JP7355644B2 - How to adjust the tension of PC steel materials - Google Patents

Description

The present invention adjusts the tension applied to the prestressing steel materials (hereinafter referred to as tension (including releasing the tension force by adjusting it to 0), in particular, it is preferable to adjust the tension force applied to the prestressing steel material even if the work space (work space) is small. Regarding the technology that can be used. In the present invention, the PC steel material includes a PC steel wire and a PC steel stranded wire. In addition, since the present invention is preferably applied to prestressed concrete structures, in particular to an external cable method using an external cable that is not buried in concrete (for reinforcement), such an embodiment will be described. The present invention is not limited to such external cables.

The most common PC anchorage system for anchoring PC steel members (PC cables) made of PC steel wire or PC steel strands consists of a casting block and an anchor head embedded in concrete. After tensioning, the PC steel wire or the PC steel strand is fixed to the anchor head by a wedge, and the casting block and sheath are filled with grout through the grout hole provided in the casting block to complete anchoring.

Wedge fixing in such fixing work (using a fixing tool (fixing grip) consisting of a wedge and a sleeve with a tapered hole, the PC steel wire is bitten at the inner circumference of the wedge, and the taper between the outer circumference of the wedge and the sleeve is When the wedge is fixed with a hole (fixed with a hole), the wedge protrudes outside the sleeve when tension is applied, but when the tensile load of the jack is released (unloaded) during fixation, the wedge returns to the sleeve due to the return (loosening) of the PC steel wire. As it sinks inward, a set amount occurs, and a decrease in prestress (set loss) occurs by that amount. This set loss has a greater effect as the wire length (member length) is shorter than that of PC steel, and its proportion to the design prestress is also large, which may make it difficult to introduce the design prestress. Therefore, it is necessary to correct this set amount. As a system for this correction work, the following technique is known, which was filed as a patent application by the applicant of the present application and was registered as Patent No. 6131292 (Patent Document 1).

The set amount correction jig disclosed in Patent Document 1 reduces the labor of repeatedly attaching and detaching a heavy hydraulic jack in a PC structure where a set amount occurs during tensioning and fixing work, and is easy to use in narrow positions. The following configuration is provided for the purpose of reducing the number of work steps and correcting the set amount. This set amount correction jig is used to apply compressive force to the PC structure by firstly tensioning the prestressed steel material, and is also used for secondary tensioning to correct the set amount of the prestressed steel material using a ring nut. A setting amount correction jig for a prestressing steel material, which is attached to the tip of a hydraulic jack and includes a main body, a fixed ring, and a movable ring, the main body being substantially hollow with a center hole through which the prestressing steel material passes. A fixing device having a cylindrical shape and having a ring nut on the side of the bearing pressure plate, and a fixed ring and a movable ring each having a shape symmetrical about the axis of the PC steel material are housed, and the hydraulic jack is placed on the side opposite to the bearing pressure plate. is attached, and the fixing ring is provided on the inner surface of the hollow cylinder of the main body so that it cannot rotate around the axis, and has a ring of the same thickness in the axial direction at a predetermined central angle around the axis. The movable ring is provided with a plurality of fixed bearing pressure parts, and the movable ring is rotatably provided around the axis on the inner surface of the hollow cylinder of the main body, and is arranged at a predetermined center angle around the axis in the axial direction. is provided with a plurality of movable bearing pressure parts having the same thickness, and the movable ring is rotated around the axis from a primary tension state in which the fixed bearing pressure part and the movable bearing pressure part overlap. The outer peripheral surface of the ring is provided with a hole for mounting a rotating rod for transitioning to a secondary tension state in which the fixed bearing pressure part and the movable bearing pressure part do not overlap, and the main body part is mounted in the hole. The rotary rod is characterized in that the outer circumferential surface of the portion where the rotary rod is rotated around the axis is notched.

Patent No. 6131292

The set amount correction jig disclosed in Patent Document 1 is capable of correcting the set amount by reducing the number of man-hours and performing easy work in a narrow position while reducing the labor of repeatedly attaching and detaching a heavy hydraulic jack. It is highly effective and has been well received.
By the way, it goes without saying that the tension force of the PC steel material for applying compressive force to the PC structure has various magnitudes (tension load values) depending on the type of the PC structure and the type of the PC steel material. do not have. In particular, when applying a small tension force to the PC steel material, or when applying the tension force accurately to the PC steel material, the following problems occur.

<Issue 1> Sufficient fixing performance cannot be achieved with low tension force In wedge-type fixing devices, when the tension force introduced during construction is small, the wedge tooth profile bites shallowly, resulting in insufficient fixation against impact force. Performance may not be achieved.
On the other hand, in order to deepen the bite of the wedge tooth shape at low tension, after tensioning with normal tension (>low tension), wedges are used to restore the elongation of the tendon to lower tension If you remove it and restore the amount of elongation, it will settle in the new position with low tension, resulting in the wedge teeth cutting into it shallowly.

<Issue 2> It is difficult to finely adjust the tension Even if the tension material is pulled in with a predetermined tension using a tensioning device, the amount of wedge bite (set loss) that occurs during the process of transferring the tension to the wedge-type fixing device It is difficult to adjust the tension to a predetermined tension because the tension is reduced and the amount of biting differs slightly depending on the tension, tension material, and fixing device.

