JP3150927B2 - Reinforced concrete columns - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforced concrete column having a reinforcing bar.

[0002]

2. Description of the Related Art Conventionally, as a reinforced concrete column of this type, for example, JIS standards of SR235 and SD29, which are longitudinal reinforcing reinforcing bars in a substantially cylindrical form along an axial direction, are used.
5 or more round bars or deformed bars are located on the circumference and arranged side by side, and the design standard strength is 400 kgf / cm
RC piles (Reinforced spun Concrete piles) that have been centrifugally formed by putting in ^two or more pieces of concrete, or deformed steel bars that are arranged along the axial direction in a formwork are pulled and tensioned. There are known PC piles (Prestressed Concrete piles) in which concrete of 800 kgf / cm ² or more is put and molded, and a compressive stress is applied to the concrete.

[0003]

By the way, due to the recent increase in height and size of construction structures and seismic strength, it has been desired to further improve the strength of reinforced concrete columns for supporting construction structures. And, in conventional RC piles, while improving the compressive strength by using concrete compounded to have high strength, increasing the diameter of deformed steel bars or selecting the material of deformed steel bars, etc. It is conceivable to improve the strength by using deformed steel bars or increasing the number of deformed steel bars to improve the tensile strength. However, if the short-term allowable stress, which is the strength of concrete, is set in accordance with the strength of high-strength deformed steel bars, concrete cracks before reinforced concrete columns are subjected to tensile stress up to the specified yield point of high-strength deformed steel bars. However, the high strength of the deformed steel bar is not sufficiently satisfied, and even if a high-strength deformed steel bar and high-strength concrete are used, substantially no improvement in the strength of the reinforced concrete column can be expected. Further, cracks due to shrinkage during hardening of the concrete are liable to occur, making it difficult to manufacture and lowering the yield, so that an inexpensive reinforced concrete column cannot be obtained.

[0004] On the other hand, PC piles in which compressive stress is applied to concrete are constantly subjected to compressive stress. Therefore, even if tensile stress is applied to a reinforced concrete column up to the specified yield point of deformed steel bars, cracks are unlikely to occur, and cracks occur. Although the width is controlled to within 0.2 mm so that water does not invade and the internal rebar does not corrode, it is necessary to tension deformed steel bars during manufacturing, so equipment such as tensioning deformed steel bars is required. Due to the configuration, it is difficult to increase the diameter of the deformed steel bar or to increase the number thereof, and it is difficult to further improve the strength.

The present invention has been made in view of the above problems, and has as its object to provide a high-strength reinforced concrete column that can be easily manufactured while controlling cracks.

[0006]

A reinforced concrete column according to claim 1 is a reinforced concrete column in which an elongated bar-shaped reinforcing bar is provided along the axial direction on the concrete, wherein the concrete is used for the reinforcing bar to be used. The expansion rate was increased in response to the increase in the short-term allowable stress.

[0007] By adding and manufacturing concrete whose expansion rate is increased in accordance with an increase in the short-term allowable stress of the elongated bar-shaped reinforcing steel bar disposed along the axial direction, the concrete is set. Compressive stress is applied to concrete even if it is not manufactured by tensioning the reinforcing steel, and cracks are less likely to occur when stress is applied or during manufacturing, and the strength of the reinforcing steel and concrete is fully exhibited and high strength Can be easily obtained.

[0008] A reinforced concrete column according to a second aspect of the present invention is the reinforced concrete column according to the first aspect, wherein the concrete contains an expanding material in response to an increase in the short-term allowable stress of the reinforcing bar.

The expansion rate of the concrete is easily controlled because the expansion rate is increased in accordance with the short-term allowable stress of the reinforcing steel bar by adding the expanding material to the concrete.

A reinforced concrete column according to a third aspect is the reinforced concrete column according to the first or second aspect, formed by centrifugal force forming.

Then, in order to form by centrifugal force molding,
Since the expansion rate of concrete is increased by centrifugal molding, the expansion rate is easily increased.

