JP2012154048A - Joint structure for steel pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint structure capable of shortening its joint part while securing its reference strength.SOLUTION: A distance BL4 from a cylinder side joint surface 23 to a cylinder side key groove 26 nearest to the cylinder side joint surface 23 is set so that tensile strain which is generated in the cylinder side key groove 26 farthest from the cylinder side joint surface 23 when external force operates on an axial joint part 10 and a cylindrical joint part 20 is greater than tensile strain which is generated in an axial side key groove 16 nearest to an axial side joint surface 13 when external force operates on the axial joint part 10 and the cylindrical joint part 20.

Description

  The present invention relates to a steel pipe joint structure in which two steel pipes used for steel pipe piles, steel pipe sheet piles, and the like are joined in the longitudinal direction so as not to be inserted and removed.

  Conventionally, there has been such a steel pipe joint structure as described in Patent Document 1. The joint structure of the steel pipe described in Patent Document 1 includes a shaft-like joint portion (“pin joint material” in the literature) fixed to the tip of one of the two steel pipes and the other of the two steel pipes. A tubular joint portion (“box joint material” in the literature) that is fixed to the tip of the steel pipe and into which the shaft-like joint portion is inserted and fitted. The shaft-like joint portion includes a shaft-side base portion (“base tube portion” in the literature) that is fixed to one steel pipe, an insertion portion that extends from the shaft-side base portion and has an outer diameter smaller than that of the shaft-side base portion, shaft A shaft-side joint surface (“engagement end surface” in the literature) that is a step portion between the side base portion and the fitting insertion portion, a shaft-side recess (“engagement recess” in the literature) circumferentially provided on the shaft-side joint surface, and A shaft-side convex portion (“engagement protrusion” in the literature) is provided around the tip of the insertion portion.

  Further, the cylindrical joint portion includes a cylindrical base fixed to the other steel pipe, a fitting receiving portion that extends from the cylindrical base and has an inner diameter larger than that of the cylindrical base, and receives the fitting insertion portion. A cylinder-side joint surface (in the literature, “end face”) that is provided at the tip of the cylinder, and a cylinder-side convex portion that is provided around the cylinder-side joint surface and engages the shaft-side recess (in the literature, “protrusion”). Part "), and a cylinder-side recess (" recess "in the literature) that is provided around the step portion between the cylinder-side base and the fitting receiving part and engages with the shaft-side protrusion.

  Further, one or more shaft-side key grooves (“outer groove strip” in the literature) are provided around the outer peripheral portion of the fitting insertion portion, and the shaft-like joint portion is connected to the inner peripheral portion of the fitting receiving portion. One or more cylinder-side key grooves (in the literature, “inner groove strips”) corresponding to the shaft-side key grooves when inserted into the portion are provided. And as a means for restraining relative movement between at least the longitudinal joint portion and the tubular joint portion in the longitudinal direction, it is disposed so as to be engaged across the mutually corresponding shaft side key groove and tubular side key groove. One or more key members (“load transmission key” in the literature) are provided. The key member is disposed in the cylinder-side key groove, and is engaged across the shaft-side key groove and the cylinder-side key groove by a bolt that is screwed inward in the radial direction by an operation from the outside of the cylindrical joint. To do.

JP 2000-234333 A

  By the way, with regard to such a steel pipe joint structure, when an external force such as seismic force is applied to two steel pipes or a joint between the steel pipes (shaft joint part and cylindrical joint part), the steel pipe itself is first destroyed. However, if the external force is considerably large, the steel pipes are broken at the thin portions (shaft side keyway and tube side keyway). Since the joint structure of steel pipes is mainly made of iron, it is particularly broken by tension. In addition, when a structure is damaged during an earthquake or the like, a steel pipe pile or the like may be pulled out to verify the destruction status. In this case, it is easy to verify if a specific part is destroyed. Therefore, for reasons such as easy visual observation, a method has been adopted in which the dimensions of each part are designed so that the cylinder side keyway of the cylindrical joint part exposed to the outside is broken prior to the shaft side keyway.

In this design method, the dimensions of each part are determined by the following two steps.
(1) Step 1
The tensile stress generated in the cylinder side key groove by the action of a predetermined external force is obtained, and the thickness of the cylinder side key groove is determined so that the cylinder side key groove becomes the weakest while ensuring the reference strength of the cylinder side key groove.
(2) Step 2
About the thickness of another part, the dimension is determined so that it may become higher intensity | strength than a cylinder side keyway.

