KR101118029B1 - Fiber Reinforced Composite Tubular Unit and Bridge Deck Assembled with Tubular Unit - Google Patents

Abstract

The present invention is a FRP tube having a polygonal hollow cross-section and fabricated in a precast method of fiber-reinforced composite material and connected in parallel by a mechanical coupling of a snap-fit type to form a bottom plate, and a bottom plate made by the tube. It is about.
In the present invention, the upper plate (2), the lower plate (3) and the abdominal plate (4) is composed of a plurality of polygonal hollow cross-section FRP tube 10, one side of the FRP tube 10, the first downward protrusion coupling portion 150a, the second downward protrusion coupling part 150b, the upper extension part 51, and the upper extension part 61 are formed; On the other side of the FRP tube 10, the first upward protrusion coupling portion 151a and the second upward coupling which are detachably coupled to the first and second downward protrusion coupling portions 150a and 150b in the form of snap-fits, respectively. The protrusion coupling part 151b is formed, and the lower extension part 52 and the lower extension part 62 are formed, and the lower end face reduction part 72 is concave on the bottom surface of the lower plate 3 from one side of the FRP tube 10. ), A concave upper cross-sectional reduction portion 71 is formed on the upper surface of the upper plate 2, and protrusions 150c and 151c are formed on the protrusion coupling portions 150a, 151a, 150b, and 151b. The fiber-reinforced composite precast FRP tube is characterized in that the bottom plate is coupled to the neighboring FRP tube (20, 30) by a snap-fit mechanical detachment in a vertical direction. In addition, the present invention provides a bottom plate manufactured using the FRP tube.

Description

Fiber Reinforced Composite Tubular Unit and Bridge Deck Assembled with Tubular Unit}

The present invention relates to a composite tube of a hollow cross section and a composite bottom plate using the same, and specifically, a hollow hollow cross section of a polygon using fiber reinforced plastic (hereinafter referred to as "FRP"). It has a snap-fit coupling structure that is manufactured at the factory to have a tube and is fitted into a neighboring tube in a vertical direction, and has an extension part which is laterally extended toward the neighboring tube and joined using an adhesive such as epoxy. The present invention relates to a novel FRP tube having a high resistance to breakage at a connection portion coupled to a tube, and a bottom plate assembled by this.

FRP tubes having a shape extending in the longitudinal direction to have a polygonal hollow section are known through Design Registration No. 30-312946, analog No. 2 (Application No. 30-2003-3540), which are known in the transverse direction. By inserting in the transverse direction to the side of the neighboring FRP tube to make the bottom plate of the bridge or building structure, the wall, the wall of the box culvert, etc. (in this specification, the term "floor plate" is the bottom plate of the bridge) In addition, it is to be understood as including the bottom plate, wall, box culvert wall, etc. of such a building structure). 1 is a schematic perspective view of a conventional FRP tube.

By the way, in the case of a conventional FRP tube as shown in Figure 1, there is an inconvenience in the construction of the bridge bottom plate installed on the girder. In the case of the conventional FRP tube as shown in Figure 1, in order to assemble the neighboring FRP tube in the transverse direction, the side of the neighboring FRP tube by horizontally pushing the FRP tube on one side toward the other FRP tube horizontally It will be assembled to. On the other hand, in the installation of the bottom plate on the girder for shear synthesis of the girder and the bottom plate should be provided with a shear connecting material such as a stud on the girder. However, it is impossible to push the FRP tube horizontally horizontally as described above in the state that the shear connector such as the stud is provided on the girder, so the shear connector is inevitably only after the bottom plate installation by the assembly of the FRP tube is completed. It can only be installed in. However, assembling the shear connector after the installation of the bottom plate requires work in a poor site, which increases the time required for the shear connector installation and increases the cost, and it is difficult to visually check the shear connector installation status, and in the case of concrete girder, the shear connector Various problems arise, such as making the installation extremely difficult.

The present invention was developed for the purpose of solving the limitations and problems of the conventional FRP tube and the bottom plate constructed by using the same, pre-fabricated by using the FRP pre-fabrication, horizontal when assembling the FRP tube It aims to be able to assemble in the vertical direction rather than the direction, and to improve the structural integrity between the FRP tube by greatly increasing the bonding strength at the connection between the neighboring FRP tube in the lateral direction.

