JP7628905B2 - Column-beam joint method and column-beam joint structure - Google Patents

Description

The present invention relates to a method for joining columns and beams in a precast concrete structure and a structure for joining columns and beams in a precast concrete structure.

Prestressed concrete structures are known as structures with higher elastic strength than RC structures (Patent Document 1). In these prestressed concrete structures, a large number of precast concrete columns with integrally molded girder support jaws are erected on a concrete foundation, and precast concrete girders with protrusions at their ends are supported by the girder support jaws and erected between each of the columns. Filler is provided at the joint between the girder support jaws and the protrusions, and the prestressed precast concrete girders are tensioned and fixed to the precast concrete columns by tensioning the PC steel wires.

A method using multiple unbonded precast prestressed concrete columns is also known as a building construction method that can shorten the construction period (Patent Document 2). In this method, a predetermined story is constructed on the core of a building that includes multiple unbonded precast prestressed concrete columns, and then a predetermined story is constructed on the outer periphery of the building.

Japanese Patent Application Publication No. 5-280092 JP 2020-56165 A

However, in the prestressed concrete structure described in Patent Document 1, the girder support jaws are integrally formed with the precast concrete columns so that they protrude from the outer surface of the column. The ends of the precast concrete beams are formed with recesses for receiving the girder support jaws, giving them a protruding shape. When the girder support jaws are formed protrudingly on the precast concrete columns in this way, the freedom of construction is limited. In addition, because the girder support jaws and protrusions are integrally formed with the columns and girder, the manufacturing costs of these precast concrete members are high. In addition, because the precast concrete columns are bulky due to the integral formation of the girder support jaws, the transportation costs are also high.

On the other hand, in the building construction method described in Patent Document 2, the columns in the core section are constructed as unbonded precast prestressed concrete columns, but the beams in the core section are reinforced concrete beams. Therefore, there is room for improvement in terms of increasing the freedom of construction and reducing costs. Paragraph [0022] of Patent Document 2 discloses that the beams in the core section may be unbonded precast prestressed concrete beams, precast prestressed concrete beams, etc., but does not disclose the specific configuration of the column-beam joints or the specific construction method for the columns and beams.

In view of the above background, the present invention aims to improve the flexibility of construction in precast concrete structures and reduce costs.

In order to solve the above problem, one aspect of the present invention is a method for joining columns and beams in a precast concrete structure, comprising the steps of erecting a precast column member (12) having a concave-shaped column-side shear key (21) at a predetermined position (FIG. 5(A)), attaching a removable temporary support member (23) to the precast column member (FIG. 5(A)), and placing an end of a precast beam member (13) having a concave-shaped beam-side shear key (20) on its end face on the temporary support member, and attaching the column-side shear key and the beam-side shear key to the precast column member (FIG. 5(A)). The method includes a step of opposing the precast beam member and the precast column member (FIG. 5(B)), a step of filling the gap (G) formed between the precast beam member and the precast column member with a filler (14) (FIG. 5(C)), a step of arranging a tension member (15) so as to span the precast beam member and the precast column member (FIG. 5(D)), and a step of applying tension to the tension member after the filler has hardened to introduce prestress into the precast beam member and the precast column member (FIG. 5(D)).

According to this embodiment, since the column side shear key and the beam side shear key are concave, the precast beam members can be positioned from both above and horizontally, and the freedom of construction is not limited. In addition, since a removable temporary support member can be attached to the precast column member and the end of the precast beam member can be placed on the temporary support member, construction is easy. Furthermore, since the column side shear key and the beam side shear key are concave, the manufacturing costs and transportation costs of the precast members can be reduced compared to when protrusions are formed on the precast column members and the precast beam members.

In the above embodiment, the method may further include a step of removing the temporary support member after the tension is applied to the tension member (FIG. 5(E)).

According to this aspect, the temporary support members can be reused, which reduces material costs. In addition, removing the temporary support members improves the appearance of the column-beam joint. When covering the column-beam joint with a board or the like, removing the temporary support members can reduce dead space.

In order to solve the above problem, another aspect of the present invention is a precast concrete beam-column joint structure (11), which includes a precast column member (12) erected at a predetermined position and having a concave column-side shear key (21) on its outer surface, a precast beam member (13) having a concave beam-side shear key (20) on its end surface and arranged so that the beam-side shear key faces the column-side shear key, a filler (14) filled in a gap (G) formed between the precast beam member and the precast column member, and a tension member (15) arranged to span the precast beam member and the precast column member and introduce prestress into the precast beam member and the precast column member.