According to a fourth aspect of the present invention, there is provided the reinforced concrete column according to the second or third aspect, wherein the inflating material is a reinforcing reinforced concrete column having a crack width of 0.2 mm or less at the time of a short-term allowable stress. With respect to the strain amount at the time point of the short-term allowable stress, the content is set as the expansion amount with the increase in the strain amount at the time point of the short-term allowable stress of the reinforcing steel used.

[0013] The amount of the expanding material to be added is such that the crack width at the short-term allowable stress level is 0.2 mm or less, at which the reinforcing steel does not corrode due to penetration of water. For the amount of distortion at the time,
Since the increase in the amount of strain at the time of the short-term allowable stress of the reinforcing steel to be used is added so as to compensate for the amount of expansion, high strength can be obtained while easily controlling cracks.

According to a fifth aspect of the present invention, there is provided the reinforced concrete column according to the second or third aspect, wherein the expanding material is a reinforcing reinforced concrete column having a crack width of 0.2 mm or less at a short-term allowable stress level. The amount of expansion at the short-term allowable stress and the value obtained by multiplying the increase by 1.13 with respect to the amount of strain at the short-term allowable stress and the value of the expansion at the short-term allowable stress are as follows. Is set as the range of the content.

The amount of the expanding material to be added is determined based on the amount of strain at the time of the short-term allowable stress of the reinforcing steel of the reference reinforced concrete column whose crack width becomes 0.2 mm or less at the time of the short-time allowable stress. In order to compensate for the increase in the amount of strain at the time of the short-term allowable stress of the reinforcing steel to be applied and the value obtained by multiplying this increase by 1.13 so as to compensate for the expansion, the cracks are easily formed. High strength can be obtained while controlling.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A process for manufacturing a reinforced concrete column according to one embodiment of the present invention will be described below.

First, in FIGS. 8 and 9, reference numeral 1 denotes a mold for centrifugal force forming. The mold 1 has a cylindrical portion 2 which is open at both axial end faces and has a substantially cylindrical inner peripheral surface. An end plate portion 3 for substantially closing both end surfaces in the axial direction of the cylindrical portion 2 is provided. A plurality of tire portions 4 are provided in a flange shape on the outer peripheral surface of the cylindrical portion 2. The end plate portion 3 is provided with a lid 5 that can open and close a concrete inlet (not shown) that is formed in a substantially radial position and that is opened. Further, the end plate 3
A jig for holding an end portion of an elongated rod-shaped reinforcing bar (not shown) and supporting the axial direction of the reinforcing bar along the axial direction of the cylindrical portion is provided on the inner surface side of the cylindrical bar.

A plurality of reinforcing bars and spiral reinforcing bars spirally connected to the reinforcing bars are supported by the end plate portion 3 and housed in the cylindrical portion 2.
Then, the end plate portion 3 is fixed by fixing means (not shown) such as bolts and nuts. Thereafter, cement, water, coarse aggregate, fine aggregate, and expanding material, as well as concrete appropriately mixed with a high-strength admixture, silica powder, a water reducing agent, etc., are introduced from a concrete inlet opening, and driving means (not shown) The centrifugal force is formed by rotating the mold 1. Then, the mold is appropriately removed and cured to form a reinforced concrete column.

The centrifugal forming mold 1 is not limited to those shown in FIGS. 8 and 9, but may have any structure.

Next, the operation of the above embodiment will be described.

[0021] The obtained reinforced concrete column is made of a concrete to which an expanding material is added and the expansion rate of which is increased corresponding to the short-term allowable stress of the reinforcing steel along the axial direction to be used. As in the case of PC piles (Prestressed Concrete piles), which tension the reinforcing steel bars without tensioning them, compressive stress is applied to the concrete relatively from the reinforcing steel bars due to the expansion of the concrete. For this reason, a device for tensioning the reinforcing steel bars is not required, and for example, the reinforcing reinforcing steel bars are made to have high strength by increasing the diameter of the reinforcing steel bars, using a high-strength material, or increasing the number of reinforcing bars. Even if the strength is improved by this, when the stress is applied up to the yield point specification value of this reinforcing steel, water enters and the internal reinforcing steel and spiral steel are corroded.
The above cracks do not occur. Therefore, even if the reinforcing steel and concrete are set to high strength, a high-strength reinforced concrete column can be easily formed at low cost while suppressing cracks and sufficiently exhibiting the high strength of the reinforcing steel and concrete.

