JP6865545B2 - How to build the silo hopper - Google Patents

Description

The present invention relates to a method for constructing a silohopper portion.

In silos such as coal, aggregates and grains, it is common to guide the contents (coal, etc.) into the payout space formed at the bottom and transport the contents by a belt conveyor arranged in this payout space. Is. The contents are guided to the payout space by using the payout device arranged in the silo hopper portion in the silo hopper portion formed directly above the payout space at the bottom of the silo.
The silo hopper portion is formed by a hopper skeleton formed so as to sandwich the payout space. The hopper skeleton generally includes an upper skeleton that forms an inclined surface of the silo hopper portion and a lower skeleton that supports the upper skeleton and forms a side wall of the payout space.
Further, in the silo hopper portion, a housing for accommodating the payout device is formed along the upper part of the payout space. The housing is suspended by a beam laid on top of the hopper skeleton.

The hopper skeleton, housing and beams are generally made of cast-in-place concrete. However, the construction using cast-in-place concrete requires reinforcement work, formwork assembly / removal work, concrete curing, etc., which hinders shortening of the construction period.
In the construction method of Patent Document 1, the construction period is shortened by constructing the upper skeleton of the hopper skeleton with precast members. The upper skeleton is supported by a partition wall formed so as to be orthogonal to the axial direction of the hopper skeleton. In the construction method of Patent Document 1, the upper skeleton is placed on the partition wall, and then the lower skeleton is formed of cast-in-place concrete.

Japanese Unexamined Patent Publication No. 08-135244

The partition wall that functions as a support member of the hopper skeleton needs to have a sufficient proof stress against the loading load, so that the amount of reinforcement is increased. Therefore, when the precast member is adopted, the weight of one piece becomes large, so that it takes time and effort for transportation and construction.
On the other hand, due to the suspension of use of nuclear power plants due to the Great East Japan Earthquake, most of the electricity is covered by thermal power generation. Large-scale silos (coal silos) used for thermal power generation are aging and require the construction of large-scale silos for the purpose of increasing power generation. Further early construction is required for various silos.
From this point of view, it is an object of the present invention to propose a method for constructing a silohopper portion capable of early construction.

In order to solve the above problems, the present invention presents a hopper skeleton formed so as to sandwich the payout space, a housing for a payout device formed above the payout space, and a beam laid horizontally on the hopper skeleton. It is a method of constructing a silo hopper part equipped with. Method of constructing the Sairohoppa portion includes a partition wall formation step of forming a partition wall of the previous SL hopper skeleton, a side wall portion forming step of forming a side wall of the hopper building frame, beneath said hopper skeleton on the side wall portion The first diagonal wall portion forming step of forming the diagonal wall portion, the beam mounting step of mounting the beam steel frame on the partition wall, the housing forming step of erection of the housing, and the hopper skeleton on the lower diagonal wall portion. In addition to forming the upper diagonal wall portion, a second diagonal wall portion forming step of forming the beam by placing concrete around the beam steel frame and forming the top of the hopper skeleton on the upper diagonal wall portion. It is provided with a top forming step. In the partition wall forming step, the partition wall is formed by arranging a pair of precast wall members at intervals and horizontally laying a precast upper wall member on the upper ends of the pair of the wall members. ..

According to the method of constructing the silo hopper portion, since the partition wall constituting the hopper skeleton is constructed by the precast member, the construction period can be shortened. Since the partition wall is divided into a plurality of precast wall members, it is easy to handle. The partition wall may be formed with a slit or an opening.

In the first diagonal wall forming step, the work of erection of the first precast concrete plate between the partition walls formed at intervals with respect to the axial direction (extension direction of the payout space) of the hopper skeleton, and the work of erection. The lower diagonal wall portion may be formed by the work of arranging the metal plate with a gap from the first precast concrete plate and the work of placing concrete between the first precast concrete plate and the metal plate. .. By adopting a so-called half PC member using the first precast concrete plate as the lower diagonal wall portion, the construction period can be shortened.
Further, in the side wall forming step, the work of arranging the formwork on the front surface and the back surface of the side wall, respectively, and the work of arranging the second precast concrete plate so as to project from the upper part of the side wall toward the payout space side. The side wall portion may be formed by the work of placing concrete in the space surrounded by the formwork and the second precast concrete plate. If a so-called half PC member is used for the projecting portion, the construction period can be shortened.

