JP4310794B2 - Anchor bolt and mobile formwork method using this anchor bolt - Google Patents

Description

  The present invention relates to an anchor bolt for a formwork in dam construction and a movable formwork method using the anchor bolt.

  The construction of a dam body in dam construction takes a lot of time and labor for the concrete placement work due to the size of the dam body. Therefore, it is required to work efficiently and quickly and to shorten the construction period.

  In general, a movable formwork method is adopted as a method for constructing a bank body in dam construction. The mobile formwork method is a method of constructing a concrete structure by moving a large formwork or stainless steel formwork unitized into a unit form. Mobile formwork methods include, for example, the “slide formwork method” in which concrete is cast while being moved up and down, the “jumping formwork method” in which concrete is moved one panel at a time after the concrete has hardened, and the median strip of the road `` Slip formwork method '' created by moving a continuous structure of the same shape laterally, etc., and used for structures with the same shape of cross-section, and the support work and the formwork are integrated. There are “traveling formwork method” and “self-raising dam formwork method” that rationalizes the movement of formwork in dam construction.

  The mobile formwork method often employs a structure that supports a load acting on the formwork by placing concrete in the next process by combining anchor bolts embedded in the existing concrete and the formwork. That is, the anchor bolt embedded in the existing concrete has a structure that supports the mold by resisting the load acting on the mold by the pulling shear force acting on the outer peripheral surface of the anchor bolt.

Here, conventionally, in order to increase the peripheral area of the anchor bolt, as the anchor bolt in the movable formwork method, one having a tip formed into a semicircular hook shape (hereinafter also referred to as a conventional anchor bolt) is used. (For example, refer to Patent Document 1). As a reference value, the time of demolding in the case of using conventional anchor bolts indicates that the compressive strength of concrete is 3.5 N / mm ² or more (concrete specification). That is, if the compressive strength of the concrete is 3.5 N / mm ² or more, the concrete adheres sufficiently to the anchor bolts embedded in the concrete and can resist the pulling force acting on the anchor bolts. The formwork can be supported and construction can be promoted.

Japanese Patent Laid-Open No. 10-212721 (FIG. 3)

By the way, considering that shortening the construction period of the levee leads to a significant shortening of the construction period, curing the concrete to a compressive strength of 3.5 N / mm ² means shortening the construction period. It was a hindrance.
However, with conventional anchor bolts, if the next process is performed before the concrete compressive strength reaches 3.5 N / mm ² , the concrete is not sufficiently adhered to the anchor bolts. I can't. That is, the pull-out resistance force of the conventional semi-circular hook-shaped anchor bolt corresponds to the adhesion strength of the anchor bolt peripheral surface to the concrete, so that the pull-out resistance can withstand the pull-out force acting on the anchor bolt. The structure requires a sufficient curing period to have strength.

  In addition, the method of shortening the time to the strength expression of concrete using early-strength Portland cement is also considered. However, when early strength Portland cement is used for mass concrete such as a dam body, it is difficult to adopt because it generates a lot of heat at the initial stage of curing and causes cracking.

  The present invention has been made to solve such a problem, and obtains the pulling resistance necessary for supporting the formwork even when the concrete is in a young age (small compressive strength). It is an object to provide an anchor bolt that can be used, and an object is to provide a movable formwork method using the anchor bolt.

The invention according to claim 1 is an anchor bolt for fixing a formwork used in a movable formwork method, which comprises a plate and an anchor bar, and the anchor bar extends vertically from the formwork. A bent portion formed by bending at a predetermined angle downward from the vertical portion, and one end of the anchor muscle is a fixing portion for fixing a mold, and the bending of the anchor muscle The plate is attached to the distal end side of the portion, and the plate resists the concrete around the bent portion of the anchor muscle so as to push up in the axial direction of the bent portion .

According to such a configuration, the anchor muscle has a bent portion bent downward from the vertical portion, and the bent portion is provided with the plate. Since the pulling shear force is generated and resists in the direction of pushing up the concrete around the bent portion in the axial direction, the pulling resistance can be further increased. Thereby, even if the compressive strength of concrete is small, sufficient pulling resistance can be obtained, and the mold can be reliably supported.

