Plug member, CFT steel pipe, sealing method of vapor release hole in CFT steel pipe, and construction method of CFT column

Abstract

To provide a plug member and the like making it unnecessary for them to be removed from a vapor release hole after sealing the vapor release hole with them when filling the inside of a CFT steel pipe with concrete.SOLUTION: A plug member inserted in a vapor release hole of a CFT steel pipe to seal the vapor release hole comprises: a shaft part; a surrounding member surrounding the shaft part; an engagement mechanism rotatably attached on an end of the shaft part and inserted in the vapor release hole to be rotated and engaged inside the CFT steel pipe; and a fastening mechanism arranged on the other end of the shaft part to fix the shaft, the engagement mechanism, and the surrounding member on the CFT steel pipe, wherein the surrounding member melts at the time of fire to form a gap releasing vapor generated inside the CFT steel pipe in the vapor release hole.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plug member for sealing a steam vent hole of a CFT steel pipe, a CFT steel pipe, a method for sealing a steam vent hole of a CFT steel pipe, and a method for constructing a CFT column. [Background technology]

[0002] Conventionally, as a structure for building columns, for example, a CFT structure formed by filling a vertically erected steel pipe with concrete is known (see, for example, Patent Document 1). In a CFT structure, a steam vent hole is provided in the steel pipe to release steam generated in the steel pipe in the event of a fire and reduce pressure. If this steam vent hole is blocked by concrete, steam in the steel pipe cannot escape, so when pouring the filled concrete, it is necessary to manage the steam vent hole so that it is not blocked. The Ministry of Land, Infrastructure, Transport and Tourism Notification indicates that for CFT steel pipes used for columns, two steam vent holes of 10 mm to 20 mm in size should be installed at the same height in the head and base of the column, evenly spaced from the center of the column, and that the steam vent holes should be installed at intervals of 5 m or less from the vertical axis. In order to prevent the steam vent holes provided in the CFT steel pipes from being blocked by concrete when the CFT steel pipes are filled with concrete, the steam vent holes are plugged with plugs or a nut is welded to the steam vent hole and a bolt inserted into the steam vent hole is screwed into the nut to block the steam vent hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-150831 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the steam vent hole is blocked with a plug or a bolt, it must be removed from the steel pipe after filling with concrete. This requires a lot of time to remove the plug or bolt. In particular, when blocking with a bolt, it requires the steps of welding a nut to the steel pipe, screwing the bolt, and removing it, which is very time-consuming. In addition, because plugs and bolts need to be removed reliably, there was also the issue that the task of checking that they had been removed was time-consuming.

[0005] The present invention has been made in consideration of these circumstances, and has an object to provide a plug member that seals the steam vent hole when concrete is filled into the steel pipe of a CFT but does not need to be removed from the steam vent hole afterwards, a CFT steel pipe, a method of sealing a steam vent hole in a CFT steel pipe, and a method of constructing a CFT column. [Means for solving the problem]

[0006] In order to achieve this object, the plug member of the present invention comprises: A plug member that is inserted into a steam vent hole of a CFT steel pipe to seal the steam vent hole, A shaft portion, A surrounding material surrounding the shaft portion; A locking mechanism that is rotatably attached to one end of the shaft portion, inserted into the steam vent hole, and locked by rotating inside the CFT steel pipe; A fastening mechanism is provided at the other end of the shaft portion and fixes the shaft portion, the locking mechanism, and the surrounding material to the CFT steel pipe, The surrounding material is characterized in that it melts in the event of a fire and forms a gap in the steam vent hole to allow steam generated inside the CFT steel pipe to escape. Other features of the present invention will become apparent from the following detailed description of the present invention and the accompanying drawings. Effect of the Invention