In the above embodiment, the reinforced concrete column is a cylindrical one such as a reinforced concrete pipe.
Any shape such as a pillar shape may be used, and it is used for any purpose such as a pile or a pillar of a building, a distribution pipe, and a guide pipe.

[0023]

[Example] JIS A 5310 "centrifugal reinforced concrete pile"
It is specified that the crack width of RC pile (Reinforced spunConcrete pile) is within 0.2 mm which does not cause corrosion of internal reinforcing steel due to water penetration. The specified reinforcing steel has a diameter of 6 to 22 mm according to JIS, a round bar of SR235 and a width of 13 to 22 mm (D1).
3 to D22) and uses a deformed bar of SD295.

Therefore, based on the composition shown in Table 1, the deformed steel bars of SD 295 are used as reinforcing steel, and the reinforced concrete pile is used as a reinforced concrete pillar having a crack width of 0.2 mm or less. It was formed by conventional vibration molding and centrifugal force molding using a mold 1 as shown in FIGS. Here, Portland cement is ordinary Portland cement manufactured by Chichibu Onoda Co., Ltd., fine aggregate is hard sandstone crushed sand from Iwase having a particle size of 0.15 to 5 mm, and coarse aggregate is hard sandstone from Iwase having a particle size of 5 to 20 mm. Crushed stone, high-strength admixture is Onoda No. 1000 (trade name) manufactured by Onoda Co., Ltd., silica stone powder is manufactured by Chichibu Onoda Co., Ltd., and high performance water reducing agent is Mighty 150 manufactured by Kao Corporation.
(Trade name), Onoda Expan (trade name) manufactured by Chichibu Onoda Co., Ltd. was used as the expansion material. After curing under the conditions shown in FIG. 10 and FIG.
Cured in the air at ± 2 ° C and 60% humidity.

[0025]

[Table 1] The material age formed by each composition shown in Table 1 is 2
The expansion amount of the reinforced concrete pile on the 8th was measured according to JIS A 6202. The result is shown in FIG. In the case of the centrifugally molded product, the variation due to blending conditions, curing conditions, and the like was set to a range of 95% of the population average from the viewpoint of safety.

From the results shown in FIG. 1, it can be understood that the centrifugal force molded product has a larger expansion amount than the vibration molded product.

On the other hand, a deformed steel bar having a higher strength than SD295 has a width of 6 to 51 mm (D6 to D51) and a material of SD
345, width is 6 to 51 mm (D6 to D51), material is SD390, and width is 6 to 51 mm (D6 to D51)
The case where the material is SD490 and used as a reinforcing bar will be discussed. The strength is shown in Table 2. Table 2 shows the amount of concrete expansion such that the width of cracks within which corrosion of the internal reinforcing steel does not occur due to the penetration of water generated when stress is applied is within 0.2 mm specified by JIS. As shown, if the short-term allowable stress σ _s (kgf / cm ² ) is up to the yield point specification value of the reinforcing steel used,
An increase in the strain at the time point of short-term allowable stress up to the yield point specification value of SD295 of the reinforced concrete pile using SD295 which is a reference satisfying the crack width is compensated by expansion by the expanding material.

Here, since the expanding material is added to the concrete which is not originally added, it is necessary to consider the shrinkage of the concrete. The amount of expansion of the reinforced concrete pile using SD295 is measured by the material age in 28 days. However, the amount of expansion slightly decreases in the long term and depends on the environment such as curing in the environment of the storage place of the reinforced concrete pile. Variations occur. Therefore, the standard SD2
The increase in the strain of the reinforced concrete pile using the S.95 at the time of the short-term allowable stress of SD295 is the safe side.
The required expansion was set as shown in Table 2 by setting the shrinkage of the reinforced concrete pile using D295 to 0.