In order to achieve the above object, in the present invention, the upper plate, the lower plate and the abdominal plate is composed of a plurality of polygonal hollow cross-section FRP tube, one side of the FRP tube, the first downward protrusion coupling portion and the second downward protrusion coupling portion The first downward protrusion coupling portion is formed downward in the middle of the upper extension portion in which the upper plate is further extended to the side surface, and further exists in the transverse side from the position where the first downward protrusion coupling portion is formed. An upper extension portion forms an upper extension portion, and the second downward protrusion coupling portion is formed to protrude downwardly on an outer side surface of the outer abdominal plate; The other side of the FRP tube is formed with a first upward protrusion coupling portion and a second upward protrusion coupling portion which is mechanically coupled in a snap-fit form so as to be detachable from the first and second downward protrusion coupling portions, respectively. The upward protrusion coupling portion protrudes upward from the outer side of the outer abdominal plate, and the second upward protrusion coupling portion is provided upward in the middle of the lower extension portion in which the lower plate is further extended outward, and the second upward protrusion coupling portion is formed. The lower extension further present from the position to the transverse side constitutes the lower extension; On the bottom surface of the lower plate from one side of the FRP tube in which the second downward protrusion coupling portion is formed so that the lower extension provided on the other side of the front neighboring FRP tube can be covered and joined by an adhesive, a recess corresponding to the thickness of the lower extension is formed. A lower cross-sectional reduction portion of the shape is formed; On the upper surface of the upper plate from the other side of the FRP tube in which the first upward protrusion coupling part is formed so that the upper extension provided on one side of the rear neighboring FRP tube can be covered and joined by an adhesive, the upper extension corresponds to the thickness of the upper extension. An upper cross-sectional reduction portion of a concave shape is formed; The protrusion coupling portion is formed with protrusions corresponding to each other so as to form a mechanical coupling to each other, it is coupled by the mechanical detachment method of the snap-fit type in a direction perpendicular to the neighboring FRP tube to form a bottom plate Characterized by the FRP tube is provided.

In addition, in the present invention, as the bottom plate formed by combining the above FRP tube in the transverse direction, the FRP tube is inserted in the vertical direction, the snap-fit type mechanical coupling method between the up and down projection coupling portion, A bottom plate made of an assembly of an FRP tube, characterized in that it is integrally coupled to each other by the bonding between the upper extension and the upper cross-sectional reduction and the lower expansion and the lower cross-sectional reduction. This is provided.

According to the invention, the bottom plate can be constructed by interconnecting the FRP tubes, which is particularly useful for fabricating the bottom plate of the bridge.

In the present invention, since the FRP tube made of fiber-reinforced composite material having corrosion resistance and high durability is used, the problems of durability and structural safety, such as concrete deterioration and reinforcement corrosion of reinforced concrete, which are conventional floorboard materials, are fundamentally solved. As a result, the service life of the bridge deck can be extended 2-3 times longer than the conventional reinforced concrete deck method. In addition, due to the high durability, the maintenance cost can be minimized during public use, so when considering the life cycle cost of the entire bridge can be expected to significantly reduce the maintenance cost compared to the conventional reinforced concrete deck.

According to the present invention, in the case of improving the performance of the existing concrete deck plate bridge, the existing reinforced concrete deck is to be demolished and installed in the factory assembled precast FRP tube on site, in this case the dead weight of the concrete deck is lightweight composite material It can be replaced by the dead weight of the bottom plate to reduce the dead weight of the upper structure by more than 80%, and it can pass the vehicle load that is larger than the reduction of the dead weight. This facilitates the construction, and can be economically constructed by lightening the girder and the substructure even when the bridge is newly constructed.

In particular, the present invention exhibits the following excellent effects as compared to the conventional structure of the FRP tube.

In the present invention, since the FRP tube is mounted by pressing from above, the shear connector may be pre-installed on the upper surface of the girder, and as in the conventional case, the shear connector does not need to be welded and assembled later through a narrow space, thereby Installation is easy and saves time and effort. In addition, there is an advantage that easy verification and quality control of the welding state of the shear connector. Furthermore, according to the present invention, in the case of a concrete girder, it is possible to manufacture a concrete girder in a state in which the rebar for shear connector is arranged in advance.

In the present invention, since the FRP tube can be assembled in the vertical direction, each FRP tube can be transported to the site without assembling the bottom plate panel in the factory, and the bottom plate can be assembled in the field. Therefore, as compared with the conventional case of having to transfer the large and heavy bottom panel panel, the transfer operation is easy, it is possible to reduce the cost of the transfer. In particular, while installing each FRP tube, it is easy to adjust the gap between the lower part of the tube and the upper surface of the girder, and to check the filler injection quality between the gaps.

