JP7162338B2 - Joining structure and joining method of precast member - Google Patents

Description

TECHNICAL FIELD The present invention relates to a joining structure and joining method for precast members. Precast concrete is simply called precast. Moreover, prestressed concrete is described as PC.

Underground structures such as box culverts have been thought to be less susceptible to earthquakes because they behave together with the surrounding ground during an earthquake. In fact, damage to box culverts by the earthquake was small. However, in recent years, the size of box culverts has been increasing beyond the scope of application of conventional culverts. In addition, the national policy (i-Construction: an initiative to improve the productivity of the entire construction production system by introducing measures such as the full use of ICT (information and communication technology) at the construction site) will improve productivity. Precasting of box culverts for the purpose is progressing. In this way, the seismic resistance of box culverts, which have become larger and precast, is currently unclear.

For convenience in transportation, a large precast product must be manufactured by dividing it into a plurality of precast members, transported to a construction site, and assembled by joining the precast members at the construction site. For example, FIG. 6 shows a box culvert 51 consisting of two upper L-shaped members 52, 52, one top intermediate member 53, two lower L-shaped members 54, 54, and one bottom intermediate member 55. 4 shows an example of division into body precast members. There are mainly the following two types of joining methods for precast members, excluding joining accompanied by placing cast-in-place concrete.

(1) PC joining by pressure welding between precast members with tensioned PC steel material that penetrates a plurality of precast members (for example, Patent Document 1).

(2) Joining by a mortar-filled joint in which the ends of both reinforcing bars embedded in adjacent precast members are fixed via mortar filled in a common sleeve (for example, Patent Document 2). FIG. 6 shows an example of joining with a mortar filling joint 60 .

In addition, in Patent Document 3, as a connection means for connecting the side wall portion and the top plate portion of the box culvert, in addition to the PC joint, a mortar-filled joint is also used to join. It is described that a highly reliable, high-strength connection structure is obtained.

JP 2007-315024 A JP-A-9-209334 JP 2009-191523 A

It has been found that when an underground structure made by PC-joining precast members receives a positive and negative alternating load such as during a large-scale earthquake, there is a high possibility that the joints will open. This is because in PC joining, a small number of PC steel materials are continuous between members, but a large number of reinforcing bars embedded in each precast member are not continuous between members.

Underground structures formed by joining precast members with mortar-filled joints do not cause such openings even in the event of a large-scale earthquake. This is because, in joining by a mortar-filled joint, a large number of reinforcing bars embedded in each precast member are connected between the members by the mortar-filled joint. Therefore, when assuming a large-scale earthquake, mortar-filled joints are becoming the mainstream method for joining precast members of underground structures.

However, joining by mortar-filled joints has the following problems.
It takes one day or more for the mortar to harden after filling. If a force such as a load is applied between the precast members during this hardening period, the mortar will flow and the sleeve and the reinforcing bars will be displaced relative to each other, resulting in displacement between the precast members.

In the box culvert example shown in FIG. 6, the top slab intermediate member 53 is a non-self supporting precast member with no load support from below. Therefore, in order to prevent the top plate portion intermediate member 53 from being displaced downward due to the load during the curing period, it is necessary to temporarily support the load from below on the top plate portion intermediate member 53 .

For example, FIG. 6A shows an example of using a table 71 as a load support. The top slab intermediate member 53 supported by a base 71 temporarily installed on the ground and the upper L-shaped members 52, 52 placed on the ground are joined by a mortar filling joint 60, while the lower L-shaped members 54, 54 placed on the ground are connected. After the 54 and the bottom intermediate member 55 are joined by the mortar filling joint 60 , the upper L-shaped member 52 and the lower L-shaped member 54 are joined by the mortar filling joint 60 .

FIG. 6(b) is an example of using a shoring 72 as a load support. The top slab intermediate member 53 is supported by a shoring 72 temporarily installed on the bottom slab intermediate member 55 , and all precast members ( 52 , 52 , 53 , 54 , 54 , 55 ) are joined by mortar filling joints 60 .

Due to these problems (period and temporary construction cost), joining by mortar filling joints cannot be applied to the divided top slabs, and has been mainly applied to the divided side walls.

Even if the combined use of the PC joint of Patent Document 3 and the joint by the mortar filling joint is applied to the divided top slab, the above-mentioned problem cannot be solved because the above-mentioned load support is required temporarily.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to enable precast members to be joined in a short period of time without having to temporarily install a load bearing, and to prevent precast products after joining from opening at joints during large-scale earthquakes. be.