According to the method for constructing the silo hopper portion of the present invention, early construction of the silo becomes possible.

It is an elevation view which shows the coal storage facility which concerns on embodiment of this invention. It is sectional drawing which shows the coal silo. It is a figure which shows the silo hopper part, (a) is the AA sectional view of FIG. 2, and (b) is the BB sectional view of FIG. It is an enlarged sectional view which shows a part of the silo hopper part. It is a perspective view which shows the construction procedure of the construction method of the silo hopper part of this embodiment, (a) is a partition wall forming step, (b) is a side wall part forming step. (A) is a cross-sectional view showing a formwork arrangement work of a side wall portion forming step, and (b) is a plan view of the same. FIG. 5 is a perspective view showing a construction procedure of a method for constructing a silo hopper, which is a continuation of FIG. is there. FIG. 7 is a perspective view showing a construction procedure of a method for constructing a silo hopper portion following FIG. 7, in which (a) is a first diagonal wall portion forming step and (b) is a beam mounting step. It is sectional drawing of the beam mounting process. It is a perspective view of the housing formation process. (A) is a perspective view of the housing forming process following FIG. 10, and (b) is a perspective view of the metal plate installation work of the second diagonal wall portion forming process. FIG. 11A is a perspective view showing a second diagonal wall portion forming step following FIG. 11B, and FIG. 11B is a perspective view showing a top forming step.

In this embodiment, a case of constructing a coal storage facility will be described. As shown in FIG. 1, the coal storage facility of the present embodiment includes a plurality of coal storage silos (hereinafter, simply referred to as "coal silo 1"). The number and arrangement of the coal silos 1 are not limited and may be set as appropriate. For example, it is not always necessary to build a plurality of coal silos 1.
As shown in FIG. 2, the coal silo 1 of the present embodiment includes a foundation slab 11, a silo main body 12 erected on the foundation slab 11, and a roof portion 13 formed at the upper end of the silo main body 12. ing.

The foundation slab 11 is a bottom slab made of reinforced concrete. The thickness (height) of the foundation slab 11 is not limited and may be appropriately determined.
The silo body 12 is formed in a cylindrical shape. The shape of the silo body 12 is not limited, and may be, for example, a square cylinder. A silo hopper portion 2 is formed inside the silo main body 12. Further, an inner wall 14 is formed in the lower part of the silo main body 12 along the inner peripheral surface. The inner wall 14 has a truncated cone shape that shrinks in diameter toward the lower side.
As shown in FIG. 1, the roof portion 13 has a truncated cone shape whose diameter decreases toward the upper end. The shape of the roof portion 13 is not limited.

The silo hopper unit 2 guides the coal, which is the content of the coal silo 1, to the payout space 3 and discharges the coal to the outside of the coal silo 1. As shown in FIG. 3B, three rows of payout spaces 3, 3, and 3 are arranged side by side in the silo hopper portion 2 of the present embodiment. The payout space 3 is a space formed in a straight line. The end of the payout space 3 faces the outer surface of the coal silo 1. The payout space 3 has a cross-sectional shape in which a transportation means (not shown) such as a belt conveyor can be arranged (see FIG. 2).

As shown in FIGS. 2 and 3A, the silo hopper portion 2 includes a hopper skeleton 4, a beam 5, and a housing 6.
The hopper skeleton 4 is formed parallel to the payout space 3. In the present embodiment, the first hopper skeletons 41 and 41 formed between the payout spaces 3 and the second hopper skeleton 42 formed between the outer wall of the silo main body 12 and the payout space 3 are provided. .. In the present embodiment, the first hopper skeletons 41 and 41 in two rows are formed, but the number of the first hopper skeletons 41 is not limited and may be appropriately formed according to the number of payout spaces 3. Just do it.

The hopper skeleton 4 (first hopper skeleton 41 and second hopper skeleton 42) has an upper skeleton 7 forming an inclined surface of the silo hopper portion 2 and a lower skeleton 8 that supports the upper skeleton 7 and forms a side wall of the payout space 3. And a partition wall 9 that supports the upper skeleton 7 and the lower skeleton 8 from the back surface (the surface opposite to the payout space 3) is provided (see FIG. 4).

