JP3720781B2 - PC steel material protection structure and PC steel material arrangement method in sheath curve portion of PC structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a PC steel material protection structure and a PC steel material arrangement method in which a centroid of a PC steel material and a sheath centroid are matched in a sheath curve portion of a prestressed concrete (hereinafter referred to as PC) structure.
[0002]
[Prior art]
As one of methods for manufacturing PC, a post-tension method is conventionally known. In this post-tension method, a sheath such as a metal tube is first placed in a mold, and a PC steel material is inserted into the sheath. Next, the mold is filled with concrete, and after the concrete in the mold is cured, the PC steel material is tensioned to introduce prestress. The post-tension method is a method suitable for on-site construction because the PC steel is tensioned after the concrete is hardened.
[0003]
In particular, in PC structures such as bridges, compressive force acts on the upper side of the central part and tensile force acts on the lower side of the central part, while tensile force acts on the upper side of the intermediate fulcrum part (bridge pier part) and compresses on the lower side. Force acts. Therefore, in the PC structure using the post-tension method, the PC steel centroid at the center is below the structure cross-sectional centroid and the PC steel centroid on the intermediate fulcrum is the structure to use PC steel efficiently. Arranged so as to be above the cross-sectional centroid.
[0004]
In the design calculation, the centroid of the PC steel is designed to match the centroid of the sheath, but the PC steel cannot be refracted and placed. PC steel materials are arranged in a curved line. The curve radius of this PC steel material is designed with a radius that allows a curve to be naturally formed by elastic deformation.
[0005]
In the post-tension method, grout is filled in the sheath from the viewpoint of improving the corrosion resistance of the PC steel material and ensuring the integrity of the PC steel material and the concrete structure. When the grout is filled in the sheath, the grout does not leave a void in the sheath and the periphery of the sheath in order to improve the corrosion resistance of the PC steel and to ensure the integrity of the PC steel and the concrete structure. It is desirable to fill so that the grout thickness is equal.
[0006]
[Problems to be solved by the invention]
However, by tensioning the PC steel at the site, the centroid of the PC steel is placed above the sheath centroid at the center of the PC steel [see FIGS. 4a and c], and at the intermediate fulcrum than the sheath centroid. Located on the bottom [see FIGS. 4a and d]. Therefore, in the design calculation document, the centroid of the PC steel material is designed so that it substantially coincides with the centroid of the sheath, but the actual PC steel centroid is eccentrically arranged in a direction in which the introduction prestress is smaller than the design value. The That is, the amount of prestress applied to the actual PC structure cross section is less than the calculated value, and the prestress applied to that amount is insufficient with respect to the calculated value.
[0007]
As a result of the PC steel material being arranged as described above, the grout thickness filled around the PC steel material arranged in the sheath is filled in an uneven state, and the sheath and the PC steel material come into contact with each other. In this case, it becomes difficult to ensure the integrity of the PC steel material and the concrete structure.
[0008]
The present invention has been made to solve the above-mentioned problems of the prior art. The PC steel material centroid and the sheath are arranged at the central part and the intermediate fulcrum part in the PC structure while efficiently arranging the PC steel material. By matching the centroid with the centroid, an object is to eliminate the shortage of prestress due to the placement error of the PC steel material in the field and to uniformly fill the periphery of the PC steel material with grout.
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a PC structure in which a sheath is arranged in a curved shape in a bent-up section and a bent-down section of a PC steel material. A spacer for fixing the PC steel material to be inserted into the sheath centroid is disposed, the PC steel material insertion hole concentric with the central axis is formed in the center, and the PC steel material is disposed around the PC steel material insertion hole. A grout passage portion extending in the axial direction of the spacer is provided so as to exclude portions corresponding to the upper and lower portions that are in strong contact with the spacer.
In the invention of claim 2, in the invention of claim 1, four support protrusions are formed on the outer peripheral side of the spacer so as to form a cross shape, of which the thick support protrusions are arranged in the upper and lower parts, The tip of each support projection is formed in a curved surface that comes into surface contact with the inner wall of the sheath, and a grout passage is formed between each support projection in a notch shape extending in the axial direction of the spacer. The outer peripheral portions at both ends in the axial direction are chamfered in a curved shape.
[0010]
The invention of claim 3 is the invention of claim 1, wherein the spacer is formed in a columnar shape having an outer diameter slightly smaller than the inner diameter of the sheath, and a plurality of grout passage portions are provided outside the PC steel material insertion hole. Is opened so as to extend in the axial direction of the spacer and to exclude portions corresponding to the upper and lower portions.
According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the spacer can be divided into two parts vertically from the center in the axial direction. A step is provided.
