JP7140859B2 - Joint structure and joining method of floor slab and steel girder - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act On September 9, 2020, Yusuke Fujii, Keisen Wada, Takeshi Kano, and Rancoschamira published a summary of the 75th Annual Scientific Lecture of the Japan Society of Civil Engineers. On September 9, 2020, Yusuke Fujii, Keisen Wada, Takeshi Kano, and Rancoschamira posted on the website address "(Address of the Japan Society of Civil Engineers)". From September 9th to 11th, 2020, Yusuke Fujii made a presentation at the 75th Annual Academic Lecture Meeting of the Japan Society of Civil Engineers (website). On October 29, 2020, Rancoschamira published a summary of lectures at the 29th Symposium on the Development of Prestressed Concrete by the Society of Prestressed Concrete Engineers. On October 29, 2020, Rancoschamira made a presentation at the 29th Symposium on the Development of Prestressed Concrete by the Society of Prestressed Concrete Engineers (held on the web). On October 1, 2020, Sumitomo Mitsui Construction Co., Ltd. posted on the website address “https://www.smcon.co.jp/service/RandD/report-2020/02.html”.

TECHNICAL FIELD The present invention relates to a joining structure and joining method of a floor slab and a steel girder.

In recent years, a large number of floor slab replacement works for bridges and the like have been carried out. As a method of joining the floor slab to the steel girder, a through hole is made through the floor slab in the thickness direction, a stud is placed inside the through hole, the lower end of the stud is joined to the upper surface of the steel girder, and then mortar is applied. is generally used to fill the through holes. However, in this method, since the mortar penetrates the floor slab in the thickness direction, moisture and salt may enter through the gap between the mortar and the side wall of the through hole and reach the bottom surface of the floor slab. Considering the maintenance of roads, it is desirable to avoid deterioration in the durability of joints due to such phenomena. Patent Document 1 discloses a connection structure between a precast floor slab and a steel girder. The floor slab is provided with a recess opening to the lower surface of the floor slab, a stud is provided on the upper surface of the steel girder, and the floor slab is positioned on the steel girder such that the stud is accommodated in the recess. The recess is then filled with non-shrinkage mortar. According to this connection structure, a path for water and salt that connects the upper surface and the lower surface of the floor slab is not formed, so the durability of the joint can be enhanced.

Japanese Patent Application Laid-Open No. 2020-100966

Floor slabs are generally made of precast, and the joining of floor slabs is done on site. A connection structure is provided between the floor slabs, and the connection structure is formed between the floor slabs to be newly installed and the floor slabs that have already been installed. For that purpose, it is necessary to adjust the position while moving the floor slab to be newly installed in the girder direction. Patent Literature 1 does not disclose this work, nor does it disclose the configuration of a joint structure that enables this work.

SUMMARY OF THE INVENTION An object of the present invention is to provide a joint structure and joining method of a floor slab and a steel girder, which does not form a through-hole penetrating the floor slab and is excellent in workability.

The floor slab and steel girder joint structure of the present invention comprises a steel girder, precast first and second floor slabs installed adjacent to each other on the steel girder, and provided on the upper surface of the steel girder. It has a projecting body and mortar for joining the second floor slab to the steel girder. The second floor slab has a recess opening to the bottom surface, the projecting body is accommodated in the recess, and the recess is filled with mortar. The first floor slab has a first connection part, the second floor slab has a second connection part, and the first connection part and the second connection part are fitted in the girder direction, A connection structure is formed between the first floor slab and the second floor slab . The minimum distance between the projecting body and the side wall of the recess on the side of the first floor slab in the girder direction is larger than the fitting length of the first and second connecting portions.

The method of joining a floor slab and a steel girder according to the present invention includes a first placing step of placing a first floor slab on top of the steel girder, and a precast steel plate on the steel girder adjacent to the first floor slab. A second placement step of arranging the second floor slab, a first joining step of joining the first deck slab to the steel girder, and a second joining step of joining the second deck slab to the steel girder and have A projecting body is provided on the upper surface of the steel girder, the second floor slab has a recess opening to the lower surface, the first floor slab has a first connection portion, and the second floor slab has a second connection. In the second placement step, the second floor slab is placed on the steel girder so that the second connection portion is spaced apart from the first connection portion in the girder direction while the projecting body is accommodated in the recess. A connection structure is formed between the first floor slab and the second floor slab by the first positioning step of positioning and the overlapping of the first connection portion and the second connection portion in the girder direction. and a second positioning step of bringing the second floor slab closer to the first floor slab. A second joining step comprises filling the recesses with mortar. At the end of the second positioning step, the minimum distance between the projecting body and the side wall of the recess on the first floor slab side in the girder direction is greater than the fitting length of the first and second connecting portions .

