JPH0728269Y2 - Precast beams - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a precast beam used for a part of a reinforced concrete structure.

[Prior Art] A reinforced concrete structure may require a beam with a short span. The structure of the conventional reinforcing bar is mainly composed of main bars parallel to the longitudinal direction of the beam, and auxiliary bars such as abdominal muscles or costal muscles are combined therewith.

[Problems to be solved by the invention] However, the short-span beam mainly composed of the parallel main bars as described above is more likely to cause brittle shear fracture than the long-span beam. It is supported by the damage situation and experiments at the time of the earthquake, and countermeasures for it were desired. By the way, as a means to improve the toughness of beams and columns,
It is known to be effective to increase the number of ribs and stirrups, or to adopt so-called X-shaped reinforcements in which some of the main reinforcements cross each other, but for beams with short spans of reinforced concrete structure. If these are applied, the complicated bar arrangement work will become more complicated from the beginning, and it will take time and labor for the work at the site, and it will be difficult to secure the accuracy such as the arrangement interval of the main bar.
There was a problem that it was difficult to construct a good beam.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a precast beam having main bars arranged in the longitudinal direction, wherein at least a part of the main bars is provided in the longitudinal direction. In the vertical plane along the direction, they are arranged to intersect each other in an X shape, and the ends of the main bars are projected horizontally from the ends of the precast beam, and the tips are formed in an L shape in the vertical direction. The above-mentioned main bars of one precast beam and the other precast beam that are bent and are arranged adjacent to each other are arranged on one side and the other side with the same vertical plane sandwiched therebetween. The joint portions are provided so as to face each other without interfering with each other.

[Operation] In such a precast beam, not only the direction in which the main bars are parallel to the longitudinal direction of the beam but also the so-called X-shaped bar crossing each other, the toughness of the precast beam is greater than that of a beam with normal bar arrangement. It has been improved significantly. In addition, since it has been precast in factories in advance, the dimensional accuracy of the bar arrangement and the placement of concrete will be performed with sufficient control, and the work at the site will be simplified.

Further, since the end portion of the main bar is configured to be a joint portion bent into an L shape, the joint portion with the pillar can be easily joined with sufficient strength simply by placing concrete. it can.

In addition, one precast beam and the other precast beam that are adjacent to each other are configured so that the joint portions of the respective main bars face each other with the same vertical plane sandwiched, so that the precast beams can be easily connected to each other. It becomes possible, and the main bars of the adjacent precast beams become continuous in parallel with the longitudinal direction of the precast beams.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 to 7 show a first embodiment of the present invention, and the two-dot chain line in FIG. 1 shows the shape of the formwork 1A of the concrete short-span precast beam (PC beam) 1. The PC beam 1 is precast and formed in a factory or the like in advance. The solid line in Fig. 1 indicates a PC
Various reinforcing bars for reinforcing the beam 1, 2 are parallel main bars, 3 are X-shaped main bars, and 4 are ribs wound around the parallel main bars. The parallel main bars 2 are arranged at the four corners of the cross section of the PC beam 1 in parallel with the longitudinal direction of the PC beam 1, while the X-shaped main bars 3 have virtual vertical planes P parallel to the longitudinal direction of the PC beam 1. The same PC beam 1 which is sandwiched and is arranged in two pairs crossing each other in an X shape.
In, the two pairs of X-type main muscles 3 are arranged in the same direction. That is, as shown in FIG. 3, in the cross section of the PC beam 1, the upper bar arrangement is on the same side of the virtual vertical plane P. Two types are adopted in the arrangement of the X-shaped main bar 3. That is, in the type 1 PC beam 1a, in the cross-sectional view (the AA view in FIG. 2) facing the center from the end of the PC beam 1,
The X-shaped main bar 3a is arranged such that the upper bar is on the right side of the virtual vertical plane P and the lower bar is on the left side (see FIG. 3). Also, in the type 2 PC beam 1b, the X-shaped main bar 3b
The upper bar arrangement is on the left side and the lower bar arrangement is on the right side (see FIG. 4), and both are mirror-symmetrical. The ends of these main bars 2 and 3 project from the end surface of the PC beam 1, the parallel main bars 2 extend as they are, the X-shaped main bars 3 are once bent in the horizontal direction, and the tips are further bent vertically to form L.
Character-shaped anchors 5 and 6 are formed.

