JP4595545B2 - Joint structure of footing and pile - Google Patents

Description

  The present invention relates to a footing-pile coupling structure that couples a footing provided below a structure such as a column base and a pile installed below the footing and supporting the structure.

Conventionally used footing and pile coupling structures include those shown in FIGS.
The footing-pile joint structure shown in FIG. 10 fills the head of the pile 2 formed of a cylindrical steel pipe with the filling concrete 10 and extends the reinforcing bars 22 arranged in the filling concrete 10 upward. The footing 1 and the pile 2 are joined by burying the upper end side of the reinforcing bar 22 and the pile 2 in the footing concrete 6 forming the footing 1.

  The footing and pile coupling structure shown in FIG. 11 extends the reinforcing bar 22 joined to the outer peripheral surface of the pile 2 by welding or the like, and embeds the upper end side of the reinforcing bar 22 and the pile 2 in the footing concrete 6. The footing 1 and the pile 2 are combined. In addition, although not shown in particular, the reinforcing bars in the padded concrete and the reinforcing bars joined to the outer peripheral surface of the pile are extended upward, and the upper end side of these reinforcing bars and the pile is embedded in the footing concrete so that the footing and the pile are piled up. There is also a footing-pile connection structure that connects the two.

Further, as shown in FIG. 12, a footing-pile combined structure for connecting the footing 1 and the pile 2 by burying the upper end side of the pile 2 in the footing concrete 6 without arranging reinforcing bars in the pile 2. There is also.
However, the above-described footing-pile joint structure in which the footing-pile joint is a rigid joint causes the following problems.

  FIG. 13 shows the bending moment generated in the entire pile 2 as a distribution for each depth when a horizontal force generated during an earthquake is applied to the footing 1 in the coupled footing and pile structure as shown in FIG. It is a thing. In the figure, the solid line represents the connection between the footing and the pile as a solid connection, the broken line represents the connection between the footing and the pile as described later, and the semi-rigid connection as described later represents the connection between the footing and the pile. Is indicated by a one-dot chain line.

As shown in FIG. 13, when the footing and the pile are coupled rigidly, the horizontal pile generated during the earthquake is applied to the footing 1 as compared with the other two types of coupled structures. The pile head bending moment Mt generated in the head is increased. For this reason, it is necessary to increase the size of the piles, increase the amount of reinforcement to the footing and the foundation beam, etc., resulting in an increase in cost and a decrease in workability. Also, in the case of piles that require particularly high bearing capacity, such as when the structure is a high-rise building, etc., the pile head bending moment becomes excessive, making it difficult to design the pile head and reducing workability. It will occur.
The pile head fixing degree αr in FIG. 13 is expressed by the following formula (1).

Here, H is the bending stiffness of the pile (usually determined from the product of the elastic modulus E of the pile body and the cross-sectional secondary moment I of the pile), and Kp is the rotational spring stiffness of the pile head. Moreover, (beta) is a characteristic value of a pile, when the outer diameter of a pile is set to D and a ground spring coefficient is set to k, it calculates | requires by the following conditional expressions (2).
β = (k · D / 4H) ^1/4 (2)

For such a problem, when a horizontal force generated during an earthquake is applied to the footing, as a footing-pile combined structure capable of reducing a pile head bending moment generated in the pile head, for example, Patent Document 1 There are a coupling structure described and a coupling structure described in Patent Document 2.
As shown in FIG. 15, the coupling structure shown in Patent Document 1 is a pin coupling structure in which a pile head 24 is rotatably coupled to a structure 8 to release a pile head bending moment. Moreover, the coupling structure shown in Patent Document 2 is a roller coupling structure in which the pile head 24 is slidably coupled to the structure 8 so as to release the pile head bending moment, as shown in FIG. .

  With these coupling structures, the displacement amount of the pile head 24 is larger than the coupling structure in which the footing and the pile are rigidly coupled as shown in FIGS. Since the cross section of the main body of the pile 2 can be reduced, the cost is reduced. However, these footing-pile joint structures are complex joint structures having a rotation function, a slide function, and the like, and thus have problems such as a decrease in durability and workability and an increase in construction cost. In addition, the continuity between the pile 2 and the structure 8 is cut off by the rotation function and the slide function, and there is a problem that an unstable structure tends to be obtained particularly when a large-scale earthquake occurs. Furthermore, the rotational rigidity at the joint between the pile head 24 and the structure 8 varies depending on the load state (pushing force, pull-out force, axial force) acting on the joint between the pile head 24 and the structure 8. Therefore, it is difficult to perform an appropriate design evaluation.