ADVANTAGE OF THE INVENTION According to this invention, the joint structure and joining method of a floor slab and a steel girder which do not form the through-hole which penetrates a floor slab, and are excellent in workability can be provided.

1 is a perspective view of a floor slab and a steel girder to which the floor slab-steel girder joint structure of the present invention is applied; FIG. It is a perspective view which shows the lower surface of the floor slab shown in FIG. 2 is a cross-sectional view along line AA of FIG. 1 of a joint structure according to an embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view along line BB of FIG. 1 of a joint structure according to one embodiment of the present invention; It is a figure which shows the construction procedure (before construction) of the joining structure which concerns on one Embodiment of this invention. It is a figure which shows the construction procedure (arrangement process) of the joining structure which concerns on one Embodiment of this invention. It is a figure which shows the construction procedure (joining process) of the joining structure which concerns on one Embodiment of this invention. It is a figure which shows the construction procedure (tensing process) of the joining structure which concerns on one Embodiment of this invention. It is a figure which shows the construction procedure (joining process) of the joining structure which concerns on one Embodiment of this invention.

Hereinafter, embodiments of a joint structure 1 between a floor slab 2 and a steel girder 3 and a method for connecting the floor slab 2 and a steel girder 3 according to the present invention will be described with reference to the drawings. In the following description, the direction in which the steel girder 3 extends, that is, the longitudinal direction of the steel girder 3 is called the girder row direction X, and the width direction of the steel girder 3 is called the girder width direction Y. The girder row direction X and the girder width direction Y are orthogonal to each other, and the girder row direction X and the girder width direction Y are orthogonal to the vertical direction Z in general. 1 is a perspective view of the floor slab 2 and the steel girder 3, and FIG. 2 is a perspective view showing the lower surface 21 of the floor slab 2 shown in FIG. FIG. 3 is a cross-sectional view of the steel girder 3 and the floor slab 2 along line AA in FIG. 2 is an enlarged view of version 2. FIG. FIG. 4 is a cross-sectional view of the steel girder 3 and floor slab 2 taken along line BB in FIG. Since the floor slabs 2 are installed in order one by one in the girder direction X, the floor slabs 2 installed on the steel girders 3 in advance are called the first floor slab 2A, and immediately after the first floor slab 2A, the first floor slab 2A. The floor slab 2 installed on the steel girder 3 adjacent to the floor slab 2A may be called a second floor slab 2B.

The steel girder 3 consists of, for example, four steel beams 31, and a large number of precast floor slabs 2 are arranged in the girder row direction X thereon. The length of each floor slab 2 in the girder direction X is 1.5 to 3 m, and the length in the girder width direction Y is approximately equal to the full width of the steel girder 3 . A filling material 4 made of mortar is filled between the floor slabs 2, and prestress is applied to the floor slabs 2 as described later. The floor slab 2 has a flat plate-like main body 22 and a plurality of ribs 23 provided on the lower surface of the main body 22 . The ribs 23 are composed of vertical ribs 23X extending in the girder direction X and horizontal ribs 23Y extending in the girder width direction Y. The vertical ribs 23X are provided at positions facing the steel beams 31 . That is, the floor slab 2 is fixed to the steel girder 3 at the positions of the longitudinal ribs 23X.

