JP2016164327A - Joint structure between tubes with different diameter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint structure between a large diameter tube and a small diameter tube each having a diameter different from each other for allowing fluid to pass therethrough while ensuring required flexural capacity, axial strength and shear capacity in the joint part with a small working amount in the joint part at a low cost.SOLUTION: The joint structure is constituted of, including: a small diameter steel pipe 1; and a large diameter steel pipe 2; and a flat joint steel plate 3. After inserting the end part of the small diameter steel pipe 1 as the pile main body part into the end part of the large diameter steel pipe 2 of an expanded head part H in a tube in a tube axial direction, the flat joint steel plate 3 having a generally sector-shape is placed and welded between the large diameter steel pipe 2 of the expanded head part H and the small diameter steel pipe 1 as the pile main body part being inclined in the tube axial direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a joining structure of two pipes (a large diameter pipe and a small diameter pipe) having different diameters. For example, the present invention is applied to a widened pile in which a pile head is widened.

  Patent Documents 1 and 2 are known as prior art relating to the present invention.

  That is, in Patent Document 1, as shown in FIG. 13, in the head-expanded pile 20 to be sunk in the previously excavated hole, the upper portion of the small-diameter portion 22 is suppressed in order to suppress a decrease in supporting force at the root-fixed bulb portion at the lower end portion. The outer diameter surface of the large diameter portion 21 and the inner diameter surface of the lower portion of the large diameter portion 21 are connected by a plurality of radially arranged ribs 23, whereby the large diameter portion 21 and the small diameter portion 22 below the large diameter portion 21 are connected. The inflow part 24 into which a fluid can flow in from the outer side of a pile toward the inside is provided in the joint part in between. Also, the stress concentration is alleviated by setting both the joining angle θ2 of the lower end of the rib 23 to the outer diameter surface of the upper portion of the small diameter portion 22 and the joining angle θ1 of the upper end of the rib 23 to the inner diameter surface of the lower portion of the large diameter portion 21 to be acute angles.

  Moreover, in patent document 2, in order to provide the rational and economical different diameter steel pipe pile excellent in earthquake resistance, the 1st end part of the same diameter which can be combined with a large diameter pile material, and the said small diameter The first straight pipe part and the second straight pipe part are provided in the longitudinal center direction from each of the first end part and the second end part. And having a reduced diameter portion that decreases in diameter from the first straight pipe portion toward the second straight pipe portion, the steel pipe thickness of the second end portion is thicker than the steel pipe thickness of the first end portion, The steel pipe thickness of the reduced diameter portion is assumed to change continuously.

JP 2006-132100 A JP 2008-25156 A

  However, the above-described Patent Document 1 has the following problems.

  That is, since the outer diameter surface of the upper portion of the small diameter portion and the inner diameter surface of the lower portion of the large diameter portion are connected by a plurality of radially arranged ribs, the number of members and the number of joints are large, and processing is time-consuming and economical. Low.

  Further, the above-described Patent Document 2 has the following problems.

  That is, since it has a reduced diameter portion that decreases in diameter as it goes from the first straight pipe portion toward the second straight pipe portion, the processing cost for reducing the diameter increases, so the economy is low.

  The present invention was made in order to solve the above-described problems. As a joining structure of a large diameter pipe and a small diameter pipe having different diameters, a bending strength, a shaft strength, and a shear strength necessary for a joint portion are provided. An object of the present invention is to provide a joining structure for different diameter pipes that allows a fluid to pass through a pipe with a small amount of processing of the joining portion and high economic efficiency.

  In order to solve the above problems, the present invention has the following features.

  [1] A joining structure of a large-diameter pipe and a small-diameter pipe having different diameters, wherein the small-diameter pipe end is inserted into the large-diameter pipe end in the pipe axis direction, and the large-diameter pipe and the small-diameter pipe are A flat, generally fan-shaped joint plate is installed to be inclined with respect to the pipe axis direction, the outer elliptical arc portion of the joint plate is joined to the inner diameter portion of the large-diameter pipe, and the inner elliptical arc portion of the joint plate is A joining structure of different diameter pipes, which is joined to the outer diameter part of the small diameter pipe and through which a fluid can pass.

  [2] The joint structure of different diameter pipes according to [1], wherein the large-diameter pipe, the small-diameter pipe, and the substantially fan-shaped joint plate are made of metal.

