KR102540408B1 - Retensioned PHC Pile and Construction Method for the same - Google Patents

Abstract

The present invention relates to a re-tensioned PHC pile which increases the shear strength and bending strength of an upper part of a pile, and to a construction method thereof. The re-tensioned PHC pile comprises: a filler; a mounting plate coupled to an upper part of the filler; a wedge barrel of a pipe shape formed with a thread; a mounting barrel formed with a screw groove; and a wedge installed between a hollow part of the wedge barrel and a PC steel rod.

Description

Retensioned PHC Pile and Construction Method for the Same}

The present invention relates to a re-tensioning PHC pile capable of restoring concrete prestress lost due to the removal of the tendon anchorage during the head preparation process of the pile and a construction method thereof, and more particularly, to a PHC that has the largest shear force and bending moment Re-tensioning PHC piles that increase the shear strength and flexural strength of the upper part of the pile by inserting intermittent circular reinforcing bars instead of continuous spiral wire at the top of the pile and restoring the lost concrete prestress through re-tensioning of the tension member after the head of the pile is straightened. It's about how it's built.

PHC pile (Prestressed Spun High Strength Concrete Pile) is one of the most widely used pile types in Korea because of its high bearing capacity and economic feasibility.

1 is a structural diagram of a typical PHC pile. Prestress is introduced into the concrete by the deformed PC steel bar tensioned at both ends, and the shear strength is reinforced by the continuous spiral wire welded to the PC steel bar.

Figure 2a shows a construction step in which the PC steel bar is exposed to the outside by removing the concrete at the top of the pile to connect the PHC pile embedded in the ground with the foundation concrete. The length of the PC steel bar normally exposed is about 35 times the diameter (D) of the steel bar. Since the anchoring part is removed in the process of exposing the PC steel bar to the outside, slip occurs between the PC steel bar and the concrete, and the concrete prestress is lost at the top of the pile. The length of the section where the slip phenomenon occurs is called a transfer length, and is usually about 50D. When the prestress disappears, the transition from prestressed concrete structure to reinforced concrete structure significantly reduces shear strength and flexural strength. In general, since the shear force and bending moment acting at the upper end of the pile are the largest, the performance degradation of the upper end makes it impossible to properly utilize the retention performance of the PHC pile.

Figure 2b is a drawing of Registered Patent No. 10-0444555 (head reinforcement method of prestressed concrete pile), which relates to a method of tensioning PC steel bars for restoring concrete prestress lost in the process of arranging the head of a pile. An anchorage wedge was used to tense the exposed PC steel bar, but since the wedge inevitably accompanies slip during the anchoring process, the PC steel bar was repeatedly tensioned and a wedge plate inserted to fix the anchorage slip ), a method for offsetting the loss of tension force was proposed. However, the anchoring activity of the wedge is usually about 6mm, but the total elongation of the PC steel bar (D=9.2mm) is about 2.5mm, which is the sum of 1.0mm of elongation within the transmission length and 1.5mm of the elongation of the exposed steel bar (35D). And the wedge activity must be gradually reduced through the insertion of the wedge plate, so the tension work is quite cumbersome. In this process, a fixation error of the thickness of the wedge plate is unavoidable, but since the total elongation is very small, even a small fixation error has a large effect, making it virtually impossible to introduce precise tension.

In addition, as can be seen in the photo of Figure 2c, the work of exposing the PC steel bar by crushing the concrete is quite rough, so it is easy to damage some PC steel bars. If the damaged PC steel bar is strained, it may break. If even one is broken, complete restoration of the prestress becomes impossible. In addition, since the head reinforcement is composed of an upper plate, a lower plate, and a support, there is a disadvantage in that the manufacturing cost is expensive.

Therefore, in order to solve the above problems, it is possible to precisely and easily perform the re-tensioning work of the PC steel bar for restoring the concrete prestress lost in the process of tidying up the head of the PHC pile, and the work of tidying up the head of the pile can also be easily performed. PHC piles and their construction methods are required.

The present invention has been made to solve the problems of the above-mentioned background art, and uses a fixing device and a tension system that can tension the PC steel bar exposed for bonding with the foundation concrete without loss of tension due to anchorage slip. By re-tensioning, the concrete prestress that is lost during the pile head preparation process is completely restored, and the structure is improved so that the shear strength of the upper part of the pile can be increased while making it possible to easily perform the exposure work of the PC steel bar during the pile head preparation process. It is to provide a re-tensioned PHC pile and its construction method.

As a means of solving the above problems, the present invention,

In the PHC pile including the PC steel bar, the shear reinforcing bar coupled to the PC steel bar, and the concrete for accommodating the PC steel bar and the shear reinforcing bar,

The shear reinforcing bar includes a spiral reinforcing bar disposed on the lower side of the PHC pile and a plurality of circular reinforcing bars installed at regular intervals on the upper side,

After the PHC pile is driven into the ground, a part of the concrete located on the top of the ground is removed to expose the PC steel bar,

A filler applied to the upper end of the remaining concrete after a portion of the concrete has been removed;

A fixing plate coupled to an upper portion of the filling material, made of steel, and having a through hole for penetrating the PC steel bar;

A pipe-shaped wedge barrel having a hollow portion formed to accommodate the exposed portion of the PC steel bar and having a thread formed on an outer circumferential surface thereof;

a fusing barrel having a screw groove connectable to the thread of the wedge barrel formed on an inner circumferential surface of the wedge barrel and screwed to the outer circumferential surface of the wedge barrel;

