Friction bonding pad

Abstract

To provide a doubling plate for frictional joining capable of enabling fastening from one direction by a torque shear wrench and dispensing with a nut.SOLUTION: A doubling plate 11 is used in frictional joining with a bolt while being superposed on a member to be joined 10, by using a bolt which has a shape with a torque shear stud-type fracture groove and a pin tail, and on which a male screw 21 of left-hand thread is formed on one of half parts of the bolt, a male screw 23 of right-hand thread is formed on the pin tail-side half part, and a nut 22 is engaged with the male screw 23 of right-hand thread, as a stud bolt. The doubling plate is disposed below the member to be joined 10, enables fastening from one side by being provided with a female screw 11A of left-hand thread to be engaged with the male screw 21 of left-hand thread of the bolt, and provides a function as a nut of large width across flat.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a gasket for friction joints, and particularly to a gasket used for friction joints of steel materials by high-strength bolts in building steel structures and other steel structures.

Background Art

[0002] When joining steel structure members, it is generally performed by welding or high-strength bolt friction joints.

[0003] In the case of joining by welding, the mechanical quality of the welded part is greatly influenced by the skill of the operator, and sufficient countermeasures against wind and rain are also required. To ensure the necessary mechanical quality, a great deal of management and labor are required.

[0004] Therefore, friction joints by high-strength bolts, which are relatively easy to ensure the mechanical quality of the joint, are widely adopted (Patent Document 1, Patent Document 2).

[0005] For example, there is a friction joint structure of a steel structure member using high-strength bolts as shown in FIG. 4. In FIG. 4, 40 is a steel structure member (joined member), 41 is a steel gasket, 42 is a nut, and 43 is a bolt.

[0006] In this friction joint structure, through holes 45 are provided in two steel structure members 40, and the overlapping surface (friction surface) of the steel gasket 41 overlapped on one side or both sides of the two steel structure members 40 is controlled to be in a rusty state or a plastic-treated state. Through holes 46 are provided in the steel gasket 41, and the two steel structure members 40 are connected by the tightening force of high-strength bolts 43 inserted and screwed through these through holes 45 and 46 and tightened.

[0007] In the friction joint structure shown in FIG. 4, the treatment of the friction surface is relatively simple and the manufacturing cost is also low, so it is widely used for the friction joints of H-shaped steel.

Prior Art Documents

Patent Documents

[0008] [Patent Document 1] Japanese Patent Publication No. 2006-138392 [Patent Document 2] Japanese Patent Publication No. 2015-194232 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0009] However, in the friction joint method described above, the steel frame member and the steel splice plate are clamped together with the bolt head and nut to obtain frictional force, so the bolt or nut cannot be inserted inside the member being joined. When friction joining general structural square steel pipes etc. as specified in JIS B3466, it was necessary to use a unidirectional bolt with a complex mechanism. Furthermore, since the bolt head and nut sandwich the steel frame member and the steel reinforcing plate to obtain a tightening friction force, an axial force up to the standard bolt tension is applied to the high-strength bolt in order to obtain an appropriate friction force for the friction joint structure. Therefore, the nuts for high-strength bolts that receive this axial force are specified to have a size that is one size larger than the hexagonal nuts specified in JIS B1181, with a width across flats and a height of the nominal diameter.

[0010] In view of the above problems, the present invention aims to provide a splice plate for friction bonding that enables tightening from one direction using a torque shear wrench and eliminates the need to use a nut.

[0011] Therefore, the friction splice plate according to the present invention is used when friction joining a member to be joined by overlapping a bolt, with the bolt having a shape in which a torque shear stud type fracture groove and a pintail are formed on a stud bolt, a left-hand threaded male thread formed on one half of the bolt and a right-hand threaded male thread formed on the pintail side, and a nut screwed onto the right-hand threaded male thread, and is positioned on the underside of the member to be joined, and has a left-hand threaded female thread formed thereon that is screwed onto the left-hand threaded male thread of the bolt, thereby enabling tightening from one direction and providing the function of a nut with a wide cross-section.

[0012] One of the features of this invention is that the left-hand thread of the stud bolt, which has a torque shear stud-type fracture groove and a pintail, is screwed into the left-hand thread of the splice plate, thereby enabling tightening from one direction, and also allowing the splice plate to function as a nut with a large width across flats.

[0013] This eliminates the need to use nuts on the underside of the splice plate, as in conventional methods, and enables weight reduction of the friction joint structure. Furthermore, it allows for the creation of a strength class F10T friction joint structure using commercially available tools such as torque shear wrenches, without the need for very expensive bolts such as unidirectional bolts. Furthermore, since the play screw is inserted inside the column base and other components, there is a great degree of freedom in the length of each joined member. In addition, a lightweight and highly reliable friction joint structure can be realized.

