Method for fixing FRP tensioning material

Abstract

To enable a filler to be charged across an entire length of a tendon insertion hole of a precast member on which the tendon insertion hole having length disallowing a shrinkage-compensating mortar to be charged is formed.SOLUTION: A fixation method of an FRP tendon (3) in a pre-stressed concrete member (1) includes a first injection step to inject a first filler (5) for fixing the FRP tendon to a precast member (2) to a first end section S1 on one end side in a longer direction of a tendon insertion hole 4, a second injection step to inject a second filler (6) having higher fluidity than the first filler to a central section S2 positioned at a center in the longer direction of the tendon insertion hole, and a third injection step to inject the first filler to a second end section S3 on the other end side in the longer direction of the tendon insertion hole.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This Disclosure relates to a method for fixing an FRP tendon in a prestressed concrete member and a fixing structure of the FRP tendon.

Background Art

[0002] PC steel materials are sometimes used as tendons for applying prestress to concrete members. In precast concrete members, ducts are embedded, and PC steel materials are inserted into the ducts. After the PC steel materials are tensioned, both ends are fixed with fixing tools. The fixing tools hold the tension of the PC steel materials by fixing both ends of the PC steel materials to the precast member. The inside of the duct may be filled with grout. By filling with grout, corrosion of the PC steel materials is prevented, and the PC steel materials are held by the concrete member through the grout. In recent years, fiber reinforced plastic (FRP) may be used as a tendon instead of metal.

[0003] Patent Document 1 discloses a method for applying prestress to a concrete main girder using FRP as a tendon. This method is performed by an operator according to the following procedure. The concrete main girder has a duct for inserting an FRP tendon and rectangular recesses arranged near both ends of the concrete main girder and formed to communicate with the duct. Each of the two recesses opens on the upper surface of the concrete main girder. First, FRP is inserted into the duct and the recesses and tensioned. The ends of the aramid FRP cannot be fixed to the precast member by the fixing tools used for PC steel materials. Therefore, after tensioning, a filler such as cement mortar or resin mortar is injected into both recesses and the duct. The mortar filled in both recesses fixes the FRP to the concrete main girder and holds the tension of the FRP.

Prior Art Documents

Non-Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-133648 [Overview of the project] [Problems that the invention aims to solve]

[0005] Because mortar has low fluidity, even if mortar is injected into the sheath from the recessed portion, as in Patent Document 1, it is difficult to fill the entire length of the sheath with mortar. If mortar is filled only into the recessed portion, the FRP tensioning material can be fixed to the precast main girder. However, if there is a void in the center of the sheath through which the tensioning material is inserted (tensioning material insertion hole), the strength of that part will be lower than that of the ends, and there is also a risk that the FRP tensioning material will wear down due to friction with the sheath of the precast member or other FRP tensioning materials due to vibration, etc.

[0006] In view of the above background, the present invention aims to enable the filling of a filler material along the entire length of a tensioning material insertion hole in a precast member that is formed in a tensioning material insertion hole that is too short to be filled with mortar. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a method for fixing an FRP tensioning member (3) in a prestressed concrete member (1), comprising the steps of: inserting the FRP tensioning member into a tensioning member insertion hole (4) formed in a precast member (2) (Figure 3(B)); tensioning the FRP tensioning member inserted into the tensioning member insertion hole (Figure 3(C)); and, with the FRP tensioning member tensioned, placing the FRP tensioning member in the first end section (S1) on one end (4a) side in the longitudinal direction of the tensioning member insertion hole, in the precast part The method includes a first injection step (Figure 4(D)) in which a first filler (5) is injected to fix the material; a second injection step (Figure 4(E)) in which, with the FRP tensioning material under tension, a second filler (6) having higher fluidity than the first filler is injected into the tensioning material insertion hole in the central section (S2) located in the center of the longitudinal direction of the tensioning material insertion hole; and a third injection step (Figure 4(F)) in which, with the FRP tensioning material under tension, the first filler is injected into the second end section (S3) on the other end side of the longitudinal direction of the tensioning material insertion hole.