For such a problem, there is a coupling structure described in Patent Document 3, for example, as a coupling structure between a footing and a pile that has a more stable structure and a simple structure. As shown in FIG. 17, this coupling structure is formed by coupling the footing 1 and the pile 2 via the coupling member 4, so that an intermediate state between the rigid coupling by the reinforcing bar and the coupling by the pin and the roller (semi-rigid coupling). ) To support the structure.
Japanese Patent Application No. 11-248106 (FIG. 1) Japanese Patent Application No. 2000-125325 (FIG. 4) Japanese Patent Laid-Open No. 2001-159142 (FIG. 2)

However, the joint structure described in Patent Document 3 has the following problems.
In the joint structure described in Patent Document 3, when a horizontal force generated during an earthquake is applied to the footing 1 and a bending moment is generated in the entire pile 2, the footing 1 is caused by three types of transmission mechanisms as shown in FIG. It is thought that it is transmitted to the pile 2 through the connecting member 4 from the top. Here, the three types of transmission mechanisms are a transmission mechanism based on the horizontal support pressure of the concrete indicated by A in the figure, a transmission mechanism based on the vertical offset support pressure (adhesive force) of the concrete indicated by B in the figure, It is the transmission mechanism in the end surface of the coupling member shown by C inside.

  In addition to the bending moment described above, axial force and shearing force are applied to the coupling member. Of the three types of transmission mechanisms described above, the transmission mechanism using the concrete horizontal support pressure and the concrete vertical displacement prevention For the transmission mechanism using the support pressure, the influence of the axial force is small. However, regarding the transmission mechanism at the end face of the coupling member, the amount of transmission of the bending moment changes depending on the magnitude of the axial force. That is, the greater the axial force in the pushing direction that acts on the coupling member, the greater the burden ratio on the bending moment to the transmission mechanism at the end face of the coupling member. On the other hand, the greater the axial force in the pulling direction that acts on the coupling member, the lower the rate of bending moment burden due to the transmission mechanism at the end face of the coupling member.

  FIG. 19 shows the relationship between the pile head fixing degree αr and the axial force ratio N / No (N: acting axial force, No: yield axial force load of the pile). The acting axial force N indicates an axial force that acts in the pushing direction when it is a positive value, and an axial force that acts in the pulling direction when it is a negative value. The pile head fixing degree αr obtained by the equation (1) is a numerical value indicating the degree of coupling, and when αr = 1, it is a rigid coupling, and when αr = 0, it is a pin coupling. Here, assuming that the pile and the ground horizontal resistance spring are elastic, the pile head action moment Mt is expressed by the following formula (3) and is proportional to the pile head fixing degree αr.

In the above formula (3), Q is a horizontal force acting on the pile head.
As shown in FIG. 19, the pile head fixing degree αr varies depending on the axial force acting on the coupling member. In other words, since the bending moment changes depending on the axial force acting on the coupling member, it is necessary to design the pile structure assuming the maximum axial force acting on the coupling member in the pushing direction. There is.

  In addition, when supporting a structure, the footing is often supported by multiple piles, but the magnitude of the axial force acting at the time of the earthquake varies depending on the foundation of each pile. Variation occurs, and the fluctuation of the load transmitted from the structure to the foundation of the pile becomes large and complicated. For this reason, in the case where the footing is supported by a plurality of piles, (a) it is difficult to properly evaluate the structural design for each pile. If the cross-sectional shape is changed for each pile, problems such as deterioration in workability occur.

  The present invention has been made paying attention to the above-described problems. By mitigating an increase in pile head fixing degree when an axial force in the pushing direction acts on the coupling member, (i) To provide a combined footing and pile structure that can reduce the increase in pile head working moment and (ii) reduce the variation in pile head working moment with respect to the acting axial force to reduce costs and improve workability. Is an issue.

In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention includes one or more footings and pile heads installed below the footings and filled with a filler. A footing and pile coupling structure coupled via a coupling member of
A plurality of detents are provided on the outer peripheral surface of the coupling member,
Wherein an upper end of said displacement-preventing is provided a coupling member while embedded in the footing, by embedding the lower end the displacement-preventing is provided in the coupling member to the filler of the pile head, and the footing The combination of the piles is a semi-rigid connection ,
A cushioning material is interposed between at least one of the upper end surface of the coupling member and the footing and between the lower end surface of the coupling member and the filler of the pile head.

According to the present invention, the cushioning material is interposed between at least one of the upper end surface of the coupling member and the footing and between the lower end surface of the coupling member and the filler at the pile head, so that transmission is performed at the end surface of the coupling member. It is possible to reduce the applied load.
In addition, said filler should just be what can transmit three types of force mentioned above between a footing and a pile head, For example, as what can be considered now, concrete, mortar, metal, resin, There are rubber, plaster, porcelain, asphalt, stone, and wood.

  Next, the invention described in claim 2 is the invention described in claim 1, wherein the cushioning material inserted between the upper end surface of the coupling member and the footing is a material having rigidity lower than that of the footing. The cushioning material formed and interposed between the lower end surface of the coupling member and the filler is formed of a material having lower rigidity than the filler.

