JP5633525B2 - Pile head joint structure - Google Patents

Description

  The present invention relates to a pile head joint structure between a pile head in a foundation pile and a foundation footing or a portion on the upper structure side.

  In soft ground, foundation piles are often used to support the load of superstructures such as buildings. When using foundation piles, the foundation pile head is firmly connected to the foundation footing or a part of the corresponding upper structure (hereinafter referred to as the upper structure) for the purpose of load transmission and ensuring stability. In general, the structure is fixed.

  Various types of joint structures have been proposed as the fixing structure of the foundation pile head, but one end of the reinforcing bar is mainly fixed to the pile head and the other end is fixed to the upper structure. A method of making the joint between the upper structure and the upper structure a rigid bond having a high initial rigidity is frequently used from the viewpoint of construction cost and easy workability. The structure in which the foundation pile head is joined to the superstructure using reinforcing bars is designed in accordance with the required performance based on the arrangement of reinforcing bars and the amount of reinforcing bars for seismic resistance. It is possible to exert power. However, the structure in which the foundation pile head is joined rigidly to the upper structure using reinforcing bars as described above generates a large moment at the pile head portion. However, the foundation pile head may lead to brittle fracture.

  As described above, as a pile head joint structure that replaces the foundation pile head joint structure using the reinforcing bar as described above, recently, the pile head joint is changed from a rigid connection to a semi-rigid connection (that is, the initial rigidity is lowered). There is a design philosophy that reduces the bending moment acting on the pile head by imparting rotational performance to the pile head. One method for embodying the semi-rigid condition with reduced pile head fixation is to reduce the reinforcing bar arrangement diameter by placing the reinforcing bar arrangement diameter closer to the center of the pile. For example, as shown in FIG. 7, the reinforcing bar 20 arranged at the head of the foundation pile made of the steel pipe pile 2 is arranged near the center of the foundation pile, and the bar arrangement diameter of the pile head reinforcement is set to This is a technique for reducing the virtual RC (reinforced concrete) pile diameter in terms of design, as compared to the conventional case where the reinforcing bars 20 are arranged outside or near the inner side of the steel pipe wall material of the steel pipe pile 2. By doing so, the initial rigidity is lowered by joining the pile head as a semi-rigid joint, and as shown in FIG. 8, when a bending moment M acts on the pile head during an earthquake, This is a design philosophy of a pile head joint structure that allows minute rotation (that is, improved rotation performance).

JP 2001-295220 A JP 2002-349011 A

  As mentioned above, reducing the reinforcing bar diameter in order to give rotation performance of the pile head is that when the bendingless moment acts when the unreinforced part becomes large at the joint part of the pile end part As shown in FIG. 8, there is a possibility that a crack 9 is generated near the joint. For example, in the case of the above-mentioned pile head joint structure that allows the micro-rotation of the pile head, as shown in FIG. 8, the bending moment M indicated by the solid line arrow is applied to the pile head when an earthquake load acts upon a large earthquake. In the meantime, it works repeatedly many times while reversing. At this time, as shown in FIG. 8, a crack 9 (crack) is generated in the reinforcing bar joint (pile head reinforcing bar joint) between the pile head and the foundation footing 1 or the upper structure 1a. When such a bending moment M acts and crack 9 occurs, the reinforcing bar 20 near the boundary between the steel pipe pile 2 (foundation pile) side and the foundation footing 1 or the reinforced concrete bottom of the upper structure 1a extends. It comes out and is not restrained by the concrete 8.

  As described above, when the reinforcing bar 20 near the boundary between the steel pipe pile 2 (foundation pile) side and the foundation footing 1 or the bottom part of the reinforced concrete of the upper structure 1a extends and comes out and is not restrained by the concrete 8, FIG. In this way, the reinforcing bar 20 is locally exposed, a tensile load is applied to the exposed reinforcing bar portion 21, and strain is concentrated on the exposed reinforcing bar 20 portion (the generated strain is localized). At this time, since the exposed reinforcing bar portion 21 comes to bear a large amount of tensile force and the like, the strain is concentrated so that the strain concentrates on the exposed reinforcing bar portion 21, and as shown in FIG. The generated stress is maximized compared to the portion, and the reinforcing bar 20 yields early. Thereafter, when the bending moment M is reversed, as shown in FIG. 10, the compressive load P acts on the exposed reinforcing bar portion 21, and the exposed reinforcing bar portion 21 is deformed and buckled as shown in FIG. . Originally, since the reinforcing bar 20 is disposed inside the concrete, the concrete bears a compressive load, and the compressive force does not act on the reinforcing bar 20. However, at the location where the crack 9 occurs, the compressive load acts on the reinforcing bar 20 until the crack 9 is closed and the upper and lower concrete portions come into contact with each other and the concrete is in a state where the compressive load can be transmitted.