  [3] The above-mentioned [2], wherein the elliptical arc part outside the joint plate and the inner diameter part of the large-diameter pipe, and the elliptical arc part inside the joint plate and the outer-diameter part of the small-diameter pipe are joined by welding. ] The joint structure of the different-diameter pipes as described above

  [4] The joint structure of different-diameter pipes according to [2] or [3], which is applied to a pile head structure of a steel pipe pile and the head is the large-diameter pipe.

  [5] The joint structure of different diameter pipes according to any one of the above [2] to [4], which is applied to a pile head structure of a ready-made pile in the Nakabori method.

  [6] The joint structure for different diameter pipes according to any one of [1] to [5], wherein the joint plate is provided in two stages in the pipe axis direction.

  According to the present invention, as a joining structure of a large-diameter pipe and a small-diameter pipe having different diameters, the bending portion, the shaft strength, and the shear strength necessary for the joint portion are ensured, and the amount of processing of the joint portion is small and highly economical. In addition, it is possible to obtain a joint structure of different diameter pipes through which the fluid can pass through the pipe.

It is a side perspective view of the head-expansion pile structure in Embodiment 1 of this invention. It is an arrow line view of the pipe axial center position of the head-expansion pile structure in Embodiment 1 of this invention. It is an AA arrow directional view of the head-expansion pile structure in Embodiment 1 of this invention. It is a BB arrow line view of the head-expansion pile structure in Embodiment 1 of this invention. It is a figure which shows the joint steel plate shape of the head-expansion pile structure in Embodiment 1 of this invention. It is a side perspective view of the head-expansion pile structure in Embodiment 2 of this invention. It is an arrow line view of the pipe axial center position of the head-expansion pile structure in Embodiment 2 of this invention. It is an AA arrow directional view of the expansion pile structure in Embodiment 2 of the present invention. It is a BB arrow line view of the head extension pile structure in Embodiment 2 of the present invention. It is a figure which shows the joint steel plate shape of the head-expansion pile structure in Embodiment 2 of this invention. It is a side perspective view of the head-expansion pile structure in Embodiment 3 of this invention. It is a longitudinal cross-sectional view of the pipe axial center position which shows the construction procedure of the head-expansion pile structure in Embodiment 3 of this invention. It is a figure which shows the conventional head-expanded pile structure (patent document 1).

  An embodiment of the present invention will be described. Here, a case where the present invention is applied to a steel pipe pile having an enlarged head will be described as an example.

  First, the steel pipe pile having an enlarged head is generally as follows although it varies depending on the ground conditions, the construction method, and the like.

  That is, in the design of a steel pipe pile, the axial force acting per steel pipe pile is calculated from the weight of the superstructure supported by the steel pipe pile and the number of piles, and the dimension of the steel pipe pile is determined by this acting axial force. However, a horizontal force also acts on the pile head due to an action such as an earthquake. The cross section of the steel pipe pile is determined by the acting axial force if the acting horizontal force is small, and it may be an equal section in the length direction. However, if the acting horizontal force is large, only the pile head where a large bending moment and shearing force are applied. It is economical to increase the cross section.

  Therefore, an expanded pile structure that is economical, has a predetermined stress transmission performance and is easy to manufacture in the steel pipe pile field is desired.

  In view of such a situation, in the embodiment of the present invention, the basic concept is as follows.

  That is, the Nakabori method is a construction method of a pile in which the pile is sunk by excavating the hollow part of the ready-made pile by its own weight, press-fitting or hammering, but in the embodiment of the present invention, it is used in the Nakabori method. In order to apply to ready-made piles, the end of the small-diameter steel pipe of the pile main body is inserted in the pipe axis direction into the end of the large-diameter steel pipe of the enlarged head, and between the large-diameter steel pipe of the enlarged head and the small-diameter steel pipe of the pile main body. A flat, substantially fan-shaped joint steel plate is welded while being inclined with respect to the pipe axis direction.

  At that time, the elliptical arc part on the outer side of the flat substantially fan-shaped joint steel plate is welded to the inner diameter surface of the large-diameter steel pipe with the enlarged head, and the elliptical arc part on the inner side of the flat substantially sector-shaped joint steel plate is attached Weld to the radial surface. By placing flat flat fan-shaped joint steel plates at an incline with respect to both steel pipes, a re-shaped groove is formed between the edge of the joint steel plate (end face), the inner surface of the large-diameter steel pipe, and the outer surface of the small-diameter steel pipe. Thus, complete penetration welding is possible without the need to groove the joint of the joint steel plate.

