JP5743824B2 - Laminated joint material, slit structure provided with laminated joint material, and construction method thereof - Google Patents

Description

  In the present invention, walls, pillars, beams, floors, etc. (hereinafter collectively referred to as “concrete structures”) constituting a concrete building typified by an apartment house are mutually referred to. The present invention relates to a joint material installed in an adjacent portion. More specifically, the present invention relates to a laminated joint material including two kinds of materials, a slit structure in which the laminated joint material is installed, and a method for constructing the slit structure.

  Japan is known as an earthquake-prone country. In recent years, major earthquakes such as the Tohoku-Pacific Ocean Earthquake, the Hyogoken-Nanbu Earthquake, and the Niigata-ken Chuetsu Earthquake have occurred and have suffered enormous damage each time. On the other hand, high-rise concrete buildings such as office buildings and condominiums have progressed, and as a result, earthquake countermeasures such as earthquake-resistant structures and seismic isolation structures have advanced.

  As one of the earthquake countermeasures for concrete buildings, a “hanging method” is known in which a wall is suspended by a ceiling slab. FIG. 11 is a front view showing a wall body constructed by this hanging method. As shown in this figure, the wall a is fixed only by the ceiling slab b, and the discontinuous structure is provided by providing a slit e which is a narrow gap between the floor slab c on the lower end side and the pillars d on both sides. (So-called “border cutting”). Thus, since the wall body a and the surrounding concrete structure are “edge-cut”, for example, the column part d behaves independently at the time of an earthquake. As a result, the wall body a receives a bending moment and a shearing force. There is nothing.

  In the slit e shown in FIG. 11, joint materials are usually installed for the purpose of ensuring waterproofness, dustproofing, soundproofing and the like equivalent to the wall body a. In FIG. 11, horizontally disposed joint material f is installed in the slit e at the lower part of the wall body a, and vertically disposed joint material f is installed in the slit e on both sides of the wall body a. These joint materials f are arranged so as to fill the space in order to seal the slits e in order to ensure waterproofness, dustproofing, soundproofing and the like.

  In addition to sealing the inside of the slit e, the joint material f is also used as a formwork when placing the concrete of the wall body a. Therefore, performance such as fire resistance, water resistance, predetermined strength and elasticity is required. Is done. In other words, fire resistance is a performance required to prevent the spread of fire in the event of a fire, and water resistance is a performance required to prevent leakage during completion and not absorb unnecessary moisture when placing concrete. It is. Further, as shown in FIG. 11, the joint material f disposed at the lower part of the wall body a is required to have a predetermined compressive strength in order to support the weight of fresh concrete (concrete that has not yet solidified) when the concrete of the wall body a is placed. . Furthermore, after the concrete is hardened, the wall body a suspended from the ceiling slab b shrinks (shortens) to the upper side due to drying shrinkage or the like. As a result, the interval between the slits e is widened. Performance that can follow the demand is also required. That is, the joint material f is capable of compressive deformation accompanying the placement of the wall body a concrete, and can be expanded and deformed after the concrete is hardened (hereinafter referred to as “elasticity”). Is also required.

  Conventionally, a joint material f as shown in FIG. 12 has been used as a joint material f exhibiting various performances such as fire resistance, water resistance, predetermined strength and elasticity. FIG. 12 is a cross-sectional view taken along the arrow Y-Y shown in FIG. 11 and is a detailed view of a joint material f conventionally used. The joint material f shown in this figure is formed by arranging three plate-shaped (bar-shaped) members in a plane, and a non-combustible member f1 formed of a non-combustible material is disposed at the center, and is easily deformable on both sides. The formed elastic member f2 is disposed. Examples of the material of the incombustible member f1 include rock wool, ceramic fiber, calcium silicate, and the like, and examples of the elastic member f2 include a resin such as polyethylene (PE). As described above, the conventional joint material f is configured such that the nonflammable member f1 shares fire resistance, and the elastic member f2 shares water resistance, predetermined strength, and elasticity.

  In addition, a technique such as Patent Document 1 has also been proposed with the object of providing a device with better fire resistance. The seismic slit material shown here consists of a main body and a thermal expansion refractory sheet affixed to the surface of the main body. Even if the main body burns out in the event of a fire, the thermal expansion refractory sheet thermally expands to prevent intrusion of flame It is something that can be done.