  After the buckled and exposed rebar portion 21 as described above is buckled as shown in FIG. 10, it is further subjected to repeated loads of a tensile load and a compressive load. The breakage of the reinforcing bar 20 occurs easily. In general, a plurality of reinforcing bars 20 are arranged on the pile head portion. However, the structural strength is remarkably reduced by breaking one of the reinforcing bars. It leads to brittle fracture of pile head reinforcement joints. Therefore, a technique capable of improving pile head rebar joints that may lead to brittle fracture under a large earthquake is desired.

  It is also known that the rotational rigidity of the pile head rebar joint when the pile head is a semi-rigid joint is defined by the amount of rebar extension at the pile head joint. When buckling or the like is generated as well as breaking, the rotational rigidity of the pile head reinforcing bar joint portion is greatly changed. If the rotational rigidity of the pile head rebar joint changes and the rigidity decreases, the load sharing of the pile head generally changes, and the load more than expected in the design is partially applied. There is a risk of leading to complete destruction.

  For this reason, pile head semi-rigid joints that expect the rotational performance of pile head rebar joints are stable without changing the rotational performance of pile head rebar joints under repeated loads during earthquakes. It is important to maintain a general load displacement relationship. In particular, when cracks 9 occur on the joint surface at the pile head portion, it is also expected that the reinforcing bars have already yielded, so as to suppress a decrease in rotational rigidity while having a certain rotational performance. For this, the behavior of the reinforcing bar after yielding is very important.

  As mentioned above, when the pile head joint is semi-rigidly joined, the amount of rebar expansion is ensured to have sufficient rotational performance, so that the rebar does not break during rotation. It is especially sought to do. Therefore, the reinforcing bar 20 in the vicinity of the boundary between the steel pipe pile 2 (foundation pile) side and the bottom part of the reinforced concrete of the foundation footing 1 or the upper structure 1a is extended and pulled out, the reinforcing bar 20 is locally exposed, and the exposed reinforcing bar 20 It is particularly required to avoid the concentration of strain in the portion (when the generated strain is localized, there is an increased risk of local breakage before the expansion amount of the reinforcing bar 20 corresponding to the rotational performance cannot be secured). For this reason, the reinforcing bars should be laid so that the strain of the reinforcing bars across the boundary between the steel pipe pile 2 (foundation pile) side and the foundation footing 1 or the bottom part of the reinforced concrete of the upper structure 1a becomes uniform and a sufficient amount of expansion is secured. It is considered effective to use a buckling prevention type unbonding. Here, the buckling prevention type unbonding means that the unbonded reinforcing bar can further prevent the occurrence of buckling as shown in FIG. 10 with a reinforcing steel pipe or the like. However, conventionally, as shown in Patent Documents 1 and 2, only a technique for unbonding reinforcing bars has been proposed for a structure in which a pile head joint is rigidly coupled. Actually, in the joint structure shown in Patent Documents 1 and 2, for the reinforcing bars arranged at the edge that is supposed to dominate the rotational performance of the pile head joint, the pile head joint is made to be a rigid joint. It is used as a constrained reinforcing bar and is not unbonded, and is not in a form that can solve the problems that occur when the pile head rotates. That is, no attempt has been made to unbond the reinforcing bars in a buckling-preventing manner in order to solve the above-mentioned problems peculiar to the case of semi-rigid joining.

  Further, when a bending moment acts on the pile head in the semi-rigid connection of the steel pipe pile 2, the crack 9 described above is generated on one side as shown in FIG. At this time, on the opposite side of the crack 9, a mode in which the steel pipe pile 2 is recessed into the reinforced concrete bottom portion of the foundation footing 1 or the upper structure 1a occurs. When both the pile head and the foundation footing 1 or the member of the upper structure 1a are concrete, the strength of the members is almost the same, so there is no big problem. However, when the steel pipe pile 2 is used, as shown in FIG. 8, the steel pile head having a high member strength and hardness is shown in FIG. 8 with respect to the concrete foundation footing 1 or the upper structure 1 a having a low member strength and hardness. In addition, there is a problem in that a mode of indenting on the opposite side of the crack 9 tends to occur.

  Then, this invention suppresses the fall of the rotational performance of a pile head joint part in the pile head joint structure which accepts the micro rotation of a pile head joint part as a semi-rigid joint as mentioned above. The purpose is to provide a pile head joint structure that can be used.

  In the pile head joint structure according to the first aspect of the invention, in the pile head joint structure in which the foundation footing or the upper structure and the pile head are semi-rigidly joined by a reinforcing bar to allow micro rotation of the pile head, A reinforcing steel pipe having an inner diameter larger than the reinforcing bar diameter and shorter than a reinforcing bar length of the reinforcing bar is disposed so as to surround the reinforcing bar arranged on the reinforcing bar, and the reinforcing steel pipe is connected to the steel pipe pile and the foundation footing or It arrange | positions so that the boundary surface in the junction part of superstructure may be straddled, Furthermore, the said reinforcing bar is arrange | positioned so that the inner side of the said reinforcing steel pipe may be penetrated, and it is a filling material between the said reinforcing bar and the internal peripheral surface of the said reinforcing steel pipe Is filled and hardened, a filling mortar is provided between the steel pipe inner side and the reinforcing steel pipe in the steel pipe pile, and no reinforcing bar is provided in the reinforcing bar in the reinforcing steel pipe.

