KR810000214B1 - Steel bar for concrete reinforcement having non-circular cross-section - Google Patents

Abstract

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Description

Non-Round Steel Bars for Concrete Reinforcement

1 is a side view of a conventional steel rod for concrete reinforcement.

2 is a side view of a conventional steel rod for concrete reinforcement.

3 is a cross-sectional view of a conventional steel rod for concrete reinforcement shown in FIGS.

4 is a schematic diagram of a roll and a caliber for roll forming of conventional non-reinforcing steel bars for concrete reinforcement.

5 is a schematic diagram of rolls and calibers for roll forming of conventional non-reinforcing steel bars for concrete reinforcement.

6 is a schematic diagram of a roll forming of a conventional non-reinforcing steel rod for concrete reinforcement.

7 is a cross-sectional view showing an embodiment of the steel bar of the present invention.

8 is a main cross-sectional view comparing the present invention steel bar and the conventional steel bar.

9 is a chart comparing and experimenting with the concrete adhesion between the steel bar of the present invention and the conventional steel bar.

10 is a schematic of a pull-out test to measure concrete adhesion.

11 is a schematic for explaining the definition of the transverse protrusion height of steel bars.

Fig. 12 is a car art showing the relationship between the arrangement, shape, and adhesion of concrete to the steel bar.

13 is a graph illustrating the concrete adhesion characteristics of steel bars.

14 is a graph showing the relationship between pitch, height and concrete adhesion of the transverse protrusions of steel bars.

Fig. 15 is a schematic for explaining the method of crushing test apparatus of steel bar.

Figure 16 (a) is a steel bar and a plan view of the present invention.

Fig. 16 (b) is a-a cross sectional view of Fig. 16 (a).

The present invention relates to a steel bar having a non-circular cross section used for concrete reinforcement.

It is already known that steel rods with non-circular sections are used in place of circular rods as concrete reinforcing steel rods in the civil engineering field. With only one side of longitudinal projections of various shapes projecting in the direction, or US As in Patent 2,374,827, 2,377,980, there are ones having both a transverse protrusion and a longitudinal protrusion.

By the way, in the use of these non-circular steel rods, building performance has been increased, and the weight reduction of building materials has been progressed, and a prefabricated reinforcing bar assembly by factory production is used. As a result, the construction of concrete structures by reinforcing steel rods has been greatly shortened, streamlined, and standardized. However, in this case, the only problem is the connection structure of the reinforcing bars, which can be quickly and easily connected. It can absorb assembly errors and some standard errors and requires a firm and robust connection structure. Especially for non-circular reinforcing bars, various connection structures such as screw connection method and compression sleeve method are proposed. Since none of them were developed for commercially available non-circular steel bars, they cannot be said to be optimal.

In order to cope with this problem, the non-circular steel rod itself has a specific structure, and in recent years, a connection structure, a connection device, a facility, and an easy operation of the operation have also been developed. Steel rods, so-called threaded rods, belong to the typical ones, in which a plurality of ladder-shaped transverse protrusions are formed and these groups of displaced transverse protrusions can be joined with female threads.

When described in detail according to the accompanying drawings, as shown in the first and second examples, the required pitches are distributed along the lengthwise direction on the outer circumferential surface of the steel bar (1) so that the cross section on the outer circumferential surface of the steel bar (1) A plurality of transverse protrusions (2) are formed to protrude and these transverse protrusion groups consist of two transverse protrusion groups (2a) and (2b) facing each other on the outer circumferential surface of the steel bar (1). The relationship between the protrusions 2 of the groups 2a and 2b is such that they can be screwed together with the female screw. Patent 3,782,839 and FIG. 2 are shown in U.S.Patent 3,561,185, respectively.

According to this type of concrete reinforcing steel bar, the female screw can be accepted, and the connection of the steel rods can be easily and easily connected by using a coupler type sleeve. Also in the strength itself as a reinforcing steel bar, a favorable result is shown.