JP 2002-180694 A

Conventional joint materials have two major problems. One of them is the non-land response when installing the joint material f. In many cases including FIG. 11, a concrete structure that has already been constructed (hereinafter referred to as “already constructed concrete structure”). In the case of FIG. 11, the joint material f is installed on the surface of the floor slab c. However, unevenness occurs on the surface of the already constructed concrete structure. Therefore, it becomes difficult to install the joint material f, and the joint material f remains at a high level according to the unevenness of the unevenness (supported by the convex portion). The significance of installing the material f is greatly impaired.

As described above, there has been no proposal of a technology that makes the problem of unevenness of the joint material installation surface a problem to be solved. The joint material f in three bodies shown in FIG. 12 does not have the elasticity that the incombustible members f1 arranged in the center correspond to the unevenness, and as a result, the entire joint material f cannot cope with the unevenness. Yes. In addition, since the seismic slit material proposed in Patent Document 1 has a different problem in the first place, no technology for dealing with unevenness is disclosed.

The second problem is the complexity of production and installation. The three-piece joint material f shown in FIG. 12 is obtained by arranging two different members in parallel, and the performance shared by each member is as described above. That is, the elastic member f2 shares the water resistance, and the non-combustible member f1 does not correspond to this. However, since the waterproofing function as the joint material f as a whole is not exhibited, a waterproof tape is applied from one elastic member f2 to the other elastic member f2, and the non-combustible member f1 is covered with the waterproof tape. Thus, in addition to arranging a plurality of members, a process of applying a waterproof tape is further required, and the production thereof is complicated.

Also, the installation work at the corners such as the entrance corner and the exit corner shown in FIG. 13 is complicated. FIG. 13 is a plan view showing a corner portion where the joint material f is installed. As shown in this figure, the two joint materials f to be faced must be cut obliquely. It is difficult to precisely perform this oblique cutting, and therefore it is extremely difficult to abut both joint materials f without gaps. Moreover, the incombustible members f1 (or the elastic members f2) constituting the joint material f need to be abutted so as to be continuous, but it is difficult to accurately perform this, as shown in FIG. There was a gap.

The earthquake-resistant slit material proposed in Patent Document 1 can be manufactured simply by sticking a thermal expansion refractory sheet to the surface of the main body, but the difficulty of making the butting in the corner portion continuous and the thermal expansion refractory sheet continuous. Does not disclose any solution and still has the problem of complexity in installation.

  The subject of this invention is solving the problem which a prior art has. That is, it is to provide a joint material corresponding to the unevenness of the joint material installation surface and easy to manufacture and install, and to provide a slit structure in which the joint material is installed and its construction method.

  The present invention has been made with a focus on the fact that it can follow the unevenness of an already constructed concrete structure, and has been developed with a focus on a laminated structure of a material having an unevenness tracking function and a material excellent in fire resistance. It has been done.

  The laminated joint material of the present invention is a laminated joint material installed in a slit provided between a concrete structure and another concrete structure, and includes a first layer and a second layer that are different in material. The first layer is made of a material having higher fire resistance than the second layer, and the second layer is a material having higher elasticity than the first layer. It consists of

  The laminated joint material of the present invention is installed in a slit provided between an already constructed concrete structure and a newly constructed concrete structure, and the laminated concrete structure The surface on the second layer side is arranged on the joint material installation surface, and the second layer can absorb unevenness of the joint material installation surface by its elastic performance.

  In the laminated joint material of the present invention, the thickness of the second layer may be 5 mm or more and 10 mm or less.

  The slit structure of the present invention is a structure in which a laminated joint material is installed in a slit provided between a concrete structure and another concrete structure, and the laminated joint material is different from the first layer and the first layer. It is a laminate comprising two layers, the first layer is made of a material having a high fire resistance compared to the second layer, and the second layer has a higher elasticity than the first layer. The slit is sealed with the laminated joint material.

  The slit construction method of the present invention is a slit construction method provided between an already constructed concrete structure and a concrete structure that newly constructs a new concrete structure. A joint material installation step of installing a laminated joint material on the surface, and a concrete placement step of placing the new concrete in a state where the joint material is installed, wherein the laminated joint material includes a first layer of different materials and A laminated body including a second layer, wherein the first layer is made of a material having high fire resistance compared to the second layer, and the second layer is higher than the first layer. In the joint material installation step, the second layer side surface of the laminated joint material is disposed on the joint material installation surface of the already constructed concrete structure.