  And if the shape of the joint steel plate is substantially fan-shaped and two or more joint steel plates are inclined and welded, the outer large-diameter steel pipe and the inner small-diameter steel pipe and joint are satisfied while satisfying the weld length required for stress transmission. Continuous and three-dimensional joining with a steel plate can be realized, and a rigid portion with three members is formed, and bending strength, axial strength, and shear strength necessary for the joint can be ensured.

  Note that the gap between the joint steel plates may or may not exist, and the size of the gap may be determined within a range necessary for stress transmission.

  When two joint steel plates are installed, the bending strength and the shear strength differ depending on the direction of the action of the force, and therefore the number of joint steel plates may be increased as necessary. If four joint steel plates are installed, bending strength and shear strength that are generally symmetrical in the cross-sectional direction of the steel pipe can be obtained.

  However, if the number of joint steel plates is increased, the economy is reduced accordingly. When the acting force in the cross-sectional direction of the pile varies depending on the angle, even if there are two bonded steel plates, rational design is possible by properly using the installation direction.

  With the above structure, the bending strength, axial strength and shear strength necessary for the joint can be secured, the joint steel plate is a flat plate, the number of members of the joint steel plate is small, and the diameter of the joint is special. Therefore, it is not necessary to perform processing that requires special skills, so that a highly economical joint structure for different diameter pipes can be obtained. And since the inside of a steel pipe is not obstruct | occluded, since the fluid containing soil, soil cement, cement paste, etc. can pass through the inside of a pipe, it has a structure suitable for the ready-made pile used for the Nakabori method.

  Next, Embodiments 1 to 3 that embody the above basic concept will be described with reference to the drawings.

[Embodiment 1]
1-4 is a figure which shows the head-expansion pile structure in Embodiment 1 of this invention. FIG. 1 is a side perspective view, and FIG. 2 is a longitudinal sectional view of a tube axis position. 3 is an AA arrow view in FIGS. 1 and 2, and FIG. 4 is a BB arrow view in FIGS. 1 and 2. In other words, FIG. 1 is a CC perspective view in FIGS. 3 and 4, and FIG. 2 is a DD arrow view in FIGS. 3 and 4.

  As shown in FIGS. 1-4, in this Embodiment 1, a pile head is installed by installing the large diameter steel pipe 2 with a diameter larger than the small diameter steel pipe 1 in the pile head H of the small diameter steel pipe 1 which is a pile main body. Improve the bending resistance and shear resistance of the part.

  And in order to transmit force from the large diameter steel pipe 2 to the small diameter steel pipe 1 which is a pile main body, the two joint steel plates 3 which connect both are installed. Since it is economical to use a flat plate that does not require bending as the joint steel plate 3 and to secure a weld length necessary for transmitting force, the flat joint steel plate 3 is provided with an inclination and has a small diameter. The outer surface of the steel pipe 1 and the inner surface of the large diameter steel pipe 2 are welded. The reference numeral 4 in FIGS. 2 to 4 is the weld bead.

  Therefore, as shown in FIG. 5, the joint steel plate 3 is preferably a flat substantially sector shape having an inner elliptical arc 3a and an outer elliptical arc 3b. As shown in FIG. 2, the flat and substantially fan-shaped joint steel plate 3 is installed on both steel pipes (small-diameter steel pipe 1 and large-diameter steel pipe 2) with an inclination, so that the edge of the joint steel plate 3 and the small-diameter steel pipe Since a lave groove is formed by the outer surface of 1 and the inner surface of the large-diameter steel pipe 2, welding with both steel pipes can be performed by complete penetration without providing a groove. The two sides of the straight portion 3c of the substantially fan-shaped joint steel sheet 3 can further relax the stress concentration at the end of the joint steel sheet 3 in the small diameter steel pipe 1 by making the angle formed with the outer surface of the small diameter steel pipe 1 acute. .

  Whether or not the joint steel plate 3 and the large-diameter steel pipe 2 are welded over the entire length to both ends of the elliptical arc 3b outside the joint steel plate 3 is determined according to the balance between weldability and strength. Can do.

