JP2012162983A - Foundation pile structure, precast concrete pile, and joint hardware for precast concrete pile and steel pipe pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foundation pile structure capable of soundly and smoothly transmitting a load when joining a precast concrete pile to a steel pipe pile, and to provide the precast concrete pile and joint hardware adequate thereto.SOLUTION: A precast concrete pile 1 is joined to a steel pipe pile 2 by applying welding. At the end of the precast concrete pile 1, an outer periphery steel pipe 3 is previously mounted for transmitting axial force on the end of the precast concrete pile 1. On the inner peripheral face of the outer periphery steel pipe 3, a protrusion 3a having one or more steps is previously provided. With the end of the outer periphery steel pipe 3 protruded from the position of an end plate 4 to form a protruded portion 3b, site circumferential joint welding can be applied between the precast concrete pile 1 and the steel pipe pile 2 in the same method as conventional one for both steel pipe piles. A vertical load to be transmitted while being shared with a concrete portion of the precast concrete pile 1 is gradually shifted from near a joint to the steel pipe pile 1 whose cross section is suddenly changed, to the side of the steel pipe pile 2 via the protrusion 3a of the outer periphery steel pipe 3 and the outer periphery steel pipe 3, and stably transmitted thereto.

Description

  The present invention relates to a foundation pile structure using a ready-made concrete pile (including PHC pile, RC pile, PRC pile, etc.) and a steel pipe pile, a ready-made concrete pile and a joint hardware usable for the foundation pile structure.

  With the recent increase in bearing capacity of foundation piles and the increase in design seismic force, the horizontal force during earthquakes and the ground displacement in the ground that are assumed at the time of design increase, resulting in pile bodies. An increasing number of cases use pile bodies with high yield strength so that they can withstand large cross-sectional forces.

  Ready-made concrete piles such as PHC piles (centrifugal prestressed concrete piles) are widely used for the foundation piles of buildings because they are inexpensive. Different types of prestressing force A type, B type, and C type are set for the PHC piles, and they are properly used according to the cross-sectional force generated.

  In the above environment, especially for upper piles where the generated bending moment is often increased, even the type C PHC pile with the greatest proof stress has increased the number of cases where it cannot withstand the generated sectional force. In many cases, SC piles (prepared concrete piles with shell steel pipes) having high horizontal strength and bending strength in which centrifugal concrete is placed inside the steel pipe are often used.

  The SC pile is a steel-concrete composite structure composed of a steel pipe and high-strength concrete, and has a sufficiently large bending strength and shear strength compared to a normal PHC pile, although it depends on the thickness of the steel pipe used. Moreover, naturally, if it is the same steel pipe plate thickness, it has big bending strength compared with a steel pipe pile.

  In addition, since SC piles are provided with end plates at the end portions in the same manner as PHC piles, they can be easily attached to the PHC piles by joining the end plates together and welding them in the same manner as joining conventional PHC piles. Can be joined.

  However, since SC pile is manufactured through a process of injecting concrete, centrifugal compacting and curing after preparing a steel pipe with an end plate attached in advance, the period required for manufacturing is long, and the steel pipe is used. Therefore, it is expensive.

  Therefore, there is a problem that the time for manufacturing the steel pipe and placing and curing the concrete cannot be kept, and the manufacturing may not be in time, or the cost of the foundation pile increases by applying the SC pile. .

  In order to solve the above problems, for example, in Patent Document 1, a steel pipe pile is applied instead of an SC pile to a place where a large proof stress is required, and a joint structure between a prefabricated concrete pile and a steel pipe pile is provided. The method used is disclosed.

JP 2003-232033 A Japanese Utility Model Publication No. 39-018126

  FIG. 5 (refer to Patent Document 2) and FIG. 6 show an example of a joint part structure of a conventional PHC pile (ready-made concrete pile 11). As described above, the end plates 14 are brought into contact with each other for surface contact. Joining is performed by securing and welding the edge. 5 and 6, reference numeral 6 denotes a welded portion, reference numeral 13 denotes a reinforcing band, and 15 denotes a PC steel material for introducing prestress.

  As shown in FIG. 7, when the steel pipe pile 2 is connected to the end structure of this conventional PHC pile as it is, the following problems occur.