[0029]

[Table 2] By the way, especially when the diameter of the reinforcing steel bar is increased,
In order to prevent cracks due to the affinity between concrete and reinforcing steel during production, as shown in Fig. 2, the distance from the surface of the reinforced concrete pile to the center of the reinforcing steel regardless of the material of the reinforcing steel. become longer. And, as this distance becomes longer, the width dimension of cracks generated when stress is applied to the reinforced concrete pile also becomes larger.

Therefore, the relationship between the position of the reinforcing steel bar and the strain in reinforced concrete having a diameter of 300 mm, which is the minimum diameter of the reinforced concrete pile, will be examined. In addition,
As the diameter of the reinforced concrete pile becomes smaller, the width of the crack that occurs when stress is applied becomes larger.

First, the strain ε _SC [μm] of the concrete at the upper end position (C in FIG. 2) which is the outer periphery of the reinforced concrete pile serving as a reference is determined by the elastic modulus E of the concrete.
_{This is} the value of the short-term allowable stress σ _SC [kgf / cm ² ] of concrete with respect to _C [kgf / cm ² ]. That is, ε _SC = σ _SC / E _C = 425 / 0.4 = 1063.

In the case where reinforcing bars having different diameters are used, the position of the reinforcing bars is, for example, a spiral bar having a diameter of 8 mm is used as a spiral bar, and a main bar having a width of 41 mm ( D41) The strain ε _SB of the reinforcing bar at the position (B in FIG. 2) when the material is SD345
[Μ] is the value of the short-term allowable stress σ _SB [kgf / cm ² ] of the reinforcing bar with respect to the elastic modulus E _S [kgf / cm ² ] of the reinforcing bar. That is, ε _SB = σ _SB / E _S = 3500 / 2.1 = 1667.

The width from the neutral axis O in FIG.
Distance x to the position of the rebar of 1 mm (D41) (B in FIG. 2)
[Mm] is x = 250 × ε _SB / (ε _SC + ε _SB ) = 250 × 1667 / (1063 + 1667) = 152.7.

For this reason, when the same reinforcing steel as the existing RC pile is used, that is, the concrete covering, which is the distance from the surface of the concrete pile to the outer surface of the spiral reinforcing steel, is set to the same condition as described above, and the spiral reinforcing steel is used. Use a rebar with a diameter of 6 mm and a width of 13 mm (D1
When 3) is used, the width described above is 41 mm (D
The position is shifted by about 20 mm with respect to the position of the main bar in 41). Therefore, the strain ε _SA [μ] at this position (A in FIG. 2) in the reinforced concrete pile is as follows: ε _SA = ε _SB × (x + 20) / x = 1667 × (152.7 + 20) /152.7=1885

Accordingly, the ratio n of the increase in the strain compensated by the expansion of the concrete is as follows: n = ε _SA / ε _SB = 1885/1667 = 1.13, and the maximum strain of 13% depending on the position of the reinforcing steel bar is obtained. The increase will be compensated for by the expansion of the concrete.

When reinforcing steel bars having various short-term allowable stresses are used, the increase in strain shown in Table 2 is compensated for, and the range of the amount of expansion to be compensated is calculated.
From the range of the calculated expansion amount and the result shown in FIG.
The range of the amount of the expanding material to be added can be determined according to the reinforcing steel used.

As described above, the expansion amount is larger in the case of centrifugal force molding than in the case of vibration molding. As described above, especially in the case of SD490, the addition amount becomes too large, and the mixing balance is lost, so that high-strength concrete cannot be obtained. Is less than half, indicating that a high-strength reinforced concrete pile can be formed inexpensively without breaking the high-strength compounding balance.

Next, the strength of concrete will be examined.

The diameter of the wall is 400 mm, the wall thickness is 65 mm, PC steel is used for the main reinforcement, and the design standard strength of the concrete is 85.
At 0 kgf / cm ² , the effective prestress σce is 100 kgf / cm ²
Pre-tensioning type C centrifugal high strength prestressed concrete pile (PHC pile (Pr
etensioned spun High strength Concrete pile)) and a reinforced concrete pile formed in the same manner by adding 60 kg / m ^{3 of} intumescent material to concrete at the initial allowable stress N
The relationship between [tf] and bending moment Ma [tf · m] was compared.