In the present invention, when the connection between the FPR tube and the mechanical bonding for the vertical assembly at the same time to perform the mechanical bonding using an adhesive such as epoxy for structural integration at the same time, specifically the FRP by the extension of the front neighboring FRP tube A portion of the outer surface of the tube is covered, but the extension and the outer surface of the FRP tube are integrally joined to each other by an adhesive. Therefore, the tensile force acting on the joints between the FRP tubes by bending, thermal contraction and expansion, and the tensile force due to the elastic deformation of the pavement caused by the wheel load repeatedly acting on the pavement placed on the top of the FRP bottom plate. Since the resistance due to the adhesive force between the expansion portion integrally bonded by the adhesive and the outer surface of the FRP tube is generated, the down-projection coupling portion and the vertical downward and horizontal load applied to the FRP tube adjacently coupled to each other and The tensile force acting to open between the upward protrusion coupling portions is reduced, thereby preventing the occurrence of breakage such as breakage of the adhesive portion and breakage of the downward protrusion coupling portion.

1 is a schematic perspective view of a conventional FRP tube.
2 and 3 are a schematic perspective view and a cross-sectional view showing a state of manufacturing the bottom plate by assembling the FRP tube according to the present invention, respectively.
Figure 4 is a schematic cross-sectional view of the bottom plate made by the assembly of the FRP tube.
Figure 5 is an enlarged view of the circle A portion of Figure 4, an enlarged view of the coupling form of the protrusion coupling portion provided in the FRP tube of the present invention.
6 is a schematic cross-sectional view showing a form of exhibiting resistance when the vertical load is applied in the state in which the FRP tube of the present invention is coupled.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Although the present invention has been described with reference to the embodiments shown in the drawings, this is described as one embodiment, whereby the technical spirit of the present invention and its core configuration and operation are not limited.

2, 3, 4 and 5 are respectively a schematic perspective view and a cross-sectional view showing a state of manufacturing the bottom plate by assembling the FRP tube according to the present invention, and a cross-sectional view of the bottom plate and the protrusion coupling portion provided in the FRP tube An enlarged view of the combined form is shown.

As shown in the figure, the FRP tube 10 of the present invention is composed of a top plate 2, a bottom plate 3 and the abdominal plate 4 has a plurality of polygonal hollow 50, the configuration extending in the longitudinal direction Has As shown in the figure, the hollow 50 may be provided in two pieces, or three or more pieces thereof. In the embodiment shown in the figure, the hollow 50 is to have a trapezoidal shape, the hollow 50 is not a single trapezoidal shape may have a variety of shapes. The FRP, which is a material of the tube according to the present invention, is composed of a resin selected from polyester, vinyl ester, panol, or epoxy, and reinforcing fibers (glass fiber, carbon fiber, aramid fiber, etc.), and the FRP tube is a pultrusion molding method. Is made by.

The bottom plate is constructed by combining the FRP tube 10 having the cross-sectional configuration as described above with a neighboring FRP tube in the lateral side. The FRP tube 10 according to the invention approaches in a vertical direction (from top to bottom) with respect to the FRP tube 20 (hereinafter abbreviated as the front neighboring FRP tube 20) which has been previously installed so as to laterally neighbor. And the front neighboring FRP tube 20 is coupled in a simple yet robust mechanical detachable manner in the form of a snap-fit. To this end, a first downward protrusion coupling part 150a and a second downward protrusion coupling part 150b are formed at one side of the FRP tube 10, and the first and second downward protrusion coupling parts 150a and 150b are formed. Each of the first upward protrusion coupling part 151a and the second upward protrusion coupling part 151b which are mechanically coupled in a snap-fit form to be detachable from each other are formed at the other side of the FRP tube 10.

Specifically, in the embodiment shown in the figure, one side surface of the FRP tube 10 is formed with an upper extension portion 51 in which the upper plate 2 further extends in the lateral side, the upper extension portion The first downward protrusion coupling portion 150a is formed in the middle of the 51 in the downward direction. In this way, the upper extension portion further present in the transverse side from the position where the first downward protrusion coupling portion 150a is formed corresponds to the upper extension portion 61. The upper extension 61 is fitted to the upper cross-sectional reduction portion 71 formed on a part of the other upper plate 2 of the front neighboring FRP tube 20, so that the upper extension 61 is the front neighboring FRP tube. (20) A part of the other side upper plate 2 is covered.