According to this embodiment, the column side shear key and the beam side shear key are concave, so the freedom of construction when constructing a column-beam joint structure is not limited. In addition, because the column side shear key and the beam side shear key are concave, the manufacturing and transportation costs of the precast members can be reduced compared to when protrusions are formed on the precast column members and precast beam members.

In the above embodiment, a retaining member (22) may be provided in the lower portion of the precast beam member in the precast column member to detachably hold a temporary support member (23) for temporarily supporting the precast beam member.

According to this aspect, the temporary support member for temporarily supporting the precast beam member can be attached to the precast column member, and the end of the precast beam member can be placed on the temporary support member, making construction easy.

In the above aspect, the precast beam member has a beam side through hole (18) extending in the longitudinal direction to insert the tension member, and the precast column member has a column side through hole (19) extending in the horizontal direction at a position aligned with the beam side through hole, the beam side through hole and the column side through hole are partitioned by the gap and communicate with each other, and the tension member is inserted into the beam side through hole and the column side through hole, and the precast beam member and the precast column member may be in an unbonded state.

According to this embodiment, the column-beam joint is an unbonded prestressed concrete structure. Therefore, the elastic deformation performance of the column-beam joint structure can be improved compared to the case of a bonded structure. In addition, since the precast beam member and the precast column member can be separated by removing the tension member, the precast members can be reused, and the life cycle cost of the column-beam joint structure can be reduced. Furthermore, by reusing the precast members, the environmental load such as _CO2 emissions can be reduced compared to the case of constructing new members.

In the above embodiment, the column side shear key and the beam side shear key may have upper surfaces (20a, 21a) that become lower toward the back in the vertical section.

This aspect prevents air pockets from forming in the gap when filling the gap with the filler.

In the above embodiment, the column side shear key and the beam side shear key may have a pair of side surfaces (20b, 21b) that widen toward the back in plan cross section.

According to this embodiment, the column side shear key and the beam side shear key become dovetails, and the bonding force of the filler to the precast beam member and the precast column member is strong. Therefore, even if the tension material breaks and the connection by the tension force is released, the precast beam member is prevented from falling from the precast column member.

In the above embodiment, the filler may be non-shrink mortar, fiber-reinforced mortar, or low-elasticity, high-toughness mortar.

According to this aspect, the filler is less likely to break, improving the bonding strength of the precast beam member to the precast column member.

The above aspects improve the flexibility of construction in precast concrete structures and reduce costs.

Front view of the building according to the first embodiment Elevation section of the building shown in Figure 1 Enlarged view of the main part of Figure 2 A cross-sectional view taken along the line IV-IV in Figure 3. FIG. 1 is a diagram showing a procedure for constructing a building according to the first embodiment; Front view of a column-beam joint structure according to a second embodiment

The following describes an embodiment of the present invention with reference to the drawings. The present invention is applied to a building 1 with a rigid-frame structure made of reinforced concrete or steel-reinforced concrete.

First Embodiment
First, a first embodiment of the present invention will be described with reference to Figs. 1 to 5. Fig. 1 is a front view of a building 1 according to the first embodiment. As shown in Fig. 1, the building 1 includes a pair of columns 2 and a beam 3 whose both ends in the extension direction are joined to the pair of columns 2. The columns 2 are arranged at predetermined positions at a predetermined interval in the X direction and the Y direction which are orthogonal to each other in a plan view. The columns 2 may be provided in three or more rows in at least one of the X direction and the Y direction. The beams 3 are provided so as to extend in each of the X direction and the Y direction. In addition, the beams 3 are provided at predetermined positions in the vertical direction for each story of the building 1, and support floors (not shown). The ends of the beams 3 are joined to the columns 2 by a column-beam joint structure 11.

The column 2 includes at least one precast column member 12. The precast column member 12 is erected at a predetermined position, such as on a lower column or foundation constructed below. The precast column member 12 may be the same length as the floor height of one story, or may be longer than the floor height of one story. Alternatively, the precast column member 12 may be shorter than the floor height of one story. The precast column member 12 is preferably joined to the lower lower column or foundation below by an unbonded tendon.