A wedge installed between the hollow part of the wedge barrel and the PC steel bar to fix the wedge barrel and the PC steel bar; includes,

In a state where the PC steel bar is fixed to the wedge barrel by the wedge and the wedge barrel and the fixing barrel are screwed together, the PC steel bar, the wedge barrel, the fixing barrel and the wedge assembly are lifted to the upper part of the PC steel bar and the fixation The barrel is moved in the direction of the fixing plate to maintain the state in which the tensile force is loaded on the PC steel bar,

When the wedge barrel and the fixing barrel are screwed together, the upper end of the wedge barrel is installed to be exposed upward compared to the upper end of the fixing barrel, and the lifting means is screwed with the upper end of the wedge barrel Re-tension PHC, characterized in that provide stakes

The PC steel rod may include a non-attached portion toward the upper end of the PHC pile and an attachment portion provided from the lower portion of the non-attached portion to the lower end of the PHC pile,

The PC steel bar may include an attachment portion toward the upper end of the PHC pile, a non-attachment portion formed over a predetermined distance from below the attachment portion, and an attachment portion provided from the lower portion of the non-attachment portion to the lower end of the PHC pile.

The lower end of the non-adherent portion is disposed lower than the lower end of the PC steel bar exposed when a portion of the upper portion of the concrete is removed, and the upper end of the non-adherent portion is disposed higher than the upper end of the PC steel bar exposed.

The lifting means includes a hydraulic jack including a hollow part and a ram; a chair supporting the hydraulic jack while in contact with the anchoring plate; One end is screwed with the wedge barrel to transmit the force loaded by the ram of the hydraulic jack to the PC steel bar, penetrates the hydraulic jack and the ram, and has a threaded hollow steel bar on the outer circumferential surface of the other end; a steel rod fixing plate coupled to the end of the ram; It is preferable to include; a fixing nut for fixing the other end of the hollow steel bar to the steel bar fixing plate.

A cross section of an outer circumferential surface of the fixing barrel is preferably a polygonal shape.

The PC steel bar includes a first steel bar disposed relatively upward and a second steel bar disposed relatively downward, and the first steel bar and the second steel bar are connected to each other, and the cross-sectional area of the first steel bar is the second steel bar. may be larger than the cross-sectional area of

A portion where the first and second steel rods are connected is preferably located in the attachment portion.

The first steel bar and the second steel bar may be connected by a threaded coupler,

A fixing plate is installed between the first steel bar and the second steel bar, and the lower end of the first steel bar and the upper end of the second steel bar may be fixed to the fixing plate, respectively.

The present invention also

A preparation step of preparing the aforementioned PHC pile;

Among the PHC piles prepared in the preparation step, PC steel bars, shear bars including spiral bars coupled to the PC steel bars but disposed on the lower side of the PHC piles and several circular bars installed at regular intervals on the upper side, the PC steel bars and shear bars An embedding step of embedding a PHC pile containing concrete into the ground;

A cleaning step of exposing a part of the PC steel rod by removing a part of the exposed upper end of the PHC pile inserted in the insertion step;

After the cleaning step, a fixing plate installation step of applying a filling material to the upper surface of the concrete at the top of the PHC pile and installing the fixing plate on top of the filling material, but installing the fixing plate in a state where the PC steel rod penetrates the through hole;

A screw coupling step of screwing the wedge barrel and the fusing barrel together;

A fixing step of fixing the wedge barrel and the PC steel bar by installing a wedge between the PC steel bar and the hollow portion in a state in which the PC steel bar is accommodated in the hollow portion of the wedge barrel;

The PC steel bar, wedge barrel, fixing barrel, and wedge are lifted to the upper part of the PC steel bar by the lifting means to load the PC steel bar with tensile force and move the fixing barrel in the direction of the fixing plate to load the PC steel bar with tensile force keep,

and a re-tensioning step in which the upper end of the wedge barrel is exposed upward compared to the upper end of the fixing barrel when the wedge barrel and the fixing barrel are screwed together, and the lifting means is screwed into the wedge barrel. It provides a PHC pile construction method.

The PC steel rod may include a non-attached portion toward the upper end of the PHC pile and an attachment portion provided from the lower portion of the non-attached portion to the lower end of the PHC pile,

The PC steel bar may include an attachment portion toward the upper end of the PHC pile, a non-attachment portion formed over a predetermined distance from below the attachment portion, and an attachment portion provided from the lower portion of the non-attachment portion to the lower end of the PHC pile.

The lower end of the non-adherent portion is disposed lower than the lower end of the PC steel bar exposed when a portion of the upper portion of the concrete is removed, and the upper end of the non-adherent portion is disposed higher than the upper end of the PC steel bar exposed.

The lifting means includes a hydraulic jack including a hollow part and a ram; a chair supporting the hydraulic jack while in contact with the anchoring plate; One end is screwed with the wedge barrel to transmit the force loaded by the ram of the hydraulic jack to the PC steel bar, penetrates the hydraulic jack and the ram, and has a threaded hollow steel bar on the outer circumferential surface of the other end; a steel rod fixing plate coupled to the end of the ram; It is preferable to include; a fixing nut for fixing the other end of the hollow steel bar to the steel bar fixing plate.

A cross section of an outer circumferential surface of the fixing barrel is preferably a polygonal shape.

The PC steel bar includes a first steel bar disposed relatively upward and a second steel bar disposed relatively downward, and the first steel bar and the second steel bar are connected to each other, and the cross-sectional area of the first steel bar is the second steel bar. may be larger than the cross-sectional area of

A portion where the first and second steel rods are connected is preferably located in the attachment portion.