Meanwhile, one side of the FRP tube 10 in which the second downward protrusion coupling part 150b is formed so that the lower extension part 62 provided on the other side of the front neighboring FRP tube 20 is fitted and covered. From the bottom surface of the lower plate 3, a lower cross-sectional reduction portion 72 of a concave shape corresponding to the thickness of the lower expansion portion 62 is formed. At one side of the FRP tube 10 in the transverse direction, the second downward protrusion coupling part 150b protrudes downward from the outer side of the outer abdominal plate 4.

On the other side of the FRP tube 10 in the lateral direction, the first upward protrusion coupling portion 151a which is fastened to the first downward protrusion coupling portion 150a is provided to protrude upward from the outer side of the outer abdominal plate 4. The lower extension part 52 in which the lower plate 3 extends is formed in the lower part, and the second upward protrusion which is engaged with the second downward protrusion coupling part 150b in the middle of the lower extension part 52. Coupling portion 151b is provided upward. As such, the lower extension part further present in the transverse side from the position where the second upward protrusion coupling part 151b is formed corresponds to the lower extension part 62. The lower extension part 62 is a lower cross-sectional reduction part formed on a portion of the bottom surface of one lower plate 3 of the FRP tube (hereinafter, abbreviated as rear neighboring FRP tube 30) (see FIG. 4). 72, the lower extension 62 covers a portion of the bottom surface of the lower plate 3 of the rear neighboring FRP tube 30 in one direction.

On the other hand, the upper extension portion 61 of the rear neighboring FRP tube 30 is fitted to the upper surface of the upper plate 2 from the other side of the FRP tube 10 in which the first upward protrusion coupling portion 151a is formed. In order to be covered, a concave upper cross-sectional reduction portion 71 corresponding to the thickness of the upper extension 61 is formed.

5 is an enlarged view of an embodiment in which the first downward protrusion coupling unit 150a and the first upward protrusion coupling unit 151a are coupled to each other, and the first downward protrusion coupling unit 150a and the first upward protrusion are combined with each other. The protrusion coupling portions 151a are formed with protrusions 151c and 152c of corresponding shapes, respectively, so that the protrusions 150c and 151c bite each other to form a strong mechanical coupling. Shown in dashed lines in FIG. 5 shows a fiber arrangement in the protrusion coupling parts 150a and 151a. As shown in the drawing, the first downward protrusion coupling part 150a and the first upward protrusion coupling part 151a protrude from the abdominal plate 4 but have a structure in which protrusions are formed parallel to the abdominal plate 4. Dotted lines in FIG. 5 represent the arrangement of the fibers.

In the present invention, the FRP tube 10 is fitted side by side in the lateral side of the front neighboring FRP tube 20 of the same shape to form a plate structure, that is, a bottom plate. Specifically, as shown in FIG. 3, on the other side of the front neighboring FRP tube 20 in the transverse direction, the FRP tube 10 is placed vertically from above and pressurized to join the front neighboring FRP tube 20, which is the front neighbor. The first upward protrusion coupling portion 151a of the FRP tube 20 is fitted with the first downward protrusion coupling portion 150a of the FRP tube 10 which is positioned downward from the top. At the same time, the second upward protrusion coupling part 151b of the front neighboring FRP tube 20 is fitted with the second downward protrusion coupling part 150b of the FRP tube 10. In this way both FRP tubes 10, 20 are firmly joined by mechanical engagement.

In this case, since the first upward protrusion coupling part 151a and the second downward protrusion coupling part 150b have a predetermined elasticity, when the FRP tube 10 is pressed with a force of a predetermined level or more, the protrusions 150c, As the slip occurs between 151c, the first upward protrusion coupling portion 151a and the second downward protrusion coupling portion 150b are finely retracted to facilitate mechanical coupling of the protrusion period. After the protrusions 150c and 151c are slipped from each other, the first upward protrusion coupling part 151a and the second downward protrusion coupling part 150b are returned to each other by elasticity, so that the protrusions 150c and 151c are firmly connected to each other. Will be passed down.

