JP7199152B2 - Steel pipe connecting mechanism - Google Patents

Description

The present invention comprises a pin joint provided at one end of a steel pipe body, a box joint provided at the other end, an outward groove provided around the outer peripheral surface of the pin joint, and an inner peripheral surface of the box joint. Also, it relates to a steel pipe coupling mechanism provided with a load transmission key arranged so as to straddle an inward groove provided around the outward groove corresponding to the outward groove.

Patent Document 1 discloses a pin joint provided at one end of a steel pipe body, a box joint provided at the other end, an outward groove provided around the outer peripheral surface of the pin joint, and an inner groove of the box joint. A longitudinal splicing device for a steel pipe sheet pile or the like is disclosed, in which a load transmission key is arranged on the peripheral surface so as to straddle the inward grooves provided around the outward grooves corresponding to the outward grooves.

Japanese Patent No. 3336430

However, in the conventional splicing device, the force applied from the load transmission key to the outward groove and the force applied from the load transmission key to the inward groove stress the corners of the outward and inward grooves formed at right angles by cutting. The distribution is disturbed and the stress increases locally (stress concentration).

In pin joints and box joints, the thickness of the part where outward grooves and inward grooves are provided is relatively thinner than the other parts, and this is a structural weakness. Some thickness is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly economical steel pipe connecting mechanism.

In order to achieve the above object, the steel pipe connection mechanism according to the present invention is characterized by: a pin joint provided at one end of a steel pipe body; a box joint provided at the other end; A steel pipe connection mechanism comprising an outward groove provided around an outer peripheral surface and a load transmission key arranged so as to straddle an inward groove provided around the inner peripheral surface of the box joint corresponding to the outward groove. The inward groove has a depth capable of accommodating the entire load transmission key in the thickness direction, and the corners of the outward groove and the inward groove have a radius of curvature ρ [mm] is the following formula (1) (where t is the thickness [mm] in the cross section of the load transmission key) and formula (2) (where a is the cross section of the load transmission key half the length of the diagonal [mm]).

In a steel pipe connection mechanism, the thickness of each joint where the load transmission key is arranged is thinner than the other parts, which is a structural weakness, and the outward groove of the pin joint and the inward groove of the box joint are stress concentration. It can be the starting point of fracture due to

Therefore, by setting the radius of curvature ρ [mm] of the corners of the outward grooves and the corners of the inward grooves as described above, stress concentration can be alleviated.

Relief of stress concentration reduces the local force acting on the outward and inward grooves. The economy of the coupling mechanism can be enhanced.

Relieving the stress concentration reduces the local force acting on the outward grooves and the inward grooves. The economic efficiency of the steel pipe connection mechanism can be improved.

However, the larger the radius of curvature of the corners of the outward and inward grooves, the narrower the bearing surfaces of the load transmission key and the outward and inward grooves. will decline. Therefore, the upper limit of the curvature radius ρ [mm] is set as described above.

In the present invention, it is preferable that the load transmission key is configured such that the chamfers C [mm] provided at the four corners in the cross section satisfy the following formula (3).

According to the above-described configuration, the load transmission key is chamfered with a radius of curvature equal to or greater than the radius of curvature of the corners of the outward and inward grooves. The depth of the outward grooves and the depth of the inward grooves can be made as shallow as possible. The larger the chamfers provided at the four corners of the load transmission key in the cross section, the narrower the areas of the bearing surfaces of the load transmission key and the outward and inward grooves, resulting in the load transmission efficiency of the load transmission key. decreases. Therefore, the upper limit of the chamfer C [mm] is set as described above.

In the present invention, each of the outward groove and the inward groove is single, and the length Lb [mm] of the box joint and the distance L [mm] of the inward groove from the tip of the box joint are given by the following formula: (4) (where My is the bending moment [kN m] acting on the box joint, and Py is the bending load [N] applied to the tip of the box joint), and formula (5) ( However, T is the compressive load [N] acting from the load transmission key to the bearing surface of the inward groove from the tip of the box joint, and d is the depth [mm] of the inward groove. preferably configured.

