JP3159380B2 - Connection device between pile head and structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The experience of earthquake disasters, including the 1995 Great Hanshin-Awaji Earthquake, has pointed out the importance of the seismic safety of not only the structure itself but also its basic structure. TECHNICAL FIELD The present invention relates to a pile foundation system that rationally and economically enhances seismic safety performance of a pile structure supporting a structure.

[0002]

2. Description of the Related Art When constructing structures on soft ground or water, various pile foundations such as steel piles, prestressed reinforced concrete piles, and cast-in-place concrete piles are used to support the structures. ing.

[0003] The original purpose of these piles was to support the weight of the structure in normal times. However, many cases of damage to the piles in past earthquake disasters have been reported. It has been pointed out that ensuring the seismic safety of piles and foundation structures in Japan is an important issue in seismic design.

[0004] The most general method for improving the seismic safety of piles is to use the seismic stress (= bending) generated in the pile body by forcible deformation due to horizontal force transmitted by a structure or horizontal displacement of the stratum surrounding the pile. This method is to increase the horizontal strength (= bending strength and shear strength) of the pile so as to withstand the moment and the horizontal shear strength. In Japan, various methods for improving the horizontal strength of piles have been developed and put into practical use for many years.

[0005] In the conventional method for increasing the horizontal strength of a pile, the pile body is integrated with an upper structure or a foundation footing by a rigid connection so as to restrain the rotational displacement of the pile head by a "pile head fixed" connection. Is a precondition. But,
Instead, a large bending moment and shear force are generated at the pile head during an earthquake in order to restrict the rotation of the pile head, and the connection condition of this pile head was changed from "fixed pile head" to "pile pin connection". It has been theoretically understood that the change greatly reduces the seismic stress generated at the pile head.

[0006] In recent years, some proposals have been made to realize this pile head pin connection, but a reasonable and economical connection method taking into account actual workability has not yet been established. This is the actual situation.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a "pile which can" reasonably and economically "realize a" pile head pin connection "which can greatly reduce the stress at the time of an earthquake generated in a pile body, especially a pile head. The main object is to provide a method of connecting the head with a structure above the body or a basic footing.

Further, the joining method according to the present invention is "easy to construct" and can be applied to various diversified pile bodies such as cast-in-place concrete piles, steel piles and concrete-based pre-casted piles. Pile head pin connection method ”is intended to be put into practical use.

[0009]

[Means for Solving the Problems] In the conventional foundation design for fixing the pile head, in the case of concrete piles, the main reinforcement inside the pile body is swallowed firmly into the foundation footing, and the main reinforcement of the pile is adhered to the reinforcing steel and concrete. In the case of a steel pile, in the case of a steel pile, a method of welding a reinforcing steel to a pile steel pipe head and fixing it in a basic footing, or a method of embedding a pile itself in the basic footing is adopted. The problem with this pile head fixing method is that by constraining the rotational displacement of the pile at the joint of the pile head, not only the vertical load but also the bending moment and the horizontal shear force that the pile body cannot withstand are transmitted. It is.

According to the present invention, a pile head joining method capable of transmitting a vertical load and a certain amount of horizontal shearing force at a joining position of a pile head, transmitting a bending moment as little as possible, or setting the transmitted moment to an arbitrary value is realized. I do. That is, it is the greatest goal of the present invention that "the restraining force of the rotational displacement of the pile head joint is smaller than the bending rigidity of the pile body and the rotational spring constant can be set to an arbitrary value". is there.

For this purpose, a superelastic material such as rubber is introduced as a rotary spring element into the pile head joint. Laminated rubber has been developed and put to practical use as a seismic isolation member for structures, but it is a device whose main purpose is to exert large horizontal shear deformation. In the present invention, a single rubber layer or a laminated rubber composed of a plurality of layers is used as a new rotary spring element after restricting its horizontal shear deformation function so that horizontal deformation of a certain degree or more does not occur. Is what you do.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing embodiments.