[0014] Furthermore, while the material of the splice plate is not particularly limited, using a high-hardness steel plate for the splice plate allows the desired strength to be obtained using a thin steel plate, resulting in further weight reduction of the friction joint structure. [Brief explanation of the drawing]

[0015] [Figure 1] This is a side view showing a preferred embodiment of the friction bonding splice plate according to the present invention. [Figure 2] This figure shows a stud bolt with a nut in the above embodiment. [Figure 3] This figure schematically illustrates the tightening process of the friction joint in the above embodiment. [Figure 4] This figure shows an example of a conventional friction joint structure. [Figure 5] This figure shows the failure patterns of splice plates and bolts made of SS400 steel with thicknesses of 6 mm, 9 mm, 12 mm, and 16 mm in the as-rolled state. [Figure 6] This figure shows the failure patterns of splice plates and bolts made of HT590 steel in the as-rolled, unheat-treated state, with thicknesses of 6 mm, 9 mm, 12 mm, and 16 mm. [Figure 7]This is a diagram showing the failure modes of the gusset plates and bolts of steel type EVERHARDC400L with thicknesses of 6 mm, 9 mm, 12 mm, and 16 mm that have undergone HT treatment. [Figure 8] This is a diagram showing the relationship between the thickness of the gusset plate and the ultimate load.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail based on specific examples shown in the drawings. FIGS. 1 and 2 show preferred embodiments of the gusset plate for frictional joining according to the present invention. In the figures, the frictional joining bolt 20 has a shape in which a torque shear stud type fracture groove 24A and a pigtail 24 are formed on a stud bolt. A left thread 21 is formed on one half of the bolt 20, and a right thread 23 is formed on the half side of the pigtail 24. A nut 22 that functions as a bolt head is screwed onto the right thread 23. That is, it has a shape in which a left thread with the same nominal size as the right thread is cut at the part where the head of the structural torx type high-strength bolt having a pigtail and a right thread is located.

[0017] In the joined member 10 joined by the frictional joining bolt 20, a plurality of insertion holes 10A for the frictional joining bolts 20 are formed at intervals from each other, and in the gusset plate 11 overlapped with the frictional joining bolt 20, a plurality of left thread holes 11A are formed at the same intervals as the insertion holes 10A of the joined member 10.

[0018] Generally, for the frictional joining of steel structures by high-strength bolts, a set of a structural torx type high-strength bolt hexagonal nut, a flat washer, and a torx wrench is widely used because of its excellent characteristics such as ease of construction and stability of the tightening axial force.

[0019] When performing frictional joining, a high-strength bolt hexagonal nut 22 is set on the pigtail 24 side of the frictional joining bolt 20 shown in FIG. 2.

[0020] Next, as shown in Figure 3, the splice plate 11 is placed on top of the member to be joined 10, the friction joint bolt 20 is inserted from the top of the member to be joined 10 through the washer 25, and the left-hand thread 21 of the friction joint bolt 20 is screwed into the left-hand threaded bolt hole (splice) 11A of the splice plate 11.

[0021] Finally, the tightening parts A and B of the torque wrench are placed over the pintail 24 and nut 22 of the friction joint bolt 20 and rotated to break the pintail 24. This tightens the joined member 10 between the left-hand thread 21, which has a splice cut into it in place of the torque shear bolt head, and the hexagonal nut 22, completing the friction joint.

[0022] The tightening process to ensure the tightening axial force on the friction joint bolt 20 using a torque shear wrench proceeds in the following steps, as shown in Figure 3. 1. The pintail gripping jig A on the core of the torque shear wrench grips the pintail of the friction joint bolt 20. Grasp part 24 and rotate it counterclockwise while keeping nut 22 in place. 2. The counterclockwise rotation of the friction joint bolt 20 causes the seating surface of the splice plate 11 and the seating surface of the nut 22 to sandwich the fastened member 10. 3. The frictional resistance of the seating surface of the splice plate 11 stops the counterclockwise rotation of the pintail 24. 4. Once the rotation of the pintail gripping jig A has stopped, it functions as a reaction force receiver for the rotation of the nut 22. 5. When the pintail gripping jig A stops, the nut gripping jig B rotates clockwise, causing the nut 22 to tighten the member to be joined 10. When a predetermined tightening axial force is generated in the friction joining bolt 20, the pintail 24 breaks, and the tightening is completed.

[0023] (test) As basic data for the practical application of threaded splice plates, we cut female threads into SS400 and high-hardness steel plates commonly used for splice plates and compared their limit plate thicknesses using guaranteed load tests (tensile method). The tests used SS400, HT590, and EVERHARDC400LE steel grades, with test specimen sizes of 75 x 75 mm, plate thicknesses of 6 mm, 9 mm, 12 mm, and 16 mm, and M20 right-hand threads with screw pilot hole diameters of 17.294 / 17.744. Twelve F10T M20 x 150 hexagonal bolts were used as test bolts. The test method involved applying an axial tensile load according to JIS B1052-2 Figure 1 using a 1000 KN universal testing machine, and observing the maximum load reached and the failure morphology after the test. The results are shown in Table 1, and the failure morphology of the test specimens is shown in Figures 5 to 7.

