JP2022150478A - Joint bend prevention fixture and joint bend prevention structure - Google Patents

Abstract

To provide a joint bend prevention fixture capable of preventing a joint from being bent in a simple configuration, and a joint bend prevention structure.SOLUTION: A joint bend prevention fixture 1 comprises: an annular base part 3 fixed on an outer peripheral surface of an insert-side pipe body 2; a diameter enlarged part 4 extending radially outward from the base part 3; and an extension part 5 extending from an outer edge of the diameter enlarged part 4 in a pipe axis direction. In a state where a receive port of a receive-side pipe body 6 bonded with the insert-side pipe body 2 enters an inner diameter side of the extension part 5, the receive-side pipe body abuts on at least one of the diameter enlarged part 4 and the extension part 5, thereby regulating bending angles of joints of the insert-side pipe body 2 and the receive-side pipe body 6. A joint bend prevention structure 15 comprises the insert-side pipe body 2, the receive-side pipe body 6 bonded with the insert-side pipe body 2, and the joint bend prevention fixture 1 fixed on an outer peripheral surface of an insert port of the insert-side pipe body 2.SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint bending prevention fitting for preventing bending of a pipe joint, and a joint bending prevention structure employing the joint bending prevention fitting.

Ductile iron pipes buried underground to transport liquids such as water and sewage, agricultural water, rainwater, and gases such as air are inserted into the socket of the receiving side pipe body. Pipes are formed by joining pipes together. The joints are called joints, and the types of joints include general joints such as mechanical type (K type) and push-on type (T type), and earthquake-resistant joints such as GX type and NS type. Earthquake-resistant joints have separation prevention function and expansion/contraction allowance, and even if earthquake motions or ground changes due to earthquakes occur, the joints can follow the changes. For this reason, it has a high detachment prevention function compared to general joints.

As shown in Figures 8(a) to (d), the main faults associated with earthquakes are normal faults (slip faults) (Figure 8(a)), reverse faults (slip faults) (Figure 8(b) ), left strike-slip fault (Fig. 8(c)), and right strike-slip fault (Fig. 8(d)). As shown in FIG. 9, any fault F causes a load on the joint J of the pipeline N. Especially when the pipeline is arranged in the reverse fault shown in FIG. When displacement occurs as shown in b), forces in the compressive and bending directions act on the joint J near the fault F, causing it to bend greatly, and the bending angle may exceed the allowable value.

Such large bends in joints are most likely to occur on reverse faults (Fig. 8(b)), but they can also occur on strike-slip faults (Figs. 8(c) and 8(d)), etc., depending on the direction in which the pipeline is laid. have a nature. Basically, earthquake-resistant joints can cope with fault displacement, but in some cases it is necessary to supplement the detachment prevention function in preparation for momentary large ground movements. .

Therefore, for example, in the configuration according to Patent Document 1 below, the housing 11 is arranged so as to surround the pipe joint 5, and when the spigot portion 2a is detached from the socket portion 3c, the housing 11 The inner flanges 11b and 11b' formed in the inner flanges 11b and 11b' come into contact with the release restricting member 12 attached to the fluid pipe 2 and the large-diameter portion 3g of the socket portion 3c (hereinafter referred to as configuration A). .). Further, in the other pipe joint 5, the blade portion of the locking member 23 of the earthquake-resistant pipe joint 22 is made to bite into the surface of the fluid pipe 3 to prevent it from coming off (hereinafter referred to as configuration B) (hereinafter referred to as configuration B). See especially paragraphs 0018-0030 of Patent Document 1, FIG. 1).

JP 2016-138637 A

In the configuration A of Patent Document 1, in order to surround the housing 11, the entire periphery of the pipe joint 5 (for example, 2 to 3 meters in the pipe axial direction) is excavated to remove earth and sand down to the ground surface. must be removed at once. Therefore, the excavation work is very complicated and requires work cost. In addition, in the configuration B of Patent Document 1, since the blade portion of the locking member 23 of the earthquake-resistant pipe joint 22 bites into the surface of the fluid pipe 3, there is a problem that when applied to the earthquake-resistant joint, the expansion/contraction action is lost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent bending of a joint with a simple configuration.

