JP2004293179A - Prestressed concrete beam and method for manufacturing prestressed concrete beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prestressed concrete beam that can freely control the performance of the beam, and to provide a method for manufacturing the prestressed concrete beam. <P>SOLUTION: The prestressed concrete beam 1 is composed of a tendon 2 extending in the longitudinal direction of the prestressed concrete beam 1, a fixing fitting 4 crimped and joined to be paired at a prescribed position of the tendon 2 in a state of introducing prestress, and concrete 3 for burying them. The prestressed concrete beam 1 forms a prestress valid region 1a holding the prestress over a long period in a region sandwiched between the paired fixing fittings 4 by burying the paired fixing fittings 4 in the concrete 3 fixed at the position, and forms prestress decline or an invalid region 1b easy to diminish the prestress out of the region sandwiched between the paired fixing fittings 4, namely, between the fixing fitting 4 and the end of the prestressed concrete beam 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-performance prestressed concrete beam and a method for manufacturing the prestressed concrete beam.
[0002]
[Prior art]
Conventionally, prestressed concrete beams of precast concrete (hereinafter, PCa) have been applied to reinforced concrete super-high-rise houses in order to cope with an increase in span. As a low-cost PCa-made prestressed concrete beam applicable to a super-high-rise house, a pretension method manufactured in a factory or the like is often used. Here, the pretensioned prestressed concrete beam means a tension member installed on a prestress introduction stand, and a prestressing force is introduced into the tension member. It is manufactured by cutting the tendon at both ends of the prestressed concrete beam after demolding, and releasing the tendon from the prestress introduction stand.
[0003]
In the prestressed concrete beam having such a configuration, the prestress is easily lost because the tendon is opened at the end. In addition, when an earthquake or the like occurs, these ends, which serve as joints with other members such as columns, are repeatedly deformed. Has a problem that it is easy to expand.
In view of such circumstances, in Patent Document 1, the disappearance of prestress at both ends of the prestressed concrete beam is suppressed by providing an auxiliary fixing means for the tension member at each end of the prestressed concrete beam.
[0004]
[Patent Document 1]
JP-A-9-309105
[Problems to be solved by the invention]
However, the prestressed concrete beam having such a configuration promotes the crushing of the concrete in which the tendon is buried due to the presence of prestress at the end that is easily deformed when an earthquake or the like occurs. In addition, the effective area of the prestress tends to decrease with the promotion of concrete crushing, and it is not always effective to introduce the prestress to the end.
[0006]
In view of the above circumstances, the present invention is to provide a prestressed concrete beam and a method of manufacturing a prestressed concrete beam that can clearly distinguish a portion where a prestress is introduced and a portion where the prestress is not introduced, and can freely control the performance of the beam. The purpose is.
[0007]
[Means for Solving the Problems]
The prestressed concrete beam according to claim 1, wherein the prestressed concrete beam includes a tension member that extends in a longitudinal direction and has a prestressing force introduced therein, and a concrete in which the tension member is embedded. A fixing metal having a cross-sectional diameter larger than that of the tendon, and having a through hole through which the tendon penetrates, is fixed in a pair at a predetermined interval at a position buried in the concrete, and I have.
[0008]
The prestressed concrete beam according to claim 2 is characterized in that an unbonding process is performed on an outer peripheral surface of the tendon except for a region sandwiched between the pair of fixing hardware.
[0009]
4. The prestressed concrete beam according to claim 3, wherein a threaded steel rod is used as the tension member, and a threaded surface that fits the threaded steel rod is formed on a peripheral surface of a through hole provided in the fixing hardware. It is characterized by being done.
[0010]
The method for manufacturing a prestressed concrete beam according to claim 4 is a method for manufacturing a prestressed concrete beam including a tension member that extends in a longitudinal direction and into which a prestress is introduced, and a concrete in which the tension member is embedded. In the state where the tendon is penetrated through each through hole of the fixing hardware to be formed, the tendon is placed on a prestress introduction stand, and a first step of introducing the prestress and a pair of fixing at a predetermined position of the tendon It is characterized by comprising a second step of fixing hardware and a third step of casting concrete so that both are buried.