The laminated joint material of the present invention, the slit structure provided with the laminated joint material, and its construction method have the following effects.
(1) A laminated structure in which the first layer and the second layer are superposed, and can be manufactured very easily.
(2) The first layer is made of a material having high fire resistance, and can reliably prevent the intrusion / extrusion of the flame.
(3) The second layer is made of a material having high elasticity, and can reliably follow the load at the time of placing concrete and deformation at the time of drying shrinkage. Furthermore, even when the non-land surface of the pre-constructed concrete structure is used as the joint material installation surface, the high elasticity of the second layer can reliably seal the slit gap corresponding to this non-land surface. Is possible.
(4) The second layer is made of a material having high water resistance, and can reliably prevent water from entering from the outside.
(5) In corner portions such as entering corners and protruding corners, it is not necessary to perform planar positioning for each material, and joint materials can be easily abutted.

The front view which shows the state by which the laminated joint material of this invention was installed in the wall body constructed | assembled by the suspension method. It is XX arrow sectional drawing shown in FIG. 1, and is detail drawing explaining the structure of a laminated joint material. The model figure of the fire-proof experiment of a slit. The temperature change figure in the location which does not provide a slit. The temperature change figure in the uppermost slit part. The temperature change figure in a middle slit part. The temperature change figure in the lowermost slit part. (A) is a first step diagram showing a stage where a floor slab is constructed, (b) is a second step diagram showing a stage where a laminated joint material is installed on the floor slab, and (c) is a wall body and a column part. The 3rd step figure which shows the stage which started up. The expanded sectional view which shows the state which the 2nd layer body contact | adhered to the floor slab upper surface. The top view which shows the corner part which installs a laminated joint material. The front view which shows the wall body constructed | assembled by the hanging construction method. It is YY arrow sectional drawing shown in FIG. 11, and is a detailed drawing of the conventional joint material. The top view which shows the corner part which installs a joint material.

[Embodiment]
An embodiment of a laminated joint material of the present invention, a slit structure provided with the laminated joint material, and a construction method thereof will be described with reference to the drawings.

  First, the state in which the laminated joint material of the present invention is installed will be briefly described. FIG. 1 is a front view showing a state in which a laminated joint material of the present invention is installed on a wall body constructed by a suspension method. Note that FIG. 1 is the same as FIG. 11 except for the joint material that is installed, and the same components as those in FIG. As described above, in the suspension method, the wall body a is fixed only by the ceiling slab b (in the drawing, a broken line is drawn at the boundary between the ceiling slab b and the wall body a, but actually it is an integral structure). . A horizontal slit 10 is provided between the wall body a and the floor slab c, and vertical slits 20 are provided between the wall body a and the pillar portions d on both sides. By providing these slits, the load acting on the wall body a does not directly act on the surrounding concrete structure, and the wall body a and other concrete structures behave independently during an earthquake. To do. That is, other concrete structures such as the column part d do not receive a bending moment or a shearing force due to the behavior of the wall body a.

  The horizontal slit 10 is a space formed between the wall body a and the floor slab c, though it is minimal. If the state of this space is a complete form, unnecessary things will invade from here, and sound will also leak. Therefore, in order to ensure waterproofness, dustproofness, soundproofing properties and the like equivalent to the wall body a, the laminated joint material 30 is installed in the horizontal slit 10 so as to fill the space. Similarly, a normal joint material 40 is installed in the vertical slit 20. For convenience, the laminated joint material 30 is installed only in the horizontal slit 10 in FIG. 1, but the laminated joint material 30 can also be installed in the vertical slit 20. Further, here, the case of the hanging method is described as an example, but the present invention is not limited to this method, and the concrete structures are adjacent to each other, for example, waist walls and leaning walls. It can be implemented in various concrete structure adjacent parts, such as vertical mating parts or horizontal mating parts of scallop walls.

(Laminated joint material)
Next, the configuration of the laminated joint material 30 will be described in detail. FIG. 2 is a cross-sectional view taken along the line XX shown in FIG. 1 and is a detailed view illustrating the configuration of the laminated joint material 30.

