JP6735214B2 - Construction method of concrete slab - Google Patents

Description

The present invention relates to a concrete slab construction method.

In some seismic isolation structures, columns 20 are provided on the seismic isolation device 10 to support the concrete slab 1 and the like thereon, as briefly shown in FIG. When the placed concrete contracts with the passage of time when the concrete slab 1 is constructed with such a seismic isolation structure, the columns 20 and the like move horizontally following the contraction of the concrete as shown in FIG. 12(b). However, the seismic isolation device 10 is deformed horizontally (shear deformation), and distortion occurs.

The shrinkage of concrete includes dry shrinkage and temperature shrinkage, and the shrinkage amount due to dry shrinkage and temperature shrinkage increases according to the scale of the concrete slab. If the scale of the concrete slab is large and the amount of shrinkage is large, the seismic isolation device will be distorted to a large extent, exceeding the permissible range, and the desired performance may not be achieved.

Therefore, conventionally, in order to keep the scale of the concrete slab below a certain level, it has been common to divide the concrete slab into several sections for construction and provide an expansion joint between the concrete slabs in each section.

Further, in Patent Document 1, in order to suppress the strain of the seismic isolation device due to the contraction of concrete, the concrete slab is divided into several sections for construction, and the concrete in each section is placed and hardened before the concrete A method is described in which pressure is applied from the side with a jack or the like to forcefully shrink the material, and then a filling material is filled between the concrete slabs in adjacent sections.

Patent No. 5491212

However, when an expansion joint is provided between the concrete slabs, there is a difficulty in that maintenance is difficult during use of the building after construction.

Further, when the concrete is forcibly compressed as in Patent Document 1, a large pressure by the jack is required. Therefore, a strong jack is required and costly, and it is difficult to control the pressure of the jack. Further, the compression work by the jack needs to be performed after the concrete is completely hardened, which causes a problem in terms of construction period.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for constructing a concrete slab that can easily suppress distortion of the seismic isolation device due to contraction of concrete.

The present invention for solving the above-mentioned problems, a step of forming concrete slabs of a plurality of sections supported via a seismic isolation device, and moving at least one of the concrete slabs of adjacent sections, the adjacent sections of A method of constructing a concrete slab, comprising: a step of widening an interval between the concrete slabs; and a step of filling a space filler between the concrete slabs of adjacent sections.

In the present invention, after concrete is cast in a plurality of sections to form a concrete slab, the concrete slabs in the adjacent sections are moved, and the intervals are widened to fill the packing material. At this time, the seismic isolation device is distorted, but as the concrete shrinks over time, the seismic isolation device returns to its original shape, and the seismic isolation device can be suppressed from being distorted within an allowable range. According to the present invention, since the concrete slab is moved instead of being compressed as described above, it is not necessary to apply a large pressure by a jack or the like, and the cost can be reduced and the pressure can be easily controlled. Further, the work can be started after the concrete is removed from the mold, which is also preferable in terms of construction period. Further, it is not necessary to provide an expansion joint between the concrete slabs, and maintenance is easy.

In the present invention, for example, both of the concrete slabs in the adjacent sections are moved to widen the interval. At this time, it is desirable that the number of seismic isolation devices supporting the concrete slabs in the adjacent sections be about the same.
In the present invention, both of the concrete slabs in the adjacent sections can be moved and the interval can be increased as described above. At this time, since the number of seismic isolation devices supporting the concrete slabs in both sections is the same, these concrete slabs are moved evenly when pushing between the concrete slabs using a jack etc. It is possible to prevent the concrete slab from moving greatly.

In the present invention, it is also possible to move the concrete slabs on both sides of the concrete slab in the central section to widen the interval. At this time, it is desirable that the number of seismic isolation devices that support the concrete slabs on both sides of the section be about the same.
In the present invention, as described above, the concrete slabs on both sides of the concrete slab in the central compartment can be moved to widen the intervals between the concrete slabs in the adjacent compartments. At this time, since the number of seismic isolation devices supporting the concrete slabs on both sides is similar, it is possible to move these concrete slabs evenly when pushing between the concrete slabs using a jack or the like. it can.