The cross-sectional shape of the threaded steel rod 1 of this kind, which is known in the art, is a cross-sectional shape of the steel rod main portion from which the transverse protrusion group is removed as illustrated in the enlarged cross section of FIG. In the center, the transverse protrusion (2) in the upper half of the center has a main body and a top of the concentric circumference, and the transverse protrusion (2) in the lower half in the center is different from the main body and the circular shape. Although it has an elliptic top, the transverse protrusion 2 having the top portion is formed as a ladder having a cross section in the circumferential direction in this way, and in this case, by accepting a female screw, There is no longitudinal protrusion projecting linearly on the outer circumferential surface over the longitudinal direction of 1). In the figure, 0 indicates the center of the circular steel rod body.

In the production of such steel concrete reinforcing steel bars, it is generally manufactured by hot rolling process for mass production of standardized products, and is usually hot pressed to have an oval or flat hexagonal cross-sectional shape in hot. The formed steel bar and a caliber as shown in FIGS. 4 and 5 are rolled to have a cross-sectional shape as shown in FIG. 3 by passing between a pair of finishing finishing rolls.

In the caliber of FIG. 4, the solid line part 3 is a part for forming the outer periphery of the three-dimensional part of the steel rod in a perfect circle, and the dotted part 4 is a transverse protrusion having the main part and the top of the concentric circle shown in FIG. (2) is a part for shaping, and the dotted line part 4a in FIG. 5 is a part for shaping the transverse protrusion 2 which has the elliptical top part shown in FIG. 3, and FIG. The relationship between (1a) and a pair of finishing rolls (5) and (5) is shown, and a pair of finishing rolls (5) and (5) with calibers as shown in Figs. 4 and 5 are used. When rolling by forming the steel rod 1a of elliptical or flat hexagonal cross section from the top and bottom, the cross section of the main part of the steel bar 1 is formed into a completely circular shape by the expansion in the lateral direction. The transverse protrusions 2 are formed. (6) represents the interval between the rolls (5) and (5).

정도에 머무르고 일반으로 사용되고 있는 종래의 비원형철근에 있어서의 돌기의 길이에 비하여 상당히 짧으며 콘크리이트의 부착성, 확실하고 강력한 나사결합성의 점에서 문제점이 있다.For this reason, it is necessary to strictly control the cross-sectional area of the steel bar, the shape of the roll and the rolling interval of the roll interval, but the length of the transverse protrusion 2 that is effective in view of the nut settled in such a control (circumference of the main part) Direction) of the steel bar (1) circumference

It is considerably shorter than the length of the protrusion in the conventional non-circular rebars, which are generally used, and have problems in terms of adhesion of concrete and reliable and strong screwing properties.

The present invention has been made to solve the problems of the conventional steel bar, and a first object of the present invention is to provide a steel rod for concrete reinforcement, which is capable of accepting a female screw and is provided with a simple, complete and easy connection device. .

It is a second object of the present invention to provide a steel rod for concrete reinforcement which is excellent in productivity and has superior characteristics in comparison with conventional steel bars in concrete adherence, screwing property and bonding.

In a first embodiment of the present invention for achieving the above or another object, a cross section in which a cross section is formed in a ladder shape protruding from a steel rod main body at a pre-selected pitch along a longitudinal direction of the steel rod is a ladder shape. Two-row projection groups composed of a plurality of projections are symmetrical to each other and formed on the outermost surface of the steel bar main body, and two straight-line longitudinal directions extending in the longitudinal direction of the steel bar at the middle points of the two-row projection groups The protrusions are symmetrically formed from the steel rod main body by two lines, and the distance from the steel rod shaft core to the outermost face of the longitudinal protrusion is equal to or slightly smaller than the distance from the steel rod shaft core to the outermost face of the steel rod main body. And the position of the outermost surface of the center of the transverse projection from the steel rod shaft core is on the virtual circumference having a diameter larger than the two distances. The distance to the outer surface of both side portions of the lateral projections is formed to gradually decrease toward the outermost surface of the longitudinal projections, and the relationship between the projections of the lateral projection groups can be screwed together with the female screw. It is a round rod.

