JP2018165470A - Connection structure of steel pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize prior work on steel pipes when connecting the steel pipes using mechanical fittings.SOLUTION: A connection structure 10 of steel pipes includes a first member 11 inserted into a steel pipe and a second member 12 inserted into the first member 11. The first member 11 has a friction surface 111 formed on an outer periphery and a pressed surface 112 formed on an inner periphery. The second member 12 has a pressing surface 122 formed on an outer periphery and expanding the outer diameter of the first member 11 beyond the inner diameter of the steel pipe by pressing the pressed surface 112.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steel pipe connection structure.

  Steel pipes have a variety of uses, one of which is a use as a structural member of a building or a civil engineering structure. For example, when a long structural member such as a pile is composed of a steel pipe, construction in a limited space becomes possible by connecting the short steel pipe in the field to make a long structural member. It is also easy to transport the steel pipe up to. For example, in the case of a small-diameter steel pipe having a diameter of about 50 mm to 200 mm, if it is short, it can be handled manually.

  In such a case, one of the most common methods for connecting steel pipes is welding. However, the welding process is relatively time consuming and requires a skilled welder. Therefore, the process of welding a short steel pipe on site to make a long structural member tends to be a construction bottleneck in terms of construction period and personnel planning. Therefore, various steel pipe connection structures using mechanical joints that do not require an on-site welding process have been proposed.

  For example, Patent Document 1 describes a technique of mechanically connecting steel pipes by fitting a pair of connecting members welded to end faces of the respective steel pipes to each other. In this case, since the steel pipe and the connecting member can be welded at a factory, no on-site welding process is required. Patent Document 2 describes a technique of mechanically connecting steel pipes by engaging a connecting member from the outside with a flange formed at an end of each steel pipe.

Japanese Patent Laying-Open No. 2015-143466 Japanese Patent Laying-Open No. 2015-132106

  The conventional steel pipe connection structure as described above is advantageous in that it does not require an on-site welding process. However, it can be said that there is still room for improvement in the conventional connection structure of steel pipes in that the steel pipe needs to be processed in advance. If the pre-processing on the steel pipe can be reduced or eliminated, not only the whole process including the factory process is simplified, but also it is advantageous in that the connection structure can be applied in a wider range.

  Accordingly, an object of the present invention is to provide a new and improved steel pipe connection structure capable of minimizing the prior processing of a steel pipe when connecting the steel pipe using a mechanical joint. To do.

［１０］第１部材の外径が鋼管の内径を超えて拡張されるときの鋼管の拡径量δが、鋼管の外径Ｄ、鋼管のヤング率Ｅ、および鋼管の降伏強度σ_ｙを用いて下記の式（ｉｉ）によって表される範囲にある、［１］〜［９］のいずれか１項に記載の鋼管の連結構造。

［１１］第１部材の外径が鋼管の内径を超えて拡張されるときの鋼管の拡径量δが、鋼管の外径Ｄおよび鋼管の一様伸びＡ_Ｕ（％）を用いた下記の式（ｉｉｉ）、または鋼管の外径Ｄおよび鋼管の破断時全伸びＡ_Ｄ（％）を用いた下記の式（ｉｖ）によって表される範囲にある、［１］〜［９］のいずれか１項に記載の鋼管の連結構造。

According to some aspects of the invention, the following is provided.
[1] A first member inserted inside the steel pipe, and a second member inserted inside the first member,
The first member has a friction surface formed on the outer periphery and a pressed surface formed on the inner periphery,
The second member has a pressing surface that is formed on the outer periphery and has a pressing surface that extends the outer diameter of the first member beyond the inner diameter of the steel pipe by pressing the pressed surface.
[2] The steel pipe connection structure according to [1], wherein the first member is divided into a plurality of portions in the circumferential direction, and a gap is provided between the plurality of portions.
[3] The steel pipe connection structure according to [1] or [2], wherein the pressing surface and the pressed surface are tapered surfaces having shapes corresponding to each other.
[4] The steel pipe connection structure according to any one of [1] to [3], wherein thread shapes corresponding to each other are formed on an inner periphery of the first member and an outer periphery of the second member.
[5] The steel pipe connection structure according to any one of [1] to [4], wherein an adhesive layer is formed between the pressing surface and the pressed surface.
[6] The steel pipe connection structure according to any one of [1] to [5], wherein the friction surface or the inner peripheral surface of the steel pipe is roughened.
[7] The steel pipe connection structure according to [6], wherein the friction surface or the inner peripheral surface of the steel pipe is blasted or metal sprayed.
[8] The steel pipe connection structure according to any one of [1] to [7], wherein the first member has a flange rising outward from one end of the friction surface.
[9] The diameter δ of the steel pipe when the outer diameter of the first member is expanded beyond the inner diameter of the steel pipe is the outer diameter D of the steel pipe, the Young's modulus E of the steel pipe, the yield strength σ _{y of the} steel pipe, the friction surface Is expressed by the following equation (i) using the coefficient of static friction μ between the pipe and the inner peripheral surface of the steel pipe, the length L of the friction surface in the axial direction of the steel pipe, and the coefficient α (0 <α ≦ 1). The connection structure of steel pipes according to any one of [1] to [8], which is in a range.