It is desirable that the average daily temperature of the average day of filling of the interstitial material is lower than the average ordinary temperature of the day when the concrete of the concrete slab in at least one of the sections is placed.
As a result, the filling material can be filled in a state where the concrete contracts due to the temperature, and the influence of the subsequent temperature contraction of the concrete can be reduced to keep the strain of the seismic isolation device within the allowable range.

Further, within a predetermined period, the casting start date and the filling start date are the maximum differences obtained by subtracting the average value of the daily average temperature of the filling start date from the normal value of the daily average temperature of the placement start date. It is also desirable to start placing concrete of the concrete slab in at least one of the sections and filling filling material with the filling material.
Thereby, the filling material is filled under the condition that the shrinkage of the concrete due to the temperature is maximized, and the influence of the subsequent temperature shrinkage of the concrete can be further reduced.

When viewed along the moving direction of the concrete slab, the total amount of movement of the concrete slab is 2 × 10 ^-4 × L/, where L is the length from end to end of the concrete slab of all sections in the moving direction. It is preferably 2 or more and 12×10 ⁻⁴ ×L/2 or less. It is also desirable to determine the moving amount of the concrete slab according to the length of the concrete slab along the moving direction of the concrete slab.
By setting the total amount of movement of the concrete slab within the above range, it is possible to finally restore the seismic isolation device to its original shape due to deformation due to drying shrinkage of the concrete and the like. Further, since the shrinkage amount of concrete due to drying or the like depends on its length, the seismic isolation device can be suitably returned to its original shape by determining the moving amount of the concrete slab according to the length of the concrete slab.

According to the present invention, it is possible to provide a method for constructing a concrete slab that can easily suppress distortion of the seismic isolation device due to contraction of concrete.

The figure which shows the outline of the construction method of the concrete slab 1. The figure which shows the outline of the construction method of the concrete slab 1. The figure which shows the outline of the construction method of the concrete slab 1. The figure which shows the outline of the construction method of the concrete slab 1. The top view of the slab 1. The top view of the slab 1. The figure which shows the floor above the floor directly above the seismic isolation device 10. The figure which shows the outline of the construction method of the concrete slab 1. The figure which shows the outline of the construction method of the concrete slab 1. The figure which shows the outline of the construction method of the concrete slab 1. The top view of the slab 1. The figure which shows the distortion of the seismic isolation apparatus 10.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
(1. Outline of construction method for concrete slab 1)
1 to 4 are diagrams showing an outline of a method for constructing a concrete slab according to the first embodiment of the present invention.

As shown in FIG. 1, in this embodiment, a pillar 20 is installed on a seismic isolation device 10 in a seismic isolation structure, and concrete is placed using a form (not shown) on the pillar 20. A concrete slab 1 (hereinafter sometimes simply referred to as a slab) is formed. In the example of FIG. 1, the concrete slab in the planned construction area is divided into two sections for construction, and the slab 1 in each section is supported via the seismic isolation device 10. Reinforcing bars 11 project from the slabs 1 in the respective sections in the respective directions, and the reinforcing bars 11 form a lap joint between the slabs 1.

A beam 30 is provided on the lower surface of the slab 1 in each section. In the example of FIG. 1, the beam 30 is a steel beam, and the beams 30 in adjacent sections are joined by the joining plate 31. The joint plate 31 is attached to each beam 30 by a bolt 32, but the bolt 32 on the side of one beam 30 (the beam 30 in the left section in the example of FIG. 1) is passed through the elongated hole 33 in the beam axial direction of the joint plate 31. The beams 30 in both sections are relatively movable in the beam axis direction until the bolt 32 is fully tightened.

In this embodiment, after the concrete of the slab 1 of each section is cast, the mold (not shown) is demolded and the jack 2 is placed between the slabs 1 of the adjacent sections as shown in FIG. 2(a). Deploy. Then, as shown in FIG. 2B, the gap between the slabs 1 is widened by the jack 2 to move the slabs 1 in both sections outward by the distance x.

As the slab 1 moves, the columns 20 and the beams 30 in both sections also move, and the seismic isolation devices 10 in both sections deform according to the movement of the columns 20. The amount of movement of the slab 1 is determined in consideration of the amount of shrinkage of concrete due to the subsequent drying shrinkage and temperature shrinkage, and the jack 2 forcibly spreads the slab 1 by the amount to be contracted.

