JP5405889B2 - Tension material tensioning method - Google Patents

Description

  The present invention relates to a tension material tensioning method used for introducing prestress into a structure or for supporting the structure.

Tensile material for introducing prestress into a concrete structure is not only inserted through a sheath embedded in a concrete member, but also is fixed by inserting both ends into through holes provided in the structure. Some of them are stretched outside the concrete member. The tension material stretched outside the concrete member is disposed, for example, inside a bridge girder having a box-shaped cross section, and both ends are fixed to a fixing block provided for fixing the cross beam or the tension material. That is, a through hole is provided in the cross beam or the fixing block, and a tension material is inserted into the through hole to fix the cross beam or the fixing block so that a reaction force acts on the cross beam or the fixing block.
On the other hand, the diagonal suspension material used for the cable-stayed bridge is also fixed by inserting both end portions into through holes provided in the main tower and the bridge girder.

  As such a tendon, a material in which wires are bundled from a plurality of steels is often used. When the tension member is stretched at a predetermined position, a plurality of steel strands are bundled in advance, and a grip is attached to one end to connect the wire. The wire is pulled by a winch or the like, and a bundle of wires is bundled and inserted into a through hole provided in the structure. A plurality of steel strands inserted through the through holes are locked to a multi-strand jack, and a tension force is introduced into the plurality of steel strands collectively. Then, it is fixed to the structure using a wedge or the like in a state where the tension is introduced.

  However, since the height of the bridge girder becomes small in a cable stayed bridge or the like, a case where a multi-strand jack having a large size cannot be used at the time of introducing a tension force occurs. In other words, the space inside the bridge girder is narrow, and there is a case where the jack cannot be attached to the fixing portion of the tension material. In such a case, as described in Non-Patent Document 1, a plurality of steel strands constituting the tension material are sequentially tensioned one by one using a small single-strand jack.

Yoshio Iizuka, Hirofumi Ando, Kazuhiro Utsuki, Yoshiyuki Wakabayashi, “Construction of PC Reverse Langer Arch Bridge Ikedako Bridge (tentative name)”, Prestressed Concrete Technology Association 8th Symposium Proceedings, October 1998

As described above, when a tension force is introduced into a tension material in which a plurality of steel strands are bundled, if the tension force is sequentially introduced to each strand of steel, the following problems arise.
If tension materials that bundle a plurality of steel strands are collectively inserted into the through hole, the plurality of steel strands may be twisted or entangled in the through hole. In particular, when a through hole is provided in a curved shape in a structure such as a cross beam and is deflected, twisting or the like is likely to occur. Then, when the tension force is introduced one by one in a state where the strands of the plurality of steel strands are twisted with each other, the steel strand that has introduced the tension force first presses the wire from the non-tensile steel, and the steel that is tensioned later There are cases where a predetermined tension cannot be introduced into the line.

On the other hand, it is conceivable that a plurality of tendons are not inserted through the through-holes at once, but it is also possible to insert steel strands one by one through the through-holes. It may be difficult to insert wires from steel. In particular, when a part of the through hole is provided in a curved shape, the insertion is likely to be difficult. This is because the steel strand that has been inserted is less likely to move in the through hole, and it is difficult to adjust the space in the through hole, making it difficult to insert the wire from the last one or two steels. Conceivable.
Further, if the wires are inserted one by one, the steel strands inserted later will penetrate between the steel wires inserted earlier, and as a result, the steel wires will twist each other.

  This invention is made | formed in view of such a situation, The objective is to insert smoothly the tension material which bundled the wire from several steel in the through-hole provided in the structure of the fixing | fixed part. It is also possible to provide a tension material stretching method that can easily introduce a predetermined tension force to all the steel strands even if the tension force is sequentially introduced one by one.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that the vicinity of the ends of the tension members bundled with a plurality of steel strands are respectively inserted into through holes provided in the structure, and the tension force is applied to the tension members. Is a tension material tensioning method in which both ends are fixed by applying a reaction force to the structure in a state in which is introduced, the step of inserting the vicinity of at least one end of the tension material into the through-hole, Prepare a wire rod having a diameter approximately the same as that of the steel strand and long enough to hold both ends from the through-hole, and adjoin the same number of wires as the number of wires from the steel of the tension material Bundling in a state where the wires are in contact with each other to form a dummy tendon, inserting the dummy tendon into the through hole of the structure, and configuring one end of one wire constituting the dummy tendon as the tendon Connected to one steel strand, and the other of the wires connected to the steel strand Gripping the part and pulling it out from the through hole, pulling the wire from the steel instead of the wire into the through hole, connecting the wire to the steel wire, and pulling the wire and pulling the wire from the steel into the through hole There is provided a tension material tensioning method in which the step of drawing in is sequentially performed on the other steel strands of the tension material.