According to a second aspect of the present invention, in the movable formwork method in which concrete is sequentially cast from the lower side by a predetermined height, the lower part of the formwork is fixed to the anchor bolt according to the first aspect embedded in the existing concrete A second step of newly installing the anchor bolt according to claim 1 on the upper part of the mold, a third step of placing concrete in a part surrounded by the mold, and the concrete Including a fourth step of curing the mold for a certain period of time, a fifth step of removing the mold, and a sixth step of moving the mold upward.

According to this method, by using the anchor bolt according to the first aspect, it is possible to quickly obtain the pulling resistance required for the load acting on the mold. Therefore, since it is possible to demold and move the formwork and newly place concrete without waiting for the compressive strength of the placed concrete to be 3.5 N / mm ² , the construction period Can be shortened.

According to the present invention, with respect to extraction force acting on the A Nkaboruto, large pulling shearing force acts. For this reason, even if the concrete is in a young age state (a state in which the compressive strength is small), it is possible to obtain the pulling resistance necessary for supporting the formwork. Moreover, according to the formwork method using this anchor bolt, the formwork can be removed and moved at an early stage, and a new concrete can be placed. Therefore, the construction period can be shortened, and the construction cost can be reduced.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a view showing a side view when a formwork is installed on an anchor bolt according to the present embodiment embedded in existing concrete.
As shown in FIG. 1, the anchor bolt 1 includes an anchor bar 2 and a plate 3. One end of the anchor bar 2 is a fixing portion r that fixes the mold 10, and the plate 3 is connected to the other end. It is attached.

As shown in FIG. 1, the anchor bar 2 is bent at an angle (hereinafter referred to as “φ”) that opens downward from a line X perpendicular to the mold 10, for example, approximately 25 °. By bending the anchor muscles 2 in this way, the anchor muscles 2 can have a structure with a greater pulling resistance than linear anchor bolts. That is, in addition to the force that the anchor bar 2 resists in the X direction, a force that pushes the concrete C around the anchor bar 2 upward in the mold 10 (the axial direction of the bent portion) works. Resistance will increase.
The angle is not limited to 25 °, and may be in the range of 0 <φ <45 °, and more preferably 15 ° to 25 °.

  The anchor muscle 2 according to this embodiment uses a length of 40 cm and a diameter of 19 mm, but is not limited thereto, and depends on the size of the formwork, the amount of concrete placed, the composition and the curing period. Is set as appropriate.

The shape of the plate 3 is a square in this embodiment. The shape of the plate 3 is not limited to this, and may be square or circular.
Moreover, although the attachment angle of the plate 3 with respect to the anchor muscle 2 is perpendicular | vertical in this embodiment, it is not limited to this.

  A method for calculating the area of the plate 3 will be described later.

  Since the material of the anchor muscle 2 and the plate 3 needs to withstand the pulling force acting on the anchor bolt 1, a material having high rigidity is preferable. In this embodiment, steel is used.

Next, the structure of the mold will be described.
2A and 2B are views showing a formwork in the present embodiment, where FIG. 2A is a front view and FIG. 2B is a cross-sectional view.

As shown in FIG. 2, the mold 10 is vertically mounted on a plurality of vertical end members 11, 11 made of two lip groove type steels 11 a and 11 b, and the vertical end member 11. A framework is constituted by the four lateral end members 12 to be welded. The vertical end member 11 is provided with two lip groove steels 11a and 11b so that their webs face each other, and a gap slightly larger than the diameter of the insert cylinder 4 to be described later is provided.
On the concrete placement side of the vertical end member 11, a steel siding plate 13 that directly receives the concrete C is attached. The steel bracing plate 13 is engaged from the front side of the vertical end member 11 (opposite side of the placing side) by a pin 14 with a barb, and the pin head is nut-tightened and fixed to the vertical end member 11.

  The vertical length of the vertical end member 11 is about 4 m, for example, and the size of the steel slat is about 1.7 m in length and about 1.5 m in width.