Considering drying shrinkage and the like, when viewed along the moving direction of the slab 1 (corresponding to the left-right direction of FIG. 2B), the total amount of movement of the slab 1 by the jack 2 (example of FIG. 2B) Then, 2x) is preferably 2×10 ⁻⁴ ×L/2 or more and 12×10 ⁻⁴ ×L/2 or less. Here, L is the length from end to end of the slab 1 in all the sections in the moving direction. This length L is, for example, the length before the movement of the slab 1 (see L in FIG. 2A).

The above range is obtained by adding deformation due to temperature shrinkage to data of deformation due to drying shrinkage of many concrete slabs. That is, the amount of shrinkage due to drying of concrete falls within the range of approximately 2 × 10 ^-4 × L/2 to 8 × 10 ^-4 × L/2, and the maximum value of this range is the maximum amount of shrinkage due to temperature change of concrete. The above range is defined by adding 4×10 ⁻⁴ ×L/2. By keeping the total amount of movement of the slab 1 by the jack 2 within this range, the amount of contraction due to drying of concrete is canceled by the amount of movement, and the seismic isolation device 10 is finally returned to its original shape as described later. Can be returned.

Further, the moving amount of the slab 1 can be determined according to the length of the slab 1 when viewed along the above-described moving direction. That is, since the amount of shrinkage due to drying or temperature change of concrete depends on its length, by determining the amount of movement of the slab 1 according to the length of the slab 1, shrinkage due to drying etc. The amount can be canceled and the seismic isolation device 10 can eventually be restored to its original shape as described below.

In this way, the space between the slabs 1 is widened and the slabs 1 in both compartments are moved, and as shown in FIG. 3, the space filler 3 is filled between the slabs 1 in both compartments to connect the slabs 1 in both compartments. .. For example, concrete is used as the filling material 3, and the slabs 1 in both sections are connected and integrated by post-casting concrete between the slabs 1.

In consideration of temperature shrinkage, the filling start date of the filling material 3 (hereinafter sometimes referred to as a connection date) is the date when the concrete of the slab 1 in at least one of the sections is first placed (hereinafter, simply concrete It is advisable to set the average yearly temperature T2 of the average daily temperature of the filling material 3 to be lower than the average average temperature T1 of the daily average temperature (often called the start date of placing).

As a result, the filling material 3 is filled in a state where the concrete contracts due to the temperature, and the influence of the subsequent temperature contraction of the concrete is reduced to keep the strain of the seismic isolation device 10 within the allowable range. In addition, the normal value of the daily average temperature is an average of the daily average temperatures of the past day on a day-to-day basis in a predetermined period in the past (for example, the past 10 years, the past 20 years, the past 30 years, etc.), Data provided by the Meteorological Agency (see the Meteorological Agency website) can be used. Moreover, the value adopted as the normal year value is, for example, the value at the point where the normal year value as described above is obtained and which is the closest to the construction site of the concrete slab 1.

Particularly, in the present embodiment, the difference (T1-T2) obtained by subtracting the average value T2 of the average daily temperatures of the consolidated days from the average value T1 of the average daily temperatures of the concrete placing start dates within the predetermined period is the maximum. On the concrete pouring start date and the connection date, the concrete pouring of the slab 1 in at least one of the sections and the filling of the filling material 3 are started. Thereby, the filling material 3 is filled under the condition that the shrinkage of the concrete due to the temperature is maximized, and the influence of the subsequent temperature shrinkage of the concrete can be further reduced. The above-described predetermined period can be determined as a period in which the steps described in FIGS. 1 to 3 can be performed in consideration of the construction procedure of the seismic isolation structure as a whole.

When actually filling the filling material 3, check the temperature of the day (for example, the expected average temperature of the day obtained by the day before the day), and check the actual average temperature of the day when concrete is placed. Compare the difference (T1'-T2') minus the temperature T2' of the day from the value T1' and (T1-T2), if they differ by a predetermined amount, for example, the value of (T1'-T2') When is less than (T1-T2)/2, the filling of the filling material 3 can be postponed.