The first steel bar and the second steel bar may be connected by a threaded coupler,

A fixing plate is installed between the first steel bar and the second steel bar, and the lower end of the first steel bar and the upper end of the second steel bar may be fixed to the fixing plate, respectively.

According to the present invention, the PC steel bar exposed for bonding with the foundation concrete is re-tensioned using an anchoring device and a tension system capable of tensioning without loss of tension due to anchorage slip, thereby reducing the concrete lost in the process of arranging the head of the pile. It is possible to provide a re-strength PHC pile with an improved structure and a construction method to fully restore the pre-stress and increase the shear strength of the upper part of the pile while being able to easily perform the exposure work of the PC steel bar during the head preparation of the pile. there is.

1 is a view showing a conventional PHC pile structure.
Figure 2a is a view showing a PHC pile with exposed PC steel rods for bonding with foundation concrete.
Figure 2b shows an example of a method of tensioning exposed PC steel rods of conventional PHC piles.
Figure 2c is a photograph of the PC steel rod exposure work of the conventional PHC pile.
Figure 3 is a view for explaining the attachment and non-attachment of the PC steel bar of the PHC pile according to one embodiment of the present invention.
Figure 4a is a view for explaining a method of connecting a first steel bar and a second steel bar using a threaded coupler.
Figure 4b is a view for explaining a method of connecting a first steel bar and a second steel bar using a fixing plate.
5 is a view for explaining the shear reinforcement arrangement of the PHC pile according to one embodiment of the present invention.
Figure 6a is an exploded perspective view for explaining a wedge barrel, a fixing barrel and a wedge of a PHC pile according to one embodiment of the present invention.
Fig. 6b is a cross-sectional view of the wedge barrel, fixing barrel and wedge shown in Fig. 6a;
7 is a view for explaining the arrangement step of the PHC pile construction method according to one embodiment of the present invention.
8 is a view for explaining in detail a method of re-tensioning a PC steel bar.
9 is a view for explaining the lifting means.
10 is a view for explaining a method of connecting a reinforcing bar to a PC steel bar.
Figure 11a is a view for explaining the change in tension force introduced in the case of using a PC steel bar including a non-adhesive portion.
Figure 11b is a view for explaining the change in tension force introduced in the case of using a PC steel bar including a first steel bar, a second steel bar, and a non-attached portion.
Figure 11c is a view for explaining the change in the tension force introduced in the case of connecting the first steel bar and the second steel bar using a fixing plate and using a PC steel bar including a non-adhesive portion.

Hereinafter, a re-tensioned PHC pile according to one embodiment of the present invention will be described with reference to the drawings.

Figure 3 is a view for explaining the attachment and non-attachment of the PC steel bar of the PHC pile according to one embodiment of the present invention, Figure 4a is a method for connecting the first steel bar and the second steel bar using a threaded coupler A drawing for explanation, Figure 4b is a view for explaining a method of connecting the first steel bar and the second steel bar using a fixing plate, Figure 5 explains the shear reinforcement arrangement of the PHC pile according to one embodiment of the present invention. Figure 6a is an exploded perspective view for explaining the wedge barrel, anchorage barrel and wedge of the PHC pile according to one embodiment of the present invention, Figure 6b is a combination of the wedge barrel, anchorage barrel and wedge shown in Figure 6a 8 is a view for explaining in detail the re-tension method of the PC steel bar, FIG. 9 is a view for explaining the lifting means, and FIG. 10 is a view for explaining the method of connecting the reinforcing bar to the PC steel bar.

The re-tensioned PHC pile according to this embodiment includes PC steel bar 10, shear reinforcing bar 20, concrete 30, filling material 31, anchoring plate 32, wedge barrel 40, anchoring barrel 50, Includes wedge (60).

In the state in which the PC steel bar 10 is combined with the shear reinforcing bar 20, tensile force is introduced into the PC steel bar 10 and it is accommodated in the concrete 30 and centrifugally formed is the same as a conventional PHC pile, but the PC steel bar 10 is There is a difference between the part or shape attached to the concrete 30 and the shape of the shear reinforcing bar 20, which will be described sequentially.

The upper part of the PC steel bar 10 is exposed as part of the concrete 30 exposed above the ground is removed after the PHC pile is driven into the ground, as shown in FIGS. 2a, 2b, and 7(d). .

As shown in FIG. 3, the PC steel bar 10 includes an attachment portion 10a and a non-attachment portion 10b.

The attachment part 10a is a part where the concrete 30 and the PC steel bar 10 are in direct contact and the PC steel bar 10 and the concrete 30 are attached, and the non-adhesive portion 10b is the PC steel bar 10 It is a part where the PC steel bar 10 and the concrete 30 are not attached by covering the coating 15 on the.

As shown in (a) of FIG. 3, the non-adhesive portion 10b is provided at the upper end of the PHC pile, and an attachment portion 10a may be provided from the lower portion of the non-attached portion 10b to the lower end of the PHC pile. As shown in (b), an attachment portion 10a is provided from a part of the upper end of the PHC pile and a lower portion of the non-attachment portion to the lower end of the PHC pile, and a non-attachment portion 10b is provided between the attachment parts 10a. It could be.

The lower end of the non-adhesive portion 10b is disposed lower than the lower end of the PC steel bar 10 exposed when a portion of the upper end of the concrete 30 is removed, and the upper end of the non-adhesive portion 10b is exposed to the PC steel bar. It is placed higher than the upper end of (10) (between C1 and C2). At this time, it is preferable to leave enough margin so that the exposed part of the PC steel bar 10 is always within the non-attached part after the head preparation of removing part of the upper end of the concrete 30 in consideration of the error in the ground penetration length of the PHC pile.