[10] Using the outer diameter D of the steel pipe, the Young's modulus E of the steel pipe, and the yield strength σ _y of the steel pipe when the outer diameter of the first member is expanded beyond the inner diameter of the steel pipe. The connection structure of steel pipes according to any one of [1] to [9], in a range represented by the following formula (ii):

[11] The amount of expansion δ of the steel pipe when the outer diameter of the first member is expanded beyond the inner diameter of the steel pipe is the following using the outer diameter D of the steel pipe and the uniform elongation A _U (%) of the steel pipe: Any one of [1] to [9], which is in the range represented by the following formula (iv) using the formula (iii) or the outer diameter D of the steel pipe and the total elongation A _D (%) at break of the steel pipe The steel pipe connection structure according to Item 1.

  ADVANTAGE OF THE INVENTION According to this invention, when connecting a steel pipe using a mechanical coupling, the prior process with respect to a steel pipe can be suppressed to the minimum.

It is a schematic perspective view which shows the member of the connection structure which concerns on 1st Embodiment of this invention. It is a figure which shows the connection process of the steel pipe by the connection structure shown by FIG. It is a figure for demonstrating the force which acts on the connection structure shown by FIG. It is a schematic sectional drawing which shows the modification of 1st Embodiment of this invention. It is a schematic perspective view which shows the member of the connection structure which concerns on 2nd Embodiment of this invention. It is a schematic perspective view which shows the member of the connection structure which concerns on 3rd Embodiment of this invention. It is a rough sectional view showing the connection structure concerning a 4th embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 is a schematic perspective view showing members of a connection structure according to the first embodiment of the present invention. The connecting structure 10 shown in FIG. 1 includes a first member 11 (illustrated as portions 11a, 11b, and 11c) inserted inside the steel pipe and a second member 12 inserted inside the first member 11. Including.

  The first member 11 has a friction surface 111 formed on the outer periphery and a tapered surface 112 formed on the inner periphery. Here, the taper surface means a surface in which the diameter of the member (the inner diameter in the first member 11 and the outer diameter in the second member 12) continuously changes in the tube axis direction of the steel pipe to be connected. The friction surface 111 has a shape corresponding to the inner peripheral surface of the steel pipe, and contacts the inner peripheral surface of the steel pipe when the first member 11 is inserted inside the steel pipe. As will be described later, the friction surface 111 may be subjected to a surface treatment for increasing the frictional force. The tapered surface 112 is a pressed surface that is pressed by the tapered surface 122 of the second member 12. In the illustrated example, in order to ensure the length of the friction surface 111 in the tube axis direction (that is, the axial direction of the steel pipe), a straight surface 113 is formed on the inner periphery continuously to the tapered surface 112. Yes. Here, the straight surface means a surface in which the diameter of the member (inner diameter in the first member 11) is constant in the tube axis direction of the steel pipe to be connected. Further, the first member 11 has a flange 114 that rises outward from one end of the friction surface 111. On the other hand, the second member 12 has a rod shape or a cylindrical shape as a whole, but a tapered surface 122 is formed on the outer periphery. The tapered surface 122 is a pressing surface that presses the tapered surface 112 of the first member 11. The tapered surfaces 112 and 122 have shapes corresponding to each other.

  Here, although the 1st member 11 is a cylindrical shape as a whole, it is divided | segmented into several parts about the circumferential direction, specifically, three parts 11a-11c, and between each of parts 11a-11c, it is predetermined. A gap is provided. With this structure, the outer diameter of the first member 11 can be expanded and contracted. When the second member 12 is inserted inside the first member 11, the tapered surface 122 of the second member 12 presses the tapered surface 112 of the first member 11, so that the gap is widened. The outer diameter of the is expanded. At this time, the outer diameter of the first member 11 before expansion is equal to or smaller than the inner diameter of the steel pipe. Further, the outer diameter of the first member 11 after expansion is larger than the inner diameter of the steel pipe. As a result, as described later, when the second member 12 is inserted inside the first member 11, a large frictional force is applied between the friction surface 111 of the first member 11 and the inner peripheral surface of the steel pipe. be able to.

  In the present embodiment, the state in which the outer diameter of the first member 11 is expanded by the tapered surface 122 of the second member 12 pressing the tapered surface 112 of the first member 11 is the tapered surface 112 and the tapered surface 122. It is maintained by forming an adhesive layer (not shown) between them. The adhesive layer is formed, for example, by applying an adhesive to one or both of the tapered surfaces 112 and 122.

  2 (A) to 2 (C) are diagrams showing a steel pipe connecting step by the connecting structure shown in FIG. In the illustrated example, the pair of first members 11 (parts 11a to 11c and parts 11d to 11f. However, since the part 11c and the part 11f are not shown, the parts 11a and 11b and the parts 11d and 11e are respectively shown below. And a pair of steel pipes 2 (steel pipe 2a and steel pipe 2b) are connected using the second member 12 (having tapered surfaces 122a and 122b formed in opposite directions).