After the filling of the filling material 3 in this way, the days pass, and the drying shrinkage and the temperature shrinkage of the slab 1 progress, whereby the above-mentioned movement amount is gradually offset and the column 20 moves as shown in FIG. It is possible to construct the slab 1 in which a plurality of sections are integrated by eliminating the distortion of the seismic isolation device 10 by returning to the original position. The bolts 32 passed through the long holes 33 of the joining plate 31 are finally tightened at this point, and the beams 30 in adjacent sections are joined by the joining plate 31. Since the filling material 3 is provided in the narrow gap between the slabs 1, the shrinkage thereof is negligible as compared with the shrinkage of the slab 1.

(2. Other examples of construction method of concrete slab 1)
The above is the outline of the construction method of the concrete slab 1, and in the example of FIGS. 1 to 4, the slab 1 of each section is supported by one seismic isolation device 10. However, when the slab 1 is actually divided and constructed, the slab 1 in each section is often supported by a plurality of seismic isolation devices 10.

In such a case, for example, as shown in the plan view of FIG. 5, it is desirable to use the same number of seismic isolation devices 10 in adjacent sections. This is because when the number of seismic isolation devices 10 supporting the slabs 1 in both sections is different, the number of seismic isolation devices 10 is small when the slab 1 is moved by the jack 2 as described above, and the seismic isolation device 10 restrains the seismic isolation devices 10. This is because the slab 1 in one of the compartments with a small force may largely move, and eventually the seismic isolation device 10 may remain distorted. Note that, in FIG. 5, illustration of the reinforcing bars 11 and the like protruding from the slab 1 is omitted. This also applies to FIGS. 6 and 11 described later.

In FIG. 5, the slab 1 of each section is divided so as to be aligned in the left-right direction of the plane, and distortion of the seismic isolation device 10 in that direction can be prevented. For example, as shown in the plan view of FIG. It is also possible to prevent distortion of the seismic isolation device 10 in the horizontal direction of the plane and in the vertical direction orthogonal to the horizontal direction by dividing 1 at the same time. In this case as well, the number of seismic isolation devices 10 in the vertically and horizontally adjacent sections is the same. In this way, it is advisable to divide the concrete slab so that all the seismic isolation devices 10 in the adjacent sections have the same number and perform the construction in the procedure of FIGS. 1 to 4.

Further, in the above example, only the floor immediately above the seismic isolation device 10 has been described, but for the floors above it, it is possible to follow the movement of the slab 1 on the floor directly above the seismic isolation device 10, as shown in FIG. 7. It is desirable to keep. In the example of FIG. 7, only the columns 20 and the beams 30 are constructed on the floors directly above the seismic isolation device 10, and the beams 30 of the adjacent sections use the same bolts 32 and elongated holes 33 as those described above. The mechanism allows relative movement in the beam axis direction.

As described above, in the present embodiment, concrete is poured into a plurality of compartments to form the slab 1, then the slabs 1 in the adjacent compartments are moved, and the intervals are widened to fill the packing material 3. At this time, the seismic isolation device 10 is distorted, but as the concrete shrinks over time, the seismic isolation device 10 returns to its original shape, and the seismic isolation device 10 can be suppressed from being distorted within an allowable range. it can. Thereby, the seismic isolation device 10 can exhibit a predetermined performance.

In the present embodiment, since the slab 1 is moved instead of being compressed in each section as described above, it is not necessary to apply a large pressure by the jack 2, and the cost can be reduced and the pressure management is easy. In addition, the work can be started after demolding the concrete, which is desirable in terms of construction period. Further, it is not particularly necessary to provide an expansion joint between the slabs 1, and maintenance is easy.

In this embodiment, as described above, it is possible to move both of the slabs 1 in the two adjacent sections to widen the interval. At this time, since the number of the seismic isolation devices 10 supporting the slabs 1 in both sections is the same, when the spaces between the slabs 1 are widened using the jack 2, the slabs 1 are moved evenly and one of the sections is separated. It is possible to prevent the slab 1 from moving largely.

Further, in the present embodiment, the average value of the daily average temperature on the connecting day is lower than the average value of the average daily temperature of the concrete pouring start day described above, so that the filling material 3 of the filling material 3 is contracted in the presence of shrinkage of the concrete due to the temperature. The effect of temperature shrinkage of concrete after filling can be reduced. Especially, the slab of at least one of the sections on the concrete placing start date and the joining date, which has the maximum difference between the ordinary value of the average day temperature of the concrete placing day and the ordinary value of the average day temperature of the joining day. By starting the casting of the concrete No. 1 and the filling of the filling material 3, the influence of the subsequent temperature shrinkage of the concrete can be further reduced.

