JP2024040986A - Precast member and lifting structure of precast member - Google Patents

Abstract

To suppress the future deterioration of precast members.SOLUTION: A precast member (5) includes: a concrete body 14; and multiple insert members 15 buried in the concrete body 14 for locking during lifting. The insert member 15 is made of fiber-reinforced plastic and has a protruding part 15b that protrudes from an upper surface of the concrete body 15. Since the insert member 15 has the protruding part 15b, there is no need to provide a through hole or a box-out on an upper surface of the concrete body 14, and there is no need to provide post-fill materials on the upper surface of the concrete body 14. Therefore, occurrences of cracks and edge separation are suppressed.SELECTED DRAWING: Figure 3

Description

The present invention relates to a precast member and a structure for lifting the precast member.

There is a precast segment construction method as a construction method for manufacturing structures such as bridges. This construction method involves joining precast concrete blocks (segments) on site and integrating them by introducing prestress using tendons. The heavy precast segments are lifted using a crane and erected into position. As a structure for lifting precast segments of a box girder bridge, a structure is known in which a through hole is formed in the floor slab, and a fixed frame (lifting jig) is attached to a PC steel rod inserted through the through hole to lift the segment. (Figure 2 of Patent Document 1).

Furthermore, as shown in FIG. 5(A), the structure for lifting the precast member is such that an anchor material 52 is embedded in the member body 51, and a lifting jig 53 is attached to the anchor material 52 to lift the precast member. There is also. The anchor material 52 is provided in a box cutout 54 formed in the member body 51. After the precast member is lifted and erected at a predetermined position, the boxed part 54 is filled with a post-filling material 55 such as non-shrinkage mortar or expanded concrete and processed to be flat, as shown in FIG. 5(B). . A through hole as disclosed in Patent Document 1 is also treated with post-filling material 55 after the precast member is erected.

Japanese Patent Application Publication No. 11-80696

However, in conventional lifting structures, the back fill material is exposed on the top surface of the precast member. When the post-filling material deteriorates over time due to long-term use, there is a risk that the post-filling material may crack or the edge between the post-filling material and the precast member may break. Alternatively, when expanding concrete is used as a post-filling material, a sufficient expansion effect may not be obtained depending on the environmental conditions at the time of filling. In such a case, the edges between the post-filling material and the precast member are likely to be cut, and cracks are likely to occur. When cracks occur on the upper surface, the precast member deteriorates due to erosion due to water entering through the cracks, freezing of the water entering the cracks, and rusting of metal members such as reinforcing bars due to the water.

In view of the above background, it is an object of the present invention to suppress future deterioration of precast members.

In order to solve the above problems, an aspect of the present invention is a precast member (5) comprising a concrete body (14) and a plurality of insert members (14) buried in the concrete body for locking during lifting. 15), wherein the insert member is made of fiber-reinforced plastic and has a protrusion (15b) protruding from the upper surface of the concrete body.

According to this aspect, the precast member can be lifted by locking the hanging tool to the insert member. Since the insert member has a protruding portion, there is no need to provide a through hole or a boxed portion on the upper surface of the concrete body, and there is no need to provide a post-filling material on the upper surface of the concrete body. Therefore, the occurrence of cracks and edges on the upper surface of the concrete body is suppressed. Furthermore, since the insert member is made of fiber-reinforced plastic, there is no deterioration of the insert member due to rust. Therefore, deterioration of the precast member is suppressed.

In the above aspect, it is preferable that the insert member has a low shear resistance to the extent that it can be cut with a tool.

According to this aspect, after the precast member is hung by attaching a hanging tool to the precast member and moved to a predetermined position, the protruding portion that is no longer needed can be removed.

Moreover, in order to solve the above-mentioned problem, an aspect of the present invention is a suspension structure for the precast member (5) of the above-mentioned aspect, which includes a fixing tool (16) fixed to the protruding part of the insert member, and and a hanger (13) attached to the anchor.