In order to solve the above problems, in the present invention,
an annular base fixed to the outer peripheral surface of the insertion-side tubular body;
an enlarged diameter portion extending radially outward from the base;
an extension portion extending in the pipe axis direction from the outer edge of the enlarged diameter portion;
and the receiving port of the receiving-side tubular body joined to the insertion-side tubular body comes into contact with at least one of the enlarged-diameter portion and the extending portion in a state in which it enters the inner diameter side of the extending portion. and a joint bending prevention metal fitting that regulates the bending angle of the joint between the inserting side pipe body and the receiving side pipe body.

In this way, when forces in the compression and bending directions act on the joint, the movement in the compression direction is stopped by the enlarged diameter portion, and the movement in the bending direction is stopped by the extended portion, so that the joint exceeds the predetermined angle. can be prevented from bending. Moreover, since the structure is also very simple, the manufacturing cost of this joint bending prevention metal fitting can be suppressed.

In the above configuration, the surface of the enlarged diameter portion facing the extending direction of the extending portion is formed with an inclined portion that is inclined in a direction opposite to the extending direction of the extending portion toward the radially outer side. It is preferable to set it as the structure which has. In this way, when the receiving side tubular body is inclined by the inclination angle of the inclined portion with respect to the insertion side tubular body, the end surface of the socket of the receiving side tubular body comes into surface contact with the inclined portion. Therefore, the force in the compression direction acting from the receiving side pipe body can be reliably received by the enlarged diameter portion (joint bending prevention metal fitting) and the insertion side pipe body.

In each of the above configurations, it is preferable that an inclined portion that inclines toward the inner diameter side toward the tip of the extension portion is formed on the surface on the inner diameter side of the extension portion. In this way, when the receiving-side tubular body is inclined with respect to the insertion-side tubular body by the inclination angle of the inclined portion, the outer peripheral surface of the socket of the receiving-side tubular body comes into surface contact with the inclined portion. . Therefore, a force in the bending direction acting from the receiving-side tubular body can be received by the wide surface of the extension portion, and damage to the extension portion can be prevented.

In each of the above configurations, at least one of the surface of the enlarged diameter portion facing the extending direction of the extending portion and the surface on the inner diameter side of the extending portion is provided between the receiving port of the receiving side tubular body. It is preferable to have a configuration in which an elastic member intervening between is provided. With this configuration, when the bending angle of the receiving side tube with respect to the insertion side tube does not match the inclination angle of the inclined portion formed on the enlarged diameter portion or the inclination angle of the inclined portion formed on the extension portion. However, since the elastic member is deformed corresponding to the difference in the angles to ensure the surface contact state, it is possible to prevent the enlarged diameter portion and the extension portion from being damaged.

In each of the above configurations, it is preferable that the base is provided with a projection that fits into a recess formed on the outer peripheral surface of the insertion-side tubular body. With this configuration, even if the receiving port of the receiving-side tubular body abuts against the enlarged diameter portion or the extension portion from the axial direction, the joint bending prevention metal fitting is less likely to shift in the axial direction.

In each of the configurations described above, it is preferable to adopt a configuration in which a ring is formed by connecting a plurality of divided pieces divided in the circumferential direction. By doing so, the joint bending prevention metal fitting can be smoothly attached to the existing pipe.

In addition, in order to solve the above problems, in the present invention,
an insertion-side tubular body;
a receiving-side tubular body joined to the insertion-side tubular body;
the joint bending prevention fitting fixed to the outer peripheral surface of the insertion port of the insertion-side tubular body;
and the socket of the receiving side tubular body comes into contact with the joint bending prevention metal fitting in a state of being inserted into the inner diameter side of the extension portion of the joint bending prevention metal fitting, whereby the insertion side pipe body and the insertion side pipe body and the A joint bending prevention structure is configured to regulate the bending angle of the joint of the receiving pipe body.

In this way, the bending prevention effect of the joint bending prevention fitting can prevent the joint between the insertion side pipe and the receiving side pipe from bending beyond a predetermined angle, and a large ground movement will occur instantaneously. In such a case, the detachment prevention function can be reliably exhibited.