The reason for including the non-adhesive portion 10b is to facilitate the separation of the PC steel bar 10 and the concrete 30 when removing the upper part of the PHC pile and to introduce more prestress to the upper end of the PHC pile. It is to do.

Meanwhile, the PC steel bar 10 may include a first steel bar 11 and a second steel bar 12.

The first steel bar 11 is disposed relatively upper and the second steel bar 12 is disposed relatively lower, and the first steel bar 11 and the second steel bar 12 are connected to each other. In addition, the cross-sectional area of the first steel bar 11 is larger than that of the second steel bar 12.

The part where the first steel bar 11 and the second steel bar 12 are connected is located in the attachment part 10a, and as shown in FIG. The second steel bar 12 may be connected, and as shown in FIG. 4B, the lower end of the first steel bar 11 'and the upper end of the second steel bar 12' are alternately fixed to the annular fixing plate 72 It may be connected in a way that is not limited to the shown method, and can be selected from various methods such as a cold extrusion connection method. When using the fixing plate 72, the number of first steel bars 11 'and the number of second steel bars 12' may be varied, and discontinuous sizes of different sizes on both sides based on the fixing plate 72 Prestress can be introduced.

When the diameter (cross-sectional area) of the first steel bar 11 is larger than the diameter (cross-sectional area) of the second steel bar 12, a larger tension force can be introduced to the upper end of the PHC pile, but a relatively large bending moment acts It is possible to additionally reinforce the flexural strength of the upper side of the PHC pile. This will be described later in the section describing the construction method.

The shear reinforcing bar 20 includes a spiral reinforcing bar 21 and a circular reinforcing bar 22, as shown in FIG.

The spiral reinforcing bar 21 is disposed on the lower side of the PHC pile and is continuously installed while being welded to the PC steel bar 10, and the circular reinforcing bar 22 is disposed on the upper side of the PHC pile. The deformed reinforcing bar is processed into a circular shape and used .

Conventionally, spiral reinforcing bars were used for the entire PHC pile, but spiral reinforcing bars 21 cause considerable inconvenience when removing concrete in the process of arranging the head of the pile. Moreover, since the spiral reinforcement 21 has a smooth surface and a small diameter, there is a disadvantage in that it does not greatly help the shear reinforcement of the PHC pile.

Since the spiral reinforcing bar 21 has a small diameter and no nodes, it is usually called a spiral wire in order to distinguish it from a deformed reinforcing bar having a large diameter and nodes.

However, the deformed reinforcing bar used as the circular reinforcing bar 22 has excellent adhesion to the concrete 30 and has a large cross-sectional area, and can sufficiently increase the shear strength of the PHC pile. ) is fixed to the PC steel bar 10, it is also easy to separate the circular reinforcing bar 22 and the PC steel bar 10 during head cleaning. When determining the position of the concrete cutting surface for the head preparation of the PHC pile, the position of the circular reinforcing bar 22 is calculated by measuring the distance from the top of the pile or the position of the circular reinforcing bar 22 is determined using a reinforcing bar explorer, and the concrete cutting position is determined. It is possible to prevent overlapping with the circular reinforcing bar 22.

The filling material 31 is applied to the upper end of the remaining concrete after a portion of the concrete is removed, and fills the gap between the anchoring plate 32 and the uneven concrete surface because the cut surface of the concrete is not smooth. As the filling material 31, a material capable of exhibiting sufficient strength at an early stage while bonding heterogeneous members, such as epoxy, epoxy mortar, non-shrinkage mortar, etc., may be used.

The fixing plate 32 is a steel material coupled to the upper portion of the filling material 31 . The fixing plate 32 is formed with a through hole 33 (see FIG. 6A) through which the PC steel bar 10 passes.

The wedge barrel 40, the fixing barrel 50, and the wedge 60 are configured to apply tensile force to the PC steel bar 10 and fix it while maintaining the tensile force. Each configuration will be described in turn.

The wedge barrel 40 is a columnar shape having a hollow part 41 and includes a screw thread 42 formed on an outer circumferential surface. The hollow part 41 is a hole for accommodating the exposed portion of the PC steel bar 10. The cross-sectional shape of the outer circumferential surface of the cross section of the wedge barrel 40 is preferably circular, but may be a shape in which a part is removed from the circular shape. do.

The fixing barrel 50 has a columnar shape including a hollow portion and includes a threaded groove 51 formed on an inner circumferential surface of the hollow portion. The threaded groove 51 can be screwed with the thread 42 of the wedge barrel 40. prepared to be The cross section of the outer circumferential surface of the fixing barrel 50 is preferably made in a polygonal shape such as a hexagon because it is convenient to rotate it using a wrench or the like.

The wedge 60 is installed between the hollow part 41 and the PC steel bar 10 as a configuration for fixing the PC steel bar 10 to the wedge barrel 40. The wedge 60 is in the form of a wedge cone composed of two or three pieces.

In order to accommodate the wedge 60, an accommodating portion having a shape in which the cross section increases toward the top is formed at an upper end of the wedge barrel 40. Since the configuration related to the receiving portion for accommodating the wedge 60 is a technique generally used for fixing a steel bar or strand using a wedge, additional description will be omitted.