As shown in FIG. 4, the upper skeleton 7 of the present embodiment includes a lower diagonal wall portion 71 and an upper diagonal wall portion 72. The upper skeleton 7 of the first hopper skeleton 41 includes a top portion 73 formed at the upper end of the upper diagonal wall portion 72. On the other hand, the upper end of the upper diagonal wall portion 72 of the second hopper skeleton 42 is connected to the lower end of the inner wall 14. The configuration of the upper skeleton 7 is not limited, and may be appropriately determined. The lower diagonal wall portion 71 extends obliquely upward from the upper end of the lower skeleton 8, and is inclined so as to be separated from the payout space 3 toward the upper side. The upper diagonal wall portion 72 extends obliquely upward from the upper end of the lower diagonal wall portion 71. Further, the lower diagonal wall portion 71 and the upper diagonal wall portion 72 that are continuous vertically are inclined at the same angle. Similarly, the vertically continuous inner wall 14, the upper diagonal wall portion 72, and the upper diagonal wall portion 72 and the top portion 73 are also inclined at the same angle.

The lower skeleton 8 includes a side wall portion 81 and an overhanging portion 82 formed on the upper portion of the side wall portion 81, and has an inverted L-shape in cross-sectional view. The side wall portion 81 is continuous along the side surface of the payout space 3 (see FIG. 3A). The overhanging portion 82 projects from the upper portion of the side wall portion 81 toward the upper side of the payout space 3. A gap for guiding coal (contents) to the payout space 3 is formed between the overhanging portions 82 of the lower skeleton 8 adjacent to each other across the payout space 3. The size of the gap between the overhanging portions 82 is not limited, but is about 700 mm in the present embodiment.

The partition walls 9 are formed so as to intersect the axial direction of the hopper skeleton 4 (longitudinal direction of the payout space 3), and a plurality of partition walls 9 are formed at intervals with respect to the axial direction of the hopper skeleton 4. In the present embodiment, the first partition wall 91 is formed at the position of each beam 5, and the second partition wall 92 is formed at an intermediate position between the adjacent beams 5 (see FIG. 5A). The location where the partition wall 9 is formed is not limited, and may be appropriately determined. The partition wall 9 is formed by combining a plurality of wall members 90, 90, .... Further, an opening 93 is formed in the central portion of the partition wall 9. The opening 93 of the partition wall 9 does not necessarily have to be formed. That is, the inside of the hopper skeleton 4 may be completely shielded by the partition wall 9. Further, the shape of each partition wall 9 (first partition wall 91 and second partition wall 92) is not limited.

As shown in FIGS. 3A and 4, the beam 5 is orthogonal to the payout space 3 and the hopper skeleton 4. Both ends of the beam 5 are connected to the inner surface of the outer wall of the silo body 12. In this embodiment, a plurality of beams 5, 5, ... Are arranged side by side. That is, the silo hopper portion 2 of the present embodiment has a plan view grid shape due to the hopper skeleton 4 and the beam 5. The beam 5 of the present embodiment has a steel-framed reinforced concrete structure. The structure of the beam 5 is not limited, and may be, for example, a reinforced concrete structure. Further, the beam 5 need only intersect with the hopper skeleton 4, and does not necessarily have to be orthogonal to each other.

The housing 6 is formed directly above the payout space 3 and parallel to the payout space 3. The housing 6 includes a gate-shaped housing body 61 and a support portion 62 integrally formed on the upper portion of the housing body 61. The housing body 61 is a cross-sectional gate-shaped concrete member, and the lower end is open. The payout device can be stored inside the housing body 61. The support portion 62 is a beam member made of steel-framed reinforced concrete formed so as to intersect the beam 5. That is, both ends of the support portion 62 are connected to the side surfaces of the adjacent beams 5 and 5. The configuration of the support portion 62 is not limited, and may be made of reinforced concrete, for example.

The method for constructing the silo hopper is a partition wall forming step, a side wall forming step, a first diagonal wall forming step, a beam mounting step, a housing forming step, a second diagonal wall forming step, and a top forming step. And have.
The partition wall forming step is a step of forming the partition wall 9 as shown in FIG. 5 (a). The partition wall 9 is formed by combining a plurality of precast wall members 90, 90. The partition walls 9 are formed at intervals with respect to the axial direction of the hopper skeleton 4. In the present embodiment, the first partition wall 91 is formed according to the position of the beam 5, and the second partition wall 92 is formed between the adjacent first partition walls 91.