[0011]
The invention according to claim 5 relates to the invention according to any one of claims 1 to 4, and the portions corresponding to the curve start point, the curve intermediate part, and the curve end part of the sheath of the PC steel material cut to a predetermined length in advance. After the spacers are fixed to the PC steel material, the PC steel material is inserted into the sheath.
[0012]
The invention according to claim 6 relates to the invention according to any one of claims 1 to 4, wherein the curve start point portion, the curve intermediate portion, and the curve end point portion of the sheath are formed by a joint sheath that can be removed by sliding, and the sheath The PC steel material is inserted into the sheath in a connected state, and then the joint sheath is slid, and the spacer is fixed to the curve start point portion, curve middle portion and curve end point portion of the sheath. is there.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1a is a longitudinal sectional view showing an outline of the present invention. The present invention is a PC steel material protection structure applied to a PC structure 2 in which a sheath 1 is arranged in a curved shape, such as a bridge girder of a bridge, for example.
[0014]
In the present invention, in the center portions R1, R2 and the intermediate fulcrum portion R3 where the sheath 1 is arranged in a curved shape, the curve start point portion r1, the curve intermediate portion r2, and the curve end point portion r3 of R1, R2, and R3, A spacer 4 for fixing the PC steel material 3 to the sheath centroid is disposed. As a result, as shown in FIGS. 1b to 1d, the PC steel centroid and the sheath centroid substantially coincide. Note that two or more spacers 4 arranged in the curve middle portion r2 may be arranged as R2 in FIG. 1a.
[0015]
In the PC steel material protection structure of the present invention, the procedure for fixing the spacer 4 differs depending on the method of inserting the PC steel material 3 into the sheath 1. Hereinafter, each PC steel material arrangement | positioning method is demonstrated concretely by an Example.
[0016]
[Example 1]
In Example 1, the spacer 4 is fixed in advance to the positions corresponding to the curve start point r1, the curve intermediate part r2, and the curve end point r3 of the sheath 1 in the PC steel 3 in advance, and then the PC steel 3 is placed in the sheath 1 in advance. How to insert.
[0017]
FIG. 2 is a view showing the spacer 4 used in the PC steel material arranging method of the first embodiment. Although the spacer 4 used in Example 1 is not limited, it is particularly preferably formed of MC nylon (monomer casting nylon). In addition, the spacer 4 of Example 1 has four cross-sectional shapes in the circumferential direction, and four support protrusions 4b are formed in a cross shape on the outer peripheral side of the cylindrical portion where the inner peripheral side becomes the PC steel material insertion hole 4a. The tip of each bearing projection 4b is formed in a curved surface so as to come into surface contact with the inner wall of the sheath 1. In Example 1, the thick support protrusions 4b are arranged at the upper and lower portions of the spacer 4 where the spacer 4 and the PC steel material 3 are in strong contact, and the PC steel material bearing strength of the spacer 4 is ensured. On the other hand, a grout passage portion 4 c is formed in a notch shape extending in the axial direction of the spacer 4 between the support protrusions 4 b.
[0018]
In addition, the circumferential cross-sectional shape of the spacer 4 of the first embodiment is set so that the cross-shaped support protrusion 4b is accommodated in a circle having a slightly smaller diameter than the inner diameter of the sheath 1, and the spacer 4 can be inserted into the sheath 1. It is like that. In order to facilitate the insertion of the spacer 4 into the sheath 1 and to prevent the spacer 4 from being caught by the joint portion of the sheath 1, the outer peripheral portions at both axial ends of the spacer 4 are chamfered in a curved shape.
[0019]
Furthermore, the spacer 4 of Example 1 is configured by connecting two identically-shaped parts facing each other with a bolt 5 and a nut 6 so that the spacer 4 can be easily attached to the PC steel material 3, and from the axial center. It can be divided into two. The dividing surface of the spacer 4 crosses the center of the two support protrusions 4b. The spacer 4 is formed with bolt holes on the left and right so as to vertically cut the divided support projections 4b. Note that a step 4d is provided on the dividing surface of the spacer 4 so that alignment when the spacer 4 is connected is easy.
[0020]
Hereinafter, the PC steel material arrangement method of Example 1 will be described in order.
[0021]
(A1) First, the rebar is assembled in the mold of the PC structure 2 and the sheath 1 is arranged. And the some PC steel material 3 cut | disconnected by the predetermined length required for the prestress introduction | transduction operation | work of PC structure 2 is bundled.
[0022]
(A2) Next, the spacers 4 are fixed at locations corresponding to the curve start point r1, the curve intermediate part r2, and the curve end point r3 of the sheath 1 in the bundled PC steel material 3, respectively. The spacer 4 may be slid from the end of the PC steel material 3, but it is preferable to attach the two spacers 4 to the PC steel material 3 by bolting because the workability is improved.