As shown in (c) of FIG. 8, the length of the wedge barrel 40 (length in the vertical direction when installed) is longer than the length of the fixing barrel 50, so that the wedge barrel 40 and the fixing barrel 50 are When coupled, it is preferable that the upper end of the wedge barrel 40 is installed so that it is exposed upward compared to the upper end of the fusing barrel 50. In this configuration, it is easy to screw the exposed part of the wedge barrel 40 and other members together. because it does Of course, even when the length of the wedge barrel 40 is the same as the length of the fusing barrel 50 or the fusing barrel 50 is longer, the upper end of the wedge barrel 40 can be fastened higher than the upper end of the fusing barrel 50. so there is no problem As such, when the upper end of the wedge barrel 40 is installed higher than the upper end of the fixing barrel 50, the lifting means for loading the tensile force of the PC steel bar 10 can be screwed to the upper end of the wedge barrel 40.

The PC steel bar 10 is fixed to the wedge barrel 40 by the wedge 60, and the PC steel bar 10 ), the wedge barrel 40, the fixing barrel 50 and the wedge 60 assembly are lifted toward the upper part of the PC steel bar and the fixing barrel 50 is moved in the direction of the fixing plate 32 to the PC steel bar 10 Maintain the loaded state of tension. The fixing barrel 50 may be rotated and moved in the direction of the fixing plate 32 .

When installing the wedge 60, it is preferable to lightly hit the wedge and bring it into close contact with the wedge barrel 40, as in a conventional wedge installation method, because the amount of tension can be reduced.

The lifting means 100 may use a hydraulic device, and an example of the lifting means 100 is shown in FIG. 9 . The lifting means 100 may include a chair 101, a hollow steel bar 102, a hydraulic jack 103, a steel bar fixing plate 105, and a fixing nut 106.

The chair 101 is configured to support the hydraulic jack 103 in a state in contact with the fixing plate 32.

The hydraulic jack 103 is a configuration for providing lifting force by hydraulic pressure, and includes a hollow part through which a hollow steel bar 102 can penetrate and a ram 104.

One end of the hollow steel bar 102 is screwed with the wedge barrel 40 to transmit the force loaded by the ram 104 of the hydraulic jack 103 to the PC steel bar 10 and penetrates the hydraulic jack 103, A thread 107 is formed on the outer circumferential surface of the other end.

The steel rod fixing plate 105 is a plate coupled to the end of the ram 104 of the hydraulic jack 103.

The fixing nut 105 is screwed to the thread 107 of the hollow steel bar 102 in order to transmit the lifting force by the ram 104 of the hydraulic jack 103 to the hollow steel bar 102, and the steel bar fixing plate 105 Adhering to and fixing the other end of the hollow steel bar 102 to the steel bar fixing plate 105.

Unlike the usual tensioning method in which a tension member such as a PC steel bar is bitten with a mechanical paper and a tensile force is applied directly to the tension member, using a hollow steel bar 102 screwed with the wedge barrel 40 is exposed as shown in FIG. 6B Tension is possible even when the length of the PC steel bar 10 is short, and tension is possible even when the length of the exposed PC steel bar 10 is long, as shown in FIG. In addition, if the fixing is done using the fixing barrel 50 after tension is completed, the problem of wedge action during fixing can be solved.

Figure 10 is a method that can be used when the length of the exposed PC steel bar 10 is short or damaged during the head clearance of the pile and the prescribed exposure length cannot be secured. After tension is completed, the exposed PC steel bar (10 ) and installing a threaded coupler 80 on the protrusion of the wedge barrel 40 to reinforce it by connecting it to the reinforcing bar. Since the tensile strength of the reinforcing bar is smaller than that of the PC steel bar, the cross-sectional area of the reinforcing bar is increased so that the cross-sectional area of the reinforcing bar and the tensile strength are multiplied by greater than the cross-sectional area of the PC steel bar (10) and the tensile strength. PC steel bar (10 ) can satisfy the exposure length regulations.

Hereinafter, one embodiment of a construction method for re-tensioning the PC steel bar 10 and maintaining the re-tensioned state while constructing the above-described PHC pile will be described with reference to the drawings.

Figure 7 is a view for explaining the arrangement step of the PHC pile construction method according to one embodiment of the present invention, Figure 8 is a fixing plate installation step, screw coupling step of the PHC pile construction method according to one embodiment of the present invention , a drawing for explaining the fixing step and the re-tensioning step, Figure 9 is a drawing for explaining the lifting means, Figure 11a is a drawing for explaining the change in the tension force introduced when using a PC steel bar including a non-attachment portion, Figure 11b is a view for explaining the change in the tension force introduced in the case of using a PC steel bar including a first steel bar, a second steel bar, and a non-attachment portion, Figure 11c is a view for explaining the first steel bar and the second steel bar using a fixing plate It is a diagram for explaining the change in tension force introduced when using a PC steel bar that is connected and includes a non-adhesive portion.

The PHC pile construction method according to this embodiment includes a preparation step, an insertion step, a cleanup step, a fixing plate installation step, a screw coupling step, a fixing step, and a re-tensioning step.

The preparing step is a step of preparing the aforementioned PHC pile. The PHC pile includes a PC steel bar (10), shear reinforcing bar (20), concrete (30), filling material (31), anchoring plate (32), wedge barrel (40), anchoring barrel (50), wedge (60) However, since each configuration has been described above, further description will be omitted.