Next, the invention described in claim 3 is a footing that joins a footing and a pile head that is installed below the footing and is filled with a filler via one or more connecting members. A pile connection structure,
A plurality of detents are provided on the outer peripheral surface of the coupling member,
Wherein an upper end of said displacement-preventing is provided a coupling member while embedded in the footing, by embedding the lower end the displacement-preventing is provided in the coupling member to the filler of the pile head, and the footing The combination of the piles is a semi-rigid connection ,
A gap portion is provided between at least one of the upper end surface of the coupling member and the footing and between the lower end surface of the coupling member and the filler of the pile head.
According to the present invention, since the gap is provided between at least one of the upper end surface of the coupling member and the footing and between the lower end surface of the coupling member and the filler of the pile head, the gap is transmitted at the end surface of the coupling member. Load can be reduced.

Next, the invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein the coupling member is arranged with its axis directed in the vertical direction, and the coupling member is coupled to the coupling member. Place the member with the axis facing up and down,
The coupling auxiliary member projects from the upper end surface and the lower end surface of the coupling member, and at least a part of the projecting portion from the upper end surface is embedded in the footing, and at least a part of the projecting portion from the lower end surface Embedded in the pile head filler.

Next, the invention described in claim 5 is the invention described in any one of claims 1 to 3, wherein the coupling member is arranged with its axis directed in the vertical direction, and the coupling member is The shaft is passed through the coupling auxiliary member that is longer than the coupling member with the axis in the vertical direction,
The upper end side of the coupling auxiliary member protrudes from the upper end surface of the coupling member, and at least a part of the protruding portion is embedded in the footing, and the lower end side of the coupling auxiliary member protrudes from the lower end surface of the coupling member. In addition, at least a part of the protruding portion is embedded in the pile head filler.

Next, the invention described in claim 6 is the invention described in claim 4 or 5, and is between the upper end surface of the coupling auxiliary member and the footing, and the lower end surface of the coupling auxiliary member and the pile head. A cushioning material is interposed between at least one of the fillers.
Next, the invention described in claim 7 is the invention described in claim 4 or 5, and is between the upper end surface of the coupling auxiliary member and the footing, and the lower end surface of the coupling auxiliary member and the pile head. A gap is provided in at least one of the fillers.

  According to the present invention, the load transmitted at the end face of the coupling member is reduced, and the increase in the pile head fixing degree when the axial force in the pushing direction is applied to the coupling member is reduced. It is possible to reduce the increase in head acting moment, and (ii) to reduce the variation in pile head acting moment with respect to the acting axial force. Can be obtained.

Next, embodiments of the present invention will be described with reference to the drawings.
First, the configuration of the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. In addition, about the structure similar to the past, it attaches | subjects and demonstrates the same code | symbol.
As shown in FIG. 1, the footing and pile coupling structure of the present embodiment couples the footing 1 and the pile 2 via a coupling member 4 arranged with its axis directed in the vertical direction. In addition, in the figure, although the state which has couple | bonded the footing 1 and the pile 2 via the one coupling member 4 is shown, it is not limited to this, The footing 1 and the pile 2 are You may couple | bond through two or more coupling members 4. FIG.

The footing 1 is formed of footing concrete 6 and is disposed below a structure 8 such as a column base. The pile 2 is a cylindrical steel pipe pile, and its head is filled with medium-filled concrete 10 as a filler, and is disposed below the footing 1.
The coupling member 4 is formed by filling a hollow steel pipe with concrete, and a plurality of stoppers 12 with the footing concrete 6 and the filling concrete 10 are provided on the outer peripheral surface thereof. The upper end side of the coupling member 4 is embedded in the lower end of the footing concrete 6 by a predetermined length, and the lower end side of the coupling member 4 is embedded in the upper end of the filling concrete 10 by a predetermined length. Here, it is assumed that at least one slip stopper 12 is embedded in each of the footing concrete 6 and the filling concrete 10.

  In the footing concrete 6, a cushioning material 14 a having a size covering the upper end surface of the coupling member 4 is interposed between the upper end surface of the coupling member 4 and the footing concrete 6. In addition, a cushioning material 14 b having a size covering the lower end surface of the connecting member 4 is interposed between the lower end surface of the connecting member 4 and the intermediate packed concrete 10 in the intermediate packed concrete 10.

  Depending on the shape of the coupling member 4, the cushioning materials 14 a and 14 b may be made of, for example, a monolithic one as shown in FIG. 2A or another material such as a cylindrical shape as shown in FIG. Filled and formed. Moreover, the thickness of the buffer materials 14a and 14b is given an appropriate value according to the size of the pile 2 and the weight of the superstructure. In this case, if it is a thickness of 10 mm or more, since it can respond also to a large pile, it becomes a more desirable form. Furthermore, in order to reduce the bending moment transmitted to the end face of the coupling member 4 with certainty, the cushioning materials 14a and 14b are less rigid than the footing concrete 6 or the intermediate-filled concrete 10 which are in contact with each other. To form. More preferably, the cushioning material 14a is formed of a material having a rigidity of 1/10 or less of the contacted footing concrete 6, and the cushioning material 14b is formed of a material having a rigidity of 1/10 or less of the infilling concrete 10 in contact. As the material of the buffer material 14 and another material to be filled, mortar, shaped steel, metal, resin, rubber, asphalt, gypsum, porcelain, stone, and the like are used.