It is known that the secondary bending in the steel pipe connection mechanism is greatly affected by the positions of the outward grooves and the inward grooves in the axial direction of the steel pipe connection mechanism. However, conventionally, there were no indicators for designing the axial length of the pin joint and the box joint and the position of the load transmission key. , or the position of the load transmission key may not be arranged at an appropriate position.

According to the above configuration, it is possible to reduce the axial length of the pin joint and the box joint while suppressing the secondary bending of the steel pipe connection mechanism, and it is possible to arrange the load transmission key at an appropriate position. It became so. The upper limit of the bending moment My [kN·m] is set as described above. The value of 216 [kN·m] is a threshold value obtained from experiments and analyses. In addition, since the stress concentration is relieved, the local force acting on the groove is reduced, so that the load transmission key can be further improved, thereby improving the economic efficiency of the steel pipe connection mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the steel-pipe pile provided with the steel-pipe connection mechanism which concerns on this invention. FIG. 4 is an enlarged view of a main part of the steel pipe connecting mechanism; FIG. 4 is an explanatory diagram of a main part of a box joint; 4 is a graph explaining the relationship between the radius of curvature and the stress concentration factor;

A steel pipe connecting mechanism according to an embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, steel pipe piles 1 (1A, 1B) are provided by welding a small-diameter cylindrical pin joint 3 to one pipe end of a steel pipe body 2 such as a cylindrical spiral steel pipe. A cylindrical box joint 4 into which a pin joint 3 can be fitted is provided by welding to the other pipe end of the tube 2, and is formed in a cylindrical shape having a substantially constant outer diameter over the entire length.

A plurality of steel pipe bodies 2 are connected along the axial direction by a steel pipe connecting mechanism A according to the present invention. Hereinafter, the steel pipe connecting mechanism A according to the present invention will be described in detail, focusing on the pin joint 3 and the box joint 4. As shown in FIG.

As shown in FIGS. 1 and 2, the pin joint 3 includes a base cylinder portion 30 having substantially the same diameter as the outer diameter of the steel pipe body 2 and a fitting portion extending from the base cylinder portion 30 and having a smaller diameter than the base cylinder portion 30. and an insertion portion 31 . An outer peripheral surface 31a of the inserting portion 31 is provided with an outward groove 32 that can be engaged with a load transmission key 7, which will be described later. The outward groove 32 has a depth that can accommodate half of the load transmission key 7 in the thickness direction.

The box joint 4 is provided with a fitting portion 41 having substantially the same diameter as the outer diameter of the steel pipe body 2 . An inner peripheral surface 41 a having a shape corresponding to the outer peripheral surface 31 a and capable of receiving the fitting insertion portion 31 of the pin joint 3 is formed on the inner periphery of the fitting receiving portion 41 . A line of inward grooves 42 capable of accommodating the load transmission key 7 is formed in the inner peripheral surface 41 a at a position corresponding to the outward grooves 32 . The inward groove 42 has a depth capable of accommodating the entire thickness of the load transmission key 7 .

As shown in FIG. 2, the curvature radius ρ [mm] of the corner portion 32c of the outward groove 32 and the corner portion 42c of the inward groove 42 is given by the following formula (1) (where t is the cross section of the load transmission key 7). thickness [mm]) and formula (2) (where a is half the length [mm] of the diagonal line in the cross section of the load transmission key 7). .

In this embodiment, the load transmission key 7 has a height l of about 17.6 [mm] in the cross section, a thickness t of about 10.5 [mm] in the cross section, and a diagonal line in the cross section. The half length a of the length of is about 10.2 [mm]. The relationship between the radius of curvature ρ [mm] and the stress concentration factor α at this time is shown in the table below. Based on this table, FIG. 4 shows a graph in which ρ/a is plotted on the horizontal axis and the stress concentration factor α is plotted on the vertical axis. The stress concentration factor α was calculated from the following formula (6).

As shown in the above table and FIG. 4, as the radius of curvature ρ [mm] increases, the stress concentration factor α decreases exponentially, and when the radius of curvature ρ is 1.0 [mm] , 0.4 [mm], the stress concentration factor α is lower. Also, when the value of ρ/a is 0.6 or more, the effect of lowering the stress concentration factor is small. In this embodiment, since the thickness t of the load transmission key 7 is 10.5 [mm], the curvature radius ρ [mm] must be smaller than 5.25 [mm]. From the above, it can be seen that the radius of curvature ρ [mm] is preferably about 1.0≦ρ≦3.0.