  In the pile head joint structure of the second invention, in the pile head joint structure in which the foundation footing or the upper structure and the pile head are joined semi-rigidly by a reinforcing bar to allow micro rotation of the pile head, A reinforcing steel pipe having an inner diameter larger than the reinforcing bar diameter and shorter than a reinforcing bar length of the reinforcing bar is disposed so as to surround the reinforcing bar arranged on the reinforcing bar, and the reinforcing steel pipe is connected to the steel pipe pile and the foundation footing or It arrange | positions so that the boundary surface in the junction part of superstructure may be straddled, Furthermore, the said reinforcing bar is arrange | positioned so that the inner side of the said reinforcing steel pipe may be penetrated, and it is a filling material between the said reinforcing bar and the internal peripheral surface of the said reinforcing steel pipe Is filled and hardened, a filling mortar is provided between the steel pipe inner side and the reinforcing steel pipe in the steel pipe pile, and an adhesion preventing coating is provided on the reinforcing bar in the reinforcing steel pipe.

  In the third invention, in the pile head joint structure of the first invention or the second invention, the cross-sectional area of the rebar is smaller than the cross-sectional area of the rebar in the outer part of the reinforcing steel pipe only in the inner part of the reinforcing steel pipe. It is characterized by being set.

  According to a fourth invention, in the pile head joint structure according to any one of the first invention to the third invention, a portion on the foundation footing or upper structure side, which is in contact with the steel pipe in the steel pipe pile head, is equivalent to the steel pipe. A bearing ring having the above rigidity or hardness is provided.

  According to a fifth invention, in the pile head joint structure according to any one of the first invention to the fourth invention, the outer peripheral surface of the reinforcing steel pipe has a slip stopper.

  According to the first aspect of the present invention, in the pile head joint structure that allows the micro-rotation of the pile head by joining the foundation footing or the upper structure and the pile head in a semi-rigid connection with a reinforcing bar, the pile head is disposed in the steel pipe pile head. A reinforcing steel pipe having an inner diameter larger than that of the reinforcing bar and shorter than the reinforcing bar length is disposed so as to surround the reinforcing bar, and the reinforcing steel pipe is connected to the steel pipe pile and the foundation footing or the superstructure. It is arranged so as to straddle the boundary surface, and further, the reinforcing bar is arranged so as to penetrate the inside of the reinforcing steel pipe, and the filling material is filled and cured between the reinforcing bar and the inner peripheral surface of the reinforcing steel pipe, Since the filling mortar is provided between the steel pipe inner side and the reinforcing steel pipe in the steel pipe pile, and no reinforcing bar is provided in the reinforcing steel pipe, the following effects can be obtained. Even if a horizontal force acts on the foundation footing or the upper structure side during an earthquake and a crack occurs at the boundary between the steel pipe pile head and the foundation footing or the upper structure side, the intermediate part of the reinforcing bar is still inside the reinforcing steel pipe. Since the deformation in the direction perpendicular to the axis is constrained, it is possible to prevent the buckling of the reinforcing bar or breakage due to it, and the brittle fracture of the pile head joint. As a result, semi-rigid pile head joints that allow fine rotation of the pile head when the horizontal footing acts on the foundation footing or the equivalent superstructure side during a major earthquake (enhanced rotation performance) The effect that the change of the rotational rigidity of a pile head can be suppressed in a part is acquired. In addition, since no reinforcing bar is provided in the reinforcing steel pipe, the same function as that in the case where an anti-adhesion film is provided on the reinforcing bar can be easily exhibited, and the structure can be simplified. Therefore, when the earthquake occurs, the steel pipe pile head rotates slightly due to the bending moment acting on the pile head, which easily eliminates the adhesion between the reinforcing bar and the filler material in the reinforcing steel pipe, And the like. By setting this unbonded state, the seismic force in the compression or tension direction acting on the reinforcing bar can be borne by the entire rebar part in the unbonded state, and localization of the strain of the reinforcing bar due to the seismic force is avoided. Thus, the strain of the reinforcing bar can be made uniform. Furthermore, by preventing the buckling of the reinforcing bars with the reinforcing steel pipe, it is possible to suppress the occurrence of buckling under repeated loads and to prevent the yield strength from abruptly decreasing, maintaining the rotation performance of the pile head It becomes possible.