In the joint bending prevention structure, the joint has an earthquake-resistant joint structure that allows expansion and contraction in the pipe axial direction between the joined insertion-side tubular body and the receiving-side tubular body, and the joint bending prevention fitting is provided. is fixed to the insertion side tube, the tip of the extension portion is located closer to the insertion side tube in the tube axis direction than the socket tip of the receiving side tube, and the insertion side tube It is preferable that when the body and the receiving side tubular body approach each other, the receiving end of the receiving side tubular body enters the inner diameter side of the extending portion. By doing so, the expansion and contraction function of the earthquake-resistant joint can be maintained, and the anti-bending effect can be reliably exhibited when forces in the compression direction and the bending direction act on the joint. Moreover, when attaching the joint bending prevention metal fitting to the existing pipe, only the vicinity of the insertion opening of the insertion side pipe body needs to be excavated, so that the amount of excavation can be reduced and the construction period can be shortened.

In the present invention, since the above-described joint bending prevention metal fitting is employed, it is possible to prevent the joint from bending beyond a predetermined angle when forces are applied to the joint in the compression direction and the bending direction.

FIG. 1 is a front view showing an embodiment of a joint bending prevention metal fitting according to the present invention; Cross-sectional view along the II-II line in FIG. FIG. 2 is a cross-sectional view of the joint bending prevention metal fitting shown in FIG. 1, where (a) is the first modification and (b) is the second modification BRIEF DESCRIPTION OF THE DRAWINGS Sectional view showing one embodiment of the joint bending prevention structure according to the present invention. FIG. 5 is a cross-sectional view showing a state in which forces in a compression direction and a bending direction act on the joint bending prevention structure shown in FIG. Diagram showing the relationship between joint bending angle and bending moment A diagram showing the calculation results of the bending angle of the joint when forces in the compression direction and the bending direction act on the pipeline. Schematic representation of major fault types: (a) normal fault (strike-slip fault), (b) reverse fault (strike-slip fault), (c) left-lateral strike-slip fault, (d) right-lateral strike-slip fault fault Fig. 3 shows a pipeline installed in a reverse fault, (a) before displacement and (b) after displacement

An embodiment of a joint bending prevention fitting 1 according to the present invention is shown in FIGS. 1 and 2. FIG. This joint bending prevention metal fitting 1 comprises an annular base portion 3 fixed to the outer peripheral surface of an insertion-side tubular body 2, an enlarged diameter portion 4 extending radially outward from the base portion 3, and an enlarged diameter portion 4. and an extension part 5 extending from the outer edge in the pipe axial direction, and the socket of the receiving side pipe body 6 joined to the insertion side pipe body 2 abuts on the joint bending prevention metal fitting 1. , the bending angle of the joint between the insertion-side tubular body 2 and the receiving-side tubular body 6 is regulated.

The base portion 3, the enlarged diameter portion 4, and the extended portion 5 are composed of split pieces that are divided into two pieces in the circumferential direction. By using split pieces in this manner, the joint bending prevention fitting 1 can be smoothly attached to an existing pipe. Moreover, when attaching the joint bending prevention fitting 1 to the existing pipe, only the vicinity of the insertion port of the insertion side pipe body 2 needs to be excavated, so that the amount of excavation can be reduced and the construction period can be shortened. In addition, in the case of a new pipe, the undivided annular joint bending prevention metal fitting 1 can be inserted as it is from the insertion opening of the insertion side pipe body 2 .

The base portion 3 is a strip-shaped member having a width in the pipe axis direction that is wider than that of the enlarged diameter portion 4 . Since the bearing surface facing the insertion-side tubular body 2 is widened by increasing the width in the pipe axial direction in this way, the joint bending prevention metal fitting 1 can be stably fixed to the insertion opening of the insertion-side tubular body 2 . . The inner diameter of the base part 3 is designed so that the insertion-side tubular body 2 is slightly tight-fitted when the bolt/nut 7 is tightened, so that the base part 3 is securely fixed to the insertion opening. be able to.

On the surface of the expanded diameter portion 4 facing the extending direction of the extending portion 5, an inclined portion 8 is inclined in the direction opposite to the extending direction of the extending portion 5 (to the left in FIG. 2) toward the radially outer side. is formed. The inclination angle of the inclined portion 8 is about the permissible bending angle of the receiving side tube 6 with respect to the insertion side tube 2 (for example, about 2 degrees for a large diameter tube and about 4 degrees for a small diameter tube), and , the maximum bending angle or less (for example, about 4 degrees for large-diameter pipes, and about 8 degrees for small-diameter pipes). The surface opposite to the surface on which the inclined portion 8 is formed stands substantially perpendicular to the tube axis direction. Although the length in the radial direction of the expanded diameter portion 4 is not particularly limited, a gap between the outer peripheral surface of the insertion side tubular body 2 to which the joint bending prevention metal fitting 1 is attached and the extended portion 5 is filled with the insertion side tubular body. The length is such that the socket of the receiving-side tubular body 6 joined to 2 can smoothly enter.

