JP3762717B2 - PC steel fixed structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a PC steel material fixing structure and fixing method, and a PC cable used in the fixing structure. In particular, it improves the workability of fixed fixing parts of PC steel strands used for cables used for prestressed concrete members, cable-stayed bridge suspension materials, outer cables, etc., and without making a fixing tool of complicated shape The present invention relates to a fixing structure capable of improving fatigue performance.
[0002]
[Prior art]
Conventionally, fixing devices for strands of PC steel are roughly classified into a fixing device using a wedge and a fixing device using a crimping grip.
[0003]
As shown in FIG. 5, the fixing device using a wedge includes a combination of a wedge 20 (wedge) and an anchor disk 50 or a female cone 55 having a tapered hole 51. The wedge 20 is generally formed into a truncated cone shape having a large diameter at one end and a small diameter at the other end by combining two or three divided pieces. In the state where the divided pieces are combined, a circular hole extending in the axial direction is formed at the center of the wedge 20. In this circular hole, the PC steel wire 10 is held by the wedge 20. The PC steel strand 10 whose end is gripped by the wedge 20 is given a predetermined tension with a jack, and is fixed by fitting the wedge 20 into the taper hole 51 of the anchor disk 50 or the female cone 55. The anchor disk 50 is disposed on an anchor plate 60 located on the surface of the concrete structure.
[0004]
On the other hand, as shown in FIG. 6, the fixing tool using the crimping grip is composed of a combination of a cylindrical crimping grip 70 and an anchor plate 60. The crimp grip 70 is usually a steel sleeve having an inner diameter slightly larger than the outer diameter of the wire 10 than the bare PC steel, and the metal 40 is interposed between the PC steel wire 10 and the sleeve 70 as shown in FIG. While being interposed, it passes through a die 80 having a diameter slightly smaller than the outer diameter of the sleeve 70 by extrusion, and is strongly pressed against the wire 10 from the PC steel. On the other hand, the anchor plate 60 is a metal plate having a through hole through which the PC steel wire 10 passes but the crimping grip 70 does not pass. When the PC steel strand 10 is passed through the through hole and the PC steel strand is tensioned, the crimp grip 70 is pressed against the anchor plate 60, whereby the end of the PC steel strand 10 is fixed.
[0005]
Recently, with the increase in size of prestressed concrete structures, the PC cables used are increasing in capacity and length. Along with this, conventionally, PC steel strands were inserted one by one into the sheath of the structure, but multiple PC steel strands were bundled together at the factory to improve workability. There are many ways to make a cable and pull it into the sheath at once. At this time, the PC steel strand is fixed using the wedge or the crimping grip.
[0006]
[Problems to be solved by the invention]
However, in either case, there were problems as described below.
<In case of wedge>
The wedge for fixing the strand of PC steel when tensioned is arranged in the tapered hole of the anchor disk, but since the wedge is made up of 2 to 3 divided pieces, one piece of each piece is placed in the tapered hole. The wedge is arranged so that the heads (thick side) are aligned, and the hollow cylinder is struck into the tapered hole so as not to fall.
[0007]
(1) However, the arrangement of the wedges is restricted by the arrangement of a large number of tapered holes 51 provided in the disk-shaped anchor disk 50 as shown in FIG. Therefore, it is relatively easy to place a wedge on the PC steel strand on the outer part of the cable, but it is very difficult to work on the PC steel strand on the inner part of the cable because the outer PC steel wire becomes an obstacle. There are cases where accurate placement is not possible.
[0008]
(2) When a jack is attached to the tension side PC steel wire to be tensioned after the wedge is arranged, the PC steel wire may be pressed when passing through the tension hole of the jack. In that case, with the fixed fixture on the opposite side, the arranged wedge may jump out together with the PC steel wire, and if tensioned as it is, the head of the wedge split piece will shift in the axial direction and cause a step difference, affecting the fixing performance. May give.
[0009]
(3) If the inner surface of the taper hole in the anchor disk is rusted, the friction with the outside of the wedge will increase and the sliding will be poor, and the wedge will have less force to grip the wire than PC steel, and the wire will be more tensioned than PC steel. Sometimes it slips.
