Method of using temporary reinforcing ring

Abstract

To provide a method of using a temporary reinforcing ring that can improve safety of construction work such as assembling and erecting a reinforcement cage for a cast-in-place pile.SOLUTION: A method of using a temporary reinforcing ring includes: a process of, when assembling a reinforcement cage for a cast-in-place pile comprising a plurality of main reinforcements arranged around a central axis approximately parallel to a direction of the central axis, a plurality of hoop reinforcements arranged in a circumferential direction approximately perpendicular to the central axis and having intersections with the plurality of main reinforcements, and a plurality of reinforcing rings arranged inside or outside the plurality of main reinforcements and having intersections with the plurality of main reinforcements, attaching the temporary reinforcing ring with reinforcing bar fixing hardware to a main reinforcement connection portion for connecting the reinforcement cages together or to a main reinforcement anchor portion exposed from a pile head of the cast-in-place pile; and a process of removing the temporary reinforcing ring together with the reinforcing bar fixing hardware during or after erection of the reinforcement cage.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for using a temporary reinforcing ring, and more particularly to a method for using a temporary reinforcing ring for a reinforcing cage of a cast-in-place pile. [Background technology]

[0002] At construction sites, a common method is to drive piles into the ground to form pile foundations that support the structure in order to increase the structure's earthquake resistance. One method of pile foundation construction is the cast-in-place pile method. A cast-in-place pile is a pile in which a cylindrically assembled rebar cage is placed in an excavated pile hole, and after the cage is placed, concrete is poured into the hole and allowed to harden. There are several known cast-in-place pile construction methods, such as the all-casing method, earth drill method, and reverse method, which differ in the method of excavating the ground.

[0003] In the past, the rebar cages required for constructing cast-in-place piles were often assembled by temporary welding. However, after the Great Hanshin-Awaji Earthquake in 1995, many fractures were observed in the main reinforcement welds near the surface of cast-in-place piles, and so a non-welding method for constructing rebar cages without welding was introduced.

[0004] Then, in March 2012, after the Great East Japan Earthquake of 2011, the "Highway Bridge Specifications and Commentary" (Japan Road Association) was revised, and the proviso to (1) of "19.8 Fabrication and Erection of Reinforced Concrete Cages" read, "...However, when assembling the reinforcing bars, welding for the purpose of maintaining the shape during assembly, etc., shall not be used." The commentary added, "...because welding...makes it difficult to ensure construction quality and may result in defects such as a reduction in the cross-sectional area of the reinforcing bars...," thus stipulating that direct welding of the main reinforcing bars, which are the main components of reinforcing concrete cages, shall not be used. For this reason, no-welding methods are now being adopted. Reinforcing concrete cages fabricated using such no-welding methods are disclosed, for example, in the following Patent Documents 1 to 3.

[0005] For reinforcing cages manufactured using this type of non-welding method, it is recommended that consideration be given to maintaining the shape of the reinforcing cage and ensuring safety during erection, in accordance with the "Guidelines for the Design and Construction of Non-Welding Methods for Reinforcing Cages for Cast-in-Place Concrete Piles" published by the Japan Foundation Foundation Association.

[0006] In non-welding construction, the fixing strength of the mounting brackets used is weaker than with welding, so the reinforcing frame (also called reinforcing ring) used as assembly rebar, which is responsible for evenly distributing the load, plays an important role in maintaining the shape of the reinforcing bar cage and preventing buckling.The above-mentioned Road Bridge Specifications state that "The diameter and arrangement of the assembly reinforcing bar will vary depending on the size and weight of the reinforcing bar cage, but it is generally best to use reinforcing bars with a diameter of about 22 mm and place them at intervals of 2 to 3 meters."

[0007] [Problem to be solved by the invention] In recent years, in order to withstand large earthquakes, the diameter and number of reinforcing bars in the pile head cages, which are particularly susceptible to horizontal forces during earthquakes, have increased significantly, and the excessive load at the pile head is now supported by the same main reinforcement bars at the base as before, that is, by a reinforcing bar cage made up of smaller diameter and fewer main reinforcements than the reinforcing bar cage at the pile head.In addition, extra-large diameter main reinforcement bars such as D51, which were rarely used in the past, and large diameter ties (also called hoop reinforcement) such as D32 and D35, are now being used, and pile lengths have also changed significantly from reaching the intermediate bearing layer to reaching deeper bearing layers, resulting in significant changes in the arrangement of reinforcement and the structure of the pile itself from the days of the traditional welding method.

[0008] Compared to the reinforcement arrangement of conventional rebar cages, the reinforcement arrangement of current rebar cages has become unprecedented, with the diameter and number of main bars and hoop bars, and the size of reinforcing rings increasing.The rebar cages are also becoming heavier and larger in diameter, making construction more difficult to the point that past experience is completely useless.

[0009] Compared to conventional welding methods, welding-free metal fittings have the disadvantages of not being integrated, having weak fixing strength, and the fixing position shifting. Therefore, for safe construction, it is necessary to understand the limits (allowable bearing capacity) of welding-free metal fittings and distribute the load (hanging load) evenly while leaving a margin for this allowable bearing capacity.

[0010] However, the lifting load during erection has increased dramatically by several times compared to the days of conventional welding methods, which has led to an increased need to use stronger materials, such as wider ring members, for the top reinforcing ring to which the lifting equipment is attached during erection. However, as mentioned above, the diameter and number of not only the main reinforcement but also the hoop reinforcement have increased in current reinforcing cages, and the spacing between the hoop reinforcement has become very narrow.In addition, due to constraints such as the hooks formed when installing the hoop reinforcement, it has become difficult to arrange wider reinforcing rings than before, which has been an issue.