Next, functions and effects of this embodiment will be described.
When a horizontal force generated during an earthquake or the like is applied to the footing 1, a bending moment generated by the horizontal force is transmitted from the footing 1 to the pile 2 via the coupling member 4.
At this time, the upper and lower end surfaces of the coupling member 4 have lower rigidity than the respective parts that are in contact with each other (desirably, the cushioning material 14a is made of the footing concrete 6 and the cushioning material 14b is made of the filling concrete 10; Since each of the cushioning members 14a and 14b having a sufficient thickness is disposed, the upper and lower end surfaces of the coupling member 4 are sufficiently lower in rigidity than other portions. For this reason, the bending moment generated by the horizontal force is higher in rigidity (a) the horizontal bearing pressure between the connecting member 4 and the filling concrete 10, and (b) the detent provided on the outer peripheral surface of the connecting member 4. The bending moment transmitted through the upper and lower end surfaces of the coupling member 4 is reduced.

  That is, according to the coupling structure of the footing and the pile according to the present embodiment, the bending moment transmitted on the upper and lower end surfaces of the coupling member 4 can be reduced. It is possible to mitigate the increase in pile head fixing degree that occurs when the action is applied. Therefore, it is possible to reduce the increase in pile head working moment and the variation in pile head working moment with respect to the acting axial force, thereby reducing costs and improving workability.

In addition, in the case of a combined structure in which the footing 1 is supported by a plurality of piles 2, it is possible to mitigate an increase in pile head fixing degree for each of the plurality of piles. Load can be homogenized, and the workability can be improved and the cost can be reduced.
In the footing and pile coupling structure of the present embodiment, a cushioning material 14 a is interposed between the upper end surface of the coupling member 4 and the footing concrete 6, and between the lower end surface of the coupling member 4 and the filled concrete 10. Although the cushioning material 14b is inserted, it is not limited to this. That is, if it is possible to reduce the bending moment transmitted on the upper and lower end surfaces of the coupling member 4, the gap between the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10. Of these, the cushioning material 14 may be inserted in only one of them.

  Further, in the footing and pile coupling structure of the present embodiment, the footing 1 is formed of the footing concrete 6, but is not limited to this, for example, mortar, shape steel, metal, resin, rubber, asphalt, gypsum Alternatively, other materials such as porcelain and stone may be used. Moreover, you may form the footing 1 with the outer frame formed with two or more types of materials, for example, a steel plate, and the concrete with which the inside of this outer frame is filled. That is, a structure in which a structure such as a column base and the head of the pile 2 can be connected so that a horizontal force generated during an earthquake or the like is applied to the footing 1 and a bending moment generated by this horizontal force can be transmitted to the pile 2. I just need it.

  Furthermore, in the footing and pile coupling structure of the present embodiment, the pile 2 is formed by a cylindrical steel pipe pile, but is not limited to this, and is formed by a steel pipe pile having a polygonal cross section. May be. Moreover, the pile 2 is not limited to a steel pipe pile, The pile currently used normally other than a steel pipe pile (for example, RC pile, PC pile, PHC pile, SC pile), a cast-in-place pile, etc. If it is.

  In the footing and pile coupling structure of the present embodiment, the coupling member 4 is formed of a steel pipe having a circular cross section, but is not limited to this, and the steel pipe having a polygonal cross section. May be formed. Furthermore, although the coupling member 4 is formed of a steel pipe, the present invention is not limited to this, but various concrete such as concrete, reinforced concrete, steel reinforced concrete, mortar, resin, rubber, asphalt, gypsum, porcelain, stone, etc. You may form with a material. In addition, the hollow portion of the coupling member 4 is filled with concrete, but the present invention is not limited to this. Instead of concrete, other materials such as mortar, resin, rubber, asphalt, gypsum, porcelain, and stone are filled. The hollow portion may be a void. Further, the coupling member 4 is formed of a hollow steel pipe, but is not limited to this, and may be formed by a solid structure, that is, by integral molding using the same material. As an example formed by integral molding using the same material, there are a steel column, a concrete column, and the like. As a special example, there is one formed by a shape steel such as an H-shaped steel. That is, the configuration of the coupling member 4 may be appropriately selected from the above-described elements according to the required design specifications.

  Moreover, in the footing and pile coupling structure of the present embodiment, the cushioning material 14 is formed by filling different materials into a columnar shape and a cylindrical shape according to the shape of the coupling member 4, but is limited to this. Instead, if the end surface of the coupling member 4 can be covered, the cross section may be formed in a polygonal shape, for example.