[0010]
(4) For cables that require high fatigue characteristics, such as cable-stayed bridges, in order to align the length between the fixed side fixing tool and the tension side fixing tool of the PC steel strand that constitutes the cable as much as possible as well as the fixing tool. Length management may be performed when laying PC steel strands. In other words, when there are many cables and they become longer, the length between individual wires will vary from PC steel, and if tension is applied at once, the tension between individual PC steels will vary and the fatigue characteristics will deteriorate. is there. In this case, after marking the both ends of the PC steel wire and aligning the fixed side fixing tool, the tension side is first tensioned with a jack from the PC steel to the specified mark one by one. Once you have all the lengths in place, strain with a large jack. However, in the case of a wedge, when the wire is moved from the PC steel, the axial direction is likely to be displaced, and it may be difficult to accurately match the mark on the fixed side.
[0011]
<In case of crimp grip>
On the other hand, in the case of a crimping grip, a sleeve is crimped at the end of the strand of PC steel at the factory, and this is used as a cable and then inserted into the structure sheath as it is. For this reason, at least the fixed side does not need to perform an operation of arranging the wedges one by one on the site. Also, when the jack is installed on the tension side, the PC steel wire is pressed, and even if the wedge is tensioned after jumping out of the taper hole on the fixed side, the wedge head does not become uneven and secure fixing Can do. Furthermore, if it is a crimping grip, it can be crimped according to a predetermined mark, and even if the wire is moved from PC steel, the crimping grip does not deviate from the position marked by the wire from PC steel. In particular, when the cable is placed diagonally, such as a cable stayed cable or an extra-dust bridge cable, if the lower fixing part is used as a crimping grip, it is fixed to the PC steel wire, so it will fall off during operation. There is no.
[0012]
(1) However, in the case of a crimping grip, the tension is maintained by the crimping force against the wire from the PC steel, so if a repeated stress is applied after tension, the wire will come out of the PC steel from the outlet side of the sleeve. And As a result, relative movement is likely to occur between the inner surface of the crimping grip and the PC steel wire, so that a so-called fretting phenomenon is likely to occur. For this reason, the crimp grip can be used as a fixing device having sufficient fatigue characteristics in the case of ordinary post-tension structures, etc., but for cables that require fatigue characteristics such as cable-stayed bridges or extradost bridges. Not suitable as a fixing tool.
[0013]
(2) In order to improve the fatigue characteristics of the fixing tool due to the crimping grip, Japanese Patent Publication No. 7-21163 and Japanese Patent Application Laid-Open No. 2001-107507 disclose that the load is transmitted to the crimping grip and the initial tip is fatigued by various measures. A technique for improving the characteristics has been devised. Japanese Examined Patent Publication No. 7-21163 discloses a technology for improving the fatigue characteristics by making the tip of the cylindrical sleeve a tapered truncated cone with a split groove and reducing the relative movement of the wire from the PC steel of the tip of the cylindrical sleeve as much as possible. Disclosure. Japanese Patent Laid-Open No. 2001-107507 discloses a technique in which an inner surface of a crimping grip is filled with a cushioning material such as an epoxy resin so that a load is first transmitted to the resin and then transmitted to the crimping grip. As a result, the relative movement of the wire from the PC steel is caused in the cushioning material, the fretting phenomenon is reduced, and the fatigue characteristics are improved. However, each technique has a problem that the fixing tool becomes large, the shape becomes complicated, and the cost increases.
[0014]
(3) The crimping grip is designed to withstand high loads while the crimping process of the sleeve is quite strong, and the sleeve may be damaged when it is tensioned.
[0015]
Accordingly, a main object of the present invention is to provide a PC steel fixing structure and fixing method, and a PC cable, which can maintain a high fatigue characteristic without complicating the shape of a fixing portion and can accurately arrange a wedge. It is in.
[0016]
[Means for Solving the Problems]
The present invention achieves the above object by using a wedge and providing a fixture that suppresses the displacement of the wedge.
[0017]
That is, the PC steel material fixing structure of the present invention includes a wedge attached to the outer periphery of the fixed-side PC steel material, a wedge receiver having a fitting hole into which the wedge is fitted, and a rear end side of the wedge. The fixing tool is fixed to the PC steel with a gripping force sufficient to abut against each divided piece and restrict the movement of the divided piece in the axial direction of the PC steel. It is characterized by being.