[0007] According to the present invention, it is possible to provide a plug member that blocks the steam vent hole when concrete is filled into the steel pipe of a CFT but does not need to be removed from the steam vent hole afterwards, a CFT steel pipe, a method for sealing a steam vent hole in a CFT steel pipe, and a method for constructing a CFT column. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a vertical cross-sectional view showing a state in which the plug member of the first embodiment is attached to a steam vent hole. [Diagram 2] FIG. 2 is an exploded view showing the configuration of the plug member of the first embodiment. [Diagram 3] 5A to 5C are diagrams showing a method of attaching the plug member of the first embodiment to a steam vent hole. [Figure 4] FIG. 2 is a top view of the plug member of the first embodiment attached to a steel pipe. [Diagram 5] 1 is a top view of a plug member according to a first embodiment attached to an annular steel pipe. FIG. [Figure 6] FIG. 11 is a vertical cross-sectional view showing a state in which a plug member of a second embodiment having two washers is attached to a steam vent hole. [Figure 7] 13 is a view from above showing a state in which a plug member of a second embodiment having two washers is attached to a steam vent hole. FIG. [Figure 8] FIG. 11 is a vertical cross-sectional view showing a state in which a plug member of a second embodiment having one washer is attached to a steam vent hole. [Figure 9] 13 is a view from above showing a state in which a plug member of a second embodiment having one washer is attached to a steam vent hole. FIG. [Figure 10] FIG. 11 is a view of a first modified example of a washer used in the plug member of the second embodiment, as viewed from the outside of a steel pipe. [Figure 11] FIG. 11 is a view of a second modified example of a washer used in the plug member of the second embodiment, as viewed from the outside of a steel pipe. [Figure 12] 10 is a vertical cross-sectional view showing a state in which a plug member in which a nut abuts against a surrounding material is attached to a steam vent hole. FIG. [Figure 13]13 is a view from above showing a state in which a plug member with a nut abutting against a surrounding material is attached to a steam vent hole. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] At least the following points will become apparent from the following specification and drawings. Aspect 1: A plug member that is inserted into a steam vent hole of a CFT steel pipe to seal the steam vent hole, the plug member having a shaft, a surrounding material surrounding the shaft, a locking mechanism that is rotatably attached to one end of the shaft, inserted into the steam vent hole and locks by rotating inside the CFT steel pipe, and a fastening mechanism that is provided at the other end of the shaft and fixes the shaft, the locking mechanism, and the surrounding material to the CFT steel pipe, wherein the surrounding material melts in the event of a fire to form a gap in the steam vent hole through which steam generated inside the CFT steel pipe can escape.

[0010] According to the plug member of aspect 1, the shaft portion surrounded by the surrounding material is inserted into the steam vent hole of the CFT steel pipe, a locking mechanism attached to one end of the shaft portion rotates and locks inside the CFT steel pipe, and the shaft portion, locking mechanism and surrounding material are fixed to the CFT steel pipe by a tightening mechanism provided at the other end of the shaft portion. Therefore, the plug member is fixed to the CFT steel pipe with the surrounding material surrounding the shaft portion inserted into the steam vent hole. Therefore, it is possible to block the steam vent hole by attaching the plug member.

[0011] In addition, the surrounding material of the plug member fixed to the CFT steel pipe melts in the event of a fire, forming a gap in the steam vent hole to let out steam generated inside the CFT steel pipe, making it possible to release water vapor even when the plug member is attached to the CFT steel pipe. This makes it possible to provide a plug member that closes the steam vent hole when concrete is filled into the CFT steel pipe, but does not need to be removed from the steam vent hole afterwards.

[0012] Aspect 2: A plug member as described in Aspect 1, wherein the fastening mechanism includes a nut that screws onto the shaft portion, and a spanning member that is provided between the nut and the CFT steel pipe, and the spanning member includes a leg that abuts against the surface of the CFT steel pipe, a storage section that stores the surrounding material inside, and an opening that connects the storage section to the outside, and wherein the steam is allowed to escape through the opening.

[0013] According to the plug member of the second aspect, the spanning member provided between the nut and the CFT steel pipe has a storage section for storing the surrounding material inside and an opening section that connects the storage section to the outside, and steam is allowed to escape from the opening section. Therefore, in the event of a fire, the water vapor inside the CFT steel pipe can be more reliably exhausted to the outside from the opening section.

[0014] Aspect 3: The plug member according to aspect 1, wherein the fastening mechanism includes a nut that is threadedly engaged with the shaft portion; A washer is provided between the nut and the CFT steel pipe and surrounds the shaft portion, The washer has a through hole having a diameter larger than a diameter of the shaft portion, The steam is allowed to escape through a gap formed between the shaft portion and the through hole of the washer fixed by the nut.

[0015] According to the plug member of aspect 3, the fastening mechanism provided at the other end of the shaft has a nut that screws onto the shaft, and a washer that is provided between the nut and the CFT steel pipe and surrounds the shaft, and the through hole of the washer has a larger diameter than the shaft, so that a gap is formed between the through hole and the shaft, and steam can escape through the gap. This makes it possible to more reliably exhaust water vapor inside the CFT steel pipe to the outside in the event of a fire.

