JP5947140B2 - Prestressed concrete construction method and prestressed concrete structure - Google Patents

Description

  The present invention relates to a pre-tensioned prestressed concrete structure.

  Prestressed concrete structures are widely used in the civil engineering and construction fields as a useful structural form that realizes a large span and a large space. As a typical press tracing system, there is a post-tension system that performs tension work at a construction site. A wide variety of post-tension methods have been developed, but in general, the fixing tool (anchor head, bearing plate, spiral reinforcement for bearing support, etc.) protrudes outside the prestressed concrete member. (For example, Patent Literature 1 and Non-Patent Literature 1), and the fixing tool is embedded by post-molding mortar or the like.

  However, for example, when the fixing tool is located at the beam-column joint, it is necessary to install the fixing tool so as not to interfere with the reinforcing bars such as the main bars of the columns and beams and the shear reinforcement bars. Since the bars are overlaid, sufficient consideration is required for the concrete filling property, which makes the construction complicated.

  In addition, depending on the presence of the fixing tool, it may be necessary to increase the size of the column-beam joint or the column or beam member. In recent years, with the spread of seismic isolation and vibration control technology, there is a tendency to reduce the cross-section of members by actively using high-strength materials, but the presence of anchors has become a major design and construction issue .

  Therefore, as a post-tension type press tracing system that does not require a fixing tool, a tension force is introduced to the member by adhesion of PC steel and concrete, and a fixed distance from the end surface of the member (the fixing length in the pre-tension method). In the case of the above-mentioned, the fixing by the adhesion resistance described above is proposed (Patent Document 2).

JP 2004-131969 A JP 2011-184871 A

“Prestressed Concrete VSL Method Design and Construction Standards”, VSL Association, Revised February 1, 2012

  The method of Patent Document 2 uses the mechanical principle of a pre-tension method in which tension is introduced into a member by the adhesion of PC steel and concrete, but when using PC steel stranded wire, the fixing length is May be longer. For example, the fixing length possible with the adhesion resistance force of PC steel stranded wire varies depending on the steel material diameter, but generally 40 to 70 times the steel material diameter (1m or more for φ15.2 stranded wire) is required. In many cases, it is difficult to fix in the beam-column joint.

  An object of the present invention is to reduce the size of the fixing unit while ensuring the necessary fixing force.

According to the present invention, a plurality of beams are installed between a plurality of columns, and a prestressed concrete structure construction method for introducing prestress into the plurality of beams,
Tensioning a PC pipe twisted through a sheath tube embedded in a concrete member and a bearing plate disposed on both end faces of the concrete member to introduce prestress into the concrete member;
A filling step of filling the sheath tube with a filler;
A release step of releasing the tension of the PC steel stranded wire and removing the bearing plate after the strength of the filler is expressed;
Wherein the one end of the PC steel twisted wire, while the hardware disposed in the sheath tube is pressure wear, the other end of the PC steel twisted wire, the hardware is not attached,
The prestressed concrete structure , wherein the one end of the PC steel stranded wire is located at a column beam joint, and the other end of the PC steel stranded wire is located at an intermediate portion of the beam. A construction method is provided.

Further, according to the present invention, in a prestressed concrete structure in which prestress is introduced into a plurality of beams installed between a plurality of columns , a sheath tube embedded in a concrete member and a PC inserted through the sheath tube A steel stranded wire and a filler filled in the outer periphery of the PC steel stranded wire in the sheath tube, and one end of the PC steel stranded wire is located at a column beam joint , placed hardware are pressure wear, and the other end of the PC steel twisted wire is located in the middle part of the beam, the prestressed concrete structure, characterized in that the hardware in the sheath tube is not attached Provided.

  According to the present invention, it is possible to reduce the size of the fixing unit while ensuring the necessary fixing force.

(A) is explanatory drawing of the fixing structure which concerns on one Embodiment of this invention, (B) is sectional drawing which follows the line II of FIG. 1 (A). (A) And (B) is explanatory drawing of the manufacturing method which concerns on one Embodiment of this invention, (C) is the elements on larger scale of FIG. 2 (B). (A) thru | or (C) are explanatory drawings of the said manufacturing method. (A) And (B) is explanatory drawing of the said manufacturing method, (C) is a figure which shows another example of arrangement | positioning of a steel pipe. (A) And (B) is explanatory drawing of another example. FIG. 6 is an explanatory diagram of a conventional fixing structure example as a comparative example.

