JP6694751B2 - Connection structure of SC pile and steel column - Google Patents

Description

  The present invention relates to a joint structure of SC piles and steel columns.

  Conventionally, for example, when a pillar member of an existing building is used as a pillar member (steel frame pillar) of a building to be newly constructed, it is brought into a construction site of a new building and a pair of pillar members arranged at predetermined positions are joined together. A ring panel method is used as one of the methods (see, for example, Patent Document 1). Further, it has been proposed and put into practical use to use a pile head ring socket construction method as a means for joining a steel pipe pile (support pile / pile foundation) and a column member (for example, refer to Patent Document 2).

  In such a construction method, a tubular steel ring socket is installed so as to include the lower end of the upper pillar member and the upper end of the lower pillar member and the joint where the pile heads of steel pipe piles are abutted, and the ring The gap between the socket, joint and ring socket is filled with mortar or concrete filler. Thus, the pair of upper and lower pillar members, and the upper pillar member and the steel pipe pile can be joined via the ring socket and the filler.

JP, 09-184201, A JP, 2009-013602, A

  On the other hand, if the upper pile part of the support pile is a SC pile (concrete pile with outer shell steel pipe) and the middle pile part and the lower pile part are also PHC piles (pretension method centrifugal force high strength prestressed concrete pile), Compared with the case where the entire support pile is a steel pipe pile, the cost can be significantly reduced (about 40 to 50% in the trial calculation example).

  Therefore, it has been strongly desired to develop a method capable of suitably joining the SC pile and the steel frame column by the pile head ring socket construction method.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a joint structure capable of suitably joining an SC pile and a steel frame column.

  In order to achieve the above object, the present invention provides the following means.

  A joint structure of an SC pile and a steel column of the present invention is a structure for joining an SC pile forming at least an upper pile portion of a support pile and a steel column, and a pile head of the SC pile and the pile head. A cylindrical ring socket provided so that the lower end portion of the steel column disposed above is placed inside and encapsulated therein, and is integrally provided on the ring socket and protrudes inward from the inner surface of the ring socket. The ring socket side bearing member provided, the SC pile side bearing member that is integrally provided on the pile head of the SC pile and projects outward from the outer peripheral surface of the pile head, and the steel column Filling between the steel column side bearing member integrally provided at the lower end portion and protruding outward from the outer surface of the steel column, the ring socket, the pile head of the SC pile, and the lower end portion of the steel column. The ring socket, the pile head portion of the SC pile, and the joint filling concrete that integrates the lower end portion of the steel column are configured.

  Here, in the present invention, the steel column is any one of a circular steel pipe, a square steel pipe, an H-shaped steel, and a CFT (concrete-filled steel pipe).

  Further, in the joint structure of the SC pile and the steel column of the present invention, it is desirable that the elastic limit proof strength is set according to the following formulas (1), (2), (3), and (4).

Here, the total area of _{P a} elastic limit strength _is, I _{F C} 'is Bearing Strength of SC piles (inner steel pipe) side pressure bearing member near the _concrete, I _{A R} is SC piles (inner steel pipe) side pressure bearing member , O _F C _'ring socket Bearing strength (external steel pipe) side pressure bearing member near the concrete, _O a _R is the total area of the ring socket (outer steel pipe) side pressure bearing member, F _C is the joint filling concrete Compressive strength, _I D is the outer diameter of the steel pipe of the SC pile, _I t is the thickness of the steel pipe of the SC pile, _O D is the outer diameter of the ring socket, and _O t is the thickness of the ring socket.

Further, in the joint structure of the SC pile and the steel column of the present invention, the ring socket side bearing member and the SC pile side bearing member use bearing members of the same shape. It is desirable that the number of materials is larger than that of the SC pile side bearing members.

  According to the joining structure of the SC pile and the steel column of the present invention, it becomes possible to suitably join the SC pile and the steel column by using the pile head ring socket construction method. As a result, SC piles can be added to the applicable range of the pile head ring socket construction method instead of high-cost steel pipe piles, and the cost of the support piles can be reduced by, for example, about 40 to 50%, resulting in a significant cost reduction. It will be possible.