  When multiple sets of shaft-side key grooves, cylinder-side key grooves, and key members are provided, internal stress increases as the distance from the tip of each joint increases. Paying attention to the separated cylinder side key groove and the axis side key groove closest to the axis side joint surface, at least the cylinder side key groove farthest from the cylinder side joint surface is the axis side key groove closest to the axis side joint surface. It was designed to be destroyed in advance.

  However, in the joint structure designed in this way, there is no standard as to how to set the joint length, and the shaft joint part and the cylindrical joint part have to be lengthened unnecessarily, resulting in good economic efficiency. There was no joint structure. If the overlap between the fitting insertion portion and the fitting receiving portion is simply shortened, the strength of the joint portion decreases, so there is a limit to shortening the length of the joint portion without any guideline.

  In view of such circumstances, an object of the present invention is to provide a joint structure that can shorten the length of the joint portion while ensuring the reference strength.

  The characteristic structure of the steel pipe joint structure according to the present invention is a steel pipe joint structure in which two steel pipes are joined together in the longitudinal direction so that they cannot be inserted and removed, and is fixed to the tip of one of the two steel pipes. A shaft-like joint portion, and a cylindrical joint portion that is fixedly attached to the tip of the other steel pipe of the two steel pipes and into which the shaft-like joint portion is inserted and fitted. A shaft-side base fixed to the one steel pipe, a fitting insertion portion extending from the shaft-side base and having an outer diameter smaller than that of the shaft-side base, and a stepped portion between the shaft-side base and the fitting insertion portion A shaft-side joint surface, a shaft-side concave portion provided around the shaft-side joint surface, and a shaft-side convex portion provided around the distal end portion of the fitting insertion portion. The cylinder side base fixed to the other steel pipe, and extending from the cylinder side base and having an inner diameter larger than the cylinder side base, A fitting receiving portion that receives the fitting insertion portion; a cylinder-side joining surface that is in contact with the shaft-side joining surface; and is provided around the tube-side joining surface and is engaged with the shaft-side recess. A cylinder-side convex part, and a cylinder-side concave part that is provided around a step part between the cylinder-side base part and the fitting receiving part, and that engages with the shaft-side convex part, and on the outer peripheral part of the fitting insertion part, One or more shaft-side key grooves are provided around the shaft-side key groove when the shaft-like joint portion is inserted into the cylindrical joint portion on the inner peripheral portion of the fitting receiving portion. A cylinder-side key groove, and disposed so as to straddle across the corresponding shaft-side key groove and the cylinder-side key groove, and at least the shaft-shaped joint portion in the longitudinal direction; One or more key members that restrain relative movement with the cylindrical joint portion are further provided, and an external force is applied to the shaft joint portion and the cylindrical joint portion. The tensile strain generated in the cylinder side keyway furthest away from the cylinder side joint surface is closest to the shaft side joint surface when the external force is applied to the shaft joint part and the cylindrical joint part. The distance from the cylinder side joint surface to the cylinder side key groove closest to the cylinder side joint surface is set so as to be larger than the tensile strain generated in the shaft side key groove.

  As described above, in the joint structure of steel pipes, conventionally, attention has been paid to the tensile stress generated in each key groove. However, as the test and research are repeated, the inventor has increased the tensile stress in each key groove. Based on this, a bending moment (secondary bending) was generated, and it was thought that the bending moment had a great influence on the fracture of the keyway. And by the inventor's earnest research, like this characteristic configuration, by managing the distance from the cylinder side joint surface to the cylinder side key groove closest to the cylinder side joint surface, the shaft joint part and the cylindrical joint The tensile strain generated in the cylinder-side keyway that is farthest from the cylinder-side joint surface when an external force is applied to the part can be greater than the tensile strain generated in the shaft-side keyway that is closest to the shaft-side joint surface. I understood. In other words, the design criteria regarding the joint length that would destroy the cylinder-side keyway furthest away from the cylinder-side joint surface prior to the shaft-side keyway closest to the axis-side joint surface became clear. Therefore, it is possible to provide a steel pipe joint structure with good economic efficiency.

  In the steel pipe joint structure according to the present invention, it is preferable that the distance from the tube side joint surface to the tip end surface of the tube side key groove closest to the tube side joint surface is set to 33 mm or less.

  Based on further earnest research by the inventor, a specific design standard that the distance from the cylinder side joint surface to the tip side end surface of the cylinder side key groove closest to the cylinder side joint surface is 33 mm or less as in this feature configuration. Becomes clear, and it can be set as the joint structure of the steel pipe which is easier to design.

