JPS6241841A - Reinforcement of pillar/beam connection part - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reinforcing a column-beam joint of a reinforced concrete structure.

The term "reinforced concrete structure" as used in the present invention refers to general reinforced concrete structures (RC structures) and steel reinforced concrete structures (SRC structures).

[Conventional technology]

Conventionally, concrete used for reinforced concrete structures has a compressive strength of 200 to 300 at 28 days.
It is around cm2. For this reason, when large deformations occur at column-beam joints due to earthquakes, etc., or when deformation of the pillars is applied, shear failure of the panel zone and pull-out of beam reinforcing bars may occur, resulting in severe damage to the joints. There was a fear that this would lead to a decrease in toughness.

This phenomenon is particularly noticeable when the structure is high-rise and large stress is applied to the column-beam joints in the lower floors. For this reason, methods to prevent shear failure in panel zones (intersections of columns and beams) without impairing the structural strength of reinforced concrete buildings include increasing the number of hoop reinforcements (shear reinforcing bars) and There is a way to increase the cross-sectional dimension of. On the other hand, methods to prevent the phenomenon of beam reinforcing bars being pulled out include using reinforcing bars with fixing plates, reinforcing bars with attachment fittings, and methods of welding beam reinforcing bars to column reinforcing bars. However, methods such as increasing the number of hoop bars and using anchor plates require reinforcing bars and metal fittings to be inserted into joints where column reinforcing bars and beam reinforcing bars are intricately intertwined, resulting in obstacles to concrete pouring. This results in the creation of voids within the joint, which is the most important part, resulting in a decrease in the rigidity of the member.

In addition, increasing the cross section of the joint results in significant economic losses such as increased dead weight and loss of space.

On the other hand, if the strength of the concrete used is low, it is impossible to prevent the reinforcing bars from pulling out even at joints where shear reinforcement measures have been taken, and fixing plates or the like are used to increase the adhesion of the beams. If pull-out is prevented, there is a high possibility of increasing shear failure in the panel zone.Also, if the concrete is of low strength, the compressed area of the joint will collapse during large deformations, resulting in a sudden decrease in toughness. This may lead to destruction.

For this reason, resin concrete is being considered as a material with good filling properties and high compressive strength, but resin concrete has significant volumetric shrinkage, problems with fire resistance, and adhesion of existing concrete. It has not been put into practical use because it cannot be poured unless the surface is completely dry.

[Problem that the invention seeks to solve]

The inventors of the present invention have investigated various cement-based materials that have high adhesion to existing concrete and reinforcing bars, are nonflammable, and can be cast on site.・The present invention was completed based on the knowledge that by pouring steel into beam joints, the joints can be reinforced by eliminating the phenomenon of reinforcing bars pulling out during large deformations.

[Means to solve the problem]

That is, in the present invention, when constructing a reinforced concrete structure, the column-beam joint of the structure has a compressive strength of 700 at the age of 28 days.
This is a method for reinforcing column-beam joints of reinforced concrete structures, which is characterized by pouring concrete or mortar of kg/am2 or more.

The present invention will be explained in detail below.

The present invention has a compressive strength of 700 kg/cm2 at 28 days.
This method is characterized by using the above concrete or mortar.

The reason why concrete or mortar having the above-mentioned physical properties is used in the present invention is as follows.

As shown in FIG. 1, when an external force acts on the beam 1 and the beam 2 undergoes a large deformation, tensile stress is generated in the reinforcing bar 4 at the top of the beam due to the bending moment. On the other hand, concrete 5 in the shaded area
compressive stress occurs.

In this case, the attachment length of the beam reinforcing bars within the column is generally shorter than the attachment length within the beam, although it is determined by the diameter of the reinforcing bars used. In this case, the adhesion inside the column breaks, causing the reinforcing bars to pull out, and the concrete in the shaded area to collapse, resulting in a significant decrease in toughness. Such a phenomenon is particularly noticeable when loading is repeated.

The pull-out phenomenon is usually judged by the deformation angle of the beam. The deformation angle changes depending on the amount of reinforcing bars, and the smaller the value, the better.

The compressive strength of the joint at 28 days is 700 kg/cm2.
By placing the above concrete or mortar, a dense, high-strength hardened cement body with high adhesion is formed around the reinforcing bars, thereby eliminating the phenomenon of beam reinforcing bars pulling out.

The concrete or mortar according to the present invention is not limited to any material as long as it exhibits a compressive strength of 700 kli'/cm" or more at 28 days of age.

The present invention will be further explained below by giving specific examples.

An example of concrete or mortar having the above-mentioned physical properties is, for example, concrete containing 5 to 35 parts by weight of ultrafine powder and 10 parts by weight or less of a high performance water reducing agent based on 100 parts by weight of cementitious material.

Cementitious materials are traditionally used as cementitious materials. Also, mixed cement mixed with admixtures such as blast furnace slag and fly ash, mixed cement made by pulverizing the mixed material and/or the cement to be mixed, and further cement containing pulverized blast furnace slag powder greater than mixed cement. can be used.