  First, as shown to FIG. 2 (A), the 1st member 11 (part 11a, 11b) is inserted inside the steel pipe 2a. At this time, the outer diameter of the first member 11 (parts 11a and 11b) is equal to or smaller than the inner diameter d of the steel pipe 2a as shown in the figure. Therefore, it is easy to insert the 1st member 11 (part 11a, 11b) inside the steel pipe 2a. When the flange 114 abuts against the end surface 2e of the steel pipe 2a, the position of the first member 11 (parts 11a and 11b) in the pipe axis direction is fixed.

  Next, as shown in FIG. 2B, the second member 12 is inserted inside the first member 11 (parts 11a and 11b). At this time, the tapered surface 122a of the second member 12 presses the tapered surface 112 of the first member 11 (parts 11a and 11b), whereby the outer diameter of the first member 11 (parts 11a and 11b) is expanded. In the illustrated example, the outer diameter of the first member 11 (parts 11a and 11b) extends beyond the inner diameter d of the steel pipe 2a to d + δ until the second member 12 is inserted to a predetermined depth dp. Is done. In addition, δ is the diameter expansion amount of the steel pipe 2a. As a result, a large frictional force acts between the friction surface 111 of the first member 11 (parts 11a and 11b) and the inner peripheral surface 2s of the steel pipe 2a, and the first member 11 (parts 11a and 11b) It is fixed to the steel pipe 2a.

  Further, as shown in FIG. 2 (C), the first member 11 (parts 11d and 11e) is also inserted inside the other steel pipe 2b, and the second member 12 is inserted inside thereof. Similarly to the process shown in FIG. 2B, the tapered surface 122b of the second member 12 presses the tapered surface 112 of the first member 11 (parts 11d and 11e), thereby the first member 11 (parts 11d and 11d). The outer diameter of 11e) is expanded beyond the inner diameter d of the steel pipe 2b. As a result, a large frictional force acts between the friction surface 111 of the first member 11 (parts 11d and 11e) and the inner peripheral surface 2s of the steel pipe 2b, and the first member 11 (parts 11d and 11e) It is fixed to the steel pipe 2b.

  In the illustrated example, the outer diameter of the first member 11 inserted inside the steel pipes 2a and 2b is expanded beyond the inner diameter d of the steel pipes 2a and 2b. Thus, a large frictional force is applied between the friction surface 111 of the first member 11 and the inner peripheral surface 2s of the steel pipes 2a and 2b, and the first member 11 can be fixed to the steel pipes 2a and 2b. Further, a common second member 12 is inserted inside both the first members 11, and the first member 11 and the second member 12 are fixed by an adhesive layer. Thus, the connection structure 10 which concerns on this embodiment connects the steel pipe 2a and the steel pipe 2b.

(First design example)
FIG. 3 is a diagram for explaining the force acting on the connection structure shown in FIG. 1. In FIG. 3, the surface pressure P acting from the inner peripheral surface 2 s of the steel pipe 2 toward the friction surface 111 of the first member 11 and the axial friction force of the steel pipe 2 generated along with the surface pressure P (maximum static Friction force F) is shown. FIG. 3 also shows the inner diameter d, outer diameter D, and wall thickness t of the steel pipe 2 and the length L of the friction surface 111 of the first member 11 in the axial direction of the steel pipe 2. In the following description, it is assumed that the wall thickness t does not change even when the diameter of the steel pipe 2 is increased. In this case, the same expanded amount δ is generated in the inner diameter d and the outer diameter D of the steel pipe 2. In FIG. 3 and FIG. 4 to be described later, it is shown that the diameter expansion amount δ / 2 is uniformly generated on both sides of the steel pipe 2, but if the diameter expansion amount δ is generated on both sides, The above explanation is valid, and it is not always necessary to generate an equal amount of diameter expansion on both sides. Below, the 1st design example of the connection structure on condition of this diameter expansion amount (delta) is demonstrated.

  As already described, in the present embodiment, the outer diameter of the first member 11 inserted inside the steel pipe 2 exceeds the inner diameter d of the steel pipe 2 and is expanded to d + δ. If the diameter expansion amount δ at this time is within an appropriate range, the steel pipe 2 is elastically deformed. At this time, the surface pressure P acts between the friction surface 111 of the first member 11 pressed by the second member 12 and the inner peripheral surface of the steel pipe 2. The maximum static frictional force F generated with the surface pressure P is the static friction coefficient μ between the friction surface 111 of the first member 11 and the inner peripheral surface 2s of the steel pipe 2, the surface pressure P, and the friction surface 111 and the inner surface. It is the product of the contact area with the peripheral surface 2s, and is expressed as in equation (1). Note that the static friction coefficient μ can be measured, for example, according to a friction coefficient measurement method defined in JIS K7125.

  From the above equation (1), it can be seen that the maximum static friction force F increases in proportion to the static friction coefficient μ, the surface pressure P, and the length L of the friction surface 111. Of these, in order to increase the value of the static friction coefficient μ, either or both of the friction surface 111 and the inner peripheral surface 2s may be roughened. Specifically, the surface roughening can be realized by surface treatment such as blast treatment or metal spray treatment of aluminum or zinc. Alternatively, when the first member 11 or the steel pipe 2 is manufactured by casting, the value of the static friction coefficient μ is increased by leaving a rough surface of the casting surface on one or both of the friction surface 111 and the inner peripheral surface 2s. May be.

