Precast concrete structure

Abstract

To provide a precast concrete structure capable of integrating precast concrete members with each other by a relatively simple joining method.SOLUTION: A precast concrete structure 1 is constituted by joining a first precast concrete member 10 and a second precast concrete member 20 at joint surfaces 11 and 21. The joint surface 11 of the first precast concrete member 10 is provided with a truncated cone-shaped convex part 14, and the joint surface 21 of the second precast concrete member 20 is provided with a concave part 24 into which the convex part 14 is fitted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a precast concrete structure constructed by joining precast concrete members together. [Background technology]

[0002] 2. Description of the Related Art Joint structures for joining precast concrete members together have been available in the past (see Patent Documents 1 and 2). Patent Document 1 shows a joint structure between non-combustible wall panels. A continuous recess is formed in the joint surface of one wall panel in the longitudinal direction, and a continuous protrusion is formed in the joint surface of the other wall panel in the longitudinal direction, and the width of the protrusion is narrower than the opening width of the recess. The wall panels are joined by inserting the protrusion of one wall panel into the recess of the other wall panel.

[0003] Patent Document 2 shows a joint structure of at least two precast members connected in series. The precast members are pressure-welded by tensioned precast steel members that penetrate the precast members, and the ends of the reinforcing bars embedded in the precast members are joined by mortar-filled joints and shear keys provided on both end faces of the precast members. The precast steel members penetrate the shear keys. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-197079 A [Patent Document 2] JP 2020-94391 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a precast concrete structure in which precast concrete members can be integrated together using a relatively simple joining method. [Means for solving the problem]

[0006] The inventors have discovered that a precast concrete structure for joining a pair of precast concrete members at their joint surfaces can be achieved relatively easily by providing a convex portion shaped like a truncated pyramid or a truncated cone on the joint surface of one of the precast concrete members, and providing a recess into which the convex portion fits on the joint surface of the other precast concrete member, and then fitting the two together. A precast concrete structure of a first invention (for example, precast concrete structures 1, 1A described below) is a precast concrete structure constructed by joining a first precast concrete member (for example, first precast concrete member 10, 10A described below) and a second precast concrete member (for example, second precast concrete member 20, 20A described below) at a joint surface (for example, joint surfaces 11, 21 described below), characterized in that the joint surface of the first precast concrete member is provided with a truncated pyramid or truncated cone-shaped convex portion (for example, convex portion 14 described below), and the joint surface of the second precast concrete member is provided with a concave portion (for example, concave portion 24 described below) into which the convex portion fits.

[0007] According to this invention, precast concrete members are joined not by using joint keys made of metal joints or by connecting rebars embedded in the precast concrete members with mechanical joints, but by fitting convex and concave parts provided on the joint surfaces of the precast concrete members together. Therefore, the precast concrete members can be integrated together using a relatively simple joining method. In addition, since no joint keys or reinforcing bars are embedded in the joint surfaces of precast concrete components, the tensile stress that occurs around the highly rigid joint keys and reinforcing bars can be suppressed, and the occurrence of cracks caused by tensile stress can be suppressed.

[0008] The precast concrete structure of the second invention is characterized in that the binder used in the first precast concrete member and the second precast concrete member is one in which 40% or more of ordinary Portland cement has been replaced with ground granulated blast furnace slag.

[0009] According to this invention, the binder used in the precast concrete members is one with a high mixing ratio of ground granulated blast furnace slag, such as blast furnace cement type C (more than 60% and not more than 70% blast furnace slag) or blast furnace cement type B (more than 30% and not more than 60% blast furnace slag). This makes it possible to reduce the amount of carbon dioxide emitted, which is proportional to the amount of ordinary Portland cement, during the production of the precast concrete members, thereby contributing to improving the global environment.

[0010] The precast concrete structure of the third invention is characterized in that communicating through holes (e.g., through holes 15, 25 described below) are formed around the convex portions and the concave portions of the first precast concrete member and the second precast concrete member, steel material (e.g., PC steel material 40 described below) is inserted into the through holes to introduce tension, and the through holes are formed with polyethylene or polypropylene sheath tubes (e.g., sheath tube 16 described below).