  In this method, since the dummy tendon is cut to a degree slightly longer than the through hole, even if they are bundled and inserted through the through hole at once, the rear part of the dummy tendon is less likely to be restrained, There is little twist in the wire. Then, when the steel strand is connected to the wire constituting the dummy tendon and the wire is pulled, the steel strand having the same diameter as that of the wire is smoothly drawn into the through hole, and the wire or steel strand is surrounded around the wire. Even if it exists, a wire is easily replaced with a strand from steel. Then, if the wires constituting the dummy tension members are replaced with steel strands in sequence, the plurality of steel strands are inserted into the through-holes with less twist and smoothly even if tension is introduced one by one. A predetermined tension can be introduced into all steel strands.

  In addition, it is possible to use a wire rod having a diameter approximately equal to that of a wire than steel, and it is desirable that the wire has a diameter slightly larger than that of the wire. Can be used. When the diameter of the wire is smaller than the diameter of the wire than the steel, and the difference is large, the resistance increases when the wire is connected to the steel wire and the wire is drawn into the through hole. Therefore, when using a wire having a diameter smaller than that of the wire, the diameter of the wire is set so that the wire can be drawn into the through hole from the connected steel. Moreover, when the diameter of a wire is larger than the diameter of a wire than steel, it is set as the extent which can insert all the wires into a through-hole, and can draw out one by one.

  The invention according to claim 2 is the tensioning method of the tension material according to claim 1, wherein all the wires of the dummy tension material are pulled out from the through holes, and all of the steel wires constituting the tension material are penetrated. It is assumed that tension force is sequentially introduced one by one after being inserted into the hole, and is sequentially fixed to the structure.

  In this method, the wire of the dummy tendon can be replaced with a steel strand in a state where no tension is introduced into all the tendons. Thereby, it becomes possible to perform efficiently the operation | work which penetrates a steel strand to a through-hole.

  The invention according to claim 3 is the method of tensioning the tension member according to claim 1 or 2, wherein the tension member is formed by pulling out one wire of the dummy tension member from the through hole. After one of the wires is inserted into the through hole, a tension force is introduced into the steel wire and fixed. After that, for all the steel wires, the steel wire is drawn into the through hole to introduce and fix the tension force. The steps to be performed are repeated sequentially.

  In this method, when a tension force is introduced into the stranded wire, the wire in the through hole is cut short, so that the position in the through hole is less likely to be restrained, and the tension of the stranded wire in the surrounding steel is less. The position is adjusted as the force is introduced. As a result, the wire rod can be easily replaced with a stranded wire, and a predetermined tension force can be reliably introduced into the stranded wire drawn into the through hole.

  The invention according to claim 4 is the tension material tensioning method according to claim 1, claim 2 or claim 3, in which the core wire arranged at the center and the outer periphery twisted around the core as the steel strand The step of connecting the wire and the steel stranded wire is performed by cutting the outer peripheral line at an end portion of the steel stranded wire, and connecting the exposed core wire to the wire. It shall join and the said connection tool shall use the outer diameter smaller than the outer diameter of the said wire.

  In this method, a core wire can be used to easily and firmly connect a steel strand to a connector. Since the outer diameter of the connecting tool is smaller than the outer diameter of the wire rod, the connecting tool is less likely to become an obstacle when the wire is pulled into the through-hole from the connected steel.

  As described above, in the tension material tensioning method of the present invention, the tension material can be inserted while suppressing twisting of the through hole provided in the structure, and one strand of steel is provided. Even if tension is introduced one by one, a predetermined tension can be easily introduced into all the steel strands.