  According to the second invention, in the pile head joint structure which allows the micro-rotation of the pile head by joining the foundation footing or the upper structure and the pile head to a semi-rigid joint by a reinforcing bar, the above-mentioned disposed in the steel pipe pile head A reinforcing steel pipe having an inner diameter larger than that of the reinforcing bar and shorter than the reinforcing bar length is disposed so as to surround the reinforcing bar, and the reinforcing steel pipe is connected to the steel pipe pile and the foundation footing or the superstructure. It is arranged so as to straddle the boundary surface, and further, the reinforcing bar is arranged so as to penetrate the inside of the reinforcing steel pipe, and the filling material is filled and cured between the reinforcing bar and the inner peripheral surface of the reinforcing steel pipe, In order to reduce adhesion between reinforcing bars and filling materials in reinforcing steel pipes, by providing a filling mortar between the steel pipe inner side and the reinforcing steel pipe in the steel pipe pile, and providing an anti-adhesion coating on the reinforcing bars in the reinforcing steel pipe In Runode, the first invention and the same effect can be obtained. Further, by providing an anti-adhesion coating on the reinforcing bars in the reinforcing steel pipe, it is possible to obtain an effect that the reinforcing bars and the filling material in the reinforcing steel pipe can be reliably prevented from sticking.

  According to the third invention, since the cross-sectional area of the reinforcing bar is set to be smaller than the cross-sectional area of the reinforcing bar in the outer part of the reinforcing steel pipe only in the inner part of the reinforcing steel pipe, Even if a crack occurs at the boundary portion between the base footing and the like, it is possible to prevent an abnormal maximization of local strain of the reinforcing bar in the cracked portion. In addition, by reducing the cross-sectional area of the reinforcing bar only in the inner part of the reinforcing steel pipe, it is possible to suppress the occurrence of the breaking of the reinforcing bar in advance other than the part restrained by the reinforcing steel pipe. An effect is obtained.

  According to the fourth invention, since the support ring having the rigidity or hardness equal to or higher than that of the steel pipe is provided on the foundation footing or the upper structure side, the portion contacting the steel pipe in the head portion of the steel pipe pile, The concrete part on the foundation footing side or the like can be received by the support ring without directly contacting the upper end of the steel pipe in the steel pipe pile. As a result, the end of the steel pipe pile can be received by the support ring, and the local force applied from the steel pipe pile can be dispersed by the support ring. As a result, the concrete part such as the foundation footing side can be crushed. It is possible to prevent the change in the rotational rigidity of the pile head due to this.

  According to the fifth invention, since the outer peripheral surface of the reinforcing steel pipe has a stopper, the integration of the reinforcing steel pipe and the filling mortar is enhanced, and the reinforcing steel pipe is securely held at a predetermined position in the steel pipe pile. The effect that it can do is acquired.

(A) is a longitudinal front view showing the pile head joint structure of the first embodiment of the present invention, and (b) is a longitudinal front view showing a part of (a) in an enlarged manner. (A) is a longitudinal front view showing a pile head joint structure of a second embodiment of the present invention, (b) is a longitudinal front view showing a part of (a) in an enlarged manner. (A) is a longitudinal front view showing a pile head joint structure of a third embodiment of the present invention, and (b) is a longitudinal front view showing a part of (a) in an enlarged manner. (A) is a longitudinal front view showing a pile head joint structure of a fourth embodiment of the present invention, and (b) is a longitudinal front view showing a part of (a) in an enlarged manner. In the case of the pile head joint structure of 4th Embodiment of this invention, it is a longitudinal front view which shows the state which has deformed the reinforcing bar. It is a vertical front view which shows the pile head junction structure of 5th Embodiment of this invention. It is a vertical front view which shows the conventional pile head joining structure. In the case of the conventional pile head joining structure, it is a vertical front view which shows the state in which the reinforcing bar is locally pulled out and stretched and distorted. (A) is a figure which expands and shows the vicinity of the state which the reinforcing bar of FIG. 8 expands locally, and is distorted, and (b) is a figure which shows the strain distribution of the part. FIG. 10 is a longitudinal sectional front view showing a state where the compression force acts on the reinforcing bar in a state where the pile head is locally pulled out from the state shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 shows a pile head joint structure according to the first embodiment. In this embodiment, the foundation footing 1 made of reinforced concrete or the superstructure 1a made of reinforced concrete and the reinforcing bar 3 arranged at the head of the steel pipe pile 2 are arranged from the central longitudinal axis of the steel pipe pile 2, and the pile head reinforcement The bar arrangement diameter is reduced from the central longitudinal axis of the steel pipe pile 2. At this time, the foundation footing 1 made of reinforced concrete or the upper structure 1a made of reinforced concrete and the head of the steel pipe pile 2 are not integrated and rigidly coupled by concrete, or are rigidly coupled by restraining reinforcing bars or the like. It may be a semi-rigid joint that is joined by adhesion of the upper and lower parts of the reinforcing bar 3. By doing in this way, the pile head joint part by the reinforcing bar 3 is made into the semi-rigid connection, and it is set as the pile head joint structure which accept | permits a micro rotation of a pile head.