Further, by setting the total amount of movement of the slab 1 within the above range, the seismic isolation device 10 can be finally returned to its original shape due to the deformation caused by the drying shrinkage of concrete or the like. Further, since the shrinkage amount of concrete due to drying or the like depends on its length, by determining the moving amount of the slab 1 according to the length of the slab 1, the seismic isolation device 10 can be restored to its original shape. ..

However, the present invention is not limited to this. For example, although the slab 1 is moved using the jack 2 in this embodiment, the slab 1 may be moved by other moving means. For example, it is possible to use a mechanism that pulls and moves the slab 1 instead of pushing the space between the slabs 1. Also, the planar shape of the slab 1 in each section is not particularly limited.

Further, although the beam 30 is a steel beam in the present embodiment, the beam is not limited to this and may be an RC (reinforced concrete) beam. In this case, similarly to the slab 1 described above, the beams 30 of both sections are arranged at intervals, and the reinforcing bars are projected from the beams 30 of both sections toward each other to form a lap joint between the beams 30. It is possible. Also in this case, the beams 30 in both sections can move relative to each other in the beam axial direction as the slab 1 moves and contracts, and the beams 30 can be narrowed by concrete or the like.

Next, another example of the present invention will be described as a second embodiment. The second embodiment will mainly describe different points from the first embodiment, and similar points will be denoted by the same reference numerals in the drawings and the like, and description thereof will be omitted. Further, the configuration described in the second embodiment can be combined with the configuration described in the first embodiment as needed.

[Second Embodiment]
8 to 10 are views showing the outline of the method for constructing a concrete slab according to the second embodiment of the present invention.

As shown in FIG. 8, in this embodiment, the concrete slab in the planned construction area is divided into three sections, and the slab 1 in each section is supported via the seismic isolation device 10 as in the first embodiment. To be done. The beam 30 is provided on the lower surface of the slab 1 in each section, as in the first embodiment.

In this embodiment, after the concrete of the slab 1 in each section is cast, the mold (not shown) is demolded to separate the slab 1 in the central section and the sections on both sides thereof as shown in FIG. 9(a). Place the jacks 2 between the slabs 1 respectively. Then, as shown in FIG. 9B, the interval between the slabs 1 in the adjacent sections is widened by the jack 2. At this time, the slab 1 in the center section does not move, but the slabs 1 in the sections on both sides move outward by the distance x.

As the slab 1 moves, the columns 20 and beams 30 on both sides of the partition also move, and the seismic isolation devices 10 on both sides of the partition deform according to the movement of the column 20.

In this way, the slab 1 is moved and the space between the slabs 1 in the central compartment and the slabs 1 in the compartments on both sides of the slab 1 is spread out, and as shown in FIG. The material 3 is filled and the slabs 1 in adjacent sections are connected.

Similarly to the above, also in the present embodiment, after the filling of the interstitial material 3, the days pass, and the drying shrinkage and the temperature shrinkage of the slab 1 progress, whereby the above-mentioned movement amount is gradually offset, As shown in FIG. 10( b ), the pillars 20 on both sides of the section move and return to their original positions, the strain of the seismic isolation device 10 on both sides of the section is eliminated, and a slab 1 in which a plurality of sections are integrated is constructed. It becomes possible to do. Similar to the above, the bolts 32 passed through the long holes 33 of the joining plate 31 are finally tightened at this point, and the beams 30 in the adjacent sections are joined by the joining plate 31.

The amount of movement of the slab 1 by the jack 2 is the same as above, and when viewed along the direction of movement of the slab 1 (corresponding to the left-right direction of FIG. 9B), the total amount of movement of the slab 1 by the jack 2 (2x in the example of FIG. 9B) is preferably set to be 2×10 ⁻⁴ ×L/2 or more and 12×10 ⁻⁴ ×L/2 or less. Similarly to the above, L is the length from end to end of the slab 1 in all the sections in the above-described moving direction (see L in FIG. 9A). In addition, the moving amount of the slab 1 is determined according to the length of the slab 1 along the moving direction described above, and the concrete placing start date and the connecting date are substantially the same as those in the first embodiment.