[0023]
(A3) Then, the PC steel material 3 to which the spacer 4 is fixed is inserted into the sheath 1. Specifically, when the PC steel material 3 is small, the PC steel material 3 to which the spacer 4 is fixed is manually pushed from the inlet side to the outlet side of the sheath 1. When the PC steel material 3 is a medium size, a lead rope is attached to a cable grip or a cable drawing tool, and the PC steel material 3 to which the spacer 4 is fixed is pulled and pulled from the outlet side of the sheath 1 with a winch.
[0024]
(A4) Thereafter, concrete 7 is placed outside the sheath 1 in the mold. And after the concrete 7 in a formwork hardens | cures, tension | tensile_strength is introduce | transduced into PC steel material 3 by tension | tensile_strength introduction means, such as a jack arrange | positioned on the mold outer side. In the present invention, the centroid of the PC steel material 3 substantially coincides with the centroid of the sheath 1 by the spacers 4 arranged at the curve start point r1, the curve intermediate part r2 and the curve end point r3 of the sheath 1. Therefore, the amount of eccentricity of the PC steel material 3 can be taken according to the design calculation document, and prestress does not become insufficient with respect to the calculated value.
[0025]
(A5) After fixing the PC steel material 3 with the fixing tools 8 arranged at both ends of the PC structure 2, the grout 9 is filled in the sheath 1 to complete the PC structure 2. In the present invention, the PC steel material 3 is arranged so that the centroid of the sheath 1 substantially coincides with the centroid of the sheath 1, and the grout 9 is smoothly filled through the grout passage 4 c of the spacer 4. Therefore, the PC steel material 3 does not come into contact with the inner wall of the sheath 1, and the grout 9 in the sheath 1 is filled evenly around the PC steel material 3, and the PC steel material 3 and the concrete structure can be integrated, The durability of the PC structure 2 can be improved.
[0026]
[Example 2]
Example 2 is a method in which, after the PC steel material 3 is inserted into the sheath 1, the spacer 4 is fixed to the curve start point r1, the curve intermediate part r2, and the curve end point r3. In addition, the same code | symbol is attached | subjected to the structure same as Example 1 in Example 2, and description is abbreviate | omitted.
[0027]
FIG. 3 is a view showing the spacer 4 used in the PC steel material arranging method of the second embodiment. Although the spacer 4 used in Example 2 is not limited, it is particularly preferably formed of MC nylon (monomer casting nylon). The overall shape of the spacer 4 of Example 2 is formed in a columnar shape whose outer diameter is slightly smaller than the inner diameter of the sheath 1 so that the spacer 4 can be inserted into the sheath 1. In the center of the spacer 4, a PC steel material insertion hole 4 a is opened concentrically on the central axis of the spacer 4.
[0028]
A plurality of grout passage portions 4 c are opened outside the PC steel material insertion hole 4 a of the spacer 4 so as to extend in the axial direction of the spacer 4. In order to secure the PC steel material bearing strength of the spacer 4, the grout passage portion 4 c is opened so as to exclude portions corresponding to the upper and lower portions where the spacer 4 and the PC steel material 3 are in strong contact.
[0029]
Further, the spacer 4 of the second embodiment is configured by connecting two parts having the same shape facing each other so that the spacer 4 can be easily attached to the PC steel material 3, and can be divided into two from the axial center. ing. Note that a step 4d is provided on the dividing surface of the spacer 4 so that alignment when the spacer 4 is connected is easy.
[0030]
Hereinafter, the PC steel material arrangement method of Example 2 will be described in order.
[0031]
(B1) First, the rebar is assembled in the mold of the PC structure and the sheath 1 is arranged. At this time, the sheath 1 is cut before a fixed portion of the spacer 4 [curve start point r1, curve intermediate portion r2 and curve end point r3] to leave a certain interval. The sheath 1 is connected to the fixing portion of the spacer 4 by covering the sheath 1 with a joint sheath 10 having a slightly larger diameter than the sheath 1 of the other part. The seam between the sheath 1 and the joint sheath 10 is sealed and fixed with a tape 11.
[0032]
(B2) Next, a predetermined number of PC steel materials 3 are inserted into the connected sheaths 1 at a high speed by a pushing machine.
[0033]
(B3) After the insertion of the PC steel material 3, the tape 11 at the seam of the sheath 1 is peeled off, and the joint sheath 10 is slid. Then, the PC steel material 3 is bundled at the fixing position of the spacer 4, and the two split spacers 4 are fixed to the PC steel material 3. After the spacer 4 is fixed, the joint sheath 10 is returned to the original position and sealed with the tape 11, and the sheath 1 is connected again. This step is repeated at the fixed portion of each spacer 4. Since the following steps are the same as those in the first embodiment, they are omitted.