  In the head portion of the steel pipe pile 2, a plurality of reinforcing steel pipes 4 are arranged at intervals such as equiangular intervals. The reinforcing steel pipe 4 is disposed so as to straddle the boundary surface 5 at the joint portion between the steel pipe pile 2 and the foundation footing 1 or the upper structure 1a. The length L (see FIG. 1 (b)) for inserting the upper end of the reinforcing steel pipe 4 into the foundation footing 1 or the upper structure 1a is determined by the bending moment M acting on the pile head during a large earthquake. Even if a crack 9 (see FIG. 5) occurs at the boundary between the footing 1 or the upper structure 1a and the head of the steel pipe pile 2, the length may be set so that the intermediate part of the reinforcing bar 3 is not exposed. The length L into which the upper end portion of the reinforcing steel pipe 4 is inserted is set by design.

  Each reinforcing steel pipe 4 has an inner diameter larger than the reinforcing bar diameter so as to surround each reinforcing bar 3 arranged in the steel pipe pile head, and the reinforcing steel pipe 4 shorter than the reinforcing bar length of the reinforcing bar 3 Has been.

  Further, each reinforcing bar 3 is disposed so as to penetrate the inside of the reinforcing steel pipe 4, and between the reinforcing bar 3 and the inner peripheral surface of the reinforcing steel pipe 4, a mortar 6 or a filling material corresponding to mortar is provided. Filled and cured. Moreover, between the steel pipe 7 inner side and the steel pipe 4 for reinforcement in the steel pipe pile 2, it arrange | positions suitably and is provided so that the mortar 6 may be driven and hardened, and the filling mortar 8a may be formed. In addition, although the formwork provided in the steel pipe pile 2 in order to support the filling mortar 8a in each embodiment was abbreviate | omitted in FIG. 1, of course, the said formwork may be provided.

  As described above, by arranging the reinforcing steel pipe 4 so as to straddle the boundary surface 5 at the joint portion between the steel pipe pile 2 and the foundation footing 1 or the upper structure 1a, the crack 9 occurred in the vicinity of the boundary part. In the portion, the rebar 3 is prevented from being exposed, and the reinforcing steel pipe 4 and the hardened mortar 6 in which deformation is constrained thereby, or the filling material corresponding to the mortar, the buckling of the rebar 3 in the portion where the crack 9 is generated. Is preventing. More specifically, by adopting the structure as in the above embodiment, even when a crack 9 occurs in the pile head joint during a large earthquake, the reinforcing steel pipe 4 and its reinforcement are deformed in the direction perpendicular to the axis of the intermediate part of the reinforcing bar 3. The steel pipe 4 is restrained together with the mortar 6 or the like to prevent buckling or breakage of the reinforcing bar 3 and a semi-rigid joint structure in which the rotational rigidity of the pile head is prevented from changing.

  In the first embodiment shown in FIG. 1, the lower part of the reinforcing bar 3 is provided so as to penetrate downward from the lower end of the reinforcing steel pipe 4, and is fixed to the filling mortar 8a.

  The intermediate portion of the reinforcing bar 3 such as a different diameter steel bar in the reinforcing steel pipe 4 is not provided with a wrinkle (node, protrusion) as a small diameter shaft portion 15 having a uniform cross section in the longitudinal direction. The adhesion between the intermediate portion of the reinforcing bar 3 and the mortar 6 or the filling material corresponding to the mortar is reduced.

  In the embodiment shown in FIG. 1, the cross-sectional area of the reinforcing bar 3 is smaller than the cross-sectional area of the reinforcing bar 3 in the outer part of the reinforcing steel pipe 4 only in the inner part of the reinforcing steel pipe 4, and is the small-diameter shaft part 15. ing. Thus, by setting the diameter of the rebar 3 middle part (small-diameter shaft part 15) small over the length dimension of the reinforcing steel pipe 4, the cross-sectional area is made small and the cross-sectional area of the rebar 3 middle part is set small. The axial force of the tensile force and the compressive force is borne equally over the entire portion. Thereby, in the case of this embodiment, although the elongation by elastic deformation or plastic deformation in the portion (small-diameter shaft portion 15) where the cross-sectional area of the reinforcing bar 3 is small increases, as in the conventional case, in the portion of the crack 9, The local maximum of local distortion is prevented. By reducing the cross-sectional area of the intermediate portion of the reinforcing bar 3 only at the inner portion of the reinforcing steel pipe 4, it is possible to suppress the breakage of the reinforcing bar 3 other than the portion restrained by the reinforcing steel pipe 4 in advance. Can do.

