JPS5853879Y2 - Anchoring structure of PC steel material - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a fixing structure for PC steel materials.

In the conventional crimp-type fixing structure, a deformed wire spring that has been hardened and twisted by quenching is fitted onto the entire surface of the PC steel material that comes into contact with the sleeve, and compressive residual stress in the circumferential direction is applied to the sleeve through the crimp process. By providing these three components, these three components are mechanically integrated.

The prestress was maintained by fixing this PC steel material to concrete or the like via the fixing surface.

However, in such a fixing structure of the PC steel material and the sleeve, since the two are integrated at a position approximately 5 mm from the fixing end surface, stress is concentrated at this portion.

To illustrate this schematically, in FIG. 1, the increase in the isolateral temperature area with respect to the distance from the fixing end is as shown by curve 5.
There was a sudden change at the Xl position, stress was concentrated at this part, and combined with the notch effect caused by the triangular wire spring, the fatigue resistance was impaired.

In order to alleviate such stress concentration areas, it is conceivable to weaken the compression force of the sleeve as it approaches the fixing end surface of the sleeve, but in reality it is difficult to adjust the compression force, as shown in Figure 1. It becomes a gentle curve as shown in curve 7, and in this case, the part with the largest isolateral temperature area, that is, P
Distance required for C steel material and sleeve to be integrated (Y-X
In order to ensure 3), the length of the sleeve becomes long, which goes against the demand for downsizing of the sleeve.

The present invention was made to solve these problems, and the purpose is to provide a fixing structure that can avoid stress concentration on the fixing end face and meet the demand for shortening the length of the sleeve as much as possible. It is something.

The present invention is a fixing device for a PC steel material in which a quench-hardened, tightly wound coil spring is fitted onto the outer periphery of the end of a prestressing steel material, and a steel sleeve is crimped from the outer periphery of the spring. The springs are different from each other, and the sum of the lengths of both springs is long enough to maintain the necessary fixing efficiency, and the spring closer to the fixing end surface has a cutout effect than the other spring. It is constructed of springs with a cross-sectional shape that has a small cross-section.

FIG. 2 shows one embodiment of this, in which springs 3 and 4 are fitted to the ends of the steel material 1, and a sleeve 2 is crimped from the outer periphery of the springs 3 and 4 to secure the steel material 1 in place.

The spring 3 is composed of a densely wound coil with a triangular cross section that has been quenched and hardened.

Therefore, the adhesion force due to the crimping of the sleeve 2 is large in the triangular wire spring portion, which has a large notch effect, and is small in the round wire spring portion.

That is, a spring with a small notch effect is used in the vicinity of the fixing end surface 10 for a length Lα, and a spring with a large notch effect is used in the remaining length Lβ.

Various other shapes can be adopted as the springs 3 and 4, and there are no particular limitations on their combination as long as the notch effect of the spring 4 is smaller than that of the spring 3.

In this way, if a spring with a small notch effect is used in a portion of a certain length Lα from the fixing surface, the change in the equivalent cross-sectional area will be as shown by curve 6 in FIG. 1, and stress concentration will be alleviated.

In this case, the length y-x2) over which the sleeve and the steel material are integrated can also be made relatively large.

Therefore, in the present invention, this length distribution can be easily set by selecting the lengths Lα and Lβ of the springs 3 and 4.

The values of Lα and Lβ are determined in consideration of the PC steel material used, the material and shape of the sleeve, the fixing efficiency, fatigue resistance, etc. required of the fixing section.

Then, a prestress of Q, 6XPu is introduced for the standard tensile load Pu, and for general PC steel material with a fixing efficiency of 1XPu, L a =0.6-0.8 ds
(ds: PC steel material diameter), Lβ = 3.6 to 4.4 ds
As a result of various experiments, it has been confirmed that the best results can be obtained if

As an example, a fatigue test was conducted on a conventional product and a product of the present invention using seven stranded PC steel wires each having a diameter of 15.2 mm, and the results shown in FIG. 3 were obtained.

The shape, material, processing conditions, etc. of the sleeves are the same for both, and the material of the sleeve is JIS-G450.
1-535C1 dimensions are outer diameter 34.8mm, inner diameter 17.4
The PC steel material is made of 7 PC steel strands 5WPR-7A as specified in JIS-G 3506, and the diameter is 15.2 mm. The spring is JIS-G 3502-8WR5-72B, and the outer diameter of the sleeve is 30. It was crimped to 5mm.

In this invention, the spring on the fixing end side has a diameter of 0.73 mm.
mm round wire spring, the remaining part is the same triangular wire spring as the conventional product, which is an equilateral triangle with one side of Q, 3 mm, and is molded and then quenched to have a hardness of Hv soo ~ 850, and L a = 0 .7 ds, I, β=3.9
ds.

The test conditions were a partial oscillation load with a lower limit load of 15960 kg and a repetition rate of 250 c, pom.

In the figure, curve 8 shows the characteristics of the product of the present invention, and curve 9 shows the characteristics of the conventional product.

This shows that the product of the present invention is significantly superior to the conventional product in both time strength and fatigue limit.

In addition, keeping the total length of the sleeve constant, Lα is 0.6 ds
In this case, the effect of inserting the round wire spring was weak, and there was no significant difference in the fatigue test from the conventional product shown by curve 9 in Figure 3.

Further, when Lα is set to Q, 8 ds, the results are equivalent to or higher than those shown in curve 8, but since Lβ becomes smaller, the fixing efficiency decreases, causing a practical problem.

In order to improve the fusing efficiency, the total length of the sleeve must be the minimum length required for the prestressing steel material from the standpoint of economics and space in the fusing section. The length should be long enough for the anchor to withstand the tensile force.

In order to improve the fatigue strength under such conditions, it is necessary to set Lα to 0°6 to 0.8 ds.

As explained above, the present invention uses a spring that has a small notch effect only in the vicinity of the anchoring end surface as a spring for anchoring the sleeve to the PC steel material, thereby alleviating stress concentration near the anchoring end surface and reducing fatigue. This is intended to improve strength.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing changes in the equivalent cross-sectional area of the fixing section, FIG. 2 is a longitudinal sectional view showing an embodiment of the present invention, and FIG. 3 is a comparison diagram of the characteristics of the product of the present invention and a conventional product. 1...PC steel material, 2...Sleeve, 3
, 4... Spring, 10... Fixing end surface.

Claims (1)

[Scope of utility model registration request] In a fixing device for a PC steel material, in which a quench-hardened, tightly wound coil-shaped spring is fitted to the outer periphery of the end of a prestressing steel material, and a steel snub is crimped from the outer periphery, the notch effect differs depending on the cross-sectional shape of the spring. It consists of springs, and the sum of the lengths of both springs is long enough to maintain the necessary fixing efficiency, and the cross-sectional shape of the spring closer to the fixing end surface has less of a notch effect than the other spring. An anchoring structure made of PC steel material, characterized by being composed of springs.