Here, by adding the expanding material at 60 kg / m ³ , the expansion strain was reduced to about 110 from the graph shown in FIG.
0 μm. And, the concrete to which the expanding material is not added has a drying shrinkage of about 200 μm.
The strain will increase toward the 300 μ expansion side. When this strain is converted into stress, the amount of stress increase = the amount of increase in strain × the elastic coefficient of the reinforcing steel bar × the ratio of the reinforcing steel bar = 1300 × 10 ^-6 × 2.0 × 10 ⁶ × 0.015 = 39 [kgf / cm ² ]. Therefore, the expansion material by adding 60 kg / m ^3, effective prestress amount increases from 100 kgf / cm ² to about 140 kgf / cm ^2. And the design standard strength of concrete is 1000kgf / cm which is high strength concrete.
The relationship between the axial force N and the bending moment Ma at the initial allowable stress when the value was set to ² was examined. As a comparative sample, A species reinforced concrete pile design strength is 800 kgf / cm ² in an effective prestress weight 40 kgf / cm ^2, design strength is effective prestress value 850kgf / cm ² 8
Class B reinforced concrete pile of 0 kgf / cm ² , and design standard strength of 850 kgf / cm ² and effective prestress of 10
A class C reinforced concrete pile of 0 kgf / cm ² was used.

Here, the axial force N and the bending moment Ma
Σba ≦ N / Ae ± Ma / Ze ≦ σca−σce σba: Short-term allowable tensile stress of concrete [kgf / cm ² ] Ae: Cross-sectional area of concrete [cm ² ] Ze: Converted cross-sectional coefficient [cm ³ ] σca : Short-term allowable compressive stress of concrete [kgf / cm ² ] σce: Calculated from effective pre-stress [kgf / cm ² ]. The result is shown in FIG.

From the results shown in FIG. 3, it is understood that the use of the high-strength concrete to which the expanding material is added can improve the axial force N and the bending moment Ma, and obtain a high-strength concrete pile.

Similarly, RC piles (Reinforced spun
Similarly, the relationship between the axial force N and the bending moment Ma at the short-term allowable stress level was also compared for the concrete pile).
FIG. 4 shows the results.

From the results shown in FIG. 4, when the design reference strength of concrete and the short-term allowable stress of the concrete are constant and the strength of the reinforcing steel is changed, the axial force N and the bending moment Ma at the short-term allowable stress are changed. The relationship is that the negative axial force is slightly larger or smaller depending on the strength of the reinforcing steel, but no difference is recognized in the positive axial force or bending moment. When the strength of the reinforcing steel is not changed and the design standard strength of the concrete and the short-term allowable stress of the concrete are changed, there is no difference in the negative axial force. It was observed that the positive axial force and bending moment normally assigned to the core significantly increased or decreased.

Therefore, it is understood that the strength of the reinforced concrete pile can be improved by increasing the strength of the reinforcing steel bar and the strength of the concrete.

Therefore, using a high-strength reinforcing steel,
By using high-strength concrete that is set by increasing the amount of expansion in response to the increase in the short-term allowable stress of the reinforcing steel, it is possible to easily increase the strength while suppressing stress and cracking during manufacturing. It can be seen that a reinforced concrete pile with high strength can be obtained, and the amount of expansion material that varies the amount of expansion can be reduced by centrifugal force forming, and the pile can be formed at low cost.

Next, the diameter is 400 mm and the wall thickness is 85 m.
m, length is 4.0m, width is 13mm (D13), the number of reinforcing bars is 8, the spiral reinforcing bar is 100mm pitch using 6mm diameter ordinary iron wire, concrete design standard strength is 850kgf / cm ² , SD295, SD345, SD390 and SD4 conventionally used for reinforcing steel
90, the expansion material is 0 kg / m ^{3 in} SD295, SD
20 kg / m ^{3 for} 345, 35 kg / m for SD390
For m ³ and SD490, various reinforced concrete piles were formed at 60 kg / m ³ , and a bending test was performed as a strength measurement. Further, as a comparative example, a reinforcing steel bar made of SD345 without adding an expanding material was used. In the bending test, as shown in FIG.
m, the distance between the loading spans was 1.0 m, and the displacement was measured by installing a displacement gauge and a surface gauge at various places on the reinforced concrete pile under the conditions of the incremental displacement one-way repeated bending test.