(1) Joining structure of precast members In the joining structure of at least two precast members connected in series,
The at least two precast members are pressure-welded between the precast members by tensioned PC steel material penetrating all the precast members, and through mortar filled in a common sleeve with the ends of both reinforcing bars embedded in the adjacent precast members. is joined by a mortar filling joint fixed by a
The shear key is a concrete trapezoidal convex shear key formed on one of the two end faces of the adjacent precast members, and a concrete trapezoidal concave shear key formed on the other end face. is a composite structure, a concrete shear key ,
The PC steel material penetrates the trapezoidal convex shear key and the trapezoidal concave shear key .

(2) Joining structure of precast members In the joining structure of at least three precast members connected in series,
at least one precast member in the intermediate part in the series direction is a non-self-supporting precast member without load support from below;
The at least three precast members are pressure-welded between the precast members by tensioned PC steel materials penetrating all the precast members, and through mortar filled in a common sleeve with the ends of both reinforcing bars embedded in the adjacent precast members. is joined by a mortar filling joint fixed by a
The shear key is a concrete trapezoidal convex shear key formed on one of the two end faces of the adjacent precast members, and a concrete trapezoidal concave shear key formed on the other end face. is a composite structure, a concrete shear key,
The PC steel material penetrates the trapezoidal convex shear key and the trapezoidal concave shear key .

(3) Method for joining precast members In a method for joining at least three precast members connected in series,
at least one precast member in the intermediate part in the series direction is a non-self-supporting precast member without load support from below;
The at least three precast members are pressure-welded between the precast members by tensioned PC steel material penetrating through all the precast members and embedded in the adjacent precast members without temporarily supporting the load from below on the non-self-supporting precast members. mortar-filled joints, in which the ends of both reinforcing bars are fixed via mortar filled in a common sleeve, and shear keys provided on both end faces of adjacent precast members ;
The shear key is fitted between a concrete trapezoidal convex shear key formed on one end face and a concrete trapezoidal concave shear key formed on the other end face of the adjacent precast members. be a concrete shear key, which is a composite structure; and
The PC steel material penetrates the trapezoidal convex shear key and the trapezoidal concave shear key .

[Action]
In the following, the pressure welding of precast members made of PC steel will be referred to as "PC bonding".
(a) PC joints and shear keys prevent misalignment between precast members during curing of mortar-filled joints. Therefore, even when joining the divided top slabs, load support such as shoring is not required, and construction can be completed in a short period of time.

(a) By considering both mortar-filled joints and PC joints in the structural design during service, it is possible to combine the toughness of mortar-filled joints with the weight reduction and high durability of PC joints. That is, the mortar-filled joint ensures the continuity of the reinforcing bars, ensuring the toughness of the joints and preventing the joints from opening during an earthquake. The anti-slip function of the shear key works not only during construction, but also after construction, and even during an earthquake. In addition, since prestress is introduced into the precast member by the PC steel material, the precast member can be designed to be lightweight, and the precast member has crack recovery properties, resulting in a highly durable structure.

(c) In addition, the top slab can be divided, for example, in a box culvert, and a large internal space width can be constructed.

According to the present invention, precast members can be joined in a short period of time without temporarily installing a load bearing, and the precast product after joining has both the toughness of the mortar-filled joint and the weight reduction and high durability of the PC joint. It has the excellent effect of not opening the joints in the event of a large-scale earthquake.

FIG. 1 is an exploded front view of a precast member constituting the box culvert of the embodiment. FIG. 2 shows the same precast member, (a) is a side view of the upper L-shaped member, (b) is a side view of the lower L-shaped member, (c) is a plan view of the upper L-shaped member, and (d) is a top view. FIG. 4 is a plan view of a plate unit intermediate member; FIG. 3 is an exploded perspective view of the precast member. FIG. 4 is a front view of a box culvert of an embodiment formed by joining the same precast members. FIG. 5 is an enlarged vertical cross-sectional view taken along the line A--A in FIG. Fig. 6 shows a conventional box culvert joining method. (a) is a front view showing a method of supporting the top slab intermediate member with a stand, and (b) is a method of supporting the top slab intermediate member with a shoring. It is a front view showing.

1. Precast Member A precast member is produced by dividing a precast product. Examples of precast products include, but are not limited to, box culverts, shed blocks, water channel blocks, and the like.

In particular, the present invention is suitable for box culverts, shed blocks, etc. having a top slab.
The at least three precast members in the means (2) and (3) are preferably produced by dividing the top plate of the box culvert.