1 is a schematic side view of a cable-stayed bridge to which a tension material tensioning method according to an embodiment of the present invention is applied, and a cross-sectional view of a bridge girder of the cable-stayed bridge. It is a longitudinal cross-sectional view which shows the fixing | fixed part of the tension material which introduces prestress to the bridge girder shown in FIG. It is a longitudinal cross-sectional view which shows the fixing structure of the tension material used for the bridge girder shown in FIG. It is a schematic side view of the dummy tendon used when tensioning a tension girder on the bridge girder shown in FIG. It is a schematic sectional drawing which shows the state which penetrates the dummy tendon shown in FIG. 4 to the through-hole provided in the cross beam. It is a schematic sectional drawing which shows the state which the insertion to the through-hole of a dummy tendon was completed. It is a schematic sectional drawing which shows the state which connected one of the steel strands which comprise a tension material to one dummy steel strand of a dummy tension material. It is an expanded side view which shows the connection part of a dummy steel strand and a steel strand. It is sectional drawing of a stranded wire. It is a schematic sectional drawing which shows the state which pulls a wire from a dummy steel and draws a wire from a steel in a through-hole. It is a schematic sectional drawing which shows the state which the penetration to the through-hole of the wire from the 1st steel was completed. It is a schematic sectional drawing which shows the state which draws in a strand from the 2nd or less steel strand in a through-hole. It is a schematic sectional drawing which shows the state which completed the process which replaces with a dummy steel strand and inserts the strand from the steel which comprises a tendon into a through-hole.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The cable-stayed bridge shown in FIG. 1 is bridged between the first abutment 1 and the second abutment 2, and the first pier is provided between the first abutment 1 and the second abutment 2. 3 and the second pier 4 are provided to support the bridge girder 8. And the main towers 5 and 6 are set up above the bridge girder 8 from the upper part of the first pier 3 and the second pier 4, and the slanting material stretched obliquely downward from the main towers 5 and 6. 7, the bridge girder 8 is suspended and supported.

The bridge girder 8 is made of concrete, and as shown in FIG. 1 (b), is composed of an upper floor slab 11, a lower floor slab 12, and four webs 13 that join them up and down and has a cross section. It has a box shape, and the web 13 is provided so as to be inclined. A tension member 20 for introducing prestress in the axial direction of the bridge girder 8 is stretched in an inner space in which the cross section of the bridge girder 8 has a box shape. As shown in FIG. 2, the tension member 20 is inserted through the first beam pier 3 and the second beam pier 4 with the through holes 31 formed in the cross beams 9 and 10 provided in the bridge beam 8, and the tension force The reaction force is applied to the cross beams 9 and 10 to be fixed.
The through hole 31 is formed by embedding a tubular sheath in the concrete of the cross beams 9 and 10 and has a curved portion in the cross beam so that the tension member 20 is bent down on the tension end side. It has become.

The tendon 20 is a bundle of steel strands, and in the present embodiment, 19 strands of steel strands having an outer diameter of 15.7 mm by twisting seven steel wires are used. Yes. As shown in FIG. 3, the fixing device for the tension member 20 includes a diameter expanding pipe 32 embedded in an opening end portion of the through hole, a bearing plate 33 on which the steel wire 21 is locked, and a steel wire 21. And a wedge 34 for locking to the pressure bearing plate 33.
The expanded pipe 32 is connected to the sheath 35 embedded in the cross beam 9, and is provided with projecting portions 32 a and 32 b on the outer peripheral surface, and the reaction force of the tension material 20 is dispersed and transmitted to the concrete of the cross beam 9. It can be done.
The bearing plate 33 is in contact with the end face of the diameter expansion pipe 32 and transmits the reaction force transmitted from the wire 21 to the diameter expansion pipe 32 from each steel. The bearing plate 33 is provided with the same number of holes as the number of strands 21 of steel, and the diameter of the holes increases from the contact surface with the diameter expansion tube 32 toward the distal end side of the strands 21 of the steel. It has become. A wedge 34 is mounted between the steel wire 21 inserted into the hole and the inner peripheral surface of the hole, and the steel wire 21 is locked to the bearing plate 33 by the wedge 34.

