JP2011241632A - Upper end part processing method of pc tendon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an upper end part processing method for PC tendon capable of economically performing a grout filling in an short construction period.SOLUTION: To fill grout 30 in a vertical sheath 20 near the upper end 101 of a vertical unbonded PC tendon 100 constructed with a post-tensioning system, there are provided a grout injection part 41 communicating an inside of the vertical sheath 20 to an outer face of concrete 40 and a foam polyurethane resin injection part 43 being at a position lower than the grout injection part 41 and communicating the inside of the vertical sheath 20 to the outer face of the concrete 40. Foam polyurethane resin 50 is injected into the vertical sheath 20 through the foam polyurethane resin injection part 43, and thereafter the grout 30 is injected into the vertical sheath 20 through the grout injection part 41.

Description

  The present invention relates to a method for processing an upper end portion of a PC tendon.

  In recent years, in a high-rise concrete structure such as a chimney and a tower-like structure such as a tower, a tank, or a building structure, a vertical sheath is provided in advance in the concrete structure, and a single wire is used as a PC tension member disposed in the vertical sheath. The use of wire bundles from PC steel, which is a high-capacity cable in which a plurality of PC steel wires and PC steel wires are bundled, has been increasing.

  Here, depending on the performance required for the concrete structure, it is often reasonable to adopt a so-called unbonded structure. In this case, the PC tension member arranged in the vertical sheath is not covered with a rust preventive protective coating in the vicinity of the fixing portion for fixing, and is not in the vertical sheath near the fixing portion not covered with the rust preventive protective coating. Only, it is preferable to fill grout mainly for rust prevention.

  However, since grout has fluidity, in order to fill grout into the longitudinal sheath, it is necessary to inject grout from the lower end of the longitudinal sheath and fill the entire length of the longitudinal sheath to the upper end of the longitudinal sheath. is there. Therefore, even when the PC tendon is an unbonded cable, the grout is filled even in the longitudinal sheath of the intermediate portion that is coated with the rust preventive material and does not require grout filling. When was long, there was a considerable waste.

  Conventionally, with regard to filling grout into the sheath, in a bridge structure in which PC tension members are arranged by the post tension method and the external cable method, a vacuum pump is used only on the back surface of the fixing portion of the outer cable where the sheath is disposed. A technique for injecting grout into a sheath has been proposed (see, for example, Patent Document 1). In this technique, grout stop spacers prevent grout outflow, but they cannot be completely prevented, so urethane foam is injected.

  Further, a technique has been proposed in which a free length portion of an earth anchor is covered with a sheath material, a foamed water-stopping agent such as urethane foam is injected into the sheath material, and foamed in the sheath material (see, for example, Patent Document 2). ).

JP 2004-353241 A Japanese Examined Patent Publication No. 61-229020

  As described above, in order to fill the vertical sheath with grout, it is necessary to inject grout from the lower end of the vertical sheath and fill the entire length of the vertical sheath to the upper end of the vertical sheath. Even in the case of a cable, the grout is filled even in the longitudinal sheath of the intermediate portion that is coated with the rust preventive material and does not require grout filling. In such a PC tendon, if the grout can be filled only in the longitudinal sheath in the vicinity of the fixing portion, a small amount of material and temporary equipment or construction equipment can be used, but the grout is not filled over the entire length of the longitudinal sheath. Therefore, a large amount of them are required, which requires a long construction period and a cost increase. In addition, since there is a limit on the injection height in order to inject the grout from the lower part to the upper part of the vertical sheath, the injection operation is performed several times, especially when the grout is filled in the vertical sheath provided in the ultra-high concrete structure. It was necessary to divide the work into two parts, and the necessity of a scaffold for that was also a factor in the construction period and cost.

  In view of the above circumstances, an object of the present invention is to provide a method for treating the upper end portion of a PC tendon that can be economically constructed in a short construction period.

  The upper end portion processing method of the PC tendon material of the present invention that achieves the above object includes a grout injection portion communicating with the inside of the vertical sheath from the outer surface of the concrete when filling the grout into the vertical sheath in the vicinity of the upper end portion of the PC tendon material. A foamed polyurethane resin injection part communicating with the inside of the vertical sheath from the concrete outer surface below the grout injection part, and injecting the polyurethane foam resin into the vertical sheath through the foamed polyurethane resin injection part, The grout is injected into the vertical sheath through the grout injection part.

  The method of treating the upper end portion of the PC tendon according to the present invention is to inject a foamed polyurethane resin into the vertical sheath through the foamed polyurethane resin injecting portion provided below the grout injecting portion, and then to the vertical through the grout injecting portion. In this method, grout is injected into the sheath. Therefore, the foamed polyurethane resin filled in the vertical sheath acts as a grout flow stop, and the grout can be filled only in the vertical sheath near the upper end of the PC tendon. Therefore, according to the method for treating the upper end portion of the PC tendon of the present invention, the grout injection operation, which generally requires a large amount of material and temporary equipment or equipment for construction, is minimized, and grout filling is performed. Economical construction with a short construction period.