  In the said 1st Embodiment, what has set the cross-sectional area small is used for the rebar 3 intermediate part as the small diameter axial part 15 in which the cross section without a bend is uniform in a longitudinal direction. The rebar 3 as described above may be appropriately manufactured by hot working or by cutting. Here, as a method of manufacturing the reinforcing bar 3 having a small cross-sectional area by cutting, there is a method of partially cutting the ready-made reinforcing bar 3. According to this, in the cutting portion, the cross-sectional area of the reinforcing bar 3 can be reduced, and at the same time, the nodes of the reinforcing bar 3 are not cut. For this reason, when cutting is used, it is possible to efficiently manufacture the unbonded reinforcing bar 3 by having a small cross-sectional area and no nodes of the reinforcing bar 3. Therefore, it is more desirable to manufacture the reinforcing bar 3 partially free of nodes by cutting, rather than unbonding by providing an anti-adhesion film on the reinforcing bar 3. However, the present invention is not limited to these, and other methods may be used. In some cases, a plurality of reinforcing bars 3 having different outer diameters and a bar-shaped reinforcing bar having a uniform cross section may be configured by screw joining or the like.

  When the reinforcing steel pipe 4 and the reinforcing bar 3 are arranged across the steel pipe pile 2 and the foundation footing 1 or the upper structure 1a as described above, the reinforcing bar 3 is disposed through the reinforcing steel pipe 4 in advance. Thus, the reinforcing steel pipe reinforcing bar is preferably formed by filling and hardening a mortar 6 or a filling material corresponding to the mortar. And in the state which has arrange | positioned and hold | maintained the lower part of the reinforcing steel pipe reinforcement in the steel pipe pile 2, the concrete 8 is filled in the steel pipe pile 2, and it hardens | cures, and the reinforcing steel pipe 4 and the reinforcing bar 3 are put into a predetermined position. Can be arranged. Thereafter, the foundation footing 1 or the upper structure 1a made of reinforced concrete may be built on the steel pipe pile 2 so as to embed the upper part of the reinforcing steel pipe 4 and the reinforcing bar 3.

  As described above, the cross-sectional area of the intermediate portion of the reinforcing bar 3 in the reinforcing steel pipe 4 may be smaller than that of the other parts, but the cross-sectional area may be the same as that of the other parts.

  If the cross-sectional shape of the reinforcing bar 3 in the reinforcing steel pipe 4 is uniform and there is no wrinkle, it will correspond to the reinforcing bar 3 and the mortar 6 or the mortar even if the filling material corresponding to the mortar 6 or the mortar is filled and cured. Since the adhesion with the filling material is weak, when a tensile force or a compressive force is applied to the reinforcing bar 3 at the time of an earthquake, an edge cutting state occurs. Moreover, in order to prevent adhesion between the reinforcing bar 3 and the mortar 6 or the filling material corresponding to the mortar, an anti-adhesion film or the like is provided in advance in the intermediate part of the reinforcing bar 3 disposed in the reinforcing steel pipe 4. It may be left. As said adhesion prevention film, you may use well-known materials, such as a mold release agent, oil paint, asphalt, for example.

  The flat cross-sectional form of the steel pipe pile 2 and the reinforcing steel pipe 4 may be a square, a hexagon, or the like in addition to a circle. Moreover, you may make it use the steel pipe 7 of cylindrical shapes, such as a triangle and an ellipse, as the plane cross-sectional form of the steel pipe 4 for reinforcement.

  FIG. 2 shows a pile head joint structure according to the second embodiment. In the first embodiment, the lower part of the reinforcing bar 3 is lengthened, the fixing length is secured at the lower part of the reinforcing bar 3, and the fixing is made on the filling mortar 8a. However, in the second embodiment, the fixing plate 10 is disposed on the lower side of the reinforcing steel pipe 4, the lower end side of the reinforcing bar 3 is inserted into the fixing plate 10, and fixing such as nuts disposed on the lower side of the fixing plate 10 is performed. The metal fitting 11 is locked. With such a structure, it is not necessary to make the lower part of the reinforcing bar 3 long, and the amount of the filling mortar 8a can be reduced. Even in such a configuration, as in the case of the above-described embodiment, even if a crack 9 occurs in the pile head joint portion during a large earthquake, the reinforcing steel pipe 4 and the reinforcing steel pipe are deformed in the direction perpendicular to the axis of the intermediate portion of the reinforcing bar 3. 4 is restrained together with the mortar 6 and the like filled in the inside. Thereby, it is set as the semi-rigid joining structure which prevented buckling or fracture | rupture of the reinforcing bar 3 and suppressed changing the rotational rigidity of the pile head. Other configurations are the same as in the case of the first embodiment described above, and thus the same reference numerals are used and description below is omitted.