The insertion step is coupled to the PC steel bar 10 and the PC steel bar 10, which are fixed in a state in which tensile force is applied among the PHC piles prepared in the preparation step, but the spiral reinforcement 21 disposed on the lower side of the PHC pile and the upper side determined Shear reinforcing bars 20 including circular reinforcing bars 22 installed at intervals, PHC piles containing concrete 30 accommodating the PC steel bars 10 and shear reinforcing bars 20 are inserted into the ground It is a step. It is possible to drill the ground using an auger and insert the PHC pile into the drilled part. The configuration for re-tensioning the PC steel bar 10 is inserted in an excluded state.

The cleaning step is a step of exposing a part (top part) of the PC steel bar 10 by removing a part of the upper end of the PHC pile inserted in the insertion step.

7 is a diagram for explaining a cleaning step. First, as shown in (a) of FIG. 7, the upper end of the PHC pile is cut in a one-cutting manner. C1 is a position where the circular cutting is performed, and the head of the PHC pile is cut in consideration of the exposed length of the PC steel bar 10. Since the tensile force of the PC steel bar 10 is as large as 7 to 10 tons, cutting the non-attached portion 10b of the PC steel bar 10 may cause the PC steel bar 10 at the top to protrude, resulting in a dangerous situation. In order to do this, it is preferable to place the attachment portion 10a on top of the non-attachment portion 10b to prevent the PC steel bar 10 being tensed from protruding out.

As shown in (b) of FIG. 7, when the head of the PHC pile is removed by the one-cutting method, a groove is formed on the outside of the concrete in the portion marked C2, and as shown in (c), the top of the PHC pile is impacted. After cutting the concrete by generating a through crack by applying a through crack, the upper part of the pile is removed as shown in (d). At this time, since the PC steel bar 10 in the portion marked C2 is a non-adhesive portion 10b, the concrete can be easily cut. By one-cutting, the prestress introduced by the PC steel bar 10 is lost, and since the PC steel bar 10 is not attached to the concrete and there is no shear reinforcing bar, the concrete can be cut even with a small impact. In addition, since the concrete between C1 and C2 is not attached to the PC steel bar 10, it can be pulled out using an appropriate lifting device and can be removed without crushing the concrete.

The fixing plate installation step is a step of applying the filling material 31 to the upper surface of the concrete at the top of the PHC pile after the cleaning step and installing the fixing plate 32 on top of the filling material 31. Since the cut surface of the PHC pile in the preparation stage is not smooth, the filling material 31 is filled between the anchoring plate and the upper surface of the irregular concrete before installing the anchoring plate 32. In the drawing, the lower surface of the filling material 31 is shown as being flat, which is for convenience of illustration, and in reality, an irregular cut surface is formed.

Figure 8 (a) shows the state in which the cleaning step is completed, and as shown in Figure 8 (b), the filling material 31 and the fixing plate 32 are installed. Since the through hole 33 is formed in the fixing plate 32, the fixing plate 32 is installed in a state where the exposed PC steel bar 10 passes through the through hole 33.

The screw coupling step is a step of screw coupling the wedge barrel 40 and the fusing barrel 50 together. Screwing the wedge barrel 40 and the fixing barrel 50 is irrelevant at any time prior to the fixing step.

In the fixing step, a wedge 60 is installed between the PC steel bar 10 and the hollow part 41 in a state where the PC steel bar 10 is accommodated in the hollow part 41 of the wedge barrel 40, so that the PC steel bar (10) is fixed to the wedge barrel (40). At this time, it is preferable to lightly hit the wedge 60 to bring the wedge into close contact with the wedge barrel 40 because it can reduce the amount of tension. The state in which the fixing step is completed is shown in (c) of FIG. 8 .

The re-tensioning step is a step of loading a tensile force on the PC steel bar 10 from which the tension is relieved in the arranging step and maintaining the loaded state.

To this end, the assembly of the PC steel bar 10, the wedge barrel 40, the fixing barrel 50, and the wedge 60 is lifted toward the upper part of the PC steel bar to load the PC steel bar 10 with a tensile force.

When a tensile force is applied to the assembly, elongation and wedge slip of the PC steel bar 10 occur simultaneously. The amount of tension is the sum of the elongation of the PC steel bar and the wedge action. 8(d) shows a state in which the assembly is lifted. In (d) of FIG. 8, only the hollow steel bar 102 of the lifting means 100 is shown, which is for convenience in illustration.

When tensile force is applied to the assembly and the tensile force is introduced to the PC steel bar 10, the fixing barrel 50 is rotated and moved in the direction of the fixing plate to fix the PC steel bar 10. If the fixing barrel 50 is tightened with sufficient torque and brought into close contact with the fixing plate 32, the tensioned state can be maintained intact even when the tension is removed. Since the wedge action is completed during tension by the hollow steel bar 102, no additional wedge action occurs, unlike the usual method of biting and tensioning the tension member. 8(e) shows a state in which the fixing barrel 50 is in close contact with the fixing plate 32, that is, a state in which the PC steel bar 10 is fixed in a state in which tensile force is loaded.

After settling by the fixing barrel 50, the hollow steel bar 102 is dismantled, and when the re-tensioning step is completed as shown in FIG. 8(f), the PC steel bar 10 of the PHC pile is re-tensioned The construction of the PHC piles is complete.

Hereinafter, a change in tension force introduced when a non-attached PC steel bar is used in the upper part of the PHC pile will be described with reference to FIGS. 11A to 11C.

