JPH0161140B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for anchoring beam main reinforcements to improve the seismic performance of reinforced concrete structures.

In reinforced concrete multi-span frame structures, the main reinforcement of the beam usually passes through the joint with the column, that is, the joint, so-called through-reinforcement arrangement. For this reason, the repeated stress during earthquakes and the deterioration of adhesive strength increase the possibility of slipping out, reducing the strength of the joint.

Furthermore, when the end of the beam becomes a plastic hinge, bending cracks occur in that part, reducing shear rigidity, but it has been difficult to prevent this with conventional stirrups. These phenomena have the disadvantage that the energy absorption ability of the plastic hinge is reduced, reducing the safety of structures whose earthquake resistance is ensured by their plastic deformation ability.

A method for solving this drawback has already been disclosed (Japanese Patent Laid-Open No. 57-29763). As shown in FIG. 8, reinforcing bars 6 are tied along the beam passing bars 1 of the joint section, and the ends thereof are bent and fixed within the beam ends.

According to this method, a decrease in shear rigidity when the beam ends are plastically hinged can be prevented by the strut action or tie action of the diagonally anchored parts of the reinforcing bars, but it is economically It had the disadvantage of being a heavy burden.

This invention was made to solve this problem, and instead of using all or some of the beam main reinforcements as through reinforcements, after extending them to other beams through the joint part,
It is fixed by bending it in the vertical direction.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a reinforced concrete column-beam joint showing an embodiment of the present invention, and FIG. 2 is a plan view.

Among the main reinforcements of the beam, the inner main reinforcements 1a at the upper and lower ends are guided into the opposite end of the beam through the joint part 2,
There, it is bent up or bent down and fixed. For this reason, an X-shaped main reinforcement anchoring section in elevation is formed at the beam end by the anchoring sections of the upper and lower beam main reinforcements. It is effective to set the bend angle to approximately 45°.
The end of the fixed end is not particularly tightened.

In this example, the main reinforcements 1b other than the inner main reinforcements 1a are arranged in the conventional through reinforcement arrangement. Of these, the corner main reinforcing bars 1b1 are threaded reinforcing bars, and are fixed to the inside of a ring plate 3 instead of a hoop via nuts 4. Note that due to the presence of the ring plate, the inner main reinforcement also passes through it, but it is not necessarily necessary to lock it at the fixing end side. This is because the stress in that part is passive with respect to the joint part, and the locking effect of the bend part is added.

According to this mixed usage method in which the main reinforcing bars at the four corners of the beam are passed through and arranged as reinforcement, there is no problem in construction, especially in the installation of stirrups, and the amount of reinforcing bars is minimized.

In addition, the load-deformation curve obtained by the experiment of this example is shown as a solid line in FIG. In the figure, the dotted line indicates the normal through-bar arrangement (Figure 4) under the same conditions except for the joint hoop. All of them are of the beam yield type, but the one of this example not only has a high yield strength, but also has spindle-shaped restoring force characteristics and good energy absorption ability.

A second embodiment of the invention is shown in FIGS. 5 and 6. A horizontal haunch 5 is provided on the beam to substantially enlarge the joint section, and the column hoop is accordingly enlarged. The hoop is a ring plate, and the main reinforcing bars at the corners are locked to this via nuts to prevent the main reinforcing bars from slipping out.

FIG. 7 shows the load-deformation curve obtained through the experiment of the second example. For comparison, the graph of the first example is marked with a dotted line. Resilience properties are further improved.

As described above, since the present invention fixes the main beam reinforcement at the end of another beam, it is possible to prevent slipping and reduce the strength of the joint part due to the main reinforcement coming out without installing special reinforcing bars or fastening hardware. Moreover, it has the advantage of improving the shear strength of the beam end.

Further, if a horizontal haunch is provided on the beam, the joint portion will substantially expand and its proof strength will increase, which will improve the shear strength of the beam end and promote restoring force characteristics.

[Brief explanation of drawings]

1 and 2 are a sectional view and a plan view showing a first embodiment of the present invention. FIG. 3 is a graph showing the experimental results of the first example. FIG. 4 is a longitudinal sectional view showing an example of the prior art. 5 and 6 are a sectional view and a plan view showing a second embodiment of the present invention. FIG. 7 is a graph showing the experimental results of the second embodiment of the present invention. FIG. 8 is a sectional view of a column-beam joint explaining a known improvement plan. 1: Beam main reinforcement, 1a: Inner main reinforcement of the beam, 1b: Outside main reinforcement of the beam, 1b1: Corner main reinforcement of the beam, 2: Joint part,
3: Ring plate, 4: Nut, 5: Horizontal haunch, 6: Reinforcement bar, C: Column, B: Beam, P: Load,
Q: reaction force, N: axial force of column, δ: displacement.

Claims (1)

[Claims] 1. A method for fixing beam main reinforcement in a reinforced concrete structure, which comprises extending the main reinforcement of one beam to another beam through a joint part, and bending it vertically within the end of the beam to fix it. . 2. The method for fixing beam main reinforcement in a reinforced concrete structure according to item 1, wherein the beam main reinforcement is an inner main reinforcement. 3. The method for anchoring beam main bars in a reinforced concrete structure according to item 1 or 2, wherein the bend angle is about 45°. 4 A horizontal haunch is provided between the ends of the beams that intersect at the joint part, thereby substantially expanding the joint part, and in conjunction with this, expanding the column hoop of the joint part, and removing all or part of the main reinforcement of the beam. A method for fixing main beam bars in a reinforced concrete structure, characterized in that the ends of the beams are guided to other beams through joints, bent vertically, and fixed. 5. The method for fixing main beam reinforcement in a reinforced concrete structure according to item 4, wherein the hoop of the column at the joint part is a cylindrical ring plate.