  FIG. 3 shows a pile head joint structure according to the third embodiment. In this embodiment, the reinforcing steel pipe 4 is provided with irregularities on the outer peripheral surface of the reinforcing steel pipe 4 in the steel pipe pile 2 side portion and has the stopper 12. Integration of the reinforcing steel pipe 4 and the filling mortar 8a is enhanced by providing a large number of irregularities 12 on the outer peripheral surface of the reinforcing steel pipe 4 at intervals in the axial direction and the circumferential direction. It is a form. By embedding and fixing the reinforcing steel pipe 4 in the filling mortar 8a, the reinforcing steel pipe 4 can be reliably held at a predetermined position in the steel pipe pile 2. Even in such a configuration, as in the case of the above-described embodiment, even if a crack 9 occurs in the pile head joint portion during a large earthquake, the reinforcing steel pipe 4 and the reinforcing steel pipe are deformed in the direction perpendicular to the axis of the intermediate portion of the reinforcing bar 3. 4 is constrained with the mortar 6 and the like filled in 4 to prevent buckling or breaking of the rebar 3 and to prevent a change in rotational rigidity of the pile head. Other configurations are the same as those of the second embodiment.

  FIG. 4 shows a pile head joint structure according to the fourth embodiment. In this embodiment, in addition to the case of the first embodiment, the base footing 1 or the upper structure 1a side has a rigidity equal to that of the steel pipe pile 2 or a portion that contacts the upper end of the steel pipe 7 at the steel pipe pile head or This is a form in which a support ring 13 made of a material having hardness is provided. For example, a ring-shaped steel flat plate is used as the support ring 13. A gibber 14 such as a stud diver is fixed to the support ring 13 as appropriate. The diver 14 is embedded and fixed to the base footing 1 or the upper structure 1a corresponding thereto, and the support ring 13 is fixed to the base footing 1. Etc. are fixed. With the lower surface of the bearing ring 13 placed on the steel pipe pile 2, the foundation footing 1 side is built, and the concrete 8 is placed on the filling mortar 8a after the bar placement work on the foundation footing 1 side. Thus, the basic footing 1 side is constructed. Therefore, the steel pipe 7 upper end surface in the steel pipe pile 2 and the lower surface of the support ring 13 are in a metal touch state between the steel members.

  When the steel support ring 13 as shown in FIG. 4 is provided, the head of the steel pipe pile 2 is slightly rotated when a bending moment M acts on the pile head as shown in FIG. Even so, the local force applied from the steel pipe pile 2 can be dispersed by the support ring 13, and a part of the upper end of the steel pipe 7 in the steel pipe pile 2 corresponds to the reinforced concrete foundation footing 1 or the foundation footing. Will not sink into part of the superstructure (made of concrete or reinforced concrete). Therefore, as shown in FIG. 8, when there is no support ring 13, there is a risk of crushing the concrete part such as the foundation footing 1 side, but by providing the support ring 13, the steel pipe 7 in the steel pipe pile 2 is It is possible to prevent crushing of the concrete portion such as the foundation footing 1 side. When the concrete part on the foundation footing 1 side is crushed, the rotational rigidity of the pile head changes, but the concrete part on the foundation footing 1 side is prevented from collapsing. This prevents changes in the rotational rigidity of the pile head due to crushing.

  Such a support ring 13 made of steel or the like may be applied to the second embodiment or the third embodiment. In addition, what is necessary is just to make the form of the lower surface of the support ring 13 into forms, such as a circular ring or a rectangular ring, according to the form of the upper end surface of the steel pipe 7 in the steel pipe pile 2. FIG.

  In the form shown in FIG. 4, the upper part of the reinforcing steel pipe 4 and the intermediate part (small-diameter shaft part 15) of the reinforcing bar 3 are located on the foundation footing 1 or a part on the upper structure side corresponding to the case of the first embodiment. Also has a long dimension. By doing in this way, even if a crack 9 occurs in the pile head joint at the time of a large earthquake, the intermediate part of the reinforcing bar 3 is prevented from being exposed, and the deformation of the intermediate part of the reinforcing bar 3 in the direction perpendicular to the axis is for reinforcement. It restrains with the mortar 6 etc. with which it fills in the steel pipe 4, prevents buckling or a fracture | rupture of the reinforcing bar 3, and suppresses that the rotational rigidity of a pile head changes. The form shown in FIG. 4 not only suppresses the change in rotational rigidity of the pile head, but also prevents the collapse of the concrete 8 portion such as the foundation footing 1 described above, the buckling of the rebar 3 or the breakage due thereto, Easy removal of adhesion between the reinforcing steel pipe 4 and the reinforced mortar 8a in the reinforcing steel pipe 4 and destruction of the reinforcing steel 3 other than the parts restrained by the reinforcing steel pipe 4 are preceded. This is a desirable embodiment in that the suppression of the above can be realized at the same time.