<Issue 3> It is necessary to leave extra length of the tendons even when in service.The tension introduced into the tendons must be released (releasing means adjusting the tension to 0), so it is not necessary to release the tension. (This is included in the adjustment of tension force) In order to do this, it is necessary to leave an extra length of tension material, and the anchoring part will be longer when in service. In addition, in order to release the tension with a wedge-type fixing device, it is necessary to further tighten and stretch in order to remove the wedge, but if the tension that has already been introduced is large, it is not possible to secure enough stretch to move the wedge. Unable to release tension.

Furthermore, although not limited thereto, there is a technique called an external cable method that uses an external cable that is not buried in concrete (installed later) in a prestressed concrete structure in relation to <Problem 1> above. This external cable method involves placing a tension material (PC steel material) that has been treated with anti-corrosion treatment on the outside of the PC structure, and tensioning and fixing the external cable using a fixing device (consisting of a sleeve, wedge, and anchor plate). This is a general term for a structure that applies a prestress force using a deflection unit (which maintains the position of the outer cable and deflects it using a deflection tool attached to the PC structure). If this external cable system is applied to a PC bridge (to which a predetermined prestress force is applied), which is a PC structure, and a low tension force is applied to the external cable, the PC structure itself deforms. Then, the tension of this outer cable increases naturally, and it functions as a cable for applying prestress force to the PC structure and reinforcing the PC structure. Since such an external cable is fixed with low tension when constructing a PC structure, <Problem 1> described above occurs.

<Issue 4> A larger work space (work space) is required than when tensioning. A reaction force mount (chair) is usually used to adjust (including release) the tension force introduced into the tension material. In addition to the hydraulic jack, a reaction frame is also used in case of tension, which requires a large work space.
Furthermore, although not limited to, in relation to <Issue 4> above, when adjusting the tension force of the outer cable in the above-mentioned outer cable method, a large amount of work is required on the anchoring part side that tensions and fixes the outer cable. Space often does not exist and it may not be practical to install a reaction mount and a hydraulic jack.

The present invention was developed in view of the above-mentioned problems (problems) of the prior art, and its purpose is to introduce prestress into a concrete frame of a new PC structure or to introduce prestress into a concrete frame. To provide an adjustment method capable of adjusting the tension force applied to a prestressing steel material in an existing prestressed structure that has already been introduced, without requiring a large work space due to not using a reaction mount. It is.

In order to achieve the above object, the method for adjusting the tension of a PC steel material according to the present invention takes the following technical measures.
That is, a tension adjustment method of a PC steel material according to an aspect of the present invention is a tension adjustment method for adjusting the tension of a PC steel material that is applying compressive force to a prestressed PC structure, The end portion is fixed by a fixing tool provided in a concrete fixing device having a substantially rectangular parallelepiped shape, and the concrete fixing device has a PC steel material for connection on a surface opposite to the surface on which the fixing tool is provided in the longitudinal direction of the PC steel material. is configured to be connectable, and in the connecting step of connecting the connecting PC steel material to the concrete fixing device, the same tension as that of the fixing device is applied at the side where the connecting PC steel material is connected in the longitudinal direction of the PC steel material. a mounting step of attaching an intermediate fixing device to the PC steel material so that the intermediate fixing device is oriented in the direction of the PC steel material; and insertion of the insertion hole of the PC steel material and the connecting PC steel material in a direction away from the concrete fixing device side in the longitudinal direction of the PC steel material. A first bearing plate with holes, a hydraulic jack, a second bearing plate with an insertion hole for the PC steel material and an insertion hole for the connection PC steel material are prepared in this order, and the PC steel material and the PC steel material are inserted into the insertion hole. The connection PC steel materials are inserted through each, and the intermediate fixing device is opposed to one surface of the first bearing pressure plate, the hydraulic jack is opposed to the other surface, and the hydraulic jack is opposed to one surface of the second bearing pressure plate. an installation step of installing the fixing member of the connection PC steel material so that the jack faces the other surface; a jack connection step of connecting the connection PC steel material to the hydraulic jack; a connection PC fixing step of fixing the connection PC steel material with a fixing member on the opposite side of the hydraulic jack; and using the hydraulic jack to reduce the tension of the PC steel material between the intermediate fixing tool and the fixing tool. After the step of sufficiently reducing the tension force and the tension force between the intermediate fixing device and the fixing device being sufficiently reduced, the PC steel material is removed at an arbitrary position between the intermediate fixing device and the fixing device. a cutting step of cutting the connecting PC steel material, the intermediate fixing tool, and the tension releasing step of releasing the tension force by the hydraulic jack to realize a state in which the tension force of the prestressing steel material is released; and a step of removing the first bearing pressure plate, the second bearing pressure plate, and the hydraulic jack.