Next, the configuration of the second embodiment of the present invention will be described with reference to FIG. In addition, about the structure similar to 1st embodiment mentioned above, the same code | symbol is attached | subjected and demonstrated.
As shown in FIG. 3, the footing and pile coupling structure of the present embodiment has the same configuration as that of the first embodiment except for the following points. That is, in the footing concrete 6, a gap 16 a is provided between the upper end surface of the coupling member 4 and the footing concrete 6 instead of the cushioning material 14 a being interposed. Further, in the filling concrete 10, a gap 16 b is provided between the lower end surface of the coupling member 4 and the filling concrete 10, instead of the cushioning material 14 b interposed. In addition, let the shape of the space | gap part 16a, 16b be a shape which can cover the end surface of the coupling member 4, for example, a cross section becomes circular or a polygon.

Next, functions and effects of this embodiment will be described.
When a horizontal force generated during an earthquake or the like is applied to the footing 1, a bending moment generated by the horizontal force is transmitted from the footing 1 to the pile 2 via the coupling member 4.
At this time, since the gap portions 16a and 16b are provided on the upper and lower end surfaces of the coupling member 4, the upper and lower end surfaces of the coupling member 4 have sufficiently lower rigidity than other portions. For this reason, the bending moment generated by the horizontal force is higher in rigidity (a) the horizontal bearing pressure between the connecting member 4 and the filling concrete 10, and (a) the detent provided on the outer peripheral surface of the connecting member 4. The bending moment transmitted by the upper and lower end surfaces of the coupling member 4 is reduced.

  That is, according to the coupling structure of the footing and the pile according to the present embodiment, the bending moment transmitted on the upper and lower end surfaces of the coupling member 4 can be reduced. It is possible to mitigate the increase in pile head fixing degree that occurs when the action is applied. Therefore, it is possible to reduce the increase in pile head working moment and the variation in pile head working moment with respect to the acting axial force, thereby reducing costs and improving workability.

  In the footing and pile coupling structure of the present embodiment, a gap portion 16 a is provided between the upper end surface of the coupling member 4 and the footing concrete 6, and a gap is formed between the lower end surface of the coupling member 4 and the filling concrete 10. Although the part 16b was provided, it is not limited to this. That is, if it is possible to reduce the bending moment transmitted on the upper and lower end surfaces of the coupling member 4, the gap between the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10. Of these, a configuration in which the gap 16 is provided on only one side may be employed.

  Moreover, how to provide the space | gap part 16 is not limited to the method mentioned above. For example, at least one of the space between the upper end surface of the coupling member 4 and the footing concrete 6 and the space between the lower end surface of the coupling member 4 and the filling concrete 10 is a cylindrical member with the upper and lower surfaces closed, and the shaft is moved up and down. It is good also as the space | gap part 16 by inserting in the direction and forming the hollow part formed in the inside of this member. Further, a cylindrical member in which only a portion in contact with the coupling member 4 is closed between at least one of the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10. May be inserted with the shaft directed in the vertical direction, and a hollow portion formed inside the member may be used as the gap portion 16.

Here, the rigidity of the material forming the member is equal to or less than the rigidity of the footing concrete 6 if it is a member having a hollow portion as a gap portion 16a, or less than that of the filling concrete 10 if it is a member having a hollow portion as a gap portion 16b. To do. More preferably, the member having the hollow portion as the gap portion 16a is 1/10 or less of the footing concrete 6 and the member having the hollow portion as the gap portion 16b is made of a material having a rigidity of 1/10 or less of the filling concrete 10, respectively. Form. As a specific material of the member, a material similar to the cushioning materials 14a and 14b described in the first embodiment is used.
Other actions and effects are the same as those of the first embodiment described above.

Next, the configuration of the third embodiment of the present invention will be described with reference to FIGS. In addition, about the structure similar to 1st and 2nd embodiment mentioned above, the same code | symbol is attached | subjected and demonstrated.
As shown to Fig.4 (a), the coupling | bonding structure of the footing and a pile of this embodiment becomes the structure similar to 1st embodiment except for the following points. That is, the coupling auxiliary member 18 formed of a cylindrical hollow steel pipe that is longer than the coupling member 4 penetrates the coupling member 4 with its axis directed in the vertical direction. The upper end side of the coupling auxiliary member 18 protrudes from the upper end surface of the coupling member 4 and penetrates the buffer material 14 a, and the portion protruding from the buffer material 14 a is embedded in the footing concrete 6. The lower end side of the coupling auxiliary member 18 protrudes from the lower end surface of the coupling member 4 and penetrates the buffer material 14b. The portion protruding from the buffer material 14b is embedded in the filling concrete 10. Moreover, the inside of the coupling auxiliary member 18 is filled with concrete.