The floor slab 2 does not contain materials that may corrode, such as reinforcing bars and PC steel materials. Therefore, the burden of future maintenance will be reduced. Specifically, the floor slab 2 is made of high-strength fiber-reinforced concrete with a design standard strength of 80 N/mm ² , and aramid FRP rods are used as tendons 5 . The floor slab 2 has a recessed portion 24 that opens to the lower surface 21 . The recess 24 is provided in the vertical rib 23X. The recesses 24 are filled with mortar 7 . The recesses 24 need only be provided at least partly in the thickness direction of the vertical ribs 23X, and may penetrate through the vertical ribs 23X and may be provided partly in the thickness direction of the main body 22 . No reinforcement is installed around the recess 24 . The concave portion 24 has a rectangular cross section that is long in the girder direction X and short in the girder width direction Y, but as will be described later, what is important is the dimension in the girder direction X, and the dimension in the girder width direction Y is the minimum required for construction. As long as the dimensions are secured. Therefore, the cross-sectional shape of the recess 24 need not be rectangular, but may be square, circular, elliptical, or the like. The depth of the recess 24 can be determined by considering the strength of the floor slab 2, the length of attachment of the mortar to the projecting body 6 (described later), the arrangement space of the upper air discharge section 9 described later, and the like. The structure of the floor slab 2 is not particularly limited, and for example, a precast floor slab made of reinforced concrete can be used. Also, the tendon 5 is not limited to aramid FRP, and other FRP tendons such as PC steel and CFPC (Carbon Fiber Reinforced Polymer) can be used.

The projecting body 6 of this embodiment, which is provided on the upper surface of the steel girder 3, is a stud welded to the upper surface 32 of the steel girder 3. The protrusion 6 is accommodated in the recess 24 and embedded in the mortar 7 filled in the recess 24 . The projecting body 6 transmits the horizontal force transmitted from the floor slab 2 through the mortar 7 to the steel girder 3 . As long as the shear force generated by the horizontal force can be transmitted to the steel girder 3, the shape of the protruding body 6 is not limited, and it may be a rod-shaped body or a box-shaped body other than the stud.

Mortar 7 joins floor slab 2 to steel girder 3 . A non-shrinking mortar is preferably used as the mortar 7 . The mortar 7 is filled in the recesses 24 as described above, and is continuously provided in the girder direction X between the floor slab 2 and the steel girder 3 . An upper air discharge part 9 is connected to the upper part of the recess 24 in order to confirm that the recess 24 is filled with the mortar 7 . Since the upper air discharge part 9 is connected to the upper surface 25 of the recess 24 , it can be reliably confirmed that the recess 24 is filled with the mortar 7 . The upper air discharge part 9 may be connected to a position other than the upper surface 25 of the recess 24, but in that case as well, it is preferably connected to a position near the upper surface 25 of the recess 24 as much as possible. The upper air discharge part 9 can be formed of, for example, a resin embedded in the floor slab 2, a wooden frame, a vinyl tube, or the like. Before attaching the floor slab 2 to the steel girder 3, it is preferable to confirm that a continuous flow path is formed from one end of the upper air discharge section 9 to the other end. The upper air discharge part 9 rises upward from the upper surface 25 of the recess 24 , bends downward in the middle, and opens toward the lower surface 21 of the floor slab 2 . As a result, both the end opening of the upper air discharge portion 9 and the end opening of the lower air discharge portion 9, which will be described later, are positioned on the side of the lower surface 21 of the floor slab 2, so that the filling of the mortar 7 can be easily confirmed. can. Further, since the upper air discharge part 9 does not penetrate the floor slab 2 in the thickness direction, a path for moisture or salt passing through the floor slab 2 is not formed.

The floor slab 2 is formed with a through hole 26 extending in the girder direction X for inserting the tendon 5 . Specifically, the first floor slab 2A has a plurality of first through holes 26A extending in the girder direction X, and the second floor slab 2B has a plurality of second through holes 26A extending in the girder direction X. 26B (see FIGS. 6-9). A first connecting portion (coupler) 27A is provided at one end of the first through hole 26A facing the second through hole 26B, and a first connecting portion (coupler) 27A is provided at one end of the second through hole 26B facing the first through hole 26A. 2 connecting portions (couplers) 27B are provided. The first connecting portion 27A is a pipe protruding from the end face of the first floor slab 2A facing the second floor slab 2B, and the second connecting portion 27B is the first connecting portion of the second floor slab 2B. It is a tube protruding from the end face facing the floor slab 2A. The first and second connection portions 27A, 27B are concentric with the corresponding first and second through holes 26A, 26B in a state where the first and second floor slabs 2B are attached, and one side is connected to the other side. The outer diameter is slightly different so that it fits. The configuration of the first connection portion 27A and the second connection portion 27B is not limited to this. Alternatively, the second connecting portion 27B may be a pipe that protrudes from the end face of the second floor slab 2B facing the first floor slab 2A and fits into the opening. In any case, the first connection portion 27A and the second connection portion 27B are overlapped in the column direction X to form the connection structure 28 between the first floor slab 2A and the second floor slab 2B. (See FIG. 6(b)). The connection structure 28 connects the first through-hole 26A and the second through-hole 26B to form a continuous space 29 partitioned from the surroundings. A tendon 5 is inserted to apply a compressive force to the floor slabs 2A, 2B. As a result, when filling the filler 4 between the first floor slab 2A and the second floor slab 2B, the filler 4 flows into the first through-hole 26A and the second through-hole 26B. can be prevented. Moreover, by tensioning the tendons 5, the strength of the first and second floor slabs 2A and 2B can be increased.