[0011] In addition, in recent years, in order to be able to cope with horizontal forces during earthquakes as much as possible, there has been an increase in designs in which the arrangement of the main reinforcement bars of the reinforcing bar cage is shifted in the axial direction (up and down) and the connection points between the main reinforcement bars at the connecting parts (ends) of the reinforcing bar cage are shifted in the axial direction (up and down), rather than connecting the reinforcing bar cages together, i.e., connecting the main reinforcement bars together at the same height (same row) (commonly known as lug joints). In the area where the reinforcing cages connect, no hoops or reinforcing rings are installed, and the structure is made up of only main reinforcement bars, so as not to interfere with the connection between the main reinforcement bars. In a reinforcing bar cage with the above-mentioned structure in which the arrangement of the main reinforcement bars is shifted in the axial direction, the area that forms the connecting portion becomes longer, and there is a problem that the reinforcing bar cage may not be able to maintain its cylindrical shape and may become deformed, for example, when assembling, storing, or moving the reinforcing bar cage in a sideways position. In addition, the reinforcing bar cage placed at the pile head has an area consisting only of main reinforcement, which serves as an anchor part for exposing the main reinforcement from the pile head. However, as the reinforcing bar cage at the pile head becomes heavier and larger in diameter, the area that serves as this anchor part also becomes longer, and as mentioned above, there is a problem that the reinforcing bar cage may not be able to maintain its cylindrical shape and may become deformed when assembled, stored, or moved in a sideways position.

[0012] As a result of the increasing weight and diameter of the reinforcing bar cages, and the increasing diameter and density of the main reinforcement and hoop reinforcement, the construction of cast-in-place piles is becoming more difficult, and there has been a problem in that it is becoming difficult to ensure safety during construction using conventional construction methods. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Patent No. 5382394 [Patent Document 2] Patent No. 3914897 [Patent Document 3] Patent No. 5711504 Summary of the Invention Means to solve the problem and their effects

[0014] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a method of using a temporary reinforcement ring that can improve the safety of construction work such as assembling and installing reinforcing cages for cast-in-place piles.

[0015] In order to achieve the above object, a method (1) for using the temporary reinforcement ring according to the present invention includes, during the assembly work of a reinforcing bar cage for a cast-in-place pile, the reinforcing bar cage having a plurality of main reinforcements arranged around a central axis substantially parallel to the direction of the central axis, a plurality of hoop reinforcements arranged in a circumferential direction substantially perpendicular to the central axis and having intersections with the plurality of main reinforcements, and a plurality of reinforcing rings arranged inside or outside the plurality of main reinforcements and having intersections with the plurality of main reinforcements, a step (attachment step) of attaching the temporary reinforcement ring with a reinforcing bar fixing metal fitting to a main reinforcement connecting portion for connecting the reinforcing bar cages together or to a main reinforcement anchor portion exposed from the pile head of the cast-in-place pile; The method is characterized by including a step (removal step) of removing the temporary reinforcement ring together with the reinforcing bar fixing metal fittings during or after the installation work of the reinforcing bar cage.

[0016] According to the above-mentioned method (1) of using the temporary reinforcement ring, the installation process involves attaching the temporary reinforcement ring to the main reinforcement connection part or the main reinforcement anchor part with the reinforcing bar fixing metal fittings during the assembly work of the reinforcing bar cage. Therefore, even if the area that becomes the main reinforcement connection part or the main reinforcement anchor part becomes longer due to the weight or diameter of the reinforcing bar cage increasing, deformation of the reinforcing bar cage can be prevented when the reinforcing bar cage is assembled in a sideways position, during storage, or when it is moved, thereby increasing safety during construction. Furthermore, even if the lifting load during the installation work of the reinforcing bar cage becomes excessive due to the weight and diameter of the reinforcing bar cage, the temporary reinforcement ring is attached to the main reinforcement connection part and the main reinforcement anchor part, so the load burden on the intersection part between the reinforcing ring and the main reinforcement can be reduced, and safety during installation can be increased. In addition, the removal process allows the temporary reinforcement ring to be removed along with the reinforcing bar fixing hardware during or after the installation of the reinforcing bar cage, so that the temporary reinforcement ring and the reinforcing bar fixing hardware do not hinder subsequent work, making it possible to safely install the cast-in-place piles.

[0017] In addition, the method (2) of using a temporary reinforcement ring according to the present invention is characterized in that, in the above-mentioned method (1) of using a temporary reinforcement ring, the reinforcing bar fixing fittings are fixed in multiple stages at the intersection between the main reinforcement and the temporary reinforcement ring.

[0018] According to the above-mentioned method (2) of using the temporary reinforcement ring, the allowable bearing capacity of the reinforcing bar fixing metal fittings can be reinforced by fixing the reinforcing bar fixing metal fittings in multiple stages at two locations, one above and one below, in the width direction of the temporary reinforcement ring at the intersection of the main reinforcement and the temporary reinforcement ring. Therefore, construction can be carried out more safely even when the weight and diameter of the reinforcing bar cage make the hanging load excessive.

[0019] Furthermore, the method (3) of using a temporary reinforcement ring according to the present invention is characterized in that, in the method (1) or (2) of using a temporary reinforcement ring, the temporary reinforcement ring is configured to include two or more stages of ring portions.

[0020] According to the above-mentioned method (3) of using the temporary reinforcement ring, since the temporary reinforcement ring is configured to include two or more stages of ring portions, the hanging load (total weight of the reinforcing bar cage) when erecting the reinforcing bar cage can be evenly distributed among the two or more stages of ring portions, preventing deflection and deformation of each ring portion and reducing the load borne by the reinforcing bar fixing metal fittings. This makes it possible to increase the safety of the erection work of the reinforcing bar cage even when the reinforcing bar cage becomes heavier, thereby improving construction safety.

[0021] Furthermore, the method (3) of using a temporary reinforcement ring according to the present invention is characterized in that, in the above-mentioned method (1) or (2) of using a temporary reinforcement ring, it includes a step of attaching a suspending device for suspending the reinforcing bar cage to the temporary reinforcement ring and suspending the reinforcing bar cage into the pile hole during the installation work of the reinforcing bar cage.