In the second embodiment of the present invention, the height of the longitudinal projections in the steel bar of the first embodiment is 1.0-2.0 mm.

로 한 것으로서 이는 즉(0.05D_N+0.5)㎜로부터 (0.05D_N+1.3)㎜까지 되는 것이다.In the third embodiment of the present invention, in the steel bar of the first embodiment, the height of the transverse ceramic is set when the nominal diameter of the steel bar is D _N.

This is from (0.05D _N +0.5) mm to (0.05D _N +1.3) mm.

의 관계가 성립되도록 한 것이다.The fourth embodiment of the present invention, in the steel bar of the first embodiment, the relationship between the pitch (p) of the transverse projections and the height (h) of the transverse projections

The relationship between

의 관계가 되도록 한 것이다. 여기서 h는 횡방향돌기의 높이이다.The fifth embodiment of the present invention, in the steel bar of the first embodiment, between the nominal diameter (D _N ) of the steel bar and the pitch (p) of the transverse protrusion,

The relationship is to be. Where h is the height of the transverse protrusion.

In the sixth embodiment of the present invention, in the steel bar of the first embodiment, the bottom width W of the transverse protrusion is in the range of 0.81 D _{N to} 0.30 D _N , preferably 0.17 D _{N to} 0.30 D _N.

Where D _N is the nominal diameter of the steel bar.

In the seventh embodiment of the present invention, the flank angle between the screw face and the front face of the transverse protrusion in the steel bar of the first embodiment is 23 ° to 60 °.

In the eighth embodiment of the present invention, in the steel bar of the first embodiment, the width of the longitudinal projections is in the range of L / 36 to L / 12, where L is the nominal circumference of the steel bar.

Referring to the present invention in detail according to the embodiment of the drawings, shown in Figure 7 is a cross-sectional view of the steel bar according to the present invention, in Figure 11 (11) is the main body of the steel bar, (12), ( 12 indicates a transverse protrusion, and 13 and 13 indicate a longitudinal protrusion.

That is, the plurality of direction protrusions 12 are arranged on the symmetrical surface of the outer circumferential surface of the steel rod main body 11 at predetermined pitches according to the steel rod length direction, and the cross section protruding from the outer circumferential surface of the main body 11 is ladder-shaped. , Two rows of transverse protrusion groups 12a and 12b are integrally formed and formed at the midpoint of the two rows of transverse protrusion groups 12a and 12b. A pair of longitudinal projections 13 and 13 extending linearly protrude on the outer peripheral surface of the main body portion 11.

D₃＞D₄의 관계를 만족시키도록 한다.In this case, the outermost surfaces 13a and 13b of the longitudinal protrusions 13 and 13 and the outermost surfaces 11a and 11a of the steel rod main body 11 are centered on the axis 0. The lateral projections 12, 12 and the central outermost surface 12c are on a virtual circumference 15 having a diameter larger than that of the virtual circumference 14. At the same time, the outer surfaces of both side portions 12d and 12d of the transverse protrusions 12 and 12 are the outermost surfaces 13a and 13a of the longitudinal protrusions 13 and 13, respectively. If the distance from axis 0 is gradually reduced, the size between each specification D ₁ -D ₄ shown in the drawing is D ₁ > D ₂

Satisfy the relationship of D ₃ > D ₄ .

Among these, D ₁ is the diameter of the virtual circumferential surface 15, D ₂ is the diameter of the virtual circumferential surface 14, D ₃ is the outermost surface 13a, each of the longitudinal projections (13), (13) ( The diameter between 13a) may be the same as or smaller than the diameter D ₂ of the virtual circumferential surface 14.