  In addition, as shown to (a) and (b) of FIG. 2, the hole T which penetrates the insert cylinder 4 is provided in the upper part of the steel slat plate 13. As shown in FIG. In addition, since the vertical end member 11 is formed with a gap extending in the vertical direction in the lip groove steels 11a and 11b, the mounting position of the insert cylinder 4 and jack bolt 18 described later can be adjusted appropriately in the vertical direction. The positions where the insert cylinders 4 are inserted are the upper mounting position, the middle mounting position, and the position where the jack bolt 18 is installed, respectively.

Next, the coupling structure of the mold 10 and the anchor bolt 1 will be described with reference to FIGS.
As shown in FIG. 1, a hole j extending in the axial direction is provided at the tip of the insert tube 4 through which the vertical end member 11 and the steel support plate 13 are inserted. The diameter of the hole j is slightly larger than the diameter of the fixing portion r with the mold 10 positioned at one end of the anchor muscle 2, and the fixing portion r of the anchor muscle 2 is fitted into the hole j. Then, a flat washer 6 is fitted on the base end side of the insert cylinder 4, and the mold 10 and the anchor bolt 1 are coupled by tightening with a head nut 7 from the outside.

  In addition, the coupling | bonding method is used for the coupling | bonding of the insert cylinder 4 and the fixing | fixed part r of the anchor bolt 1. FIG. This is because fine adjustment of the angle of the mold 10 can be easily performed by giving some play to the coupling portion.

  The method for joining the anchor bolt 1 and the insert cylinder 4 is not limited to the fitting type, and is a structure in which a screw hole is formed in the insert cylinder 4 and a screw thread is formed in the fixing portion r and screwed together. Also good.

  An anchor hole 5 is formed around a fixed portion r of an anchor bolt 1 (hereinafter also referred to as a sea bolt S) embedded in concrete. The anchor hole 5 is a hole provided in the existing concrete C so as to wrap around the fixing portion r of the anchor bolt 1 by removing the insert cylinder 4 after the concrete C is hardened. Thereby, since the fixing | fixed part r of the anchor bolt 1 does not protrude from the finishing surface of the concrete C, the formwork 10 can be moved smoothly. Moreover, the aesthetics of a finished surface can be improved by filling the anchor hole 5 after removing the mold 10 with the filler.

<Construction method>
Next, the movable formwork method using the anchor bolt 1 will be described. This movable formwork construction method is a construction method in which concrete is sequentially placed from the lower side by a predetermined height. The first step of fixing the lower part of the formwork to the anchor bolt 1 embedded in the existing concrete, and the mold A second step of newly installing the anchor bolt 1 on the upper part of the frame, a third step of placing concrete in a portion surrounded by the mold, a fourth step of curing the concrete for a certain period of time, and the mold Including a fifth step of removing the mold and a sixth step of moving the mold upward.

<First step>
First, as shown in FIG. 3A, in a state in which the formwork 10 is lifted by the crane P, after the middle mounting position and the position of the anchor hole 5 are aligned, the insert cylinder 4 is inserted into the vertical end member 11. The insert cylinder 4 is fitted to the sea bolt S. Furthermore, the mold 10 is fixed to the sea bolt S by screwing the flat washer 6 and the head nut 7 at the base end of the insert cylinder 4.

Further, the jack bolt 18 is installed at the lower mounting position. The jack bolt 18 finely adjusts the angle of the mold 10 by adjusting the gap between the lower part of the mold 10 and the existing concrete C.
In FIG. 3 (a), the crane P is written small ignoring the scale in consideration of easy understanding of the drawing.

<Second step>
Next, as shown in FIG. 3B, anchor bolts 1 (hereinafter also referred to as dummy bolts D) are fixed to the upper part of the mold 10. The insert tube 4 is inserted into the upper mounting position, the flat washer 6 is fitted to the base end side of the insert tube 4, and the mold 10 and the insert tube 4 are fixed by the head nut 7. Then, the dummy bolt D is fixed to the mold 10 by fitting the fixing portion r of the dummy bolt D into the hole j provided inside the tip of the insert cylinder 4.

<Third step>
Next, as shown in FIG. 3C, fresh concrete f is placed in the portion surrounded by the mold 10. Here, existing concrete C (not shown) or form 10 (not shown) is installed on the opposite side of the form 10 and the front and back direction of the paper surface of FIG. 3, and the concrete placement space is enclosed. It is assumed that
The method for placing the mold 10 is not limited, and a known technique may be used. For example, in the present embodiment, the concrete f is placed using a distributor.

