JPS60253650A - Screw joint of steel rod - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a threaded steel bar joint that is useful mainly in the fields of civil engineering and construction, and particularly to a joint for a threaded steel bar that is provided with a male thread on the end surface or the entire length surface. The present invention relates to a threaded joint in which two steel rods are connected to each other by a sleeve (coupler) having internal threads on the inside, and a filler (grout material) is injected into the gap between the threads.

<Background technology> In recent years, in order to cope with the difficulty in securing skilled welders and the demand for higher efficiency in on-site work, steel bars with male threads provided only on the end surface or over the entire length are threaded together using a sleeve. A technology for connecting steel bars that eliminates on-site welding work by joining them has been attracting a lot of attention, especially for reinforced concrete structures (for example, [Sumitomo Metals J
Vot, 29°A4.0ct-197'i', 35th ~
(See page 47).

By the way, the above-mentioned steel bar joint method has a significant advantage in that it eliminates welding work at the construction site, but on the other hand, it also suffers from the unavoidable gap between the male and female threads. However, there remained a major problem in countermeasures against this problem. In particular, in the case of steel bars where the male thread on the outer peripheral surface is simultaneously formed during hot rolling, the dimensional accuracy of the thread is not necessarily high, and a relatively large gap may occur between it and the female thread on the inner surface of the joint sleeve. Therefore, if a joint in this condition is used in a reinforced concrete structure, the slight external force C due to the bend will cause the joint to deform, which tends to cause cracks in the concrete at the joint location. Met.

Conventionally, in order to prevent such rattling in threaded joints, lock nuts 2, 2 are screwed onto both ends of the joint sleeve l, as shown in FIG. Torque is applied to the steel rod 3 of the joint,
3, a method of introducing prestress (torque method) has been attempted.

However, this torque method requires two lock nuts, and when the diameter of the steel rod becomes thicker, a special tightening tool is required to apply a predetermined large torque, so there is a preparatory processing cost. The construction costs were high, and the practical benefits were not that great.

Therefore, the present inventors have developed a steel rod 3,3 as shown in FIG. Filler material such as non-shrink cement paste or resin is injected into the gap between the threads of the joint sleeve L and the fitting sleeve L through the filler injection hole 4.
proposed a threaded joint (hereinafter referred to as the grouting method) (see Utility Model Application Publication No. 54420/1983 and
(See Publication No. 112618). Threaded joints obtained by this grouting method have come to be widely adopted in the civil engineering and construction fields.

However, even with threaded joints made by the grouting method, which have demonstrated sufficiently reliable performance in a variety of conventional reinforcing structures, depending on the manufacturing conditions or under conditions where the operating temperature changes significantly, etc. It has become clear through research conducted by the present inventors from various angles, including performance tests, that the stiffness of the joint may be slightly lower than the expected value. be.

<Purpose of the Invention> The purpose of the present invention is to achieve even higher reliability without causing any inconvenience even in the face of any particular hindrances, i.e., to achieve a rigidity equivalent to that of a steel bar body under any conditions. The main purpose is to stably and reliably obtain threaded joints with a rigidity of 200 mm or more, and to completely prevent accidents in structures using steel rods due to insufficient rigidity of the joint.

By the way, in the case of steel rod joints, 5.If the elastic modulus of the steel rod body is EO, and the apparent elastic modulus of the joint is E, then 1For example, as stipulated in the civil engineering and construction standards, E/Eo≧
If it satisfies 09, it is considered for practical dirt floor purpose.

<Structure of the Invention> Now, the above-mentioned problem in threaded joints of steel rods using joint sleeves is the problem of stiffness of the joint portion where the joint sleeve is clogged. The rigidity of the joint is determined by the amount of deformation of the sleeve and steel rod in response to the applied load and the amount of removal of the steel rod from the sleeve.

However, since the material and cross-sectional area of the joint sleeve are selected so that its rigidity is equal to or higher than that of the steel rod, the amount of deformation of the steel rod and sleeve itself can be considered to be constant, and therefore the joint part The stiffness of the steel rod ultimately depends on the amount of ejection of the steel rod from the joint sleeve when axial tensile stress is applied.

In joints made using the grout method, the amount of removal is determined by the state of engagement between the male thread of the steel rod and the female thread of the sleeve (the degree of engagement) and the properties of the filled filler. .