[0008] According to this embodiment, by performing the first to third injection steps, the filler can be filled into the tensioner insertion hole over a longer length. In addition, by injecting a second filler, which has higher fluidity than the first filler, into the tensioner insertion hole in the second injection step, the filler can be filled into the tensioner insertion hole over a longer length compared to when only the first filler is injected.

[0009] In the above embodiment, the second injection step is performed after the first injection step, and in the second injection step, the second filler is injected from the position where the first filler injected in the first injection step was injected; and the third injection step is performed after the second injection step, and in the third injection step, the first filler is injected from the position where the second filler injected in the second injection step was injected.

[0010] According to this embodiment, in the second and third injection steps, it is possible to suppress the retention of air between the first and second fillers in the tensioner insertion hole. Furthermore, in both steps, the filler can be filled into the tensioner insertion hole while pushing out the air inside.

[0011] In the above embodiment, in the first injection step, the first filler is filled from one end of the tensioning material insertion hole to a first position (P1) which is a first length distance longer than the fixing length for fixing the FRP tensioning material to the precast member; in the second injection step, the second filler is injected from a second position (P2) which is one end side of the first position (P1) and the other end side of the position which is a fixing length distance from one end of the tensioning material insertion hole to a third position (P3) which is a predetermined length distance from the other end of the tensioning material insertion hole; and in the third injection step, the first filler is injected from a fourth position (P4) which is a second length distance longer than the fixing length from the other end of the tensioning material insertion hole and is one end side of the third position.

[0012] According to this embodiment, the first filler is injected into a section longer than the fixing length required to fix the FRP tensioning material to the precast member, thereby fixing both ends of the FRP tensioning material to the precast member.

[0013] In the above embodiment, it is preferable that a first confirmation hole is formed at the first position (P1) of the tensioning material insertion hole for confirming the arrival of the first filler, and a second confirmation hole is formed at the third position (P3) of the tensioning material insertion hole for confirming the arrival of the second filler.

[0014] According to this embodiment, in the first injection step, after injecting the first filler, it can be determined that the first filler has filled the tensioner insertion hole from one end to the first position when the first filler reaches the first confirmation hole. Also, in the second injection step, after injecting the second filler, it can be determined that the second filler has filled from the second position to the third position when the second filler reaches the second confirmation hole. Therefore, it is possible to more reliably suppress the retention of air between the first filler and the second filler in the tensioner insertion hole.

[0015] In the above embodiment, the first filler is preferably a non-shrink mortar, and the second filler is preferably a PC grout with higher fluidity than the first filler.

[0016] According to this embodiment, by using PC grout, which has higher fluidity than non-shrink mortar, the filler can be easily filled into the tensioning material insertion holes over lengths that cannot be filled with non-shrink mortar.

[0017] Furthermore, in order to solve the above problems, the present invention provides an anchoring structure for an FRP tensioning material (3) in a prestressed concrete member (1), wherein the prestressed concrete member comprises a precast member (2) having a tensioning material insertion hole (4) formed therein, the FRP tensioning material placed in the tensioning material insertion hole, a first filler (5) that fills at least both ends (S1, S3) of the tensioning material insertion hole and anchors both ends of the FRP tensioning material to the precast member, and a second filler (6) that fills the longitudinal central part (S2) of the tensioning material insertion hole, wherein the fluidity of the second filler in its uncured state is higher than that of the first filler in its uncured state.

[0018] According to this aspect, by filling the first filler at both ends of the tension member insertion hole, both ends of the FRP tension member in a tensioned state can be fixed to the precast member. Also, by filling the second filler in the central portion of the tension member insertion hole, a fixing structure body without a cavity can be constructed. Thereby, it is possible to prevent the FRP tension member from rubbing against and wearing on the concrete member or other FRP tension members due to vibration or the like. Further, since the second filler is filled in the central portion in the longitudinal direction of the tension member insertion hole, the filler can be filled over the entire length of the tension member insertion hole with a small number of injection times, and the process can be shortened.

Effect of the Invention

[0019] The present invention can fill the filler over the entire length of the tension member insertion hole of a precast member in which a tension member insertion hole having a length that cannot be filled with mortar is formed.