  Here, in the method for treating the upper end of the PC tendon of the present invention, the foamed polyurethane resin is a two-part foamed urethane that rapidly foams and cures by a thermal reaction, and the filling amount is controlled by the injection time of the two-part foamed urethane. Is preferred.

  According to such a preferable form, it is possible to reliably fill the vertical sheath with an amount of foamed polyurethane resin necessary and sufficient to support the weight of the grout filled in the vertical sheath.

  Further, in the method for treating the upper end portion of the PC tendon according to the present invention, the PC tendon is an aggregate of a plurality of longitudinal unbonded PC tendons, and the plurality of longitudinal directions of the portions to be filled with the foamed polyurethane resin are used. It is also a preferred form that a spacer ring is inserted into each of the unbonded PC tendons.

  When such a spacer ring is inserted, a gap enough to allow the foamed polyurethane resin to enter between the plurality of longitudinally unbonded PC tendons is formed. Therefore, when the foamed polyurethane resin is injected, the foamed polyurethane resin spreads between the plurality of longitudinal unbonded PC tendons. Therefore, the foamed polyurethane resin is reliably filled in the vertical sheath, and the grout can be reliably prevented from flowing down. In particular, when the longitudinal sheath is disposed obliquely, the longitudinal unbonded PC tendon is biased so that there is no gap between them and filling is hindered. Therefore, it is preferable to insert a spacer ring.

  Furthermore, in the method for treating the upper end portion of the PC tendon according to the present invention, it is more preferable that the longitudinal sheath of the portion to be filled with the foamed polyurethane resin has a shape having a ring-shaped pleat.

  According to such a preferred embodiment, the foamed polyurethane resin injected into the longitudinal sheath is likely to spread throughout the filling site in the longitudinal sheath along the ring-shaped folds. Therefore, the foamed polyurethane resin is reliably filled in the vertical sheath, and the grout can be prevented from flowing down reliably.

  ADVANTAGE OF THE INVENTION According to this invention, the upper-end part processing method of PC tendon which can construct grout filling economically with a short construction period is provided.

It is explanatory drawing explaining each process in the upper end part processing method of the longitudinal direction unbonded PC tendon which is one Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  Drawing 1 is an explanatory view explaining each process in an upper end part processing method of longitudinal direction unbonded PC tendon material 100 which is one embodiment of the present invention.

  As shown in FIG. 1, a vertical sheath 20 made of, for example, polyethylene is disposed so as to vertically penetrate concrete 40. In the longitudinal sheath 20, a longitudinal unbonded PC tendon 100 is applied by a post tension method. Thereby, a compressive force is applied to the concrete 40. The longitudinal unbonded PC tendon 100 is an aggregate obtained by combining, for example, seven longitudinal unbonded PC steel materials 10 each having a diameter of 15.2 mm. Moreover, this longitudinal direction unbonded PC tension material 100 has a portion where the upper end portion 101 is not covered with a rust preventive protective coating. Moreover, the diameter of the part by which the antirust material protection coating of each longitudinal direction unbonded PC steel material 10 is about 20 mm, for example. The longitudinal sheath 20 has, for example, a shape having ring-shaped pleats 21 having a wave pitch of 30 mm, and has an inner diameter of 80 mm and an outer diameter of 92 mm, for example.

  In filling the grout 30 into the longitudinal sheath 20 in the vicinity of the upper end 101 of the longitudinal unbonded PC tendon 100 that is not covered with the rust preventive protective material, first, the longitudinal sheath 20 communicates from the outer surface of the concrete 40. A grout injection part 41 is provided. Further, a grout discharge part 42 is provided above the grout injection part 41.

  Further, a foamed polyurethane resin injection portion 43 communicating from the outer surface of the concrete 40 into the vertical sheath 20 is provided below the grout injection portion 41. Further, a foamed polyurethane resin preliminary injection part 44 is provided further below the foaming polyurethane resin injection part 43.

  Further, a spacer ring 60 having a thickness of 3 mm and a length of 50 mm, for example, is provided on each of the seven longitudinal unbonded PC steel materials 10 that are covered with the rust preventive material and are coated with the foamed polyurethane resin 50. They are inserted in the vertical direction with an interval of 20 mm. The spacer ring 60 may be inserted by inserting the longitudinal unbonded PC tendon 100 into the longitudinal sheath 20 and then pulling it upward once, or inserting the longitudinal unbonded PC tendon 100 into the longitudinal sheath. You may insert before inserting in 20. When such a spacer ring 60 is inserted, a gap enough to allow the foamed polyurethane resin 50 to enter between the seven longitudinal unbonded PC steel materials 10 is formed. Therefore, when the foaming polyurethane resin 50 is injected, the foaming polyurethane resin 50 spreads between the seven longitudinal unbonded PC steel materials 10. Therefore, the foamed polyurethane resin 50 is reliably filled in the vertical sheath 20 and the flow of the grout 30 can be reliably prevented.