[0016] Aspect 4: A plug member as described in Aspect 1, wherein the fastening mechanism includes a nut that screws onto the shaft portion, and a washer that is provided between the nut and the CFT steel pipe and surrounds the shaft portion, the washer having a contact portion that contacts the surrounding material and a gap portion that forms a gap between the washer and the nut, and the steam is allowed to escape through the gap portion.

[0017] According to the plug member of the fourth aspect, the washer that is provided between the nut and the CFT steel pipe and surrounds the shaft has a gap that forms a gap between the contact part that contacts the surrounding material and the nut, and steam is allowed to escape from the gap. Therefore, in the event of a fire, it becomes possible to more reliably exhaust water vapor inside the CFT steel pipe to the outside.

[0018] Aspect 5: A plug member as described in Aspect 1, characterized in that the tightening mechanism has a nut that screws onto the shank, and the nut is screwed onto the shank while abutting the surrounding material that protrudes outward from the surface of the CFT steel pipe, and the surrounding material melts to allow the steam to escape through a gap formed between the CFT steel pipe and the nut.

[0019] According to the plug member of the fifth aspect, the nut that screws onto the shaft is in contact with the surrounding material that protrudes outward from the surface of the CFT steel pipe and is screwed onto the shaft, so that when the surrounding material that penetrates the steam vent hole melts due to fire, a gap is created between the CFT steel pipe and the nut, and steam escapes from the gap. This makes it possible to more reliably vent water vapor inside the CFT steel pipe to the outside in the event of a fire.

[0020] Aspect 6: A CFT steel pipe, characterized in that the steam vent hole is sealed with the plug member according to any one of Aspects 1 to 5.

[0021] According to the CFT steel pipe of aspect 6, the plug member that seals the steam vent hole blocks the steam vent hole when concrete is filled into the CFT steel pipe, but does not need to be removed from the steam vent hole afterwards. Therefore, by simply erecting the CFT steel pipe and pouring concrete inside, it is possible to easily construct a CFT column that has a steam hole through which steam can escape in the event of a fire.

[0022] Aspect 7: A method for sealing a steam vent hole of a CFT steel pipe, comprising sealing the steam vent hole of the CFT steel pipe with the plug member according to any one of aspects 1 to 5.

[0023] According to the sealing method for sealing the steam vent hole of a CFT steel pipe of aspect 7, by inserting a plug member into the steam vent hole of the CFT steel pipe and fixing it with a tightening mechanism, it is possible to block the steam vent hole when filling the steel pipe of the CFT with concrete, and then seal the steam vent hole with the plug member that does not need to be removed from the steam vent hole.

[0024] Aspect 8: A method for constructing a CFT column, comprising constructing the CFT column using the CFT steel pipe in which the steam vent hole is sealed with the plug member described in any one of Aspects 1 to 5.

[0025] According to the method for constructing a CFT column of embodiment 8, it is possible to easily construct a CFT column with steam holes that allow steam to escape in the event of a fire, simply by erecting a CFT steel pipe and filling the inside with concrete.

[0026] ===About this embodiment=== Hereinafter, a plug member, a CFT steel pipe, a method for sealing a steam vent hole of a CFT steel pipe, and a method for constructing a CFT column according to one embodiment of the present invention will be described with reference to the drawings. ===First embodiment===

[0027] As shown in FIG. 1, the plug member 1 of the first embodiment seals a steam vent hole 2b formed through a pipe wall 2a of a CFT steel pipe (hereinafter referred to as a steel pipe) 2. The steam vent hole 2b is formed by penetrating the pipe wall 2a while aligning its axial direction with the wall thickness direction of the pipe wall 2a of the steel pipe 2. When constructing a CFT column (hereinafter referred to as a CFT column), the plug member 1 is inserted into the steam vent hole 2b from the outside of the steel pipe 2 to seal the steam vent hole 2b. This prevents the liquid of concrete from leaking from the steam vent hole 2b when concrete is filled into the steel pipe 2. The plug member 1 of the present invention has the function of forming a gap in the steam vent hole 2b that allows steam generated from the concrete to escape to the outside of the steel pipe 2 in the event of a fire without being removed from the steel pipe 2 after the concrete has hardened.

[0028] Incidentally, the type of steel pipe 2 may be, for example, a square steel pipe having a rectangular planar cross section, a round steel pipe having a circular planar cross section, etc., but is not limited thereto. Here, an example will be described in which a steam vent hole 2b is provided in a flat pipe wall portion 2a of a square steel pipe 2 having a rectangular planar cross section.