  On the other hand, the surface pressure P can be expressed as a function of the diameter expansion amount δ. Assuming that the thickness t of the steel pipe 2 is sufficiently small with respect to the outer diameter D, Equation (2) is established for the surface pressure P, where σ is the stress in the circumferential direction of the steel pipe.

Here, when the amount of expansion is δ with respect to the outer diameter D of the steel pipe, the circumferential strain ε _c can be expressed as in Equation (3) from the change in the circumferential length of the steel pipe before and after the expansion.

On the other hand, as long as the steel pipe does not yield, the circumferential strain ε _c can be expressed as shown in Equation (4) from the relationship with the Young's modulus.

From the above equations (3) and (4), the relationship of equation (5) is established.

  From the above formulas (2) and (5), the surface pressure P can be expressed as a formula (6) as a function of the diameter expansion amount δ. Further, when Expression (6) is substituted into the above Expression (1), Expression (7) is obtained. In addition, in the expression after the expression (7), since the wall thickness t of the steel pipe 2 is sufficiently small with respect to the outer diameter D, an approximation is used in which a quadratic term of the wall thickness t is discarded.

Next, a condition to be satisfied by the maximum static friction force F calculated as described above is examined. First, the total strength of the steel pipe 2 with respect to the axial tension, that is, the condition that the connected structure is maintained until the steel pipe 2 itself yields due to the axial tensile load. In this case, the maximum tensile load F _max to be countered by the maximum static frictional force F is a tensile load when a stress equal to the yield strength σ _y of the steel pipe 2 acts in the axial direction of the steel pipe 2. This is obtained by multiplying the yield strength σ _y by the cross-sectional area of the steel pipe 2 and is expressed by the equation (8). In addition, when the material standard of the steel pipe 2 is known, the yield strength σ _y can be specified as the standard minimum yield strength (SMYS). When the material standard of the steel pipe 2 is not known, or when SMYS is not stipulated in the material standard, the yield strength of the steel pipe 2 measured by, for example, a metal tensile test method specified in JIS Z2241 may be used. it can.

From the above formulas (7) and (8), the condition that the maximum static friction force F can counter the maximum tensile load F _max (F ≧ F _max ) is expressed as in formula (9). When formula (9) is arranged with respect to the diameter expansion amount δ, formula (10) is obtained.

Here, although the above formula (10) is based on the condition of the total strength against tension, it is often required to design economically with a smaller, minimum necessary tensile strength. In such a case, assuming that the required tensile strength is expressed by ασ _y (0 <α ≦ 1) with respect to the yield strength σ _{y of the} steel pipe 2, the above formula (10) is changed to the formula (11). Can be rewritten as:

  The above equation (11) defines the condition for the connection structure 10 according to the present embodiment to maintain the connection against the axial tension of the steel pipe 2. In other words, when the second member 12 of the connection structure 10 is inserted inside the first member 11, if the diameter expansion amount δ of the steel pipe 2 is within the range represented by the above formula (11), the connection structure 10 Can resist the tensile of the steel pipe 2 in the axial direction.

  On the other hand, as described above, the connecting structure 10 according to the present embodiment is designed on the assumption that the diameter expansion amount δ is smaller than the inner diameter d and the outer diameter D of the steel pipe 2 and the steel pipe 2 is elastically deformed. Yes. That is, when the diameter expansion amount δ is too large and the steel pipe 2 yields in the circumferential direction and undergoes plastic deformation, the surface pressure P is rather small, and it is difficult to maintain the connection. Therefore, in addition to defining the lower limit value of the diameter expansion amount δ by the above equation (11), it is useful to define the upper limit value of the diameter expansion amount δ so that the steel pipe 2 does not yield in the circumferential direction.

The relationship between the stress σ acting in the circumferential direction of the steel pipe 2 (approximate that it is equal to the stress acting in the radial direction) and the surface pressure P has already been shown by the above equation (2). Here, the stress σ immediately before the steel pipe 2 yields in the circumferential direction is considered to be equal to the yield strength σ _y of the steel pipe 2. Therefore, the surface pressure P _max immediately before the steel pipe 2 yields in the circumferential direction is expressed as in Expression (12) by replacing the stress σ in Expression (2).

From the above equations (6) and (12), the condition that the steel pipe 2 does not yield in the circumferential direction (P ≦ P _max ) is expressed as equation (13). When formula (13) is arranged with respect to the diameter expansion amount δ, formula (14) is obtained.

  The above equation (14) defines the conditions for the connecting structure 10 according to the present embodiment to prevent the steel pipe 2 from yielding in the circumferential direction. That is, when the second member 12 of the connection structure 10 is inserted inside the first member 11, if the diameter expansion amount δ of the steel pipe 2 is within the range represented by the above formula (14), the steel pipe 2 is It is elastically deformed and surface pressure P and frictional force as expected are applied.

Table 1 shows a first design example of the connecting structure 10 based on the above examination. In the following example, the above-described static friction coefficient μ, long for a steel pipe 2 having an outer diameter D of 114.3 mm (nominal diameter 100 A) and a Young's modulus E of 205.8 GPa (205.8 × 10 ³ N / mm ² ). The connecting structure 10 is designed using the thickness L, the coefficient α, and the yield strength σ _y as variables. Each design is evaluated by the range of the diameter expansion amount δ satisfying the above formulas (11) and (14). In the table, δ _min indicates a lower limit value of the diameter expansion amount δ calculated by the equation (11), and δ _max indicates an upper limit value of the diameter expansion amount δ calculated by the equation (14). A wider permissible range (δ _max −δ _min ) of the diameter expansion amount δ is advantageous in that, for example, an error in member processing or construction can be permitted.