It is a perspective view which shows the joint structure of the steel pipe which concerns on this invention. It is a longitudinal direction sectional view showing the joint structure of a steel pipe concerning the present invention. It is a figure which shows the relationship between BL4 and the ratio of the distortion | strain in a keyway with respect to a reference | standard distortion. It is sectional drawing of the longitudinal direction of the cylinder side keyway in a one-stage type joint structure. It is sectional drawing of the longitudinal direction of the shaft side keyway in a one-stage type joint structure. It is sectional drawing of the longitudinal direction of the cylinder side keyway in a two-stage type joint structure. It is sectional drawing of the longitudinal direction of the shaft side keyway in a two-stage type joint structure. It is an example (diameter 400-800) of a suitable joint with respect to steel pipe SKK490. It is an example (diameter 900-1200) of a suitable joint with respect to steel pipe SKK490. It is an example (diameter 400-800) of a suitable joint with respect to steel pipe SKK400. It is an example (diameter 400-800) of a suitable joint with respect to steel pipe SKK400. It is a perspective view which shows the joint structure of the steel pipe which concerns on another embodiment. It is radial direction sectional drawing which shows the joint point of the joint structure of the steel pipe which concerns on another embodiment.

  Hereinafter, an example in which a steel pipe joint structure according to the present invention is applied to a steel pipe pile (pile foundation) buried in the ground will be described with reference to the drawings.

[Outline of steel pipe pile]
The steel pipe pile is configured by positioning a plurality of steel pipes on substantially the same axis X and joining them in the longitudinal direction so that they cannot be inserted and removed. Since the design length of steel pipe piles can be as long as several tens of meters, it is impossible to transport them to the construction site after joining them at the factory. Join.

[Outline of steel pipe joint structure]
No matter how many steel pipes the steel pipe pile is composed of, the joints between the steel pipes are the same at all points. Therefore, as shown in FIG. 1, the joint structure of a steel pipe will be described by paying attention to a specific upper pile 2 and lower pile 1 that are in a vertical relationship. Formally called the upper pile 2 and the lower pile 1, but these are substantially the same steel pipe. That is, the upper pile 2 and the lower pile 1 correspond to “two steel pipes” according to the present invention. A male pin joint 10 is fixed to the tip of the upper pile 2 of the lower pile 1 by welding at the factory. A box joint 20 that is externally fitted to the pin joint 10 in the factory is fixed to the tip of the upper pile 2 on the lower pile 1 side by welding. That is, the pin joint 10 corresponds to the “shaft joint portion” according to the present invention, and the box joint 20 corresponds to the “tubular joint portion” according to the present invention.

  As shown in FIG. 1 and FIG. 2, the pin joint 10 is formed in a cylindrical shape like the lower pile 1. The pin joint 10 includes a shaft base 11 fixed to the lower pile 1, a fitting insertion portion 12 extending from the shaft base 11 and having an outer diameter smaller than that of the shaft base 11, and the shaft base 11 fitted. A shaft side joint surface 13 which is a stepped portion with the insertion portion 12, a shaft side concave portion 14 provided around the shaft side joint surface 13, and a shaft side convex portion 15 provided around the distal end portion of the fitting insertion portion 12. It is equipped with.

  The shaft-side base 11 has the same inner diameter, outer diameter, and thickness as the lower pile 1 on the lower pile 1 side, and the outer diameter is increased and the wall thickness is increased while decreasing the inner diameter from the middle portion. The fitting insertion portion 12 has an inner peripheral surface obtained by extending the inner peripheral surface of the shaft-side base 11 with the same diameter, and an outer peripheral surface obtained by reducing the diameter of the outer peripheral surface of the shaft-side base 11 stepwise. The shaft-side recess 14 is formed by recessing an inner diameter side portion of the shaft-side joining surface 13 in an annular shape on the lower pile 1 side along the axis X direction. The shaft-side convex portion 15 is formed by projecting an outer diameter side portion of the distal end portion of the fitting insertion portion 12 in an annular shape toward the distal end side along the axis X direction.

  As shown in FIGS. 1 and 2, the box joint 20 is formed in a cylindrical shape like the lower pile 1. The box joint 20 includes a cylinder side base 21 fixed to the upper pile 2, a fitting receiving part 22 that extends from the cylinder side base 21 and has an inner diameter larger than that of the cylinder side base 21, and receives the fitting insertion part 12. A cylinder-side joint surface 23 that is provided at the distal end of the fitting receiving portion 22 and is in contact with the shaft-side joint surface 13; a cylinder-side convex portion 24 that is provided around the cylinder-side joint surface 23 and that engages with the shaft-side recess 14; A cylinder-side concave portion 25 is provided around the step portion between the cylinder-side base portion 21 and the fitting receiving portion 22 and engages with the shaft-side convex portion 15.