In addition, although the side view of the steel bar of this invention was abbreviate | omitted, the relationship of each horizontal protrusion 12 in two-row lateral protrusion group 12a, 12b similarly to the threaded rod of the conventional example like 1st, 2nd degree is They are arranged so that they can accept female screws.

Advantages of a threaded steel bar having the above-described transverse ribs 12 and longitudinal ribs 13 according to the present invention will be described with reference to FIG. That is, the solid line in FIG. 8 indicates the shape of the transverse protrusion and the longitudinal protrusion according to the present invention as is apparent from FIG. 7, and is represented by a thin broken line (E). The figure shows the shape of the transverse protrusion (refer to FIG. 3) in the conventional threaded steel bar, and the upper half of the transverse protrusion is in the circumference with the center of axis 0 as the upper half from the axis of the drawing. The lower half is a case where the top of the transverse protrusion is on an elliptical line and corresponds to the transverse protrusions 2 and (2) of FIG.

에 멈추지 않고

이상으로 연장할 수 있으며 이에 의하여 나사결합성을 향상시켜 확실하고 강력한 나사결합이 되고 또 압력을 지탱하는 면적이 증가함에 의하여 콘크리이트에 대한 부착성을 현저히 개선할 수가 있다.As in the prior art, only the transverse protrusions 2 and 2 are pressed down by a pair of finishing rolls 5 and 5 and hot rolled with a caliber as illustrated in Figs. At the same time as the main body is formed, in the portion enclosed by the broken line E, the metal is filled to form the transverse projections 2, but the gap between the pair of finishing rolls 5 and 5 as in the present invention. In order to roll-form the longitudinal ribs 13 and 13 at the position corresponding to (6), the longitudinal protrusions 13 and 13 are not formed unless the B portion shown in the drawing is pressed down strongly and the grinding B By pressing down the part strongly, in response to this, a lot of metal is filled through the caliber by the part A of the drawing, and the part A extends outward and is rolled, so that the projections ( Effective length of 12) The length of the screw as the diameter (θ ₁ > θ ₂ > θ ₃ with respect to 0 in FIG. ₃ ) can be made longer than the other ones, and the A and B portions of the figure are an increase in the area supporting the pressure, as shown in the figure. Particularly, both side portions 12d and 12d of the transverse protrusion 12 extend effectively, and the effective length as the threaded portion as in the prior art is the

Without stopping in

It is possible to extend the above, thereby improving the screwing property, thereby making sure and strong screwing, and increasing the pressure bearing area, thereby significantly improving the adhesion to concrete.

FIG. 9 shows the results of experiments conducted to prove this, and the experiments were carried out with 150 mm of specimen steel rods each having a longitudinal rolling height of 0 mm, 1.0 mm and 1.7 mm, and a nominal diameter of 25.4 mm, respectively. It is buried in the center of the cube concrete as shown in FIG. 10. After sufficient curing, the steel bar is tensioned when the compressive strength of the concrete reaches 270 kg / cm 2, and the tension is embedded in the concrete. The relationship between the surface area divided by the buried portion (average adhesion stress) and the slip amount △ ℓ (that is, the amount of free rod sliding in the direction of the arrow) to the concrete is shown. It is called a pull-out test. And the height of the longitudinal projection is 0 mm, for example, U.S. Patent 3,561,185 and U.S. Pat. Conventional and threaded rods such as those shown in Patent 3,782,839. As a result of this experiment, the maximum value of the average adhesion stress was 91.3 kg / cm 2, 102.5 kg / cm 2 and 102.1 kg / cm 2 for the heights O mm, 1.0 mm and 1.7 mm of the longitudinal projections, respectively.