The method of constructing such a PC beam 1 will be described in connection with the case where the PC beams 1 are connected in series via a joint (intersection with a pillar).
This will be described with reference to FIGS. First, the precast
Position the PC beam between the pillars 7 by using concrete pillars that have been concrete-cast in advance to the bottom of the beam, or by using an appropriate pedestal.
The column main bar 8 constructed in 1 and the L-shaped anchors 5 and 6 described above are interlaced, or other auxiliary bars or the like are used to arrange the joint portion 9, and the form frame is arranged on the joint portion 9. Place concrete. This is done sequentially to build a PC beam structure,
As the PC beam 1 connected through the connection part 9, the type 1 PC beam 1a and the type 2 PC beam 1b are alternately used. In this case, the PC
The arrangement of the L-shaped anchors 6a, 6b protruding from the ends of the beams 1a, 1b is
As shown in Fig. 7, they will be aligned in the same direction, and there will be no gap between the anchors 6 as compared with the conventional case shown in Fig. 7A, which will facilitate the connection, The beam width is short. In addition, the left and right PCs in the connection section 9
Since the anchors 5 and 6 from the beams 1a and 1b do not interfere with each other, after the one PC beam 1 is installed, the other PC beam 1 can be dropped from above, which facilitates the work.

Further, the ends of the parallel main bars 2 are made parallel to each other without being L-shaped, and the ends of the main bars 2 of the PC beams 1a and 1b connected through the joint 9 are welded, pressure welded, mechanical joint or the like. 8 and 9 by connecting with a joint.
As shown in the figure, the beam width can be further reduced.

In the reinforced concrete structure constructed in this way, the toughness is improved because part of the main reinforcement of the PC beam 1 is an X-shaped reinforcement, and brittle shear fracture is less likely to occur in an earthquake or the like. This is well known. In addition, since it is precast, the work at the site is greatly reduced, it can be manufactured under sufficient management in advance, the arrangement of the main bars 2, 3 and the ribs 4, and other high-precision PC beams 1 Is manufactured.

Further, in the PC beams 1a, 1b arranged adjacent to each other, the continuous main bars 3a, 3b are configured to face each other across the vertical planes along the longitudinal direction of the PC beams 1a, 1b, respectively. The main bars 3a and 3b can be continuously extended in a direction parallel to the longitudinal direction of the PC beams 1a and 1b.

Furthermore, since the anchors 5 and 6 at the end of each main bar 3 are bent in an L-shape, each PC is
The beam 1 can be firmly joined and the strength against bending stress can be increased. Moreover, at the time of construction, each PC
After the beam 1 is installed at a predetermined position, it is only necessary to pour concrete into the joint portion 9 without performing a special joining work or the like, so that the construction can be easily performed.

The concrete configuration of the PC beam 1 is not limited to the above example, and the main bar may be only X-shaped as shown in the following example, or only a part of the beam may be used instead of the entire beam. It may be precast.

FIGS. 10 and 11 show a second embodiment of the present invention, which has a simpler structure than the first embodiment described above. That is, in the cross section of the PC beam 1, auxiliary parallel reinforcements 10 having a diameter smaller than that of the main reinforcement are arranged at the four corners, and these are wrapped or welded to the bent portion of the X-shaped main reinforcement 3 (corresponding to the end face position of the PC reinforcement 1). It is fixed by the
The ribs 4 are wound around 10.

The one shown in FIGS. 12 and 13 is the third one of the present invention.
This is an example, and this PC beam 11 has a configuration in which a part of the upper side is left and the lower side is precast in the second example. That is, a part of the upper side of the reinforcing bar is exposed to the outside, and a reinforcing bar for floor is connected to this part to integrate the floor slab.

FIGS. 14 to 16 show a fourth embodiment of the present invention, in which two mutually parallel X-shaped main bars 12, 12 are arranged on both sides of one virtual vertical plane P. The X-shaped main muscle 12 of has four intersections on one virtual vertical plane P. It goes without saying that such a PC beam 13 has further improved toughness and strength as compared with the first embodiment.