Next, a process of inserting the steel strand 21 through the through hole 31 provided in the cross beam will be described.
First, as shown in FIG. 4, a dummy tendon 40 is prepared. The dummy tendon is a bundle of wires having a diameter similar to that of a wire used as a tendon. The wire is bundled in the same number as the number of wires from the steel constituting the tendon according to the arrangement when inserted into the through hole 31. As the wire rod of the dummy tension member 40, it is desirable to use a wire that is slightly larger in diameter than the wire 21 that is the same as the steel wire 21 that is used as the tension member 20 or the steel 21 that is used as the tension member 20. In addition, it is a wire that can be flexibly bent and can be used as long as it has sufficient strength to draw the wire from the steel into the through hole and has low frictional resistance on the peripheral surface. A wire rod or the like can also be used. In the present embodiment, a stranded wire having the same diameter is used.

  The dummy steel strand 41 used as the wire rod of the dummy tension member 40 is cut by about 2 m longer than the length of the through hole 31. It can be gripped for connection to 21 and for traction. In order to bundle these dummy steel wires 41, an adhesive tape or the like can be used, and a shape holding jig 51 for holding the positions of the dummy steel wires at both ends and, if necessary, an intermediate portion is used. Is desirable.

As shown in FIG. 5, the dummy steel strand 41 bundled as described above is connected to the rope 53 by attaching the cable grip 52 to the tip portion. The rope 53 is pulled using a pulling machine such as human power or a winch, and the dummy tendon 40 is pulled into the through hole 31.
The cable grip 52 firmly holds the wire 41 from the dummy steel and has a spindle shape at the tip side so that it can smoothly move in the through hole.

  When the dummy steel wire 41 is drawn into the through-hole 31, the cable grip 52 is removed, and the dummy steel wire 41 is inserted into the hole provided in the bearing plate 33 at the end on the tension side as shown in FIG. The support plate 33 is arranged at a predetermined fixing position. And as shown in FIG. 7, one strand 21-1 of the steel strand which comprises a tension | tensile_strength material is connected to the edge part on the opposite side to the tension | tensile_strength end of one dummy strand 41 using the connecting tool 54. As shown in FIG. .

As shown in FIG. 8, the connection tool 54 is a substantially cylindrical member having both ends rounded and curved, and has an outer diameter slightly smaller than the outer diameter of the wire 41 than the dummy steel. The connecting tool 54 is provided with a central hole 54a penetrating in the axial direction, and a plurality of screw holes 54b communicating with the central hole from the side surface are formed. The inner diameter of the center hole 54a is such that seven steel strands 21 and core wires 21a and 41a of dummy steel strands 41 can be inserted. That is, as shown in FIG. 9 (a), the seven stranded steel wires are obtained by twisting six outer peripheral wires 21b having the same diameter around one core wire 21a, and six outer peripheral wires 21b. When the tip of the core wire 21a is cut, the core wire 21a is exposed, and the core wire 21a can be inserted into the center hole 54a of the connector 54. Further, the core wire 41a of the dummy steel wire can be similarly inserted into the center hole 54a from the opposite side of the connector 54. Then, a bolt is screwed into the screw hole 54b from the side surface of the connector 54, and the tip is pressed against the core wires 21a and 41a inserted into the center hole. Thereby, the connecting tool 54 is firmly joined with the steel strand 21 and the dummy strand 41, and the steel strand 21 and the dummy strand 41 are connected.
As shown in FIG. 9 (b), the steel stranded wire is formed by twisting a plurality of first outer peripheral wires 61b having different outer diameters around one core wire 61a and a second outer peripheral wire 61c outside thereof. 19 or more can also be used. Even in such a case, the first outer peripheral line 61b and the second outer peripheral line 61c are cut while leaving only one core wire 61a, or only the second outer peripheral line 61c is cut and the connector is joined. You can also.

  When one strand of steel strand 41-1 and one of the strands of steel constituting the tension member 21-1 are connected to each other, as shown in FIG. Pull the steel wire 21-1 into the through hole 31. As a result, as shown in FIG. 11, the dummy steel wire 41-1 is replaced with the permanent steel wire 21-1. At this time, since the outer diameter of the connection tool 54 is smaller than the outer diameter of the wire 41 than the dummy steel, the connection tool 54 is less likely to become a resistance when the wire 21 is drawn into the through hole 31.