[0011] According to this invention, the convex and concave portions on the joint surfaces of the precast concrete members are fitted together, and these joint surfaces are pressed together by tension introduced into the PC steel, thereby making it possible to more firmly integrate the precast concrete members. In addition, since the through hole is formed using a polyethylene or polypropylene sheath tube, which has lower rigidity than a steel sheath tube, the tensile stress generated around the sheath tube can be suppressed, and the occurrence of cracks due to tensile stress can be suppressed. Effect of the Invention

[0012] According to the present invention, a precast concrete structure can be provided in which precast concrete members can be integrated together using a relatively simple joining method. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a vertical cross-sectional view of a precast concrete structure according to a first embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of the precast concrete structure of FIG. 1 according to an embodiment of the present invention; [Diagram 3] FIG. 2 is an enlarged view of the area surrounded by dashed line B of the precast concrete structure in FIG. 1. [Figure 4] 1 is a flowchart of a procedure for constructing a precast concrete structure according to the first embodiment. [Diagram 5] FIG. 2 is an explanatory diagram of the construction procedure of the precast concrete structure according to the first embodiment (part 1, the state after concrete is poured into the formwork and the state after the formwork is removed). [Figure 6] FIG. 2 is an explanatory diagram of the construction procedure of the precast concrete structure according to the first embodiment (part 2, the state in which the precast concrete members are arranged and joined at the construction site). [Figure 7] FIG. 5 is a longitudinal sectional view of a precast concrete structure according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a longitudinal cross-sectional view of a precast concrete member constituting a precast concrete structure according to a second embodiment. [Figure 9] 8 is a cross-sectional view of the precast concrete member shown in FIG. [Figure 10] 9 is an enlarged view of the portion surrounded by dashed line D of the precast concrete member in FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention is a precast concrete structure in which a pair of precast concrete members are joined together. In the first embodiment, a convex part having a truncated pyramid shape or a truncated cone shape is provided on the joint surface of one of the precast concrete members, and a concave part into which the convex part fits is provided on the joint surface of the other precast concrete member, so that the two are fitted together. In the second embodiment, in addition to the joint structure of the first embodiment, the precast concrete members are joined together by being tightened and pressure-bonded with prestressed concrete steel members to which tension has been applied. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same components are denoted by the same reference numerals, and the description thereof will be omitted or simplified. [First embodiment] Fig. 1 is a longitudinal sectional view of a precast concrete structure 1 according to a first embodiment of the present invention. Fig. 2 is a sectional view taken along line AA of the precast concrete structure 1 in Fig. 1. Fig. 3 is an enlarged view of a portion surrounded by a dashed line B of the precast concrete structure 1 in Fig. 1. The precast concrete structure 1 is the foundation of a structure, and is constructed by joining a first precast concrete member 10 and a second precast concrete member 20 at their joint surfaces 11, 21. A fine joint 17 is formed between the joint surface 11 of the first precast concrete member 10 and the joint surface 21 of the second precast concrete member 20.

[0015] The first precast concrete member 10 is made of reinforced concrete and comprises a base 12 placed on the ground surface 2 and a wall portion 13 constructed on top of the base 12. The first precast concrete member 10 has two truncated cone-shaped protrusions 14 at the top and bottom of the joint surface 11. That is, the protrusions 14 have a shape that tapers toward the tip. The protrusions 14 have, for example, a base diameter of 150 mm, a tip diameter of 100 mm, and a height of 50 mm.

[0016] The second precast concrete member 20 comprises a base 22 placed on the ground surface 2 and a wall portion 23 constructed on the base 22. Further, recesses 24 into which the protrusions 14 fit are provided at two positions, top and bottom, on the joint surface 21 of the second precast concrete member 20. Inside the recesses 24, a space in the shape of a truncated cone is formed. As a result, the precast concrete members 10, 20 are joined together by fitting together the convex portions 14 and the concave portions 24.

[0017] The precast concrete members 10 and 20 are made of concrete using blast-furnace cement type C. That is, the cement used in the precast concrete members 10 and 20 is ordinary Portland cement mixed with more than 60% and not more than 70% ground granulated blast-furnace slag. In other words, if the mass of the entire cement is taken as 100%, the mass of the ground granulated blast-furnace slag is more than 60% and not more than 70%. The autogenous shrinkage strain of concrete using ordinary Portland cement was 50 to 70 × 10 after four weeks (28 days) after concrete was poured. -6 In contrast, concrete using blast-furnace slag cement had a viscosity of about 130×10 -6 In addition, drying shrinkage strain tends to converge roughly 180 days after concrete is poured, and in concrete using ordinary Portland cement, it is 400 to 800 × 10 -6 In contrast, concrete using blast-furnace cement type C has a -6 It becomes.