Since the insert member is made of fiber-reinforced plastic, if the hanger is attached directly to the protrusion of the insert member, the protrusion may be damaged. According to this aspect, the fixing tool is fixed to the protruding part of the insert member, and the hanging tool is attached to the fixing tool, so that the hanging tool can be connected to the protruding part without damaging the protruding part.

In the above aspect, the lifting structure includes a pair of supports (17) arranged on the upper surface of the concrete body so as to sandwich the protrusion of the insert member, and a pair of supports (17) that connects the fixing device to the pair of supports. It is preferable to further include a fixing device (18) for fixing the device.

According to this aspect, since the protrusion is fixed to the pair of supports by the fixture, shearing force and bending moment are suppressed from acting on the protrusion. Therefore, damage to the protrusion is suppressed, and the precast member can be lifted safely.

In the above aspect, it is preferable that the fixing device fixes the fixing device to the pair of supports while applying tension to the protrusion.

According to this aspect, when the precast member is lifted using the hanging tool, it is possible to suppress loosening of fixation of the fixing tool to the support tool due to elongation of the protruding part due to the load of the precast member.

According to the above aspect, future deterioration of the precast member can be suppressed.

Side view showing the construction status of the girder bridge according to the embodiment Front view of the girder bridge seen from arrow II in Figure 1 Enlarged sectional view of section III in Figure 1 Enlarged cross-sectional view of the precast deck after cutting the insert member An explanatory diagram of a precast member lifting structure according to conventional technology

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, an example in which the invention is applied to a prestressed concrete deck slab 4 and a precast deck slab 5 of a girder bridge 1 will be described.

FIG. 1 is a side view showing the construction status of a girder bridge 1 according to an embodiment. As shown in FIG. 1, the girder bridge 1 includes a main girder 3 constructed between piers 2 spaced apart in the bridge axis direction, and a prestressed concrete deck slab 4 constructed on the main girder 3. has. The prestressed concrete deck slab 4 is constructed by connecting a plurality of precast deck slabs 5 arranged side by side in the bridge axis direction. These precast floor slabs 5 are connected to each other by introducing prestress using tendons 6. The tension material 6 is preferably made of aramid FRP, and may be made of fiber reinforced plastic other than aramid. Alternatively, the tension member 6 may be a PC steel rod or a PC steel strand. The precast floor slab 5 is lifted by a crane (not shown) via a lifting device 10 and placed at a predetermined position on the main girder 3.

FIG. 2 is a front view of the girder bridge 1 seen from arrow II in FIG. Since the precast deck slab 5 is long in the direction perpendicular to the bridge axis, two suspension devices 10 are arranged at positions separated from each other in the direction perpendicular to the bridge axis. Both suspension devices 10 have the same configuration. Both lifting devices 10 are connected to each other above by a main frame (not shown), and are lifted by one crane via the main frame. Each of the hanging devices 10 includes a rectangular frame 11, four hanging members 12 hanging from near the corners of the frame 11, and four hanging tools provided at the lower end of each hanging member 12 and attached to the precast floor slab 5. 13.

A pair of side surfaces 5a of the precast deck slab 5 facing the bridge axis direction are joint surfaces that are joined to the precast deck slabs 5 adjacently arranged on both sides of the bridge axis direction by tension members 6 that are tensioned by a post-tensioning method. be. A plurality of tendon insertion holes 7 are formed in the side surface 5a of the precast deck slab 5 facing the bridge axis direction. The tendon insertion hole 7 extends in the bridge axis direction and opens at a pair of side surfaces 5a of the precast deck slab 5. A shear key or keyway (not shown) may be formed on the side surface 5a of the precast floor slab 5.