<First Embodiment>
FIG. 1A is an explanatory diagram of a fixing structure A according to an embodiment of the present invention, and an example in which the fixing structure of the present invention is applied to a column-to-column junction 100 between columns (not shown) and beams 101 to 103. Is a diagram schematically showing a cross-sectional view. The main bars, shear reinforcement bars and the like of the columns and beams 101 to 103 are not shown. FIG. 1B is a cross-sectional view taken along line I-I in FIG.

  The fixing structure A constitutes a fixing portion of the beam 101 which is a PC (prestressed concrete) beam member. A sheath tube 10 is embedded in the beam 101 over substantially the entire length thereof, and an insertion space for a PC steel stranded wire 20 for introducing prestress into the beam 101 is formed. The sheath tube 10 is, for example, a spiral sheath tube, and includes a fixing unit 10a positioned at the end of the beam 101 and an intermediate unit 10b. In the present embodiment, the diameter gradually increases from the intermediate portion 10b toward the fixing portion 10a, but the entire sheath tube 10 may have the same diameter.

  In the case of this embodiment, it is assumed that the cross-sectional dimension is made smaller than that of a general PC member by using high-strength concrete for the columns and beams 101 to 103 and the column-beam joint portion 100. For example, the column is 600 mm square. The width of the beam 101 is about 400 mm.

  Assuming such a high prestress level suitable for concrete strength, assuming that seven PC steel stranded wires 20 inserted into one set of sheath tubes 10 are inserted with a diameter of 15.2 mm. However, the diameter and number of the PC steel stranded wires 20 are appropriately selected according to the design contents. A mortar 100 ′ is post-fired near the end of the PC steel stranded wire 20.

  Each PC steel twisted wire 20 is pre-pressed with a steel pipe 30 as a steel grip, and is located in the sheath pipe 10 (in the fixing portion 10a). In this embodiment, the steel pipe 30 is pre-crimped, but it is not limited to a steel pipe as long as it is a hardware that can be crimped to a PC steel stranded wire.

  The sheath tube 10 is filled with a filler 40. The filler 40 is preferably a grout material having a strength equal to or higher than that of the member concrete. In recent years, ultra-high strength grout material (Fc150) has also been developed and commercialized, and there are various types from the conventional Fc30 class to Fc150. The strength of the grout material can be appropriately selected according to design conditions, performance conditions, and the like.

  In the fixing structure A of the present embodiment having such a configuration, the PC steel stranded wire 20 can be fixed in the sheath tube 10 by the bearing effect of the steel tube 30 and the filler 40. At that time, the hoop tension effect of the sheath tube 10 can also be expected. Since the steel pipe 30 exists in the sheath pipe 10, there is no fixing tool outside the target concrete member.

  For this reason, for example, the fixing portion can be made more compact than a case where a fixing tool is embedded as in the VSL method. FIG. 6 is an explanatory view of a conventional fixing structure example by the VSL method in a similar case as a comparative example. In the example of FIG. 6, the spiral reinforcement 1, the bearing plate 2, the anchor head 3, and the steel pipe sleeve 4 are embedded in the column beam joint 100, and in order to obtain a cover thickness equivalent to this embodiment, the column beam It is necessary to increase the size of the joint 100. In addition, the space for arranging the main bars and the like is small, and the range of the trailing portion 100 ″ of the column beam joint 100 is also large.

  In the fixing structure A, as described above, stress is transmitted from the steel pipe 30 pre-crimped to each PC steel twisted wire 20 to the concrete via the filler 40 and the sheath pipe 10, so that the bearing plate 2 is finally unnecessary. Become. Further, since the sheath tube 10 plays the role of the spiral muscle 1, this is not necessary, and the arrangement of the bars near the fixing portion can be simplified. The fixing structure A can be downsized in that the fixing tool is not embedded in this way, and the bar arrangement is also advantageous.

  Next, for example, the necessary fixing force can be ensured with a shorter fixing length as compared with the prior art using only the adhesion resistance force between the PC steel material and the filler.

  Thus, in the present embodiment, the fixing unit can be made compact while ensuring the necessary fixing force.

  In addition, in this embodiment, since it is going to introduce tension | tensile_strength into a member (beam 101) by the bearing effect of the steel pipe 30 and the filler 40, among the sheath pipe | tubes 10, the fixing | fixed part in which the steel pipe 30 exists inside In 10a, the expansion of the PC steel stranded wire 20 itself and the bearing stress of the filler 40 by the steel pipe 30 increase, and a compressive stress is generated in the circumferential direction on the inner surface of the sheath pipe 10 in the vicinity thereof.