<4th process>
Next, as shown in FIG. 3 (d), after leveling the top surface of the placed concrete, it is cured for a certain period until the required strength is obtained. The curing period can be derived from the proportional relationship between the integrated temperature and the compressive strength by setting the required compressive strength. Moreover, you may determine a curing period, after creating a test body and performing a pull-out test in the field.

<5th process>
Next, as shown in FIG. 3E, when the set period has elapsed, the mold 10 is removed. First, the crane P is engaged with the hook of the crane P and the hook 19 provided at the upper end of the mold 10 so that the mold 10 can maintain the current height. Then, the head nut 7 and the flat washer 6 screwed to the dummy bolt D and the sea bolt S are removed, and the insert cylinder 4 is removed.

<6th process>
Next, using the crane P, the mold 10 is moved up to a position where the middle mounting position of the mold 10 and the anchor hole 5 ′ formed by the dummy bolt D are aligned (position in FIG. 3A in the next process). Let And it returns to a 1st process and the dam body is constructed by repeating the process mentioned above.

<Calculation method of plate surface area>
Next, a method for calculating the required surface area of the anchor bolt plate will be described. FIG. 4 is a view showing a load model according to the present embodiment, FIG. 4 (a) is a view showing a load model acting on the mold 10, and FIG. 4 (b) is with a plate. It is a model figure showing the shear resistance surface of the anchor bolt.
As shown in FIG. 4B, in the description of the method for calculating the surface area of the plate, a straight anchor bar 31 and a square plate 32 having a side of a are used (hereinafter, anchor bolts are plate-shaped). With anchor bolts 30).

  As shown in FIG. 4A, P represents a load acting on the mold 10, and T represents a pulling force acting on the anchor bolt 30 with a plate. In other words, the mobile formwork method according to the present embodiment has a structure in which the load P acting on the formwork 10 is resisted by the anchor bolt 30 with a plate embedded in the already-laid dam body side. Therefore, the load T acting on the anchor bolt 30 with a plate is represented by T = P · x / y. Here, T is a load (N) acting on the anchor bolt 30 with a plate, P is a concrete load (N) acting on the mold 10, and x is a lifted length (hatched portion (cm in FIG. 4) )), Y represents the lift length that has been placed + the lift length to be newly placed (the broken line portion (cm) in FIG. 4).

FIG. 4B is a model diagram showing a drawing shear resistance surface when the anchor bolt 30 with a plate is installed perpendicularly to the mold 10 and a load T is applied. a indicates the length of one side of the plate 32, and b indicates the length of the anchor muscle 31.
The anchor bolt 30 with a plate resists the load T by the resultant force of the pulling shear force t acting on the frustum-shaped peripheral surface extending 45 ° from the plate 32 toward the mold 10. The resultant force of the pulling shear force t is determined by the product of the area of the shear resistance surface (side area of the frustum shape) and the shearing force of the concrete (determined by the concrete mix and elapsed time). Therefore, the load T is represented by T = τ · M. Here, T represents the load (N) acting on the anchor bolt, τ represents the shear stress (N / cm ² ) of the concrete, and M represents the area (cm ² ) of the shear resistance surface.

Further, the area M of the shear resistance surface is expressed by M = 4 × {(a + b) × b / sin 45 °}. Here, a indicates the length of one side of the plate, and b indicates the length of the anchor muscle. The length b of the anchor bar is arbitrarily set according to the formwork (about 40 to 50 cm), and M is an existing value by M = T / τ, so that the side length a of the plate is obtained.
Therefore, the area A of the plate is obtained from A = a ² .

  In addition, when the anchor muscle 31 has an angle, the area of the plate 32 is calculated according to the angle.

[Pullout test]
<Summary>
Next, a pull-out test for demonstrating that sufficient necessary strength can be obtained according to the anchor bolt according to the present embodiment even when the material is young (in a state where the compressive strength is low) will be described.
A pull-out test was performed on the anchor bolt with plate according to the present embodiment and the conventional anchor bolt in which the tip of the anchor bar had a semicircular hook shape. The results are shown below.