In the steel pipe connection mechanism A, the pin joint 3 and the box joint 4 are thinner at the portions where the load transmission keys 7 are arranged than at the other portions, which is a structural weak point. 32c and the corner 42c of the inward groove 42 can be the starting point of fracture due to stress concentration.

Therefore, by setting the radius of curvature ρ [mm] of the corner portion 32c of the outward groove 32 and the corner portion 42c of the inward groove 42 as described above, stress concentration can be alleviated.

It is necessary for the portions of the outward grooves 32 of the pin joint 3 and the inward grooves 42 of the box joint 4 that the local forces acting on the outward grooves 32 and the inward grooves 42 are reduced by alleviating the stress concentration. Since the plate thickness can be reduced, the economic efficiency of the steel pipe connecting mechanism A can be improved.

In other words, the relaxation of the stress concentration reduces the local force acting on the outward groove 32 of the pin joint 3 and the inward groove 42 of the box joint 4, which means that when the plate thickness remains the same, , the number of stages of the load transmission keys 7 can be reduced, so the economic efficiency of the steel pipe connecting mechanism A can be enhanced.

However, the larger the radius of curvature ρ [mm] of the corner portion 32c of the outward groove 32 and the corner portion 42c of the inward groove 42, the larger the area of the bearing surfaces of the load transmission key 7 and the outward groove 32 and the inward groove 42. It becomes narrower, and the efficiency of load transmission by the load transmission key 7 is lowered. Therefore, the upper limit of the curvature radius ρ [mm] is set as described above. In addition, it is preferable that the radius of curvature ρ≦3.0 [mm].

In this embodiment, each of the outward groove 32 and the inward groove 42 is single, and therefore the load transmission key 7 is single. Since the stress concentration is relieved, the local force acting on the outward grooves 32 and the inward grooves 42 is reduced, so that the load transmission key 7 can be made one-tiered.

The axial lengths of the outer peripheral surface 31a and the inner peripheral surface 41a, the positions of the outward grooves 32 on the outer peripheral surface 31a, and the positions of the inward grooves 42 on the inner peripheral surface 41a can be set as follows. Regarding the axial lengths of the outer peripheral surface 31a and the inner peripheral surface 41a, the length of one corresponds to the length of the other, and the position of the outward groove 32 on the outer peripheral surface 31a and the position of the inward groove 42 on the inner peripheral surface 41a Since one position corresponds to the other position, the axial length of the inner peripheral surface 41a and the position of the inward groove 42 on the inner peripheral surface 41a will be described here.

As shown in FIG. 3, the length Lb [mm] of the box joint 4 and the distance L [mm] of the inward groove 42 from the tip of the box joint 4 are given by the following formula (4) (where My is the box joint 4 and Py is the bending load [N] applied to the tip of the box joint 4.), and Equation (5) (where T is the inward direction from the tip of the box joint 4 is the compressive load [N] acting from the load transmission key 7 on the bearing surface of the groove 42, and d is the depth [mm] of the inward groove 42).

The bending moment My [kN·m] is configured to be within 216 [kN·m]. 216 [kN·m] is a threshold obtained from experiments and analysis. By configuring as described above, the lengths of the pin joint 3 and the box joint 4 in the axial direction can be shortened while suppressing the secondary bending of the steel pipe connection mechanism A, and the load transmission key 7 is also suitable. Can now be placed in position.

A plurality of screw holes 43 are provided in the inward groove 42 at predetermined intervals in the circumferential direction of the box joint 4 so as to communicate with the outer peripheral surface of the box joint 4 . A set bolt 8 is screwed into the screw hole 43 . The set bolt 8 is screwed with the load transmission key 7 inside the inward groove 42 .

The load transmission key 7 is an arc-shaped key member having a curvature along the curvature of the outward groove 32 , and is provided in plurality at predetermined intervals in the circumferential direction of the outward groove 32 . As shown in FIG. 2, the load transmission key 7 is configured such that the chamfers C [mm] provided at the four corners in the cross section satisfy the following formula (3).