  The cylinder-side base 21 has the same inner diameter, outer diameter, and thickness as the upper pile 2 on the side of the upper pile 2, and from the middle part, the outer diameter is increased while increasing the outer diameter while increasing the thickness. . The fitting receiving portion 22 has an inner peripheral surface obtained by expanding the inner peripheral surface of the cylinder side base portion 21 stepwise, and an outer peripheral surface obtained by extending the outer peripheral surface of the tube side base portion 21 with the same diameter. The tube-side convex portion 24 is formed by projecting an inner diameter side portion of the tube-side joint surface 23 in an annular shape toward the tip side along the axial center X direction. The cylinder-side recess 25 is formed by recessing a portion on the outer diameter side of the stepped portion between the cylinder-side base 21 and the fitting receiving portion 22 in an annular shape on the tip side along the axis X direction.

  As shown in FIG. 2, the outer diameter of the fitting portion 12 and the inner diameter of the fitting portion 22 are set to be substantially the same, and when the pin joint 10 is inserted into the box joint 20, it fits with the outer peripheral surface of the fitting portion 12. The inner surface of the receiving portion 22 is in close contact with the shaft side joint surface 13 and the tube side joint surface 23. The cross-sectional shape of the shaft-side recess 14 in the direction of the axis X is set so as to be engageable with the tube-side protrusion 24. The cross-sectional shape of the cylinder side recess 25 in the axis X direction is set so as to be engageable with the axis side protrusion 15. Further, the inner peripheral surface of the insertion portion 12 and the inner peripheral surface of the tube side base portion 21 are set to be flush with each other.

  One shaft side keyway 16 is provided around the outer peripheral portion of the insertion portion 12 along the circumferential direction of the shaft core X. Similarly, one cylinder side key groove 26 corresponding to the shaft side key groove 16 when the pin joint 10 is inserted into the box joint 20 is provided around the inner periphery of the fitting receiving portion 22. The cross-sectional shape of the shaft side keyway 16 and the cylinder side keyway 26 in the axis X direction is a rectangle having the same length in the axis X direction. When the pin joint 10 is inserted into the box joint 20, the shaft-side key groove 16 and the cylinder-side key groove 26 face each other and cooperate to form one groove having a rectangular cross section.

  A plurality of screw holes communicating from the outer peripheral portion of the fitting receiving portion 22 to the cylinder side key groove 26 are provided at intervals in the circumferential direction at a portion of the fitting receiving portion 22 where the cylinder side key groove 26 is provided. Has been. A set bolt 30 is screwed into the screw hole, and the set bolt 30 can be screwed inward in the radial direction by a tightening operation from the outside of the box joint 20. The cylinder side keyway 26 accommodates a load transmission key 31 as a “key member”. The tip of the set bolt 30 is fixed to the load transmission key 31, and the load transmission key 31 can project radially inward from the cylinder side key groove 26 by tightening the set bolt 30.

  The groove depth of the cylinder side key groove 26 is larger than the length of the load transmission key 31 in the radial direction, and the groove depth of the shaft side key groove 16 is the length of the load transmission key 31 in the radial direction. About 1/2. The shape of the load transmission key 31 is an arc shape that is accommodated in the cylinder-side key groove 26 with almost no gap in the state of being most retracted in the cylinder-side key groove 26. Therefore, when the load transmission key 31 is most retracted into the cylinder side key groove 26, the load transmission key 31 does not protrude from the inner peripheral surface of the fitting receiving portion 22. That is, the pin joint 10 can be smoothly inserted into the box joint 20 by retracting the load transmission key 31 most into the cylinder side key groove 26. Further, when the pin joint 10 is inserted into the box joint 20, when the load transmission key 31 is protruded most from the cylinder side key groove 26, the load transmission key 31 is substantially inserted into the cylinder side key groove 26 and the shaft side key groove 16. Lock evenly. Thereby, the relative movement of the pin joint 10 and the box joint 20 in the axial center X direction is restrained.

  In addition, the joint structure that restrains the relative movement of the pin joint 10 and the box joint 20 in the axial center X direction by the pair of the shaft side key groove 16, the cylinder side key groove 26, and the load transmission key 31 in this way. Hereinafter, it will be referred to as “one-stage joint structure”. Since the joint structure of the steel pipe according to the present embodiment is a one-stage type, the cylinder side key groove 26 is “the cylinder side key groove closest to the cylinder side bonding surface 23” and “the cylinder side key furthest away from the cylinder side bonding surface 23”. The shaft-side key groove 16 corresponds to “the shaft-side key groove closest to the shaft-side joining surface 13”.