In Examples 1 to 4, a normal steel pipe 2 having a yield strength σ _y of 235 N / mm ² is used. In Example 1, the inner circumferential surface 2s of the steel pipe 2 and the friction surface 111 of the first member 11 are not roughened (static friction coefficient μ = 0.3), and the length L is twice the outer diameter D ( 228.6 mm) and the total strength against tension (α = 1) was the condition. In this case, although design is possible, the allowable range (δ _max −δ _min ) of the diameter expansion amount δ is narrow (0.022 mm), and errors in member processing and construction are hardly allowed.

In contrast, in Example 2, the length L was stretched to 3 times the outer diameter D (342.9 mm). As a result, the maximum static frictional force F generated with respect to the same diameter expansion amount δ increases, and the lower limit value δ _min of the diameter expansion amount δ decreases. As a result, the allowable range (δ _max −δ _min ) of the diameter expansion amount δ. Expanded to nearly three times that of Example 1 (0.058 mm).

In Example 3, the static friction coefficient μ was increased from 0.3 to 0.7 by roughening while the length L remained twice as large as the outer diameter D (228.6 mm). As a result, as in Example 2, the maximum static frictional force F increases and the lower limit value δ _min of the diameter expansion amount δ decreases. As a result, the allowable range (δ _max −δ _min ) of the diameter expansion amount δ increases. It was enlarged to nearly 4 times (0.084 mm).

When the coefficient of static friction μ is 0.7, as shown in Example 4, even if the length L is shortened to 1.5 times the outer diameter D (171.5 mm), the allowable range of the diameter expansion amount δ. (Δ _max −δ _min ) is 3 times or more (0.068 mm) as compared with Example 1. From this, it can be seen that an increase in the static friction coefficient μ is highly effective for increasing the degree of freedom in design.

In Example 5, the length L and the coefficient of static friction μ were the same as in Example 1, but the total strength against tension was not required, and 75% of the tensile strength could be used (α = 0.75). As a result, the lower limit value δ _min of the diameter expansion amount δ was reduced, and as a result, the allowable range (δ _max −δ _min ) of the diameter expansion amount δ was expanded more than twice (0.049 mm) compared to Example 1.

On the other hand, in Example 6, as a result of increasing the strength of the steel pipe 2, the yield strength σ _y is 315 N / mm ² . As a result, the upper limit value δ _max of the diameter expansion amount δ increases, but the lower limit value δ _min also increases, so that the allowable range (δ _max −δ _min ) of the diameter expansion amount δ is as narrow as in Example 1 ( 0.029 mm). Based on this, in Example 7, the value of the coefficient α was adjusted (α = 0.75) so that the required tensile strength was approximately the same as in the case where the steel pipe 2 was not strengthened (Example 1). As a result, the lower limit δ _min was maintained at the same level as in Example 1, and the allowable range (δ _max −δ _min ) of the diameter expansion amount δ could be expanded (0.066 mm).

  As in the above example, by designing in consideration of the diameter expansion amount δ of the steel pipe 2, a connection structure that maintains the connection against the axial tension of the steel pipe 2 and does not yield the steel pipe 2 in the circumferential direction. 10 can be realized while allowing an error in member processing and construction as much as possible.

(Second design example)
Below, the 2nd design example of the connection structure 10 on condition of the diameter expansion amount (delta) shown by FIG. 3 is demonstrated. In the first design example described above, the condition of the diameter expansion amount δ is determined on the condition that the steel pipe 2 does not yield in the circumferential direction, that is, the diameter is expanded within the range of elastic deformation. In addition, even if the metal material is deformed beyond the range of elastic deformation, it does not break immediately, and even in the range of plastic deformation, the metal material is uniformly deformed to some extent. That is, even when the steel pipe 2 is plastically deformed, the contact pressure P and the frictional force are generated as in the elastic deformation range until the deformation amount reaches a certain level, and the connection structure 10 can be maintained. However, when plastic deformation further proceeds, non-uniform plastic deformation, specifically, deformation in which a part of the circumferential direction of the steel pipe 2 is constricted occurs, and in addition to the possibility of breakage, the first member 11 is increased. As a result, the contact area is reduced, which makes it difficult to maintain the connection structure. In the second design example, the allowable range of the diameter expansion amount δ is expanded in consideration of the range of plastic deformation that can maintain the connection structure 10 as described above.

The range of plastic deformation that can maintain the connection structure 10 is defined as uniform elongation (plastic elongation at the maximum test force) in JIS G0202 and JIS Z2241, for example. Even if the elongation (deformation amount) exceeds the range of elastic deformation, the stress increases as the elongation increases, but the steel pipe 2 is deformed almost uniformly in the circumferential direction until the uniform elongation. It is possible to maintain the connection structure 10 like this. Accordingly, the condition of the diameter expansion amount δ corresponding to the range of plastic deformation capable of maintaining the connection structure 10 is expressed by the following equation (15), where D is the outer diameter of the steel pipe 2 and A _U (%) is the uniform elongation. Is done.