It is a perspective view showing a joining structure of a SC pile and a steel frame pillar concerning one embodiment of the present invention. It is a figure which shows the example of the support pile of the joining structure of the SC pile and steel frame column which concerns on one Embodiment of this invention. It is sectional drawing which shows the joining structure of the SC pile and steel frame column which concern on one Embodiment of this invention. It is a figure which shows the test body used in (A) partial model experiment (punching experiment) of a verification experiment. It is a figure which shows the application method (application device) of the (A) partial model experiment (punching experiment) of a verification experiment. It is an experimental result of the (A) partial model experiment (punching experiment) of a verification experiment, and is a figure which shows the load of each test body, and the relationship of displacement of an application point. It is the figure which compared the experimental value of elastic limit proof stress with the calculated value. It is a figure which shows the test body used in (B) joining part experiment of a verification experiment. It is a figure which shows the application method (application device) of the joint experiment of (B) of a verification experiment. It is a figure which shows the loading program of the joint experiment of (B) of a verification experiment. It is an experimental result of the (B) joining part experiment of a demonstration experiment, and is a figure which shows the shearing force of the pile of each test body, and the relationship of a deformation angle. It is an experimental result of the (B) joining part experiment of a verification experiment, and is a figure which compared the skeleton curve of each test body. It is an experimental result of the (B) joining part experiment of a verification experiment, and is a figure which shows the relationship between the deformation | transformation angle of the pile of each test body, and the amount of pull-outs. It is a figure which shows the definition of the protrusion amount of a pile. It is an experimental result of the (B) joining part experiment of a demonstration experiment, and is a figure which compared the estimated value and the experimental value of yield strength and maximum proof stress. It is an experimental result of a verification experiment and is a figure which compared the initial rigidity of each test body.

  Hereinafter, a joint structure of an SC pile and a steel column according to an embodiment of the present invention will be described with reference to FIGS. 1 to 16.

  First, as shown in FIGS. 1 and 2, the support pile 1 of the present embodiment is an SC pile in a range (upper pile portion 1a / pile head portion) to which the joint structure of the SC pile and the steel column according to the present invention is applied. (Steel Composite Concrete Piles; concrete piles with steel pipes for outer shells) 2 and PHC piles (straight piles, knot piles), steel pipe piles, etc. in other areas (support pile 1 middle pile portion 1b and lower pile portion 1c) It is formed using. The middle pile portion 1b and the lower pile portion 1c may be SC piles 2.

  On the other hand, the steel column 3 of the present embodiment is formed by using any of a circular steel pipe, a square steel pipe, an H-shaped steel, and a concrete-filled steel pipe (CFT).

  As shown in FIGS. 1, 2, and 3, the joint structure 10 of the SC pile and the steel column of the present embodiment has a pile head of the SC pile 2 and a steel column 3 arranged on the pile head. A tubular steel ring socket 4 provided so as to enclose the lower end of the pile inside, and a pile head filling concrete 5 that is filled inside the pile head side of the SC pile 2. A joint that is filled between the ring socket 4 and the pile head of the SC pile 2 and the lower end of the steel column 3 to integrate the ring head of the ring socket 4 and the SC pile 2 with the lower end of the steel column 3. It is configured by including the filling concrete 6.

  It should be noted that a connecting beam may be provided integrally with the ring socket 4 (portion) depending on the condition of the ground. At this time, the connecting beam may be joined to the ring socket 4 using an outer diaphragm or the like.

  A non-shrink mortar 7 (or concrete) is laid on the pile head of the SC pile 2, and the steel column 3 is mounted on the non-shrink mortar 7 with its lower end abutted. The level is adjusted by the non-shrink mortar 7.

  As shown in FIG. 3, the ring socket 4 is integrally provided with a ring socket side bearing member 11 which projects inward from the inner surface thereof and extends in the circumferential direction to be connected. The pile head of the SC pile 2 is integrally provided with the SC pile side bearing member 12 that projects outward from the outer peripheral surface of the pile head (outer shell steel plate) and extends in the circumferential direction to be connected. The steel column 3 is provided at its lower end with a steel column side bearing member 13 that projects outward from the outer surface of the steel column 3 and extends in the circumferential direction to be connected.

  These pressure bearing members 11, 12 and 13 are members for surely transmitting stress between the members and for preventing shifts between the members, and are integrally attached to each member by welding. The bearing members 11, 12 and 13 may be welded and attached in the factory before construction, or may be welded and attached on site.

  The ring socket-side bearing member 11, the SC pile-side bearing member 12, and the steel column-side bearing member 13 are vertically spaced from each other, and the ring socket 4, the pile head of the SC pile 2 and the lower end of the steel column 3 are provided. Multiple units are provided in each section. Further, in the joint structure 10 of the SC pile and the steel frame column of the present embodiment, the number of the ring socket side bearing members 11 is made larger than the number of the SC pile side bearing members 12.