  Next, the polyurethane foam resin 50 is injected into the vertical sheath 20 through the polyurethane foam resin injection portion 43. If the foamed polyurethane resin 50 cannot be injected from the foamed polyurethane resin injection part 43 due to some trouble, the foamed polyurethane resin 50 is injected into the vertical sheath 20 through the foamed polyurethane resin preliminary injection part 44. As described above, since the vertical sheath 20 has the ring-shaped pleats 21, the foamed polyurethane resin 50 injected into the vertical sheath 20 is filled in the vertical sheath 20 along the ring-shaped folds 21. Easy to spread throughout. Therefore, the foaming polyurethane resin 50 is reliably filled in the vertical sheath 20, and the flow of the grout 30 can be reliably prevented.

  Here, the foamed polyurethane resin 50 is a two-component foamed urethane that rapidly foams and cures by a thermal reaction of two components (for example, an isocyanate and a polyol) having an expansion ratio of 30 times, for example. In addition, an amount to fill a gap having a sheath length of 800 mm or more is injected in 5 ± 2 seconds. Thereby, a sufficient amount of foamed polyurethane resin 50 necessary to support the weight of the grout 30 filled in the vertical sheath 20 can be reliably filled in the vertical sheath 20.

  Thereafter, the grout 30 is injected into the longitudinal sheath 20 through the grout injection part 41.

  According to the method for treating the upper end portion of the longitudinal unbonded PC tendon 100 of the present embodiment described above, the foamed polyurethane resin 50 filled in the longitudinal sheath 20 acts as a flow stop for the grout 30, and the post tension system. The grout 30 can be filled only in the longitudinal sheath 20 in the vicinity of the upper end portion 101 of the longitudinal unbonded PC tendon 100 constructed in the above. Therefore, the grout injection operation, which generally requires a large amount of material and temporary equipment or equipment for construction, is minimized, and grout filling can be carried out economically in a short construction period.

  In the above-described embodiment, the example in which the PC tendon according to the present invention is a longitudinal unbonded PC tendon has been described. However, the PC tendon according to the present invention is not limited to this, and how PC tension material may be used.

  Moreover, in the Example mentioned above, although the PC tension material said to this invention demonstrated the example which is the aggregate | assembly which united seven longitudinal direction unbonded PC steel materials 10, this PC tension material said to this invention is this. However, the present invention is not limited to this, and it may be a single PC tendon, or may be an assembly of a plurality of longitudinally unbonded PC tendons.

  In the above-described embodiment, the example in which the vertical sheath according to the present invention has a ring-shaped pleat has been described. However, the vertical sheath according to the present invention is not limited to this, and the ring-shaped fold is not limited thereto. However, it is preferable that at least the longitudinal sheath of the portion to be filled with the foamed polyurethane resin has a shape having ring-shaped pleats.

  In the above-described embodiments, the two-component foamed urethane referred to in the present invention has been described as an example of injecting the filling amount in a gap having a sheath length of 800 mm or more in 5 ± 2 seconds. Is not limited to this, and it is preferable to control the filling amount by the injection time of the two-component foamed urethane.

DESCRIPTION OF SYMBOLS 100 Longitudinal unbonded PC tension material 10 Longitudinal unbonded PC steel material 101 Upper end part 20 Longitudinal sheath 21 Ring-shaped fold 30 Grout 40 Concrete 41 Grout injection part 42 Grout discharge | emission part 43 Foaming polyurethane resin injection | pouring part 44 Foaming polyurethane resin preliminary injection part 50 Firing Polyurethane resin 60 Spacer ring

Claims (4)

  When filling grout into the vertical sheath in the vicinity of the upper end of the PC tendon, a grout injection part communicating from the outer surface of the concrete into the vertical sheath, and a communication from the outer surface of the concrete below the grout injection part into the vertical sheath. A foaming polyurethane resin injection part for injecting polyurethane resin into the vertical sheath through the foaming polyurethane resin injection part, and then injecting grout into the vertical sheath through the grout injection part A method for treating the upper end of a PC tendon characterized by the above.   2. The top end treatment of a PC tendon material according to claim 1, wherein the foamed polyurethane resin is a two-component foamed urethane that rapidly foams and cures by a thermal reaction, and the filling amount is controlled by an injection time of the two-component foamed urethane. Method.   The PC tendon is an aggregate of a plurality of longitudinal unbonded PC tendons, and a spacer ring is inserted into each of the plurality of longitudinal unbonded PC tendons in a portion to be filled with the foamed polyurethane resin. The upper end part processing method of PC tension material of Claim 1 or 2 characterized by these.   The upper end portion processing method for a PC tendon material according to any one of claims 1 to 3, wherein a longitudinal sheath of a portion to be filled with the foamed polyurethane resin is formed into a shape having a ring-shaped pleat.

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