Preferably, the tension reducing step may be configured to reduce the tension of the PC steel material between the intermediate fixing device and the fixing device to zero.
A tension adjustment method for a prestressed steel material according to another aspect of the present invention is a tension adjustment method for adjusting the tension of a prestressed steel material that applies compressive force to a prestressed PC structure, the method comprising: The section is fixed by a fixing tool provided in a concrete fixing device having a substantially rectangular parallelepiped shape, and the concrete fixing device has a connecting PC steel material on a surface opposite to the surface on which the fixing tool is provided in the longitudinal direction of the PC steel material. the fixing device includes a ring nut, the tension of the prestressed steel material is maintained by the ring nut, a connecting step of connecting the connecting prestressing steel material to the concrete fixing device; an attachment step of attaching an intermediate fixing device to the prestressing steel material in the same tension direction as the fixing device on the side to which the connecting prestressing steel material is connected in the longitudinal direction; A first bearing pressure plate having an insertion hole for the PC steel material and an insertion hole for the connection PC steel material, a hydraulic jack, an insertion hole for the PC steel material, and an insertion hole for the connection PC steel material in a direction away from the fixing device side. A second bearing pressure plate is prepared in this order, and the PC steel material and the connection PC steel material are respectively inserted into the insertion hole, and the intermediate fixing device is opposed to one surface of the first bearing pressure plate. an installation step of installing the hydraulic jack in such a manner that the hydraulic jack faces one surface of the second bearing pressure plate, and the fixing member of the connecting PC steel material faces the other surface of the second bearing pressure plate; a jack connecting step of connecting the connecting PC steel material to the hydraulic jack; a connecting PC fixing step of fixing the connecting PC steel material with a fixing member on the opposite side of the hydraulic jack on the second bearing pressure plate; a tension reducing step of reducing the tension of the prestressed steel material between the intermediate fixing device and the fixing device to a state where the ring nut can rotate; a ring loosening step of loosening the ring nut so as to reduce the tension force; a tension reduction step of releasing the tension force of the hydraulic jack to realize a state in which the tension force of the prestressing steel material is reduced; The method includes a removing step of removing the connecting PC steel material, the intermediate fixing device, the first bearing pressure plate, the second bearing pressure plate, and the hydraulic jack.

Preferably, when realizing a state in which the tension force of the prestressing steel material is 0 in the realizing step, the ring nut may be loosened and removed in the ring loosening step.
More preferably, in the installation step, the hydraulic jack may be installed, the piston of which is set in a state corresponding to release or reduction of tension in the prestressing steel material.

More preferably, the concrete fixing device does not have a space for installing the hydraulic jack on the side where the fixing tool is provided in the longitudinal direction of the PC steel material, and has a space for installing the hydraulic jack on the opposite side. It can be configured to provide.

According to the tension adjustment method for prestressing steel materials according to the present invention, a reaction frame is not used in a newly constructed PC structure in which prestress is introduced into the concrete frame or in an existing PC structure in which prestress is already introduced in the concrete frame. Therefore, it is possible to provide an adjustment method that can adjust the tension applied to the PC steel material without requiring a large working space.

It is a figure which shows the reinforcement example of the prestressed PC bridge 100 to which the tension adjustment method of the PC steel material based on the 1st Embodiment of this invention is preferably applied. FIG. 2 is a sectional view of the concrete fixing device (fixing section 200) shown in FIG. 1. FIG. FIG. 2 is a side view for explaining steps 11 and 12 of the method for adjusting the tension amount of a prestressing steel material according to the first embodiment of the present invention. FIG. 3 is a side view for explaining Step 13 and Step 14 of the method for adjusting the tension amount of a PC steel material according to the first embodiment of the present invention. FIG. 3 is a side view for explaining Step 15 and Step 16 of the method for adjusting the tension amount of a PC steel material according to the first embodiment of the present invention. It is a figure which shows the reinforcement example of the prestressed PC bridge 100 to which the tension adjustment method of the PC steel material based on the 2nd Embodiment of this invention is preferably applied. 7 is a sectional view of the concrete fixing device (fixing section 202) shown in FIG. 6. FIG. It is a side view for demonstrating the procedure 21 and the procedure 22 of the tension amount adjustment method of the PC steel material based on the 2nd Embodiment of this invention. It is a side view for explaining the procedure 23 and the procedure 24 of the tension amount adjustment method of the PC steel material concerning the 2nd embodiment of the present invention. FIG. 7 is a side view for explaining steps 25 and 26 of the method for adjusting the tension amount of a prestressing steel material according to the second embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, the tension amount adjustment method (hereinafter, may be simply described as a tension amount adjustment method or adjustment method) of a PC steel material according to an embodiment of the present invention will be described in detail based on the drawings. Here, for all drawings, if a cross section is shown in a part that is not a cross-sectional view, if the appearance is shown in a part that is a cross-sectional view, if the parts showing a cross-sectional view do not match between the drawings, This may include cases where the front member is not drawn and the rear member is shown as if it is seen through, but these are cases in which the adjustment method according to the embodiment of the present invention is easily understood. In order to facilitate a thorough understanding of the present invention, members according to the present invention are basically shown in cross-sectional views or perspective views without hatching. Further, some caps, packings, sealings, etc. for rust prevention, which are not particularly related to the present invention, are not shown.

Note that the method for adjusting the tension of PC steel materials according to the present invention also applies when adjusting the tension of the PC steel materials of a newly constructed PC structure during construction where prestress is introduced into the concrete framework. It can also be suitably applied to the case where the tension of the prestressing steel material of an existing prestressed structure is adjusted when it is in service.
Further, the PC steel material in the present invention may be a PC steel wire or a PC steel strand made of a plurality of steel wires, and one of the plurality of steel wires may be made of a plurality of thinner steel wires. It may be a wire or a single steel wire.

Furthermore, in the following, male threads, male threads, external threads, male threads, external threads, and external threads are described without distinguishing, and female threads, female threads, female threads, female threads, internal threads, and internal threads are described without distinguishing. Sometimes.

