JPH05321326A - Embedding forms for beam - Google Patents

Abstract

PURPOSE:To provide embedding forms for a beam which is high in strength and light and copes with a large and long span beam by a method wherein fiber-reinforced concrete mixed with a short fiber reinforcing material forms a base material, continuous fiber filaments are arranged as a stretch material, and prestress is introduced. CONSTITUTION:A stretch material 3 where, for example, longitudinally orientated three continuous fiber filaments of carbon fiber form a core is arranged at the U-shaped bottom part of U-shaped embedding forms 1 where fiber- reinforced concrete 2 mixed with carbon fiber short fibers forms a base material, and prestress is introduced through a pretension. A cotter 4 formed of uneven line extending the direction of width is arranged on the inner surface of the U-shaped embedding forms 1. Thus, weight owing to arrangement, beam concrete, and placing of floor slab concrete is exerted on the U-shaped embedding forms 1 but since prestress is introduced to the stretch material 3 where a core is formed of carbon fiber and continuous filaments, even a long span beam can be installed without using a timbering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precast concrete beam embedded formwork used when constructing a beam of a concrete structure.

[0002]

2. Description of the Related Art Conventionally, precast concrete members made of cement mortar or high-strength concrete have been used as an embedded formwork for beams with a concrete structure, but the reinforcing bars are mainly rebars and prestress is introduced. Not a member is common.

This is because, when a prestress is introduced into a thin-walled cross-section member made of cement mortar or high-strength concrete by the technique using conventional PC steel, the concrete causes splitting fracture, and a reinforcing bar for preventing splitting fracture is required. In addition, since the steel material used is corroded, it is necessary to thicken the concrete coating to protect the steel material, and the concrete cross section is usually large and not thin.

Therefore, the amount of concrete to be used increases, and in addition to the weight of steel having a large specific gravity, the unit weight of the manufactured member is large, and there is a problem that large-sized members and long-span members are uneconomical. It was

[0005]

The present invention has been made in view of the above problems. The purpose thereof is to propose a beam embedded formwork which has a high strength member, can be reduced in weight, and can be applied to a large beam having a long span.

[0006]

[Means for Solving the Problem] The buried formwork of this beam is constructed by using fiber reinforced concrete mixed with short fiber reinforcement as a base material, and using continuous fiber yarn as a tension material to introduce prestress. It is characterized by

[0007]

The embedded formwork is made of fiber reinforced concrete containing carbon fiber, aromatic polyamide fiber (aramid fiber), alkali resistant glass fiber or other short fiber having high tensile strength and high tensile modulus as a base material, and Since prestress is introduced by arranging continuous filaments of these fibers as a tension material, a thin cross section with high bending rigidity and bending resistance and a small amount of reinforcing bar is used to achieve high strength and weight reduction. Can be achieved.

Even if the fiber-reinforced concrete base material has a thin cross section, prestress can be introduced into the tension material without causing splitting fracture.

[0009] Even if the cross section is thin, the reinforcing fibers are corroded and
Demonstrate the desired performance over a long period without causing deterioration.

[0010]

EXAMPLE FIG. 1 shows an embedding form 1 for a beam made of prestressed concrete and having a U-shaped cross section (hereinafter referred to as U-type PC embedding form). This formwork 1 has a fiber-reinforced concrete 2 mixed with short carbon fibers as a base material, and has a U-shaped bottom portion made of a continuous fiber yarn of three carbon fibers oriented in the longitudinal direction as a core material. Has been arranged, and prestressing by pretensioning has been introduced. Further, on the inner surface of the mold 1, a cotter 4 formed of a ridge and groove along the width direction is provided.

This U-shaped PC-embedded formwork 1 is bridged between columns and arranged in a predetermined manner, and then a post-cast concrete beam is placed to construct a beam. In this construction, the formwork 1 receives the weight due to the reinforcement, beam concrete, and floor slab concrete placement, but since prestress is introduced into the tension material with carbon fiber and continuous yarn as the core material, It can be installed even in a long span without using shoring. Further, a cotter 4 is formed on the inner surface of the mold 1 to secure the integrity of the post-cast concrete and the mold 1.

A U-shaped PC-embedded form 1 of the embodiment shown in FIG.
Is the same as the formwork 1 of the above-mentioned embodiment in that the fiber-reinforced concrete 2 is used as a base material, the tension material 3 is laid on the bottom of the U shape to introduce prestress, and the cotter 4 is formed on the inner surface.
This formwork 1 has □ -shaped shear reinforcing bars 5 arranged therein in parallel in the width direction. As the shear reinforcing bar 5, a fiber reinforced plastic (FRP) having a long fiber yarn as a core material is suitable, but a steel material can also be used.

This formwork 1 has a shear reinforcing bar arrangement,
It is possible to improve the shear reinforcement effect and prevent damage during transportation and construction of the formwork.

[0014]

The present invention is as described above, and the buried formwork of this beam has the following effects.

(A) Lightweight and high-strength, the beam can be constructed without using the supporting work. Therefore, rationalization of construction,
It is possible to save labor and improve the safety of work on the lower floor.

(B) Since beams can be constructed without using steel materials such as reinforcing bars, they have excellent corrosion resistance and durability, and can be used for a long period of time when used in factories, marine structures or underground structures that generate corrosive gas. It becomes durable.

[Brief description of drawings]

FIG. 1 shows a U-shaped PC-embedded formwork of an embodiment,
(a) is a BB sectional view, (b) is an AA sectional view.

2A and 2B show a U-shaped PC-embedded form of another embodiment, wherein FIG. 2A is a sectional view taken along line D-D and FIG. 2B is a sectional view taken along line CC.

[Explanation of Codes] 1 ... U-shaped buried formwork, 2 ... Fiber reinforced concrete, 3 ... Tensile material, 4 ... Cotter, 5 ... Shear reinforcement.

Claims (1)

[Claims] 1. In an embedded formwork of a beam made of precast concrete, fiber-reinforced concrete mixed with short fiber reinforcement is used as a base material, and continuous fiber yarns are used as a tension material to introduce prestress. An embedded formwork for beams, which is characterized in that