[0029] As shown in Figure 2, the plug member 1 has a shaft portion 3 having a threaded portion 3a, a surrounding material 4 surrounding the shaft portion 3, a rotating plate 5 constituting a locking mechanism rotatably attached to one end (hereinafter referred to as the tip end) of the shaft portion 3, a nut 6 constituting a tightening mechanism provided on the other end (hereinafter referred to as the tail end) of the shaft portion 3 and screwed into the threaded portion, and a spanning material 7 arranged between the steel pipe 2 and the nut 6.

[0030] The shaft portion 3 has a slit 3b that penetrates in the diameter direction at its tip and is open at the tip side, and a threaded portion 3a is provided on the circumferential surface on the other end side up to near the center of the shaft portion 3. A nut 6 with a flange 6a is screwed onto the threaded portion 3a.

[0031] A pin 3c is provided in the slit 3b so as to span the shaft portion 3 between portions located on both sides of the slit 3b, and a rotating plate 5 disposed in the slit 3b is rotatably supported by this pin 3c.

[0032] The rotating plate 5 has a width approximately equal to the diameter of the shaft 3, and when arranged along the shaft 3, a portion of it is accommodated in the slit 3b, with its tip end protruding beyond the tip of the shaft 3. The rotating plate 5 is formed so that the length from the position supported by the pin 3c (pin support position) to the tip end is longer than the length from the pin support position to the tail end. Therefore, when the pin 3c is aligned horizontally, the rotating plate rotates vertically due to its own weight. Also, the length from the pin support position to the tail end is longer than the radius of the steam vent hole 2b.

[0033] The surrounding material 4 is a cylindrical member made of a low melting point material, for example, a tube made of a polyethylene foam material, and it is possible to use an existing commercially available product. The outer diameter of the surrounding material 4 is approximately equal to the inner diameter of the steam vent hole 2b of the steel pipe 2, and it has a hollow part with an inner diameter approximately equal to the diameter of the shaft portion 3.

[0034] The spanning member 7 has two plate-shaped legs 7a that face each other with a gap between them, and a connecting plate portion 7b that connects one end of the two legs 7a, and has a U-shaped cross section. An insertion hole 7c through which the shaft portion 3 is inserted is provided in the approximate center of the connecting plate portion 7b. The spanning member 7 may be made by cutting an existing commercially available channel material used as a joist support, for example, to an appropriate length and forming the insertion hole 7c.

[0035] The plug member 1 is made by inserting the shaft 3 into the surrounding material 4 and the spanning material 7 in this order from the tip end, and while the shaft 3 is still inserted, the nut 6 is screwed onto the tail end of the shaft 3, whereby the shaft 3, surrounding material 4, nut 6 and spanning material 7 are integrally assembled, and the plug member 1 is in a completed and usable state. In this embodiment, the shaft 3 and nut 6 provided with the rotating plate 5 are used, but an existing commercially available product having a similar configuration, such as IT Hanger (registered trademark) manufactured by Sanko Techno Co., Ltd., may also be used.

[0036] The plug member 1 is attached to the steam vent hole 2b as follows. 3(a), for example, the surrounding material 4 is moved toward the tip side of the shaft portion 3 so that the rotating plate 5 is aligned along the axial direction of the shaft portion 3, and then the shaft portion 3 together with the surrounding material 4 is inserted into the steam vent hole 2b from the outside to the inside of the steel pipe 2. At this time, when the shaft portion 3 is moved so that the rotating plate 5 of the shaft portion 3 protrudes from the surrounding material 4 toward the inside of the steel pipe 2, the rotating plate 5 rotates by its own weight so as to be aligned vertically.

[0037] Next, as shown in Fig. 3(b), the nut 6 is rotated and moved toward the steel pipe 2 together with the spanning member 7. Then, the tip of the leg 7a is brought into contact with the outer surface 2c of the steel pipe 2. After that, the vertically oriented rotating plate 5 is brought into contact with the tip of the surrounding member 4. At this time, the two legs 7a of the spanning member 7 are positioned on either side of the steam vent hole 2b.