As a result, the crack width at the short-term allowable stress level in SD295 with the expansion material of 0 kg / m ³ (without addition of the expansion material) and SD345, SD390 and SD490 with the predetermined amount of the expansion material added was determined by the standard. Although the value of 0.2 mm was satisfied, the width of the cracks was increased in the case of SD345 in which the expanding material was not added. FIG. 7 shows the relationship between load and displacement.
In the reinforced concrete pile formed of ordinary concrete using the reinforcing steel bar of SD345 to which no expansion material is added as shown in (1), the pile load capacity is from 21 cycles to the vicinity of the design breaking load (15.37 tf · m). The load decreased, and the pile yield strength decreased from the 25th cycle to the design yield load (9.98 tf · m) of the reinforcing steel, and at the 31st cycle, the pile yield strength fell below the design yield load of the reinforcing steel. The toughness index mu ₂ is a value of the maximum displacement [delta] _Max2 exceeding design yield load for yield displacement [delta] _y2 was _{μ 2 = δ Max2 / δ y2} = 238.5 / 3.7 = 64.5.

On the other hand, for example, as shown in FIG.
In the case of the material formed of concrete containing expanded material using No. 5, the pile strength was lower than the design breaking load from the 37th cycle, and the pile strength was lower than the design yield load of the reinforcing steel bar at the 40th cycle. Also, the toughness factor μ which is the value of the maximum displacement δ _Max1 exceeding the design yield load for the yield displacement δ _y1
1 was μ ₁ = δ _Max1 / δ _y1 = 279.9 / 3.19 = 87.7. Furthermore, the distribution width of the cracks generated in the reinforced concrete pile after the test was narrower in the case of the one made of concrete containing the expanding material using SD345. Note that δ for the maximum displacement δ _Max2
Max1 whereas a 1.17-fold, mu ₁ for toughness index mu ₂ is higher 1.36-fold and toughness ratio. this is,
This is because the design yield point displacement _Δy1 is smaller than _Δy2 . The [delta] _y1 is [delta] _y2 smaller than reason, [delta] _y1 is smaller crack width by chemical prestressing by expansion material, because the rigidity of the pile material is increased is due to the effect of the expansion member. Therefore, it is understood that the expansion performance also improves the deformation performance. SD390 and SD
Similarly, when 490 was used, better results were obtained than when SD295 was used.

From these facts, by forming a high-strength concrete to which an expanding material is added by using a high-strength reinforcing reinforcing bar, the crack width satisfies the standard value, the toughness is high, and the deformation performance is high. It was confirmed that an excellent high-strength reinforced concrete pile could be obtained.

[0051]

According to the reinforced concrete column according to the first aspect, the expansion rate is increased in accordance with the increase in the short-term allowable stress of the elongated bar-shaped reinforcing steel bar disposed along the axial direction, and the mixing ratio is increased. Because it is formed from the set concrete, compressive stress is applied to the concrete even if it is not manufactured by tensioning the reinforcing steel, making it less likely to crack when subjected to stress or during manufacturing, and for high-strength reinforcement When the reinforcing bar and the concrete are used, the reinforcing bar and the concrete exhibit sufficient strength, and high strength is easily obtained.

According to the reinforced concrete column of the second aspect, in addition to the effect of the reinforced concrete column of the first aspect,
Since the expansion rate is increased in accordance with the short-term allowable stress of the reinforcing reinforcing bar by adding the expanding material to the concrete, the expansion rate of the concrete can be easily controlled, and the concrete can be easily manufactured.