Since the load transmission key 7 is chamfered C [mm] with a size equal to or greater than the radius of curvature ρ [mm] of the corners 32c of the outward groove 32 and the corners 42c of the inward groove 42, the four corners of the load transmission key 7 are Since there is no contact with the corner portion 32c of the outward groove 32 or the corner portion 42c of the inward groove 42, the depth of the outward groove 32 and the depth of the inward groove 42 can be made as shallow as possible. The larger the chamfers C [mm] provided at the four corners of the load transmission key 7 in the cross section, the narrower the area of the pressure-bearing surface between the load transmission key 7 and the outward grooves 32 and the inward grooves 42 . , the load transmission efficiency of the load transmission key 7 is lowered. Therefore, the upper limit of the chamfer C [mm] is set as described above.

Each load transmission key 7 can be moved from the housed position in the inward groove 42 to the position straddling the outward groove 32 and the inward groove 42 of the insertion portion 31 by rotating the set bolt 8 screwed thereto. When it is moved forward and rotated in the opposite direction (leftward), the load transmission key 7 retreats from the position straddling the outward groove 32 and the inward groove 42 to the accommodation position in the inward groove 42 .

As shown in FIG. 1, in order to connect the steel pipe pile 1A and the steel pipe pile 1B, the steel pipe pile 1B is lifted by a crane, transported directly above the steel pipe pile 1A and lowered, and the pin joint 3 on the side of the steel pipe pile 1B is connected to the steel pipe pile. By inserting into the box joint 4 on the 1A side, the steel pipe pile 1A and the steel pipe pile 1B are fitted. After that, the set bolt 8 is screwed to push the load transmission key 7 accommodated in the inward groove 42 toward the outward groove 32 . As a result, the load transmission key 7 straddles the outward groove 32 and the inward groove 42, and the steel pipe pile 1A and the steel pipe pile 1B are connected through the load transmission key 7 in a non-removable manner. In addition, if necessary, a rotation suppression key may be arranged so as to straddle the pin joint 3 and the box joint 4 to prevent the steel pipe pile 1A and the steel pipe pile 1B from rotating relative to each other around the axis. good.

The steel pipe connection mechanism A according to the present invention is not limited to the steel pipe pile 1 as described above, but is a joint that can be connected to joints that are similarly provided on adjacent steel pipe sheet piles along the outer peripheral surface of the steel pipe body 2 along the longitudinal direction. It can also be adopted for steel pipe sheet piles provided with.

The above-described embodiments are all examples of the present invention, and the present invention is not limited by the description, and the specific configuration of each part can be appropriately changed and designed within the range in which the effects of the present invention are exhibited. be.

2: Steel pipe body 3: Pin joint 4: Box joint 7: Load transmission key 31a: Outer peripheral surface 32: Outward groove 32c: Corner 41a: Inner peripheral surface 42: Inward groove 42c: Corner A: Steel pipe connection mechanism

Claims (3)

A pin joint provided at one end of a steel pipe body, a box joint provided at the other end, an outward groove provided around the outer peripheral surface of the pin joint, and an outer groove formed on the inner peripheral surface of the box joint. A steel pipe connection mechanism provided with a load transmission key arranged so as to straddle an inward groove circumferentially provided corresponding to the groove,
The inward groove has a depth capable of accommodating the entire thickness direction of the load transmission key, and
The curvature radii ρ [mm] of the corners of the outward grooves and the corners of the inward grooves are given by the following formula (1) (where t is the thickness [mm] of the cross section of the load transmission key) and A steel pipe connection mechanism configured to satisfy the formula (2) (where a is a length [mm] that is half the length of a diagonal line in the cross section of the load transmission key).

2. The steel pipe connection mechanism according to claim 1, wherein the load transmission key is configured such that chamfers C [mm] provided at four corners in the cross section satisfy the following formula (3).

Each of the outward groove and the inward groove is one line,
The length Lb [mm] of the box joint and the distance L [mm] of the inward groove from the tip of the box joint are given by the following formula (4) (where My is the bending moment [kN m], and Py is the bending load [N] applied to the tip of the box joint. 3. The steel pipe connecting mechanism according to claim 1 or 2, wherein the compressive load [N] acting from the load transmission key and d is the depth [mm] of the inward groove.

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