In the first partition wall 91, a pair of wall members 90, 90 are arranged at intervals (openings 93), and the first upper wall member 94 is laid horizontally on the upper ends of both wall members 90, 90. Form. That is, the first partition wall 91 has a gate shape. The upper end of the wall member 90 is flat. The wall member 90 has a sufficient yield strength as a support member for the beam 5. The wall member 90 includes a rectangular portion formed along the back surface of the lower skeleton 8 and a trapezoidal portion formed above the upper skeleton portion and having an inclined lower portion at the same angle as the inclined surface of the upper skeleton 7. It has. The shape of the wall member 90 is not limited. The first upper wall member 94 is a front view trap-shaped member having a lower side having a width larger than that of the upper side. The first upper wall member 94 may be arranged as needed.
In the second partition wall 92, a pair of wall members 90, 90 are arranged at intervals (openings 93), and the second upper wall member 95 is laid horizontally on the upper ends of both wall members 90, 90. Form. That is, the second partition wall 92 has a gate shape. The second upper wall member 95 is a front viewing table-shaped member whose lower side has a width larger than that of the upper side and whose height is larger than that of the first upper member 94. The second upper wall member 95 may be arranged as needed. The shape and dimensions of the wall member 90 constituting the second partition wall 92 may be the same as or different from the shape and dimension of the wall member 90 constituting the first partition wall 91. Further, the first upper wall member 94 and the second upper wall member 95 do not necessarily have to have a front view trapezoidal shape, and their shapes are not limited.

The side wall forming step is a step of forming the lower skeleton 8 of the hopper skeleton 4 (see FIG. 5B). The side wall forming step of the present embodiment includes a formwork arranging work, a PCa plate erection work for an overhanging part, and a concrete placing work.
In the formwork arranging work, as shown in FIG. 6A, the first formwork 83 is installed so as to be flush with the end face of the wall member 90, and a gap is left from the first formwork 83 for the second formwork. The formwork 84 is arranged. That is, the first formwork 83 and the second formwork 84 are installed at positions corresponding to the back surface (the surface opposite to the payout space 3) and the front surface (the surface on the payout space 3 side) of the side wall portion 81, respectively. As shown in FIG. 6B, the second formwork 84 is arranged between the partition walls 9 adjacent to each other in the axial direction of the hopper skeleton 4. In addition, necessary reinforcing bars (not shown) will be arranged along with the installation of the formwork 83 and 84.

In the work of erection of the PCa plate for the overhanging portion, the precast concrete plate 85 for the overhanging portion 82 is arranged so as to project from the upper part of the side wall portion 81 toward the payout space 3. The precast concrete plate 85 is a half precast member that forms a part of the overhanging portion 82 of the lower skeleton 8, and covers the lower surface and the tip of the overhanging portion 82. In the present embodiment, the precast concrete plate 85 is supported by the support work 86.
In the concrete placing work, concrete is placed in the space surrounded by the formwork 83, 84 and the precast concrete plate 85. As a result, as shown in FIG. 5B, the lower skeleton 8 in which the side wall portion 81 and the overhanging portion 82 are integrated is formed. After curing the concrete, the formwork 83 and 84 are removed.

The first diagonal wall portion forming step is a step of forming the lower diagonal wall portion 71 on the side wall portion 81 (see FIG. 8A).
The first diagonal wall portion forming step of the present embodiment includes a PCa plate erection work for an upper skeleton, a metal plate placement work, and a concrete placing work.
In the work of erection of the PCa plate for the upper skeleton, as shown in FIG. 7A, the precast concrete plate 74 for the upper skeleton 7 is erected between the partition walls 9. The precast concrete plate 74 is a half precast member that forms a part of the lower diagonal wall portion 71 and the upper diagonal wall portion 72 of the upper skeleton 7. The precast concrete plate 74 has an inverted V shape when viewed from the front. The axial end of the hopper skeleton 4 of the precast concrete plate 74 is placed on the upper end of the adjacent partition wall 9. That is, the precast concrete plate 74 is laid horizontally on the partition walls 9 and 9 adjacent to each other in the axial direction of the hopper skeleton 4. The lower end of the precast concrete plate 74 is placed on the upper surface of the lower skeleton 8.