Brief Description of the Drawings

[0020] [Figure 1] Side view of a prestressed concrete floor slab according to an embodiment [Figure 2] Enlarged cross-sectional view of both ends of a prestressed concrete floor slab [Figure 3] Explanatory drawing of a method for fixing an FRP tension member [Figure 4] Explanatory drawing of a method for fixing an FRP tension member

Modes for Carrying Out the Invention

[0021] Hereinafter, with reference to the drawings, embodiments of a method for fixing an FRP tension member and a fixing structure of an FRP tension member according to the present invention will be described. In the embodiment, an example of a prestressed concrete floor slab to which the fixing structure of an aramid FRP tension member 3 is applied will be described.

[0022] Figure 1 is a side view of a prestressed concrete slab 1 according to an embodiment of the present invention. The prestressed concrete slab 1 is constructed by connecting a plurality of precast slab members 2 placed on a girder. In the figure, the precast slab members 2 are numbered 21, 22, 23, ..., 2 from left to right. (n―1) , 2 n These are denoted by symbols. These precast slab members 2 are sometimes collectively referred to as precast slab members 2. These precast slab members 2 are integrated by introducing prestress with aramid FRP tensioning material 3, thereby constructing a prestressed concrete slab 1.

[0023] Figure 2 is an enlarged cross-sectional view of both ends of the prestressed concrete deck slab 1. As shown in Figure 2, each precast deck slab member 2 has tension member insertion holes 4 that extend in the direction of the bridge axis. When multiple precast deck slab members 2 are arranged in predetermined positions, these tension member insertion holes 4 become continuous in the direction of the bridge axis, forming a single tension member insertion hole 4.

[0024] A tensioned aramid FRP tensioning material 3 is placed in the tensioning material insertion hole 4. Non-shrink mortar 5 is filled at both ends of the tensioning material insertion hole 4 as a first filler material for fixing the aramid FRP tensioning material 3 to the precast deck member 2. The non-shrink mortar 5 is filled into the tensioning material insertion hole 4 over a length longer than a predetermined fixing length L for fixing the aramid FRP tensioning material 3. At least one precast deck member 2 located at each end in the bridge axis direction is a fixing deck member for fixing the aramid FRP tensioning material 3. Hereinafter, the left end portion of the tensioning material insertion hole 4 filled with non-shrink mortar 5 will be referred to as the first end section S1, and the right end portion of the tensioning material insertion hole 4 filled with non-shrink mortar 5 will be referred to as the second end section S3.

[0025] In the portion of the tensioning material insertion hole 4 that is not filled with non-shrink mortar 5, i.e., the central part of the tensioning material insertion hole 4, PC grout 6 is filled as a second filler material to fill the cavity. In its uncured state, PC grout 6 has higher fluidity than non-shrink mortar 5. Hereinafter, the central part of the tensioning material insertion hole 4 filled with PC grout 6 will be referred to as the central section S2. The filler material is injected from the left end 4a, which is one end in the longitudinal direction of the tensioning material insertion hole 4, to the right end 4b, which is the other end.

[0026] Precast floor slab member 22 adjacent to precast floor slab member 21 located at the left end and precast floor slab member 2 located at the right end n Adjacent to precast floor slab member 2 (n―1) The tension member insertion holes 4 are provided with injection ports 7, 10 and discharge ports 8, 9. The tension member insertion holes 4 of the precast floor slab member 2 may be formed by a sheath, and the injection ports 7, 10 and discharge ports 8, 9 may be provided on a coupler connecting the sheaths. Also, the precast floor slab members 23-2 (n―2) The tensioning material insertion hole 4 may be provided with an auxiliary inlet and outlet.

[0027] The inlet ports 7 and 10 extend downward from the lower side of the tensioning member insertion hole 4 to the underside of the precast slab member 2. The outlet ports 8 and 9 curve from the upper side of the tensioning member insertion hole 4 of the precast slab member 2 to the underside of the precast slab member 2. Since the inlet ports 7 and 10 and the outlet ports 8 and 9 open on the underside of the precast slab member 2 and there are no openings on the upper side, the risk of deterioration factors entering from the road surface is avoided.