Next, a method for forming the joint structure 1 between the floor slab 2 and the steel girder 3 explained above, or a method for joining the floor slab 2 and the steel girder 3 will be explained. In the following description, the first floor slab 2A is already placed on the steel girder 3, and the second floor slab 2B is placed on the steel girder 3 adjacent to the first deck 2A. FIG. 5 shows the first floor slab 2A and the floor slab 2A' installed just before it. A projecting body 6 (stud) is installed in advance at a predetermined position on the upper surface 32 of the steel girder 3 . The joining method is an arrangement step of arranging the second floor slab 2B adjacent to the first floor slab 2A on the steel girder 3 to which the first floor slab 2A is fixed. and a joining step of joining the floor slab 2B to the steel girder 3.

The placement process includes a first positioning process (see FIG. 6(a)) and a second positioning process (see FIG. 6(b)). In the first positioning step, the second floor slab 2B is lifted by a lifting machine such as a crane, and placed at a predetermined position on the steel girder 3 so that the protrusions 6 are accommodated in the recesses 24 . The vertical distance between the second floor slab 2B and the steel girder 3 is adjusted by a spacer (not shown). At this time, as shown in FIG. 6(a), the second floor slab 2B is positioned with respect to the steel girder 3 so that the second connection portion 27B is separated from the first connection portion 27A in the girder direction X. do. Although the recessed portion 24 is shifted to the right side relative to the protruding body 6, it does not interfere with the side wall 241 of the recessed portion 24 because the dimension of the recessed portion 24 is given a margin. After that, in the second positioning step, as shown in FIG. 6(b), the second floor slab 2B is moved to the left. That is, the second floor slab 2B is brought closer to the first floor slab 2A. By overlapping the first connection portion 27A and the second connection portion 27B in the girder direction X, the second connection portion 27B is connected to the first connection portion 27A, and the first floor slab 2A and the second floor are connected. A connection structure 28 is formed between the plate 2B. At this time, it is preferable that the protruding body 6 is positioned substantially in the center of the concave portion 24 in the girder direction X. As shown in FIG. As can be seen from FIG. 6(b), the distance d2 between the projecting body 6 and the side wall 241 of the recess 24 (the distance d2 is the first floor slab 2A side) is larger than the overlapping length d1 of the first and second connecting portions 27A and 27B. In practice, as shown in FIG. 6(c), a margin G1 for construction is secured between the first connection portion 27A and the second connection portion 27B, and the sidewalls of the protrusion 6 and the recess 24 are provided. 241, it is preferable to secure a construction allowance G2. The construction allowance G2 includes an allowance for absorbing elastic deformation (compressive deformation) that occurs in the floor slab 2 due to the tension of the tendon 5 . The allowances G1 and G2 can be appropriately set according to construction conditions. Since d2=d1+G1+G2, d2-d1=G1+G2. In other words, the interval d2 should be larger than the overlapping length d1 of the connecting portion, but in reality it is preferable that the overlapping length d1 is larger than the total of the margins G1 and G2.

Next, a joining process is performed. First, as shown in FIG. 7, the gap 12 between the first floor slab 2A and the second floor slab 2B is filled with mortar to form the filling material 4. As shown in FIG. After that, after installing the required number of floor slabs 2, the tendons 5 are inserted into the through holes 26 as shown in FIG. .

