JPH05302398A - Precast concrete beam - Google Patents

Abstract

PURPOSE:To increase workability on constructing and secure a high quality as a structural member when finished, by lightening a support structure for receiving the concrete weight placed at site in case of the structure used as a sub-frame for instance and preventing the withstanding force from decreasing due to deformation of the reinforcing cage when finished as a beam. CONSTITUTION:In a part of a beam which is in the lower position than the upper most end of stirrups 2b in a reinforcing steel cage 2 for the beam, concrete is previously placed and prestressed tension steel rods 4 are arranged in the concrete 3. One end of a shaped steel member 5 is protruded from the end of concrete 3 and at least a part of the steel member at the other end thereof is buried in the concrete, at both ends of concrete 3. And the reinforcing steel cage 2 is constituted to be a truss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to pre-concrete a beam portion of a reinforcing bar cage for beam reinforcement below a position below the upper end of a rib, and to dispose a tension steel material for introducing prestress in the concrete. The present invention relates to a precast concrete beam in which at least a part of a shaped steel material is embedded in both ends of the concrete by projecting one end from the concrete end face.

[0002]

2. Description of the Related Art In the above-mentioned precast concrete beams, conventionally, in constructing a reinforcing bar cage for beam reinforcement, main bars are arranged at the four corners of the cross-sectional view when the beam is completed, while the ribs surrounding these main bars are It is known that a plurality of them are arranged along the longitudinal direction of the beam in an independent state, and the lower half part of the rebar cage is embedded in concrete together with the shaped steel material in precast (for example, ,
See Japanese Utility Model Publication No. 2-5520).

[0003]

However, the above-mentioned conventional precast concrete beams have the following problems. In other words, this type of precast concrete beam is used as a formwork, for example, by burying the upper part of the ribs protruding from the precast concrete beam part in the concrete that is cast on site with the slab and the like. Although it constitutes a beam as a completed structural material, in the above-mentioned conventional configuration, since a plurality of ribs constituting the rebar cage were independently embedded in the concrete, the concrete to be constructed on site was constructed. The ribs do not contribute to the structural reinforcement of the precast concrete beam itself in the state where it is not a completed beam before it is placed, therefore the precast concrete beam is installed as a scrap frame. However, in order to be able to withstand the weight of the concrete to be poured, some kind of support such as supporting the middle part with support work is required. If you need because of construction there were many. Further, since the upper end portion of the independent ribs is exposed before the concrete is placed, there is a possibility that the ribs may be bent when a worker walks on it or the concrete is placed. ..

In view of the above situation, an object of the present invention is to provide a precast concrete beam which can have a light support structure when used as a scrap frame and which is less likely to damage the reinforcing bar cage.

[0005]

A characteristic construction of a precast concrete beam according to the present invention is that a reinforcing bar cage for beam reinforcement in which a portion below a position below the upper end of a rib is embedded in concrete in advance is a truss reinforcement. There is something I did.

[0006]

[Action] In other words, the plurality of ribs that make up the rebar cage are not independent of each other, but the structure that is structurally solidly organized by constructing the truss reinforcement. Even if it is not completed as a beam before placing, the precast concrete beam itself in which a part of the reinforcing bar basket is concrete placed is one completed frame, so greater strength can be obtained. is there.
On the other hand, since each rib is connected to each other to form a truss, even if a load is applied to it by a worker walking on it, the postures of the ribs are regulated as trusses to prevent deformation. It can be prevented.

[0007]

As a result, since the precast concrete beam itself has a larger proof stress than before, when it is used as, for example, a scrap frame, a support structure for receiving the load of the concrete cast on site is light. Moreover, it is possible to avoid the situation where the yield strength is reduced when the beam is completed due to the deformation of the reinforcing bar cage, so the workability at the time of construction is excellent as a whole and the high strength at the time of completion as a structural material. We are now able to provide precast concrete beams that can ensure quality.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the precast concrete beam according to the present invention is constructed by embedding a part of a reinforcing bar cage 2 for reinforcing the beam, which is composed of main bars 2a and ribs 2b, in concrete 3. This concrete 3 occupies a position below the upper end of the rib 2b in the rebar cage 2 and is integrated with the concrete cast on site where the upper portion of the rib 2b is buried to form a beam. Configured to configure. Further, in this concrete 3, a tension steel material 4 for introducing prestress for increasing the bending resistance of the finished beam is arranged. The tension steel material 4 is installed by pretensioning. After the concrete 3 is placed in a state where a tensile force is applied in advance, the hardening is waited for and the tensile force is removed to compress the concrete 3 as a prestressing force. It gives power. Further, H-shaped steel 5, which is an example of a shaped steel material, is buried in both ends of the concrete 3 by projecting one end from the end surface of the concrete 3. Bolt holes 1a for high-strength bolts used for joining to the brackets of columns are formed in the projecting portions of both H-shaped steels 5, so that beam columns can be easily joined in a steel-framed reinforced concrete frame. ..