The inner diameter side and outer diameter side surfaces of the extended portion 5 are surfaces extending in parallel along the pipe axial direction in the circumferential cross section thereof, but the inner diameter side surface has an extended portion An inclined portion 9 is formed which is inclined toward the inner diameter side toward the tip of 5 . Similar to the inclined portion 8 formed in the enlarged diameter portion 4, the inclination angle of the inclined portion 9 is about the allowable bending angle of the receiving side tubular body 6 with respect to the insertion side tubular body 2 (for example, 2 in the case of a large diameter tube). about 4 degrees for small-diameter pipes) and below the maximum bending angle (for example, about 4 degrees for large-diameter pipes and about 8 degrees for small-diameter pipes). The length of the extending portion 5 in the direction of the tube axis is not particularly limited, but is set to such a length that the socket of the receiving-side tubular body 6 bent with respect to the insertion-side tubular body 2 does not come off the extending portion 5 . (see Figure 5).

In this embodiment, the inclined portions 8 and 9 are formed on both the enlarged diameter portion 4 and the extended portion 5, but the configuration may be such that only one of the enlarged diameter portion 4 or the extended portion 5 is formed. can also Also, a configuration in which the inclined portions 8 and 9 are not formed is also possible.

An elastic member 10 is provided between the surface of the expanded diameter portion 4 facing the extension side of the extension portion 5 and the inner diameter side surface of the extension portion 5 and the socket of the receiving-side tubular body 6 . It is By providing the elastic member 10, the inclination angle of the receiving-side tubular body 6 with respect to the insertion-side tubular body 2 is adjusted to the inclination angle of the inclined portion 8 formed in the enlarged diameter portion 4 and the inclination formed in the extension portion 5. Even when the inclination angle does not match the inclination angle of the portion 9, the elastic member 10 is deformed corresponding to the difference in the angle to ensure a state close to surface contact, thereby preventing the enlarged diameter portion 4 and the extension portion 5 from being damaged. can do.

In this embodiment, the elastic member 10 is provided on both the enlarged diameter portion 4 and the extension portion 5, but it may be provided on either the enlarged diameter portion 4 or the extension portion 5 only. . Alternatively, a configuration in which the elastic member 10 is not provided is also possible. Further, the shape, such as the thickness, and the material of the elastic member 10 can be appropriately changed according to the nominal diameter of the target pipe and the joint type.

As shown in FIG. 3(a), this joint bending prevention metal fitting 1 has a protrusion 12 formed on the inner diameter surface of the base 3 to fit into a recess 11 formed on the outer peripheral surface of the insertion port of the insertion side pipe body 2. can also be configured. In this way, even if the socket of the receiving-side tubular body 6 comes into contact with the enlarged diameter portion 4 or the extended portion 5 from the axial direction, the joint bending prevention metal fitting 1 is less likely to slip in the axial direction. Further, as shown in FIG. 3B, a rib 13 bridging the base portion 3 and the enlarged diameter portion 4 and a rib 14 bridging the enlarged diameter portion 4 and the extension portion 5 may be formed. By doing so, the strength of the joint bending prevention metal fitting 1 can be improved, and deformation and breakage when a large external force acts can be prevented.

FIG. 4 shows an embodiment of a joint bending prevention structure 15 according to the present invention. The joint bending prevention structure 15 includes the insertion side tubular body 2 , the receiving side tubular body 6 joined to the insertion side tubular body 2 , and the above joint bending structure fixed to the outer peripheral surface of the insertion port of the insertion side tubular body 2 . The socket of the receiving-side tubular body 6 is inserted into the inner diameter side of the extended portion 5 of the joint bending prevention metal fitting 1, and the joint bending prevention metal fitting 1 abuts against it. , the bending angle of the joint between the insertion-side tubular body 2 and the receiving-side tubular body 6 is regulated. The joint shown in this embodiment has an earthquake-resistant joint structure that permits expansion and contraction in the pipe axial direction between the insertion-side tubular body 2 and the receiving-side tubular body 6 that are joined together.

On the outer diameter side of the tip of the insertion opening of the insertion-side tubular body 2, there is formed a locking projection 16 having an inclined surface whose diameter decreases toward the tip side and a wall surface that rises in the radial direction on the rear end side. ing.