[0022] According to the above-mentioned method (3) of using the temporary reinforcement ring, even if the size of the reinforcement ring at the hanging position is restricted due to the overcrowding of the hoop reinforcement arrangement, the temporary reinforcement ring is attached to the main reinforcement connection part or the main reinforcement anchor part, i.e., the area where the hoop reinforcement is not arranged, so that the temporary reinforcement ring used as a hanging ring can be made of a material strong enough to safely lift the reinforcing bar cage, and the process of hanging the reinforcing bar cage into the pile hole can be carried out more safely. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a simplified, partially omitted side view showing an example of the configuration of a reinforcing bar cage assembled using a method for using a temporary reinforcing ring according to an embodiment. FIG. [Figure 2] 1A and 1B are diagrams showing a reinforcing bar fastening metal fitting (second metal fitting) used in a method of using a temporary reinforcement ring according to an embodiment, where (a) is a side view and (b) is a bottom view. [Figure 3] 10 is a simplified, partially omitted side view showing another example of the configuration of a reinforcing bar cage assembled using the method for using the temporary reinforcing ring according to the embodiment. FIG. [Figure 4] This is a diagram for explaining an example of the process of erecting a reinforcing bar cage assembled using the method of using the temporary reinforcement ring of the embodiment, and is a diagram schematically showing the erection work of the lower reinforcing bar cage. [Figure 5] This is a diagram for explaining an example of the process of erecting a reinforcing bar cage assembled using the method of using the temporary reinforcement ring of the embodiment, and is a diagram schematically showing the erection work of the middle reinforcing bar cage. [Figure 6] This is a diagram for explaining an example of the process of erecting a reinforcing bar cage assembled using the method of using the temporary reinforcement ring of the embodiment, and is a diagram schematically showing the erection work of the upper reinforcing bar cage. DETAILED DESCRIPTION OF THE INVENTION

[0024] The following describes how to use the temporary reinforcing ring according to the present invention with reference to the drawings. The embodiments described below are preferred examples of the present invention, and therefore various technically preferable limitations are applied. However, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited.

[0025] FIG. 1 is a simplified, partially omitted side view showing an example of the configuration of a reinforcing bar cage assembled using a method for using a temporary reinforcing ring according to an embodiment. The reinforcing bar cage 1 is a reinforcing bar cage for cast-in-place piles constructed using a non-welding method, and is an example of a reinforcing bar cage installed at the top of a pile, i.e., the top of a connected reinforcing bar cage constructed by connecting multiple reinforcing bar cages each having a roughly cylindrical shape. Note that Figure 1 shows the reinforcing bar cage in a horizontal position.

[0026] The reinforcing bar cage 1 is composed of a plurality of main reinforcements 2 arranged around a central axis and approximately parallel to the direction of the central axis, a plurality of hoop reinforcements 3 arranged in a circumferential direction approximately perpendicular to the central axis and having intersections with the plurality of main reinforcements 2, and a plurality of reinforcing rings 4 arranged inside the plurality of main reinforcements 2 and having intersections with these main reinforcements 2. The intersections of the main reinforcements 2 and the reinforcing rings 4 are fixed by first metal fittings 20, which are metal fittings for fastening reinforcing bars. The intersections of the main reinforcements 2 and the hoop reinforcements 3 are fixed by iron wire ties, metal fittings, etc. (not shown). The reinforcing rings 4 are arranged inside the main reinforcements 2, but they can also be arranged outside the main reinforcements 2.

[0027] One end of the reinforcing bar cage 1 is a main reinforcement anchor part 2a that is exposed from the pile head of the cast-in-place pile. The main reinforcement anchor part 2a is the part that will be buried in the foundation footing that will be constructed later. The main reinforcement anchor portion 2a does not have a hoop reinforcement 3 or a reinforcing ring 4, and a temporary reinforcing ring 5A is fixed with a second metal fitting 30, which is a metal fitting for fastening reinforcing bars. In other words, the intersections between each main reinforcement 2 of the main reinforcement anchor portion 2a and the temporary reinforcing ring 5A are fixed with two second metal fittings 30. By fixing the second metal fittings 30 in multiple stages, one above the other, the load on the second metal fittings 30 can be distributed, and the allowable bearing capacity of the second metal fittings 30 can be reinforced.

[0028] The temporary reinforcement ring 5A is also used as a hanging ring to which a lifting device is attached and which hangs the reinforcing bar cage 1 with a crane when erecting the reinforcing bar cage 1 into a pile hole (drilled hole). Therefore, for the temporary reinforcement ring 5A, a ring member is used that is made of a material with sufficient strength, width, and thickness to prevent deformation during hanging, taking into consideration the hanging load (total weight of the reinforcing bar cage) and safety factor. In FIG. 1, the intersections between each main bar 2 of the main reinforcement anchor portion 2a and the temporary reinforcement ring 5A are fixed in multiple stages with two second metal fittings 30, but depending on the specifications of the reinforcing bar cage 1, they may be fixed with a single second metal fitting 30.

[0029] The other end of the reinforcing bar cage 1 forms a main reinforcing bar connection section 2b for connecting the reinforcing bar cages together. As with the main reinforcing bar anchor section 2a, the main reinforcing bar connection section 2b does not have hoops 3 or reinforcing rings 4, and instead has a temporary reinforcing ring 5B fixed with a second metal fitting 30, which is a metal fitting for fastening reinforcing bars. That is, the intersections between each main reinforcing bar 2 of the main reinforcing bar connection section 2b and the temporary reinforcing ring 5B are fixed with the second metal fitting 30. The second metal fitting 30 is composed of a recyclable and reusable fixing metal fitting. Note that in FIG. 1, the intersections between each main reinforcing bar 2 of the main reinforcing bar connection section 2b and the temporary reinforcing ring 5B are fixed with a single second metal fitting 30, but depending on the specifications of the reinforcing bar cage 1, they may be fixed in multiple stages with two second metal fittings 30, as with the main reinforcing bar anchor section 2a.

[0030] The size of the reinforcing bar cage 1 varies depending on the construction site, with diameters ranging from 0.6m to 3m or more, and lengths of up to 12m to 14m per cage. The main reinforcement 2 is made of rod-shaped reinforcing bars such as deformed steel bars with diameters of 19mm to 51mm. The main reinforcement 2 may be placed individually or in groups of two, either horizontally or vertically.