As the expanding material, for example, lime-based, gypsum-based, quicklime-gypsum-based, and calcium sulfoaluminate-based materials are effective. Due to its expansive properties, the preferred amount of cementitious material used is 1
00 parts by weight or less.

The use of fly ash is effective in improving fluidity without impairing strength properties and in reducing length changes. Spherical fly ash is most suitable. From the viewpoint of strength, the amount used is preferably 60 parts by weight or less per 100 parts by weight of the cementitious material, and more preferably 5 to 25 parts by weight.

The ultrafine powder is a powder with an average particle size of 1 μm or less, and there are no particular restrictions on its composition, but those that are easily soluble in water are not suitable. In the present invention, silica dust (silica fume) and siliceous dust, which are by-products during the production of silicon, silicon-containing alloys, and zirconia, are particularly suitable, including calcium carbonate, silica slag, opalescent sandstone, titanium oxide, and aluminum oxide. etc. can also be used. From the fluidity and moldability of the mixed material, the preferred amount of ultrafine powder is 100 parts by weight of the cementitious material.
) 5 to 35 parts by weight.

A high-performance water reducing agent (hereinafter simply referred to as a water reducing agent) is a surfactant that has a large dispersing power without causing too much delay in setting or excessive air entrainment even when added to cement in large quantities.Melamine sulfone Examples include salts of acid formaldehyde condensates, salts of naphthalene sulfonic acid formaldehyde condensates, high molecular weight lignin sulfonates, polycarboxylate salts, and the like. The standard usage amount of water reducing agent is 0.3 to 1 weight of cementitious material, but in the present invention,
It is desirable to add 1 in a larger amount than that, preferably 1 in terms of solid content per 100 parts by weight of cementitious material.
The amount is 0 parts by weight or less, more preferably 1 to 5 parts by weight.

Although general sand or gravel can be used as the aggregate, using hard aggregate selected according to either a Mohs hardness of 6 or higher or a Knoop indenter hardness of 700 kg/m or higher will improve the strength and elastic modulus. It is extremely effective in improving

Examples of materials that meet this criterion are sandstone, pyrite,
Hematite, magnetite, yellow jade, lawsonite, corundum, zenasite, suzannell, beryl, full curb stone, tourmaline, granite, andalusite, cross stone, zircon, calcined bauxite, boron carbide, tungsten carbide, ferrosiliconite These include silicon nitride, fused silica, fused magnesia, and silicon carbide.

Add water to the above ingredients to obtain a mixed substance. From the viewpoint of filling properties, the amount of water added is preferably 10 to 60 parts by weight, more preferably 15 to 25 parts by weight, per 100 parts by weight of the cementitious material.

In the present invention, in addition to the above materials, the following calcined CaO
And/or the use of rapidly hardened materials will bring out the effect even more. The use of calcined CaO is effective in adhering to beam reinforcing bars and reducing shrinkage.

As calcined CaO, soft calcined, hard calcined, molten products, etc. can be used.
Soft calcined CaO is preferred from the viewpoint of reactivity. Further, the particle size of calcined CaO is preferably 88 μm or less in view of reactivity.

The amount of calcined CaO used is 1 to 10 parts by weight, preferably 2 to 8 parts by weight, per 100 N parts of the cementitious material. 1N
If the amount is less than 10 parts by weight, the cured product will shrink, and if it is more than 10 parts by weight, it will overexpand.

The timing and degree of the digestion reaction of calcined CaO varies depending on the calcination method, but the calcined CaO used in the present invention is
, 100 to 1,300° C. for 6 to 5 hours, and those having a crystal grain size of 10 μm or less are more preferable.

Further, as the rapidly hardening material, a mixture of calcium aluminate and inorganic sulfate is suitably used, and the blending ratio thereof is preferably 10 to 40% by weight based on the inner weight of the cementitious material. Concrete or mortar using rapid hardening materials has excellent strength development in a short period of time, so if filling workability is an issue, you can freely adjust the pot life by adding a setting retarder. . Examples of setting retarders include hydroxycarboxylic acids such as citric acid, tartaric acid, and gluconic acid, or water-soluble salts thereof, Na 2 CO 2 , and Na
Examples of HCO3+ include alkali carbonates and bicarbonates such as 2CO3 and KHCO3.

In addition to the above-mentioned materials, fibers such as carbon fiber, steel fiber, vinylon fiber, glass fiber, metal pieces, etc. can also be used in combination.

Next, a method of mixing the above materials will be explained.

The usual method is to dry blend the above materials in advance and add water to this, but there are also methods in which each material is weighed separately and mixed at the same time, and, for example, materials other than ultrafine powder and water reducing agent are kneaded with water in advance. However, it is also possible to use a method in which ultrafine powder and a water reducing agent are then added and kneaded again. The mixers used for mixing are regular paddle type mortar mixers, omelet mixers, hand mixers, strong agitation mixers, etc.
Any format may be used as long as it can be mixed.