  The rotation of the circumferential direction relative to the pin joint 10 and the box joint 20 is restricted by the rotation stop key 32. Specifically, the first groove 17 is formed by cutting out the vicinity of the shaft-side joint surface 13 in the outer peripheral portion of the shaft-side base portion 11, and the vicinity of the tube-side joint surface 23 is cut out in the outer peripheral portion of the fitting receiving portion 22. The second groove 27 is formed. The circumferential length of the first groove 17 and the circumferential length of the second groove 27 are matched. Further, the length of the first groove 17 in the axis X direction and the length of the second groove 27 in the axis X direction are also matched. In a state where the pin joint 10 is inserted into the box joint 20, the first groove 17 and the second groove 27 are aligned, and the rotation key 32 is matched so as to straddle the first groove 17 and the second groove 27. The bolt is tightened and fixed in the screw hole provided in the rotation stop key 32 and the first groove 17. Thereby, the relative movement in the circumferential direction between the pin joint 10 and the box joint 20 is restricted.

  As described above, the pin joint 10 and the box joint 20 are inserted and fitted. Note that the engagement between the pin joint 10 and the box joint 20 is enhanced by the engagement between the shaft-side concave portion 14 and the cylinder-side convex portion 24, and the engagement between the shaft-side convex portion 15 and the cylinder-side concave portion 25, and in particular bending. The rigidity against is increased. What is necessary is just to set suitably the number of the load transmission keys 31 and the number of the rotation stop keys 32 with the diameter of the upper pile 2, the lower pile 1, etc. FIG.

[Keyway position]
In the joining through the load transmission key 31 as described above, the tensile external force acting on the upper pile 2 and the lower pile 1 is the side surface of the shaft side key groove 16 or the side surface of the cylinder side key groove 26 and the side surface of the load transmission key 31. Is transmitted to the load transmission key 31 from one joint. That is, internal shear stress is generated in the shaft side keyway 16 and the cylinder side keyway 26. Based on this internal shear stress, a bending moment (secondary bending) is generated in the shaft side key groove 16 and the cylinder side key groove 26 so as to open the joint portion outward.

  The inventor conducted not only the tensile stress but also this bending moment for repeated testing and research, and by managing the “distance from the cylinder side joint surface 23 to the cylinder side key groove 26”, the “cylinder side key It has been found that the “tensile strain generated in the groove 26” can be set larger than the “tensile strain generated in the shaft-side key groove 16”. Thereby, when the joint portion is broken, the cylinder side key groove 26 can be surely broken prior to the shaft side key groove 16. Specifically, if the "distance from the cylinder-side joint surface 23 to the end-side end surface of the cylinder-side keyway 26" is 33 mm or less, it relates to the diameter and thickness of the steel pipe (upper pile 2 and lower pile 1). In other words, the “tensile strain generated in the cylinder-side keyway 26” was larger than the “tensile strain generated in the shaft-side keyway 16”.

  An example of the verification result is shown in FIG. This verification result is a verification result when the diameter of the steel pipe is 1000 mm and the wall thickness is 10 mm. In FIG. 3, the vertical axis indicates the strain in the axial keyway 16 relative to the reference strain, or the ratio of the strain in the cylindrical keyway 26 to the reference strain, and the horizontal axis indicates “cylinder-side joint surface 23. The distance BL4 "from the tip side end surface of the cylinder side keyway 26" is shown. The reference strain is a safety standard for destruction of each joint and may be set as appropriate. Hereinafter, for the sake of convenience, the reference strain value is “S”. That is, FIG. 3 shows “tensile strain generated in the cylinder side key groove 26” / S when “the distance BL4 from the cylinder side joint surface 23 to the end surface on the tip side of the cylinder side key groove 26” is changed. The “tensile strain generated in the shaft side keyway 16” / S is plotted. From FIG. 3, if “the distance BL4 from the cylinder-side joint surface 23 to the tip end face of the cylinder-side key groove 26” is 33 mm or less, “the tensile strain generated in the cylinder-side key groove 26” is “the shaft-side key It can be seen that it is larger than the “tensile strain generated in the groove 16”. This result was the same also about the other steel pipe of the diameter and thickness. As is clear from FIGS. 2 to 4, “the distance BL4 from the cylinder-side joining surface 23 to the tip-side end face of the cylinder-side key groove 26” is “the distance from the axis-side joining surface 13 to the axis-side key groove 16”. It is equal to the distance PL4 "to the lower pile side end face.