[0031] The size (diameter) and spacing of the main reinforcement bars 2, the size (diameter) and spacing of the hoop reinforcement bars 3, the size (width, thickness) and spacing of the reinforcing rings 4, and the size (width, thickness) of the temporary reinforcing rings 5A and 5B are designed appropriately according to the construction conditions of the cast-in-place pile, such as the size (length, diameter) of the reinforcing bar cage 1 and the length of the connected reinforcing bar cages. The reinforcing ring 4 and temporary reinforcing rings 5A and 5B shown in Figure 1 are made of strip steel plate, but they may also be made of angle steel, H-shaped steel, etc. At the construction site of the cast-in-place pile, these reinforcing bar cages are connected and erected into pile holes that are several tens of meters deep (up to about 70 meters).

[0032] The process of attaching a temporary reinforcement ring 5A to the main reinforcement anchor portion 2a of the reinforcing bar cage 1 and a temporary reinforcement ring 5B to the main reinforcement connection portion 2b with the second metal fittings 30 can be carried out in parallel with the process of attaching the reinforcement ring 4 to each main reinforcement 2 with the first metal fittings 20.

[0033] This attachment step is carried out, for example, in the following manner. First, main reinforcement support stands (not shown) with semicircular concave curved surfaces, which are pre-fabricated according to the size (diameter) of the reinforcing bar cage 1, are arranged in parallel at a predetermined interval. Then, the main reinforcement bars 2 are respectively fastened to the main reinforcement support claws (not shown) provided at regular intervals on the semicircular concave curved surfaces of these main reinforcement support stands, and the main reinforcement bars 2 in the lower half are arranged in parallel to the central axis direction of the reinforcing bar cage.

[0034] Next, reinforcing rings 4 are placed on top of these parallelly arranged main reinforcements 2 at predetermined intervals, parallel to and intersecting with the main reinforcements 2, and the intersections between each main reinforcement 2 and each reinforcing ring 4 are fixed with first metal fittings 20.

[0035] Then, temporary reinforcement rings 5A and 5B are placed at predetermined positions on both ends of the main reinforcements 2 (main reinforcement anchor portions 2a and main reinforcement connection portions 2b) arranged in parallel, parallel to the reinforcement ring 4 and intersecting with the main reinforcements 2, and the intersections between each main reinforcement 2 and each temporary reinforcement ring 5A and 5B are fixed with second metal fittings 30.

[0036] Next, main reinforcement support arch frames (not shown) with semicircular convex curved surfaces, which have been prefabricated according to the size (diameter) of the reinforcing bar cage 1, are assembled and fixed onto each of the main reinforcement support stands. The main reinforcement 2 is then engaged with the main reinforcement support claws (not shown) provided at regular intervals on the semicircular convex curved surfaces of these main reinforcement support arch frames, and the main reinforcement 2 in the upper half is aligned parallel to the central axis of the reinforcing bar cage. In this state, each reinforcing ring 4 and each temporary reinforcing ring 5A, 5B intersects with the main reinforcement 2. The intersections of each main reinforcement 2 and each reinforcing ring 4 are then fixed with first metal fittings 20, and the intersections of each main reinforcement 2 and each temporary reinforcing ring 5A, 5B are fixed with second metal fittings 30.

[0037] Next, multiple hoop reinforcements 3 are wrapped around the cylindrically assembled main reinforcement 2 at predetermined intervals, and then the intersections between the main reinforcement 2 and the hoop reinforcement 3 are fixed using iron wire ties, clip fittings, etc. Thereafter, the main reinforcement support arch frame and the main reinforcement support stand are removed to complete the assembly of the reinforcing bar cage 1. In addition, the reinforcing bar cages connected below the reinforcing bar cage 1 at the top level (pile head) have main reinforcement connection parts 2b at both ends, and the reinforcing bar cage at the bottom level (pile bottom) has one end (upper) of the main reinforcement connection part 2b.

[0038] Figure 2 shows an example of a second metal fitting 30 attached to the intersection between the main reinforcement 2 of the reinforcing bar cage 1 shown in Figure 1 and the temporary reinforcement rings 5A and 5B, where (a) is a front view and (b) is a bottom view. The second fitting 30 comprises a fitting body formed by folding a plate-like body back into a U-shape, with a U-shaped bent portion 31 and left and right side pieces 32. An insertion groove 33 for inserting a temporary reinforcing ring is formed from one side edge of each of the left and right side pieces 32, and an insertion hole 34 for inserting a fixing bolt is formed at the top of the bent portion 31. A nut 35 communicating with the insertion hole 34 is fixed to the bent portion 31, and a fixing bolt 36 is attached to the nut 35.

[0039] The nuts 35 may be fixed to the outside of the bent portion 31 or may be fixed to the inside of the bent portion 31. Alternatively, a screw hole for a fixing bolt may be formed in the bent portion 31 without providing the nuts 35. The plate-like body may be folded back into a roughly U-shape in addition to a U-shape. The second metal fitting 30 may have deep left and right side pieces 32 of the plate-like body so that it can be used for vertical bundling of two main reinforcements 2 vertically. Also, the bent portion 31 of the plate-like body may be wide so that it can be used for horizontal bundling of two main reinforcements 2 horizontally. The second metal fitting 30 can be removed and collected together with the temporary reinforcing rings 5A and 5B from the reinforcing bar cage 1 during or after installation work, and can be reused.

[0040] The first metal fittings 20 that secure the intersections between the main reinforcements 2 and the reinforcing rings 4 can be the same as the second metal fittings 30. A portion of the first metal fitting 20 can be removed from the reinforcing bar cage 1 during erection work, recovered, and reused, without being buried in the pile hole. Also, the left and right side pieces of the metal fitting body of the first metal fitting 20 may be provided with bearings (not shown) through which the shafts of reinforcing bar cage spacers (not shown) can be inserted to ensure a gap between the wall surface of the excavation hole. Also, the type of first metal fitting 20 that is buried during erection and the type that is recovered may be different.