Thus, as is clear from the graph of FIG. 9, it became clear that the concrete protrusions were superior to the conventional threaded rods having a height of 1.0 mm or more in the longitudinal projections. However, increasing the height of the longitudinal projections increases the value of (D ₂ -D ₄ ) in FIG. 7 and increases the degree of the ellipse of the steel rod main body 11. This is undesirable because it generates directionality in bending of the steel bar. Therefore, the height of longitudinal ribs should be stopped to about 2.Omm, so the longitudinal projections and height should be 1.0-2.Omm.

13이 되어야 한다는 것이 밝혀졌다. 다만 여기에서 h는 제11도에 표시한 바와 같이, 횡방향 돌기의 중앙부의 높이 h₁와, 중앙부에서 강봉의 측심 0에 대하여 각각 45°변위한 부분의 횡방향 돌기의 높이 h₂및 h₃산술평균을 한것으로

이다.FIG. 12 shows the results of a pull-out test of specimen threaded rods with a nominal diameter of 25.4 mm when the pitch (P) and height (h) of the transverse protrusions were varied. When the free end slip direction △ ℓ of steel bar is 0.1mm, the adhesion stress τ _0.1 increases as p / h decreases, and the condition for τ _0.1 to be larger than conventional non-round steel bars is p / h

It turned out to be 13. However where h is the height of the 45 ° displacement transverse protrusion of a portion of each with respect to the height h _1, and a Sounding 0 of the steel bar in the central part of the central portion of the lateral projection h ₂ and h _3, as shown in claim 11 is also With the arithmetic mean

to be.

11이고, 또 p/h

3일 때는 τmax는 p/h 비율이 작게 되는데 따라서 감소되는 경향이 있기 때문에 결국 p/h 비율은

바람직하다.By the way, the condition for increasing the mean stress of the conventional elliptical steel bar having a maximum τ max adhesion stress at the maximum slip amount of the free end is p / h.

11 and p / h

At 3, τ max becomes smaller in p / h ratio, and therefore tends to decrease, so the p / h ratio

desirable.

In addition, the height of the transverse protrusion is high to increase the adhesion to the concrete and the screwing property, but it is preferable that the height of the transverse protrusion is low so as not to deform the thread (lateral protrusion) when handling the steel bar. Also, in view of rolling technology, if the height of the transverse protrusion is high, it is impossible to guarantee a uniform thread angle. Therefore, the height (h) of the transverse protrusion should be within the following range.

즉 (0.05D_N+0.5)㎜에서 (0.05D_N+1.3)㎜로 하여야 한다. 여기에서 D_N은 강봉의 공칭직경 이다.

That is, it should be from (0.05D _N +0.5) mm to (0.05D _N +1.3) mm. Where D _N is the nominal diameter of the steel bar.

The limit of p / h using FIG. 12 is based on the conventional design method of 'the free end slip amount for any load', but in recent years the concrete strength design method has been adopted as the concept of ultimate strength design method is adopted. The attachment to the twisted came to the fact that it was not vulnerable to destruction.

FIG. 13 schematically shows two typical curves of adhesion to concrete of steel bars, where curve C ₁ is brittle, and the concrete between the transverse and longitudinal protrusions of the steel rod is suddenly broken by shear. This is called shearing fracture. C ₂ is ductile, and the concrete between the transverse protrusions of the steel rods is slowly and partially broken, which is called bearing fracture. The ideal adhesion in the ultimate strength design method as a steel rod for concrete reinforcement,

(1) The curve in the elastic region is standing upright.

(2) The carbonaceous zone is large.

를 사용하여 표시하면,

이 그것을 위한 조건이 된다.It has two characteristics called. Based on this bottom line, if the relationship between the pitch and the height of the transverse projections that the shear resistance and the acupressure resistance are considered to be effective at the same time is obtained from the result of the full out test, it becomes the part indicated by the diagonal line of FIG. expression,

To display,

This is the condition for it.