FIG. 1 shows a previously proposed example of using a laminated rubber seismic isolation device for improving the seismic safety of a pile. A laminated rubber seismic isolation device is installed on the pile head to make the pile head flexible in the horizontal direction by the horizontal deformation capability of the laminated rubber. However, this proposed diagram includes the following problems. . The first point is that since the structure 4 is buried in the ground in contact with the ground 1, the ground 1 and the structure 4 are integrated, and the horizontal deformation of the laminated rubber 3 is not exerted. It is a contradictory proposal.

Second, when it is assumed that the seismic isolation device 3 can exhibit the horizontal deformation d (cm), at least the vertical load P (t) supported by the seismic isolation device as shown in FIG. Δ
M = 1 / 2x (Pxd + Qxh) (tcm) An additional bending moment acting on the pile head is applied. Especially in the event of an earthquake, the vertical load P may easily be increased to about twice the long-term supporting load due to the fluctuation of the axial force due to the horizontal seismic force acting on the building and the vertical seismic motion. Occurs in the order of several tens of centimeters, so that this moment has an extremely large value. This phenomenon is called the Pδ effect, and is a large value that cannot be ignored for the bending strength of the pile head. Includes the contradiction that as the seismic isolation device exerts its seismic performance and deforms greatly to enhance the safety performance of the pile, the additional mormon acting on the pile head due to the Pδ effect increases.

FIG. 3 shows basic components of the main body of the present apparatus. The "laminated rubber body: 5" which provides a slight horizontal deformation and a main purpose elastic rotary spring, an upper structure or a basic hood. "Joint plate: 6 (61,62)" to transmit vertical load from pile to pile body and join them together, "Restrictor: To limit horizontal deformation of laminated rubber body to" clearance do "or less. 7 (71, 72) ". Fig. 3 (1)
(2) shows the case where the restricting body 7 (= 71) is arranged at the center of the plane of the laminated rubber body, and FIGS. 3 (3) and (4) show that the restricting body 7 (= 72) is This shows a case in which they are arranged. 3 (1) and 3 (3) show an example in which the laminated rubber body has a three-layer laminated structure, and FIGS. 3 (2) and 4) show an example in which the rubber body has one layer. As described above, the laminated rubber body includes a single rubber layer and a plurality of laminated rubber layers. Hereinafter, both of them will be referred to as a “laminated rubber body”.

FIG. 4 is an explanatory view of the basic mechanism of the pile head connecting device according to the present invention.
(2) shows a state in which a rotation angle θ is generated with a slight horizontal deformation do at the pile head during an earthquake. The present invention realizes a pile head joint close to a pin joint by releasing the rotational deformation constraint of the pile head without adding a severe bending moment to the pile head by the Pδ effect. Since the horizontal deformation δ of the laminated rubber body is limited to the clearance do or less by the constraint body 71 (72) provided at the center or the outer periphery of the laminated rubber body, a large additional moment cannot be generated at the pile head. The clearance do is set within a range that does not hinder both from the viewpoint of the bending strength of the laminated rubber body 5 and the pile. Since the allowable horizontal deformation do is limited to a small value, the present device can make the total thickness of the rubber layer much smaller than that of the conventional laminated rubber for the seismic isolation structure, and is therefore an economical device.

The bending rigidity KR of the laminated rubber body is KR = M /
θ = ERB · Ieq / tR (ERB: apparent elastic modulus relating to bending of the rubber body, Ieq: equivalent moment of inertia of the rubber body, tR: rubber thickness), and the plane size and thickness of the rubber body and Any value can be easily set according to the elastic coefficient of the rubber material. Therefore, the pile can be joined in a state almost close to a complete pin compared to the bending rigidity of the pile, or an elastic spring having a certain degree of rotational resistance can be joined. It is a major feature of the present invention that the rotational rigidity can be arbitrarily adjusted and set. Note that the vertical bearing capacity of the rubber layer and the laminated rubber body is extremely large and can be arbitrarily adjusted depending on the thickness and area of one rubber layer, so that the vertical load bearing and transmitting ability can be sufficiently and easily secured.

The above is the construction of the device and the basic mechanism. The following relates to a construction method for joining the present device to a pile and an upper structure or a foundation footing.

FIG. 5A shows the upper and lower joining plates 6 (61, 61).
In this method, the "stud bolt 8" is arranged outwardly of 62), and this is driven into the concrete of the upper and lower foundation footings and piles to be integrated. This method is suitable for cast-in-place concrete piles and relatively large diameter existing piles.