2. Mortar-filled joints and PC joints There is no particular limitation on the burden ratio of mortar-filled joints and PC joints (mortar-filled joints: PC joints) in structural calculation. 5:5 to 7:3 is preferable, and 5.5:4.5 to 6 in terms of good balance and in terms of ensuring the number of PC steel materials required for PC joining of non-self-supporting precast members during construction. .5:3.5 is more preferred.
The number of mortar-filled joints, the strength of reinforcing bars, the number of PC joints, and the strength of PC steel materials can be appropriately determined according to the above-mentioned burden ratio.

3. Shear Key The shear key is not particularly limited in material, shape, size, number or position on the end surface of the precast member, etc., as long as it does not deviate from the above content. As the shear key, in addition to the above-mentioned concrete shear key, a steel shear key or the like can be exemplified as a reference example.
A steel shear key has a fitting structure in which a steel convex joint embedded in one of the two end faces of adjacent precast members and a steel concave joint embedded in the other end face. be.

Next, embodiments of the present invention will be described with reference to FIGS. 1 to 5. FIG. The structure, material, shape and dimensions of each part in the embodiment are examples, and can be changed as appropriate without departing from the gist of the invention.

The precast product of the example is a large box culvert 1 (for example, 3000 to 10000 mm in length and 4000 to 17000 mm in width). The design divides the sidewalls into upper and lower parts, respectively,
two upper L-shaped members 2, 2 forming the end of the top plate and the upper part of the side wall;
one top plate portion intermediate member 3 that constitutes only the intermediate portion of the top plate portion;
two lower L-shaped members 4, 4 forming the end portion of the bottom plate portion and the lower portion of the side wall portion;
It is manufactured by being divided into six precast members (2, 2, 3, 4, 4, 5) with one bottom plate portion intermediate member 5 constituting only the intermediate portion of the bottom plate portion.

Of the six precast members, the top intermediate member 3 is a non-self-sustaining precast member that does not support a load from below (when in use).

The two upper L-shaped members 2, 2 and the top plate intermediate member 3 are laterally connected in series,
The two lower L-shaped members 4, 4 and the bottom intermediate member 5 are laterally connected in series,
It can be seen that the upper L-shaped members 2, 2 and the lower L-shaped members 4, 4 are connected in series in the vertical direction.
These two or three precast members connected in series are respectively a PC joint 10 (pressure contact between precast members by PC steel materials 13 that are stretched through all precast members) and both reinforcing bars embedded in the adjacent precast members. 21 are joined together by a mortar-filled joint 20 fixed via mortar filled in a common sleeve 22 and shear keys 30 provided on both end faces of adjacent precast members. The ratio of the burden of the mortar filling joint 20 and the PC joint 10 in the structural calculation (mortar filling joint 20:PC joint) is, for example, about 6:4.

[PC bonding 10]
The PC joints 10 are formed by sheaths 11 extending in the serial direction respectively embedded in two or three precast members connected in series and precast members at two ends in the serial direction corresponding to the ends of the sheaths 11. It is composed of a fixing plate 12, a continuous PC steel material 13 passing through the sheath 11, and a tightening tool 14 that tightens the PC steel material 13 to the fixing plate 12 to tighten it.

As the PC steel material 13, FIG. 3 and the like show one from the beginning (not joined in the middle), but a plurality of pieces may be joined with a coupler (not shown) to form a single piece. In particular, it is preferable that the PC steel material 13 joining the upper L-shaped member 2 and the lower L-shaped member 4, which are connected in series in the vertical direction, is made into one piece by joining two pieces with a coupler. Since it is difficult to fasten the lower L-shaped member 4 through the PC steel material 13 with the fasteners 14 after it is placed on the ground, a half length of the PC steel material 13 is passed through the lower L-shaped member 4 in advance and the upper and lower ends of the lower L-shaped member 4 are tightened. This is for attaching the fitting 14 and the coupler.

[Mortar filling joint 20]
The mortar filling joint 20 includes both reinforcing bars 21 embedded in adjacent precast members, a common sleeve 22 embedded near the end face of one of the precast members, and the ends of both reinforcing bars 21 entering the sleeve 22. In this state, the gap between the reinforcing bars 21 in the sleeve 22 is filled with hardened mortar 23 . The mortar filling joint 20 will be further detailed.