Figure 11a is a case where the coating is covered on the upper part of the PC steel bar 10 having a constant diameter. The tension introduced during the manufacture of the PHC pile disappears in the non-attached portion 10b due to the cutting of the steel bar during the pile head preparation, and the adhesive force is generated as the steel bar slides from the starting point of the attachment portion 10a. The sliding of the steel bar stops when the cumulative sum of the attachment forces becomes equal to the tension force. The change in tension within the transmission length (La) is shown as a linear change for convenience, but actually changes in a parabolic shape. If the PC steel bar 10 is re-tensioned after the head is straightened, the tension at the time of manufacture can be restored.

11B is a view for explaining the change in tension force when steel bars having different cross-sectional areas are connected with a coupler 71 as shown in FIG. 4A, and a steel bar having a diameter of 13 mm is used as the first steel bar 11, and the second As the steel bar 12, it is an example using a steel bar having a diameter of 9.2 mm. When the pile is manufactured, the second steel bar 12 having a small diameter (9.2 mm) is tensioned with the maximum allowable tension. When a part of the upper end of the steel bar is cut during the head straightening process, the tension of the non-adhesive portion 10b disappears and a shear length La section is formed from the non-adherent boundary portion. Since the tension force that the first steel bar 11 of large diameter (13 mm) can accommodate is greater than the initial tension force, when the steel bar is re-tensioned with a force greater than the initial tension force, the fixation length Lb longer than the shear length La is formed The name of the length of the section where the tension force changes due to the occurrence of adhesion force is changed to the transmission length and the development length is that when slippage occurs between the concrete and the steel rod, the axial force of the steel rod decreases within the shear length (La) and Poisson ( Poisson) effect, the cross-sectional area expands and the adhesion increases, and within the anchorage length (Lb), the axial force of the steel bar increases while the cross-sectional area shrinks and the adhesive force decreases. because the characteristics are the same. If the fixing length goes beyond the threaded coupler 71 to the second steel bar section of small diameter (9.2 mm), the stress of the small diameter steel bar may exceed the allowable stress, so be sure to use the large diameter (13 mm) first steel bar (11 ) should be longer than the anchorage length (Lb).

FIG. 11C is a diagram for explaining a change in tension in the case where a fixing plate 72 is present as shown in FIG. 4B. This is an example in which a steel bar having a diameter of 13 mm is used as the first steel bar 11 and a steel bar having a diameter of 9.2 mm is used as the second steel bar 12 . Since the fixing plate 72 can fully fix the tension by itself, the attachment portion 10a and the non-adhesion portion 10b may be formed based on the fixation plate 72 . When a part of the upper end of the steel bar is cut, the initial tension of the first steel bar 11 of the non-adhesive portion 10b disappears. After the head is straightened, if the first steel bar 11 of large diameter (13 mm) is tensioned with the maximum tension that can be allowed, a large tension can be introduced to the top of the pile. At this time, since the tension is fixed by the fixing plate 72, discontinuous tension is applied.

As described above, in the present invention, circular reinforcing bars 22 made of deformed reinforcing bars are arranged at predetermined intervals instead of spiral reinforcing bars 21 at the top of the PHC pile where a large shear force acts, but they are bound without welding to the PC steel bar 10. By doing so, the shear strength is improved and the head cleaning work is facilitated. In addition, in the section where the cut surface can be formed during the head preparation of the pile, the PC steel bar 10 is made into a non-attached portion 10b so that the PC steel bar 10 and the concrete 30 can be separated without crushing the concrete. Doing so makes head cleaning work easier and damage to the PC steel bar 10 can be minimized. Consisting of anchorage devices (wedge barrel 40, anchorage barrel 50 and wedge 60) that can solve the anchorage slip problem, hollow steel bar 102, chair 101, and hydraulic jack 103 By tensioning using the lifting means 100, it is possible to introduce precise tension to the PC steel bar 10.

In the above, specific details for the implementation of the present invention have been provided by describing preferred embodiments of the present invention, but the technical spirit of the present invention is not limited to the described embodiments, and various forms are included within the scope of the technical spirit of the present invention. can be materialized.

10: PC steel bar 20: Shear reinforcing bar
30: concrete 40: wedge barrel
50: settling barrel 60: wedge

Claims (20)