FIGS. 5 (2) and 3 (3) mainly show an existing pile made of concrete, which is welded to the lower joint plate 62 and inscribed in the center hole of the pile body. In this method, the body 9 "is integrated with the pile by inserting it into the center hole of the pile. FIGS. 5 (4) and 5 (5) show a method of integrating the “cap-like joint 10” welded to the lower joint plate 62 and circumscribing the pile by covering the pile. The method of the in-hole projecting joint 9 can be applied to a cast-in-place concrete pile by a method in which a center hole is once provided in a cast-in-place concrete pile and the joint 9 is driven into concrete.

FIG. 6 shows a state in which the connecting device of the present invention is integrated with a pile body and an upper footing as an example of a joining method using stud bolts shown in FIG. 5 (1). In the case of cast-in-place concrete pile, (1) in FIG.
(2) shows the case of a concrete-based precast pile, and (3) shows the case of a steel pipe pile. The joining methods shown in FIGS. 5 (4) and 5 (5) can be similarly applied to various types of piles.

FIG. 7 shows a method in which the joint body 9 (10) for joining the pile body with the restraining body 71 (72) for limiting the horizontal deformation of the laminated rubber body is shared by one member. FIG. 7 (1)
The protrusion-like joint 9 (971) embedded in the center of the pile extends to the height of the upper joint plate 61, and functions as the central restraint 71. In FIG. 7B, the cap-shaped joint 10 (1072) covering the outer periphery of the pile extends to the height of the upper joint plate 61, and functions as the outer periphery restricting member 72.

[0023]

As described above, when the pile head connecting device of the present invention is employed, the following effects can be obtained in joining the pile body to the structure or the foundation footing. (1) Not only can the pile head be a nearly perfect pin joint that transmits vertical load and horizontal shear force but does not transmit bending moment, but also has an elastic spring connection that has a rotational spring constant that can transmit any bending moment. can do. (2) As a result, the seismic stress generated at the head of the pile body is remarkably reduced, and the seismic safety performance of the pile body is dramatically improved, and at the same time, the pile body can be economically designed. (3) Within the range of horizontal deformation below the horizontal deformation limit value by the restraint of this device, the laminated rubber body functions as a seismic isolation device, so the seismic isolation effect is not applied to earthquake motion input up to a certain limit strength. Demonstrate. Therefore, (4) the seismic safety performance of the superstructure and its contents can be improved. (5) It has an excellent vibration damping effect against traffic vibration and micro vibration input in subways, railways, and highways. In addition, since the effect of blocking the high frequency component is excellent and the propagation of the individual sound can be blocked, there is an effect of preventing vibration and noise of the upper structure. (6) Since the horizontal deformation is limited to a small value by the restraint body, this device can be a rubber single layer or a very small number of laminated rubber bodies. It can be supplied at a much lower cost than seismic isolation devices. (7) After pile construction, installation is completed simply by installing this device on the pile head and placing foundation concrete or structural concrete on top of it, making construction simple, easy and quick. .

As described above, the present invention makes it possible to quickly construct a pile head pin joint or an elastic spring joint that can greatly reduce the stress of a pile body during an earthquake by a simple construction method. The present invention has made it possible to economically realize a pile foundation structure having excellent seismic safety performance.

[Brief description of the drawings]

Fig. 1 Previous proposal example of installing a laminated rubber seismic isolation device at the pile head

FIG. 2 is an explanatory view of a pile head in the proposed example of FIG. 1 (1) Configuration of pile, seismic isolation device, foundation footing and normal state (2) Piles due to horizontal deformation of laminated rubber seismic isolation device during an earthquake Illustration of additional moment acting on the head

FIG. 3 is an explanatory view of a configuration of a pile head coupling device according to the present invention. Example of (3) Laminated rubber body = 3 layers, example of outer peripheral constrained body (72) (4) Example of laminated rubber body = 1 layer, outer peripheral constrained body (72)

FIG. 4 is an explanatory view of an operation mechanism of the device of the present invention. (1) Normal state (2) State during an earthquake in which horizontal displacement do and rotation angle θ occur