  FIG. 6 shows a pile head joint structure of the fifth embodiment. This form is the form made into the steel pipe 4 for a reinforcement larger diameter than the steel pipe 4 for a reinforcement of each said embodiment. A plurality of rebar 3 intermediate portions (small-diameter shaft portions 15) arranged at the heads of the steel pipe piles 2 are arranged in the large-diameter reinforcing steel pipe 4 at an equal angular interval and the like. Accordingly, an anti-adhesion film is provided at the intermediate part of each reinforcing bar 3 and the mortar 6 or a curable filling material corresponding thereto is filled between the inside of the large diameter reinforcing steel pipe 4 and the outer peripheral surface of each reinforcing bar 3. And hardened. In this embodiment, since the plurality of reinforcing bars 3 are arranged in the large-diameter reinforcing steel pipe 4, the number of reinforcing steel pipes 4 can be reduced. Further, the plurality of reinforcing bars 3 and the reinforcing steel pipe 4 are unitized in advance by being filled with a mortar 6 filled in the reinforcing steel pipe 4 or a curable filling material corresponding thereto and cured. It is set as the form which arrangement | positioning of the reinforcing bar 3 of the steel pipe pile head and the steel pipe 4 for reinforcement becomes easy. Even in such a configuration, as in the case of the above-described embodiment, even if a crack 9 occurs in the pile head joint portion during a large earthquake, the reinforcing steel pipe 4 and the reinforcing steel pipe are deformed in the direction perpendicular to the axis of the intermediate portion of the reinforcing bar 3. 4 can be restrained together with the mortar 6 filled in the inside. Thereby, it is set as the semi-rigid joining structure which prevented buckling or fracture | rupture of the reinforcing bar 3 and suppressed changing the rotational rigidity of the pile head. Since other configurations are the same as those in the above-described embodiment, the same reference numerals are used and description below is omitted.

  When the present invention is carried out, as a filling material corresponding to mortar, for example, a high flow grout material or the like may be used.

  When practicing the present invention, the intermediate portion of the reinforcing bar 3 may not be the small-diameter shaft portion 15, and the cross-sectional areas of the upper and lower portions and the intermediate portion of the reinforcing bar 3 may be the same cross-sectional area. In such a case, an adhesion preventing film may be provided in the middle part of the reinforcing bar 3.

DESCRIPTION OF SYMBOLS 1 Foundation footing 1a Superstructure 2 Steel pipe pile 3 Reinforcement 4 Reinforcement steel pipe 5 Boundary surface 6 Mortar 7 Steel pipe 8 Concrete 8a Filling mortar 9 Crack 10 Fixing plate 11 Fixing bracket 12 Slip stopper 13 Bearing ring 14 Givel 15 Small diameter shaft part 20 Reinforcing bar 21 Exposed steel bars

Claims (5)

  In the pile head joint structure that allows the micro-rotation of the pile head as a semi-rigid joint between the foundation footing or the upper structure and the pile head with the rebar, so as to surround the rebar arranged in the steel pipe pile head, A reinforcing steel pipe having an inner diameter larger than that of the reinforcing bar and having a length shorter than the reinforcing bar length of the reinforcing bar is disposed, and the reinforcing steel pipe is straddled across the boundary surface at the joint portion of the steel pipe pile and the foundation footing or the upper structure. Further, the reinforcing bar is disposed so as to penetrate the inside of the reinforcing steel pipe, and a filling material is filled and hardened between the reinforcing bar and the inner peripheral surface of the reinforcing steel pipe. A pile head joint structure characterized in that a filling mortar is provided between an inner side of a steel pipe and the reinforcing steel pipe, and no reinforcing bar is provided on a reinforcing bar in the reinforcing steel pipe.   In the pile head joint structure that allows the micro-rotation of the pile head as a semi-rigid joint between the foundation footing or the upper structure and the pile head with the rebar, so as to surround the rebar arranged in the steel pipe pile head, A reinforcing steel pipe having an inner diameter larger than that of the reinforcing bar and having a length shorter than the reinforcing bar length of the reinforcing bar is disposed, and the reinforcing steel pipe is straddled across the boundary surface at the joint portion of the steel pipe pile and the foundation footing or the upper structure. Further, the reinforcing bar is disposed so as to penetrate the inside of the reinforcing steel pipe, and a filling material is filled and hardened between the reinforcing bar and the inner peripheral surface of the reinforcing steel pipe. A pile head joint structure characterized in that a filling mortar is provided between a steel pipe inner side and the reinforcing steel pipe, and an adhesion preventing coating is provided on a reinforcing bar in the reinforcing steel pipe.   The pile according to claim 1 or 2, wherein the cross-sectional area of the reinforcing bar is set to be smaller than the cross-sectional area of the reinforcing bar in the outer portion of the reinforcing steel pipe only in the inner portion of the reinforcing steel pipe. Head joint structure.   4. A bearing ring having rigidity or hardness equal to or higher than that of the steel pipe is provided on a portion of the foundation footing or superstructure side, which is in contact with the steel pipe in the steel pipe pile head. The pile head joint structure of any one of these.   The pile head joint structure according to any one of claims 1 to 4, further comprising a stopper on an outer peripheral surface of the reinforcing steel pipe.

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