  As shown in FIG. 5, both the cushioning materials 14 a and 14 b are formed by filling different materials into, for example, a hollow cylindrical shape according to the shape of the coupling member 4, and the size through which the coupling auxiliary member 18 penetrates. Through-holes 20 are provided. Moreover, the thickness of the buffer materials 14a and 14b is given an appropriate value according to the size of the pile 2 and the weight of the superstructure. In this case, if it is a thickness of 10 mm or more, since it can respond also to a large pile, it becomes a more desirable form. Furthermore, in order to reduce the bending moment transmitted to the end face of the coupling member 4 with certainty, the cushioning materials 14a and 14b are less rigid than the footing concrete 6 or the intermediate-filled concrete 10 which are in contact with each other. To form. More preferably, the cushioning material 14a is formed of a material having a rigidity of 1/10 or less of the contacted footing concrete 6, and the cushioning material 14b is formed of a material having a rigidity of 1/10 or less of the infilling concrete 10 in contact. As the material of the buffer material 14 and another material, mortar, shaped steel, metal, resin, rubber, asphalt, gypsum, porcelain, stone, or the like is used. Although not particularly illustrated, the buffer material 14 may be, for example, a cylindrical solid tube provided with a through hole 20. Furthermore, the buffer material 14 may be formed in a shape having a polygonal cross section, for example, as long as it can cover the end face of the coupling member 4.

Next, functions and effects of this embodiment will be described.
In the coupling structure of the footing and the pile having such a configuration, since the coupling auxiliary member 18 functions as an axial force transmission member, even if a bending moment is transmitted to the upper and lower end surfaces of the coupling auxiliary member 18, the transmitted bending moment is transmitted. Used when there is little impact on pile head fixing degree.
Therefore, according to the coupling structure of the footing and the pile of the present embodiment, when a horizontal force generated during an earthquake or the like is applied to the footing 1, a bending moment generated by the horizontal force is transmitted from the footing 1 through the coupling member 4. Is transmitted to the pile 2.

  At this time, the upper and lower end surfaces of the coupling member 4 have lower rigidity than the respective parts that are inserted and in contact (desirably, the cushioning material 14a is the footing concrete 6 and the cushioning material 14b is the filling concrete 10; Since each of the cushioning members 14a and 14b having a sufficient thickness is disposed, the upper and lower end surfaces of the coupling member 4 are sufficiently lower in rigidity than other portions. For this reason, the bending moment generated by the horizontal force is higher in rigidity (a) the horizontal bearing pressure between the connecting member 4 and the filling concrete 10, and (a) the detent provided on the outer peripheral surface of the connecting member 4. The bending moment transmitted by the upper and lower end surfaces of the coupling member 4 is reduced.

  That is, according to the coupling structure of the footing and the pile according to the present embodiment, the bending moment transmitted on the upper and lower end surfaces of the coupling member 4 can be reduced. It is possible to mitigate the increase in pile head fixing degree that occurs when the action is applied. Therefore, it is possible to reduce the increase in pile head working moment and the variation in pile head working moment with respect to the acting axial force, thereby reducing costs and improving workability.

  In addition, in the coupling | bonding structure of the footing and the pile of this embodiment, it was set as the structure which the one coupling auxiliary member 18 penetrates to the one coupling member 4, However, It is not limited to this. That is, the coupling member 4 is formed of a cylindrical steel pipe, and the coupling member 4 is provided with two or more through-holes having a diameter through which the coupling auxiliary member 18 can penetrate. It is good also as a structure which the coupling auxiliary member 18 penetrates.

Moreover, the joining method of the coupling member 4 and the auxiliary coupling member 18 is not limited to the above method. An example is described below.
For example, FIG. 4B is an example in which one coupling auxiliary member 18 shown in FIG. 4A is divided into two coupling auxiliary members 18 a and 18 b, and the coupling auxiliary member is arranged from the upper end surface of the coupling member 4. The upper end portion of 18 a is protruded from the lower end surface of the coupling member 4, and the lower end portion of the coupling auxiliary member 18 b protrudes with its axis directed in the vertical direction. A part of the coupling auxiliary members 18 a and 18 b is embedded in the concrete of the coupling member 4.

FIG. 4C is an example in which the two coupling auxiliary members 18 a and 18 b in FIG. 4B are joined to the upper and lower end surfaces of the coupling member 4. As a joining method of the coupling auxiliary member 18 and the coupling member 4, there are, for example, welding, use of an adhesive, and a method of creating a single unit depending on the material of the coupling member 4 and the coupling auxiliary members 18a and 18b.
FIG. 4D shows a case where the diameter of the coupling auxiliary member 18 shown in FIG. In this case, the cushioning material inserted in the upper and lower end surfaces of the coupling member 4 becomes small, and sufficient load reduction is not performed. Therefore, the cushioning members 14c and 14d are attached to the upper and lower end surfaces of the coupling auxiliary member 18 so as to cover the upper and lower end surfaces, respectively, so that sufficient load reduction is performed in the coupling member 4 and the coupling auxiliary member 18 as a whole. The configuration of the cushioning materials 14c and 14d is the same as that of the cushioning materials 14a and 14b described in the first embodiment.
Although FIG. 4 and FIG. 5 have been described using the cushioning materials 14a to 14d, the same effect can be obtained by providing the gap portions 16a to 16d instead.