Incidentally, in the steel pipe 2 is actually supplied as tensile test values described steel inspection certificate (mill sheet), than uniform elongation _{A U,} likewise JIS G0202, and at break defined in JIS Z2241 total Elongation is more common. For example, if only the total elongation at break as product information of the steel pipe 2 is available, it may be actually measured uniform elongation A _U in a manner as defined in JIS Z2241, as a convenient alternative, break The following equation (16) may be used with the total elongation at time A _D (%).

The above formula (16) is obtained by, for example, “Relationship between uniform elongation and breaking elongation in steel material tensile test” by Yoshihiro Iwata et al. (The Architectural Institute of Japan, Vol. 78, No. 683, pages 223-232) (January 2013) and the like. The above document describes that the magnitude relationship between the uniform elongation and the total elongation at break differs depending on the strength of the material. For example, a material having a tensile strength of 500 N / mm class ² has a uniform elongation A _U of about 1/2 of the total elongation _AD at break, whereas a material having a tensile strength of 800 N / mm class ² has a uniform elongation A _U of all at break. It may decrease to about 1/6 of the elongation _AD . In the above equation (16), based on these findings, and the elongation at 1/10 of the total elongation A _D as almost certainly smaller value than the uniform elongation A _U.

Table 2 shows a second design example of the connection structure 10 based on the above examination. In the following example, a steel pipe 2 having an outer diameter D of 114.3 mm (nominal diameter 100 A) and a Young's modulus E of 205.8 GPa (205.8 × 10 ³ N / mm ² ) is shown in FIG. Is 228.6 mm, the coefficient α in equation (11) is 1, the static friction coefficient μ, and the yield strength σ _y are variables, and the connecting structure 10 is designed based on the uniform elongation A _U and the total elongation A _D at break. ing. In Table, [delta] _min represents a lower limit of the diameter expansion amount [delta] calculated by equation (11), [delta] _max (if shown the value of uniform elongation _{A U)} formula (15) or formula (16) Indicates the upper limit value of the diameter expansion amount δ calculated by (when the value of the total elongation _AD at break is shown). As already described, the wider the allowable range (δ _max −δ _min ) of the diameter expansion amount δ, the more advantageous, for example, that an error in member processing or construction can be permitted.

In the above example, as a result of increasing the strength of the steel pipe 2, the yield strength σ _y becomes 460 N / mm ² , and accordingly, the values of the uniform elongation A _U and the total elongation A _D at break change (Example 10). , Example 11, Example 14, Example 15), and the case where the static friction coefficient μ was increased from 0.3 to 0.7 by roughening (Examples 12 to 15), Even in this case, the allowable range (δ _max −δ _min ) of the diameter expansion amount δ was significantly increased as compared with the case of the above design example 1. For example, among the outer diameter manufacturing tolerances of steel pipes specified in JIS G3444, No. 1 tolerance is ± 1%. Therefore, when the outer diameter D of the steel pipe 2 is 114.3 mm, a variation of ± 1.143 mm is allowed. Will be. The size of the allowable range (δ _max −δ _min ) of the diameter expansion amount δ is larger than the range of variation. Therefore, in the design example 2, it is possible to configure the connection structure 10 using a steel pipe manufactured with a normal manufacturing tolerance.

(Modification)
FIG. 4 is a schematic cross-sectional view showing a modification of the first embodiment of the present invention. In the connection structure shown in FIG. 4, a stopper 115 is provided on the inner periphery of the first member 11. In the illustrated example, the stopper 115 is provided on the straight surface 113 in contact with the tapered surface 112 of the first member 11, and abuts on the end surface 125 of the second member 12 inserted inside the first member 11. For example, the stopper 115 may be formed as a linear protrusion extending in the tube axis direction, or may be formed as an annular protrusion extending in the circumferential direction.

  By providing such a stopper 115, the insertion depth of the second member 12 into the first member 11 can be regulated. More specifically, for example, as shown in the drawing, when the second member 12 is inserted into the first member 11 to a predetermined depth dp, the first stopper 115 comes into contact with the end surface 125. The member 11 and the second member 12 are designed. This makes it easy to control the actual diameter expansion amount δ to an appropriate range as described above.

  The means for restricting the insertion depth of the second member 12 into the first member 11 is not limited to the stopper 115 described above. For example, a stopper may be provided on the second member 12. Specifically, a flange that rises outward from the center of the second member 12, that is, the bottom of the tapered surface 122, and comes into contact with the flange 114 of the first member 11 may be provided. Further, as a means other than restricting the insertion depth, a reference line indicating an appropriate insertion depth is drawn on the surface of the second member 12 or a propulsive force when the second member 12 is inserted into the first member 11 is used. For example, the diameter expansion amount δ may be controlled within an appropriate range.