As shown in FIG. 5, the anchor bolt test body uses an anchor bolt 40 with a plate and an anchor bolt having a semicircular hook at the tip (conventional anchor bolt (not shown)). The anchor bars 41 have a length of about 40 cm, a diameter of 19 mm, and a tensile yield strength of 345 N / mm ² , both of which are bent downward at approximately 20 °. The plate 42 is a square having a side of 10 cm. The plate 42 is attached perpendicular to the anchor bar 41. The material of the specimen is steel.

  Concrete is placed on the formwork to which these two types of anchor bolts are fixed, and a specimen is prepared. Then, a pull-out test is carried out for each test specimen (4 cases) after 24 hours and 48 hours. Prepare three anchor bolts each. The test cases are summarized in Table 1.

<Test method>
5A and 5B are diagrams showing a pull-out test method, where FIG. 5A is a front view and FIG. 5B is a side view.

As shown in FIG. 5, the anchor bolt pull-out test is performed by pulling out the anchor bolt 40 with a plate with a center hole jack 43.
The test apparatus has two H steels 44 as a base, and a square plate 45 is installed so as to straddle it. In the center of the square plate 45, a hole is provided through the tip of the center hole jack 43, and the tip of the center hole jack 43 and the end of the anchor bolt 40 with a plate embedded in concrete are connected. Has been. The center hole jack 43 is a hydraulic jack, and by adjusting the hydraulic pressure by the operation lever 47, a desired pulling load can be applied to the anchor bolt 40 with a plate. Further, the center hole jack 43 is provided with a load cell 46, and a load numerical value can be read from the data logger 48.
As shown in Table 2, the load is loaded in five stages.

<Preliminary test>
First, as a preliminary test, a compressive strength test was performed using a concrete specimen, and the relationship between the integrated temperature and the compressive strength was derived. The result is shown in FIG. The integrated temperature is an integrated value of the concrete temperature and time (days). The integrated temperature ΣT is represented by ΣT = Σ (10 + CT) Δt.
Here, T is the accumulated temperature (° C.), CT is the concrete temperature (° C.), and Δt is time or day. A coefficient of 10 indicates that the hydration reaction does not proceed when the concrete temperature is −10 ° C.

As shown in FIG. 6, since the strength expression of concrete depends on the integrated temperature of concrete, the compressive strength can be expressed as a function of the integrated temperature. The compressive strength Y is represented by Y = 0.024X−0.4685. Here, Y represents the compressive strength (N / mm ² ), and X represents the accumulated temperature.
Thereby, the relationship between elapsed time and compressive strength becomes clear.

<Test results>
Next, a tensile test was performed to examine the relationship between the pull-out load and the displacement of each anchor bolt.
FIG. 7 shows an example of test result data. A thick line M1 indicates the displacement of the anchor bolt 40 with a plate at each load stage. The white circle is a plot of the displacement of the anchor bolt with a plate at each load stage.
On the other hand, the thin line M2 shows a state where the load is released after the maximum load of about 23.5 kN is loaded and is left until there is no residual deformation. A black dot indicates a displacement of the anchor bolt 40 with a plate when the residual deformation is finished.

Here, if a force exceeding a certain limit is applied to the concrete, the deformation remains after the force is removed. This deformation is called residual deformation. This deformation per unit length is called residual strain, and in this test it is indicated by the difference between the displacement at the end of the residual deformation (when black circle) and the displacement at the first stage (when white circle).
In addition, since the amount of deformation of concrete is so small that this value is small, it means that the drawing-out resistance which acts on an anchor bolt is large.

FIG. 8 is a diagram showing the correlation between residual strain and compressive strength of each specimen based on a plurality of test data obtained by this test including the graph of FIG. A thick line L1 in FIG. 8 represents an anchor bolt 40 with a plate, and a thin line L2 represents a conventional anchor bolt. As shown in FIG. 8, a conventional anchor bolts, whereas the residual strain becomes zero is approximately 3.5 N / mm ^2, the plate with anchor bolts is about 2.5 N / mm ^2. Therefore, according to the anchor bolt 40 with a plate, the required strength can be obtained without waiting for the compressive strength of the concrete to be 3.5 N / mm ² .