The beam 3 is composed of one precast beam member 13. The precast beam member 13 has a length slightly shorter than the distance between a pair of precast column members 12. The precast beam member 13 is placed between a pair of precast column members 12. Therefore, a gap G (see FIG. 5(B)) is formed between the end of the precast beam member 13 and the opposing precast column member 12. This gap G is filled with a filler material 14. After filling with the filler material 14, the precast beam member 13 has both ends joined to a pair of precast column members 12 and is spanned across the pair of precast column members 12.

The precast column members 12 and the precast beam members 13 are fabricated in advance in a factory using precast concrete and transported to the construction site. The filler 14 is a fluid material that hardens over time, and may be, for example, mortar or cement milk. It is preferable to use fiber-reinforced mortar or low-elasticity, high-toughness mortar as the filler 14 so that the filler 14 is less likely to break after hardening.

In this way, the beam-column joint structure 11 is a joint structure between one end of a precast beam member 13 and a precast column member 12, and is configured at both ends of the precast beam member 13. In this embodiment, each end of the precast beam member 13 is pressure-joined to the corresponding precast column member 12 by a tension member 15 arranged to span from one precast column member 12 to the other precast column member 12. This makes the beam-column joint structure 11 a prestressed concrete structure.

Specifically, multiple tendons 15 are arranged on the upper and lower parts of the precast beam member 13. Both ends of each tendon 15 are fixed to the outer surface of the outside of the precast column member 12 by fasteners 16 while tension is applied. This introduces prestress to the precast column member 12 and the precast beam member 13, and each end of the precast beam member 13 is crimped to the corresponding precast column member 12.

The tension members 15 are made of PC steel rods, PC steel wires, PC steel strands, or rods or cables made of fiber-reinforced plastic such as aramid fiber, carbon fiber, or glass fiber. It is preferable that the tension members 15 are unbonded tension members that are not bonded to the precast column members 12 and the precast beam members 13. By making the tension members 15 unbonded, residual deformation after the end of an earthquake is reduced.

Figure 2 is an elevational cross-sectional view of the building 1 shown in Figure 1. As shown in Figure 2, the precast beam member 13 has a beam-side through hole 18 for inserting the tendon 15. The beam-side through hole 18 extends horizontally along the longitudinal direction of the precast beam member 13. The precast column member 12 has a column-side through hole 19 for insertion. The column-side through hole 19 extends horizontally at a position aligned with the beam-side through hole 18 and is continuous with the beam-side through hole 18.

A concave beam side shear key 20 is formed on both end faces of the precast beam member 13. A concave column side shear key 21 is formed in a position opposite the beam side shear key 20 on the inner outer surface of the precast column member 12.

Figure 3 is an enlarged view of the main part of Figure 2. As shown in Figure 3, a plurality of embedded anchors 22 are provided in the portion of the precast column member 12 below the precast beam member 13. The embedded anchors 22 have threaded holes opened on the outer surface of the precast column member 12 below the precast beam member 13. The embedded anchors 22 are holding members that cooperate with bolts B that screw into the threaded holes to detachably hold the brackets 23.

The bracket 23 is a temporary support member for temporarily supporting the precast beam member 13 when joining it to the precast column member 12. The bracket 23 may be made of shaped steel such as an angle steel, a channel steel, or an H-shaped steel. The bracket 23 may be attached before erecting the precast column member 12 and removed after joining the precast beam member 13.

This configuration allows the brackets 23 for temporarily supporting the precast beam members 13 to be attached to the precast column members 12, and the ends of the precast beam members 13 to be placed on the brackets 23, making construction easier.

As described above, the gap G (see FIG. 5B) formed between the end of the precast beam member 13 and the precast column member 12 is filled with the filler 14. In order to prevent the filler 14 from adhering to the tension member 15, an anti-adhesion material 24 is provided between the precast beam member 13 and the precast column member 12. The anti-adhesion material 24 has an annular shape and partitions the beam side through hole 18 and the column side through hole 19 from the gap G and communicates them. This prevents the filler 14 filled in the gap G from flowing into the beam side through hole 18 and the column side through hole 19. The anti-adhesion material 24 may be an elastic member disposed in a compressed state between the precast beam member 13 and the precast column member 12. In another embodiment, the anti-adhesion material 24 may be a cylindrical member disposed across the gap G and inserted into the beam side through hole 18 and the column side through hole 19.