[0011]
The method of manufacturing a prestressed concrete beam according to claim 5 is characterized in that, in the second step, an unbonding process is further performed on an outer peripheral surface of the tension member except for a region sandwiched between the pair of fixing hardware.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show a prestressed concrete beam and a method of manufacturing the prestressed concrete beam according to the present invention. The present invention provides a prestressed concrete beam, in which a fixing metal member forming a pair is fixed to a tension member constituting a prestressed concrete beam with a predetermined spacing, and the fixing metal member is buried in concrete together with the tension member. A clear performance classification is provided in which the region between the sandwiched portions is defined as an effective region of the prestress, and the region outside the region between the fixing hardware is defined as a reduced or invalid region of the prestress.
[0013]
As shown in FIG. 1A, the prestressed concrete beam 1 includes a tendon 2, concrete 3, and fixing hardware 4. The tendon 2 is disposed so as to be located in the longitudinal direction of the prestressed concrete beam 1 and is buried in the concrete 3 in a state where the prestress is introduced. In the present embodiment, a PC steel wire made of a strand is used for the tendon 2, but the present invention is not limited to this, and it is possible to introduce a prestress, and the concrete 3 adheres to the outer peripheral surface. Any of easy-to-use PC steel wires, steel materials, or steel bars may be used.
[0014]
Further, the fixing members 4 are arranged in pairs in the above-mentioned tension member 2 at a predetermined interval. The fixing hardware 4 is made of a rigid member such as a steel material, and has a cross-sectional diameter larger than that of the tension member 2 as shown in FIG. A hole 4a through which the material 2 can pass is provided. These tendons 2 are penetrated through the holes 4a, are crimp-bonded to predetermined positions where prestress is introduced into the tendons 2, and are embedded in the concrete 3.
[0015]
In the prestressed concrete beam 1 having such a configuration, the pair of fixing hardware 4 crimped to the tension member 2 is embedded in the concrete 3 and the position thereof is fixed, so that the pair of fixing metal 4 is formed. It functions to always hold the prestress introduced from the beginning to the tendon 2 in the sandwiched region. On the other hand, the tension members 2 located outside the region sandwiched by the pair of fixing hardware 4, that is, between the fixing hardware 4 and the end of the prestressed concrete beam 1, are not fixed at the end of the prestressed concrete beam 1. Because it is open, the pre-stress introduced from the beginning cannot be maintained for a long time. Thereby, as shown in FIG. 1 (b), the prestressed concrete beam 1 has a prestress effective area 1a in which the prestress is held by the tendon 2 at the center, with the fixing hardware 4 forming a pair. The prestress reduction or ineffective region 1b is formed at both ends so that the prestress is easily lost.
[0016]
An unbonding agent 7 is attached to the prestressed concrete beam 1 outside the region sandwiched by the pair of fixing hardware 4, that is, on the outer peripheral surface of the tension member 2 in the prestress reduction or ineffective region 1b. The unbonding agent 7 is generally used for the purpose of insulating the steel material and the concrete, and also in the present embodiment, the structure in which the concrete 3 does not adhere to the tendon 2 is formed.
The prestressed concrete beam 1 having the configuration in which the unbonding agent 7 is applied has the prestress reduction or ineffective area 1b as an ineffective area of complete prestress, and when a bending moment acts as an external force in this area, Since no concrete compressive edge stress is generated by prestressing, sufficient bending deformation performance can be ensured until the concrete is crushed in the same manner as a normal reinforced concrete beam.
It is not always necessary to apply the unbonding agent 7 to the prestress-reduced or ineffective area 1b of the prestressed concrete beam 1.
[0017]
A method of manufacturing the prestressed concrete beam 1 having the above-described configuration will be described below in detail with reference to FIG.
The prestress introduction gantry 5 used in the manufacturing includes a concrete form 5b, a support 5a arranged in pairs so as to sandwich the concrete form 5b from the longitudinal direction, and a not-shown support provided on the support 5a. It is composed of a prestress introduction mechanism.
[0018]
In the first step, as shown in FIG. 3 (a), both ends of the tension member 2 having the concrete form 5b penetrated are fixed to each pair of columns 5a, and a prestress introducing mechanism (not shown) is provided. Through this, a desired amount of tension is introduced into the tendon 2. At this time, the tension member 2 is provided with a pair of fixing brackets 4 in advance, and when the tension member 2 is attached to the prestress introduction pedestal 5, the pair of fixing brackets 4 is fitted with through holes. The tension member 2 is attached so as to be located inside the concrete formwork 5b while penetrating the tension member 2 through 4a.