According to the reinforced concrete column according to the third aspect, in addition to the effect of the reinforced concrete column according to the first or second aspect, since the reinforced concrete column is formed by centrifugal force forming, the expansion rate of the concrete is increased by centrifugal force forming. In addition, the expansion rate can be increased, and the manufacturability can be improved.

According to the reinforced concrete column according to the fourth aspect, in addition to the effect of the reinforced concrete column according to the second or third aspect, a reinforcing bar for a reference reinforced concrete column having a crack width of 0.2 mm or less at the time of a short-term allowable stress is provided. Because the amount of strain at the short-term allowable stress of the reinforcing steel used is set as the amount of expansion with respect to the amount of strain at the short-term allowable stress of High strength can be obtained while controlling, and manufacturability can be improved.

According to the reinforced concrete column according to the fifth aspect, in addition to the effect of the reinforced concrete column according to the second or third aspect, a reinforcing bar for a reference reinforced concrete column having a crack width of 0.2 mm or less at the time of a short-term allowable stress is provided. Of the amount of strain at the time of the short-term allowable stress of the reinforcing steel to be used and the value obtained by multiplying the increase by 1.13 with respect to the amount of strain at the time of the short-term allowable stress of Since the addition amount of the expansion material is set as the amount, high strength can be obtained while easily controlling cracks, and manufacturability can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of expansion material added and the amount of expansion in one embodiment of a reinforced concrete pile according to the present invention.

FIG. 2 is an explanatory diagram for explaining an amount of distortion at a position of a reinforcing reinforcing bar according to the embodiment.

FIG. 3 is a graph showing a relationship between an axial force N and a bending moment Ma at an initial allowable stress level in the pretension type centrifugal high strength prestressed concrete pile.

Fig. 4 Axial force N at initial allowable stress level in RC pile
6 is a graph showing the relationship between the bending moment Ma and the bending moment Ma.

FIG. 5 is an explanatory diagram showing a bending test method according to the first embodiment.

FIG. 6 is a graph showing a relationship between a displacement amount and a load in a concrete pile formed of concrete containing an expanding material using SD345 having a higher strength than SD295.

FIG. 7 is a graph showing a relationship between a displacement amount and a load in a reinforced concrete pile formed of ordinary concrete by using a conventional SD295 as a reinforcing bar.

FIG. 8 is a side view showing a formwork of one embodiment of the reinforced concrete pile according to the present invention.

FIG. 9 is a front view of the same.

FIG. 10 is a graph showing one condition of the same curing.

FIG. 11 is a graph showing another condition of the same curing.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-76924 (JP, A) JP-A-61-246419 (JP, A) Japanese Utility Model Showa 57-202080 (JP, U) 33180 (JP, B2) JP-B-54-524 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16L 9/08 E02D 5/30 E04C 3/34

Claims (5)

(57) [Claims] 1. A reinforced concrete column in which an elongated bar-shaped reinforcing bar is provided along the axial direction in concrete, wherein the concrete has an expansion rate corresponding to an increase in short-term allowable stress of the reinforcing bar to be used. A reinforced concrete column characterized by an increase. 2. The reinforced concrete column according to claim 1, wherein the concrete contains an expanding material in response to an increase in the short-term allowable stress of the reinforcing steel. 3. The reinforced concrete column according to claim 1, wherein the reinforced concrete column is formed by centrifugal force forming. 4. The reinforcing steel used in the expansion material is used for the amount of strain at the short-term allowable stress of the reinforcing steel of a standard reinforced concrete column whose crack width becomes 0.2 mm or less at the short-term allowable stress. The reinforced concrete column according to claim 2 or 3, wherein the content is set as an expansion amount based on an increase in the amount of strain at the time of the short-term allowable stress. 5. The reinforcing steel used for the expansion material is used for the amount of strain at the short-term allowable stress of the reinforcing steel of the reference reinforced concrete column whose crack width is 0.2 mm or less at the short-term allowable stress. The range of the content is set as the range of the amount of expansion as the range of the amount of increase in the amount of strain at the time point of the short-term allowable stress and the value obtained by multiplying the amount of increase by 1.13. 4. The reinforced concrete column according to 2 or 3.