[0024] [Table 1]

[0025] 1. F10T M20 bolt, effective cross-sectional area 245 mm² 2 The thickness of the splice plate required to achieve bolt fracture (250KN) can be reduced as the hardness of the splice plate increases. Specifically, The required thickness for SS400 is 17mm (113%), for F10T it is 15mm (100%), for HT590 it is 13mm (80%), and for EVERHARDC400LE it is 11mm (73%).

[0026] The relationship between the thickness of the splice plate and the resulting load was investigated. Figure 8 shows the results, with the splice plate thickness on the horizontal axis (mm) and the resulting load (KN) on the vertical axis.

[0027] 2. In the case of SS400 steel, screw threads coming loose from the splice plate are due to shearing of the threads in the splice plate. 3. In EH, screw threads coming loose from the splice plate are caused by shearing of the bolt threads. 4. When shear occurs in the bolt threads, the shear stress ratio decreases.

[0028] Next, in order to realize a friction joint structure, we considered the material and required thickness of the threaded splice plate. Bolt and nut material Friction joint bolts are made of structural boron steel that has been hardened and tempered to over 1000 MPa, while friction joint nuts are made of machine structural carbon steel that has been hardened and tempered to approximately HRC25.

[0029] The fastening structure consisting of a bolt and nut that withstands the axial force of the bolt loses its function through the following process. 1. The bearing surface of the nut receiving the load widens, reducing the engagement height of the threads on the bolt and nut. 2. The threads of a bolt or nut will be sheared when the shear strength, determined by the hardness at the point where the threads of the bolt or nut engage, reaches the shear strength of the bolt or nut.

[0030] In this invention, which involves cutting threads into a splice plate, the expanding diameter load applied to the thread flank surface is received over a larger area compared to the two-sided width of the nut, thus suppressing the reduction in the engagement height due to the widening of the effective thread diameter. The experimental results confirming this effect are shown below. [Experiment 1] A splice plate was created by cutting M20 threads into SS400 general structural rolled steel, which has a thickness of 15.6 mm, a width of 75 mm, a depth of 75 mm, and a hardness of HRB74. An M20 bolt with a 1000 MPa class tension was fitted into the splice plate, and the fracture mode was confirmed by tensile testing. The threads on the splice plate were sheared under a load of 235 kN. This shear load is 129% of the standard bolt tension of 182 kN for an F10T M20 bolt. [Experiment 2] A splice plate was created by cutting M20 threads into HT590, a special rolled steel material with a thickness of 11.9 mm, a width of 75 mm, and a depth of 75 mm, and a hardness of HRB90. An M20 bolt with a 1000 MPa class tension was fitted into the splice plate, and the fracture mode was confirmed by tensile testing. The threads of the splice plate and the bolt were simultaneously sheared under a load of 230 kN. This shear load is 126% of the standard bolt tension of 182 kN for an F10T M20 bolt. [Experiment 3] A special rolled steel material EH400l, with a thickness of 11.8 mm, a width of 75 mm, a depth of 75 mm, and a hardness of HRC38, was used to create a splice plate with M20 threads. An M20 bolt with a 1000 MPa class tension was fitted into the splice plate, and the fracture mode was confirmed by tensile testing. Under a load of 258 kN, the threads on the splice plate showed no abnormalities, but the bolt threads sheared. This shear load is 141% of the standard bolt tension of 182 kN for an F10T M20 bolt.

[0031] As described above, by reducing the mass of the nuts, it is possible to achieve performance equivalent to that of conventional friction joint structures using hardened and tempered carbon steel for machine structural use as nuts, using general structural rolled steel in its as-rolled state. [Explanation of Symbols]

[0032] 10 Parts to be joined 11 Plate 11A Left-hand female thread 20 volts 21 Left-hand threaded male screw 22 nuts 23 Right-hand threaded male screw 24 Pintail

Claims

1. A friction joint structure comprising a pair of members to be joined (10) and a splice plate (11) superimposed on at least the back surface thereof, wherein the two are joined by friction by fastening them together with joining bolts through the through holes thereof, A friction joint structure characterized in that a through hole without threads is left on the side of the member to be joined (10), while a female thread (11A) is formed in the through hole on the side of the splice plate (11) corresponding to the through hole, so as to enable tightening from one direction and to give it the function of a nut with a large width across flats.

2. The friction joint structure according to Claim 1, wherein the splice plate (11) is made of high-hardness steel plate, and the friction joint structure can be made lighter compared to SS400 due to its function as a nut with a large width across flats.

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