[0019]
In the second step, as shown in FIG. 3B, a range in which the prestress is to be maintained for a long period of time for the tendon 2 in which a desired amount of prestress is introduced is determined. The fixing metal fittings 4 forming a pair are positioned at positions where a range is formed, and the fixing metal fittings 4 forming a pair are fixed to the tension member 2 by pressure bonding.
On the other hand, the unbonding agent 7 is applied to the outer circumferential surface of the tension member 2 located outside the region sandwiched between the pair of fixing brackets 4. The unbonding agent 7 does not always need to be applied.
[0020]
In the third step, as shown in FIG. 3 (c), concrete is poured into a concrete form 5b so as to embed both the tension member 2 and the fixing metal member 4 forming a pair. The tension member 2 is released from the support 5a and the mold is removed.
As a result, the prestressed concrete beam 1 having the prestressed effective area 1a in the area sandwiched by the pair of fixing brackets 4 and the other area, that is, the prestressed reduced or ineffective area 1b near both ends, is formed.
[0021]
In this embodiment, a strand is used for the tendon 2, but the present invention is not limited to this. For example, as shown in FIG. 2B, a threaded PC steel rod whose surface is threaded is used. May be used. In this case, by forming a threaded surface on which the threaded PC steel rod fits in the inner peripheral surface of the hole 4a provided in the fixing member 4, the fixing member can be easily fixed at a predetermined position of the tension member 2. 4 can be fixed.
Further, as shown in FIG. 2 (c), the fixing bracket 4 may have a shape that can be divided, and any fixing member that can be easily and securely fixed to a predetermined position of the tendon 2 can be used. May be used.
[0022]
According to the configuration described above, in the prestressed concrete beam 1, the fixing hardware 4 is fixed to the tension member 2 in a pair with a predetermined spacing, and the fixing metal 4 forming a pair with the tension material 2 is embedded. Therefore, the prestressed effective region 1a in which the prestress is retained for a long time is located within the range sandwiched by the pair of fixing hardware 4, and the prestressed concrete beam 1 is out of the region sandwiched by the pair of fixing hardware. Prestress reduction or ineffective regions 1b where prestress is likely to disappear can be formed near both ends, and the performance of the beam related to the presence or absence of prestress can be systematically classified with a simple configuration.
Further, the prestressed effective area 1 sandwiched between the pair of fixing hardware 4 can prevent the prestress from decreasing even during an earthquake.
[0023]
Further, a prestressed reduced or ineffective region 1b is formed near both ends of the prestressed concrete beam 1, so that when these are applied to a structure as shown in FIG. In the case where cracks occur due to repeated deformation at both ends serving as joints with the column 6 due to the occurrence of the like, it is possible to prevent the prestress from decreasing in the effective region.
[0024]
When the unbonded material 7 is attached to the prestress-reduced or ineffective region 1b, a completely ineffective region of prestress is formed, so that deformation performance can be expected, and the prestressed effective region 1a extends to both ends. It is possible to improve the seismic safety as compared with a rigid structure using a beam having a groove.
[0025]
By using a threaded PC steel rod as the tension member 2 and forming a threaded surface on which the threaded PC steel rod fits in the inner peripheral surface of the hole 4 a provided in the fixing bracket 4, tension can be easily achieved. Positioning and fixing to the material 2 can be performed.
[0026]
According to the method of manufacturing the prestressed concrete beam 1, the fixing metal 4 forming a pair is crimped to a predetermined position of the tendon 2 into which the prestress has been introduced, and then the concrete 3 may be cast so as to bury them. Therefore, it is possible to systematically classify the performance of the prestressed concrete beam 1 related to the presence or absence of prestress, without requiring complicated work.
[0027]
Further, the position and the range of the prestressed effective region can be freely determined by appropriately changing the arrangement position of the pair of fixing hardware 4 with respect to the tension member 2 and the spacing between the pair of fixing hardware 4. Thus, the performance of the prestressed concrete beam 1 can be freely controlled.