Moreover, in the coupling structure of the footing and the pile of the present embodiment, the inside of the coupling auxiliary member 18 is filled with concrete. However, the present invention is not limited to this. For example, mortar, resin, rubber, asphalt, plaster, porcelain, stone material Such a material may be filled, and the coupling auxiliary member 18 may not be filled with concrete. Furthermore, although the coupling auxiliary member 18 is formed by a steel pipe having a circular cross section, the present invention is not limited to this, and may be formed by a steel pipe having a polygonal cross section. Moreover, although the coupling auxiliary member 18 is formed of a steel pipe, the present invention is not limited to this, and various types of concrete such as concrete, reinforced concrete, steel reinforced concrete, and materials such as mortar, resin, rubber, asphalt, gypsum, porcelain, and stone are used. May be formed. Moreover, although the coupling auxiliary member 18 is formed of a hollow steel pipe, the present invention is not limited to this, and may be formed by a solid structure, that is, integral molding using the same material. As an example formed by integral molding using the same material, there are a steel column, a concrete column, and the like. As a special example, there is one formed by a shape steel such as an H-shaped steel. That is, the configuration of the coupling auxiliary member 18 may be appropriately selected from the above-described elements according to the required design specifications.
Other actions and effects are the same as those of the first embodiment described above.

  Next, with reference to FIG.6 and FIG.7, the pile head in the coupling | bonding structure of the footing and a pile of this invention (invention example: FIG. 1) and the conventional coupling structure of a footing and a pile (conventional example: FIG. 17). The relationship between the degree of fixation αr and the axial force ratio N / No is shown. Here, the acting axial force N indicates an axial force acting in the push-in direction when it is a positive value, and indicates an axial force acting in the pull-out direction when it is a negative value.

FIG. 6 shows the configuration of the test body used in this test. As shown in the figure, in the test body used in this test, the upper end side of the connecting member 4 is embedded 600 mm in the lower end of the footing 1 formed of the footing concrete 6 having a thickness of 800 mm. A buffer material 14 a is interposed between the upper end surface of the member 4 and the footing concrete 6. Further, in the pile 2 in which the head of a cylindrical steel pipe pile having an outer diameter of 800 mm, a plate thickness of 12 mm, and a length of 1800 mm is filled with the intermediate filling concrete 10, the lower end side of the coupling member 4 is the upper end inside the intermediate filling concrete 10. The buffer member 14 b is interposed between the lower end surface of the coupling member 4 and the intermediate-filled concrete 10. The buffer materials 14a and 14b are both formed to have a thickness of 10 mm and a Young's modulus of about 1.0 N / mm ² . The coupling member 4 is formed by filling concrete into a cylindrical steel pipe having an outer diameter of 400 mm and a plate thickness of 18 mm.

The results of experiments using such a test specimen are shown in FIG. The N value of the assumed ground is 5. As indicated by ● in the figure, no cushioning material 14 is interposed between the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10. In the combined structure, the fluctuation of the pile head fixing degree αr is about 0.37 to 0.61.
On the other hand, as indicated by ▲ in the figure, the thickness is 10 mm between the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10. In the joint structure in which the cushioning materials 14a and 14b are formed, the fluctuation of the pile head fixing degree αr is about 0.35 to 0.45. Therefore, the coupling member 14a, 14b formed with a thickness of 10 mm is interposed between the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10, respectively. In the structure, it was confirmed that the pile head fixing degree αr was reduced in both size and variation.
Therefore, the effect of the buffer material 14 was confirmed by this experiment.

Next, with reference to FIG. 8 and FIG. 9, the result of having performed the experiment similar to Example 1 with respect to the test body from which the magnitude | size differs from the test body used in Example 1 is shown.
FIG. 8 shows the configuration of the test body used in this test. As shown in the figure, in the test body used in this test, the upper end side of the connecting member 4 is embedded 300 mm in the lower end of the footing 1 formed of the footing concrete 6 having a thickness of 600 mm. A buffer material 14 a is interposed between the upper end surface of the member 4 and the footing concrete 6. Further, in the pile 2 in which the head of a cylindrical steel pipe pile having an outer diameter of 400 mm, a plate thickness of 9 mm, and a length of 1100 mm is filled with the intermediate packed concrete 10, the lower end side of the coupling member 4 is the upper end of the intermediate packed concrete 10. The buffer member 14 b is interposed between the lower end surface of the coupling member 4 and the intermediate-filled concrete 10. The buffer materials 14a and 14b are both formed with a thickness of 5 mm and a Young's modulus of about 1.0 N / mm ² . The coupling member 4 is formed by filling concrete into a cylindrical steel pipe having an outer diameter of 200 mm and a plate thickness of 15 mm.

  The results of experiments using such a test specimen are shown in FIG. The N value of the assumed ground is 5. As indicated by ● in the figure, no cushioning material 14 is interposed between the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10. In the combined structure, the fluctuation of the pile head fixing degree αr is about 0.39 to 0.58.