[0018] The procedure for constructing the precast concrete structure 1 will be described below with reference to the flow chart of FIG. In step S1, a formwork 30 for the precast concrete members 10, 20 is prepared in a factory, and a partition plate 31 is attached inside this formwork 30. A truncated cone-shaped burred portion 32 is formed in the partition plate 31 by burring. In this state, as shown in Figure 5 (a), concrete is poured simultaneously on both sides of the partition plate 31 inside the formwork 30 to produce the precast concrete members 10, 20, and the burred portion 32 of the partition plate 31 forms the convex portion 14 and the concave portion 24.

[0019] In step S2, as shown in Fig. 5(b), the formwork 30 and the partition plate 31 are removed. In this way, the precast concrete members 10, 20 are manufactured. In step S3, as shown in Fig. 6(a), the precast concrete members 10, 20 are transported to a construction site, and the precast concrete members 10, 20 are erected at attachment locations at the construction site, and joined together without filling the spaces between them with grout material. Fine joints 17 are formed at the joint surfaces. As a result, a precast concrete structure 1 is constructed, as shown in Fig. 6(b).

[0020] According to this embodiment, the following effects are obtained. (1) The precast concrete members 10, 20 are not joined together by filling them with grout material or by using joining keys made of joining metal fittings or by using mechanical joints to connect the rebars embedded in the precast concrete members, but by fitting together the convex portions 14 and concave portions 24 on the joining surfaces 11, 21 of the precast concrete members 10, 20. Therefore, the precast concrete members 10, 20 can be integrated together using a relatively simple joining method. In addition, since no joint keys or reinforcing bars are embedded in the joint surfaces of the precast concrete members 10, 20, the tensile stress that occurs around the highly rigid joint keys and reinforcing bars can be suppressed, and the occurrence of cracks due to tensile stress can be suppressed.

[0021] (2) Type C blast furnace cement was used as the binder for the precast concrete members 10 and 20. Therefore, carbon dioxide emissions can be reduced in proportion to the amount of ordinary Portland cement used during the production of the precast concrete members, contributing to improving the global environment. (3) In environmentally friendly concrete and high-strength concrete in which 40% or more of ordinary Portland cement has been replaced with ground granulated blast furnace slag, autogenous shrinkage increases, so that if joint keys or mechanical joints are used to join precast concrete components, there is a high possibility of cracks occurring. Therefore, in the present invention, when manufacturing precast concrete members 10, 20, convex portions 14 and concave portions 24 are formed by the burring portion 32 of the partition plate 31, and the precast concrete members 10, 20 are joined by fitting these convex portions 14 and concave portions 24 together.As a result, there is no need to embed joint keys or mechanical joints in the precast concrete members 10, 20, and cracks that occur in the precast concrete members 10, 20 can be suppressed.

[0022] (4) Because the precast concrete members 10, 20 are manufactured simultaneously using the formwork 30 and the partition plate 31, when joining the precast concrete members 10, 20 on-site, it is easy to ensure the positional accuracy of the precast concrete members 10, 20, and fine joints 17 can be realized between the joining surfaces 11, 21. In other words, the precast concrete members 10, 20 can be joined while taking into account any warping that occurs.

[0023] Second Embodiment Fig. 7 is a longitudinal sectional view of a precast concrete structure 1A according to a second embodiment of the present invention. Fig. 8 is a longitudinal sectional view of a first precast concrete member 10A and a second precast concrete member 20A constituting the precast concrete structure 1A. Fig. 9 is a CC sectional view of the precast concrete members 10A and 20A in Fig. 8. Fig. 10 is an enlarged view of a portion surrounded by a dashed line D of the precast concrete members 10A and 20A in Fig. 8. This embodiment differs from the first embodiment in that precast concrete members 10A, 20A are fastened and pressure-joined to each other by PC steel members 40 to which tension has been applied.