The inventors of the present invention have confirmed the above facts based on years of research and usage results regarding threaded joints for steel bars using the grouting method, and have further analyzed the research results and usage results in more detail, and have continued their research. By correlating the engagement condition of the joint thread and the elastic modulus of the filler and setting it within a specific range, the above E/Eo≧09 can be obtained under all usage conditions of the steel bar.
We have obtained new knowledge that the conditions for this will always be stably satisfied.

That is, as shown in FIG. 4, which is a schematic explanatory diagram of the main parts of a threaded joint obtained by the 5-grout method.

LG, axial distance between male and female threads (e).

h: Thread height of male thread (cIrL).

As, average cross-sectional area of the steel bar (cr!), AR: total area (cr& ) of the male thread on one side facing the female thread in the axial direction (the part indicated by the symbol f in Fig. 4), ER: filling after hardening The elastic modulus of the material at the joint operating temperature (kg/crl) is: LG/h≦3.0 ・・・・・・■ AR/AS≧02 ・・・・・・■ ER/LG≧5 X 10 It has been found that the above object can be achieved when the conditions (2), (2) and (2) are simultaneously satisfied.

As is clear from FIG. 4, the above-mentioned condition e indicates the allowable upper limit of the gap between the male screw and the female screw, that is, the clearance.

In manufacturing a threaded steel bar, especially when it is manufactured by hot rolling, it is advantageous to have a larger allowable upper limit value. Further, the work of connecting steel rods at a construction site is also more efficient as the looseness between the rod and the coupler (coupling sleeve) is larger.

However, if this "reduction" becomes too severe and the ratio of LG/h exceeds 3.0, tensile stress in the axial direction will act on the steel bar even after filling the gap between the male threads with filler. When this occurs, the amount of extraction increases. That is, as will be described later, even if a filler with a high elastic modulus is used, if the value of the axial distance (LG) is large, the amount (thickness) of the filler existing between both screws will be large. Not only does the total amount of deformation increase, but when the value of LG/h is large, the filler material between both screws stretches into the space between the crest of the male screw and the valley of the female screw.
This results in deformation and an increase in axial displacement. Therefore, although the appropriate value differs depending on the type of filler that can satisfy the condition of E/E0≧0.9, it was confirmed that it should be 3.0 or less from the actual situation of manufacturing and using steel bars. . Of course, the larger this value is, the more it is necessary to use a filler with a larger elastic modulus, so it is more desirable that LG/h≦1.5.

On the other hand, if the axial distance (LG) is made small, the amount of pull-out when axial tensile stress is applied to the steel bar can be reduced even if a resin with a low elastic modulus is used, but When using a steel bar with a male thread formed in the process, the large variation in dimensional accuracy makes it difficult for the male thread to mesh with the female thread of the sleeve. Needless to say, there is a limit to reducing the axial distance (Lo, 1) since this will result in an increase in cost.

The condition (2) defines the effective area where the male thread and the female thread are engaged and receive stress.

When the portion indicated by the symbol f in Fig. 4 becomes relatively small, the load per unit area of the screw thread increases when tensile stress is applied to the steel rod, and the load per unit area of the filler interposed between both screws increases. The load will also increase. And AR/As2
The condition O,2 prevents a decrease in E (apparent elastic modulus of the joint) due to deformation of the thread itself and deformation of the filler between them, and ensures that E/Eo≧0.9 as described above. This is a necessary condition to ensure this.

Note that since AR is the total sum of the parts indicated by the symbol f in FIG. 4, it can be adjusted by adjusting the length of the joint sleeve, and the longer the joint sleeve is lengthened, the greater the value of AR/As will be.

In order to stably ensure E/Eo≧0.9 in threaded joints using the grouting method, it is important to satisfy the conditions ■ and ■ mentioned above, and also satisfy the condition shown in ■ above. It is.

The condition (2) defines the relationship between the elastic modulus of the filler after hardening and the above-mentioned distance between both screws. In other words, the larger the axial distance (Lo ) is, the higher the elastic modulus must be used. On the other hand, in order to reduce the axial distance CLG ), the steel bar must be hot rolled Since there is a limit to how much it can be made, it is not easy to determine the appropriate value.

The present inventors have investigated the relationship between the elastic modulus of a large number of fillers at the steel bar operating temperature and the conditions (1) and (2) above, and found that E/Eo≧
They discovered that this is an essential requirement to always ensure 0.9.