On the other hand, as indicated by □ in the figure, the thickness is 5 mm between the upper end surface of the connecting member 4 and the footing concrete 6 and between the lower end surface of the connecting member 4 and the filled concrete 10. In the joint structure in which the cushioning members 14a and 14b are formed, the pile head fixing degree αr varies about 0.40 to 0.45. Therefore, the coupling member 14a, 14b formed with a thickness of 5 mm is interposed between the upper end surface of the coupling member 4 and the footing concrete 6 and between the lower end surface of the coupling member 4 and the filling concrete 10, respectively. In the structure, it was confirmed that the pile head fixing degree αr was reduced in both size and variation.
Therefore, the effect of the buffer material 14 was confirmed by this experiment.

It is a figure which shows the coupling | bonding structure of the footing and pile of 1st embodiment of this invention. It is a figure which shows the shock absorbing material of 1st embodiment of this invention. It is a figure which shows the coupling | bonding structure of the footing and pile of 2nd embodiment of this invention. It is a figure which shows the coupling | bonding structure of the footing and pile of 3rd embodiment of this invention. It is a figure which shows the buffer material of 3rd embodiment of this invention. It is a figure which shows the structure of a test body. It is a figure which shows the relationship between a pile head fixing degree and an axial force ratio. It is a figure which shows the structure of a test body. It is a figure which shows the relationship between a pile head fixing degree and an axial force ratio. It is a figure which shows the connection structure of the conventional footing and a pile. It is a figure which shows the connection structure of the conventional footing and a pile. It is a figure which shows the connection structure of the conventional footing and a pile. It is a figure which shows a pile head bending moment. It is a figure which shows the horizontal force added to a footing at the time of the occurrence of an earthquake. It is a figure which shows the connection structure of the conventional structure and a pile. It is a figure which shows the connection structure of the conventional structure and a pile. It is a figure which shows the connection structure of the conventional footing and a pile. It is a figure which shows the transmission mechanism of a bending moment. It is a figure which shows the relationship between a pile head fixing degree and an axial force ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Footing 2 Pile 4 Coupling member 6 Footing concrete 8 Structure 10 Filled concrete 12 Slip stopper 14 Cushioning material 16 Cavity 18 Joint auxiliary member 20 Through hole 22 Reinforcement 24 Pile head

Claims (7)

A footing-pile coupling structure that couples a footing and a pile head installed below the footing and filled with a filler via one or more coupling members,
A plurality of detents are provided on the outer peripheral surface of the coupling member,
Wherein an upper end of said displacement-preventing is provided a coupling member while embedded in the footing, by embedding the lower end the displacement-preventing is provided in the coupling member to the filler of the pile head, and the footing The combination of the piles is a semi-rigid connection ,
A cushioning material is inserted between at least one of the upper end surface of the coupling member and the footing and between the lower end surface of the coupling member and the filler of the pile head. Bond structure.   The cushioning material inserted between the upper end surface of the coupling member and the footing is formed of a material having lower rigidity than the footing, and the cushioning material inserted between the lower end surface of the coupling member and the filler is The footing-pile joint structure according to claim 1, wherein the footing-pile joint structure is formed of a material having a rigidity lower than that of the filler. A footing-pile coupling structure that couples a footing and a pile head installed below the footing and filled with a filler via one or more coupling members,
A plurality of detents are provided on the outer peripheral surface of the coupling member,
Wherein an upper end of said displacement-preventing is provided a coupling member while embedded in the footing, by embedding the lower end the displacement-preventing is provided in the coupling member to the filler of the pile head, and the footing The combination of the piles is a semi-rigid connection ,
The coupling between the footing and the pile, wherein a gap is provided between at least one of the upper end surface of the coupling member and the footing and between the lower end surface of the coupling member and the filler of the pile head. Construction. The coupling member is arranged with its axis facing up and down, and the coupling auxiliary member is arranged on the coupling member with its axis facing up and down,
The coupling auxiliary member projects from the upper end surface and the lower end surface of the coupling member, and at least a part of the projecting portion from the upper end surface is embedded in the footing, and at least a part of the projecting portion from the lower end surface 4. The footing-pile coupling structure according to claim 1, wherein the pile is embedded in the pile head filler. 5. The coupling member is arranged with the axis facing up and down, and a coupling auxiliary member that is longer than the coupling member is passed through the coupling member with the axis facing up and down,
The upper end side of the coupling auxiliary member protrudes from the upper end surface of the coupling member, and at least a part of the protruding portion is embedded in the footing, and the lower end side of the coupling auxiliary member protrudes from the lower end surface of the coupling member. 4. The footing-pile coupling structure according to claim 1, wherein at least a part of the projecting portion is embedded in the filler of the pile head. 5.   A cushioning material is interposed between at least one of the upper end surface of the coupling auxiliary member and the footing and between the lower end surface of the coupling auxiliary member and the filler of the pile head. The combined structure of footing and pile described in 4 or 5.   5. A gap is provided in at least one of the space between the upper end surface of the coupling assisting member and the footing and between the lower end surface of the coupling assisting member and the filler of the pile head. Or the footing and pile combined structure described in 5.

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