Further, in the present embodiment, when the slab 1 of each section is supported by a plurality of seismic isolation devices 10, as shown in the plan view of FIG. Is desirable. Similarly to the above, if the number of seismic isolation devices 10 supporting the slabs 1 on both sides is different, when the slab 1 is moved by the jack 2 as described above, the slabs 1 on both sides do not move evenly, This is because the slab 1 with the smaller number of seismic isolation devices 10 moves greatly. The number of seismic isolation devices 10 in the central compartment may be different from the number of seismic isolation devices 10 in both compartments.

As described above, in the present embodiment, by moving the slabs 1 on both sides of the slab 1 in the central section and widening the interval between the slabs 1 in the adjacent sections, the same effect as that of the first embodiment can be obtained. can get. At this time, since the number of seismic isolation devices 10 supporting the slabs 1 on both sides is the same, the slabs 1 on both sides are moved evenly when the slabs 1 are widened using the jack 2. be able to.

The number of seismic isolation devices 10 of the slabs 1 on both sides is ideally the same as described above, but in practice, the number of seismic isolation devices 10 may be approximately the same, and may be slightly different. Here, the number of seismic isolation devices 10 being approximately the same means that the number of seismic isolation devices 10 of one slab 1 is N1 and the number of seismic isolation devices 10 of the other slab 1 is N2, and the error is 2×( When N1-N2)/(N1+N2), the error is in the range of -0.2 or more and 0.2 or less. This is because the difference (margin) between the maximum designed horizontal deformation amount of the seismic isolation device 10 and the limit horizontal deformation amount of the seismic isolation device 10 at the time of an earthquake response is about 100 mm, and about 50 mm which is half of the difference is targeted by the present invention. This is because, considering it as the limit of the amount of deformation due to the contraction of the body, 20% (0.2 times) of 10 mm can be judged as the error range. This also applies to the number of seismic isolation devices 10 of each slab 1 of the first embodiment.

The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and naturally, these also belong to the technical scope of the present invention. Understood.

1: Concrete slab 2: Jack 3: Packing material 10: Seismic isolation device 11; Reinforcing bar 20: Pillar 30: Beam 31: Joint plate 32: Bolt 33: Long hole

Claims (9)

Forming a concrete slab of multiple compartments supported via seismic isolation devices;
A step of moving at least one of the concrete slabs in the adjacent sections to increase the interval between the concrete slabs in the adjacent sections,
A step of filling the filling material between the concrete slabs in the adjacent sections,
A method for constructing a concrete slab, which comprises: The method for constructing a concrete slab according to claim 1, wherein both of the concrete slabs in adjacent sections are moved to widen the interval. The method for constructing a concrete slab according to claim 2, wherein the number of seismic isolation devices supporting the concrete slabs in the adjacent sections is substantially the same. The method for constructing a concrete slab according to claim 1, wherein the concrete slabs on both sides of the concrete slab in the central compartment are moved to widen the intervals. The method for constructing a concrete slab according to claim 4, characterized in that the number of seismic isolation devices supporting the concrete slabs in the sections on both sides is substantially the same. The average value of the daily average temperature of the filling start date of the filling material is lower than the average value of the average temperature of the casting start date of the concrete slab in at least one of the sections. Item 6. A method for constructing a concrete slab according to any one of Items 5. Within a predetermined period, at least the casting start date and the filling start date at which the difference obtained by subtracting the normal value of the daily average temperature of the filling start day from the normal value of the daily average temperature of the casting start date is the maximum, The method for constructing a concrete slab according to claim 6, wherein the placing of concrete of the concrete slab in any of the sections and the filling of the filling material are started respectively. When viewed along the moving direction of the concrete slab, the total amount of movement of the concrete slab is 2 × 10 ^-4 × L/, where L is the length from end to end of the concrete slab of all sections in the moving direction. The method for constructing a concrete slab according to any one of claims 1 to 7, which is 2 or more and 12 x 10 ^-4 x L/2 or less. The method for constructing a concrete slab according to any one of claims 1 to 8, wherein the moving amount of the concrete slab is determined according to the length of the concrete slab along the moving direction of the concrete slab.

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