[0041] It is preferable to use rebar fixing fittings of the type shown in Figure 2 for the first fitting 20 and the second fitting 30 in order to improve the ease of attachment and detachment work, but the first fitting 20 and the second fitting 30 are not limited to the type shown in Figure 2, and various types of weldless fittings that can ensure the necessary allowable bearing capacity may be used.

[0042] For example, various types of weldless fittings can be used as the first fitting 20 and the second fitting 30, such as fittings that use U-bolts to secure the intersections between the reinforcing ring 4 or temporary reinforcing rings 5A, 5B and the main reinforcement 2, fittings that hook onto the main reinforcement 2 at the intersections and secure with bolts, or fittings that directly tighten the main reinforcement 2 at the intersections with bolts. These various types of weldless fittings may also be used in combination. When using U-bolts, insertion holes are formed at the positions on the circumference of the reinforcing ring 4 or temporary reinforcing rings 5A, 5B where the main reinforcement 2 is to be placed, through which both ends of the U-bolts can be passed and secured with nuts. In the example of Figure 1, the intersection between each main reinforcement 2 of the main reinforcement anchor portion 2a and the temporary reinforcement ring 5A is fixed with two second fittings 30, but in another variant, it is also possible to fix in multiple stages with two or more reinforcing bar fixing fittings by changing the type of second fitting 30 or combining the different types of fittings described above.

[0043] Fig. 3 is a simplified, partially omitted side view showing another example of the configuration of a reinforcing bar cage assembled using the method for using the temporary reinforcing ring according to the embodiment. Fig. 3 shows the cage in a horizontal position. Components having the same mechanisms as those in Fig. 1 are given the same reference numerals, and their explanations will be omitted.

[0044] The reinforcing bar cage 1A shown in FIG. 3 is an example of a reinforcing bar cage that is placed in the middle of the connected reinforcing bar cages. The reinforcing bar cage 1A is composed of a plurality of main reinforcements 2, a plurality of hoop reinforcements 3, and a plurality of reinforcing rings 4. The intersections of these main reinforcements 2 and reinforcing rings 4 are fixed by first metal fittings 20, and the intersections of the main reinforcements 2 and hoop reinforcements 3 are fixed by iron wire ties, clip fittings, etc. (not shown).

[0045] Both ends of the reinforcing bar cage 1A are main reinforcement connecting portions 2b for connecting the reinforcing bar cages together. The main reinforcement connecting portions 2b are configured so that adjacent main reinforcements 2 are alternately (staggered) by a predetermined length in the axial direction (staggered configuration). No hoops 3 or reinforcing rings 4 are provided in the main reinforcement connecting portions 2b, and temporary reinforcing rings 5B are placed on the main reinforcements 2 of the main reinforcement connecting portions 2b, and the intersections between the main reinforcement 2 and the temporary reinforcing rings 5B are fixed with second metal fittings 30. The position and number of temporary reinforcing rings 5B can be designed appropriately depending on the length of the main reinforcement connecting portions 2b, etc. Alternatively, a temporary reinforcing ring 5B may be placed on the main reinforcement 2 on the protruding side of the main reinforcement connection portion 2b, and the intersections between the protruding main reinforcement 2 and the temporary reinforcing ring 5B may be fixed with second metal fittings 30. In this case, the intersections are reduced to half or less, and the distance between the main reinforcement bars at the intersections is more than doubled. Therefore, as a measure against the hanging load, it is preferable to increase the width (height) of the temporary reinforcing ring 5B and fix it in multiple stages at each intersection with two or more second metal fittings 30. Of course, even in the configuration shown in FIG. 3, it is also possible to fix it in multiple stages at each intersection with two or more second metal fittings 30.

[0046] The process of attaching temporary reinforcement rings 5B to the main reinforcement connection parts 2b at both ends of the reinforcing bar cage 1A using second metal fittings 30 can be carried out in the same manner as the process of attaching temporary reinforcement rings 5A, 5B to the main reinforcement anchor parts 2a and main reinforcement connection parts 2b of the reinforcing bar cage 1 described above using second metal fittings 30, except that adjacent main reinforcements 2 are arranged alternately and offset by a predetermined length in the axial direction. When the reinforcing bar cages 1A are connected together during erection, the connection points between the main reinforcements 2 are connected in a manner that is offset in the axial direction (up and down), which makes it possible to increase strength and durability against horizontal forces during earthquakes.

[0047] Next, an example of the process for erecting a reinforcing bar cage assembled using the method for using the temporary reinforcing ring according to the embodiment will be described with reference to Figures 4 to 6. For ease of explanation, the case where a lower reinforcing bar cage (pile bottom), a middle reinforcing bar cage (intermediate), and an upper reinforcing bar cage (pile top) are erected while being sequentially connected will be described.

[0048] Figure 4 shows the process of erecting the lower reinforcing bar cage into the pile hole, Figure 5 shows the process of erecting the middle reinforcing bar cage into the pile hole, and Figure 6 shows the process of erecting the upper reinforcing bar cage into the pile hole. This erection process is one of the steps included in the all-casing construction method. Note that components with the same mechanisms as the reinforcing bar cages 1 and 1A shown in Figures 1 and 3 are given the same reference numerals and their explanations are omitted.

[0049] The lower reinforcing bar cage 10C has a temporary reinforcing ring 5B attached to the main reinforcing bar connecting portion 2b on one end (upper side). The middle reinforcing bar cage 10B has a temporary reinforcing ring 5B attached to the main reinforcing bar connecting portion 2b on both ends. The upper reinforcing bar cage 10A has a temporary reinforcing ring 5A attached to the main reinforcing bar anchor portion 2a on one end (upper side), and a temporary reinforcing ring 5B attached to the main reinforcing bar connecting portion 2b on the other end (lower side).

[0050] These reinforcing bar cages 10A, 10B, and 10C, assembled using the method of using temporary reinforcing rings, are transported (moved) sideways to the vicinity of the pile holes. These reinforcing bar cages 10A, 10B, and 10C have temporary reinforcing rings 5A attached to the main reinforcing bar anchor portions 2a and temporary reinforcing rings 5B attached to the main reinforcing bar connecting portions 2b, preventing deformation of the cage shape during transportation (movement). The erection of these reinforcing bar cages is carried out using, for example, a mobile crane such as a crawler crane.