FIG. 17 shows a fifth embodiment of the present invention. When a plurality of short-span PC beams are connected in series with the joint portion 9 interposed therebetween as shown in FIGS. 5 and 6, a plurality of PC beams are previously prepared. The beam 14 is precast with the X-shaped main bars 15 connected in series by the parallel connecting portions 16. Although three PC beams 14 are connected in the figure, the number is not limited to this. It is advantageous in terms of strength that the parallel connecting portion 16 is made of the same reinforcing bar as the X-shaped main bar 15 and is inserted through all the PC beams 14, but the present invention is not limited to this. Further, the parallel connecting portion 16 may be formed in an X shape to improve the toughness of the joint portion. Although only the side view is shown in this figure, the specific arrangement of the reinforcing bars is based on that of the first or second embodiment. In such a configuration, the labor on site at the time of connecting the short span PC beams in series can be further reduced, and the connection strength between the PC beams 14 is improved. In addition to connecting linearly like this,
They may be connected at right angles or by bending at an appropriate angle as needed. Further, the configuration may be a combination of this example and the third embodiment.

[Effect of the Invention] As described in detail above, the present invention is a precast PC beam having main bars arranged in the longitudinal direction, in which at least a part of the main bars intersect each other in an X shape. Therefore, the toughness is markedly improved as compared with the PC beam with the normal reinforcement and the work on site is simplified.
In addition, because the dimensional accuracy of the bar arrangement and concrete placement are carried out under sufficient control, it is possible to provide a PC beam of higher quality than in the case of performing bar placement and concrete placement at the site. It is also possible to mold it into a special shape according to the construction situation.

In addition, in the precast beams that are arranged adjacent to each other, since the main bars are arranged on one side and the other side with the same vertical plane sandwiched, the main bars are continuous in parallel to the longitudinal direction of the precast beam. Can be extended.

Further, since the end portion of the main bar is bent into an L-shape, the precast beam can be firmly joined to the joint portion to increase the strength against bending stress. Moreover, the construction can be easily performed only by placing concrete.

[Brief description of drawings]

FIG. 1 is a perspective view of the first embodiment of the present invention, and FIG.
FIG. 3 is a side view of the embodiment, FIG. 3 is a view of the type 1 PC beam taken along the line AA in FIG. 2, and FIG. 4 is a view of the type 2 PC beam taken along the line AA in FIG. FIG. 7 is a plan view of the PC beam of the first embodiment, FIG. 6 is a view taken along the line VI-VI of FIG. 5, FIG. 7 is a view taken along the line VII-VII of FIG. 5, and FIG. 7A. Is a cross-sectional view of a pillar portion in the conventional case, FIG. 8 is a plan view showing a modification of the first embodiment, FIG. 9 is a view taken along the line IX-IX of FIG. 8, and FIG. 2 is a perspective view of the embodiment, FIG. 11 is a cross sectional view thereof, FIG. 12 is a perspective view of a third embodiment of the present invention, FIG. 13 is a cross sectional view thereof, and FIG. 14 is a fourth embodiment of the present invention. FIG. 15 is a side view of an example, FIG. 15 is a side view thereof, FIG. 16 is a view taken along the arrow XVI-XVI of FIG. 15, and FIG. 17 is a side view of a fifth embodiment of the present invention. 1,1a, 1b, 11,13,14 …… PC beam, 2 …… Parallel bars, 3,12,15
…… X-shaped main bar, 5,6 …… L-shaped anchor.

Claims (1)

[Scope of utility model registration request] 1. A precast beam having main bars arranged in the longitudinal direction, wherein at least some of the main bars are arranged to intersect each other in an X shape within a vertical plane along the longitudinal direction, The end portion of the main bar is a joint portion that protrudes horizontally from the end portion of the precast beam and has its tip portion bent in the vertical direction in an L-shape, and one of the joint portions is arranged adjacent to each other. The main bars of each of the precast beam and the other precast beam are arranged on one side and the other side with the same vertical plane sandwiched therebetween, and the joint portions are configured to face each other without interfering with each other. Precast beams characterized by.