In the upper L-shaped members 2, 2, a plurality of sleeves 22 are embedded near the outer peripheral surface and near the inner peripheral surface near the end surface on the top plate side and near the end surface on the side wall portion side, respectively. As shown in FIG. 5, the sleeve 22 has a mortar injection port 24 and a mortar discharge port 25 near both ends of the peripheral wall, and an uneven portion on the inner peripheral surface. The reinforcing bar 21 includes a rectangular portion 21a and a curved portion 21b in the middle and continues from near the end face on the side of the top slab to near the end face on the side of the side wall. Both ends of the reinforcing bar 21 enter an intermediate portion within the sleeve 22 . A deformed reinforcing bar having irregularities (nodes) on the outer peripheral surface is used as the reinforcing bar 21 . The uneven portion of the sleeve 22 and the uneven portion of the reinforcing bar 21 are joints that transmit force via hardened mortar 23 . A high-strength and non-shrinkage mortar is used for the mortar 23 .

In the lower L-shaped members 4, 4, a plurality of sleeves 22 are embedded near the outer peripheral surface and near the inner peripheral surface near the end surface on the bottom plate portion side. The reinforcing bar 21 includes a rectangular portion and a curved portion in the middle and is continuous from the vicinity of the end face on the side of the bottom slab to the end face on the side of the side wall. The lower end portion of the reinforcing bar 21 extends into the intermediate portion inside the sleeve 22 . The upper end portion of the reinforcing bar 21 protrudes from the end face on the side wall portion side, enters the middle portion in the sleeve 22 of the upper L-shaped members 2, 2, and is joined via the mortar 23. As shown in FIG. Others are the same as those of the upper L-shaped members 2,2.

In the top plate portion intermediate member 3, the reinforcing bars 21 are linearly continuous between both end surfaces of the same member. Both ends of the reinforcing bar 21 protrude from both end faces of the same member, enter the middle part in the sleeves 22 of the upper L-shaped members 2, 2, and are joined via mortar 23. As shown in FIG. Others are the same as those of the upper L-shaped members 2,2.

In the bottom slab intermediate member 5, the reinforcing bars 21 are linearly continuous between both end faces of the same member. Both ends of the reinforcing bar 21 protrude from both end faces of the same member, enter the middle part in the sleeves 22 of the lower L-shaped members 4, 4, and are joined via the mortar 23. As shown in FIG. Others are the same as those of the upper L-shaped members 2,2.

[Shear key 30]
The shear keys 30 are concrete shear keys in this embodiment, and consist of a convex shear key 31 formed on one end face and a concave shear key formed on the other end face of the adjacent precast members. 32 is a fitting structure.

Specifically, between the upper L-shaped members 2, 2 and the top plate portion intermediate member 3, a trapezoidal convex side shear key 31 is formed in the central portion of the end face of the upper L-shaped members 2, 2, and the top plate portion A trapezoidal concave shear key 32 is formed at the center of the end face of the intermediate member 3 .

Between the upper L-shaped members 2, 2 and the lower L-shaped members 4, 4, two trapezoidal convex side shear keys 31 are provided on the lower end surfaces of the upper L-shaped members 2, 2 near the front side and the rear side. are formed, and two trapezoidal concave side shear keys 32 are formed in the front and rear portions of the lower L-shaped members 4 and 4, respectively.

Between the lower L-shaped members 4, 4 and the bottom plate portion intermediate member 5, a trapezoidal convex side shear key 31 is formed in the central portion of the end faces of the lower L-shaped members 4, 4, and the end face of the bottom plate portion intermediate member 5 is formed. A trapezoidal concave shear key 32 is formed in the center of the.

The box culvert 1 of the embodiment configured as described above transports the precast members (2, 2, 3, 4, 4, 5) to the construction site, and joins the precast members at the construction site as follows. Assembled. It is well known that a plurality of box culverts 1 are connected in the lengthwise direction to form a waterway, a road, or the like.

(1) First, as shown in the change from FIG. 1 to FIG. 3 to FIG. The intermediate member 5, the upper L-shaped members 2, 2 and the lower L-shaped members 4, 4, and the two upper L-shaped members 2, 2 and the top plate intermediate member 3 are joined by PC joint 10 and the shear key 30 .

(2) Next, as shown in FIG. 5, the mortar 23 is injected into the sleeves 22 from the injection port 24 of each sleeve 22, and discharged from the discharge port 25 until it is slightly discharged to fill the sleeves 22. As shown in FIG. After that, the injection port 24 and the discharge port 25 are closed with a stopper 26 . During the injection and the subsequent hardening period, the top plate portion intermediate member 3 is not temporarily provided with a load support from below. When the mortar 23 hardens, joining by the mortar filling joint 20 is added to the above joining (1).