  (1) Since the cross section of the end plate 14 does not change like the connection between PHC piles, PHC piles and SC piles, and the cross section changes rapidly at the joints, the vertical load and horizontal load acting on the pile foundation Issues remain in terms of smooth and sound communication. That is, in the PHC pile portion, the axial force shared by the thick concrete is concentrated on the steel pipe having a small thickness at the joint portion. At this time, a simple shaft is provided near the joint portion of the steel pipe pile 2. Not only the directional force but also the bending stress M from the end plate 14 of the PHC pile (the ready-made concrete pile 11) acts, so that it becomes a structural weak point.

  (2) If there is a gap between the steel pipe end face and the end plate, it may cause welding failure due to leakage of weld metal, etc., so it is necessary to strictly ensure the end face accuracy of the steel pipe pile 2 and the vertical accuracy at the time of pile connection, Problems remain from the viewpoint of ensuring the quality of welding in the field.

  In order to cope with such a problem, the following structure is disclosed in Patent Document 1 described above. That is, it is a structure in which a similar end plate is installed in advance at the end of the steel pipe pile on the side to be joined with the PHC pile so that the field welding can be performed in the same manner as the joining of the conventional PHC piles.

  However, in this structure, the problem (2) is solved, but the problem (1) is not solved. That is, the bending moment M of FIG. 7 acting on the end of the steel pipe pile 2 through the end plate 14 cannot be eliminated (the rigidity is improved by the double end plates, and the end of the steel pipe pile is acted on). Although it may be possible to expect an effect of slightly reducing the bending moment, it is still a structure in which the stress transmission changes abruptly at the joint).

  In addition, a structure in which a stiffener is installed and reinforced in advance at the end of the steel pipe pile that is to be joined with the PHC pile can be considered, but the processing is expensive and expensive. However, there is a problem that the problem (2) is not solved.

  In order to solve the above problem (2), it may be possible to further provide a stiffener (such as reinforcing the steel pipe pile and the corners of the end plate with a stiffener) in the structure of Patent Document 1. Becomes complicated and the material used increases, resulting in a very expensive structure.

  The present invention was made to solve the above problems, and relates to a joint pile structure composed of different types of piles in which a steel pipe pile is applied to a place where a large proof stress is required among foundation piles made of ready-made concrete piles. A foundation pile structure that can smoothly and soundly transmit the stresses caused by pushing, pulling, and bending to ensure the proof strength of the joint, and can be welded in the field in the same way as before. It aims at providing the ready-made concrete pile and joint hardware which can be utilized for this foundation pile structure.

  The foundation pile structure according to claim 1 of the present application is formed by joining a ready-made concrete pile and a steel pipe pile having a bending strength larger than that of the ready-made concrete pile, and the end of the ready-made concrete pile on the side to be joined to the steel pipe pile. Is provided with an outer peripheral steel pipe for axial force transmission provided with one or more protrusions on the inner peripheral surface, the end plate of the ready-made concrete pile is provided on the inner peripheral surface of the outer peripheral steel pipe, and the end of the outer peripheral steel pipe The portion is projected from the end plate position.

  The ready-made concrete piles here include PHC piles, RC piles, PRC piles and the like mainly composed of concrete, but do not include SC piles in which the entire pile has a steel-concrete composite structure.

  Moreover, although the structure which uses a steel pipe pile for the upper part of a ready-made concrete pile is fundamentally, it is not limited to this in particular, The shape pinched | interposed into a ready-made concrete pile may be sufficient.

  According to the present invention, for the sudden change in cross section between the ready-made concrete pile and the steel pipe pile to be connected, the protrusion is provided on the inner peripheral surface of the outer peripheral steel pipe provided at the end of the ready-made concrete pile, so that the ready-made concrete is provided. The load that is shared and transmitted by the concrete portion of the pile gradually shifts to the outer steel pipe side through the protrusions located on the inner peripheral surface of the outer steel pipe, and the vertical load can be stably transmitted to the steel pipe pile.

  The protrusions on the inner peripheral surface of the outer peripheral steel pipe are arranged with the number of steps necessary for transmitting the axial force at the joint position by the support pressure.