[An example of application example]
As explained in the problem to be solved by the invention, although the application of the present invention is not limited, the tension adjustment method according to the present invention can be applied to a prestressed concrete structure that is not buried in concrete (retrofitted). It is preferably applied to an external cable method using an external cable. The first embodiment will be described in steps 11 to 16 shown in FIGS. 3 to 5 as an example of the tension adjustment method for a PC steel material according to the present invention, using such an outer cable as a target for tension adjustment. As another example of the method for adjusting the tension of PC steel according to the present invention, a second embodiment will be described in steps 21 to 26 shown in FIGS. 8 to 10. Before explaining these two adjustment methods, with reference to FIG. 1 and FIG. A prestressed PC bridge reinforced by preferably applying the tension adjustment method for prestressed steel materials according to the second embodiment will be described with reference to FIGS. 6 and 7. In addition, FIGS. 1 and 2 (showing an example to which the tension adjustment method for PC steel materials shown in FIGS. 3 to 5 is preferably applied) and (showing an example of the tension adjustment method for PC steel materials shown in FIGS. 7 to 10) are preferable. 6 and 7, the ring nut 1300 is provided in FIGS. 6 and 7, but the ring nut 1300 is not provided in FIGS. 1 and 2, and the anchor plate 500 with steel pipe is The difference is that the inner diameter is different. Other than these differences, FIGS. 1 and 2 and FIGS. 6 and 7 basically have the same configuration, and the same configurations are denoted by the same reference numerals and the same explanations will not be repeated. Here, the anchor plate with steel pipe 500 includes an anchor plate 520 (this anchor plate 520 may be simply referred to as a bearing pressure plate 520) that functions as a bearing pressure plate at the end of the steel pipe 510.

An example of reinforcing a prestressed PC bridge 100 using this outer cable method will be described with reference to FIGS. 1 and 2, as well as FIGS. 6 and 7. 1(A) and 6(A) are side views showing a prestressed PC bridge 100 to be reinforced and a reinforcement method using an outer cable method including tension members (PC steel material 300) as outer cables, and FIG. 1(B) and FIG. 6(B) is a front view thereof, and FIG. 1(C) and FIG. 6(C) are an enlarged side view of a portion 1C in FIG. 1(A) and an enlarged side view of a portion 6C in FIG. 6(A). 2 is a sectional view of the concrete fixing device (fixing section 200) shown in FIG. 1, and FIG. 7 is a sectional view of the concrete fixing device (fixing section 202) shown in FIG. 6. In addition, in these figures, one approximately rectangular parallelepiped-shaped concrete fixing device (fixing section 200 in FIGS. 1 and 2, fixing section 202 in FIGS. 6 and 7) is subject to the tension adjustment method. Two PC steel materials 300 can be connected in the left and right directions in FIGS. 1(B) and 6(B), and four connection PC steel materials 810 can be connected in the horizontal and vertical directions in FIGS. 1(B) and 6(B). However, the method for adjusting the tension of the PC steel material according to the present invention is not limited to these numbers. Particularly, in the tension adjustment method of the PC steel material with reference to FIGS. 3 to 5 and FIGS. 8 to 10, which will be described later, one PC steel material 300 is connected to the PC steel material 300 using two connecting PC steel materials 810. The tension is adjusted (including release).

As shown in these figures, the external cable method for reinforcing the prestressed PC bridge 100 is to use a tensile material (PC steel material 300), which is an external cable that has been subjected to rust prevention treatment, to the outside of the prestressed PC structure (prestressed PC bridge 100). The fixing section 200 or the fixing section 202 (composed of a sleeve 1100, wedge 1200, and anchor plate 520 tensions and fixes the outer cable (PC steel material 300), but the fixing section 202 includes a ring nut 1300 in addition to these) A prestressing force is applied by a deflection unit 400 (attached to the prestressed PC bridge 100 to maintain the position of the outer cable and deflect it). This external cable system is applied to the prestressed PC bridge 100 (to which a predetermined prestress force is applied), which is a PC structure, and a low tension force is applied to the outer cable. When the PC bridge 100 itself is deformed (for example, when it bends downward), the tension of this outer cable increases naturally, applying prestress force to the prestressed PC bridge 100, which is a PC structure, and reinforcing it. do. Such external cables are fixed with low tension when constructing the prestressed PC bridge 100, which is a PC structure, and are used when the prestressed PC bridge 100 itself is deformed after the start of service (for example, when it bends downward). 2) The tension material (PC steel material 300) is applied with the specified tension within the standards such as tensile strength without breaking (because it is fixed with low tension during construction, so there is plenty of tension) By doing so, the prestressed PC bridge 100 is reinforced.

In addition, in FIGS. 1(C) and 6(C), various anti-rust treatment members are actually attached to the ends of the tension material (PC steel material 300 covered with sheathing material 302) that is the outer cable. However, in FIGS. 3 to 5 for explaining the first implementation described later as the tension adjustment method for prestressing steel materials according to the present invention, and FIGS. 8 to 10 for explaining the second implementation, A method of adjusting the tension from a state before such a rust-proofing member is attached or a method from a state where it is removed will be explained.