  According to the connection structure 10 according to the first embodiment of the present invention described above, the connection of the steel pipe 2 is maintained by the frictional force acting between the friction surface 111 of the first member 11 and the inner peripheral surface 2s of the steel pipe 2. Is done. In this case, it is not necessary to weld a connecting member to the end surface of the steel pipe 2 or to form an opening or a flange in the steel pipe 2. In the above-described embodiment, prior processing for the steel pipe 2 is not required except for the roughening of the inner peripheral surface 2s, and the roughening of the inner peripheral surface 2s can be omitted. Therefore, in said embodiment, when connecting the steel pipe 2, the prior process with respect to the steel pipe 2 can be suppressed to the minimum.

(Second Embodiment)
FIG. 5 is a schematic perspective view showing members of a connection structure according to the second embodiment of the present invention. The connection structure 20 shown in FIG. 5 includes a first member 21 (illustrated as portions 21 a to 21 c) and a second member 22. As a difference from the connection structure 10 according to the first embodiment, a thread 216 is formed on the tapered surface 112 in the first member 21. On the other hand, in the second member 22, a thread groove 226 is provided on the tapered surface 122. Other than that, the connection structure 20 according to the present embodiment has the same configuration as the connection structure 10 according to the first embodiment.

  In the present embodiment, the screw thread 216 of the first member 21 and the screw groove 226 of the second member 22 are screw shapes corresponding to each other. By providing such a screw shape, the rotational force around the tube axis of the second member 22 or the first member 21 can be converted into a propulsive force when the second member 22 is inserted into the first member 21. it can. Therefore, in the present embodiment, the second member 22 is inserted inside the first member 21 inserted inside the steel pipe, and the second member 22 is further rotated around the pipe axis. As a result, the second member 22 can be inserted into the first member 21 to press the tapered surface 112 against the tapered surface 122, and as a result, the outer diameter of the first member 11 can be expanded. At this time, the first member 11 and the steel pipe may be rotated instead of the second member 22 or together with the second member 22.

  Further, in the present embodiment, the state in which the tapered surface 122 of the second member 22 presses the tapered surface 112 of the first member 21 to expand the outer diameter of the first member 21 is represented by the thread 216 and the thread groove 226. Can be maintained by the frictional force acting during Therefore, in this embodiment, it is not always necessary to form an adhesive layer between the tapered surface 122 of the second member 22 and the tapered surface 112 of the first member 21. However, an adhesive layer may be formed between the tapered surface 122 and the tapered surface 112 for the purpose of, for example, preventing the screws from loosening.

  Furthermore, in the present embodiment, the end of the screw thread 216 located on the flange 114 side of the first member 21 and the end of the screw groove 226 located on the center side of the second member 22 are formed so as to contact each other. May be. Thereby, the insertion depth of the second member 22 into the first member 21 can be regulated. Alternatively, the insertion depth is restricted by means such as a stopper provided on the straight surface 113 of the first member 21 as in the connection structure according to the modified example of the first embodiment described above, whereby the diameter expansion amount δ is appropriately set. It may be controlled within a range.

(Third embodiment)
FIG. 6 is a schematic perspective view showing members of a connection structure according to the third embodiment of the present invention. The connection structure 30 illustrated in FIG. 6 includes a first member 31 (illustrated as portions 31 a to 31 c) and a second member 32. As a difference from the connection structure 10 according to the first embodiment, in the first member 31, a tapered surface 312 and a straight surface 313 are formed on the inner periphery, and a thread 316 is formed on the straight surface 313. On the other hand, in the second member 32, a tapered surface 322 and a straight surface 323 are formed on the outer periphery, and a screw groove 326 is formed on the straight surface 323. Other than that, the connection structure 30 according to the present embodiment has the same configuration as the connection structure 10 according to the first embodiment.

  In the present embodiment, the tapered surface 312 of the first member 31 is a pressed surface and is pressed by the tapered surface 322 of the second member 32 that is a pressing surface. As in the first embodiment, when the second member 32 is inserted inside the first member 31, the tapered surface 322 of the second member 32 presses the tapered surface 312 of the first member 31. The outer diameter of the first member 31 is expanded. Further, the thread 316 of the first member 31 and the thread groove 326 of the second member 32 have screw shapes corresponding to each other. Similar to the second embodiment, such a screw shape allows the rotational force around the axis of the second member 32 or the first member 31 to drive the second member 32 into the first member 31. Is converted to Further, the state in which the tapered surface 322 of the second member 32 presses the tapered surface 312 of the first member 31 and the outer diameter of the first member 31 is expanded can be maintained.

  Further, in the present embodiment, a step 315 is formed between the tapered surface 312 and the straight surface 313 of the first member 31, and a step 325 is formed between the tapered surface 322 and the straight surface 323 of the second member 32. The By forming the steps 315 and 325 so as to contact each other, the insertion depth of the second member 32 into the first member 31 can be regulated. Alternatively, the insertion depth is regulated by means such as a stopper provided on the straight surface 313 of the first member 31 as in the connection structure according to the modified example of the first embodiment described above, whereby the diameter expansion amount δ is appropriately set. It may be controlled within a range.