According to this embodiment, the following effects are obtained.
(a) The PC joint 10 and the shear key 30 prevent displacement between the precast members during the hardening period of the mortar-filled joint 20 . Therefore, even when joining the divided top slab intermediate members 3 that do not support the load from below (in the state of use), load support such as shoring is unnecessary, and construction can be completed in a short period of time.

(a) By considering both the mortar-filled joint 20 and the PC joint 10 in the structural design during use, it is possible to combine the toughness of the mortar-filled joint 20 with the weight reduction and high durability of the PC joint 10. That is, the continuity of the reinforcing bars 21 provided by the mortar-filled joint 20 ensures the toughness of the joint, preventing the joint from opening during an earthquake. The shear key 30 has a function of preventing displacement not only during construction, but also during construction and at all times, even during an earthquake. In addition, since prestress is introduced into the precast member by the PC steel material 13, the precast member can be designed to be lightweight, and the precast member has crack recovery properties, resulting in a highly durable structure.

(c) In addition, it is possible to divide the top slab in the box culvert 1, and to construct a large-span inner space.

It should be noted that the present invention is not limited to the above-described embodiments, and can be embodied with appropriate modifications without departing from the gist of the invention.

Reference Signs List 1 box culvert 2 upper L-shaped member 3 top plate intermediate member 3 patent document 4 lower L-shaped member 5 bottom plate intermediate member 10 PC joint 11 sheath 12 fixing plate 13 PC steel material 14 fastener 20 mortar filling joint 21 reinforcing bar 21a rectangle Part 21b Curved part 22 Sleeve 23 Mortar 24 Inlet 25 Outlet 26 Stopcock 30 Shear key 31 Convex shear key 32 Concave shear key

Claims (6)

In the joint structure of at least two precast members (2, 3) connected in series,
The at least two precast members are pressed between the precast members by tensioned PC steel material (13) penetrating all precast members, and the ends of both reinforcing bars (21) embedded in adjacent precast members are connected to a common sleeve ( 22) It is joined by a mortar filling joint (20) fixed via a mortar (23) filled inside and shear keys provided on both end faces of adjacent precast members,
The shear key comprises a concrete trapezoidal convex shear key (31) formed on one of the two end surfaces of the adjacent precast members, and a concrete trapezoidal concave shear key (31) formed on the other end surface. a concrete shear key (30) which is a mating structure with (32);
The precast member joining structure, wherein the PC steel material (13) penetrates the trapezoidal convex shear key (31) and the trapezoidal concave shear key (32) . In the joint structure of at least three precast members (2, 2, 3) connected in series,
at least one precast member (3) in the intermediate part in the series direction is a non-self-supporting precast member without load support from below;
The at least three precast members are pressure-welded between the precast members by tensioned PC steel material (13) penetrating all precast members, and connecting the ends of both reinforcing bars (21) embedded in adjacent precast members to a common sleeve ( 22) It is joined by a mortar filling joint (20) fixed via a mortar (23) filled inside and shear keys provided on both end faces of adjacent precast members,
The shear key comprises a concrete trapezoidal convex shear key (31) formed on one of the two end surfaces of the adjacent precast members, and a concrete trapezoidal concave shear key (31) formed on the other end surface. a concrete shear key (30) which is a mating structure with (32);
The precast member joining structure, wherein the PC steel material (13) penetrates the trapezoidal convex shear key (31) and the trapezoidal concave shear key (32) . A method for joining at least three precast members (2, 2, 3) in series,
at least one precast member (3) in the intermediate part in the series direction is a non-self-supporting precast member without load support from below;
Pressure welding between the at least three precast members by a PC steel material (13) tensioned through all the precast members in a state where the non-self-supporting precast member (3) is not temporarily provided with a load support from below; A mortar-filled joint (20) in which the ends of both reinforcing bars (21) embedded in adjacent precast members are fixed via a mortar (23) filled in a common sleeve (22), and both end faces of the adjacent precast members Joining with a shear key provided in
The shear key is a concrete trapezoidal convex shear key (31) formed on one of the two end faces of the adjacent precast members, and a concrete trapezoidal concave shear key (31) formed on the other end face. be a concrete shear key (30) that is a mating structure with (32) ; and
A method for joining precast members, wherein the PC steel material (13) penetrates the trapezoidal convex shear key (31) and the trapezoidal concave shear key (32) . The joining structure of precast members according to claim 1 or 2, wherein the precast members are produced by dividing a box culvert (1). 3. The joining structure of precast members according to claim 2, wherein the at least three precast members are manufactured by dividing the top plate of the box culvert (1). 4. The method of joining precast members according to claim 3, wherein the at least three precast members are produced by dividing the top plate of the box culvert (1).

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