As shown in FIGS. 1 and 2, as well as FIGS. 6 and 7, the ends of the PC steel material 300, which is the target of the tension adjustment method, are provided with approximately rectangular parallelepiped-shaped concrete fixing devices (fixing section 200, fixing section 202). It is fixed by a fixing device (the fixing unit 200 includes a sleeve 1100, a wedge 1200, and an anchor plate 520, and the fixing unit 202 further includes a ring nut 1300 in addition to these).

Here, the concrete fixing device (fixing section 200, fixing section 202) includes a fixing device (in the fixing section 200, a sleeve 1100, a wedge 1200, and an anchor plate 520) in the longitudinal direction of the PC steel material 300; In addition to these, there is a space for installing the hydraulic jack 700 (as well as the PC steel material for connection 810, the intermediate fixing device 900, the first bearing pressure plate 910, and the second bearing pressure plate 920) on the side where the ring nut 1300 is provided. First, a space is provided on the opposite side to install the hydraulic jack 700 (and the connecting PC steel material 810, the intermediate fixing device 900, the first bearing pressure plate 910, and the second bearing pressure plate 920).

This concrete fixing device (fixing section 200, fixing section 202) is located on the opposite side of the longitudinal direction of the PC steel material 300 (the right side in FIGS. 2, and the left side in FIGS. 6 and 7), a connecting PC steel material 810 is configured to be connectable. More specifically, as shown in FIGS. 2 and 7, the concrete fixing device (fixing section 200, fixing section 202) is located on the opposite side of the longitudinal direction of the PC steel material 300 to the surface on which the fixing device is provided (FIG. 2, and the left side in FIGS. 6 and 7), an embedded attachment portion 800 is provided in advance so that a connection PC steel material 810 can be connected thereto. This buried attachment part 800 is composed of, by way of example, a fixing nut 802, a bearing pressure plate 804, an buried tension member 806 made of PC steel, and a connection coupler 808. For example, by screwing together a male screw provided on the outer circumference of the connecting PC steel material 810 with a female screw provided on the inner circumferential surface of the connection coupler 808, the fixing device made of concrete (fixing section 200, fixing section 202) can be attached. Connection PC steel material 810 is connected.

Here, the ring nut 1300 included in the concrete fixing device (fixing unit 202) to which the tension adjustment method for prestressed steel material according to the second embodiment is applied will be described. This ring nut 1300 has, for example, an annular shape, and is a jig for correcting the set amount after primary tensioning of the PC steel material (a ring nut method is adopted as the set amount correction). In the concrete fixing device (fixing unit 200, fixing unit 202), the PC steel material 300 is a wedge divided into two or more wedge pieces when viewed from a plane perpendicular to the longitudinal direction of the PC steel material 300, or a substantially hollow cylinder. The ring nut 1300, which is included in the fixing section 202 and not included in the fixing section 200, is fixed by a sleeve having a tapered hole on its inner circumference that can be combined with a wedge. A female thread is provided on the inner periphery of the substantially annular ring nut 1300 to be screwed into the sleeve and movable in the longitudinal direction of the PC steel material 300.

Although it is not necessary to use the set amount correction jig disclosed in Patent Document 1 (Patent No. 6131292), the ring nut is indispensable for the tension adjustment method for PC steel materials according to the second embodiment. It is. Before carrying out the tension adjustment method for prestressing steel materials according to the second embodiment, the tension is adjusted using the set amount correction jig disclosed in Patent Document 1 (Japanese Patent No. 6131292). The set amount of the PC steel material to be adjusted is corrected by firstly tensioning the PC steel material and then secondly tensioning it by bringing a ring nut into contact with a bearing plate. Here, since the set amount can be corrected by the tension adjustment method of the prestressing steel material according to the second embodiment described later, the ring nut (and bearing plate) is essential, but the secondary tension is Not essential.

In this way, the jigs (sleeve 1100, wedge 1200, anchor plate with steel pipe 500, ring nut 1300) included in the concrete fixing device (fixing unit 200, fixing unit 202) described above, and the jig (fixing The nut 802, the bearing pressure plate 804, the embedded tension material 806, the connection coupler 808), the hydraulic jack 700, the connection PC steel material 810, the first bearing pressure plate 910, and the second bearing pressure plate 920 are known jigs. Here, the insertion hole for the tensioned PC steel material 300 provided in the bearing plate is a simple circular hole because it is not possible to set the bearing pressure plate from the end of the PC steel material 300 held by a fixing device or the like. For example, a known bearing plate having a U-shaped groove-shaped insertion hole is used. Further, the intermediate fixing tools 900 used in the tension adjustment method for prestressing steel material to be described later are also known jigs, and two or more (two to three A wedge 904 is divided into wedge pieces (often), and a sleeve piece 904 is approximately hollow and cylindrical and is also divided into two sleeve pieces when viewed from a plane perpendicular to the longitudinal direction of the PC steel material 300. A sleeve 902 is provided with a tapered hole on the surface to be combined with the wedge 904, and the two sleeve pieces are set together with the wedge 904 on the PC steel material 300 and then integrated with bolts.

[Tension adjustment method]
The tension adjustment method according to the present embodiment for the application example described above will be explained by adding FIGS. 3 to 5 and 8 to 10 to the above-described FIGS. 1 and 2 and FIGS. 6 and 7. In the following, the tension adjustment method according to the first embodiment will be explained using steps 11 to 16 shown in FIGS. 3 to 5, and the tension adjustment method according to the second embodiment will be explained using steps 11 to 16 shown in FIGS. 3 to 5. This will be explained in steps 21 to 26 shown in FIG. Here, the tension adjustment method according to the first embodiment is a tension adjustment method (tension release ), the tension adjustment method according to the second embodiment is a tension adjustment method when the tension of the PC steel material 300 is reduced or released using a ring nut when the PC structure is in service. (reduction including tension release).