[0018]
Further, the PC cable of the present invention includes a wedge attached to an end portion of the PC steel material, and a fixture that is fixed to the outer periphery of the PC steel material on the back side of the wedge and suppresses the movement of the wedge in the axial direction. It is characterized by.
[0019]
Further, the PC steel material fixing method of the present invention is a PC steel material fixing method in which a wedge made of a plurality of divided pieces is attached to an end of a PC steel material, and the wedge is fitted into a wedge receiver and fixed. A fixing tool is attached to the outer periphery of the PC steel material on the back side, and the movement of each divided piece in the axial direction is suppressed by the fixing tool to fit the wedge into the wedge receiver.
[0020]
By using a wedge as the fixing tool, (1) slippage between the crimping grip and PC steel due to insufficient load bearing capacity during tension due to the inadequate crimping process, and (2) complexity of the crimping grip shape to improve fatigue characteristics It is possible to eliminate the disadvantages of the crimp grip such as. Also, by using a fixture that is fixed to the PC steel, when the PC steel is drawn into the sheath, the wedge is placed in the tapered hole in such a way that the wedge is pushed by the fixture provided on the fixed side. There is no deviation and it is accurately placed in the tapered hole. Therefore, (1) the complexity of placing a wedge near the center of a large-capacity cable composed of a large number of PC steel strands, and (2) after the wedge jumps out of the taper hole on the fixed side when the jack is placed, Eliminates the disadvantages of wedges such as uneven head placement, (3) variation in wedge position with respect to PC steel wire mark, and (4) slipping of PC steel wire due to reduced gripping force due to rust in the taper hole it can.
[0021]
The wedge used here may be the same as that conventionally used. Therefore, it is not necessary to process the wedge into a special shape. For example, a truncated cone shape in which a gripping hole for a PC steel material is formed in the axial direction by combining two to three pieces. Usually, a groove is formed on the outer periphery of each divided piece, and the divided pieces are prevented from being separated by fitting an O-ring or the like into the groove.
[0022]
The wedge receiver may be any one as long as it has a tapered hole into which the wedge is fitted and maintains the tension of the PC steel material. For example, a cylindrical female cone having a tapered hole or a plate-shaped anchor disk in which a plurality of tapered holes are formed may be mentioned.
[0023]
The fixture is preferably ring-shaped or cylindrical. The means for fixing the fixture to the PC steel material is not particularly limited. For example, the fixing tool may be a steel sleeve and may be crimped to the outer periphery of the stationary PC steel material. Further, the fixing tool may be a steel ring, and the ring may be fixed to the PC steel material by tightening with a screw penetrating in the radial direction.
[0024]
The fixing degree of the fixture does not need to be so strong that the tension of the PC steel material is maintained as in the case of the crimping grip. In other words, when the PC steel material is pulled into the sheath and the wedge of the fixed fixing tool enters the taper hole, the gripper can hold the wedge from behind to restrict the movement of each divided piece in the axial direction. Power is enough. Therefore, the fixture may be much shorter than the conventional crimp grip and can be fixed with a small degree of processing. This sticking can be easily processed at the construction site.
[0025]
The material of the fixture may be a material having a strength that can withstand the above-described degree of fixation. For example, metals such as steel and plastics such as polyethylene, polypropylene, and polyamide can be used.
[0026]
The mounting position of the fixing tool is the rear side of the wedge, that is, the side where the wedge diameter is large. In particular, when the wedge is mounted at the mark position of the PC steel material, it is preferable to mount the fixing tool so that the fixing tool just contacts the large-diameter side end surface of the wedge.
[0027]
The fixture and the wedge may be attached integrally. Thereby, the shift | offset | difference to the axial direction of each division | segmentation piece and the shift | offset | difference of the mounting position with respect to PC steel materials of a wedge can be suppressed more reliably.
[0028]
The fixing means and the wedge are preferably attached by screws. For example, it is possible to use an annular fixture and integrate the divided pieces with screws that penetrate the fixture in the axial direction.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
Example 1
This section describes a cable that bundles 27 strands of PC steel with a diameter of 15.2 mm specified in JIS G 3156. FIG. 1 is a configuration diagram of a PC cable of the present invention equipped with a fixture.
