JP3443734B2 - How to tension the tendon - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for tensioning tension members having different lengths and tensions. 2. Description of the Related Art In the case where the lengths of the tendon members such as a ground anchor and a PC cable are different and thus the amount of elongation of the tendon members at the time of tension is different, conventionally, each tendon member (a1, a2, a3) is used. Tension was achieved using jacks b that operate independently and individually (see FIG. 6). Further, as described in Japanese Patent Publication No. 2655820, there is a method in which the difference in elongation of each tendon is stretched in the order of length of the tendon, and finally all the tendons are tensioned and fixed. In this method, first, only the longest tendon is fixed to the jack and tension is applied by the difference in elongation from the second longest tendon, and then the second longest tendon is also fixed to the jack. Then, the first and second long tendons are tensioned by the difference between the third and long tendons. Repeat this procedure to tension all tendons. [0003] The above-mentioned conventional tensioning method for tension members has the following problems. <B> The jack that operates independently for each tendon is
The structure is complicated and it is large compared to a normal jack. For this reason, it may not be easy to handle and it may be difficult to install the anchor on the head. <B> In the method in which the tension members are tensioned from the longest, the other tension members are not tensioned when the longest tension member is tensioned by the amount of elongation. For this reason, it is necessary to add an internal play to the amount of elongation of the tendon material which is secondly tense. However, since this play is not obtained by calculation, only the unscheduled tension may be introduced into the second and subsequent tendons. <C> In the above case, when all the tension members are tensioned at once and the total tension is set to a predetermined value, an excessive load may be introduced to a long tension member that has been tensioned at an early stage. is there. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a tensioning method for a tension member which can be easily implemented. In particular, it is an object of the present invention to provide a tensioning method of a tension member which can be performed by a simple procedure using a jack having a simple structure. Also,
An object of the present invention is to provide a tensioning method for a tensioning member that can accurately introduce a tensioning force into each tensioning member. The present invention achieves at least one of these objects. [0005] In order to achieve the above object, a method for tensioning a tendon according to the present invention comprises, in a method for tensioning a plurality of tendons, a jack at an end of the tendon. Install, attach the grippers to all the tendons and fix the tendons to the jacks.Tension all the tendons to the minimum value of the elongation against the tension of each tendon calculated in advance, Fix the tension member corresponding to the amount of elongation to the anchor head, remove only the gripper of this tension member, and, among the remaining tension members fixed to the jack, until the calculated amount of elongation reaches the minimum value, The tension member corresponding to the minimum elongation among the remaining tension members is fixed to the anchor head, only the gripper of this tension member is removed, and the front of the remaining tension member fixed to the jack is removed. This method is characterized in that the above steps are repeated until the tendon material fixed to the jack is exhausted. Here, the total tension can be confirmed after fixing all the tension members. The total tension is confirmed by measuring the lift-off load. Embodiments of the present invention will be described below with reference to the drawings. <A> Application Conditions The present invention is applied to a ground anchor or a PC cable having a plurality of tendons having different lengths. Also, the present invention can be applied to a case where a plurality of tendons having different tensions are to be tensioned. A ground anchor having a plurality of tendon members having different lengths is, for example, a tendon member having a different length (11, 12, 1).
3) is a distributed compression-type anchor (see FIG. 1) which is processed into a U-shape, attached to the load-bearing body 4, and integrally inserted into the anchor hole 5. Further, in order to disperse the fixing positions of the tendon members, the present invention can also be applied to a dispersed tensile anchor (see FIG. 4) constructed by inserting tendon members 14 having different lengths into the anchor holes 5. Further, the case where a plurality of tendons having different tensions are to be tensioned means, for example, a case where the lengths of the tension members are the same and the amount of elongation of the tension members is different due to the different tension. <B> Calculation of the amount of elongation P is the tension introduced into the tendon, the effective rate η of the tension against the friction generated in the tendon, E is the elastic modulus of the tendon, A is the cross-sectional area of the tendon. Assuming that the length of the tendon is L, the elongation δ of the tendon can be calculated by the following equation. Δ = Pη · L / (EA) Here, the length of the first tendon 11 is L1, the length of the second tendon is L2, and the length of the third tendon is L3. Then, the amounts of elongation are calculated as δ1, δ2, and δ3 from the above equation. In addition, a set loss is added to the elongation δ of the tendon material as necessary. <C> Installation of jack The anchor head 3 and the jack 2 are installed at the ends of the tendon. That is, each tendon (11, 1
Anchor head 3 for fixing tendons in 2, 13)
Attach. The anchor head 3 is a tendon fixing device having a hole through which the tendon is inserted. A wedge 31 is loaded into the hole of the anchor head 3 in the gap between the inserted tendon and the hole. The wedge 31 is released when the tension member is tensioned, and when the tension is stopped, the wedge bites into the gap between the tension member and the hole to fix the tension member. The jack 2 has an anchor hole 5 with respect to the anchor head 3.
And installed on the opposite side. The tendons (11, 12, 13) are fixed to the jack 2 by inserting the grippers 21 through holes in the jack head 22 of the jack. As the jack 2, for example, a jack of a type in which all the tension members loaded, such as a center hole type jack, are tensioned by an equal amount of elongation is used. This type of jack has a simple structure, is easy to handle, and can be reduced in size.