In the metal plate arranging work, the first metal plate 75 is arranged as shown in FIG. 7 (b). The first metal plate 75 is arranged with a gap from the precast concrete plate 74 so as to be parallel to the precast concrete plate 74. The first metal plate 75 has a shape that covers the surface of the lower diagonal wall portion 71. The first metal plate 75 is formed by connecting a plurality of plate materials. Prior to the installation of the first metal plate 75, necessary reinforcing bars (not shown) are arranged on the lower diagonal wall portion 71.
In the concrete placing work, concrete is placed between the precast concrete plate 74 and the first metal plate 75. As a result, as shown in FIG. 8A, the precast concrete plate 74, the first metal plate 75, and the lower diagonal wall portion 71 in which the concrete is integrated are formed.

The beam mounting step is a step of erection of the beam steel frame 51 as shown in FIG. 8 (b). As shown in FIG. 9, the beam steel frame 51 is placed on the first partition wall 91 (see FIG. 5). In the present embodiment, a plurality of beam steel frames 51 connected in a straight line are laid horizontally in the silo main body 12. Further, a height adjusting spacer 53 is provided between the first partition wall 91 and the beam steel frame 51, if necessary. The method of connecting the beam steel frames 51 to each other is not limited. For example, a bolt penetrating both gusset plates and a beam steel frame 51 with a flange or a web of the beam steel frame 51 sandwiched between a pair of gusset plates (not shown) arranged across adjacent beam steel frames 51 and 51. It may be concluded by.

A concrete precast portion 52 is partially formed on the beam steel frame 51. The precast portion 52 is formed in a portion other than the joint portion between the beam steel frames 51 and the portion placed on the first partition wall 91. Further, the connecting member 54 of the housing 6 is integrally formed on the beam steel frame 51.
In the present embodiment, reinforcing bars (not shown) are arranged around the beam steel frame 51 along with the erection of the beam steel frame 51. Further, a formwork (not shown) is arranged along the lower surface of the beam steel frame 51. The reinforcing bar arrangement pitch, the reinforcing bar diameter, and the like are not limited and may be appropriately determined.

The housing forming step is a step of erection of the housing 6. First, as shown in FIG. 10, the support portion 62 is fixed to the connecting member 54 of the beam steel frame 51. At this time, the housing 6 (support portion 62 or housing main body 61) is supported from below (foundation slab 11) by a support (not shown). A precast portion 63 of the housing body 61 is fixed to the support portion 62 in advance. The precast portion 63 is formed intermittently so as not to come into contact with the beam steel frame 51.
Next, as shown in FIG. 11A, the remaining portion of the housing body 61 (field-cast portion 64) is formed. In the construction of the cast-in-place portion 64, necessary reinforcing bars (not shown) are arranged around the beam steel frame 51, and a formwork (not shown) is installed around the reinforcing bars, and concrete is installed in the formwork. It is done by placing. The cast-in-place portion 64 is formed in a state in which a part of the precast portion 52 formed in the beam steel frame 51 is involved.

The second diagonal wall portion forming step is a step of forming the upper diagonal wall portion 72 on the lower diagonal wall portion 71 (see FIG. 12A). The second diagonal wall portion forming step includes a bar arrangement work, a metal plate installation work, and a concrete placing work.
In the reinforcing bar arrangement work, reinforcing bars (not shown) required for the upper diagonal wall portion 72 are arranged along the surface of the precast concrete plate 74.

In the metal plate installation work, as shown in FIG. 11B, the second metal plate 77 is installed with a gap from the precast concrete plate 74 so as to be parallel to the precast concrete plate 74. In the present embodiment, along with the installation of the second metal plate 77, a formwork (not shown) is installed around the beam steel frame 51. The formwork is installed on the cast-in-place portion (part other than the precast portion 52) 54 (see FIG. 12A) of the beam 5. Further, a metal plate 65 for housing parallel to the second metal plate 77 is also installed on the support portion 62 of the housing 6.
In the concrete placing work, concrete is placed between the precast concrete plate 74 and the second metal plate 77, the space surrounded by the housing body 61 and the metal plates 65 and 65 for the housing, and around the beam 5 (inside the formwork). To place. As a result, as shown in FIG. 12A, the upper diagonal wall portion 72, the housing 6 and the beam 5 are integrally formed.