[0030]
At the end of this PC steel strand 10, a 15.2 mm wedge used in the past is attached. The PC steel stranded wire 10 is formed by twisting six side wires around one central line. The wedge 20 has a truncated cone shape in which a gripping hole of the PC steel strand 10 is formed by combining three divided pieces 21. On the inner surface of the gripping hole of the wedge, female threads 22 are formed at a predetermined pitch so that the wire is securely gripped from the PC steel.
[0031]
Next, after passing through a sleeve 30 (fixing tool) made of steel and having an outer diameter of φ31mm and an inner diameter of φ15.5mm through a predetermined position at the end of the PC steel strand 10, it is crimped by a crimping machine having a die diameter of φ30mm. Process and fasten the sleeve to the PC steel strand. This crimping is performed with a metal 40 interposed between the sleeve 30 and the PC steel strand 10 as shown in FIG. The length of the sleeve 30 is 25 mm, and the processing degree is about 6%. Further, the sleeve 30 is fixed to the large diameter side of the wedge 20.
[0032]
Thereafter, the wedge 20 arranged in advance is moved to a position close to the sleeve 30. Transport this cable to the construction site and place it near the structure where the cable is to be inserted. Here, similarly to the fixing tool shown in FIG. 5 (A), the wedges 20 are fitted into the tapered holes 51 of the anchor disk 50 to fix the PC steel wires 10. As shown in FIG. 8, the anchor disk 50 is a metal disk having 27 tapered holes 51 into which the wedges 20 are fitted.
[0033]
After processing the end of the PC steel strand 10 so that the cable end can be fixed to the pulling tool, insert the PC steel strand 10 into the taper hole of the fixed anchor disk and hold the cable end with the winch Then pull it into the structure. After the end of the cable comes out from the tension side of the structure, the pull-in is completed when the wedge 20 is received in the tapered hole 51 of the fixed anchor disk.
[0034]
At the time of this pulling, the sleeve 30 crimped to the PC steel wire 10 comes into contact with the large-diameter end surface of the wedge 20 and presses each divided piece 21 in the axial direction, so that the displacement of each divided piece 21 in the axial direction is shifted. Prevent it from happening. At the same time, the wedge 20 can be reliably pushed into each tapered hole 51 of the anchor disk 50.
[0035]
This saves you the trouble of attaching wedges to the appropriate position of each strand of PC steel. In particular, the axial displacement of each of the divided 21 pieces can be reliably suppressed with respect to the PC steel strand located on the center side of the anchor disk 50. Also, when the jack is attached to the PC steel strand 10 on the tension side, even if the wedge 20 on the fixed side comes out of the taper hole 51, the sleeve 30 is rearranged by pressing each divided piece 21 during tension, The difference in the head of the wedge 20 can be eliminated.
[0036]
(Example 2)
In the first embodiment, the sleeve 30 is crimped and fixed to the PC steel wire, but the PC steel may be fixed to the wire by screwing instead of crimping. FIG. 2 shows a configuration diagram of the PC cable of the present invention equipped with a screw-type fixing device, and FIG. 3 shows a plan view of the screw-type fixing device.
[0037]
This fixture is a metal ring 35 having an outer diameter substantially equal to the large diameter side of the wedge 20. Three screw holes 36 penetrating in the radial direction are formed at equal intervals. Further, in this example, in order to integrate the ring 35 and the wedge 20, three screw holes 37 penetrating in the axial direction are formed at equal intervals. The screw holes 36 penetrating in the radial direction and the shaft holes 37 penetrating in the axial direction are alternately arranged.
[0038]
The fixing tool is attached to the PC steel strand 10 by screwing a bolt into a screw hole 36 penetrating in the radial direction and tightening. Further, a bolt is screwed into the screw hole 37 penetrating in the axial direction so as to be integrated with each divided piece 21 constituting the wedge 20. A screw hole into which the screw is screwed may be formed on the end face on the large diameter side of the divided piece.
[0039]
Even with this fixture, the wedges can be attached to the appropriate positions of the PC steel stranded wires by aligning the axial positions of the divided pieces as in the first embodiment.
[0040]
(Test example)
A fatigue test of the fixing structure shown in Example 1 was performed. Here, as a wedge used for a structure requiring high fatigue resistance, a wedge in which the pitch of teeth (internal threads) on the inner surface is made smaller than that of a conventional wedge to reduce the load applied to the teeth is used. The pitch of this internal thread is 0.5 mm. In addition, the taper angle of the anchor disk and the taper angle of the wedge are the same. The taper angle is tan α = 1/10 of the angle α formed by the outer periphery of the wedge and the axial horizontal line, and the wedge length is 45 mm. And the diameter of each PC steel strand is 15.2mm. For comparison, a fatigue test using a conventional crimp grip and a fatigue test using a fixing structure using only a wedge without using a fixture were also performed.