[0028]
【The invention's effect】
According to the prestressed concrete beam according to claim 1, a prestressed concrete beam including a tension member that extends in the longitudinal direction and into which a prestressing force is introduced, and a concrete in which the tension member is embedded. The fixing metal having a cross-sectional diameter larger than that of the tendon material and having a through hole through which the tendon material penetrates is fixed in a pair at predetermined intervals at positions buried in the concrete. The pre-stressed effective area in which the prestress is retained for a long time within the area sandwiched by the pair of anchoring hardware, and the pre-stressed area outside the area sandwiched by the pair of anchoring hardware, that is, near the both ends of the prestressed concrete beam Prestress reduction or ineffective area where stress is easy to disappear can be formed. It is possible to distinguish the performance. Further, the prestressed effective region sandwiched between the pair of fixing hardware can prevent the prestress from decreasing even during an earthquake.
[0029]
According to the prestressed concrete beam of claim 2, since the unbonding process is performed on the outer peripheral surface of the tension member except for the region sandwiched by the pair of fixing hardware, the vicinity of both ends of the prestressed concrete beam is provided. In this case, a completely pre-stressed ineffective area is formed, so even if an earthquake or the like occurs and the both ends that are the joints with the columns are repeatedly deformed, the compressed edge concrete is hardly crushed, Compared with a rigid structure using a beam in which a prestressed effective area is formed up to both ends, it is possible to improve the earthquake resistance safety.
[0030]
According to the prestressed concrete beam according to claim 3, a threaded steel rod is used as the tension member, and a threaded surface fitted to the threaded steel rod is formed on a peripheral surface of a through hole provided in the fixing hardware. Is formed, it is possible to easily perform positioning and fixing to the tendon material.
[0031]
According to the method for manufacturing a prestressed concrete beam according to claim 4 or 5, a method for manufacturing a prestressed concrete beam including a tension member that extends in a longitudinal direction and into which a prestress is introduced and a concrete in which the tension member is embedded is provided. A first step of installing the tension member on a prestress introduction stand in a state where the tension member penetrates through the through holes of each pair of fixing hardware, and a first step of introducing the prestress and a predetermined position of the tension member And a third step of casting concrete so as to bury both of them. Alternatively, in the second step, an unbonding process is performed on the outer peripheral surface of the tendon except for the region sandwiched between the pair of fixing hardware.
This makes it possible to systematically classify the performance of the prestressed concrete beam according to the presence or absence of prestress, while eliminating the need for complicated work.
[0032]
Further, the position and the range of the prestressed effective area can be freely determined by appropriately changing the arrangement position of the pair of fixing hardware with respect to the tendon material and the separation interval of the pair of fixing metal, so that the prestressed concrete can be determined. It is possible to freely control the performance of the beam.
[Brief description of the drawings]
FIG. 1 is a diagram showing details of a prestressed concrete beam according to the present invention.
FIG. 2 is a view showing a fixing hardware of a prestressed concrete beam according to the present invention.
FIG. 3 is a diagram showing a method for manufacturing a prestressed concrete beam according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Prestressed concrete beam 2 Tensile material 3 Concrete 4 Fixing hardware 5 Prestress introduction stand 6 Column 7 Unbonding agent

Claims (5)

A tendon member extending in the longitudinal direction and having a prestressing force introduced therein, and a prestressed concrete beam including concrete burying the tendon member,
A fixing metal having a cross-sectional diameter larger than that of the tendon material and having a through hole through which the tendon material penetrates is attached to the tension member in a pair at a predetermined interval at a position buried in the concrete. A prestressed concrete beam characterized by being made. The prestressed concrete beam according to claim 1,
A precast concrete beam, wherein an unbonding treatment is applied to an outer peripheral surface of a tension member except for a region sandwiched between the pair of fixing hardware. The prestressed concrete beam according to claim 1 or 2,
A pre-stressed concrete beam, wherein a threaded steel rod is used as the tension member, and a threaded surface that fits into the threaded steel rod is formed on a peripheral surface of a through hole provided in the fixing hardware. . In a state where the tendon is penetrated into the through holes of each of the fixing hardware forming a pair, the tendon is installed on a prestress introduction stand, and the first step of introducing the prestress and the pair is placed at a predetermined position of the tendon. A second step of fixing the fixing hardware to be formed;
A method of manufacturing a prestressed concrete beam, comprising the steps of: casting concrete so that both are buried, and after hardening, releasing the tendon from the prestress introduction stand. The method for manufacturing a prestressed concrete beam according to claim 4,
In the second step, a method of manufacturing a prestressed concrete beam, further comprising performing an unbonding process on an outer peripheral surface of a tendon except for a region sandwiched between the pair of fixing hardware.

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