FIG. 3 is an enlarged sectional view of section III in FIG. 1. As shown in FIG. 3, the precast floor slab 5 includes a concrete body 14 and an insert member 15 buried in the upper surface of the concrete body 14. The insert member 15 is a rod-shaped member made of fiber-reinforced plastic, and may be made of aramid FRP, for example. Alternatively, the insert member 15 may be made of plastic reinforced with non-metallic fibers such as carbon fibers and glass fibers. The insert member 15 has high tensile strength and is used to lock the lifting tool 13 to the precast floor slab 5 when lifting the precast floor slab 5.

The insert member 15 has a lower buried part 15a buried in the concrete body 14 of the precast slab 5, and a protrusion part 15b that projects upward from the upper surface of the concrete body 14. The insert member 15 preferably has a linear shape, and is directly fixed to the precast floor slab 5 by adhering concrete to the buried portion 15a.

A fixing tool 16 is attached to the protrusion 15b of the insert member 15. The fixing tool 16 is a metal cylindrical member having a male thread formed on its outer surface, and fixes the insert member 15 by injecting a fixing material with the protrusion 15b of the insert member 15 inserted therein. That is, the fixing device 16 is fixed to the insert member 15 in a non-removable manner. The fixing material may be an inorganic material such as non-shrinkage mortar, or an organic material such as an epoxy resin.

The hanging tool 13 is attached to the insert member 15 of the precast floor slab 5, more specifically, to the protrusion 15b, via the fixing tool 16, in order to lift the precast floor slab 5. The specific configuration is as follows. A male thread is formed at the lower end of the hanging member 12. The hanging tool 13 is a nut member having a female thread, and connects the hanging member 12 and the insert member 15 to each other by screwing into the male thread of the insert member 15 and the male thread of the hanging member 12.

As mentioned above, the insert member 15 has high tensile strength. On the other hand, the insert member 15 is weak against bending moment and shear force. Therefore, a pair of supports 17 are placed on the upper surface of the concrete body 14 so as to sandwich the protrusion 15b of the insert member 15, and the fixing tool 16 is fixed to the pair of supports 17 by a fixture 18. Specifically, the fixing tool 18 includes a nut that is screwed into the male thread of the fixing tool 16, and a plate member that loosely fits around the outer periphery of the fixing tool 16 and is disposed between the nut and the support tool 17 and engages with both. It is composed of. By rotating the nut, the fixture 18 is supported by the support 17 and pulls the fixture 16, thereby fixing the fixture 16. Thereby, the insert member 15 is fixed in a state where it receives only a tensile force.

When the precast floor slab 5 is lifted using the hanging tool 13, the protruding portion 15b of the insert member 15 expands due to the load of the precast floor slab 5, and the fixation of the fixing tool 16 to the support tool 17 becomes loose. Therefore, the fixing device 16 is fixed to the pair of supports 17 with the fixing device 18 applying a tension force greater than the load that the insert member 15 should support. Note that the load that the insert members 15 should support is approximately 1/8 of the weight of the precast floor slab 5 because eight insert members 15 are provided in this embodiment.

As described above, since the insert member 15 has the protruding part 15b that protrudes from the upper surface of the concrete body 14, the hanging tool 13 can be locked to the insert member 15 and the hanging device 10 can be used as shown in FIGS. The precast floor slab 5 can be lifted. After the precast floor slab 5 is placed in a predetermined position on the main girder 3 by the lifting device 10, the insert member 15 becomes unnecessary. Then, the insert member 15 is cut and removed using a tool. That is, the insert member 15 is configured to have a shear resistance low enough to be cut with a tool.

FIG. 4 is an enlarged sectional view of the precast floor slab 5 after the insert member 15 is cut. As shown in FIG. 4, the insert member 15 is preferably cut near the upper surface of the concrete body 14 of the precast slab 5. As a result, substantially the entire protrusion 15b of the insert member 15 is removed.