[0038] The length of the surrounding material 4 is set so that the leading end of the surrounding material 4 protrudes inward from the inner surface 2d of the steel pipe 2 when the trailing end of the surrounding material 4 abuts against the connecting plate portion 7b of the spanning material 7. The amount of protrusion of the surrounding material 4 into the steel pipe 2 is desirably set so that it protrudes inward from the inner surface 2d of the steel pipe 2 by several mm (e.g., 3 to 5 mm) based on the concrete-filled copper pipe (CFT) construction technical guidelines for securing the steam vent hole by screwing a bolt as a plug into the steam vent hole when filling the steel pipe 2 with concrete and removing the plugging bolt after the concrete hardens.

[0039] Thereafter, the nut 6 is further rotated to pull the shaft 3 outward from the steel pipe 2, and as shown in Figure 3(c), the rotating plate 5 is brought into contact with the inner surface 2d of the steel pipe 2, fixing the plug member 1 to the steel pipe 2. At this time, as shown in Figure 4, the lateral central portion of the tip side of the surrounding member 4 is compressed by the rotating plate 5, and portions on the left and right sides of the compressed portion remain protruding into the interior of the steel pipe 2.

[0040] The plug member 1 is attached by clamping the pipe wall portion 2a of the steel pipe 2 with the spanning member 7 and the rotating plate 5, and the inside of the steam vent hole 2b is blocked by the shaft portion 3 and the surrounding member 4 surrounding the shaft portion 3. The surrounding member 4 is arranged so as to connect between the steel pipe 2 and the spanning member 7 to the inside of the steel pipe 2. Therefore, when the surrounding member 4 melts due to a fire or the like, a gap S1 that communicates with the inside and outside of the steel pipe 2 is generated in the steam vent hole 2b, making it possible to discharge steam generated in the steel pipe 2. In FIG. 3, the gray-colored portion indicates the portion of the surrounding member 4 that is accommodated in the steam vent hole 2b, and when the surrounding member 4 melts due to a fire, a gap S1 is generated in the gray-colored portion. Here, the space between the opposing legs 7a of the spanning member 7 corresponds to a storage section 7d for storing the surrounding material 4 inside, and when the tips of the legs 7a are in contact with the outer periphery of the steel pipe 2, the openings 7e formed between the left and right ends of the spanning member 7 and the outer surface 2c of the steel pipe 2 correspond to openings open to the outside on the side of the storage section.

[0041] In the method of constructing a CFT column using the plug member 1 of the first embodiment, first, the plug member 1 is inserted into and attached to all of the steam vent holes 2b of the steel pipe 2 to be erected. Next, the steel pipe 2 with the plug member 1 attached is erected at the construction site, and then concrete is filled into the steel pipe 2. After that, the concrete hardens without removing the plug member 1, and the CFT column is constructed.

[0042] According to the plug member 1 of the first embodiment, the shaft portion 3 surrounded by the surrounding material 4 is inserted into the steam vent hole 2b of the steel pipe 2, the rotating plate 5 attached to the tip of the shaft portion 3 rotates inside the steel pipe 2, and the nut 6 on the tail end side of the shaft portion 3 is screwed, whereby the rotating plate 5 is engaged and the shaft portion 3, the straddling material 7, the nut 6 and the surrounding material 4 are fixed to the steel pipe 2. Therefore, the plug member 1 is fixed to the steel pipe 2 in a state where the surrounding material 4 surrounds the shaft portion 3 inserted into the steam vent hole 2b. Therefore, by attaching the plug member 1, it is possible to block the steam vent hole 2b.

[0043] In addition, a nut 6 is screwed onto the tail end of the shaft portion 3, and a spanning member 7 provided between the nut 6 and the steel pipe 2 has a storage section 7d in which the surrounding material 4 is stored and an opening 7e that connects the storage section 7d to the outside. Therefore, when the surrounding material 4 melts due to a fire, the inside of the steel pipe 2 is connected to the outside.

[0044] In addition, the surrounding material 4 of the plug member 1 fixed to the steel pipe 2 melts in the event of a fire, causing a gap S1 to form in the steam vent hole 2b. The surrounding material 4 is provided from inside the steam vent hole 2b to the storage section 7d of the spanning material 7, and openings 7e communicating with the outside are provided at both ends of the storage section 7d, so that when the surrounding material 4 melts, the inside of the steel pipe 2 communicates with the outside, and steam inside the steel pipe 2 escapes through the openings 7e. This makes it possible to provide a plug member 1 that blocks the steam vent hole 2b when filling the steel pipe 2 with concrete, but does not need to be removed from the steam vent hole 2b afterwards.