・First embodiment: Tension adjustment (release)
<Figure 3: Step 11: Connection step>
The connection PC steel material 810 is connected to the concrete fixing device (fixing section 200). More specifically, the connection PC steel material 810 is connected to the connection coupler 808 of the burial attachment part 800 that has been buried in advance.
<Figure 3: Step 12: Preparation for installation step>
In order to attach the intermediate fixing device 900 to the PC steel material 300 in the same tension direction as the fixing device on the side where the connecting PC steel material 810 is connected in the longitudinal direction of the PC steel material 300, the location where the intermediate fixing device 900 is attached is The covering material 302 of the PC steel material 300 is removed.

<Figure 4: Step 13: Mounting step and installation step>
An intermediate fixing device 900 is attached to the PC steel material 300 from which the coating material 302 has been removed.
The insertion hole (for example, U-shape) of the PC steel material 300 and the connecting PC steel material 810 (for example, U-shape or circular shape) are A first bearing pressure plate 910 with an insertion hole, a hydraulic jack 700, an insertion hole of the PC steel material 300 (same shape as the first bearing pressure plate 910), and an insertion hole of the connecting PC steel material (same shape as the first bearing pressure plate 910). and the second bearing pressure plate 920 are prepared in this order. Here, since the PC steel material 300 is in a tensioned state with its both ends held by fixing tools etc., the insertion hole of the PC steel material 300 in this tensioned state is, for example, a U-shaped groove as described above. This is widely known in the technical field to which the present invention pertains. Then, the PC steel material 300 and the connection PC steel material 810 are respectively inserted into the insertion holes, and the intermediate fixing device 900 is opposed to one surface of the first bearing pressure plate 910, the hydraulic jack 700 is opposed to the other surface, and the second The pressure plate 920 is installed so that the hydraulic jack 700 faces one surface and the fixing member (fixing nut 930 in this case) of the connection PC steel material 810 faces the other surface. In this installation step, the piston of the hydraulic jack 700 is set to a state corresponding to the release or reduction of tension in the PC steel material 300. More specifically, the piston of the hydraulic jack 700 is extended by an amount necessary to release the tension of the PC steel material 300 on the left side in FIG. 4 . The reason why the piston of the hydraulic jack 700 is exposed in this way is that in step 16, which will be described later, when the tension force on the right side of the drawing becomes 0, the jack 700 will take over the tension force on the left side of the drawing, so the amount of elongation will correspond to that amount. Because it is necessary to return the piston, in step 13, the piston is moved out in advance by the amount of extension of the tension force shown on the left side of the drawing.

Then, the connection PC steel material 810 is connected to the hydraulic jack 700 (jack connection step), and the connection PC steel material 810 is connected to the fixing member (here, the fixing nut 930) on the opposite side of the hydraulic jack 700 on the second bearing pressure plate 920. (connected PC fixing step).
Note that the order of processing in the installation step and the order of the installation step, jack connection step, and connection PC fixing step are not particularly limited, and may be any order as long as the tension reduction step can be realized. do not have.

<Figure 4: Step 14: Tension reduction step>
Using the hydraulic jack 700, the tension in the PC steel material 300 between the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, anchor plate 520) is sufficiently reduced. At this time, the tension of the PC steel material 300 between the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, anchor plate 520) is reduced to zero. More specifically, the piston of the hydraulic jack 700 is brought out to bring the tension of the PC steel material 300 between the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, anchor plate 520) to zero.

That is, as shown in step 14 of FIG. 4, the piston of the hydraulic jack 700 is taken out and the first bearing plate 910 is moved in the direction of the black arrow to reduce the elongation of the PC steel material 300 on the right side in FIG. The tension force is reduced to bring the tension force of the PC steel material 300 within the half-wavy line region in FIG. 4 to 0 (zero).

<Figure 5: Step 15: Cutting step>
After the tension between the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, anchor plate 520) is sufficiently reduced (here, 0 (zero)), the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, and anchor plate 520).
<Figure 5: Step 16: Tension release step>
After cutting the PC steel material 300 at an arbitrary position, the tension applied by the hydraulic jack 700 is released to realize a state in which the tension of the PC steel material 300 is released. In step 16, the tension of the PC steel material 300 is released, and the amount of elongation of the PC steel material 300 on the left side of the drawing returns to the left side of the drawing. In order to cope with this, the piston of the hydraulic jack 700 is taken out in advance in step 13.
Finally, remove the connecting PC steel material 810 (remove the fixing nut 930 and remove it from the connecting coupler 808), the intermediate fixing tool 900, the first bearing plate 910, the second bearing plate 920, and the hydraulic jack 700 (removal step). .

・Second embodiment: Tension adjustment (reduction including release)
<Figure 8: Step 21: Connection step>
The connection PC steel material 810 is connected to the concrete fixing device (fixing section 200). More specifically, the connection PC steel material 810 is connected to the connection coupler 808 of the burial attachment part 800 that has been buried in advance.
<Figure 8: Step 22: Preparation for installation step>
In order to attach the intermediate fixing device 900 to the PC steel material 300 in the same tension direction as the fixing device on the side where the connecting PC steel material 810 is connected in the longitudinal direction of the PC steel material 300, the location where the intermediate fixing device 900 is attached is The covering material 302 of the PC steel material 300 is removed.