As described above, the first downward protrusion coupling part 150a is fitted to the first upward protrusion coupling part 151a, and the second downward protrusion coupling part 150b is fitted to the second upward protrusion coupling part 151b so that both FRP tubes ( When the 10 and 20 are to be coupled, the upper extension 61 of the FRP tube 10 is connected to the upper cross-sectional reduction portion 71 formed in a part of the other upper plate 2 of the front neighboring FRP tube 20. In this way, the upper extension 61 covers a portion of the front neighboring top plate 2 of the front neighboring FRP tube 20, ie the upper cross-sectional reduction portion 71. In addition, the lower cross-sectional reduction portion 72 formed on the bottom surface of the lower plate 3 from one side of the FRP tube 10 is placed on the lower expansion portion 62 formed on the other side of the front neighboring FRP tube 20, A portion of the bottom surface of the lower plate 3 of the FRP tube 10, that is, the lower cross-sectional reduction portion 72, is covered by the lower extension 62 of the front neighboring FRP tube 20.

As such, the upper extension 61 covers the upper end face reduction portion 71 of the front neighboring FRP tube 20, and the lower end face reduction portion 72 is formed on the other side of the front neighboring FRP tube 20. When covered by the lower extension 62, between the bottom surface of the upper extension 61 and the upper surface of the upper cross-sectional reduction portion 71, and between the upper surface of the lower extension 62 and the lower cross-sectional reduction portion 72. An adhesive such as epoxy is applied to and integrally bonded to each other.

6, the upper extension 61 of the FRP tube 10 covers the upper end face reduction portion 71 on the other side of the front neighboring FRP tube 20 and is integrally joined by an adhesive, and the front neighboring FRP tube ( Example showing that the lower end face reduction portion 72 of the FRP tube 10 is covered by the lower extension portion 62 of the FRP tube 10 so as to be integrally bonded by an adhesive, thereby exhibiting excellent resistance when the stress is applied in the transverse direction. As a schematic cross-sectional view of a state in which the vertical load is applied at the top. As shown in FIG. 6, when a vertical downward load is applied to the FRP tubes 10 and 20 which are adjacently coupled to each other, the bending tensile force acts at the position of the lower plate 3. This bending tensile force acts to spread between the second downward protrusion coupling portion 150b and the second upward protrusion coupling portion 151b which are coupled to each other, to the lower extension 62 of the front neighboring FRP tube 20. As a result, a portion of the bottom surface of the lower plate 3 of the FRP tube 10 is covered and integrally bonded with an adhesive, thereby generating a large resistance to the bending tensile force, so as to bear a part of the bending tensile force generated at the lower plate 3 position. Therefore, the tensile force acting so that the gap between the second downward protrusion coupling portion 150b and the second upward protrusion coupling portion 151b is reduced, and thus the second downward protrusion coupling portion 150b is broken. This is prevented from occurring.

When a vertical upward load is applied, the bending tension is applied at the position of the upper plate 2 so that the gap between the first downward protrusion coupling part 150a and the first upward protrusion coupling part 151a is widened. Since the upper extension 61 of the FRP tube 10 covers a part of the upper side plate 2 on the other side of the front neighboring FRP tube 20 and is integrally joined by an adhesive, thereby causing a large resistance to bending tensile force. As a result, a portion of the bending tensile force occurring at the position of the upper plate 2 is borne, so that the tensile force acting to spread between the first downward protrusion coupling part 150a and the first upward protrusion coupling part 151a is reduced. The first upward protrusion coupling part 151a may be prevented from being broken.

In FIG. 6 above, the vertical load acting on the upper protrusion coupling part and the downward protrusion coupling part are caused to be caused by the tension, so that the vertical load as shown in the figure, as well as the temperature load or the expansion or the wheel, are illustrated. The above tensile force may also be affected by other factors, such as pavement elastic deformation due to load.

As described above, in the present invention, by ensuring a sufficient bonding area between the neighboring FRP tube in the upper and lower surface to achieve the adhesive bond of the adhesive, while maintaining a vertical coupling method to exhibit a great resistance to the tensile force that can occur between the FRP tube This makes it possible to prevent breakage at the connecting portion of the FRP tube. Therefore, the FRP bottom plate according to the present invention produced by the bonding of such FRP tube has excellent durability and strength.