[0045] It is also possible to provide a method for sealing the steam vent hole of a CFT steel pipe, which seals the steam vent hole 2b by attaching a plug member 1 to the steam vent hole 2b of the steel pipe 2, and a steel pipe (CFT steel pipe) 2 with the steam vent hole 2b sealed by this sealing method. It is also possible to provide a method for constructing a CFT column, which makes it possible to easily construct a CFT column that is reliably equipped with a steam vent hole through which steam can escape in the event of a fire, simply by erecting a steel pipe (CFT steel pipe) 2 with a sealed steam vent hole 2b and pouring concrete inside.

[0046] In addition, the surrounding material 4, the straddling material 7, the shaft portion 3, and the nut 6 constituting the plug member 1 can all be existing commercially available products, so it is possible to reduce costs. In addition, since the steam vent holes 2b are provided, for example, near the foot of each floor of the building to be constructed and near the ceiling, the work of removing the plug member 1 and the work of confirming that it has been removed after filling the steel pipe 2 with concrete are accompanied by work requiring a great deal of labor, such as the need for scaffolding. Since the plug member 1 of this embodiment does not require the work of removing the plug member 1 and the work of confirming that it has been removed, it is possible to significantly reduce the number of labors, shorten the construction period, and reduce costs.

[0047] In this embodiment, as shown in FIG. 4, the straddling member 7 is arranged so that the leg 7a runs along the left-right direction and the opening 7e formed between the leg 7a and the outer surface 2c of the steel pipe 2 penetrates in the left-right direction. However, the present invention is not limited to this, and the leg 7a may be arranged in any direction. In addition, when the steel pipe 2 is cylindrical, as shown in FIG. 5, the leg 7a runs along the vertical direction and the opening 7e formed between the leg 7a and the outer surface 2c of the steel pipe 2 penetrates in the vertical direction, so that the straddling member 7 can be attached to the plug member 1 in a more stable state even if the steel pipe 2 is cylindrical. In this way, when the opening 7e formed between the outer surface 2c of the steel pipe 2 and the straddling member 7 faces upward, there is a risk that sparks generated by work at the construction site may damage the surrounding material 4, so it is desirable to take separate measures to avoid sparks. In other words, as in the above embodiment, when the legs 7a are arranged along the left-right direction and the opening 7e formed between the legs 7a and the outer surface 2c of the steel pipe 2 penetrates in the left-right direction, the legs 7a cover the upper part of the surrounding material 4, making it possible to prevent damage to the surrounding material 4 due to sparks, etc. ===Second embodiment===

[0048] In the above-mentioned first embodiment, a straddling member 7 having a U-shaped cross section is used between the steel pipe 2 and the nut 6, but in this second embodiment, the main difference is that two types of existing commercially available washers 8 and 9 are used between the steel pipe 2 and the nut 6, and other points are generally the same. Therefore, in the following, the same components as those in the first embodiment are denoted by the same reference numerals, and their explanation will be omitted.

[0049] 6 and 7, in the plug member 10 of the second embodiment, two washers 8, 9 are interposed between the surrounding material 4 and the nut 6 with the shaft portion 3 inserted therethrough. Of the two washers 8, 9, the first washer 8 arranged on the surrounding material 4 side has a through hole 8a whose inner diameter is approximately twice the diameter of the shaft portion 3. The second washer 9 arranged between the first washer 8 and the nut 6 has an outer diameter approximately the same as the outer diameter of the flange 6a of the nut 6, and an inner diameter approximately the same as the diameter of the shaft portion 3.

[0050] The plug member 10 is completed and ready for use by inserting the shaft 3 successively through the surrounding material 4, the first washer 8 and the second washer 9 in that order from the tip end, and finally screwing the nut 6 into the tail end of the shaft 3 while the shaft 3 remains inserted.

[0051] The plug member 10 of the second embodiment is attached by inserting the shaft portion 3 together with the surrounding material 4 into the steam vent hole 2b from the outside to the inside of the steel pipe 2, screwing the nut 6 from the tail end side, and compressing the surrounding material 4 with the rotating plate 5 oriented vertically by rotating, while clamping the pipe wall portion 2a of the steel pipe 2 between the rotating plate 5 and the first washer 8. At this time, the first washer 8 inserted into the shaft portion 3 arranged along a substantially horizontal direction is attached to the steel pipe 2 in a state in which the shaft portion 3 and the through hole 8a are arranged in eccentric positions relative to each other, since the inner diameter of the through hole 8a is approximately twice as large as the diameter of the shaft portion 3. Therefore, between the second washer 9 arranged substantially concentrically with the shaft portion 3 and the steel pipe 2, a gap S2 is generated that faces the steam vent hole 2b at the position where the through hole 8a is eccentric. For example, if the washer 8 is attached in a state in which it is suspended from the shaft portion 3 due to its own weight, a gap S2 is generated below the shaft portion 3.