[0051] [Installation of lower rebar cage 10C] First, the lower reinforcing bar cage 10C is sling-hooked onto a traverser 41 for hoisting loads attached to a wire rope 40 suspended from the boom of a mobile crane (not shown). That is, a sling (such as a sling hook) 42 suspended from the traverser 41 is hooked onto a temporary reinforcement ring 5B on one end (upper side) of the lower reinforcing bar cage 10C, and the lower reinforcing bar cage 10C, which has been lying on its side, is raised upright (Fig. 4(a)). The number of slings 42 attached can be determined taking into consideration the size and weight of the reinforcing bar cage 10C, but is generally 2 to 6.

[0052] Thereafter, the lower reinforcing bar cage 10C is lowered into the pile hole (excavation hole) 50 while being suspended, and the lower reinforcing bar cage 10C is lowered until the reinforcing ring 4 located at the top of the lower reinforcing bar cage 10C is positioned slightly above the upper end opening of the casing 51 pressed into the pile hole 50. Then, after attaching a plurality of receiving jigs 52 for supporting the reinforcing bar cages to the upper opening of the casing 51, the lower reinforcing bar cage 10C is further lowered and the reinforcing rings 4 are engaged on the receiving jigs 52, so that the lower reinforcing bar cage 10C is suspended from the casing 51 (Fig. 4(b)). The number of receiving jigs 52 attached to the upper opening of the casing 51 is determined taking into consideration the weight of the reinforcing bar cage 10C, the strength of the reinforcing rings 4, etc., so that the reinforcing rings 4 will not break or deform when engaged with the receiving jigs 52.

[0053] Then, all of the second metal fittings 30 that secure the temporary reinforcement ring 5B are removed from the temporary reinforcement ring 5B and recovered, and the temporary reinforcement ring 5B that has been removed from the main reinforcement 2 is lifted up with a traverser 41 and the temporary reinforcement ring 5B is removed from the lower reinforcing bar cage 10C (Figure 4(c)).

[0054] [Installation of middle rebar cage 10B] Next, we move on to erecting the middle steel cage. First, the middle reinforcing bar cage 10B, which is lying on its side, is raised up in the same manner as the lower reinforcing bar cage 10C. After the middle-stage reinforcing bar cage 10B is erected, the temporary reinforcing ring 5B attached to the main reinforcing bar connection part 2b on the other end (lower side) of the middle-stage reinforcing bar cage 10B is removed. That is, all of the second metal fittings 30 that secure the temporary reinforcing ring 5B attached to the main reinforcing bar connection part 2b on the other end (lower side) are removed and collected, and the temporary reinforcing ring 5B is removed from the middle-stage reinforcing bar cage 10B (Fig. 5(a)).

[0055] Then, while the middle reinforcing bar cage 10B is suspended, it is carried above the lower reinforcing bar cage 10C suspended from the upper opening of the casing 51, and then the middle reinforcing bar cage 10B is lowered to a position where the main reinforcement 2 of the lower main reinforcement connection part 2b of the middle reinforcing bar cage 10B overlaps with the main reinforcement 2 of the upper main reinforcement connection part 2b of the lower reinforcing bar cage 10C, and then the lower reinforcing bar cage 10C and the middle reinforcing bar cage 10B are connected.

[0056] For example, using a connecting method such as connecting fittings (not shown), fixing the main reinforcements 2 together using mechanical joints, or bundling the main reinforcements 2 together using wire, the lower main reinforcement 2 of the middle reinforcing bar cage 10B is connected to the upper main reinforcement 2 of the lower reinforcing bar cage 10C, thereby connecting the lower reinforcing bar cage 10C and the middle reinforcing bar cage 10B (Figure 5(b)).

[0057] Thereafter, the middle reinforcing bar cage 10B connected to the lower reinforcing bar cage 10C is lifted up, and after the receiving jig 52 attached to the upper end opening of the casing 51 is temporarily removed, it is lifted into the pile hole 50 and the middle reinforcing bar cage 10B is lowered until the reinforcing ring 4 located at the top of the middle reinforcing bar cage 10B is positioned slightly above the upper end opening of the casing 51.

[0058] After attaching multiple receiving jigs 52 to the upper opening of the casing 51 again, the middle reinforcing bar cage 10B is further lowered and the reinforcing ring 4 is engaged on top of the receiving jigs 52, so that the middle reinforcing bar cage 10B is suspended from the casing 51 (Figure 5(c)).

[0059] Then, all of the second metal fittings 30 that secure the temporary reinforcement ring 5B are removed from the temporary reinforcement ring 5B and recovered, and the temporary reinforcement ring 5B removed from the main reinforcement 2 is lifted up with a traverser 41 and removed from the middle reinforcing bar cage 10B (Figure 5(d)).

[0060] [Installation of upper rebar cage 10A] Next, we move on to erecting the upper reinforcing bar cage 10A. First, the upper reinforcing bar cage 10A, which has been laid on its side, is raised upright in the same manner as the lower reinforcing bar cage 10C. The hoisting device 42 suspended from the traverser 41 is attached to a temporary reinforcing ring 5A fixed to the main reinforcing bar anchor part 2a at one end (upper side) of the upper reinforcing bar cage 10A. After the upper reinforcing bar cage 10A is erected, the temporary reinforcing ring 5B attached to the main reinforcing bar connection part 2b on the other end (lower side) of the upper reinforcing bar cage 10A is removed. That is, all second metal fittings 30 that secure the temporary reinforcing ring 5B are removed and collected, and the temporary reinforcing ring 5B is removed from the upper reinforcing bar cage 10A (Fig. 6(a)).