Also, there are few jack failures. <D> Tension of all tendons First, all the tendons are tensioned. First, grippers 21 are loaded into all the tendons (11, 12, 13) and fixed to the jack head 22 (see FIG. 1). If jack 2 is operated in this state,
All tendons are strained. Tension of all tendons is performed until the elongation of the tendons calculated above reaches the minimum value. Here, when the material of each tendon is the same and the magnitudes of the introduced tensions P are equal, the length of the tendon is the shortest (in this case, the third tendon 13), the amount of elongation is the smallest. Value (δ3). The amount of elongation of the tendon is confirmed by the stroke of the jack 2 or the like. In addition, since all the tension members are tensioned first, all the tension members can be adapted at once. That is, first take the slack in each tendon. As a result, the subsequent tension is introduced directly into all tendons. <E> Fixing of the tension members and removal of the gripper After tensioning all the tension members (11, 12, 13) until the amount of elongation of the tension members reaches the minimum value (δ3), the tension members are fixed. . The fixation of the tendon is automatically performed by the wedge 31 loaded in the gap between the tendon inserted into the hole of the anchor head 3 and the hole. Then, the third tendon 13 fixed to the jack head 22
The gripper 21 is removed (see FIG. 2). Even if the jack 2 is operated in this state, no tension is introduced into the third tension member 13. <F> The remaining tension members (11, 12) fixed to the tension jacks 2 of the remaining tension members are tensioned. That is, the first tension member 11 in a state where the gripper 21 is loaded.
And the second tension member 12 is tensioned. These tensions are applied to the remaining tendon (1) fixed to the jack.
The process is performed until the calculated elongation reaches the minimum value (δ2) in the cases of (1, 12). The elongation indicates a value obtained by summing the elongation from the beginning. When all the tendons are strained, the stretch amount has already been stretched to δ3, so the additional strain amount is (δ2−δ3). <G> After the tension is fixed until the total elongation of the tension member and the removal of the gripper reaches δ2, the tension member is fixed. Further, the gripper 21 of the second tendon 12 fixed to the jack head 22 is removed (see FIG. 3). Finally, the first tension member 11 is tensioned and fixed until the total amount of elongation reaches δ1. Here, the case where the tendon has three types of lengths has been described as an example, but the present invention is naturally applicable to a case where the number of tendons is larger than this. In this case, the tension and fixing are performed by repeating the process for the remaining tension member fixed to the jack. <H> Confirmation of fixing load After fixing all the tension members, the tension introduced to the ground anchor or the like can be confirmed. To check the total tension of all tendons,
First, jack chair ring 2 surrounding anchor head 3
3 is inserted between the jack 2 and the anchor head 3. Here, since the jack chair ring 23 is higher than the anchor head 3, the reaction force of the jack 2 does not act on the anchor head 3. Then, the grippers 21 are attached to all the tension members (11, 12, 13) and fixed to the jack head 22. When the jack 2 is operated in this state, the anchor head 3 rises when the tension of the jack 2 exceeds the tension introduced to the ground anchor or the like. The load at the time when the anchor head 3 is lifted is called a lift-off load, and can be said to be a tension introduced into a ground anchor or the like. According to the present invention, the following effects can be obtained because the method for tensioning the tendon material is as described above. <B> By adjusting the timing of removing the gripper and releasing from the jack for each tendon, tension is introduced to the tendons having different lengths and tensions. For this reason, the tension members having different lengths and tensions can be tensioned using a type of jack that tensions all the tension members at once. A type of jack that tensions all tendons at once,
Since it is small and easy to handle, it is easy to implement. In addition, since the structure is simple, it is easy to use and is not easily broken. <B> The tension members having different lengths and tensions are tensioned by shifting the timing for fixing the tension members. Therefore, it can be easily implemented. <C> Tension all the tendons first. For this reason, the slack of each tendon is first removed, and the subsequent tension is transmitted directly to each tendon. For this reason, tension can be accurately introduced into each tension member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of an embodiment of the present invention when tensioning all tendon members. FIG. 2 is an explanatory view of fixing a tendon member with the smallest elongation amount of tendon members. FIG. 3 is an explanatory view of tensioning only the tendon having the largest amount of elongation of the tendon. FIG. 4 is an explanatory view of an embodiment in which the present invention is applied to a dispersed tension type anchor. FIG. 6 is a side view of a conventional jack that operates independently and independently for each tension member. [Description of References] 11... First tension member 12. 13. Third tendon 2 Jack 21 Gripper 3 Anchor head

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E04G 21/12 104 E02D 5 / 76,5 / 80 E01D 11/00

Claims (1)

(57) [Claims] [Claim 1] In a method for tensioning a plurality of tendons, jacks are installed at ends of the tendons, and grippers are attached to all tendons to fix the tendons to the jacks. , Of the amount of elongation with respect to the tension of each tendon calculated in advance,
Tension all the tendons to the minimum value, fix the tendon corresponding to the minimum elongation to the anchor head, remove only the gripper of this tendon, and, among the remaining tendons fixed to the jack, Tension the remaining tension members until the calculated amount of elongation reaches the minimum value, fix the tension member corresponding to the minimum elongation among the remaining tension members to the anchor head, remove only the gripper of this tension member, Said step for the remaining tendons fixed to the jack,
A method of tensioning a tendon, which is repeated until the tendon fixed to the jack is exhausted.