In the PHC pile including the PC steel bar, the shear reinforcing bar coupled to the PC steel bar, and the concrete for accommodating the PC steel bar and the shear reinforcing bar,
The shear reinforcing bar includes a spiral reinforcing bar disposed on the lower side of the PHC pile and a plurality of circular reinforcing bars installed at regular intervals on the upper side,
After the PHC pile is driven into the ground, a part of the concrete located on the top of the ground is removed to expose the PC steel bar,
A filler applied to the upper end of the remaining concrete after a portion of the concrete has been removed;
A fixing plate coupled to an upper portion of the filling material, made of steel, and having a through hole for penetrating the PC steel bar;
A pipe-shaped wedge barrel having a hollow portion formed to accommodate the exposed portion of the PC steel bar and having a thread formed on an outer circumferential surface thereof;
a fixing barrel having a screw groove connectable to the screw thread of the wedge barrel formed on its inner circumferential surface and screwed to the outer circumferential surface of the wedge barrel;
A wedge installed between the hollow part of the wedge barrel and the PC steel bar to fix the wedge barrel and the PC steel bar; includes,
In a state where the PC steel bar is fixed to the wedge barrel by the wedge and the wedge barrel and the fixing barrel are screwed together, the PC steel bar, the wedge barrel, the fixing barrel and the wedge assembly are lifted toward the upper part of the PC steel bar and the fixation The barrel is moved in the direction of the fixing plate to maintain the state in which the tensile force is loaded on the PC steel bar,
When the wedge barrel and the fixing barrel are screwed together, the upper end of the wedge barrel is installed to be exposed upward compared to the upper end of the fixing barrel, and the lifting means is screwed to the upper end of the wedge barrel,
The PC steel bar includes an attachment part at the upper end of the PHC pile, a non-attachment part formed over a certain distance from the bottom of the attachment part, and an attachment part provided from the bottom of the non-attachment part to the lower end of the PHC pile. Retension PHC stakes made.
delete delete According to claim 1,
The lower end of the non-adhesive portion is lower than the lower end of the PC steel bar exposed when a portion of the upper end of the concrete is removed, and the upper end of the non-adhesive portion is higher than the upper end of the PC steel bar exposed. Characterized in that Retension PHC stakes.
According to claim 1,
The lifting means,
A hydraulic jack including a hollow part and a ram;
a chair supporting the hydraulic jack while in contact with the anchoring plate;
One end is screwed with the wedge barrel to transmit the force loaded by the ram of the hydraulic jack to the PC steel bar, penetrates the hydraulic jack and the ram, and has a threaded hollow steel bar on the outer circumferential surface of the other end;
a steel rod fixing plate coupled to the end of the ram;
A re-tension PHC pile comprising a fixing nut for fixing the other end of the hollow steel bar to the steel bar fixing plate.
According to claim 1,
The re-tension PHC pile, characterized in that the cross section of the outer circumferential surface of the fixation barrel is a polygon.
According to claim 1,
The PC steel bar includes a first steel bar disposed relatively upward and a second steel bar disposed relatively downward, and the first steel bar and the second steel bar are connected to each other, and the cross-sectional area of the first steel bar is the second steel bar. Re-strength PHC pile, characterized in that it is large compared to the cross-sectional area of.
According to claim 7,
Re-tensioning PHC pile, characterized in that the portion where the first steel bar and the second steel bar are connected is located in the attachment part.
According to claim 8,
The first steel bar and the second steel bar are re-tensioned PHC piles, characterized in that connected by a threaded coupler.
According to claim 8,
A fixing plate is installed between the first steel bar and the second steel bar, and the lower end of the first steel bar and the upper end of the second steel bar are fixed to the fixing plate, respectively.
Preparation step of preparing the PHC pile of claim 1;
Among the PHC piles prepared in the preparation step, PC steel bars, shear bars including spiral bars coupled to the PC steel bars but disposed on the lower side of the PHC piles and several circular bars installed at regular intervals on the upper side, the PC steel bars and shear bars An embedding step of embedding a PHC pile containing concrete into the ground;
A cleaning step of exposing a part of the PC steel rod by removing a part of the exposed upper end of the PHC pile inserted in the insertion step;
After the cleaning step, a fixing plate installation step of applying a filling material to the upper surface of the concrete at the top of the PHC pile and installing the fixing plate on top of the filling material, but installing the fixing plate in a state where the PC steel rod penetrates the through hole;
A screw coupling step of screwing the wedge barrel and the fusing barrel together;
A fixing step of fixing the wedge barrel and the PC steel bar by installing a wedge between the PC steel bar and the hollow portion in a state in which the PC steel bar is accommodated in the hollow portion of the wedge barrel;
The PC steel bar, wedge barrel, fixing barrel, and wedge are lifted to the upper part of the PC steel bar by the lifting means to load the PC steel bar with tensile force and move the fixing barrel in the direction of the fixing plate to load the PC steel bar with tensile force keep,
When the wedge barrel and the fixing barrel are screwed together, the upper end of the wedge barrel is installed so as to be exposed upward compared to the upper end of the fixing barrel, and the lifting means is screwed into the wedge barrel.
The PC steel bar includes an attachment part at the upper end of the PHC pile, a non-attachment part formed over a certain distance from the bottom of the attachment part, and an attachment part provided from the bottom of the non-attachment part to the lower end of the PHC pile. How to construct PHC piles.
delete delete According to claim 11,
The lower end of the non-adhesive portion is lower than the lower end of the PC steel bar exposed when a portion of the upper end of the concrete is removed, and the upper end of the non-adhesive portion is higher than the upper end of the PC steel bar exposed. Characterized in that PHC pile construction method.
According to claim 11,
The lifting means,
A hydraulic jack including a hollow part and a ram;
a chair supporting the hydraulic jack while in contact with the anchoring plate;
One end is screwed with the wedge barrel to transmit the force loaded by the ram of the hydraulic jack to the PC steel bar, penetrates the hydraulic jack and the ram, and has a threaded hollow steel bar on the outer circumferential surface of the other end;
a steel rod fixing plate coupled to the end of the ram;
PHC pile construction method comprising a; fixing nut for fixing the other end of the hollow steel bar to the steel bar fixing plate.
According to claim 11,
PHC pile construction method, characterized in that the outer circumferential surface of the fixation barrel is a polygon.
According to claim 11,
The PC steel bar includes a first steel bar disposed relatively upward and a second steel bar disposed relatively downward, and the first steel bar and the second steel bar are connected to each other, and the cross-sectional area of the first steel bar is the second steel bar. PHC pile construction method, characterized in that it is larger than the cross-sectional area of.
According to claim 17,
The PHC pile construction method, characterized in that the portion where the first steel rod and the second steel rod are connected is located in the attachment portion.
According to claim 18,
The PHC pile construction method, characterized in that the first steel bar and the second steel bar are connected by a threaded coupler.
According to claim 18,
A fixing plate is installed between the first steel bar and the second steel bar, and the lower end of the first steel bar and the upper end of the second steel bar are fixed to the fixing plate, respectively.

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