  Moreover, the joint steel plate 3 may be accommodated in the large-diameter steel pipe 2, or the end portion may protrude outside the large-diameter steel pipe 2 as shown in FIG. If the joint steel plate 3 is accommodated in the large-diameter steel pipe 2 and welded to the inner surface of the large-diameter steel pipe 2 over the entire length to both ends of the elliptical arc 3b outside the joint steel plate 3, the joint strength is enhanced. Welding in narrow spaces increases and welding workability deteriorates.

  Incidentally, the shape of the elliptical arc 3a inside the substantially sector-shaped joint steel plate 3 is a part of an ellipse represented by the following formula (1) with the steel pipe axis as the center of the ellipse. Note that x is a coordinate in the major axis direction, and y is a coordinate in the minor axis direction.

  Here, if the outer diameter of the small-diameter steel pipe 1 is 2r and the angle between the joint steel plate 3 and the cross-sectional direction of the steel pipe is α, the length of the major axis of the ellipse is 2r / cos α. In other words, the ellipse represented by the formula (1) is the shape of the cut surface when the small diameter steel pipe 1 is cut obliquely at the inclination angle α.

  The shape of the elliptical arc 3b outside the substantially sector-shaped joint steel plate 3 is a part of an ellipse represented by the following equation (2) with the steel pipe axis as the center of the ellipse. Note that x is a coordinate in the major axis direction, and y is a coordinate in the minor axis direction.

  Here, assuming that the inner diameter of the large-diameter steel pipe 2 is 2R and the angle between the joint steel plate 3 and the cross-sectional direction of the steel pipe is α, the length of the major axis of the ellipse is 2R / cos α. In other words, the ellipse represented by the formula (2) is the shape of the cut surface when the large-diameter steel pipe 2 is cut obliquely at the inclination angle α.

  Thus, since the shape of the joint steel plate 3 can be easily determined by the above formulas (1) and (2), the flat steel plate can be punched or laser-cut in advance at the factory without being adjusted on site. You can make it. The angle α between the joint steel plate 3 and the cross-sectional direction of the steel pipe is preferably 30 ° to 60 ° from the viewpoint of stress transmission and a range where complete penetration welding is possible without providing a groove.

[Embodiment 2]
6-10 is a figure which shows the head-expansion pile structure in Embodiment 2 of this invention. FIG. 6 is a side perspective view, and FIG. 7 is a longitudinal sectional view of the tube axis position. 8 is an AA arrow view in FIGS. 6 and 7, and FIG. 9 is a BB arrow view in FIGS. 6 and 7. In other words, FIG. 6 is a CC perspective view in FIGS. 8 and 9, and FIG. 9 is a DD arrow view in FIGS. 6 and 7. Moreover, FIG. 10 is a figure which shows the shape of the joint steel plate 3 used in this Embodiment 2. FIG.

  As shown in FIGS. 6 to 10, in the second embodiment, four substantially fan-shaped joint steel plates 3 are used in the pipe circumferential direction.

  When the number of the joint steel plates 3 is increased in this way, there is an advantage that anisotropy regarding bending strength and shear strength between the large diameter steel pipe 2 and the small diameter steel pipe 1 is relaxed. However, there is a disadvantage that the number of members increases and the economic efficiency decreases.

[Embodiment 3]
FIG. 11 and FIG. 12 are diagrams showing the expanded pile structure in the third embodiment of the present invention. FIG. 11 is a side perspective view, and FIG. 12 is a longitudinal sectional view of a tube axis position showing a construction procedure.

  As shown in FIG. 11, in this Embodiment 3, the joint steel plate 3 is installed in two steps in the pipe axis direction.

  When the acting horizontal force is large and the required bending strength and shear strength cannot be obtained with one stage of the joint steel sheet 3, the joint steel sheet 3 may be installed in two stages.

  If it is up to two stages, as shown in FIGS. 12 (a) and 12 (b), as procedure 1, the joint steel plate 3 near the end of the small diameter steel pipe 1 is welded to the small diameter steel pipe 1, and the other joint steel plate is obtained. 3 is welded to the large-diameter steel pipe 2, and then as a procedure 2, the small-diameter steel pipe 1 is inserted into the large-diameter steel pipe 2 from the side where the joint steel plate 3 is not welded, and then the joint on the side far from the end of the small-diameter steel pipe 1 If the steel plate 3 is welded to the small diameter steel pipe 1 and the other joint steel plate 3 is welded to the large diameter steel pipe 2, the welding can be easily performed.