[0061] Then, while the upper reinforcing bar cage 10A is suspended, it is carried above the middle reinforcing bar cage 10B suspended from the upper end opening of the casing 51, and then the upper reinforcing bar cage 10A is lowered to a position where the main reinforcement 2 of the lower main reinforcement connection part 2b of the upper reinforcing bar cage 10A overlaps with the main reinforcement 2 of the upper main reinforcement connection part 2b of the middle reinforcing bar cage 10B, and then the middle reinforcing bar cage 10B and the upper reinforcing bar cage 10A are connected.

[0062] For example, using a connecting method such as fixing the main bars together using connecting fittings or mechanical joints, or bundling the main bars together using wire, the lower main bars 2 of the upper reinforcing bar cage 10A are connected to the upper main bars 2 of the middle reinforcing bar cage 10B, thereby connecting the middle reinforcing bar cage 10B and the upper reinforcing bar cage 10A (Figure 6(b)).

[0063] Then, the upper reinforcing bar cage 10A connected to the middle reinforcing bar cage 10B is lifted up, and the support jig 52 attached to the upper end opening of the casing 51 is removed, and then the cage is lifted into the pile hole 50. The connected reinforcing bar cages are lowered to the bottom of the pile hole 50, and the lifting device 42 is removed from the temporary reinforcement ring 5A above the upper reinforcing bar cage 10A (Figure 6(c)).

[0064] After the rebar cage is installed, the tremie pipe is installed in the pile hole, concrete is poured, and the casing is removed. The temporary reinforcing ring 5A attached to the main reinforcing bar anchor part 2a of the upper reinforcing bar cage 10A is also used as a hanging ring, so it may be difficult to remove it during the reinforcing bar cage erection process. Therefore, it is best to remove it at an appropriate time after the erection work. For example, if the pile head is shallow, the temporary reinforcing ring 5A may be removed after the concrete has been poured and the casing has been pulled out (FIG. 6(d)). Also, if the pile head is deep, it may be left as it is and the temporary reinforcing ring 5A may be removed when the foundation footing is constructed in the subsequent process.

[0065] Furthermore, if concrete is poured up to a position that covers the main reinforcing anchor part 2a in order to protect it during concrete pouring, i.e., if the temporary reinforcing ring 5A is buried in the pile head excess concrete, the temporary reinforcing ring 5A may be removed after the excess concrete is removed during subsequent pile head processing. Note that when the temporary reinforcing ring 5A is buried in the pile head excess concrete, it is preferable to cure the main reinforcing bars 2 of the main reinforcing anchor part 2a, the temporary reinforcing ring 5A, and the second metal fitting 30 in advance to make it easier to remove the excess concrete later.

[0066] The reinforcing bar cages 10A, 10B, and 10C shown in Figures 4 to 6 have a configuration in which adjacent main reinforcements 2 arranged at the main reinforcement connection parts 2b are shifted alternately in the axial direction, but they may also have a configuration in which adjacent main reinforcements 2 are not shifted in the axial direction.

[0067] Furthermore, while the reinforcing bar cages 10A, 10B, and 10C shown in Figures 4 to 6 are constructed with single-reinforced bars, in another configuration example, the reinforcing bar cages 10A, 10B, and 10C can also be constructed with double-reinforced bars, in which the inner and outer cages are assembled together. Such double-reinforced cages are used at construction sites that require extremely high earthquake resistance, where single-reinforced cages cannot withstand horizontal forces during earthquakes. Therefore, double-reinforced cages have a large cage diameter, and their main bars are thick and numerous, and the cages are connected using mechanical joints such as couplers. For example, the main bar connection part 2b of a double-reinforced cage is arranged so that the main bars 2 of the outer cage and the main bars 2 of the inner cage are offset in the axial direction by a predetermined length (approximately 500 mm). When connecting cages as shown in Figures 5(b) and 6(b), the main reinforcement bars of the outer cages of the upper and lower double reinforced cages are connected to each other with mechanical joints (rubber joints), and the main reinforcement bars of the inner cages are connected to each other with mechanical joints (rubber joints).

[0068] Furthermore, since the double-reinforced cage described above has a heavier cage weight than a normal single-reinforced cage, it is necessary to improve the safety of the lifting work when erecting it. Temporary reinforcement rings 5A of sufficient strength and size to prevent deformation during lifting work can be attached to the main reinforcement anchor parts 2a of the outer cage and / or inner cage of the topmost double-reinforced cage using second metal fittings 30, and the temporary reinforcement rings 5A can be used as lifting rings when erecting it, thereby improving the safety of the lifting work when erecting it. Furthermore, it is preferable to fix the intersections between the main reinforcement 2 and the temporary reinforcement rings 5A in multiple stages using two or more second metal fittings 30. In addition, the temporary reinforcement ring 5B attached to the main reinforcement connection part 2b on one end (upper side) of the double reinforcing bar cages in the middle and lower tiers may be used as a hanging ring when erecting the cage.In this case, the temporary reinforcement ring 5B should be strong and large enough to not deform during the hanging work.

[0069] When the temporary reinforcement rings 5A and 5B are used as suspension rings during erection, the spacing L (mm) of the main reinforcement 2 on the temporary reinforcement rings 5A and 5B, the number n, the installation location m of the suspension device 42, the suspension load (total weight of the reinforcing bar cage) W (kN), the bending moment M (= (W / m) × L / 4) (N·mm) of the temporary reinforcement rings 5A and 5B, and the cross-sectional area A (mm 2 ), section modulus Z (mm 2 ), shear stress τ = (W / m) / A (N / mm 2 ), bending stress σ=M / Z(N / mm 2 It is preferable to determine the specifications of the temporary reinforcing rings 5A and 5B so that the shear stress τ and the bending stress σ satisfy the conditions taking into account a predetermined safety factor, i.e., shear stress τ = (W / m) / A × safety factor, bending stress σ = M / Z × safety factor. The safety factor is preferably at least 2 or more, more preferably 3 or more.