In the prestressing tension steel material of the present invention, the above-mentioned beam reinforcing reinforcing bar cage 2 is configured as a truss bar. Specifically, as shown in FIG. 2, a plurality of ribs 2b are arranged in a posture inclining with respect to the longitudinal direction of the beam, and the upper and lower ends of adjacent ones are aligned with each other to form the upper and lower main bars, respectively. 2a is joined by spot welding. The rebar cage 2 is provided so as to surround the H-shaped steel 5 at both ends thereof.

With this construction, the rebar cage 2 itself is assembled as one frame, and a large precast concrete beam can be obtained. Therefore, the precast concrete beam according to the present invention can be used as a scrap frame. It can be used to make a structure such as supporting work for supporting the concrete cast on site when placing the concrete on site on the top and making it a completed beam,
In addition to improving workability, even when a worker walks on the rebar cage 2 before the construction of cast-in-place concrete,
It is possible to reduce the deformation of the rebar cage 2 and avoid a situation in which a structural defect occurs in the completed beam.

Next, another embodiment of the present invention will be listed.

<1> Instead of connecting the ribs 2b and the main ribs 2a to form the truss reinforcing bar 2, the ribs 2b are replaced.
Alternatively, the reinforcing bar cage 2 of the truss bar may be configured only by the main bars of the beam to be independently arranged inside thereof. For example, as an example of the reinforcing bar cage 2 configured by only the ribs 2b, as shown in FIG. 3, two ribs 2x and 2y formed in a spiral shape are bite together and then welded to each other to be joined. You may make it comprise a truss muscle.

<2> As shown in FIG. 4, both ends of the reinforcing bar cage 2 serving as truss bars may be joined to the H-shaped steel 5 by welding. In this case, as shown in FIG. 5, another H-shaped steel 5 and the reinforcing bar cage 2 may be provided with another reinforcing bar cage composed of a main bar and a rib.

<3> In the above embodiment, H is used as the shaped steel material.
Although the section steel 5 has been taken up, T-section steel, C-section steel or the like may be used in place of it, and further, not only rolled material but also combination material may be used.

<4> In the previous embodiment, the method of pretensioning was used as an example to introduce prestress to the beam. However, the prestress is introduced into the concrete 3 which has been placed in advance. Alternatively, the sheath may be embedded and the tensile steel material 4 may be inserted into the sheath after the concrete 3 is hardened to apply a tensile force to the boss and tensioning. That is, the prestressing tension steel material 4 according to the present invention may be arranged before or after the concrete 3 is poured.

<5> In addition, in carrying out the precast concrete beam of the present invention, it is possible to change the concrete constitution without departing from the gist of the invention.
The upper end position of the concrete 3 to be placed in advance is the rib 2
Any position can be set as long as it is below the upper end of a.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

1] Side view

FIG. 2 is a perspective view of a rebar cage.

FIG. 3 is a perspective view of a rebar cage according to another embodiment.

FIG. 4 is a side view of yet another embodiment.

5 is a cross-sectional view of a modified example of another embodiment shown in FIG.

[Explanation of symbols]

 2 Reinforcing bar cage 2b Rib 3 Concrete 4 Pre-stressed tension steel 5 Shaped steel

Claims (1)

[Claims] 1. The ribs (2) of the reinforcing bar cage (2) for reinforcing the beam.
The beam portion below the upper end of b) is placed in concrete in advance, the tension steel material (4) for prestress introduction is placed in the concrete (3), and both ends of the concrete (3) are placed. A precast concrete beam in which at least a part of the shaped steel material (5) is embedded by projecting one end from the end surface of the concrete (3), and the rebar cage (2) is configured as a truss rebar. Concrete beams.