[Procedure for determining the keyway position]
Based on this result, a procedure for determining the position of the keyway has been formulated. The procedure will be described below.
(1) Step 1
The tensile stress generated in the cylinder-side key groove 26 by the action of a predetermined external force is obtained, and the thickness of the cylinder-side key groove is set so that the cylinder-side key groove 26 becomes the weakest while ensuring the reference strength of the cylinder-side key groove 26. decide.
(2) Step 2
About the thickness of another part, the dimension is determined so that it may become higher intensity | strength than the cylinder side keyway 26. FIG.
(3) Step 3
“Distance BL4 from the cylinder-side joining surface 23 to the tip-side end face of the cylinder-side key groove 26 (see FIG. 4)” (Distance PL4 from the shaft-side joining face 13 to the lower pile-side end face of the shaft-side key groove 16 (FIG. 5) See))) is set to 33 mm or less. In the present embodiment, as shown in FIG. 3, “the distance BL4 from the cylinder-side joining surface 23 to the tip-side end face of the cylinder-side keyway 26” is within the range of 33 mm or less. The “tensile strain generated in the separated cylinder-side key groove 26” does not exceed the reference strain (the ratio is 1.0 or less), but depending on the value of the reference strain, “the cylinder-side key groove furthest away from the cylinder-side joint surface 23”. In some cases, the tensile strain generated at 26 exceeds the reference strain. In this case, the lower limit is set in a range in which “the tensile strain generated in the cylinder-side key groove 26 farthest from the cylinder-side joint surface 23” does not exceed the reference strain.
(4) Step 4
Other dimensions are determined almost uniquely by the following concept. The width in the axis X direction of the cylinder side key groove 26 and the shaft side key groove 16 is uniquely determined by the width of the load transmission key 31 in the axis X direction. That is, the width of the load transmission key 31 in the direction of the axis X is set to a minimum value in consideration of the safety factor in a range in which the load transmission key 31 is not sheared by shear stress in the direction of the axis X acting on the load transmission key 31. To do. Thereby, “distance BL3 (see FIG. 4) from the cylinder-side joining surface 23 to the upper pile-side end face of the cylinder-side key groove 26” and “distance from the shaft-side joining face 13 to the tip-side end face of the shaft-side key groove 16”. PL3 (see FIG. 5) ”is determined. In addition, “the distance from the upper pile side end surface of the cylinder side key groove 26 to the step portion between the cylinder side base portion 21 and the fitting receiving portion 22” is “from the upper pile side end surface of the cylinder side key groove 26. The minimum value is set in consideration of the safety factor within a range in which the strength of the “portion up to the step portion between the tube side base portion 21 and the fitting receiving portion 22” can be secured. Thereby, “the full length BL2 of the fitting receiving portion 22 (see FIG. 4)” and “the full length of the shaft side base portion 11 (PL2)” are determined. And "the full length BL1 of the cylinder side base 21 (see FIG. 4)" and "the full length PL1 of the shaft side base 11" are uniquely determined from the relationship with the thickness of the upper pile 2 and the lower pile 1, etc. “Projection length of the cylinder-side convex portion 24 in the axis X direction”, “depression length of the cylinder-side recess 25 in the axis X direction”, “depression length of the axis-side recess 14 in the axis X direction”, and Since the “projection length in the axis X direction of the shaft-side convex portion 15” is a constant value, this also determines “the total length BL of the box joint 20” and “the total length PL of the pin joint 10”.

  The joint structure of the steel pipe designed by this procedure is very economical because the reference strength is ensured and the length of the joint portion is shorter than the conventional one.

  An example of the pin joint 10 and the box joint 20 in which the position of the key groove is determined by the above-described steps 1 to 4 is shown in FIGS. 8 and 9 show the pin joint 10 and the box joint 20 for a steel pipe pile having a tensile strength of 490 Mpa or more. Such a steel pipe is generally called “SKK490”. 10 and 11 show the pin joint 10 and the box joint 20 for a steel pipe pile having a tensile strength of 400 Mpa or more. Such a steel pipe is generally called “SKK400”.

The designation of the dimensions of each part of the one-stage joint structure was defined as follows.
1. About box joint (see FIG. 4) D: Outer diameter of upper side of cylinder side base 21 (equal to outer diameter of upper pile 2 and lower pile 1)
BD1: Inner diameter on the upper pile side of the cylinder side base 21 BD2: Inner diameter on the tip side of the cylinder side base 21 BD3: Inner diameter of the fitting receiving part BD4: Outer diameter in the second groove 27 of the fitting receiving part BD5: Fitting receiving part 22: outer diameter BL: full length of box joint 20 BL1: full length of tube side base 21 BL2: full length of fitting receiving portion BL3: distance from tube side joint surface 23 to upper pile side end surface of tube side keyway 26 BL4: 1. Distance from the tube-side joining surface 23 to the tip-side end surface of the tube-side keyway 26 About the pin joint (see FIG. 5) D: The outer diameter of the lower pile side of the shaft-side base 11 (equal to the outer diameter of the upper pile 2 and the lower pile 1)
PD1: Inner diameter on the lower pile side of the shaft-side base 11 PD2: Inner diameter on the tip side of the shaft-side base 11 PD3: Inner diameter of the shaft-side convex portion 15 of the fitting insertion portion 12 PD4: Outer diameter of the fitting insertion portion 12 PD5: Shaft side Outer diameter on the distal end side of the base portion PL: Full length of the pin joint 10 PL1: Total length of the insertion portion 12 PL2: Total length of the shaft side base portion 11 PL3: From the shaft side joining surface 13 to the distal end side end surface of the shaft side keyway 16 Distance PL4: Distance from the shaft side joint surface 13 to the lower pile side end surface of the shaft side keyway 16