<Figure 9: Step 23: Mounting step and installation step>
An intermediate fixing device 900 is attached to the PC steel material 300 from which the coating material 302 has been removed.
The insertion hole (for example, U-shape) of the PC steel material 300 and the connecting PC steel material 810 (for example, U-shape or circular shape) are A first bearing pressure plate 910 with an insertion hole, a hydraulic jack 700, an insertion hole of the PC steel material 300 (same shape as the first bearing pressure plate 910), and an insertion hole of the connecting PC steel material (same shape as the first bearing pressure plate 910). and the second bearing pressure plate 920 are prepared in this order. Then, the PC steel material 300 and the connection PC steel material 810 are respectively inserted into the insertion holes, and the intermediate fixing device 900 is opposed to one surface of the first bearing pressure plate 910, the hydraulic jack 700 is opposed to the other surface, and the second The pressure plate 920 is installed so that the hydraulic jack 700 faces one surface and the fixing member (fixing nut 930 in this case) of the connection PC steel material 810 faces the other surface. In this installation step, the piston of the hydraulic jack 700 is set to a state corresponding to the release or reduction of tension in the PC steel material 300. More specifically, the piston of the hydraulic jack 700 is located on the left side of the drawing in the same manner as in step 13 in the first embodiment described above (as in step 16 in the first embodiment to which step 26 in this embodiment corresponds). (In order for the amount of elongation of the PC steel material 300 to return to the left side in the drawing), the amount necessary to release the tension of the PC steel material 300 on the left side in FIG. 9 is extended in advance.

Then, the connection PC steel material 810 is connected to the hydraulic jack 700 (jack connection step), and the connection PC steel material 810 is connected to the fixing member (here, the fixing nut 930) on the opposite side of the hydraulic jack 700 on the second bearing pressure plate 920. (connected PC fixing step).
Note that the order of processing in the installation step and the order of the installation step, jack connection step, and connection PC fixing step are not particularly limited, and may be any order as long as the tension reduction step can be realized. do not have.

<Figure 9: Step 24: Tension reduction step>
Using the hydraulic jack 700, the tension in the PC steel material 300 between the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, anchor plate 520) is sufficiently reduced. At this time, the tension of the PC steel material 300 between the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, anchor plate 520) is reduced to a state where the ring nut 1300 can rotate. More specifically, the piston of the hydraulic jack 700 is taken out to reduce the tension of the PC steel material 300 between the intermediate fixing device 900 and the fixing device (sleeve 1100, wedge 1200, anchor plate 520) to zero, and the ring nut 1300 is removed. is raised slightly above the bearing pressure plate 520 so that it can be rotated.

That is, as shown in step 24 of FIG. 9, the piston of the hydraulic jack 700 is taken out and the first bearing plate 910 is moved in the direction of the black arrow to reduce the elongation of the PC steel material 300 on the right side in FIG. The tension force is reduced to bring the tension force of the PC steel material 300 within the half-wavy line region in FIG. 9 to 0 (zero). By doing so, the ring nut 1300 floats slightly (even) from the bearing pressure plate 520, and the ring nut 1300 can be rotated.

<Figure 10: Step 25: Ring loosening step>
The ring nut 1300, which has become slightly floating and rotatable from the bearing pressure plate 520, is loosened so that the tension of the PC steel material 300 is reduced to a predetermined tension. More specifically, as shown in Step 25 of FIG. 10, the ring nut 1300 is moved in the direction of the black arrow according to the amount necessary for adjusting the tension of the PC steel material 1300. Here, when realizing a state in which the tension force of the PC steel material 300 is 0 (when the tension force is completely released), the ring nut 1300 may be loosened and removed in this ring loosening step.
<Figure 10: Step 26: Tension release step>
After rotating the ring nut 1300 and moving the ring nut 1300 in the direction of the black arrow according to the amount required to adjust the tension of the PC steel material 1300, the tension force by the hydraulic jack 700 is released and the tension force of the PC steel material 1300 is released. A state in which the tension force of 300 is reduced (including release) is realized.
Finally, remove the connecting PC steel material 810 (remove the fixing nut 930 and remove it from the connecting coupler 808), the intermediate fixing tool 900, the first bearing plate 910, the second bearing plate 920, and the hydraulic jack 700 (removal step). .

[Effects of tension adjustment method]
In this way, according to the tension adjustment method according to the present embodiment, the work space ( It is possible to provide an adjustment method that can adjust the tension applied to the PC steel (including releasing it to zero and reducing it) even if the work space is small.

It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

The present invention is preferable for a method of adjusting the tension force that occurs when prestressing is applied to the prestressed steel material, and even if the work space (work space) is small, the tension force applied to the prestressed steel material can be reduced to (0 (zero)). Particular preference is given to adjustment methods that can be adjusted (including opening and reducing).

