed on the first reinforcing bars 12 located in the filling area between each concrete part 15 at intervals in the bridge axis direction. Filling concrete 19 is placed as a filling material in the filling area between each concrete portion 15. For example, quick hardening concrete is used as the filler concrete 19. As a result, each of the first reinforcing bars 12 in the filling area is integrated with the filling concrete 19, and adhesive force and bearing force (horizontal shear force) generated between each of the first reinforcing bars 12 and the filling concrete 19 are The strength of the bond between the composite floor slabs 10 is increased by the resisting force). At this time, since the adhesion force and bearing force are further increased by the anchoring portion 12a provided at the end of each first reinforcing bar 12, as shown in FIG. The length L of the overlapping portion in the bridge axis direction can be made shorter than when reinforcing bars without the fixing portion 12a are used.

Further, by filling the holes 15b of the concrete part 15 with non-shrinkage mortar, the anti-slip member (not shown) of the main girder 20 and the concrete part 15 are integrated.

Here, as shown in FIG. 9, when a load F is applied to each composite slab 10 and bending stress is generated in the filler concrete 19, a tensile force P is applied to the first reinforcing bars 12 in the filler concrete 19. . At this time, the tip side of the first reinforcing bar 12 is bent diagonally downward with respect to the bridge axis direction, so the tip side of the first reinforcing bar 12 is not bent as shown in the comparative example in FIG. The height distance D from the anchoring portion 12a at the tip to the upper surface of the filler concrete 19 is longer than in the case. As a result, the anchoring portion 12a is located on the center side in the vertical direction where the tensile stress is smaller than the upper surface side of the filler concrete 19, so that the end surface 15a of the concrete portion 15 of the composite deck slab 10 due to stress concentration on the anchoring portion 12a. Peeling of the interface with the filler concrete 19 (particularly the upper portion of the first reinforcing bars 12) and generation of cracks starting from the anchoring portion 12a are suppressed. In this case, it is preferable to ensure a horizontal distance C of, for example, about 10 mm to 60 mm between the boundary part and the fixing part 12a in order to prevent peeling.

As described above, according to the present embodiment, the first reinforcing bars 12 that extend from the end surface 15a of the concrete portion 15 of each composite deck slab 10 and are buried in the filler concrete 19 between the concrete portions 15 are located at the tip portions. It has an anchoring part 12a with an enlarged diameter, and is formed so that the tip side is bent diagonally downward with respect to the bridge axis direction, so that the center part in the vertical direction has a lower tensile stress than the upper surface side of the filler concrete 19. The anchoring portion 12a can be positioned on the side, and it is possible to suppress the occurrence of peeling or cracking at the interface between the concrete portion 15 and the filler concrete 19 due to stress concentration on the anchoring portion 12a. The durability of the joint can be improved.

In the above embodiment, the first reinforcing bars 12 of one synthetic deck 10 and the first reinforcing bars 12 of the other synthetic deck 10 are arranged so that every other reinforcing bar 12 has a wide interval and a narrow interval. However, the first reinforcing bars 12 of each composite floor slab 10 may be arranged at equal intervals.

Furthermore, in the embodiment described above, the composite deck slabs 10 are joined in the direction of the bridge axis, but the present invention can also be applied to a case where the composite deck slabs 10 are joined in the direction perpendicular to the bridge axis.

FIG. 11 shows a second embodiment of the present invention, in which the same components as in the first embodiment are denoted by the same reference numerals.

In this embodiment, the end surface 15c of the concrete portion 15 of each composite floor slab 10 is formed to have an uneven shape. As a result, the boundary surface between the concrete portion 15 and the filler concrete 19 filled between the end surfaces 15c of the concrete portion 15 becomes uneven, and the adhesion of the boundary surface is increased.

According to this embodiment, it is possible to increase the adhesive force at the interface between the concrete portion 15 and the filler concrete 19, so that stress concentration on the anchoring portion 12a causes the concrete portion 15 and the filler concrete 19 of the composite floor slab 10 to It is possible to suppress peeling of the interface with the first reinforcing bar 12 (particularly the upper part of the first reinforcing bar 12) and the occurrence of cracks starting from the anchoring part 12a, and it is possible to improve the durability of the joint part of the synthetic floor slab 10. can.

In the second embodiment, the entire end face of the concrete portion 15 is formed in an uneven shape, but only the upper part of the first reinforcing bar 12 on the end face of the concrete 15 is formed in an uneven shape. You can also do this.

FIG. 12 shows a third embodiment of the present invention, in which the same components as those in the first embodiment are denoted by the same reference numerals.

In this embodiment, the adhesive 15d is applied to the end face of the concrete portion 15 of each synthetic floor slab 10. As a result, the filling concrete 19 filled between the end faces of the concrete part 15 is adhered to the end face of the concrete part 15 by the adhesive 15d, and the adhesion force at the interface between the concrete part 15 and the filling concrete 19 is increased.

According to this embodiment, it is possible to increase the adhesive force at the interface between the concrete portion 15 and the filler concrete 19, so that stress concentration on the anchoring portion 12a causes the concrete portion 15 and the filler concrete 19 of the composite floor slab 10 to It is possible to suppress peeling of the interface with the first reinforcing bar 12 (particularly the upper part of the first reinforcing bar 12) and the occurrence of cracks starting from the anchoring part 12a, and it is possible to improve the durability of the joint part of the synthetic floor slab 10. can.

In the second embodiment, the adhesive 15d is applied to the entire end face of the concrete portion 15, but the adhesive is only applied to the upper part of the first reinforcing bar 12 on the end face of the concrete 15. You may also apply it.

Furthermore, in the second and third embodiments, similarly to the first embodiment, the tip side of the first reinforcing bar 12 is bent diagonally downward with respect to the bridge axis direction. Although shown, at least one of the second and third embodiments can be applied to the first reinforcing bar 12 whose distal end side is not bent.

Note that each of the above embodiments is an example of the present invention, and the present invention is not limited to what is described in the above embodiments.

DESCRIPTION OF SYMBOLS 10... Synthetic floor slab, 11... Bottom plate, 12... First reinforcing bar, 12a... Anchoring part, 15... Concrete part, 15a, 15c... End surface, 15d... Adhesive, 19... Filling concrete.

Claims (3)

Connecting the ends of the bottom plates of synthetic deck slabs, which are formed by placing reinforcing bars extending in a predetermined direction on a steel bottom plate and pouring concrete, as well as connecting the ends of the concrete of adjacent composite deck slabs. In a composite deck joining structure in which composite deck slabs are joined in a predetermined direction by arranging the end side of the reinforcing steel and filling a filler between the end faces of the concrete,
The reinforcing bars placed between the end faces of the concrete have a radially expanded anchoring part at the tip, and are formed so that the tip side is bent obliquely downward with respect to the predetermined direction. A characteristic joint structure of synthetic floor slabs. The composite deck joining structure according to claim 1, wherein at least an upper portion of the reinforcing bars on the end face of the concrete is formed to have an uneven shape. The joining structure of a synthetic deck slab according to claim 1 or 2, wherein at least an upper portion of the reinforcing bar and the filler material on the end face of the concrete are bonded with an adhesive.

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