[0052] According to the plug member 10 of the second embodiment, the surrounding material 4 of the plug member 10 fixed to the steel pipe 2 melts in the event of a fire, forming a gap S1 (FIG. 3) in the steam vent hole 2b for releasing steam generated inside the steel pipe 2, and a gap S2 generated between the second washer 9 and the through hole 8a of the first washer 8 communicates between the inside of the steel pipe 2 and the outside, allowing steam inside the steel pipe 2 to escape. For this reason, it is possible to provide a plug member 1 which closes the steam vent hole 2b when the steel pipe 2 is filled with concrete, but does not need to be removed from the steam vent hole 2b thereafter.

[0053] In the above-mentioned second embodiment, the plug member 10 has two washers 8 and 9. However, as shown in Fig. 8 and Fig. 9, the plug member 10 may have only the first washer 8. In this case, a gap S3 is formed between the first washer 8 and the flange 6a of the nut 6 and communicates with the outside through the through hole 8a.

[0054] The surrounding material 4 of the plug member 10 fixed to the steel pipe 2 melts in the event of a fire, and a gap S1 formed in the steam vent hole 2b is formed between the flange 6a of the nut 6 and the through hole 8a of the first washer 8, and communicates with the gap S3. Therefore, even when the plug member 10 is attached to the steel pipe 2, the inside and outside of the steel pipe 2 communicate with each other in the event of a fire, making it possible to exhaust water vapor. Therefore, even though the plug member 10 closes the steam vent hole 2b when concrete is filled into the steel pipe 2, it is not necessary to remove the plug member 10 from the steam vent hole 2b afterwards.

[0055] In the above second embodiment, an example has been described in which annular plate-shaped washers 8 and 9 are used, but as shown in Fig. 10, a third washer 11 (variation 1) may be used that includes an annular portion 11a having a hole with an inner diameter substantially the same as the diameter of the shaft portion 3, and a plurality of rod-shaped portions 11b provided radially outside the annular portion 11a. This third washer 11 is formed so that the length from the center of the annular portion 11a to the tip of the rod-shaped portion 11b is longer than the radius of the steam vent hole 2b.

[0056] When the plug member 12 using the third washer 11 is used, a gap S4 is generated between the flange 6a of the nut 6 and the surrounding material 4 due to a portion of the third washer 11 in the circumferential direction where the rod-shaped portion 11b is not provided. Therefore, when the surrounding material 4 melts during a fire, the inside and outside of the steel pipe 2 are connected, so that it is possible to exhaust the fire to the outside through steam generated inside the steel pipe 2. Here, in the third washer 11, the surfaces of the annular portion 11a and the rod-shaped portion 11b on the surrounding material 4 side correspond to the contact portion that contacts the surrounding material, and the annular portion 11a and the rod-shaped portion 11b correspond to the gap portion that forms a gap between the nut and the surrounding material.

[0057] 11, a fourth washer 13 (variation 2) may be used that includes an inner annular portion 13a having a hole with an inner diameter substantially the same as the diameter of the shaft portion 3, an outer annular portion 13b that is concentrically provided outside the inner annular portion 13a with a gap therebetween, and a mesh portion 13c that connects the inner annular portion 13a and the outer annular portion 13b to form a mesh shape. In this fourth washer 13, the inner diameter of the outer annular portion 13b is formed to be larger than the diameter of the steam vent hole 2b.

[0058] When the plug member 14 using the fourth washer 13 is used, a gap S5 is generated between the flange 6a of the nut 6 and the surrounding material 4 due to the mesh portion 13c of the fourth washer 13. Therefore, when the surrounding material 4 melts during a fire, the inside and outside of the steel pipe 2 are connected, so that it is possible to exhaust the fire to the outside through steam generated inside the steel pipe 2. Here, in the fourth washer 13, the surfaces of the inner annular portion 13a, the outer annular portion 13b and the mesh portion 13c on the surrounding material 4 side correspond to the contact portions that come into contact with the surrounding material, and the mesh portion 13c corresponds to the gap portion that forms a gap with the nut.