  As shown in FIGS. 1 and 2, the laminated joint material 30 has a plate shape. The planar shape is substantially rectangular, the dimension (width) in the lateral direction is substantially equal to the thickness of the wall body a, and the dimension (length) in the longitudinal direction is substantially equal to the dimension between the column parts d. Of course, the laminated joint material 30 of the present invention is not limited to such a shape, and in particular, the length can be shorter than the dimension between the pillar portions d. For example, when the dimension between the column parts d is 6 m, the length of the laminated joint material 30 can be 2 m, and three of these can be arranged in series between the column parts d.

  Further, the thickness of the laminated joint material 30 is preferably set to be approximately equal to or slightly thicker than the distance between the wall body a and the floor slab c, that is, the height of the horizontal slit 10. This is because the space of the horizontal slit 10 is surely sealed and the waterproofness, dustproofness, soundproofness, etc. equivalent to the wall body a are ensured. Generally, the height of the horizontal slit 10 is 1/100 of the height of the wall body a. If the wall body a is about the floor height (about 3 m), the height of the horizontal slit 10 is about 30 mm. In other words, the thickness of the laminated joint material 30 in this case is desirably about 30 mm.

  As shown in FIG. 2, the laminated joint material 30 is a laminated body including a first layer body 31 and a second layer body 32. That is, the plate-like first layer body 31 and the plate-like second layer body 32, which are substantially the same in plan view, are integrally formed by overlapping in the vertical direction (left and right direction when installed in the vertical slit 20). Has been. In addition, in order to comprise the laminated joint material 30 of this invention, it is sufficient to include at least two layers of the first layer body 31 and the second layer body 32, and in addition to these two layers, further different layers are stacked. It doesn't matter. Of course, in terms of production cost, it is desirable that the first layer body 31 and the second layer body 32 be composed of only two layers, but the outside of the first layer body 31, the first layer body 31 and the second layer body 32. It goes without saying that even if a layered product is formed by stacking other layers having different performances, the layer is included in the technical scope of the present invention.

  The first layer body 31 and the second layer body 32 constituting the laminated joint material 30 use different materials because the required performances are different. The first layer 31 is formed of a material having excellent fire resistance because fire resistance is required. Examples of the material include calcium carbonate foam, rock wool, ceramic fiber, and calcium silicate. In addition to these, metals such as iron and alloys can be mentioned, but careful consideration is required to adopt them in terms of manufacturing cost and workability due to weight. Since the calcium carbonate foam has not only excellent fire resistance but also appropriate compressive strength and elasticity that can be flexibly deformed, it can be said to be a desirable material for the first layer 31.

  The second layer body 32 constituting the laminated joint material 30 is required to have water resistance and appropriate elasticity. Examples of materials that satisfy these performances include resins such as polyethylene (PE) and polypropylene (PP). Furthermore, in order to exhibit the elasticity which can deform | transform more flexibly, adoption of the foam of PE or PP is suitable, and what was made to expand 40-40 times more desirably is good. The reason why such high elasticity is required is to cope with unevenness of the surface on which the laminated joint material 30 is installed, and more specifically, unevenness on the installation surface of the laminated joint material 30. In order to reliably fill the gap generated in the recess by being flexibly deformed according to the above.

  As described above, the first layer body 31 is required to have fire resistance, and the second layer body 32 is required to have water resistance and appropriate elasticity. In other words, the first layer body 31 does not necessarily need water resistance performance and appropriate elasticity, and the second layer body 32 does not necessarily require fire resistance performance. Of course, the first layer body 31 does not require water resistance performance. Alternatively, the second layer body 32 may have fire resistance.

  As shown in FIG. 2, the second layer body 32 can be made thinner than the first layer body 31. The reason why the second layer body 32 is thin is to prevent the intrusion and exudation of a flame from the gap even when the second layer body 32 is burned out in the event of a fire.

  In general, the fire resistance performance of the slit is considered to be the performance that suppresses the flame from being transferred to the opposite side of the wall for 2 hours when a fire occurs. Therefore, the inventor of the present application experimented with the first layer 31 as the calcium carbonate foam and the second layer 32 as the PE foam.