The present invention has been made based on the above findings, and provides a threaded joint for a steel rod, as shown in the schematic explanatory view of the main part of FIG. , 3 are butt-connected by a sleeve 1 having a female thread on the inner surface to be screwed together, and a filler material 5 is filled in the gap between the male thread and the female thread that are screwed together. Axial distance of gap with female thread (LG:
l, steel bar 3゜3 Each end of the male thread on one side facing the male thread in the axial direction (total area CAR: l, and the elastic modulus [ER] of the filler material 5 after hardening at the joint operating temperature
La/h≦30...■ AH/A BaO,2,, song, ■ E R/L Ga4 The steel rod itself has its own characteristics under all of the above usage environments.

In addition, in the threaded joint of this invention, the axial distance of the gap between the male thread and the female thread [LG:], the total area of one side of the male thread facing the female thread in the axial direction at each end of the steel bar [AR],
and the elastic modulus of the filler after curing at the joint usage temperature (
:ER) are limited to the conditions shown in formulas (1), (2), and (0) above, respectively, because if any one of them deviates from these conditions, it will not be possible to stably secure the desired joint rigidity. It is effective to adjust the relationship between the axial distance [LG] and the thread height (h) of the male thread to LG/h≦1.5 in order to ensure even higher joint rigidity.

Further, the filler may be any material as long as it satisfies the formula (2) shown above, but for example, epoxy resin, silicone resin, phenol resin, polyethylene resin, early-strength cement, or metal It is best to choose from among those that have increased fire resistance, heat resistance, and water resistance by mixing powder or the like. However, among these materials, the elastic modulus of some materials rapidly decreases when the temperature reaches about 130.degree. C., so it is necessary to carefully select the material taking into consideration the environment in which the joint will be used.

FIG. 1 is a schematic diagram showing an embodiment of a threaded joint for steel bars according to the present invention.

In Fig. 1, a steel rod 3 with a male thread formed at the connecting end.
．． 3 is a female thread that is screwed into the male thread, and is butt-joined by a coupler (coupling sleeve) 1 threaded on the inner surface of the female thread, and a filler material 5 such as resin is placed between the coupler 1 and the steel bars 3, 3. Filled. A filler injection hole 4 is provided at the center of the coupler 1 in the axial direction.

And, between the male thread on the end face of the steel rod and the female thread on the inner surface of the coupler, a filler material is placed between the male thread and the female thread on the inner surface of the coupler to facilitate the meshing work of the male thread and the female thread at civil engineering and construction sites, and to make it easier to fill the gap between the male thread and the female thread. It is also necessary to provide an appropriate gap in the axial direction, but if this gap is too large, the amount of elastic deformation of the filler will become excessive and the rigidity of the joint will decrease, so The maximum value of the axial distance is 3.0 times or less the crest height of the male thread of the steel bar.

Now, when assembling this joint, 1. Coupler 1.
The steel rods 3, 3 are screwed together from both ends of the coupler 1, and the ends of the rods are inserted into the center of the coupler 1. next.

While maintaining this state, a filler is injected and filled between the threads of the steel rod and the coupler through the injection hole 4, and the filler is waited for to harden.

In this way, the assembly of the joint is completed very easily, but the filler to be used should be, for example, an epoxy resin whose elastic modulus after curing satisfies the condition of the above equation 0 (the elastic modulus at room temperature is 5. OX 10' p/crl, 132°C
Several types are known, such as those with an elastic modulus of 0.2 x 10'kl/d at room temperature), or heat-resistant silicone resins (with an elastic modulus of 3.0 x 10'kl/cIl at room temperature). Several types are known, such as one having an elastic modulus of 16×lo'kg/cIl at 132° C.), etc. are used.

In addition, the total area [AR] of the male thread on one side of the steel rod end facing the female thread of the coupler in the axial direction can be adjusted by changing the coupler length, thread height, age, or thread pitch 1. be done.

Hereinafter, the performance of the threaded joint of the present invention will be specifically explained using examples.

<Example> The following four types of steel rods were used, and after forming the threads thereof to a practical extent, they were combined with a coupler (joint sleeve) to form a threaded joint, and a rigidity test was conducted.

D25...Average diameter: 25.4 stations, h:o, z儂.

D32...Average diameter: 31.8mm, h: 0.24mm.

D 41...Average diameter: 41.3M, h:
0.32cfILID 51...Average diameter: 50
．． 8m, h: 0.45cz0 The elastic modulus [E) of these steel bars are all approximately 2. OX 106kl
/crlL.

In addition, the following three types of fillers were used.

A...Epoxy resin (product name: Sumikadine).

B...Silicone resin, C...Metal plastic (product name: Multimetal).