[0070] According to the method of using the temporary reinforcement ring in the above embodiment, when assembling the reinforcing bar cage, the temporary reinforcement ring 5A is attached to the main reinforcement anchor portion 2a and the temporary reinforcement ring 5B is attached to the main reinforcement connection portion 2b with the second metal fittings 30 (metal fittings for fixing reinforcing bars). Therefore, even if the areas that become the main reinforcement anchor portion 2a and the main reinforcement connection portion 2b become longer due to the weight and diameter of the reinforcing bar cage, deformation of the reinforcing bar cage can be prevented when assembling, storing, or moving the reinforcing bar cage in a sideways position, thereby increasing safety during construction. Furthermore, even if the lifting load during the installation work of the reinforcing bar cages becomes excessive due to the increased weight and diameter of the connected reinforcing bar cages, the temporary reinforcement rings 5A, 5B are attached to the main reinforcement connection parts 2b and the main reinforcement anchor parts 2a, so the load burden on the first metal fittings 20 at the intersections of the reinforcing rings 4 and the main reinforcement 2 can be reduced, thereby increasing safety during installation. Furthermore, the temporary reinforcement rings 5A, 5B are removed together with the second metal fittings 30 during or after the installation of the reinforcing bar cage, so that the construction of the cast-in-place piles can be carried out safely without these temporary reinforcement rings 5A, 5B or the second metal fittings 30 interfering with subsequent concrete pouring work, etc.

[0071] Furthermore, according to the method of using the temporary reinforcement rings in the embodiment, even if the size of the reinforcement ring 4 at the hanging position is restricted due to the overcrowding of the arrangement of the hoop reinforcement 3, the temporary reinforcement ring 5A is attached to the main reinforcement anchor portion 2a, and the temporary reinforcement ring 5B is attached to the main reinforcement connection portion 2b, i.e., in an area where the hoop reinforcement 3 is not arranged, so the temporary reinforcement rings 5A and 5B used as hanging rings can be made of materials strong enough to safely lift the connected reinforcing bar cage, making the process of hanging the reinforcing bar cage into the pile hole 50 safer.

[0072] Additionally, in response to the increasing weight and diameter of the reinforcing bar cage, the size of the temporary reinforcing rings 5A and 5B can be increased, and the second metal fittings 30 can be used to secure the main reinforcement bars 2 at their intersections in two or more stages, one above the other, thereby reinforcing the allowable bearing capacity of the second metal fittings 30. Therefore, construction can be carried out safely even in cases where an excessive hanging load occurs. Furthermore, by using the temporary reinforcing rings 5A and 5B, the erection work of the reinforcing bar cage in which the main reinforcements 2 are arranged in a staggered pattern can be carried out more safely.

[0073] In the above embodiment, the temporary reinforcement rings 5A and 5B are described as being composed of a single-stage wide ring, but the temporary reinforcement rings 5A and 5B are not limited to this form and may be composed of a ring portion having two or more stages (multi-stage ring portion). For example, as a modified example, the temporary reinforcement rings 5A, 5B may be configured to include two or more ring portions arranged at a predetermined interval in the central axial direction of the reinforcing cage, and two or more connecting portions connecting the inner surfaces of the adjacent ring portions. In this case, the connecting portions may be configured to include connecting rods or wire ropes. Furthermore, when the temporary reinforcement ring of the modified example is attached to a reinforcing bar cage, it is preferable that the connecting portion is fixed to the inner surface of the adjacent ring portion and has a shape that protrudes inward from the inner surface (for example, a U-shape when viewed from the side) so that a predetermined space is secured between the main reinforcement of the reinforcing bar cage and the connecting portion.

[0074] According to the above modification, the temporary reinforcement rings 5A, 5B are configured to include two or more stages of ring portions, so that the hanging load (total weight of the reinforcing bar cage) when erecting the reinforcing bar cage can be evenly distributed among the two or more stages of ring portions, preventing deflection and deformation of each ring portion and reducing the load borne by the second metal fittings 30 (metal fittings for fastening reinforcing bars). This makes it possible to increase the safety of the erection work of the reinforcing bar cage even when the reinforcing bar cage becomes heavier, thereby improving construction safety. [Explanation of symbols]

[0075] 1, 1A, 10A, 10B, 10C Reinforced concrete cage 2 Main reinforcement 2a Main reinforcement anchor 2b Main bar connection 3 Hoop muscles 4 Reinforcement ring 5A, 5B Temporary reinforcement ring 20 First metal fitting (metal fitting for fixing rebar) 30 Second metal fitting (metal fitting for fixing rebar) 31 Bend section 32 Left and right side piece 33 Insertion groove 34 Insertion hole 35 Nut 36 Fixing bolt 40 Wire Rope 41 Traverser 42 Lifting equipment 50 Pile hole 51 Casing 52 Receiving jig

Claims

1. During assembly of a reinforcing bar cage for a cast-in-place pile, the reinforcing bar cage includes a plurality of main reinforcements arranged around a central axis substantially parallel to the direction of the central axis, a plurality of hoop reinforcements arranged in a circumferential direction substantially perpendicular to the central axis and having intersections with the plurality of main reinforcements, and a plurality of reinforcing rings arranged inside or outside the plurality of main reinforcements and having intersections with the plurality of main reinforcements, the process of attaching temporary reinforcing rings with reinforcing bar fixing metal fittings to main reinforcement connection parts for connecting the reinforcing bar cages together or to main reinforcement anchor parts exposed from the pile head of the cast-in-place pile; A method of using a temporary reinforcement ring, characterized by including a step of removing the temporary reinforcement ring together with the reinforcing bar fixing fittings during or after the installation work of the reinforcing bar cage.

2. 2. A method for using a temporary reinforcement ring according to claim 1, wherein the reinforcing bar fixing metal fittings are fixed in multiple stages at the intersections of the main reinforcement bars and the temporary reinforcement ring.

3. 2. A method for using a temporary reinforcing ring according to claim 1, wherein the temporary reinforcing ring is configured to include two or more stages of ring portions.

4. A method of using a temporary reinforcement ring as described in any one of claims 1 to 3, characterized in that it includes a step of attaching a hanging device for suspending the reinforcing bar cage to the temporary reinforcement ring and suspending the reinforcing bar cage into a pile hole during the installation work of the reinforcing bar cage.

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