  Therefore, for the purpose of restraining it by the hoop tension of the sheath tube 10 and suppressing the expansion of the filler 40 in the vicinity of the steel tube 30, the thickness of the fixing portion 10a is made thicker than the thickness of the intermediate portion 10b (thin sheath sheath). The steel strip may be thicker). Alternatively, in order to ensure the transmission of stress from the sheath tube 10 to the member concrete, the fixing portion 10a has an outer shape with higher adhesion of concrete than the intermediate portion 10b (for example, surface irregularities are dense or deep). Also good.

  Next, a method for manufacturing a PC member employing the fixing structure A will be described with reference to FIGS.

  FIG. 2 (A) shows a state in which a PC steel stranded wire 20 is inserted into a concrete member B to which prestress is introduced. The concrete member B may be a PCa member or a spot-on-site member, and the sheath tube 10 is embedded and a hole penetrating from one end to the other end is formed. After the concrete member B reaches a predetermined strength, the PC steel stranded wire 20 is inserted into the hole. When the number of PC steel stranded wires 20 is large and the total length is long, a plurality of PC steel stranded wires 20 bundled together may be connected to a wire rope, and the insertion work may be performed manually or by an electric winch.

  A steel pipe 30 is pre-crimped to the PC steel stranded wire 20 and located in the sheath pipe 10. The steel pipe 30 is disposed with its position adjusted so as to be positioned at the end of the concrete member B serving as a fixing portion.

  Next, as shown in FIG. 2 (B), the end portion of the hole of the concrete member B is filled with an outflow prevention material 50. The outflow prevention material 50 is a sealing material or the like that prevents leakage of the filling material that will be filled into the sheath tube 10 later, and may be any material that can be easily removed in a subsequent process, such as foaming urethane. Moreover, the bearing plate 51 is arrange | positioned in the both end surfaces of the concrete member B, the PC steel twisted wire 20 is inserted, and the jack chair 52, the anchor head 53, and the tension gripper 54 are sequentially arranged outside the bearing plate 51. . A gripper chair 55 is also arranged on the tension side. The anchor head 53 and the tension gripper 54 will be described with reference to FIG.

  The tension gripper 54 is a steel sleeve having a tapered outer shape and a circular cross section. The tension gripper 54 is inserted through each PC steel stranded wire 20. The anchor head 53 is formed with a hole through which each PC steel stranded wire 20 is inserted. One end of the hole is formed in a tapered shape into which the tension gripper 54 bites. When the tension of the PC steel stranded wire 20 is released, the tension gripper 54 is likely to be drawn into the hole of the anchor head 53 as the PC steel stranded wire 20 contracts. Increases and the tension state of the PC steel stranded wire 20 is maintained. In addition, the maintenance mechanism of the tension state of such a PC steel twisted wire 20 is not restricted to this, Various well-known techniques are employable.

  A concave portion serving as a space for arranging the tension gripper 54 is formed on one end face of the gripper chair 55, and the peripheral edge thereof is in contact with the anchor head 53, while the bottom surface of the recess is in contact with the tension gripper 54. .

  Next, as shown in FIG. 3A, the jack 56 is disposed on the tension side. And the pre-stress is introduced into the concrete member B by tensioning the PC steel stranded wire 20 (tensile process). The jack 56 tensions the PC steel stranded wire 20 and presses the tension gripper 54 on the anchor head 53 side via the gripper chair 55. When the introduction of the prestress is finished, the jack 56 is removed. With the above mechanism, the tension state of the PC steel stranded wire 20 and the prestress introduction state of the concrete member B are maintained.

  Next, as shown in FIG. 3B, the sheath material 10 is filled with a filler 40 (filling step). After the strength of the filler 40 is expressed, the tension of the PC steel stranded wire 20 is released to move to the operation of removing the bearing plate 51 and the like (release process). First, as shown in FIG. 3C, the PC steel stranded wire 20 is cut at an appropriate portion (position of the line L in the same figure). Cutting can be performed with a gas or a cutter. The PC steel stranded wire 20 is composed of a large number of small-diameter strands. By cutting the thin-diameter strands one by one or several at a time, the impact of releasing tension is relatively small and efficient. Work is possible. Thereafter, the bearing plate 51, the jack chair 52, and the anchor head 53 are removed.