1.72D_N으로 표시된다.In addition, in the experiment of fixing a steel rod with a screw thread to a surface plate with a nut and applying tension to the steel rod as shown in FIG. 15, the steel rod or nut is not broken and the steel rod main part is not broken. The relationship between the number of threads of the steel bar (n) screwed with the nut, the width of the bottom surface of the steel thread (W), and the nominal diameter (D _N ) of the steel bar has already been obtained by experiments.

1.72D _N

However, lengthening the nut indefinitely leads to a major problem in the manufacture of the nut and in the manufacture of the coupling coupler having a length more than twice that of the nut. That is, it causes the break of tap or bite for thread cutting and the deterioration of product quality, and the length of nut should be suppressed to 2D _N or less.

의 조건으로 부터,

으로 된다. 그러나 바람직한 것은

이 좋다.The limitation regarding the width W of the lateral protrusion at this time is

Under the terms of

Becomes But what is desirable

This is good.

23°와 같이 제한을 할 수가 있다.Moreover, the transverse protrusion shown in aa sectional drawing and 16th (b) figure in the top view of the steel bar of FIG. 16 (a) by the range of this transverse protrusion width W and the lateral protrusion height h is shown. Also regarding the flank angle α of the screw surface. α

You can limit it to 23 °.

The angle α may be more than 23 ° in theory, but the upper limit may be determined from the technical aspect of rolling, and may be limited to an upper limit of about 60 ° although it may be based on the rolling speed or the diameter of the rolling roll.

Next, it has been found from the rolling performance of reinforcing bars that the control of rolling can be significantly omitted if the area of the longitudinal projections of the steel bar is about half of the nominal cross-sectional tolerance, and the height of the longitudinal projections is 1.0 to 2. In the case of Omm, the width of the longitudinal projections is preferably in the range of L / 36 to L / 12. Where L is the nominal perimeter of the steel rod, ie L = πD _N.

As described in detail above, the non-reinforcing steel rod for concrete reinforcement according to the present invention can not only be combined with the female thread connecting device but also in the hot roll forming by the finishing roll, the cross section of the steel bar, the spacing of the finishing roll, and the rolling speed Since the area of the longitudinal projections can mitigate the error even if the back is not strictly controlled like the bells, the productivity can be improved compared to the conventional one, and the problem of the conventional threaded non-round steel rods is solved. It is possible to provide an excellent viewing angle in the properties, screw fixability and connectivity. Furthermore, the present invention is not only limited to concrete rods for concrete reinforcement, but can also be applied to steel rods for PS concrete and anchor bolts.

In view of the above teachings, it will be understood that various modifications and variations of the present invention are possible and that the present invention may be practiced otherwise than as specifically described herein within the appended claims.

Claims (1)

Two rows of projections comprising a plurality of transverse projections 12 each having a ladder-shaped cross section formed by protruding from the steel main body 11 at predetermined pitches along the longitudinal direction of the steel rods. Groups 12a and 12b are symmetrical to each other and are formed on the outermost surface 11a of the steel rod main body 11, and the two lines extending in the longitudinal direction of the steel bar at the middle point of the two-protrusion group The linear longitudinal projections 13 are formed so that two lines are symmetrical from the steel rod main body 11, from the steel rod shaft core 0 to the outermost surface 13a of the longitudinal projections 13. The distance D ₂ is equal to or slightly smaller than the distance D ₂ from the steel rod shaft core 0 to the outermost surface 11a of the steel rod main body 11, and is transverse from the steel rod shaft core 0. The position of the central portion outermost surface 12c of the direction protrusion 12 is on the virtual circumference 15 having a diameter larger than the two distances D ₂ and D ₃ and also the steel rod shaft core. The distance from (0) to the outer surface of both side portions 12d of the transverse protrusion 12 is formed to gradually decrease as it approaches toward the outermost surface 13a of the longitudinal protrusion 13, A non-circular steel rod for concrete reinforcement, characterized in that the relationship between the protrusions 12 can be screwed together with the female thread.

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