  A second aspect of the present invention is the foundation pile structure according to the first aspect, wherein the plate thickness of the outer peripheral steel pipe is not less than the plate thickness of the steel pipe pile.

  The present invention inherently addresses a sudden change in the cross section at the joint between a ready-made concrete pile and a steel pipe pile, and if the plate thickness of the outer peripheral steel pipe is smaller than the plate thickness of the steel pipe pile, Since it is disadvantageous, the thickness of the outer peripheral steel pipe of the concrete pile is limited to the thickness of the steel pipe pile or more (usually 9 mm or more).

  In addition, conventionally, a reinforcing band is attached to the end portion of the ready-made concrete pile mainly for the purpose of protecting the end portion of the concrete against the bending of the joint portion and securing the joint strength equivalent to the general portion of the pile body. .

  However, in the case of joining concrete piles, the end plates are in surface contact with each other, so this reinforcing band does not need a function of transmitting axial force. A steel plate of about 3.2 mm or a striped steel plate (checker plate) is used, and the projection height is as small as that of the striped steel plate.

  In the foundation pile structure according to claim 1 or 2, the length of the outer peripheral steel pipe is limited to 0.5 to 1.5 times the outer diameter of the ready-made concrete pile.

  In the present invention, the axial force is gradually transmitted with a certain length as a stress state in response to a sudden change in the cross section, and the length of the outer peripheral steel pipe is 0. 0 with respect to the outer diameter D of the ready-made concrete pile. 3D or more, preferably 0.5D or more is required. Moreover, since it will only increase cost even if it is too long, in Claim 3, it was set to 0.5-1.5D.

  In addition, in the case of the conventional reinforcement band, the length is also as short as about 0.25-0.5 times the outer diameter of a ready-made concrete pile from the reason described regarding Claim 2.

  As mentioned above, in the foundation pile structure of this invention, the end plate of the said ready-made concrete pile is provided in the internal peripheral surface of the said outer periphery steel pipe, and the edge part of the said outer periphery steel pipe is made to protrude from the said end plate position.

  The end plate in the present invention may have a minimum plate thickness required for manufacturing by centrifugal molding or for fixing a PC steel bar or the like.

  By attaching the end plate to the inner peripheral surface of the outer peripheral steel pipe with projections for axial force transmission and projecting the end of the outer peripheral steel pipe for a predetermined length, it is possible to perform field splice welding in the same way as conventional steel pipe piles .

  The outer peripheral steel pipe and the end plate may be integrated by welding or the like.

  The ready-made concrete pile according to claim 4 of the present application has a continuous or discontinuous protrusion of one or more stages on the inner peripheral surface at a connection end with the steel pipe pile with a plate thickness equal to or greater than the plate thickness of the steel pipe pile. An outer peripheral steel pipe for transmitting axial force is provided, an end plate of the ready-made concrete pile is provided on an inner peripheral surface of the outer peripheral steel pipe, and an end portion of the outer peripheral steel pipe is protruded from the end plate position. To do.

  The ready-made concrete pile according to claim 4 can be applied to the foundation pile structure according to claim 1 as it is.

  According to a fifth aspect of the present invention, in the foundation pile structure according to the fourth aspect, the projection is formed by a weld bead.

  In the present invention, considering the concrete thickness of the ready-made concrete pile and ensuring the reliable axial force transmission function, protrusions with a height of about 8 to 15 mm are formed on the inner surface of the outer peripheral steel pipe at a pitch of about 100 to 200 mm. It is good to install. In that case, it is economical to make the protrusion with a weld bead.

  In addition, if the protrusions are higher than necessary, there is a risk of inducing cracks in the concrete. Further, if the pitch is short, the axial force transmission by the protrusions becomes inefficient because the bearing strength of one protrusion is lowered, and if the pitch is too long, the outer peripheral steel pipe becomes long and uneconomical.

  The joint hardware according to claim 6 of the present application is a joint hardware for joining a ready-made concrete pile and a steel pipe pile, and has a plate thickness equal to or greater than the plate thickness of the steel pipe pile, and has one or more steps on the inner peripheral surface. An outer peripheral steel pipe for axial force transmission having continuous or discontinuous protrusions and an end plate of the prefabricated concrete pile are integrally formed, and an end plate of the prefabricated concrete pile is provided on an inner peripheral surface of the outer peripheral steel pipe, When joining a ready-made concrete pile and a steel pipe pile, the edge part of the said outer periphery steel pipe protrudes from the said end plate position, It is characterized by the above-mentioned.