  When one steel strand 21-1 is inserted, the second dummy steel strand 41-2 and the two-side steel strand 21-2 are connected as shown in FIG. Similarly, the wire 41-2 is pulled from the dummy steel and the steel wire 21-2 constituting the tendon is drawn into the through hole 31. In the same manner, all the dummy steel wires 41 are sequentially replaced with the main steel wires 21.

  When all the steel strands 21 are inserted into the through-holes 31 as shown in FIG. 13, small jacks for single strands are attached to the steel strands 21 in a predetermined order, and each steel strand is inserted. Sequentially introduce tension into 21 and fix. As a result, the tension member 20 in which the steel strands 21 are bundled is stretched between the two cross beams 9 and 10 in a state where a predetermined tension force is introduced.

  In addition, in the said embodiment, the time which introduces tension | tensile_strength to each of each steel strand 21 is made after inserting all the steel strands 21 in the through-hole 31, However, One steel strand is made into dummy steel. It is also possible to introduce tension after replacing the stranded wire and insert the stranded wire and introduce the tensile force sequentially.

  Moreover, in the said embodiment, although the tension material 20 was stretched in the interior space of the bridge girder 8 used as the box-shaped cross section, the tension material is arrange | positioned in the tensioning method of the present invention. It can be applied regardless of the position. Further, the present invention can also be applied to the case where the slanted suspension member 7 for supporting the bridge girder 8 from the main towers 5 and 6 is inserted and stretched through the through holes formed in the bridge girder 8 or the main towers 5 and 6.

1: first abutment, 2: second abutment, 3: first pier, 4: second pier, 5: first main tower, 6: second main tower, 7: slanting material, 8: Bridge girder, 9, 10: Horizontal girder,
11: Upper floor slab, 12: Lower floor slab, 13: Web,
20: Tensile material, 21: Stranded steel, 21a: Core wire, 21b: Peripheral wire,
31: Through-hole, 32: Expanded pipe, 33: Pressure bearing plate, 34: Wedge, 35: Sheath,
40: dummy tendon, 41: dummy steel strand,
51: Jig for holding shape, 52: Cable grip, 53: Rope, 54: Connector, 54a: Center hole, 54b: Screw hole,
61: Stranded steel

Claims (4)

Inserting the vicinity of the ends of the tension members bundled with a plurality of steel strands, respectively, through the through holes provided in the structure, and reacting both ends to the structure with tension applied to the tension members A tension material tensioning method that is fixed
The step of inserting the vicinity of at least one end of the tendon into the through hole,
Prepare a wire rod having a diameter approximately the same as that of the steel strand and long enough to hold both ends from the through-hole, and adjoin the same number of wires as the number of wires from the steel of the tension material Bundling in a state where the wires are in contact with each other as a dummy tendon, inserting the dummy tendon through the through hole of the structure,
Connecting one end of one wire constituting the dummy tendon to one steel strand constituting the tendon,
Grabbing the other end of the wire connected to the steel strand and pulling it out from the through hole, instead of the wire, pulling the wire from the steel into the through hole,
The tension characterized in that the step of connecting the wire to a strand of steel and the step of drawing the wire and drawing the wire from the steel into a through-hole are sequentially performed on the other strands of steel from the tension member. How to stretch the material.   After pulling out all the wires of the dummy tendon from the through hole, and inserting all of the strands of the steel constituting the tendon into the through hole, one by one, the tension force is introduced sequentially, and the structure is sequentially introduced. The tension material tensioning method according to claim 1, wherein the tension material is fixed to the tension material.   After pulling out one wire rod of the dummy tendon from the through hole and inserting one of the steel strands constituting the tendon into the through hole, a tension is introduced into the wire from the steel and fixed. 2. The tension material tensioning method according to claim 1, wherein for all the steel strands, the steps of drawing the strands of the steel wires into the through-holes and introducing and fixing the tension force are sequentially repeated. As the steel stranded wire, using a core wire disposed in the center and an outer peripheral wire twisted around the core wire,
The step of connecting the wire and the steel stranded wire is performed by cutting the outer peripheral wire at an end of the steel stranded wire, and joining the exposed core wire to a connector to be joined to the wire.
The tension member tensioning method according to claim 1, 2 or 3, wherein the connecting tool is one having an outer diameter smaller than the outer diameter of the wire.

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