  As shown in FIGS. 6 and 7, two shaft-side key grooves 16 are provided in the outer peripheral portion of the fitting insertion portion 12 along the circumferential direction of the shaft core X, and the inner peripheral portion of the fitting receiving portion 22. In addition, when the pin joint 10 is inserted into the box joint 20, two cylinder side key grooves 26 corresponding to the shaft side key groove 16 are provided around the shaft side key groove 16 and the cylinder side key groove 26. In the "two-stage joint structure" that works to form two grooves having a rectangular cross section, it is further defined as follows. The two shaft side key grooves 16 indicate a cylinder side key groove 16a close to the shaft side joint surface 13 and a shaft side key groove 16b separated from the shaft side joint surface 13 (see FIG. 7). The two cylinder-side key grooves 26 indicate a cylinder-side key groove 26a close to the cylinder-side joining surface 23 and 26b separated from the cylinder-side joining surface 23 (see FIG. 6). In the two-stage joint structure, the cylinder-side key groove 26a corresponds to “a cylinder-side key groove closest to the cylinder-side joining surface 23”, and the cylinder-side key groove 26b “a cylinder farthest from the cylinder-side joining surface 23”. The side keyway 16a corresponds to the “side keyway” and the shaft side keyway 16a corresponds to the “side keyway closest to the shaft side joint surface 13”.

1. Box joint (see FIG. 6) BL3: Distance from the cylinder side joint surface 23 to the upper pile side end face of the cylinder side keyway 26a close to the cylinder side joint surface 23 BL4: Tube side joint surface from the cylinder side joint surface 23 BL5: Distance from the cylinder-side joining surface 23 to the upper pile-side end face of the cylinder-side key groove 26b away from the cylinder-side joining surface 23 BL6: Tube-side joining 1. Distance from the surface 23 to the end surface on the front end side of the cylinder side key groove 26b away from the cylinder side joint surface 23 About the pin joint (see FIG. 7) PL3: Distance from the shaft-side joint surface 13 to the upper pile-side end surface of the shaft-side keyway 16a close to the shaft-side joint surface PL4: The shaft-side joint surface 13 to the shaft-side joint surface PL5: Distance from the shaft-side joint surface 13 to the upper pile-side end surface of the shaft-side keyway 16b away from the shaft-side joint surface 13 PL6: Shaft-side joint The distance from the surface 13 to the end surface on the front end side of the shaft-side keyway 16b away from the shaft-side joint surface 13

  In FIG. 8 to FIG. 11, the description of BL5, BL6, PL5, and PL6 is a two-stage joint structure, and the others are single-stage joint structures. In all of the one-stage joint structure and the two-stage joint structure disclosed in these figures, the “tensile strain generated in the cylinder-side key groove 26 farthest from the cylinder-side joint surface 23” It becomes larger than the “tensile strain generated in the near shaft side keyway 16”.

  In addition, in this embodiment, although the verification result of the one-stage type joint structure and an example of the one-stage type joint structure and the two-stage type joint structure are shown, the shaft side key groove 16 and the cylinder side key groove 26 are shown. If the distance from the cylinder side joint surface 23 to the cylinder side key groove 26 closest to the cylinder side joint surface 23 is 33 mm or less, “the most from the cylinder side joint surface 23” It has been mechanically demonstrated that the “tensile strain generated in the separated cylinder-side key groove 26” is larger than the “tensile strain generated in the shaft-side key groove 16 closest to the shaft-side joint surface 13”. Thus, when the joint portion is broken, the “cylinder side key groove 26 farthest from the cylinder side joint surface 23” is surely broken prior to the “shaft side key groove 16 closest to the shaft side joint surface 13”. Can do.