[0059] In the above second embodiment, an example was described in which washers 8, 9, 11, and 13 were interposed between the surrounding material 4 and the nut 6, but as shown in Figures 12 and 13, the flange 6a of the nut 6 may be directly abutted against the surrounding material 4. In this case, with the rotating plate 5 in a vertical position abutting against the inner surface 2d of the steel pipe 2, the surrounding material 4 protrudes to the outside of the steel pipe 2. It is desirable that the amount of protrusion of the surrounding material 4 be smaller than the length from the pin support position to the tail end side.

[0060] When using a plug member 15 that does not have an intervening member such as a washer, the flange 6a of the nut 6 that contacts the surrounding material 4 is separated from the outer surface 2c of the steel pipe 2, so that when the surrounding material 4 melts during a fire, steam inside the steel pipe 2 escapes from the gap S6 formed between the steel pipe 2 and the nut 6. This makes it possible to exhaust steam generated inside the steel pipe 2 during a fire to the outside through the steam vent hole 2b.

[0061] The above-mentioned embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The present invention can be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents thereof. [Explanation of symbols]

[0062] 1 Plug member 2 Steel pipe (CFT steel pipe) 2a Pipe wall 2b Steam vent hole 2c Outer surface of steel pipe 2d Inner surface of steel pipe 3 Shaft section 3a Threaded part 3b Slit 3c Pin 4 Surrounding material 5 Rotating plate (locking mechanism) 6 Nut (fastening mechanism) 6a Flange 7 Crossbar (fastening mechanism) 7a Legs 7b Connecting plate part 7c through hole 7d Storage area 7e opening 8 First washer (fastening mechanism) 8a through hole 9 Second washer (fastening mechanism) 10 Plug member 11 Third washer (fastening mechanism) 11a Circular section 11b Rod-shaped part 12 Plug member 13 Fourth washer (fastening mechanism) 13a Inner ring 13b Outer ring 13c Reticulum 14 Plug member 15 Plug member S1~S6 gap

Claims

1. A plug member that is inserted into a steam vent hole of a CFT steel pipe to seal the steam vent hole, A shaft portion, A surrounding material surrounding the shaft portion; A locking mechanism that is rotatably attached to one end of the shaft portion, inserted into the steam vent hole, and locked by rotating inside the CFT steel pipe; A fastening mechanism is provided at the other end of the shaft portion and fastens the shaft portion, the locking mechanism, and the surrounding material to the CFT steel pipe, The said surrounding material is a plug member characterized in that it melts in the event of a fire and forms a gap in the said steam vent hole to allow the escape of steam generated inside the said CFT steel pipe.

2. The plug member according to claim 1, The tightening mechanism includes: A nut that is screwed onto the shaft portion; A straddling member provided between the nut and the CFT steel pipe, The straddling member has a leg portion that is in contact with the surface of the CFT steel pipe, A storage section for storing the surrounding material therein; An opening communicating the storage section with the outside, A plug member characterized in that the steam is allowed to escape through the opening.

3. The plug member according to claim 1, The fastening mechanism includes a nut that is screwed onto the shaft portion; A washer is provided between the nut and the CFT steel pipe and surrounds the shaft portion, The washer has a through hole having a diameter larger than a diameter of the shaft portion, A plug member characterized in that the steam is allowed to escape through a gap formed between the shaft portion and the through hole of the washer fixed by the nut.

4. The plug member according to claim 1, The fastening mechanism includes a nut that is screwed onto the shaft portion; A washer is provided between the nut and the CFT steel pipe and surrounds the shaft portion, The washer has a contact portion that contacts the surrounding material and a gap portion that forms a gap between the washer and the nut, A plug member characterized in that the steam is allowed to escape through the gap.

5. The plug member according to claim 1, The fastening mechanism has a nut that is screwed onto the shaft portion, The nut is in contact with the surrounding material protruding outward from the surface of the CFT steel pipe and is screwed onto the shaft portion, A plug member characterized in that the surrounding material melts and the steam escapes through a gap formed between the CFT steel pipe and the nut.

6. A CFT steel pipe, wherein the steam vent hole is sealed with the plug member according to any one of claims 1 to 5.

7. A method for sealing a steam vent hole of a CFT steel pipe, comprising sealing the steam vent hole of the CFT steel pipe with a plug member according to any one of claims 1 to 5.

8. A method for constructing a CFT column, comprising constructing the CFT column using the CFT steel pipe having the steam vent hole sealed with a plug member according to any one of claims 1 to 5.

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