100 Prestressed PC bridge (prestressed PC structure)
200, 202 Fixing section (concrete fixing device)
300 PC steel material (tension material, outer cable)
400 Deflection part 500 Anchor plate with steel pipe 510 Steel pipe 520 Anchor plate (bearing pressure plate)
700 Hydraulic jack 800 Buried attachment part 900 Intermediate fixing tool 1100 Sleeve 1200 Wedge 1300 Ring nut

Claims (6)

A tension adjustment method for adjusting the tension of a PC steel material applying compressive force to a prestressed PC structure, the method comprising:
The end of the PC steel material is fixed by a fixing tool provided in a concrete fixing device having a substantially rectangular parallelepiped shape, and the concrete fixing device is attached to a surface opposite to the surface on which the fixing tool is provided in the longitudinal direction of the PC steel material. The PC steel material for connection is configured to be connectable,
a connecting step of connecting the connecting PC steel material to the concrete fixing device;
an attachment step of attaching an intermediate fixing device to the PC steel material so that the tension direction is the same as that of the fixing device on the side where the connecting PC steel material is connected in the longitudinal direction of the PC steel material;
A first bearing pressure plate having an insertion hole for the PC steel material and an insertion hole for the connecting PC steel material in a direction away from the concrete fixing device side in the longitudinal direction of the PC steel material, a hydraulic jack, and an insertion hole for the PC steel material. and a second bearing pressure plate having an insertion hole for the connection PC steel material are prepared in this order, and the PC steel material and the connection PC steel material are respectively inserted into the insertion hole, and one of the first bearing pressure plates is inserted. The intermediate fixing device faces one side, the hydraulic jack faces the other side, the hydraulic jack faces one side of the second bearing pressure plate, and the connecting PC steel fixing member faces the other side. an installation step for installing the
a jack connecting step of connecting the connecting PC steel material to the hydraulic jack;
a connection PC fixing step of fixing the connection PC steel material with a fixing member on the opposite side of the hydraulic jack on the second bearing pressure plate;
a tension reducing step of sufficiently reducing the tension of the PC steel material between the intermediate fixing device and the fixing device using the hydraulic jack;
a cutting step of cutting the PC steel material at an arbitrary position between the intermediate fixing device and the fixing device after the tension between the intermediate fixing device and the fixing device is sufficiently reduced;
a tension release step of releasing the tension from the hydraulic jack to achieve a state in which the tension of the prestressing steel material is released;
A tension adjustment method including a removing step of removing the connecting PC steel material, the intermediate fixing device, the first bearing pressure plate, the second bearing pressure plate, and the hydraulic jack. 2. The tension adjustment method according to claim 1, wherein the tension reducing step reduces the tension of the PC steel material between the intermediate fixing device and the fixing device to zero. A tension adjustment method for adjusting the tension of a PC steel material applying compressive force to a prestressed PC structure, the method comprising:
The end of the PC steel material is fixed by a fixing tool provided in a concrete fixing device having a substantially rectangular parallelepiped shape, and the concrete fixing device is attached to a surface opposite to the surface on which the fixing tool is provided in the longitudinal direction of the PC steel material. A PC steel material for connection is configured to be connectable, the fixing device includes a ring nut, and the tension of the PC steel material is maintained by the ring nut,
a connecting step of connecting the connecting PC steel material to the concrete fixing device;
an attachment step of attaching an intermediate fixing device to the PC steel material so that the tension direction is the same as that of the fixing device on the side where the connecting PC steel material is connected in the longitudinal direction of the PC steel material;
A first bearing pressure plate having an insertion hole for the PC steel material and an insertion hole for the connecting PC steel material in a direction away from the concrete fixing device side in the longitudinal direction of the PC steel material, a hydraulic jack, and an insertion hole for the PC steel material. and a second bearing pressure plate having an insertion hole for the connection PC steel material are prepared in this order, and the PC steel material and the connection PC steel material are respectively inserted into the insertion hole, and one of the first bearing pressure plates is inserted. The intermediate fixing device faces one side, the hydraulic jack faces the other side, the hydraulic jack faces one side of the second bearing pressure plate, and the connecting PC steel fixing member faces the other side. an installation step for installing the
a jack connecting step of connecting the connecting PC steel material to the hydraulic jack;
a connection PC fixing step of fixing the connection PC steel material with a fixing member on the opposite side of the hydraulic jack on the second bearing pressure plate;
a tension reducing step of using the hydraulic jack to reduce the tension of the PC steel material between the intermediate fixing device and the fixing device to a state where the ring nut can rotate;
a ring loosening step of loosening the ring nut such that the tension of the prestressing steel material is reduced to a predetermined tension;
a tension force reducing step of releasing the tension force by the hydraulic jack to realize a state in which the tension force of the prestressing steel material is reduced;
A tension adjustment method including a removing step of removing the connecting PC steel material, the intermediate fixing device, the first bearing pressure plate, the second bearing pressure plate, and the hydraulic jack. 4. The tension adjustment method according to claim 3, wherein when achieving a state in which the tension of the PC steel material is 0 in the tension reduction step, the ring nut is loosened and removed in the ring loosening step. The tension adjustment method according to any one of claims 1 to 4, wherein in the installation step, the hydraulic jack whose piston is set in a state corresponding to release or reduction of the tension of the prestressing steel material is installed. . The concrete fixing device does not have a space for installing the hydraulic jack on the side where the fixing tool is provided in the longitudinal direction of the PC steel material, but has a space for installing the hydraulic jack on the opposite side. The tension adjustment method according to any one of claims 1 to 5.

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