[Another embodiment]
In the above-described embodiment, the load transmission key 31 disposed in the cylinder-side key groove 26 is engaged across the shaft-side key groove 16 and the cylinder-side key groove 26 by the operation of the set bolt 30, and the pin joint Although the example which restrains the relative movement of 10 and the box joint 20 was shown, it is not restricted to this. Another embodiment of a configuration that restrains relative movement between the pin joint 10 and the box joint 20 will be described with reference to FIGS. 12 and 13. Except for the configuration of the key member, the configuration is the same as that of the above-described embodiment, and will not be described. In addition, the same reference numerals are given to the same components as those in the above-described embodiment.

  As shown in FIG. 12, a plurality of key insertion ports 132 communicating with the cylinder side key groove 26 are opened on the outer surface of the box joint 20. A pair of left and right arc-shaped load transmission keys 131 are inserted in the left and right directions around the axis X from the key insertion port 132 along the circumferential direction of the axis X. The cross-sectional shape in the axis X direction of the load transmission key 131 is matched to the cross-sectional shape in the axis X direction of the groove formed by combining the shaft side key groove 16 and the cylinder side key groove 26. Therefore, as shown in FIG. 13, the load transmission key 131 is engaged across the shaft side key groove 16 and the cylinder side key groove 26. Although not particularly illustrated, the load transmission key 131 is prevented from coming out of the shaft side key groove 16 and the cylinder side key groove 26 by stretching the pair of left and right load transmission keys 131. As a result, the relative movement between the pin joint 10 and the box joint 20 is restricted.

  The steel pipe joint structure according to the present invention is applicable not only to steel pipe piles but also to a joint structure in which two steel pipes such as a steel pipe sheet pile are joined in a longitudinal direction so as to be freely inserted and removed.

1 Lower pile (two steel pipes)
2 Upper pile (two steel pipes)
10 pin joint (shaft joint)
DESCRIPTION OF SYMBOLS 11 Shaft side base part 12 Insertion part 13 Shaft side joint surface 14 Shaft side recessed part 15 Shaft side convex part 16 Shaft side keyway 16a Shaft side keyway 16b Shaft side keyway 20 Box joint (tubular joint part)
DESCRIPTION OF SYMBOLS 21 Cylinder side base part 22 Fitting part 23 Cylinder side joint surface 24 Cylinder side convex part 25 Cylinder side recessed part 26 Cylinder side keyway 26a Cylinder side keyway 26b Cylinder side keyway 31 Load transmission key (key member)
131 Load transmission key (key member)

Claims (2)

A steel pipe joint structure in which two steel pipes are joined together in the longitudinal direction so that they cannot be inserted and removed,
A shaft-like joint fixed to the tip of one of the two steel pipes;
A tubular joint part fixed to the tip of the other steel pipe of the two steel pipes, and the shaft-like joint part being inserted and fitted therewith,
A shaft-side base fixed to the one steel pipe, an insertion portion extending from the shaft-side base and having an outer diameter smaller than the shaft-side base, the shaft-side base and the fitting A shaft-side joint surface which is a stepped portion with the insertion portion, a shaft-side concave portion provided around the shaft-side joint surface, and a shaft-side convex portion provided around the distal end portion of the fitting insertion portion,
A tube-side base fixed to the other steel pipe in the tubular joint, a fitting receiving portion that extends from the tube-side base and has an inner diameter larger than the tube-side base, and receives the fitting insertion portion; A cylinder side joint surface that is provided at a distal end portion of the fitting receiving portion and is in contact with the shaft side joint surface; a cylinder side convex portion that is provided around the cylinder side joint surface and engages with the shaft side concave portion; and the cylinder side A cylinder-side concave portion that is provided around a step portion between the base portion and the fitting receiving portion and engages with the shaft-side convex portion,
One or more shaft-side key grooves are provided around the outer peripheral portion of the fitting insertion portion, and the shaft-like joint portion is inserted into the cylindrical joint portion on the inner peripheral portion of the fitting receiving portion. Around one or more cylinder side key grooves corresponding to the shaft side key groove,
The shaft-side keyway and the cylinder-side keyway are arranged to engage with each other and restrain relative movement between at least the shaft-like joint portion and the tubular joint portion in the longitudinal direction. One or more key members that
When an external force is applied to the shaft-like joint portion and the cylindrical joint portion, tensile strain generated in the cylinder-side keyway that is farthest from the tube-side joint surface is caused by the shaft-like joint portion and the cylindrical joint portion. The cylinder closest to the cylinder side joint surface from the cylinder side joint surface is larger than the tensile strain generated in the shaft side key groove closest to the shaft side joint surface when the external force is applied to the cylinder side joint surface. Steel pipe joint structure with a set distance to the side keyway.   The steel pipe joint structure according to claim 1, wherein a distance from the tube side joint surface to a tip side end surface of the tube side key groove closest to the tube side joint surface is set to 33 mm or less.

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