Concrete or mortar that has been uniformly mixed can be poured by head pressure, by pouring, by pump, etc., and especially for mortar, the pre-packet method is also possible.

Note that the term "column/beam joint" as used in the present invention refers to the intersection of a column and a beam (panel zone) and the connection area that is continuous to the joint, and it can be used up to six times the position of the normal column and beam. This is the shaded area in FIG. In other words, the column's fault is t, and the beam's fault is t2.
Or if t3 (t3≧12), the column part is 313=
The range of L2 and the beam part is 6t knee L□, which is the column-beam joint of the present invention.

〔Example〕

The present invention will be explained in more detail below with reference to Examples.

Example 1 As shown in FIGS. 6 to 5, Sn2[]-D1 was used as the main reinforcement.
6 as a shear reinforcing bar, Sn2[]-DiO-@io
A model specimen for mounting a column-beam joint was created using 5D30-D10-@150 and 5D30-D10-@150. First, ordinary concrete with the composition shown in Table 1 is poured in the areas other than the column-beam joints (the middle plowing line part in Figure 6), and then concrete with the composition shown in Table 2 is poured into the joints, and concrete with the composition shown in Table 2 is poured into the joints. It was air-dried until the day.

On the other hand, using the ordinary concrete shown in Table 1 and the concrete shown in Table 2 used as model specimens, each
After preparing a cylindrical specimen of In and air-drying it until 28 days old, the compressive strength and elastic modulus were measured. The results are shown in Table 1.
and Table 2. In the test, a load was applied to a model specimen including the column-beam joint, and the structural strength of the column-beam joint was measured.

As shown in Fig. 3, while an axial force of 30 tons was applied to the column, a repeated positive and negative vertical load was applied to the end of the beam.

After measuring the load at which the beam main reinforcement yields (yield load) and the deformation angle (yield deformation angle), the deformation angle was gradually increased while applying positive and negative loads repeatedly. At the 13th cycle, the load on the beam was measured when the deformation angle reached six times the yield deformation angle.
It was confirmed that 95% of the yield load was maintained, and the performance of the joint was high.

As shown in FIG. 6, the beam reinforcing bars were fixed using welding so that the bonding length was 550 mm and no pull-out occurred at the ends of the model specimen.

t47) <Materials used> Cement - manufactured by Denki Kagaku Kogyo Co., Ltd., ordinary Portland cement ultrafine powder - silica dust from the production of 111 fujirosilicon (
Average particle size: 0.1μ) Water reducing agent A, manufactured by Ippozolis Bussan Co., Ltd., product name “P”
O2z/16.5L" Main component lignin sulfonate ttB-m-High performance water reducing agent, manufactured by Denki Kagaku Kogyo Co., Ltd. Part name "FT-500" Main component Salt of alkylnaphthalene sulfonic acid formaldehyde condensate, solid content Fine aggregate used in conversion C--Isagami sand, F M = 2.8 D
-11 Silica sand 1.5m1n or less Coarse aggregate E--1 Sagami gravel FM-6,70〃 F-
m-Sandstone Gmax 13 rnm Water --1 Tap water Example 2I'' The same procedure as in Example 1 was carried out except that the mortar shown in Table 2 was used for the column-beam joint of the model specimen. A cylindrical specimen on the 5JZ'XID side was prepared using the mortar used for the specimen, and after air-drying until 28 days, the compressive strength and elastic modulus were measured.The results are also listed in Table 2.

In the experiment using the model specimen, the yield deformation angle of the 16th cycle was 6
The load on the beam when the double deformation angle was reached was 96% of the yield load.

Comparative Example 1 A model specimen similar to that in Example 1 was made of ordinary concrete having the composition shown in Table 1, air-dried and cured until age 28, and then a loading test was conducted in the same manner as in Example 1. As a result, 16
The load on the beam when the deformation angle reached six times the yield deformation angle in the first cycle was 58% of the yield load.

〔Effect of the invention〕

The present invention has established a method for reinforcing column-beam joints with high toughness by preventing the phenomenon of beam reinforcing bars being pulled out (without changing the current design method and construction method).

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a state in which an external force acts on a column-beam joint and deforms it, and FIG. 2 is a perspective view of the column-beam joint. 6 is a schematic view showing the loading state of the model specimen, FIG. 4 is a sectional view taken along line aa in FIG. 6, and FIG. 5 is a sectional view taken along line bb in FIG. 3. Further, FIG. 6 is a cross-sectional view of the beam reinforcing bars in a fixed state. Code 1 Beam 2 Beam 3 after deformation Column 4 Beam top end reinforcing bar 5 Area where compressive stress occurs 6 Deformation angle 7 Oil jack 8 Main bar 9 Shear reinforcing bar 10 Attachment length 11 Anchor plate 12 Welding point C 1 Cross 4 Tile 5

Claims (1)

[Claims] (1) When constructing a reinforced concrete structure, the pillars and
The beam joint has a compressive strength of 700 kg/cm at 28 days.
A method for reinforcing column-beam joints in reinforced concrete structures, characterized by applying 2 or more layers of concrete or mortar.