  FIG. 3 is a model diagram of the experiment. A simulated fire was caused on the surface side (the back side in the figure) of the concrete wall shown in this figure, and the temperature on the back side (the near side in the figure) of the concrete wall was measured over time. The concrete wall is provided with three horizontal slits from above. A laminated joint material 30 comprising a first layer body 31 having a thickness of 40 mm and a second layer body 32 having a thickness of 5 mm is installed in the first stage slit t1, and a thickness of 15 mm is provided in the second stage slit t2. A laminated joint material 30 comprising a first layer body 31 and a second layer body 32 having a thickness of 10 mm is installed, and a first layer body 31 having a thickness of 25 mm and a first layer body having a thickness of 5 mm are provided in the third slit t3. A laminated joint material 30 composed of a two-layer body 32 is installed.

  The results of the experiment are shown in FIGS. In each figure, the horizontal axis represents time, and the vertical axis represents the measured temperature. 4 shows the temperature change at the measurement point where the slit is not provided, FIG. 5 shows the temperature change at the measurement point which is the first-stage slit t1, and FIG. 6 shows the measurement at the second-stage slit t2. FIG. 7 shows the temperature change at the measurement point, which is the first-stage slit t3. As can be seen from these figures, when the temperatures after 2 hours are compared, the concrete part (FIG. 4) is around 70 ° C., whereas it is 70 ° C. for slit t2 (FIG. 6) and slit t3 (FIG. 7). Before and after, the slit t1 (FIG. 5) is about 50 ° C. As a result, it was found that if the thickness of the second layer body 32 is 10 mm or less, the wall body a is not affected by the flame. On the other hand, in another experiment, it was also found that if the thickness of the second layer body 32 is 5 mm or more, necessary elasticity is ensured. That is, the layer thickness of the second layer body 32 is desirably 5 mm or more and 10 mm or less.

(Structure and construction method)
Next, the slit structure in which the laminated joint material 30 is installed and its construction method will be described. FIGS. 8A to 8C are step diagrams showing an order of constructing the slit structure in which the laminated joint material 30 is installed, and FIG. 8A is a first step diagram showing a stage in which the floor slab c is constructed. (B) is the 2nd step figure which shows the stage where the laminated joint material 30 was installed on the floor slab c, (c) is the 3rd step figure which shows the stage where the wall body a and the column part d stood | started up. For convenience, illustration of the formwork and the reinforcing bars is omitted. Each step diagram will be described below.

  As shown in FIG. 8A, a floor slab c is first constructed. In constructing the floor slab c, a normal rebar is assembled, a formwork is installed, and concrete is placed. In addition, after placing concrete, the upper surface is carefully leveled with a gold iron or the like. However, it is impossible for a person to level it completely, and unevenness (uneven surface) remains on the upper surface s of the floor slab.

  After sufficiently curing the concrete of the floor slab c, as shown in FIG. 8B, a “joint material installation step” is performed in which the laminated joint material 30 is installed on the floor slab upper surface s. At this time, the laminated joint material 30 is arranged so that the second layer body 32 becomes the lower surface, that is, the floor slab upper surface s (laminated joint material installation surface) and the second layer body 32 are in contact with each other. This is because the high elasticity of the material of the second layer body 32 follows the unevenness of the floor slab upper surface s. The laminated joint material 30 may be simply placed on the floor slab upper surface s, but may be fixed using an adhesive, a concrete nail, or the like.

  FIG. 9 is an enlarged cross-sectional view showing a state in which the second layer body 32 is in close contact with the floor slab upper surface s. As shown in this figure, the second layer body 32 does not stay high at the convex portion of the floor slab upper surface s, but is deformed flexibly and enters the concave portion without a gap. Thus, the high elasticity which the material of the 2nd layer body 32 comprises can absorb the unevenness of floor slab upper surface s, and can keep the upper surface of the 1st layer body 31 substantially horizontal. Note that the same effect can be expected not only when the laminated joint material 30 is installed horizontally but also when the laminated joint material 30 is installed in a straight direction. For example, although the surface of the column part d previously placed with concrete (laminated joint material installation surface) is uneven, the laminated joint material 30 is arranged so that the second layer body 32 is in contact with this surface. For example, the second layer body 32 can absorb the unevenness of the surface of the column part d to keep the surface of the first layer body 31 substantially vertical, and the quality of the concrete placed on the adjacent wall body a is improved. .