[0041]
In the fatigue test, a repeated amplitude stress was applied to the wire from PC steel with an upper limit load of 119.7 kN and the same wave number of 4 Hz, and the number of repetitions until breaking occurred. These results are shown in the graph of FIG. As is clear from FIG. 4, the fixing structure of the example was able to obtain the same level of results as the fatigue characteristics when the same wedge was used alone without using a fixture.
[0042]
【The invention's effect】
As described above, according to the PC steel material fixing structure and fixing method of the present invention, the wedge is inserted and arranged in advance on the PC steel fixing side, and the wedge is prevented from moving on the large diameter side of the wedge. The following effects can be achieved by attaching the fixture to the PC steel.
[0043]
Since the wedge is arranged in the tapered hole in such a manner that it is pushed by the fixing tool, it can be accurately arranged in the tapered hole without any deviation. In particular, the wedge can be attached to a predetermined position on the PC steel without deviation.
[0044]
Of the many PC steel materials, the wedges can be securely fitted into the tapered holes even for PC steel materials arranged near the center.
[0045]
Since the fixture does not need to maintain the tension of PC steel, it is not necessary to perform strong crimping and can be crimped on site.
[0046]
Since fixing is performed using a wedge, it is possible to eliminate the disadvantages of the crimping grip, such as slippage between the crimping grip and PC steel due to poor crimping, and complicated crimping grip shapes to improve fatigue characteristics.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a cable of the present invention in which a fixture is crimped.
FIG. 2 is a configuration diagram of a cable of the present invention in which a fixing tool is screwed.
3 is a plan view of the fixture of FIG. 2. FIG.
FIG. 4 is a graph showing fatigue test results.
5A is an explanatory diagram of a fixing structure using an anchor disk and a wedge, and FIG. 5B is an explanatory diagram of a fixing structure using a female cone and a wedge.
6A is an explanatory diagram of a structure in which a single strand of PC steel is fixed with a crimping grip, and FIG. 6B is an explanatory diagram of a structure in which a plurality of PC steel strands are fixed with a crimping grip.
FIG. 7 is an explanatory diagram when a crimping grip is crimped to a PC steel wire with a die.
8A is a plan view of an anchor disk, and FIG. 8B is a longitudinal sectional view thereof.
[Explanation of symbols]
10 PC steel stranded wire
20 wedges
21 pieces
22 Female thread
30 sleeves
35 rings
36 Screw hole
37 Screw hole
40 metal
50 Anchor disc
51 Taper hole
55 female cone
60 Anchor plate
70 Sleeve (crimp grip)
80 dice

Claims (5)

Consists of a plurality of divided pieces, and a wedge attached to the outer periphery of the fixed-side PC steel material,
A wedge receiver having a fitting hole into which the wedge is fitted;
On the rear end side of the wedge, comprising a fixture fixed to the outer periphery of the PC steel material,
This fixing tool is fixed to the PC steel material with a gripping force that is attached to the wedge and that abuts on each of the divided pieces and can regulate the movement of the divided pieces in the axial direction of the PC steel material. PC steel fixed structure characterized by that. The fixing structure for a PC steel material according to claim 1 , wherein the fixing tool and the wedge are attached by tightening screws.   2. The PC steel material fixing structure according to claim 1, wherein the fixing tool is made of a steel sleeve and is crimped to the outer periphery of the fixed side PC steel material.   2. The PC steel material fixing structure according to claim 1, wherein the fixing tool is a steel ring, and the ring is fixed to the PC steel material by tightening with a screw penetrating in a radial direction. PC steel, a wedge attached to the end of the PC steel, and a fixture that is fixed to the outer periphery of the PC steel on the back side of the wedge to suppress the movement of the wedge in the axial direction ,
The fixture, with attached wedge integrally, in contact with the respective segments, split piece that is fixed to the PC steel member in the gripping force enough to regulate that movement in the axial direction of the PC steel PC cable characterized by that.

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