Table 1 shows the test conditions and test results. In addition, the test temperature: 132℃ is located in the reactor chamber.
This assumes the usage conditions of reinforcing bars in structures that are affected by heat.

As is clear from the results shown in Table 1, LG/
h r AR/As and E R/L a are all within the range specified by the present invention (Test numbers 2, 4, 6, 1
0°11.12, 1.3, 14, 15. No. 17) has a joint stiffness ratio (E/Eo) of 09 or more, and it can be seen that there is no problem in practical use. It is also clear that even if the axial distance [LG] is large and therefore LG/h is large, E/E≧09 can be satisfied if an appropriate filler with a large elastic modulus [ER] is selected (
(See results for test numbers 2 and 4).

However, for large-diameter steel bars, care must be taken because if LG/h becomes too large, it becomes difficult to satisfy the condition of ER/LG≧5×10'. In particular, in the case of D51 steel rod, which is used in the largest quantity, LG/h≦1
．． It is desirable to set it to 5.

Furthermore, although a larger value of AR/A B is advantageous in increasing joint rigidity, unnecessarily increasing the length of the coupler is due not only to the material and manufacturing costs of the coupler but also to the filler material used. It is also not economical in terms of quantity. Therefore, AR/
A value of AB of about 0.3 is practically suitable.

The filler must be selected by carefully examining its elastic modulus [:ER] after curing, as well as workability such as viscosity during injection. This is because there are materials, such as the filler A, which exhibit a sufficiently large elastic modulus [ER] at room temperature but whose value decreases at high temperatures.

By the way, FIG. 5 shows the relationship between the axial distance [LG] and the rigidity ratio (E/Eo) based on the test results of the D51 material (filler B) in Table 1.

From Figure 5, the axial distance [LG] is 0.6 cm.
It can be seen that the stiffness ratio (E/Eo) exceeds 09 when the ratio is below. And the axial distance [LG] is 0.2
When it becomes smaller than 5cIrL, E/Eo increases rapidly. This phenomenon occurs because when the axial distance (Lo) falls below a certain range, the filling material no longer stretches out in the direction perpendicular to the axis when axial stress is applied, and the axial rigidity of the filling material decreases. This is thought to be due to a substantial increase.

It goes without saying that the gist of this invention is a threaded joint for steel bars using the grouting method, so it can be applied not only when threads are provided along the entire length of the steel bar, but also when threads are provided at the ends to be connected. It goes without saying that steel rods installed only in sections are also covered. In other words, the PC is smooth except for the edges.
It is also fully applicable to the connection of steel bars and steel bars with normal irregular patterns.

Furthermore, the thread may be formed by any processing method such as rolling, rolling, cutting, etc.

<Overall Effects> As explained above, according to the present invention, by appropriately determining the shapes of the male thread of the steel bar and the female thread of the joint sleeve, and by selecting the type of filler correctly.

It is possible to reliably create threaded joints that have the required rigidity under all practical usage conditions, and it is possible to further increase the reliability of structures using steel bars, thereby expanding the field of use of grout method joints. This brings about extremely useful effects.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an example of a threaded joint for steel bars of the present invention, Fig. 2 is a schematic explanatory diagram showing a threaded joint made by the torque method, and Fig. 3 shows a threaded joint made by the grouting method. 4 is a schematic explanatory diagram of the main parts of the threaded joint of the present invention, and FIG. 5 is a graph showing the relationship between the axial distance of the gap between the male thread and the female thread of the joint and the joint rigidity ratio. . In the drawings, 1... Joint sleeve (coupler), 2... Lock nut, 3... Steel rod, 4... Filler injection hole, 5... Filler. Applicant Sumitomo Metal Industries Co., Ltd. Agent Tomi 1) Kazuo and 1 other person

Claims (1)

[Claims] Steel bars having male threads at least on the outer periphery of their ends,
A joint which is butt-connected by a sleeve having a female thread on the inner surface to be screwed into the joint, and in which a filler is filled in a gap between the male thread and the female thread that are screwed together, the joint being in an axial direction of the gap between the male thread and the female thread. Distance [LG], total area C of each end of the steel bar of the male thread on one side facing the female thread in the axial direction
A threaded joint for steel bars, characterized in that the elastic modulus [AR] of the filler after hardening and the elastic modulus [ER] at the joint use temperature of the filler after hardening simultaneously satisfy the following conditions (1), (2), and (2), respectively. L(, /h≦3.0 ......■ AR/, kB≧0.2 ......■ER/LG≧5
X 10'・・・・・・■