  When the connecting structure 20 according to the second embodiment is compared with the connecting structure 30 according to the present embodiment, screw shapes corresponding to each other are formed on the inner periphery of the first member and the outer periphery of the second member. Are common. On the other hand, in the connecting structure 20, the screw shape is formed on the pressing surface and the pressed surface (tapered surfaces 112, 122), whereas in the connecting structure 30, the screw shape is different from the pressing surface and the pressed surface (straight). The points formed on the surfaces 313, 323) are different. In other words, in the connecting structure 20, the pressing surface, the pressed surface, and the screw shape overlap in the tube axis direction, whereas in the connecting structure 30, the pressing surface, the pressed surface, and the screw shape are different. Separated in the tube axis direction. The second embodiment and the third embodiment are selectively used depending on, for example, a thread-shaped processing condition.

(Fourth embodiment)
FIG. 7 is a schematic cross-sectional view showing a connection structure according to the fourth embodiment of the present invention. The connection structure 40 shown in FIG. 7 includes a first member 11 (including portions 11a to 11c and portions 11d to 11f, but the portions 11c and 11f are not shown) as in the first embodiment. And the second member 42. The second member 42 includes a hollow portion 427 that penetrates in the tube axis direction. About the other than that, the structure of the 2nd member 42 is the same as that of the 2nd member 12 which concerns on 1st Embodiment.

  When constructing a steel pipe as a structural member, a fluid such as mortar or water, or a construction tool such as a drill may pass through the steel pipe. In such a case, as shown in FIG. 7, by providing the second member 42 with the hollow portion 427, it becomes possible for the fluid and instrument as described above to pass through the connection structure. In addition, it is also possible to provide the same hollow part in the 2nd members 22 and 32 in 2nd Embodiment and 3rd Embodiment.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above embodiment, the outer diameter can be expanded by dividing the first member into three parts and providing a predetermined gap between the three parts. In another embodiment, the first member may be divided into two, or four or more parts, and the outer diameter may be expanded by providing a predetermined gap between the parts. In still other embodiments, the first member may be composed of a single part. In this case, for example, the outer diameter may be increased by providing the first member with a joint structure that can expand and contract in the circumferential direction. Alternatively, the first member may be formed with a C-shaped cross section including a slit in the tube axis direction, and when the second member is inserted, the outer diameter may be expanded by elastically deforming so that the slit is widened.

  DESCRIPTION OF SYMBOLS 10, 20, 30, 40 ... Connection structure 11, 21, 31 ... 1st member, 111 ... Friction surface, 112, 312 ... Tapered surface, 114 ... Flange, 115 ... Stopper, 216, 316 ... Screw thread, 12, 22, 32, 42 ... second member, 122, 322 ... tapered surface, 226, 326 ... thread groove, 427 ... hollow portion, 2 ... steel pipe, 2e ... end face, 2s ... inner peripheral surface.

Claims (11)

A first member inserted inside the steel pipe, and a second member inserted inside the first member,
The first member has a friction surface formed on the outer periphery and a pressed surface formed on the inner periphery.
The said 2nd member is a connection structure of the steel pipe which has a press surface which is formed in the outer periphery and expands the outer diameter of the said 1st member beyond the internal diameter of the said steel pipe by pressing the said to-be-pressed surface.   The steel pipe connection structure according to claim 1, wherein the first member is divided into a plurality of portions in the circumferential direction, and a gap is provided between the plurality of portions.   The steel pipe connection structure according to claim 1, wherein the pressing surface and the pressed surface are tapered surfaces having shapes corresponding to each other.   The steel pipe connection structure according to any one of claims 1 to 3, wherein screw shapes corresponding to each other are formed on an inner periphery of the first member and an outer periphery of the second member.   The steel pipe connection structure according to any one of claims 1 to 4, wherein an adhesive layer is formed between the pressing surface and the pressed surface.   The steel pipe connection structure according to any one of claims 1 to 5, wherein the friction surface or an inner peripheral surface of the steel pipe is roughened.   The steel pipe connection structure according to claim 6, wherein the friction surface or the inner peripheral surface of the steel pipe is subjected to blasting or metal spraying.   The steel pipe connection structure according to any one of claims 1 to 7, wherein the first member has a flange that rises outward from one end of the friction surface. The diameter δ of the steel pipe when the outer diameter of the first member is expanded beyond the inner diameter of the steel pipe is the outer diameter D of the steel pipe, the Young's modulus E of the steel pipe, and the yield strength σ _{y of the} steel pipe. , The static friction coefficient μ between the friction surface and the inner peripheral surface of the steel pipe, the length L of the friction surface in the axial direction of the steel pipe, and the coefficient α (0 <α ≦ 1) The connection structure of the steel pipe of any one of Claims 1-8 which exists in the range represented by Formula (i).

The diameter δ of the steel pipe when the outer diameter of the first member is expanded beyond the inner diameter of the steel pipe is the outer diameter D of the steel pipe, the Young's modulus E of the steel pipe, and the yield strength σ of the steel pipe. The connection structure of the steel pipe of any one of Claims 1-9 which exists in the range represented by following formula (ii) using _y .

As the diameter δ of the steel pipe when the outer diameter of the first member is expanded beyond the inner diameter of the steel pipe, the outer diameter D of the steel pipe and the uniform elongation A _U (%) of the steel pipe are used. It exists in the range represented by the following formula (iii) using the following formula (iii) or the following formula (iv) using the outer diameter D of the steel pipe and the total elongation at break A _D (%) of the steel pipe. The steel pipe connection structure according to any one of 9.

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