The above can also be supported from the calculation formula.
For example, a calculation formula for a load acting on a linear anchor bolt (not shown) is represented by T = τ · L · a. Here, T is the load acting on the anchor bolt, τ is the concrete shear stress (N / cm ² ), L is the length of the anchor bar, and a is the circumference of the anchor bolt.
On the other hand, in the case of an anchor bolt with a plate, T = τ · M, as described above.
Here, if the load T and the length and diameter of the anchor bars are the same, the plate is attached, so the value of M is larger than the value of L · a. However, the value of τ is smaller. Here, since the shear stress τ of the concrete is proportional to the accumulated time (curing period) of the concrete, it is derived that the curing period may be shorter than before.

As described above, according to the anchor bolt 40 with a plate according to the present embodiment, the required strength can be obtained in a short time as compared with the conventional anchor bolt in which the tip of the anchor bar has a semicircular hook shape.
More specifically, for example, the required compressive strength of concrete when using conventional anchor bolts is set to 3.5 N / mm ^2, and the concrete when using the anchor bolts with plates 40 according to the present embodiment is used. The case where the necessary compressive strength is set to ^2.5 N / mm ² is compared.
Here, according to FIG. 6, the former accumulated temperature needs 1654 ° C., whereas the latter accumulated temperature is 1237 ° C. That is, it has been proved that the required strength can be obtained when about 75% of the conventional set curing period has elapsed. Therefore, according to the anchor bolt 40 with a plate which concerns on this embodiment, a curing period can be set short and required intensity | strength can be obtained.
Therefore, according to the anchor bolt 40 with a plate which concerns on this embodiment, since it leads to shortening of a curing period and by extension shortening of a construction period, construction cost can be reduced.

  As mentioned above, although embodiment of this invention was described in detail with reference to drawings, this invention is not limited to this, In the range which does not deviate from the meaning of this invention, it can change suitably.

  For example, the anchor muscle 2 may be bent upward or may be bent in the left-right direction (the front and back direction of the paper surface in FIG. 1).

It is a side view at the time of the anchor bolt and formwork which were embed | buried in concrete couple | bonded with this embodiment. It is a figure which shows the formwork which concerns on this embodiment, Comprising: (a) is a front view, (b) is sectional drawing. It is a figure showing each process figure of the formwork method concerning this embodiment. FIG. 4 is a view showing a load model according to the present embodiment, FIG. 4A is a view showing a load model acting on the mold 10, and FIG. 4B is a view with a plate. It is a model figure showing the shear resistance surface of the anchor bolt. It is a figure showing the test method of a drawing test. It is a graph showing the integrated temperature and compressive strength in the preliminary test of a drawing test. It is a graph showing an example of the test data of a drawing test. It is a figure showing the correlation of the residual distortion of a drawing test, and compressive strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anchor bolt 2 Anchor reinforcement 3 Plate 4 Insert cylinder 5 Anchor hole 6 Flat washer 7 Head nut 10 Formwork 11 Vertical end material 12 Horizontal end material 13 Steel slat plate 14 Pin with pin 18 Jack bolt D Dummy bolt r Fixed part S Sea bolt P crane T through hole

Claims (2)

An anchor bolt for fixing a formwork used in the mobile formwork method,
It consists of a plate and anchor muscle,
The anchor muscle has a vertical portion extending vertically from the formwork, and a bent portion formed by bending at a predetermined angle downward from the vertical portion,
One end of the Anchors are fixed portion for fixing the mold,
The plate is attached to the distal end side of the bent portion of the anchor muscle ,
The said plate resists the concrete around the said bending part of the said anchor reinforcement | strengthening so that it may push up in the axial direction of the said bending part . In the mobile formwork method, in which concrete is placed in order from the bottom at a predetermined height,
A first step of fixing the mold bottom to the anchor bolt according to claim 1 which is embedded in the existing concrete,
A second step of newly installing the anchor bolt according to claim 1 on the upper part of the mold;
A third step of placing concrete in the part surrounded by the formwork;
A fourth step of curing the concrete for a certain period of time;
A fifth step of demolding the mold,
And a sixth step of moving the mold upward.

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