A lock ring 17 is provided on the inner surface of the socket of the receiving-side tubular body 6 . The lock ring 17 is an annular member having a notch formed in a part of its circumference. The lock ring 17 once expands in diameter by abutting against the inclined surface of the locking projection 16 when the insertion side pipe body 2 and the receiving side pipe body 6 are joined together, and passes through the locking projection 16 . After passing through it, the diameter is reduced again, and when a pull-out force acts, it comes into contact with the wall surface of the locking projection 16 to exert a retaining action. A water stop member 18 is provided on the socket tip side of the lock ring 17 . This water stop member 18 is a member made of an annular rubber material, and is interposed between the inserting side tubular body 2 and the receiving side tubular body 6 to exert a water stopping action.

Since the joint bending prevention fitting 1 is the same as that shown in FIG. 2, detailed description thereof will be omitted. As for the fixing position of the joint bending prevention metal fitting 1 to the outer peripheral surface of the insertion port, the tip of the extended portion 5 is closer to the insertion side tubular body 2 in the tube axial direction than the socket tip of the receiving side tubular body 6. Positioning is performed so that the receiving end of the receiving side tubular body 6 enters the inner diameter side of the extending portion 5 by bringing the insertion side tubular body 2 and the receiving side tubular body 6 closer to each other. By doing so, the expansion and contraction function of the earthquake-resistant joint can be maintained, and the anti-bending effect can be reliably exhibited when forces in the compression direction and the bending direction act on the joint. In addition, since only the vicinity of the insertion opening of the insertion-side tubular body 2 to which the joint bending prevention fitting 1 is attached needs to be excavated, the amount of excavation can be reduced and the construction period can be shortened.

For example, when a reverse fault on which a pipeline is installed is displaced (see FIG. 9(a)), the joint is bent as shown in FIG. There is At this time, on the inner side of the bend of the joint, the end surface of the socket contacts the inclined portion 8 of the expanded diameter portion 4 via the elastic member 10, while on the outer side of the bend, the outer peripheral surface of the socket contacts the elastic member 10. It abuts on the inclined portion 9 of the extended portion. When the bending angle of the joint is close to the angle of inclination of each inclined portion 8, 9, the end face and the outer peripheral surface of the socket and each inclined portion 8, 9 are in a substantially surface contact state.

Numerical analysis was performed on bending behavior of joints with and without the joint bending prevention fitting 1 according to the present invention. Table 1 shows the pipeline, ground, and fault conditions used in this numerical analysis. Table 2 shows the length of the pipe used and the state of attachment of the joint bending prevention fitting 1 according to the present application. In the model used for this numerical analysis, when the bending angle of the joint is 6 degrees (the absolute value is shown; the same shall apply hereinafter), as shown in FIG. , the joint bending prevention fitting 1 and the socket are assumed to be in contact with each other. In all cases shown in Table 2, fault F and pipeline N intersect at the center of one pipe (see FIGS. 9(a) and 9(b)).

Among the joint spring characteristics expressing the behavior of the joint, the characteristics in the rotational direction are shown in FIG. In a GX-type ductile iron pipe with a nominal diameter of Φ300, when the joint is bent more than 6 degrees, the insertion port and the socket come into direct contact and a large bending moment is generated. When the joint bending prevention metal fitting 1 according to the present application is not attached (see the dashed line graph in FIG. 6), the bending moment increases as the bending angle of the joint increases. If this bending angle exceeds the allowable range of the maximum bending angle, for example, 8 degrees, the possibility of water leakage from the joint increases.

On the other hand, when the joint bending prevention fitting 1 according to the present application was attached (see the solid line graph in FIG. 6), the bending moment increased sharply as the joint bending angle increased. It is considered that this is because the bending of the joint is suppressed by the rigidity of the joint bending prevention metal fitting 1 . As a result, the bending angle is less likely to exceed the allowable range of 8 degrees, and problems such as water leakage from the joint are less likely to occur.