[0024] The first precast concrete member 10A has a plurality of through holes 15 extending horizontally at predetermined intervals in the vertical direction. These through holes 15 are formed by embedding polyethylene or polypropylene sheath pipes 16 in the concrete body of the first precast concrete member 10A. Furthermore, the convex portions 14 of the first precast concrete member 10A are located between the through holes 15, so that the through holes 15 are arranged around the convex portions 14. The dimension from the center of the convex portions 14 to the center of the through holes 15 is, for example, 325 mm.

[0025] The second precast concrete member 20A has a plurality of through holes 25 extending horizontally at predetermined intervals in the vertical direction. The through holes 25 are formed by embedding polyethylene or polypropylene sheath pipes 26 in the concrete body of the second precast concrete member 20A. Further, the recesses 24 of the second precast concrete member 20A are located between the through holes 25, so that the through holes 25 are arranged around the recesses 24.

[0026] The through hole 15 of the first precast concrete member 10A and the through hole 25 of the second precast concrete member 20A are in communication with each other. PC steel members 40 are inserted through the through holes 15, 25. Tension is applied to the PC steel members 40, and in this state, both ends of the PC steel members 40 are engaged with the precast concrete members 10A, 20A by anchoring plates 41 and nuts 42. As a result, the first precast concrete member 10A and the second precast concrete member 20A are pressure-joined via the PC steel members 40, and a fine joint 27 is formed between the joint surface 11 of the first precast concrete member 10A and the joint surface 21 of the second precast concrete member 20A.

[0027] According to this embodiment, in addition to the above-mentioned (1) to (4), the following effects are obtained. (5) The convex portions 14 and concave portions 24 on the joint surfaces 11 and 21 of the precast concrete members 10A and 20A are fitted together, and these joint surfaces 11 and 21 are pressed together by the tension introduced into the PC steel 40, thereby making it possible to more firmly integrate the precast concrete members 10A and 20A. Furthermore, since the through holes 15, 25 are formed using a sheath tube 16 made of polyethylene or polypropylene, which has lower rigidity than a steel sheath tube, the tensile stress generated around the sheath tube 16 can be suppressed, and the occurrence of cracks due to the tensile stress can be suppressed.

[0028] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention. For example, in each of the above-described embodiments, the convex portion 14 is shaped like a truncated cone, and the concave portion 24 is shaped so that the truncated cone-shaped convex portion 14 fits into it. However, this is not limited to this, and the convex portion may be shaped like a truncated pyramid, and the concave portion 24 may be shaped so that the truncated pyramid-shaped convex portion 14 fits into it. In each of the above-described embodiments, the precast concrete members 10, 20 are formed from concrete using blast-furnace cement type C, but this is not limiting and the precast concrete members 10, 20 may be formed from concrete using only ordinary Portland cement. Furthermore, at least a portion of the fine aggregate and / or coarse aggregate of the concrete forming the precast concrete members 10, 20 may be blast furnace slag aggregate. [Explanation of symbols]

[0029] 1, 1A…Precast concrete structure 2…Ground surface 10, 10A…First precast concrete member 11: Joint surface; 12: Base portion; 13: Wall portion; 14: Convex portion; 15: Through hole 16...Sheath pipe 17...Fine joint 20, 20A…Second precast concrete member 21: Joint surface; 22: Base portion; 23: Wall portion; 24: Recess portion; 25: Through hole 26...Sheath pipe 27...Fine joint 30: Formwork; 31: Partition plate; 32: Burring section 40...PC steel 41...Anchoring plate 42...Nut

Claims

1. A precast concrete structure constructed by joining a first precast concrete member and a second precast concrete member at a joint surface, The joint surface of the first precast concrete member is provided with a convex portion having a truncated pyramid shape or a truncated cone shape, A precast concrete structure characterized in that a recess is provided on the joint surface of the second precast concrete member into which the protrusion fits.

2. 2. The precast concrete structure according to claim 1, wherein the binder used in the first precast concrete member and the second precast concrete member is one in which 40% or more of ordinary Portland cement has been replaced with ground granulated blast furnace slag.

3. The first precast concrete member and the second precast concrete member have through holes formed around the convex portion and the concave portion, the through holes communicating with each other, A steel material is inserted into the through hole to introduce tension, 3. The precast concrete structure according to claim 1, wherein the through hole is formed by a sheath tube made of polyethylene or polypropylene.

Images