By providing the adhesion prevention material 24 and putting the tendons 15 in an unbonded state, the column-beam joint becomes an unbonded prestressed concrete structure. This improves the elastic deformation performance of the column-beam joint structure 11 compared to a bonded structure. In addition, the precast beam members 13 and the precast column members 12 can be separated by removing the tendons 15. This makes it possible to reuse these precast members, thereby reducing the life cycle cost of the column-beam joint structure 11. Furthermore, by reusing the precast members, environmental impacts such as _CO2 emissions are reduced compared to constructing new members.

In the vertical cross section of FIG. 3, the upper surface 20a of the beam-side shear key 20 becomes lower from the gap G side toward the back. The upper surface 21a of the column-side shear key 21 also becomes lower from the gap G side toward the back. Therefore, air pockets are prevented from forming in the gap G when the filler 14 is filled into the gap G. In the vertical cross section of FIG. 3, the bottom surfaces of the beam-side shear key 20 and the column-side shear key 21 become higher from the gap G side toward the back.

Figure 4 is a plan cross-sectional view taken along the IV-IV cross-sectional line in Figure 3. As shown in Figure 4, in plan cross-section, the beam-side shear key 20 has a pair of side surfaces 20b that diverge toward the back. The column-side shear key 21 also has a pair of side surfaces 21b that diverge toward the back. This makes the beam-side shear key 20 and the column-side shear key 21 into dovetail tenons, strengthening the bonding force of the filler 14 to the precast beam member 13 and the precast column member 12. Therefore, even if the tension member 15 breaks and the connection caused by the tension force is released, the precast beam member 13 is prevented from falling from the precast column member 12.

In this embodiment, fiber-reinforced mortar, which is less likely to break, is used as the filler 14. This improves the bonding strength of the precast beam member 13 to the precast column member 12. In other embodiments, non-shrink mortar or low-elasticity, high-toughness mortar may be used as the filler 14 instead of the fiber-reinforced mortar. This also improves the bonding strength of the precast beam member 13 to the precast column member 12.

The beam-column joint structure 11 of the building 1 is constructed as described above. Next, a method for joining beams and columns in such a precast concrete structure will be described. Figure 5 is a diagram showing the construction procedure for the building 1 according to the first embodiment. The building 1 is constructed by workers through the following steps.

Prior to constructing the building 1, the required number of precast column members 12 and precast beam members 13 with the above configuration are prepared. As described above, the precast column members 12 have a concave column side shear key 21 formed therein, but no protrusions such as beam support jaws are formed therein. Therefore, the precast column members 12 are not bulky, and transportation costs can be reduced. In addition, the precast beam members 13 have a concave beam side shear key 20 formed therein, but no protrusions at their ends are formed to rest on the beam support jaws. In this way, no protrusions are formed on the precast column members 12 and precast beam members 13, and therefore the manufacturing costs of these precast concrete members can be reduced.

At the construction site of the building 1, the precast column member 12 is erected in a predetermined position as shown in FIG. 5(A). The bracket 23 may be attached to the precast column member 12 before the precast column member 12 is erected. Alternatively, the bracket 23 may be attached to the precast column member 12 after the precast column member 12 is erected in a predetermined position.

Next, as shown in FIG. 5(B), the precast beam member 13 is lifted by a crane (not shown) and placed between a pair of precast column members 12, and both ends of the precast beam member 13 are placed on the brackets 23. At this time, since the column side shear key 21 and the beam side shear key 20 are concave, the precast beam member 13 can be placed from both above and horizontally, and the freedom of construction is not restricted. In addition, the bracket 23 for temporarily supporting the precast beam member 13 is detachably attached to the precast column member 12, which improves the freedom of construction. In addition, since the bracket 23 is attached to the precast column member 12, the end of the precast beam member 13 can be placed on the bracket 23. This makes construction easy.

When the precast beam member 13 is placed in a predetermined position on the bracket 23, the beam side shear key 20 and the column side shear key 21 face each other. Although not shown in Figure 5, when the precast beam member 13 is placed in a predetermined position, an anti-adhesion material 24 (see Figure 3) is placed in a predetermined position.

Then, as shown in FIG. 5(C), filler 14 is filled into the gap G formed between the precast beam member 13 and the precast column member 12. As shown in FIG. 5(D), tensioning members 15 are placed across the precast beam member 13 and the precast column member. After the filler 14 has hardened, tension is applied to the tensioning members 15 to introduce prestress into the precast beam member 13 and the precast column member 12. This results in the construction of a prestressed concrete beam-column joint structure 11. Note that the tensioning members 15 may be placed before filling with the filler 14 in FIG. 5(C).