Next, as shown in FIG. 9, mortar 7 is continuously provided between each floor slab 2 and steel girder 3 . The mortar 7 also fills the recesses 24 . The second floor slab 2B will be described below as an example. 9(a) is a cross-sectional view taken along line AA of FIG. 1, and FIG. 9(b) is a cross-sectional view taken along line BB of FIG. Although FIG. 9(b) shows the mortar filling section 8, the upper air discharge section 9, and the lower air discharge section 10, they may be positioned at different positions in the girder direction X. As shown in FIG. A formwork 11 is provided between the steel girder 3 and the second floor slab 2B, and the mortar 7 is filled from a mortar filling section 8 installed between the second floor slab 2B and the steel girder 3. The mortar filling part 8 is, for example, a vinyl hose that penetrates the mold 11 . A lower air discharge section 10 is further provided between the second floor slab 2B and the steel girder 3. As shown in FIG. The lower air discharge part 10 is, for example, a vinyl hose passing through the mold 11 . The recesses 24 are filled with the mortar 7 until the mortar 7 flows out from the upper air discharge part 9 and the lower air discharge part 10 . As a result, it can be confirmed that the space between the second floor slab 2B and the steel girder 3 and the recesses 24 are filled with the mortar 7 . The lower air discharge section 10 is preferably provided at the end of the space to be filled. (not shown)). The upper air discharge part 9 remains inside the second floor slab 2B even after the joining process, and the inside of the upper air discharge part 9 is filled with mortar. The mortar filling portion 8 and the lower air discharge portion 10 may be removed or left after the joining process.

In the above-described joining process, the filling material 4 is first formed in the gap 12, then the tendon 5 is tensioned, and then the mortar 7 is filled. can be formed and the prestressing tendon 5 can also be tensioned.

Although the present invention has been described by way of one embodiment, the present invention is not limited to this embodiment. For example, rebar joints can be provided between floor slabs. Joints of reinforcing bars are formed by overlapping looped reinforcing bars projecting from opposite side surfaces of floor slabs on both sides in the girder direction X. As shown in FIG. Therefore, the loop reinforcement serves as the first and second connection portions 27A and 27B, and the joint serves as the connection structure 28 . In this case also, it is necessary to move the floor slab in the girder direction X to form the joint, and the present invention can be suitably applied.

Further, in the above embodiment, the first floor slab 2A is fixed in advance to the steel girder 3 with mortar 7, then the second floor slab 2B is placed on the steel girder 3, and the filler 4 is used to secure the first floor slab 2B to the steel girder 3. It is joined to the plate 2A and finally fixed to the steel girder 3 with mortar 7. However, the first floor slab 2A and the second floor slab 2B (and the subsequent floor slabs in some cases) are placed on the steel girder 3, joined to each other with the filling material 4, and then filled with the mortar 7. Then, the first floor slab 2A and the second floor slab 2B (and the subsequent floor slabs in some cases) may be fixed together to the steel girder 3. That is, the method of joining a floor slab and a steel girder according to the present invention includes a first placement step of placing the first floor slab on the steel girder, and A second arranging step of arranging a second precast floor slab, a first joining step of joining the first floor slab to the steel girder, and a second joining step of joining the second floor slab to the steel girder. and a joining step. In the above embodiment, the first placement step, the first bonding step, the second placement step, and the second bonding step are performed in this order, but in the modified example, the first placement step, the second placement step, The first and second bonding steps are performed in order.

1 Joint structure of floor slab and steel girder 2 Floor slab 2A First floor slab 2B Second floor slab 3 Steel girder 5 Tendon 6 Projected body 7 Mortar 8 Mortar filling section 9 Upper air discharge section 10 Lower air discharge section 22 Main body 23 Rib 24 Recess 26A First through hole 26B Second through hole 27A First connection part 27B Second connection part 28 Connection structure X Column direction

Claims (21)