[0028] The left injection port 7 provided in the tensioning member insertion hole 4 of the precast slab member 22 is located at the left end of the central section S2 of the tensioning member insertion hole 4. Hereinafter, this position will be referred to as the second position P2. The second position P2 is located at a distance from the left end 4a of the tensioning member insertion hole 4 of the precast slab member 2 by a length longer than the anchorage length L. The left discharge port 8 provided in the tensioning member insertion hole 4 of the precast slab member 22 is located near the right side of the second position P2. Hereinafter, this position will be referred to as the first position P1. The second position P2 is also located at a distance from the left end 4a of the tensioning member insertion hole 4 of the precast slab member 2 by a length longer than the anchorage length L.

[0029] Precast floor slab member 2 (n―1) The right-side discharge port 9 provided in the tensioning member insertion hole 4 is located near the left end of the second end section S3 of the tensioning member insertion hole 4. Hereinafter, this position will be referred to as the third position P3. The third position P3 is located at a distance from the right end 4b of the tensioning member insertion hole 4 of the precast floor slab member 2 that is longer than the anchorage length L. (n―1) The right-side injection port 10 provided in the tensioning member insertion hole 4 is located near the left side of the third position P3 and at the left end of the second end section S3. Hereinafter, this position will be referred to as the fourth position P4. The fourth position P4 is also located at a distance from the right end 4b of the tensioning member insertion hole 4 of the precast floor slab member 2 by a length longer than the anchorage length L.

[0030] The prestressed concrete slab 1 is constructed as described above. Next, the method for fixing the aramid FRP tensioning material 3 in the prestressed concrete slab 1 will be explained using Figures 3 and 4. The following work will be performed by workers.

[0031] As shown in Figure 3(A), multiple precast deck members 2 are placed in predetermined positions. In this state, the tension member insertion holes 4 are continuous in the direction of the bridge axis and open at the left end 4a and the right end 4b. Valves are provided at the lower ends of the precast deck members 2 of the inlet ports 7 and 10 and outlet ports 8 and 9. From Figure 3(B) onward, the valves are omitted from the illustration.

[0032] As shown in Figure 3(B), aramid FRP tensioning members 3 are inserted into tensioning member insertion holes 4 that are continuous in the direction of the bridge axis. After inserting the aramid FRP tensioning members 3, the aramid FRP tensioning members 3 are tensioned using a tensioning device 11, as shown in Figure 3(C). A jack or the like may be used as the tensioning device 11. After tensioning the aramid FRP, an injection hose 12 is provided at the left end 4a of the tensioning member insertion hole 4, and a discharge hose 13 is provided at the other end of the tensioning member insertion hole 4. The discharge hose 13 only needs to be provided by the step shown in Figure 4(F), which will be described later.

[0033] As shown in Figure 4(D), with the aramid FRP tensioning material 3 tensioned by the tensioning device 11, non-shrink mortar 5 is injected into the tensioning material insertion hole 4 from the injection hose 12, filling the non-shrink mortar 5 from the left end 4a of the tensioning material insertion hole 4 to the first position P1. During the injection of the non-shrink mortar 5, the valves at the first position P1 and the second position P2 are kept open. After it is confirmed that the non-shrink mortar 5 is being discharged from the injection port 7 at the second position P2, the valve at the second position P2 is closed. Next, after it is confirmed that the non-shrink mortar 5 is being discharged from the discharge port 8 at the first position P1, the valve at the first position P1 is closed to stop the injection of the non-shrink mortar 5.

[0034] As shown in Figure 4(E), after the injection of the non-shrink mortar 5, and before the non-shrink mortar 5 hardens, the valve at the second position P2 is opened, and PC grout 6 is injected into the tensioning material insertion hole 4 from the injection port 7 at the second position P2, filling the PC grout 6 up to the third position P3. During the injection of PC grout 6, the valves at the first position P1, third position P3, and fourth position P4 are kept open. After the discharge of PC grout 6 from the injection port 10 at the fourth position P4 is confirmed, the valve at the fourth position P4 is closed. Next, after the discharge of PC grout 6 from the discharge port 9 at the third position P3 is confirmed, the valve at the third position P3 is closed to stop the injection of PC grout 6. If the injection port 7 at the second position P2 is blocked by the non-shrink mortar 5 during the above-mentioned non-shrink mortar 5 injection work, PC grout 6 may be injected through a spare injection port provided in another precast floor slab member 23 located in the central section S2.