[0034]
As mentioned above, although the PC steel material protection structure and the PC steel material arrangement | positioning method in the sheath curve part of the PC structure of this invention were demonstrated, the technical scope of this invention is not limited to the said description. For example, the present invention is not limited to the illustrated bridge girder and can be widely applied to PC structures such as beams.
[0035]
【The invention's effect】
In the present invention, the centroid of the PC steel material substantially coincides with the centroid of the sheath by the spacers arranged at the curve start point portion, the curve middle portion and the curve end point portion of the sheath. Therefore, the amount of eccentricity of the PC steel material can be taken according to the design calculation document, and the effect that the prestress is insufficient with respect to the calculated value is solved.
[0036]
According to the present invention, in the present invention, the PC steel material is disposed so that the centroid of the PC material substantially coincides with the centroid of the sheath, and the grout is smoothly filled through the grout passage portion of the spacer. Therefore, the PC steel material does not come into contact with the inner wall of the sheath, and the grout in the sheath is uniformly filled around the PC steel material, so that the PC steel material and the concrete structure can be integrated, thereby improving the durability of the PC structure. Can be improved.
[Brief description of the drawings]
FIG. 1A is a longitudinal sectional view showing an outline of the present invention. 2B is a cross-sectional view taken along line AA in FIG. 1A, FIG. 3C is a cross-sectional view taken along line BB in FIG. 1A, and FIG. It is C sectional drawing.
FIGS. 2A and 2B are a plan view and a side view showing spacers used in the PC steel material arranging method of Example 1. FIGS.
FIGS. 3A and 3B are a plan view and a side view showing spacers used in the PC steel material arranging method of Example 2. FIGS.
FIG. 4A is a longitudinal sectional view showing an outline of a conventional example. 2B is a cross-sectional view taken along line AA in FIG. 1A, FIG. 3C is a cross-sectional view taken along line BB in FIG. 1A, and FIG. It is C sectional drawing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sheath 2 PC structure 3 PC steel material 4 Spacer 4a PC steel material insertion hole 4b Supporting protrusion 4c Grout passage part 4d Step 5 Bolt 6 Nut 7 Concrete 8 Fixing tool 9 Grout 10 Joint sheath 11 Tape 12 Abutment 13 Bridge pier R1, R2 Center (Sheath curve)
R3 Intermediate fulcrum (sheath curve)
r1 curve start point r2 curve middle r3 curve end point

Claims (6)

In the PC structure in which the sheath is arranged in a curved shape in the bent-up section and the bent-down section of the PC steel material,
Place the spacer to fix the PC steel material inserted through the sheath to the sheath centroid at the curve start point, curve middle and curve end point of the sheath,
In the spacer, a PC steel material insertion hole concentric with the central axis is formed in the center, and around the PC steel material insertion hole, a portion corresponding to the upper and lower portions that are in strong contact with the PC steel material is excluded . A PC steel material protection structure in a sheath curve portion of a PC structure, wherein a grout passage portion extending in the axial direction is provided. Four support projections are formed on the outer peripheral side of the spacer so as to form a cross shape, of which the thick support projections are arranged in the upper and lower portions, and the tip of each support projection is in surface contact with the inner wall of the sheath The grout passage portion is formed in a notch shape extending in the axial direction of the spacer between the support protrusions, and the outer peripheral portions at both ends in the axial direction are chamfered in a curved shape. PC steel protective structure in sheaths curved portion of claim 1 PC structure, wherein a. The spacer is formed in a cylindrical shape whose outer diameter is slightly smaller than the inner diameter of the sheath, and a plurality of grout passage portions extend in the axial direction of the spacer on the outer side of the PC steel material insertion hole, and upper and lower portions The PC steel material protection structure in the sheath curve portion of the PC structure according to claim 1 , wherein the hole is opened so as to exclude a portion corresponding to . 4. The spacer according to any one of claims 1 to 3, wherein the spacer can be divided into two parts in the vertical direction from the axial center, and a step for alignment is provided on the divided surface. The PC steel material protection structure in the sheath curve part of the PC structure described in the item.   In the PC steel material protection structure in the sheath curve part of the PC structure according to any one of claims 1 to 4, a curve start point part, a curve middle part, and a curve end part of the sheath of the PC steel material cut in advance to a predetermined length A PC steel material arranging method, wherein a PC steel material is inserted into a sheath after fixing a spacer at a position corresponding to each of the above.   In the PC steel material protection structure in the sheath curve part of the PC structure according to any one of claims 1 to 4, the joint start point part, the curve middle part and the curve end part of the sheath are slidable and removable joint sheaths. After forming and connecting the sheath with the PC steel material inserted into the sheath, the joint sheath is slid, and the spacer is fixed to the curve start point portion, the curve middle portion and the curve end point portion of the sheath. Steel material placement method.

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