  Next, as shown in FIG. 4 (A), the outflow prevention member 50 is removed and the end of the PC steel stranded wire 20 is cut so as not to protrude from the concrete member B. Finally, as shown in FIG. 4B, the end of the hole through which the PC steel stranded wire 20 is inserted is filled with mortar B '.

  Thus, in the manufacturing method of this embodiment, it is not necessary to leave the fixing tools such as the bearing plate 51, the jack chair 52, and the anchor head 53, and they can be reused, and the construction cost can be reduced. Moreover, tension work (FIG. 3 (A)) is sufficient once.

  In addition, in this embodiment, although each steel pipe 30 has been arrange | positioned in the position (the same position in the wire direction of the PC steel twisted wire 20) which overlaps in the radial direction of the sheath tube 10, it arrange | positions shifting in the line direction of the PC steel twisted wire 20 May be. FIG. 4C shows an example. By shifting the position of the steel pipe 30 in this way, the sheath pipe 10 having a smaller diameter can be employed, and the fixing portion can be further downsized. In addition, it is not necessary to shift the positions of all the steel pipes 30 from each other, and at least the positions of the adjacent steel pipes 30 may be shifted.

Second Embodiment
In the first embodiment, the steel pipe 30 is disposed in both the tension side and the fixing side fixing portions. However, the steel pipe 30 may be disposed only on one side (for example, the tension side). For example, the fixing force may be secured by the adhesion resistance force between the PC steel stranded wire 20 and the filler 30 without providing the steel pipe 30 in a portion where the fixing length can be long. An example will be described with reference to FIGS. 5 (A) and 5 (B).

  FIG. 5A assumes a case where prestress is introduced by a PC steel stranded wire 20 extending over the entire area of the plurality of beams 200 in a structural example in which a plurality of beams 200 are installed between the plurality of columns 201. ing. Reference numeral P <b> 1 indicates a fixing portion, which is two places at the end of the series of beams 200.

  In the case of the structure example in which the tension force is introduced over a plurality of spans as described above, instability secondary stress may increase and become inefficient at the joint portion of the column beam as indicated by an arrow. In such a case, as shown in FIG. 5 (B), the pre-stress is introduced by the PC steel stranded wire 20 in units of two groups divided by an intermediate portion, and the section S between the groups is a post-construction RC structure. Join as. Thereby, an inconstant secondary stress can be reduced. In addition, it is also possible to reduce the statically indeterminate secondary stress by temporarily fixing the column 201 so as to be slidable and fixing it after introducing prestress.

  In the example of the structure shown in FIG. 5B, fixing portions P1 and P2 exist as fixing portions, but the fixing portion P2 has a long distance to the nearest pillar 201. Therefore, the fixing structure P using the steel pipe 30 is used for the fixing section P1, and the steel pipe 30 is not used for the fixing section P2, and the fixing force is secured by the adhesion resistance force between the PC steel stranded wire 20 and the filler 30. May be.

Claims (3)

A construction method of a prestressed concrete structure in which a plurality of beams are installed between a plurality of columns, and prestress is introduced into the plurality of beams,
Tensioning a PC pipe twisted through a sheath tube embedded in a concrete member and a bearing plate disposed on both end faces of the concrete member to introduce prestress into the concrete member;
A filling step of filling the sheath tube with a filler;
A release step of releasing the tension of the PC steel stranded wire and removing the bearing plate after the strength of the filler is expressed;
Wherein the one end of the PC steel twisted wire, while the hardware disposed in the sheath tube is pressure wear, the other end of the PC steel twisted wire, the hardware is not attached,
The prestressed concrete structure , wherein the one end of the PC steel stranded wire is located at a column beam joint, and the other end of the PC steel stranded wire is located at an intermediate portion of the beam. Construction method. The sheath tube disposed at one end of the PC steel stranded wire is thicker than the other portion of the sheath tube or has an outer shape with high adhesion. The construction method of the prestressed concrete structure of Claim 1. In a prestressed concrete structure in which prestress is introduced into multiple beams built between multiple columns ,
A sheath tube embedded in a concrete member;
And PC steel twisted wire, which is inserted into the sheath tube,
A filler filled in the outer periphery of the PC steel stranded wire in the sheath tube,
One end of the PC steel twisted wire is located in Column Joints, other end of the hardware disposed in the sheath tube are pressure wear, and the PC steel twisted wire is located in the middle portion of the beam The prestressed concrete structure is characterized in that the hardware is not attached in the sheath tube .

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