Fig. 7 shows the calculation results of the joint bending angle. In the case of a fixed-length 6m pipe (Comparative Example 1), the inclination accompanying the displacement of the fault concentrates on the central pipe at the fault position, and the joints at both ends of this central pipe (indicated by "o" in Fig. 7). A large bending angle occurs at (maximum value of 17.4 degrees). For this reason, the allowable range of the bending angle is greatly exceeded, and problems such as water leakage from the joint may occur. In addition, if the pipe length is shortened and a 2 m pipe is adopted (Comparative Example 2), the central pipe at the fault position and the pipes on both sides of it tend to tilt, so the bending angle at the joints on both sides of this central pipe is a little. Although it is smaller (maximum value of 11.1 degrees), it still exceeds the allowable range of bending angles.

On the other hand, when the joint bending prevention fitting 1 according to the present application is attached to the insertion port of the insertion side pipe body 2 of the 2m pipe (Example), the pipes next to the pipes on both sides of the central pipe at the fault position Since it becomes easier to tilt, the maximum value of the tilt angle can be suppressed within the allowable range (maximum value of 7 degrees). Therefore, problems such as water leakage caused by bending of the joint can be suppressed.

The embodiments disclosed this time are illustrative in all respects and should be considered not restrictive. Therefore, the scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include meanings equivalent to the scope of the claims and all modifications.

1 Joint Bending Prevention Metal Fitting 2 Insert Side Pipe 3 Base Part 4 Expanded Diameter Part 5 Extension Part 6 Receiving Side Pipe 7 Bolts and Nuts 8, 9 Inclined Part 10 Elastic Member 11 Recess 12 Projections 13, 14 Rib 15 Joint Bending Prevention Structure 16 locking projection 17 lock ring 18 water stop member

Claims (8)

an annular base (3) fixed to the outer peripheral surface of the insertion side tubular body (2);
an enlarged diameter portion (4) extending radially outward from the base portion (3);
an extended portion (5) extending in the pipe axial direction from the outer edge of the enlarged diameter portion (4);
and the enlarged diameter portion (4) and A joint bending prevention metal fitting that abuts against at least one of the extension portions (5) to regulate the bending angle of the joint between the insertion side pipe body (2) and the receiving side pipe body (6). An inclined portion inclined in a direction opposite to the extending direction of the extending portion (5) toward the radially outer side on the surface of the enlarged diameter portion (4) facing the extending direction of the extending portion (5). 2. The joint bending prevention metal fitting according to claim 1, wherein (8) is formed. 3. The joint according to claim 1 or 2, wherein an inclined portion (9) is formed on the inner diameter side surface of the extension portion (5), the inclined portion (9) being inclined toward the inner diameter side toward the tip of the extension portion (5). Bending prevention metal fittings. At least one of the surface of the enlarged diameter portion (4) facing the extension direction of the extension portion (5) or the inner diameter side surface of the extension portion (5) is provided with the receiving side tubular body (6). 4. The joint bending prevention metal fitting according to any one of claims 1 to 3, further comprising an elastic member (10) interposed between the socket of the joint. 5. According to any one of claims 1 to 4, wherein the base portion (3) is formed with a protrusion (12) that fits into a recess (11) formed on the outer peripheral surface of the insertion-side tubular body (2). Joint bending prevention metal fittings described. 6. The joint bending prevention metal fitting according to any one of claims 1 to 5, wherein the ring is formed by connecting a plurality of divided pieces divided in the circumferential direction. an insertion side tubular body (2);
a receiving side tubular body (6) joined to the insertion side tubular body (2);
The joint bending prevention fitting (1) according to any one of claims 1 to 6, which is fixed to the outer peripheral surface of the insertion port of the insertion side pipe body (2);
and the socket of the receiving-side tubular body (6) is inserted into the inner diameter side of the extended portion (5) of the joint bending prevention metal fitting (1) and the joint bending prevention metal fitting (1). A joint bending prevention structure that regulates the bending angle of the joint between the insertion side tubular body (2) and the receiving side tubular body (6) by abutting against each other. The joint has an earthquake-resistant joint structure that allows expansion and contraction in the direction of the pipe axis between the insertion side pipe body (2) and the receiving side pipe body (6) that are joined, and the joint bending prevention metal fitting (1) ) is fixed to the insertion-side tubular body (2), the tip of the extension part (5) is positioned further along the tube axis than the socket tip of the receiving-side tubular body (6). (2) side, and when the insertion-side tubular body (2) and the receiving-side tubular body (6) approach each other, the socket tip of the receiving-side tubular body (6) is extended. 8. The joint bending prevention structure according to claim 7, wherein the joint bending prevention structure is constructed so as to enter into the inner diameter side of the portion (5).

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