JPH06108656A - Precast member - Google Patents

Abstract

PURPOSE:To make it possible to obtain a specified amount of drawing with ease and a large prestress force to a satisfactory extent and reduce time and cost required for heating as well. CONSTITUTION:A sheath 3 is buried in a mortar or concrete molded body 1, whose required strength is produced, over pressure resistant plates 2 and then a coil-shaped shape memory alloy material 4 is inserted into the sheath 3 where the alloy material is preheated up to at least 50 deg.C and more extended by a specified value than the memory shape. Both the ends of the shape memory alloy material 4 are fixed with the pressure resistant plates respectively. Prestress is introduced by the shape memory alloy material 4 which is designed to return to the memory shape by a subsequent cooling operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precast member in which a prestress is introduced by a post tension method using a shape memory alloy for use as a beam or a slab.

[0002]

2. Description of the Related Art As a precast member as described above, there has been one disclosed in JP-A-60-47166. According to this known example, the As point is 100.
By stretching a rod of a shape memory alloy having a temperature of ℃ or more at room temperature by 3 to 6% and then arranging concrete and placing concrete, and then heating the rod to a temperature above the As point of the alloy by energizing the rod. A shape memory phenomenon was generated, and the shrinkage strain at this time was constrained by the bond force of the concrete to introduce prestress into the concrete.

[0003]

However, in the case of the above-mentioned conventional example, since the stretching itself by the rod of the shape memory alloy is used to introduce the prestress, it is difficult to obtain a sufficient stretching amount, and the introduction is performed. There was a drawback that the prestressing power could not be increased sufficiently.

Further, a shape memory phenomenon is caused by heating to 100 ° C. or higher, and the current must be kept in an energized heating state until the effect of introducing prestress appears, which lowers workability. In addition, there is a drawback that it becomes uneconomical in terms of running cost.

The present invention has been made in view of the above-mentioned circumstances, and makes it possible to easily obtain a predetermined amount of stretching to favorably obtain a large prestressing force, and at the same time, the labor for heating. And to enable cost savings.

[0006]

The precast member of the present invention is, in order to achieve the above-mentioned objects, a mortar or concrete molded body in which the required strength is developed, in a sheath embedded over a pressure plate, A shape memory alloy material with a coil shape that shortens and returns to a memorized shape after being heated to 50 ° C or higher and inserted in a deformable state is inserted, and both ends of the shape memory alloy material are used as pressure plates. The prestress is introduced by the shape memory alloy material that is fixed and is going to be shortened and restored.

[0007]

According to the structure of the precast member of the present invention, the coil-shaped shape memory alloy material is heated to 50 ° C. or more to be stretched before being inserted into the sheath, and is naturally cooled after being inserted into the sheath. The alloy material can be shortened to return to the memory shape, and the prestress can be introduced by the pulling force to restore the shortened shape.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an overall schematic perspective view showing a part of the precast member of the present invention as seen through, and FIG. 2 is a schematic vertical sectional view in which pressure plates 2 and 2 are provided at both longitudinal ends of a concrete molded body 1. Both pressure plates 2, which are provided
2, a sheath 3 made of a tube made of vinyl, rubber or the like is provided, and a coil-shaped shape memory alloy material 4 is inserted into each of the sheaths 3 ... Wedge 5 on pressure plate 2
The precast member 6 is formed by pre-stressing by the post tension method.

The shape memory alloy material 4 is made of a Ti-Ni alloy, is freely deformed at a temperature of 50 ° C. or higher, and returns to a predetermined coil shape stored in advance as it is cooled to room temperature. It is set and heated to a temperature of 50 ° C. or more and stretched by a predetermined amount, inserted into the sheath 3 and fixed to the pressure plate 2, so as to shorten and return to a predetermined coil shape with cooling. Prestress can be introduced into the concrete molded body 1 by the tensile force.

Next, the manufacturing process of the precast member 6 will be described.

First, as shown in the schematic cross-sectional views of FIGS. 3 (a) and 3 (b), the reinforcing bars 8 are arranged in the form 7, and the sheath 3 is installed at a substantially central portion in the thickness direction. Then, as shown in the schematic sectional view of FIG. 3C, concrete (or mortar) 9 is placed in the mold 7.

After that, as shown in the schematic sectional view of FIG. 3 (d), the mold 7 is removed after the required strength is developed, and pressure is applied to both ends in the longitudinal direction of the concrete molded body 1 thus obtained. A coil-shaped shape memory alloy that is provided with the plate 2 and is heated to 50 ° C or more by heating with hot water or a burner so that it can be freely deformed and is stretched by a predetermined amount compared to the shape stored in advance. Material 4 sheath 3
Insert inside.

Thereafter, as shown in the vertical sectional view of FIG.
By the wedge 5, both ends of the shape memory alloy material 4 are fixed to the pressure plates 2 and 2, and by natural cooling, a tensile force is generated to try to shorten and restore the shape memory alloy material 4 to the shape stored in advance. To introduce prestress.

The shape memory alloy material 4 is not limited to the Ti-Ni alloy as described above, but may be Cu-Zn or Ni-A.
1, various alloy materials such as Fe, Mn-based, and other ternary alloys can be applied.

[0016]

As described above, according to the precast member of the present invention, the elongation effect of the shape change is utilized instead of the conventional elongation itself of the shape memory alloy material itself, and the precast member is applied to the sheath. Before insertion, coil shape memory alloy material is heated to 50 ° C or more and stretched to a specified length, inserted into the sheath in that heated state and both ends are fixed to the pressure plate, then natural cooling is performed. As a result, the pre-stress can be introduced by the tensile force of the shape memory alloy material which tends to shorten and return, so that a predetermined amount of stretching can be easily obtained and a large pre-stress force can be satisfactorily obtained.

Moreover, by only heating to 50 ° C. or higher before insertion into the sheath, it is not necessary to maintain a high temperature heating state until after insertion into the sheath, and the labor and cost for heating can be reduced. .

[Brief description of drawings]

FIG. 1 is an overall schematic perspective view of a part of a precast member of the present invention seen through.

FIG. 2 is a schematic vertical sectional view.

FIG. 3 is a schematic cross-sectional view illustrating a manufacturing process of a precast member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Concrete molded body 2 ... Pressure plate 3 ... Sheath 4 ... Shape memory alloy member 6 ... Precast member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobunao Murakami Innovator, Nobunao Murakami 3-18 No.8, Mokudori, Mihara-cho, Minamikawachi-gun, Osaka Office of Technical Research Institute, Takenaka Corporation (72) Sadatoshi Ono Minamikawachi, Osaka Mihara-cho, Gunma 3-chome No. 3-8 Takenaka Corporation Technical Research Institute Osaka Branch

Claims (1)

[Claims] 1. A shape memorized by cooling after being heated to 50 ° C. or higher and inserted in a deformable state into a sheath embedded over a pressure plate in a molded body of mortar or concrete exhibiting the required strength. A shape memory alloy material having a coil shape that is shortened and restored is inserted into the pressure memory plate, and both ends of the shape memory alloy material are fixed to the pressure plate, and prestress is introduced by the shape memory alloy material that is going to be shortened and restored. A precast member characterized in that