Then, as shown in FIG. 5(E), the bracket 23 is removed. By removing the bracket 23 after joining the precast beam members 13, it can be reused for other joints. This reduces material costs. Furthermore, removing the bracket 23 improves the appearance of the column-beam joint. If the column-beam joint is to be covered with a board or the like, removing the bracket 23 can reduce the dead space.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to Fig. 6. As shown in Fig. 6, this embodiment differs from the first embodiment in that both ends of a precast beam member 13 are joined to a pair of precast column members 12 by pressure bonding with discontinuous tendons 15. This will be described in detail below.

The precast beam member 13 has beam widening sections 31 at both ends that are wider than the middle section in the longitudinal direction. The beam widening sections 31 form shoulder surfaces 31a that engage the fasteners 16 on the side opposite the end faces of the precast beam member 13. The shoulder surfaces 31a are formed on both sides in the width direction in the cross section of the precast beam member 13.

Even if the precast beam member 13 is configured in this manner and both ends of the precast beam member 13 are crimped to the precast column member 12 by discontinuous, independent tension members 15, the same effect as in the first embodiment can be achieved.

Although the description of the specific embodiment is now complete, the present invention is not limited to the above embodiment and can be modified in a wide range of ways. For example, the specific configuration and arrangement of each member or part, the quantity, materials, procedures, etc. can be changed as appropriate without departing from the spirit of the present invention. On the other hand, not all of the components shown in the above embodiment are necessarily required and can be selected as appropriate.

11: Column-beam joint structure 12: Precast column member 13: Precast beam member 14: Filler material 15: Tendon 18: Beam-side through hole 19: Column-side through hole 20: Beam-side shear key 20a: Top surface 20b: Side surface 21: Column-side shear key 21a: Top surface 21b: Side surface 22: Embedded anchor (retaining member)
23: Bracket (temporary support member)
G: gap

Claims (6)

A method for joining columns and beams in a precast concrete structure, comprising the steps of:
A step of erecting a precast column member having a concave column side shear key at a predetermined position;
attaching a removable temporary support member to the precast column member;
placing an end of a precast beam member having a concave beam side shear key on an end surface thereof on the temporary support member, and arranging the column side shear key and the beam side shear key opposite each other;
filling a gap formed between the precast beam member and the precast column member with a filler material;
placing tendons across the precast beam members and the precast column members;
and after the filler has hardened, applying tension to the tendons to prestress the precast beam members and the precast column members ;
The column-beam joining method, wherein the column-side shear key and the beam-side shear key have an upper surface that is lower toward the back in a vertical cross section, and a pair of side surfaces have a shape that widens toward the back in a horizontal cross section. The beam-column joining method according to claim 1, further comprising a step of removing the temporary support member after the tension is applied to the tendon. A precast concrete beam-column joint structure,
A precast column member that is erected at a predetermined position and has a concave column side shear key on an outer surface;
A precast beam member having a concave beam side shear key at an end surface, the beam side shear key being arranged to face the column side shear key;
A filler material filled in a gap formed between the precast beam member and the precast column member;
a tendon arranged across the precast beam member and the precast column member to introduce prestress into the precast beam member and the precast column member ;
The column-side shear key and the beam-side shear key have an upper surface that is lower toward the back in a vertical cross section, and a pair of side surfaces that widen toward the back in a horizontal cross section. This is a column- beam joint structure. The beam-column joint structure according to claim 3, wherein a retaining member is provided in the lower portion of the precast beam member in the precast column member, for removably holding a temporary support member for temporarily supporting the precast beam member. a beam-side through hole extending in a longitudinal direction for inserting the tension member is formed in the precast beam member, a column-side through hole extending in a horizontal direction at a position aligned with the beam-side through hole is formed in the precast column member, the beam-side through hole and the column-side through hole are partitioned by the gap and communicate with each other,
A column-beam joint structure as described in claim 3 or claim 4, wherein the tension member is inserted into the beam side through hole and the column side through hole, and is in an unbonded state with respect to the precast beam member and the precast column member. The column-beam joint structure according to any one of claims 3 to 5 , wherein the filler is a non-shrink mortar, a fiber-reinforced mortar or a low-elasticity, high-toughness mortar.

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