  Thus, in the embodiment of the present invention, the following effects can be obtained.

  (A) Realizing a joint structure of different diameter pipes that allows fluid to pass through the pipe with a small amount of processing of the joint part and high economic efficiency while ensuring the required bending strength, axial strength and shear strength of the joint. be able to.

  (B) Since the inside of the steel pipe is not blocked, a fluid containing soil, soil cement, cement paste, or the like can pass through. Therefore, it can be used as a ready-made pile of the Nakabori method, which is a construction method of the pile.

  (C) By placing a flat, substantially fan-shaped joint steel plate at an inclination with respect to the small-diameter steel pipe and the large-diameter steel pipe, the groove shape of the ladle is formed between the edge of the joint steel plate and the outer surface of the small-diameter steel pipe and the inner surface of the large-diameter steel pipe. Therefore, complete penetration welding is possible even if the elliptical arc portion of the joint steel plate is not grooved, and both economic efficiency and welding safety can be achieved.

  (D) If two or more joint steel plates are welded at an inclination, the outer large-diameter steel pipe, the inner small-diameter steel pipe, and the joint steel plate are continuously and three-dimensionally satisfied while satisfying the weld length necessary for stress transmission. Can be realized, and a rigid portion is formed by three members, and the bending strength, axial strength, and shear strength necessary for the joint can be ensured.

  (E) By adopting a flat, substantially fan-shaped joint steel plate that does not use out-of-plane bending or diameter reduction processing of a plate with high processing costs, manufacturing costs can be kept low.

  (F) The stress concentration phenomenon in the pipe axial direction end part of a joint steel plate can be relieve | moderated by inclining a joint steel plate and joining with a large diameter steel pipe and a small diameter steel pipe.

  And in said embodiment, although the case where this invention was applied to a head-expansion pile structure was described as an example, this invention is applicable also to the joining structure of another different diameter pipe.

  Further, the present invention can also be applied when the large-diameter pipe, the small-diameter pipe, and the substantially fan-shaped joint plate are metals other than steel (for example, aluminum and copper).

  Furthermore, the present invention can also be applied when the large-diameter pipe, the small-diameter pipe, and the substantially fan-shaped joint plate are made of a metal or less material (for example, plastic).

DESCRIPTION OF SYMBOLS 1 Small diameter steel pipe 2 Large diameter steel pipe 3 Joint steel plate 3a Elliptical arc inside joint steel plate 3b Elliptical arc outside joint steel plate 3c Straight section of joint steel plate 4 Weld bead H Pile head of steel pipe pile

Claims (6)

  A large-diameter pipe and a small-diameter pipe having different diameters, each having a small-diameter pipe end inserted through the end of the large-diameter pipe in a tube axis direction, and being flat between the large-diameter pipe and the small-diameter pipe. A generally fan-shaped joint plate is inclined with respect to the pipe axis direction, the outer elliptic arc portion of the joint plate is joined to the inner diameter portion of the large-diameter pipe, and the inner elliptic arc portion of the joint plate is joined to the small-diameter pipe A joint structure of different diameter pipes that allow fluid to pass through the pipe, joined to the outer diameter part of the pipe.   The joint structure for different diameter pipes according to claim 1, wherein the large diameter pipe, the small diameter pipe, and the substantially fan-shaped joint plate are made of metal.   The elliptical arc part outside the joint plate and the inner diameter part of the large-diameter pipe, and the elliptical arc part inside the joint plate and the outer diameter part of the small-diameter pipe are joined by welding. Joint structure of different diameter pipes.   It is applied to the pile head structure of a steel pipe pile, and the head is the said large diameter pipe, The joining structure of the different diameter pipe | tube of Claim 2 or 3 characterized by the above-mentioned.   The joint structure of different diameter pipes according to any one of claims 2 to 4, which is applied to a pile head structure of a ready-made pile in the Nakabori method.   The joint structure for different diameter pipes according to any one of claims 1 to 5, wherein the joint plate is installed in two stages in the pipe axis direction.

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