  The length of the outer peripheral steel pipe, the height of the protrusions, the number of steps, the pitch, and the like can be considered in the same manner as described in the first, third, and fifth aspects, but are not necessarily limited.

  According to the present invention, the stress is transmitted through the protrusion on the inner peripheral surface of the outer peripheral steel pipe provided at the end of the ready-made concrete pile for the sudden change section where the ready-made concrete pile and the steel pipe pile are joined. The stress due to pushing, pulling and bending acting on the steel can be transmitted smoothly and soundly to ensure the strength of the joint.

  Moreover, the welding work in the field in the joining of a ready-made concrete pile and a steel pipe pile can be implemented by the same method as before, and it is excellent in workability.

  In addition, if the protrusion for facilitating the stress transmission in the suddenly changing section is formed with a weld bead, it is efficient and the manufacturing cost is low.

  FIG. 1 schematically shows the overall shape of a foundation pile structure according to the present invention. On a conventional common ready-made concrete pile 11 as a tip pile, for example, a ready-made according to claim 4 of the present invention is shown. It is assumed that the concrete pile 1 is connected, a steel pipe pile 2 having a high bending strength is connected as an upper pile, and the head of the steel pipe pile 2 is embedded in a foundation such as a footing.

  A ready-made concrete pile 11 as a tip pile has a reinforcing band 13 made of a conventional thin steel plate and an end plate 14 attached to both ends.

  For the ready-made concrete 1 of the present invention, in the example shown in FIG. 1, a reinforcing band 13 and an end plate 14 similar to those of a conventional ready-made concrete pile 11 are attached to the lower end, and a plurality of steps are provided on the inner peripheral surface at the upper end. An outer peripheral steel pipe 3 and an end plate 4 for axial force transmission provided with protrusions 3a are attached.

  The joining of the ready-made concrete pile 11 as the tip pile and the ready-made concrete 1 of the present invention is performed by abutting the end plate 14 and the end plate 4 together by welding similarly to the joining of the conventional ready-made concrete piles 11.

  In this example, the ready-made concrete 1 of the present invention and the steel pipe pile 1 are joined together by welding the upper ends of the outer peripheral steel pipes 3 and the lower ends of the steel pipe piles 2 that protrude upward from the end plates 4. .

  FIG. 2 and FIG. 3 show different forms for the portion A surrounded by the one-dot chain line in FIG.

  FIG. 2 shows an embodiment of a foundation pile structure not included in the present invention. The end of the outer peripheral steel pipe 3 for load transmission is in contact with the lower surface of the end plate 4 and the lower end of the upper steel pipe pile 1 is shown. Welded to the upper surface of the end plate 4.

  A plurality of projections 3 a are provided on the inner peripheral surface of the outer peripheral steel pipe 3 for load transmission. Further, the end portion of the PC steel material 5 is fixed to the end plate 4.

  FIG. 3 shows an embodiment of the invention according to the present invention. An end plate 4 is provided on the inner peripheral surface of the outer peripheral steel pipe 3 for load transmission, and the end of the outer peripheral steel pipe 3 protrudes from the position of the end plate 4. Thus, the protruding portion 3b is formed.

  As described above, by projecting the end portion of the outer peripheral steel pipe 3 by a predetermined length to form the protruding portion 3b, on-site circumferential welding is performed in the same manner as the conventional steel pipe pile with respect to the connection with the steel pipe pile 2. be able to.

  Although common to the embodiment of FIG. 2, since the axial force transmission is performed by the protrusion 3 a on the inner peripheral surface of the outer peripheral steel pipe 3 and the outer peripheral steel pipe 3 as shown in FIG. 4, the end plate 4 functions as a structural member. You don't have to expect Therefore, the end plate 4 may have a minimum plate thickness necessary for manufacturing by centrifugal molding or for fixing the PC steel bar 5 or the like.