As shown in FIG. 12B, the top forming step is a step of forming tops 73, 66, 55 at the upper end of the hopper skeleton 4, the upper end of the housing 6, and the upper end of the beam 5.
The top portions 73, 66, 55 are formed by fixing a top precast member having a triangular cross-sectional view to the upper end of the upper diagonal wall portion 72, the upper end of the support portion 62, and the upper end of the beam 5. A metal plate is fixed to the surface of the top precast member.

According to the method for constructing the silo hopper portion of the present embodiment, the construction period can be shortened by constructing the partition wall 9 constituting the hopper skeleton 4 with a precast member. Since the wall member constituting the partition wall 9 is divided into a plurality of parts, it is easy to handle.
Further, since the so-called half PC member using the precast concrete plate 74 is used as the upper skeleton 7, the construction period can be shortened.
Since a so-called half PC member (precast concrete plate 85) is used for the overhanging portion 82, the construction period can be shortened.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-mentioned components can be appropriately modified without departing from the spirit of the present invention.
Although the silo for storing coal has been described in the above embodiment, the type of contents contained in the silo is not limited to coal. For example, aggregates used for concrete, asphalt, etc., powders such as cement, grains, etc. may be used.
In the above embodiment, the case where the lower diagonal wall portion 71 and the upper diagonal wall portion 72 are formed as harp precast members, respectively, has been described, but the lower diagonal wall portion 71 and the upper diagonal wall portion 72 may be full precast members. ..
Further, the upper skeleton 7 does not necessarily have to be divided into a lower diagonal wall portion 71, an upper diagonal wall portion 72, and a top portion 73. In the upper skeleton 7, the wall portion 71, the upper diagonal wall portion 72 and the top portion 73 may be integrally formed, or the wall portion 71 and the upper diagonal wall portion 72 or the upper diagonal wall portion 72 and the top portion 73 are integrally formed. You may.
Similarly, the lower skeleton 8 may also be formed of a full precast member.

1 Coal silo 2 Silo hopper 3 Payout space 4 Hopper skeleton 5 Beam 6 Housing 7 Upper skeleton 71 Lower diagonal wall 72 Upper diagonal wall 73 Top 74 Precast concrete plate (first precast concrete plate)
75 First metal plate (metal plate)
8 Lower skeleton 81 Side wall part 82 Overhang part 83, 84 Formwork 85 Precast concrete plate (second precast concrete plate)
9 partition wall 90 wall member

Claims (3)

It is a method of constructing a silo hopper portion including a hopper skeleton formed so as to sandwich a payout space, a housing for a payout device formed above the payout space, and a beam laid horizontally on the hopper skeleton. ,
And the partition wall forming step of forming a partition wall of the previous Symbol hopper building frame,
A side wall portion forming step for forming the side wall portion of the hopper skeleton, and
A first diagonal wall portion forming step of forming a lower diagonal wall portion of the hopper skeleton on the side wall portion,
The beam mounting process for mounting the beam steel frame on the partition wall, and
The housing forming process for erection of the housing and
A second diagonal wall portion forming step of forming the upper diagonal wall portion of the hopper skeleton on the lower diagonal wall portion and placing concrete around the beam steel frame to form the beam.
It is provided with a top forming step of forming the top of the hopper skeleton on the upper diagonal wall portion .
In the partition wall forming step, the partition wall is formed by arranging a pair of precast wall members at intervals and horizontally laying a precast upper wall member on the upper ends of the pair of the wall members. A method of constructing a silohopper part, which is characterized by the fact that. The first diagonal wall portion forming step is
The work of erection of the first precast concrete plate between the partition walls formed at intervals with respect to the axial direction of the hopper skeleton, and
The work of arranging the metal plate with a gap from the first precast concrete plate and
The method for constructing a silohopper portion according to claim 1, further comprising a work of placing concrete between the first precast concrete plate and the metal plate. The side wall forming step is
The work of arranging the formwork on the front and back of the side wall, respectively,
The work of arranging the second precast concrete plate so as to project from the upper part of the side wall portion toward the payout space side, and
The method for constructing a silohopper portion according to claim 1 or 2, wherein the work of placing concrete in a space surrounded by the formwork and the second precast concrete plate is provided.

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