[Fig. 5] Method of joining pile / superstructure (foundation footing) to this device (1) Joining method for both upper and lower joining plates using stud bolts (8) (2) Combining device with central constrained body (71) Upper joining plate: Stud bolt (8) Lower joining plate: Joining method using insertable joint (9) in pile hole (3) Joining device with outer peripheral restraining body (72) Upper joining plate: Stud bolt (8) Lower joint plate: Method of joining with insert joint (9) in pile hole (4) Joint device with central restraint (71) Upper joint plate: Lower side with stud bolt (8) Joining plate: Joining by cap-type joint (10) on the periphery of pile (5) Joining device with outer peripheral constraining body (72) Upper joining plate: Stud bolt (8) Lower joining plate: Cap type around pile Joining with joint (10)

[Fig. 6] Illustrative method of the state in which the pile, this device, and the upper foundation footing are joined together (in the case of using stud bolts for both upper and lower joint plates) (1) When applied to cast-in-place concrete pile (2) Concrete When applied to existing piles (3) When applied to steel pipe piles

Fig. 7: Example in which the pile joint (9, 10) also has the function of the deformation constraint (71, 72) (1) The case where the joint (9) inserted in the pile hole also serves as the deformation constraint (71) (2) When the cap joint (10) around the pile also serves as the deformation restraint (72)

[Explanation of symbols]

1: Pile 2: Pile 21: Pile head jointing concrete 22: Pile head concrete placing form 3: Laminated rubber seismic isolation device 4: Upper building 4 ': Foundation footing 5: Laminated rubber body 51: Rubber layer 52: Internal steel plate for lamination 6: Joint plate 61: Upper joint plate 62: Lower joint plate 7: Deformation restraint body 71: Center restraint body 72: Outer circumference restraint body 8: Stud bolt for connection 9: Pile hole Internal insertion type joint 10: Cap type junction around the pile 971: Insertion type joint inside the pile hole that also serves as the deformation constraint (71) 1072: Cap type junction around the pile also serving as the deformation constraint (72)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E02D 27/34 E02D 27/12

Claims (4)

(57) [Claims] 1. A structure, comprising: a head of a pile supporting a structure; and a footing of the structure or a foundation of the structure, wherein the head is disposed between the head of the structure or the foundation of the structure and the pile. A pair of joining plates respectively connected, A laminated rubber in which a single layer or a plurality of rubber layers and a steel sheet are laminated and disposed between the pair of joining plates, and one of the joining plates of the pair of joining plates One end is fixed, and the other end is extended in the direction of the other joining plate, and a predetermined clearance is maintained with the other joining plate, so that the horizontal
A binding device for connecting a pile head and a structure, comprising: a restraining body that restrains a shear deformation function . 2. A structure according to claim 1, further comprising: a pedestal supporting the structure, a head mounted on the structure or a foundation footing of the structure, and one of the piles connected to the foundation footing of the structure. A joining plate, the other joining plate joined to the pile body, a laminated rubber disposed between the one joining plate and the other joining plate, and laminated with a single layer or a plurality of rubber layers and a steel plate And fixing one end to the one joining plate, extending the other end so as to penetrate the laminated rubber layer and the other joining plate, and maintaining a predetermined clearance with the other joining plate in the horizontal direction. A coupling device for connecting a pile head and a structure, comprising: a constraint member that restricts displacement of the pile head. 3. The coupling device between a pile head and a structure according to claim 2, wherein the other end of the restraint body is inserted into a hole provided in a head of the pile body. A coupling device between a pile head and a structure. 4. One of the piles, which is arranged between the head of a pile supporting a structure and the footing of the structure or the structure, and which is connected to the footing of the structure or the structure. A joining plate, the other joining plate joined to the pile body, a laminated rubber disposed between the one joining plate and the other joining plate, and laminated with a single layer or a plurality of rubber layers and a steel plate Fixing one end to the head of the pile body, extending the other end so as to penetrate the other joint plate and reach the concave portion of the one joint plate, and provide a predetermined clearance with the one joint plate. And a restraining body for holding the horizontal direction to limit the displacement in the horizontal direction.