[0035] As shown in Figure 4(F), after the injection of the PC grout 6, non-shrink mortar 5 is injected into the tensioning member insertion hole 4 from the injection port 10 at the fourth position P4, filling the tensioning member insertion hole 4 up to its right end 4b. After confirmation that the non-shrink mortar 5 has been discharged from the discharge hose 13 provided at the right end 4b of the tensioning member insertion hole 4, the injection of non-shrink mortar 5 is stopped.

[0036] After the process shown in Figures 3 and 4, the non-shrink mortar 5 filled in the first end section S1 and the second end section S3 is hardened. As a result, both ends of the aramid FRP tensioning material 3 are positioned at both ends in the bridge axis direction of the precast deck members 21, 2 n The tensioning device 11 is then removed, and the aramid FRP tensioning material 3 exposed from both ends of the tensioning material insertion hole 4 is cut off. In addition, valves and hoses (12, 13), etc. attached to the injection ports 7, 10 and discharge ports 8, 9 that open on the underside of the precast floor slab member 2 are removed. With the above steps completed, the prestressed concrete floor slab 1 is constructed.

[0037] In this way, by filling the first end section S1 on the left end 4a side of the tensioning member insertion hole 4 and the second end section S3 on the right end 4b side of the tensioning member insertion hole 4 with non-shrink mortar 5, both ends of the tensioned aramid FRP tensioning member 3 can be fixed to the precast slab member 2. Furthermore, by filling the central section S2 from the second position P2 to the fourth position P4 with PC grout 6, a fixing structure without voids can be constructed. This structure prevents the aramid FRP tensioning member 3 from rubbing against the precast slab member 2 or other aramid FRP tensioning members 3 due to vibration or other factors.

[0038] If the central section S2 is long and it is difficult to fill it with non-shrink mortar 5, the injection work must be carried out multiple times while moving to different locations, resulting in poor workability. In contrast, in the above embodiment, PC grout 6 is filled into the central section S2 instead of non-shrink mortar 5. PC grout 6 has higher fluidity than non-shrink mortar 5 in its uncured state. Therefore, the filler can be easily filled into the tension material insertion holes 4 over lengths that cannot be filled with non-shrink mortar 5. As a result, PC grout 6 can be easily injected into the central section S2, which is long enough that the injection work for non-shrink mortar 5 is difficult, with fewer injections, improving workability and shortening the process.

[0039] Furthermore, in the method for fixing the aramid FRP tensioning material 3 of the embodiment, by performing the three injection steps shown in Figures 4(D) to (F), the filler material can be filled into the tensioning material insertion hole 4 over a longer length. In addition, as shown in Figure 4(E), by injecting PC grout 6, which has higher fluidity than non-shrink mortar 5, into the tensioning material insertion hole 4 in the central section S2, the filler material is filled into the tensioning material insertion hole 4 over a longer length compared to when non-shrink mortar 5 is injected.

[0040] As shown in Figure 4, the three injection steps shown in Figures 4(D) to (F) are performed in this order, so that the tension material insertion holes 4 are filled from left to right. This allows the tension material insertion holes 4 to be filled while pushing out the air inside during the injection of each filler material. In addition, in the section between the second position P2 and the first position P1, and in the section between the fourth position P4 and the third position P3, the section in which the non-shrink mortar 5 is injected and the section in which the PC grout 6 is injected overlap. This suppresses the retention of air between the non-shrink mortar 5 and the PC grout 6 inside the tension material insertion holes 4.

[0041] Furthermore, in the injection step shown in Figure 4(E), by injecting PC grout 6 from the second position P2 on the other end side of the tensioning member insertion hole 4, which is located at a distance of anchorage length L from the left end 4a of the tensioning member insertion hole 4, the first end section S1 filled with non-shrink mortar 5 becomes longer than the anchorage length L. Also, in the injection step shown in Figure 4(F), by injecting non-shrink mortar 5 from the fourth position P4, which is located at a distance of longer than the anchorage length L from the right end 4b of the tensioning member insertion hole 4, the second end section S3 filled with non-shrink mortar 5 becomes longer than the anchorage length L. Thus, both ends of the FRP tensioning member are anchored to the precast slab member 2.