1 FRP tube 2 top plate
3 Lower 4 Abdominal Plates

Claims (2)

An FRP tube 10 composed of an upper plate 2, a lower plate 3 and an abdominal plate 4 having a plurality of polygonal hollow cross sections,
One side of the FRP tube 10 is provided with a first downward protrusion coupling portion 150a and a second downward protrusion coupling portion 150b, wherein the first downward protrusion coupling portion 150a is the upper plate 2. The upper extension is further formed in the middle in the middle of the upper extension portion 51 is formed to extend further to the side, and further exists in the transverse side from the position where the first downward protrusion coupling portion 150a is formed Forming a portion (61), wherein the second downward protrusion coupling portion (150b) is formed to protrude downward from the outer surface of the outer abdominal plate (4);
On the other side of the FRP tube 10 and the first upward protrusion coupling portion 151a which is mechanically coupled in a snap-fit form so as to be detachable from the first and second downward protrusion coupling portions 150a and 150b, respectively. The second upward protrusion coupling part 151b is formed, and the first upward protrusion coupling part 151a protrudes upward from the outer side of the outer abdominal plate 4, and the second upward protrusion coupling part 151b is provided. The lower plate 3 is provided upward in the middle of the lower extension part 52 which is further extended to the outside, and further extends in the transverse side from the position where the second upward protrusion coupling part 151b is formed. The part constitutes the lower extension 62;
Of the FRP tube 10 in which the second downward protrusion coupling part 150b is formed so that the lower extension 62 provided on the other side of the front neighboring FRP tube 20 can be covered and joined by an adhesive. On the bottom surface of the lower plate 3 from one side, a lower cross-sectional reduction portion 72 of a concave shape corresponding to the thickness of the lower expansion portion 62 is formed;
The first upward protrusion coupling part 151a is formed so that the upper extension 61 provided on one side of the rear neighboring FRP tube 30 can be covered and joined by an adhesive. On the upper surface of the upper plate 2 from the other side, a concave upper cross section reduction portion 71 corresponding to the thickness of the upper expansion portion 61 is formed;
The protrusion coupling parts 150a, 151a, 150b, and 151b are formed with protrusions 150c and 151c corresponding to each other to form a mechanical coupling by being bitten with each other, so that the protrusions 150a, 151a, 150b and 151b are perpendicular to the neighboring FRP tubes 20 and 30. FRP tube, characterized in that the bottom plate is coupled by a snap-fit mechanical detachable form.
A bottom plate composed of a top plate (2), a bottom plate (3) and an abdominal plate (4) having a plurality of polygonal hollow cross-sections FRP tubes (10, 20, 30) side by side side by side,
The FRP tube (10, 20, 30),
A first downward protrusion coupling portion 150a and a second downward protrusion coupling portion 150b are provided at one side thereof, and the first downward protrusion coupling portion 150a is formed by extending the upper plate 2 further to the side. Is formed in the middle in the middle of the upper extension portion 51, the upper extension portion further exists in the transverse side from the position where the first downward protrusion coupling portion (150a) is formed an upper expansion portion 61, The second downward protrusion coupling part 150b is formed to protrude downward from the outer surface of the outer abdominal plate 4;
On the other side, the first upward protrusion coupling portion 151a and the second upward protrusion coupling portion (151a) which are mechanically coupled in a snap-fit form to be detachably attached to the first and second downward protrusion coupling portions 150a and 150b, respectively ( 151b is formed, and the first upward protrusion coupling part 151a is provided to protrude upward from the outer side of the outer abdominal plate 4, and the second upward protrusion coupling part 151b has the lower plate 3 facing outward. The lower extension portion further provided upward in the middle of the lower extension portion 52 that is further extended, and further exists in the transverse side from the position at which the second upward protrusion coupling portion 151b is formed, is the lower extension portion 62. Make up;
The FRP tube 10 in which the second downward protrusion coupling part 150b is formed so that the lower extension 62 provided on the other side of the neighboring FRP tube 20 can be covered and joined by an adhesive. A lower end face reduction portion 72 having a concave shape corresponding to the thickness of the lower extension portion 62 is formed on the bottom surface of the lower plate 3 from one side of the bottom plate 3;
The FRP tube 10 in which the first upward protrusion coupling part 151a is formed so that the upper extension 61 provided on one side of the neighboring FRP tube 30 can be covered and joined by an adhesive. On the upper surface of the upper plate 2 from the other side of the upper side), an upper end reduction portion 71 of concave shape corresponding to the thickness of the upper expansion portion 61 is formed;
The protrusion coupling parts 150a, 151a, 150b, and 151b are formed with protrusions 150c and 151c respectively corresponding to each other to form a mechanical coupling;
FRP tube (10, 20, 30) is fitted in a vertical direction to form a snap-fit type mechanical coupling between the up and down projection engaging portion, the upper extension 61 and the upper cross-sectional reduction portion ( 71 is a bottom plate made of an assembly of the FRP tube, characterized in that integrally coupled to each other by bonding between the joint between the lower expansion portion 62 and the lower cross-sectional reduction portion (72).

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