  From the standpoints of ensuring rigidity and proof strength for smooth axial force transmission, ensuring proof strength against local stress in the vicinity of the protrusion 3a, and in-situ weld welding with the steel pipe pile 2, the thickness of the outer peripheral steel pipe 3 is the same as that of the steel pipe pile 2. The plate thickness (usually 9 mm or more) or more.

  Moreover, from the viewpoint of avoiding sudden changes in the stress state and transmitting the axial force gradually with a certain length, the length of the outer peripheral steel pipe 3 is about 0.3 to 1.5D, more preferably 0.5 to 1.5D. To the extent.

  As for the protrusions 3a, considering the concrete thickness of the ready-made concrete pile 1 and ensuring the reliable axial force transmission function, it is preferable to install the protrusions 3a of about 8 to 15 mm at a pitch of about 100 to 200 mm. It is economical to form the protrusion 3a with a weld bead.

  If the protrusion 3a is higher than necessary, there is a risk of inducing cracks in the concrete. If the pitch between the protrusions 3a is short, the axial force transmission by the protrusions 3a is inefficient (the bearing load resistance of one protrusion decreases), and if it is too long, the outer peripheral steel pipe 3 becomes long and uneconomical.

  The protrusion 3a arranges the number of steps necessary for transmitting the axial force at the joint position by the support pressure.

It is sectional drawing which shows the whole shape of the foundation pile structure of this invention. It is sectional drawing of the principal part which shows one form of a foundation pile structure. It is sectional drawing of the principal part which shows one Embodiment of the foundation pile structure of this invention. It is explanatory drawing which shows the stress transmission of the dissimilar pile joint part in this invention. It is an elevation view (left half is sectional drawing) which shows the junction part of the conventional PHC pile. It is detail sectional drawing of the junction part of the conventional PHC pile. It is explanatory drawing which shows the stress transmission of the conventional dissimilar pile joint part.

DESCRIPTION OF SYMBOLS 1 ... Ready-made concrete pile, 2 ... Steel pipe pile, 3 ... Outer peripheral steel pipe, 3a ... Protrusion, 3b ... Projection part, 4 ... End plate, 5 ... PC steel material, 6 ... Welding part,
DESCRIPTION OF SYMBOLS 11 ... Conventional ready-made concrete pile, 13 ... Reinforcement band, 14 ... End plate, 15 ... PC steel

Claims (6)

  A ready-made concrete pile and a steel pipe pile having a bending strength greater than that of the ready-made concrete pile are joined together, and the end of the ready-made concrete pile on the side to be joined with the steel pipe pile has one or more steps on the inner peripheral surface. An outer peripheral steel pipe for axial force transmission provided is provided, an end plate of the ready-made concrete pile is provided on an inner peripheral surface of the outer peripheral steel pipe, and an end portion of the outer peripheral steel pipe is protruded from the end plate position. A foundation pile structure characterized by   The foundation pile structure according to claim 1, wherein a thickness of the outer peripheral steel pipe is equal to or greater than a thickness of the steel pipe pile.   The foundation pile structure according to claim 1 or 2, wherein a length of the outer peripheral steel pipe is 0.5 to 1.5 times an outer diameter of the ready-made concrete pile.   At the connection end with the steel pipe pile, an outer peripheral steel pipe for axial force transmission having a plate thickness equal to or greater than the thickness of the steel pipe pile and having one or a plurality of continuous or discontinuous protrusions on the inner peripheral surface is provided. An end plate of the ready-made concrete pile is provided on an inner peripheral surface of the outer peripheral steel pipe, and an end portion of the outer peripheral steel pipe is protruded from the end plate position.   The ready-made concrete pile of Claim 4 with which the said protrusion is formed of the weld bead.   A joint hardware for joining a ready-made concrete pile and a steel pipe pile, having a plate thickness equal to or greater than the plate thickness of the steel pipe pile, and having an axial force having one or more continuous or discontinuous protrusions on the inner peripheral surface When the outer peripheral steel pipe for transmission and the end plate of the ready-made concrete pile are integrally formed, the end plate of the ready-made concrete pile is provided on the inner peripheral surface of the outer peripheral steel pipe, and the ready-made concrete pile and the steel pipe pile are joined Further, an end of the outer peripheral steel pipe protrudes from the end plate position, and the joint hardware of the ready-made concrete pile and the steel pipe pile.

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