[0042] As explained with reference to Figure 4, by opening the relevant valve during the injection process, the filler material can be filled into the tensioner insertion hole 4 while pushing out the air inside the hole. Furthermore, in the injection process of the non-shrink mortar 5 shown in Figure 4(D), the outlet 8 at the first position P1 functions as a first confirmation hole that confirms that the non-shrink mortar 5 has reached the first position P1. In addition, in the injection process of the PC grout 6 shown in Figure 4(E), the outlet 9 at the third position P3 functions as a second confirmation hole that confirms that the PC grout 6 has reached the third position P3. This more reliably suppresses the retention of air between the non-shrink mortar 5 and the PC grout 6 inside the tensioner insertion hole 4.

[0043] This concludes the description of specific embodiments. However, the present invention is not limited to the above embodiments or modifications and can be broadly modified and implemented. For example, in the above embodiments, the FRP tensioning material fixing method and fixing structure according to the present invention are applied to a prestressed concrete deck slab 1, but they may also be applied to a box girder bridge. Furthermore, the specific configuration, arrangement, quantity, material, or construction procedure of each member or part can be changed as appropriate, as long as it does not depart from the spirit of the present invention. In addition, not all of the components shown in the above embodiments are necessarily essential and can be selected as appropriate. [Explanation of Symbols]

[0044] 1: Prestressed concrete slab 2: Precast floor slab members 3:FRP tension material 4: Tensioner insertion hole 4a: Left end (one end) 4b: Rightmost (other end) 5: Non-shrink mortar (first filler) 6: PC Grout (Second Filling Material) 8: 1st confirmation hole (discharge port) 9:Second confirmation hole (discharge port) L: Fixing length S1: First end section S2: Central section S3: Second end section P1: 1st position P2: 2nd position P3: 3rd position P4: 4th position

Claims

1. A method for fixing FRP tensioning material in a prestressed concrete member, The steps include inserting the FRP tensioning material into the tensioning material insertion hole formed in the precast member, The steps include: tensioning the FRP tensioning material inserted into the tensioning material insertion hole, With the FRP tensioning material under tension, a first injection step is performed in which a first filler material is injected into the first end section on one end side in the longitudinal direction of the tensioning material insertion hole to fix the FRP tensioning material to the precast member. With the FRP tensioning material under tension, a second injection step is performed in which a second filler, which has higher fluidity than the first filler, is injected into the central section located in the longitudinal center of the tensioning material insertion hole. The third injection step includes injecting the first filler into the second end section on the other end in the longitudinal direction of the tensioning material insertion hole while the FRP tensioning material is under tension, The second injection step is performed after the first injection step, and in the second injection step, the second filler is injected from the position where the first filler injected in the first injection step was injected. A method for fixing an FRP tensioning material, wherein the third injection step is performed after the second injection step, and in the third injection step, the first filler is injected from the position where the second filler injected in the second injection step was injected.

2. In the first injection step, the first filler is filled from one end of the tensioning material insertion hole to a first position that is separated by a first length longer than the fixing length for fixing the FRP tensioning material to the precast member. In the second injection step, the second filler is injected from the second position which is one end closer to the first position and the other end closer to the position a fixed distance from one end of the tensioning material insertion hole, and the second filler is filled up to the third position which is a predetermined distance away from the other end of the tensioning material insertion hole. The method for fixing an FRP tensioning material according to claim 1, wherein in the third injection step, the first filler is injected from a fourth position which is spaced a second length longer than the fixing length from the other end of the tensioning material insertion hole and is located on the side of the one end that is closer to the third position.

3. A method for fixing an FRP tensioning material according to claim 2, wherein a first confirmation hole is formed at the first position of the tensioning material insertion hole for confirming the arrival of the first filler material, and a second confirmation hole is formed at the third position of the tensioning material insertion hole for confirming the arrival of the second filler material.

4. A method for fixing an FRP tensioning material according to any one of claims 1 to 3, wherein the first filler is a non-shrink mortar and the second filler is PC grout.

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