A steel girder, precast first and second floor slabs installed adjacent to each other on the steel girder, projecting bodies provided on the upper surface of the steel girder, and the second floor slab. a mortar for joining to the steel girder,
The second floor slab has a recess opening to the bottom surface, the projecting body is accommodated in the recess, and the recess is filled with the mortar,
The first floor slab has a first connecting portion, the second floor slab has a second connecting portion, and the first connecting portion and the second connecting portion fit in the girder direction. A connection structure is formed between the first floor slab and the second floor slab by mating,
The floor slab and the steel, wherein the minimum distance between the projecting body and the side wall of the recess on the side of the first floor slab in the girder direction is greater than the fitting length of the first and second connecting portions. Girder joint structure. 2. The joining structure according to claim 1, wherein said first connecting portion is an opening provided in an end surface of said first floor slab facing said second floor slab. 2. The joining structure according to claim 1, wherein said first connecting portion is a pipe protruding from an end face of said first floor slab facing said second floor slab. 4. Any one of claims 1 to 3, wherein the second connecting portion fits into the opening of the first connecting portion by sliding the second floor slab toward the first floor slab. The joint structure described in the paragraph. 5. The joining structure according to claim 1, wherein said protruding body is provided at a different position from said connection structure in said girder direction. 6. The joining structure according to any one of claims 1 to 5, wherein there is no through passage that penetrates each of the first floor slab and the second floor slab in the thickness direction. The first floor slab extends in the girder direction and has a first through hole provided with the first connecting portion at one end thereof. The second floor slab extends in the girder direction at one end of the a second through-hole provided with a second connecting portion, wherein the first and second through-holes and the connection structure form a continuous space partitioned from the surroundings;
The joint structure according to any one of claims 1 to 6 , wherein a tendon is inserted into the space to apply a compressive force to the first and second floor slabs. 8. The joining structure according to any one of claims 1 to 7 , comprising an upper air exhaust connected to the upper part of said recess. 9. The joining structure according to claim 8 , wherein said upper air discharge part is connected to the upper surface of said recess. The joint structure according to claim 8 or 9 , wherein said upper air discharge part opens to the lower surface side of said second floor slab. The mortar is provided continuously in the girder row direction between the second floor slab and the steel girder, and a mortar filling section and a lower air discharge section are provided between the second floor slab and the steel girder. The joint structure according to any one of claims 8 to 10 , wherein a is provided. The joint structure according to claim 11 , wherein the lower air discharge portion is provided at an end portion of the second floor slab in the girder direction. The second floor slab has a flat plate-like main body and a plurality of ribs provided on the lower surface of the main body and extending at least in the girder direction. A joint structure according to any one of claims 1 to 12 , provided. A first placement step of placing the first floor slab on the steel girder;
a second arranging step of arranging a precast second floor slab on the steel girder adjacent to the first floor slab;
a first joining step of joining the first floor slab to the steel girder;
a second joining step of joining the second floor slab to the steel girder;
A projecting body is provided on the upper surface of the steel girder, the second floor slab has a recess opening to the lower surface, the first floor slab has a first connection portion, and the second floor slab has a first connecting portion. the plate has a second connection,
The second arranging step includes:
The second floor slab is positioned with respect to the steel girder so that the second connecting portion is separated from the first connecting portion in the girder direction while the projecting body is accommodated in the recess. a first positioning step to
The connecting structure is formed between the first floor slab and the second floor slab by fitting the first connection portion and the second connection portion in the girder direction. a second positioning step of bringing the second floor slab closer to the first floor slab;
The second bonding step includes filling the recess with mortar,
At the end of the second positioning step, the minimum distance between the projecting body and the sidewall of the recess on the side of the first floor slab in the girder direction is the distance between the first and second connecting portions. A method of joining deck slabs and steel girders that is larger than the fitting length . 15. The joining method according to claim 14, wherein said first connecting portion is an opening provided in an end face of said first floor slab facing said second floor slab. 15. The joining method according to claim 14, wherein said first connecting portion is a pipe projecting from an end face of said first floor slab facing said second floor slab. 17. Any one of claims 14 to 16, wherein the second connecting portion fits into the opening of the first connecting portion by sliding the second floor slab toward the first floor slab. The joining method described in the item. The joining method according to any one of claims 14 to 17, wherein the protruding body is provided at a different position from the connection structure in the girder direction. 19. The joining method according to any one of claims 14 to 18, wherein there is no through-path that penetrates each of the first floor slab and the second floor slab in the thickness direction. 20. The method according to any one of claims 14 to 19, further comprising an upper air discharge connected to the upper part of said recess, wherein said bonding step fills said recess with said mortar until said mortar flows out from said upper air discharge. The joining method according to any one of the items . The mortar is continuously provided between the second floor slab and the steel girder, a lower air discharge section is provided between the second floor slab and the steel girder, and in the joining step, The joining method according to claim 20 , wherein the mortar is filled until the mortar flows out from the lower air discharge part.

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