As described above, in this embodiment, the insert member 15 has the protruding portion 15b that protrudes from the upper surface of the concrete body 14. Therefore, there is no need to provide a through hole or a box cutout 34 (see FIG. 5) on the top surface of the concrete body 14, and there is no need to provide a post-fill material 36 (see FIG. 5) on the top surface of the concrete body 14. Therefore, the occurrence of cracks and edge breaks on the upper surface of the concrete body 14 is suppressed. Further, since the insert member 15 is made of fiber-reinforced plastic, there is no deterioration of the insert member 15 due to rust. Therefore, deterioration of the precast floor slab 5 is suppressed.

In addition, since the insert member 15 has a low shear resistance to the extent that it can be cut with a tool, the insert member 15 that is no longer needed can be protruded after the precast floor slab 5 is attached to the lifting tool 13 and lifted and moved to a predetermined position. Portion 15b can be removed.

Since the insert member 15 is made of fiber-reinforced plastic as described above, if the hanger 13 is directly attached to the protrusion 15b of the insert member 15, there is a risk that the protrusion 15b will be damaged. On the other hand, in the structure for lifting the precast floor slab 5 of this embodiment, as shown in FIG. 3, the fixing device 16 is fixed to the protruding portion 15b of the insert member 15, and the hanging device 13 is attached to the fixing device 16. Thereby, the hanging tool 13 can be connected to the protrusion 15b without damaging the protrusion 15b.

Further, a pair of supports 17 are arranged on the upper surface of the concrete body 14 so as to sandwich the protruding portion 15b of the insert member 15, and the fixing device 16 is fixed to the pair of supports 17 by a fixing device 18. This suppresses shear force and bending moment from acting on the protrusion 15b. Therefore, damage to the protruding portion 15b is suppressed, and the precast floor slab 5 can be lifted safely.

Here, the fixing tool 18 fixes the fixing tool 16 to the pair of supports 17 while applying tension to the protrusion 15b of the insert member 15. Thereby, when the precast floor slab 5 is lifted using the lifting tool 13, the fixation of the fixing tool 16 to the support tool 17 is suppressed from loosening due to the elongation of the protruding portion 15b due to the load of the precast floor slab 5.

This concludes the description of the specific embodiments, but the present invention is not limited to the above embodiments and modifications, and can be implemented in a wide range of modifications.

For example, the precast member according to the invention may be applied to a precast segment of a box girder bridge, and the lifting structure according to the invention may be applied to a suspension structure of a precast segment of a box girder bridge. Furthermore, the precast member according to the invention may be applied to a precast segment of a box culvert. Alternatively, the precast member according to the invention may be applied to a precast segment of an open-cut groove.

In addition, the specific structure, arrangement, quantity, material, construction procedure, etc. of each member or part can be changed as appropriate without departing from the spirit of the present invention. Furthermore, all of the constituent elements shown in the above embodiments are not necessarily essential, and can be selected as appropriate.

1: Girder bridge 2: Pier 3: Main girder 4: Prestressed concrete slab 5: Precast slab (precast member)
10 : Hanging device 11 : Frame 12 : Hanging member 13 : Hanging tool 14 : Concrete body 15 : Insert member 15a : Buried part 15b : Projecting part 16 : Fixing tool 17 : Supporting tool 18 : Fixing tool

Claims (5)

A precast member,
concrete body,
a plurality of insert members buried in the concrete body for locking during lifting;
A precast member, wherein the insert member is made of fiber-reinforced plastic and has a protrusion projecting from an upper surface of the concrete body. The precast member according to claim 1, wherein the insert member has a shear resistance low enough to be cut with a tool. The precast member lifting structure according to claim 1 or 2,
a fixing device fixed to the protrusion of the insert member;
and a lifting device attached to the fixing device. a pair of supports disposed on the upper surface of the concrete body so as to sandwich the protrusion of the insert member;
The lifting structure according to claim 3, further comprising a fixture that fixes the fixture to the pair of supports. 5. The lifting structure according to claim 4, wherein the fixing device fixes the fixing device to the pair of supports with tension applied to the protrusion.

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