  After installing the laminated joint material 30 on the floor slab upper surface s (laminated joint material installation surface), a predetermined reinforcing bar and a formwork are assembled, and a wall body a and a column part d (further, a ceiling slab b may be added). Carry out the “concrete placing process” to place concrete. The vertical joint is installed between the mold on the front side (front side of the drawing) and the mold on the back side (back side of the drawing). At this time, since the floor slab c has already been placed in concrete, the floor slab c is referred to as “already constructed concrete structure”. On the other hand, what is constructed after installing the laminated joint material 30 is referred to as “new concrete structure”. . That is, the laminated joint material 30 of the present invention is installed in the slit e between the already constructed concrete structure and the newly constructed concrete structure, and the laminated joint material installation surface (non-land) of the already constructed concrete structure. The second layer body 32 is in contact with the generation surface), in other words, the surface of the first layer body 31 is set to be a formwork surface of the new concrete structure.

  Finally, as shown in FIG. 8 (c), the concrete of the ceiling slab b is cast to complete a series of structures. In FIG.8 (c), the space is formed between the wall body a and the floor slab c, and also the laminated joint material 30 is installed in this space, Such a structure is equipped with the "laminated joint material" of this invention. Slit structure ”.

(Corner)
FIG. 10 is a plan view showing a corner portion where the laminated joint material 30 is installed. As shown in this figure, when a laminated joint material having a special shape (hereinafter referred to as “the accessory 30a”) is arranged at corners such as the entrance corner and the exit corner, the whole can be easily accommodated. The laminated joint material 30 of the present invention does not need to be abutted after the end of the laminated joint material 30 is cut obliquely as in the prior art, and it is not necessary to perform planar alignment for different materials. Moreover, even if the dimension of the accessory 30a becomes longer (or shorter) than planned, as shown by the arrow in FIG. 10, it is easy to cut the stepped joint material 20 at the site and adjust the length. Can be paid.

  The laminated joint material of the present invention, the slit structure provided with the laminated joint material, and its construction method can be used in apartment buildings and office buildings such as condominiums, as well as in all building structures such as school buildings and warehouses. Yes, it can also be applied in the field of civil engineering structures, such as when installing precast structures between abutments and bridge girders, or on cast-in-place concrete foundations.

DESCRIPTION OF SYMBOLS 10 Horizontal slit 20 Vertical slit 30 Laminated joint material 31 1st layer body 32 2nd layer body 30a Accessory 40 Normal joint material a Wall body b Ceiling slab c Floor slab d Column part e Slit f Joint material f1 Nonflammable member f2 Elastic member s Floor slab top surface

Claims (4)

A laminated joint material provided between an already constructed concrete structure and a newly constructed concrete structure ,
It is a laminate composed of a first layer and a second layer made of different materials,
The first layer is made of a material having high fire resistance compared to the second layer,
The second layer is made of a material having higher elasticity than the first layer,
On the joint material installation surface of the already constructed concrete structure, the second layer side surface is disposed,
The layered joint material, wherein the second layer can absorb unevenness of the joint material installation surface due to its elastic performance .   The laminated joint material according to claim 1 or 2, wherein a thickness of the second layer is 5 mm or more and 10 mm or less. A slit structure in which a laminated joint material is installed in a slit provided between an already constructed concrete structure that has already been constructed and a new concrete structure that is newly constructed ,
The laminated joint material is a laminated body including a first layer and a second layer that are different from each other in material, and the first layer is made of a material having high fire resistance as compared with the second layer, The second layer is made of a material having higher elasticity than the first layer,
The second layer side surface is disposed on the joint material installation surface of the constructed concrete structure that is sealed with the laminated joint material, and the second layer has the joint material installation surface according to its elastic performance. The slit structure provided with the laminated joint material characterized by being able to absorb the unevenness of the surface. In the construction method of the slit provided between the already constructed concrete structure that has already been constructed and the concrete structure that constructs a new concrete structure,
A joint material installation step of installing a laminated joint material on the already constructed concrete structure,
In the state where the joint material is installed, a concrete placing step for placing the new concrete is provided, and
The laminated joint material is a laminated body including a first layer and a second layer that are different from each other in material, and the first layer is made of a material having high fire resistance as compared with the second layer, The second layer is made of a material having higher elasticity than the first layer,
In the joint material installation step, the second layer side surface of the laminated joint material is disposed on the joint material installation surface of the already constructed concrete structure.

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