  In the joint structure 10 of the SC pile and the steel column of the present embodiment, the elastic limit proof stress thereof is set according to the following formulas (5), (6), (7), and (8).

Here, the total area of _{P a} elastic limit strength _is, I _{F C} 'is Bearing Strength of SC piles (inner steel pipe) side pressure bearing member near the _concrete, I _{A R} is SC piles (inner steel pipe) side pressure bearing member , O _F C _'ring socket Bearing strength (external steel pipe) side pressure bearing member near the concrete, _O a _R is the total area of the ring socket (outer steel pipe) side pressure bearing member, F _C is the joint filling concrete Compressive strength, _I D is the outer diameter of the steel pipe of the SC pile, _I t is the thickness of the steel pipe of the SC pile, _O D is the outer diameter of the ring socket, and _O t is the thickness of the ring socket.

  Then, when connecting the support pile 1 and the steel column 3 by using the joint structure 10 of the SC pile and the steel column of the present embodiment having the above-described configuration, first, the support pile 1 is driven into the ground. When dismantling an existing building and constructing a new building, an existing pile may be used.

  Next, the pile head filling concrete 5 is filled in the pile head portion of the SC pile 2 in the upper pile portion of the support pile 1 as needed. Moreover, non-shrink mortar 7 (or concrete) is laminated on the pile head. At this time, the thickness of the non-shrink mortar 7 is adjusted to correct the construction error in the vertical direction.

  Next, level concrete 8 is placed around the pile and the ring socket 4 of the outer steel pipe is set. At this time, the position of the ring socket 4 is adjusted to correct the horizontal construction error. When there is a connecting beam, the beam may be connected at this stage.

  Then, the upper steel column 3 is accurately built in the ring socket 4 and installed on the pile head (non-shrink mortar 7) of the SC pile 2 and the ring socket 4 is filled with the joint filling concrete 6. .. Instead of using the non-shrink mortar 7, it is possible to arrange the steel columns 3 with a gap between them and the head of the pile, and to fill the gap with concrete. At this time, it is preferable that the gap (the distance between the pile head and the lower end of the steel frame column 3 is 100 mm or more).

  Thereby, in the joint structure 10 (pile head ring socket construction method) of the SC pile and the steel column of the present embodiment, the support pile 1 (pile foundation / SC pile 2) is absorbed by a simple work while absorbing the construction error of the pile 1. It becomes possible to join the steel column 3 with

  Further, in the joint structure 10 of the SC pile and the steel frame column of the present embodiment, it becomes possible to suitably join the SC pile 2 and the steel column 3 by using the pile head ring socket construction method. That is, the SC pile 2 can be added to the applicable range of the pile head ring socket construction method.

  Therefore, according to the joint structure 10 of the SC pile and the steel column of the present embodiment, at least the upper pile portion of the support pile 1 is formed by the SC pile 2 instead of the high-cost steel pipe pile, and the cost of the support pile 1 is, for example, It can be reduced by about 40 to 50%, and a significant cost reduction can be achieved.

  Here, a demonstration test for confirming the performance of the joint structure 10 (joint portion of the pile head ring socket construction method) of the SC pile and the steel column of the present embodiment will be described. In addition, in this proof experiment, two types of experiments, (A) partial model experiment (punching experiment) and (B) joint experiment, were performed.

(A) In the partial model experiment (punching experiment), the stress transmission mechanism by the bearing members 11, 12, 13 (effect of the compression strut by the SC pile side bearing member 12) was confirmed, and the above equation (5) was used. ~ It was done to evaluate the validity of equation (8).
(B) The joint experiment was performed to confirm the validity of the pile head ring socket construction method for SC piles and to evaluate the validity of the above formulas (5) to (8). Further, a structural experiment using the SC pile 2 with the expanded tensile axial force limited was conducted to confirm the applicable range.

[(A) Partial model experiment (punching experiment)]
First, the experimental outline of (A) partial model experiment (punching experiment) will be described.
Two bodies shown in Table 1 and FIG. 4 were used as test bodies. The experimental parameter is the number (1 or 2) of the bearing members 12 arranged in the SC pile 2. The assumed failure mode is bearing failure of the concrete 6 near the SC pile side bearing material, and in order to prevent the bearing pressure failure of the concrete 6 near the ring socket (outer steel pipe) side bearing material 11 from preceding. The number of socket-side bearing members 11 was made larger than the number of SC pile-side bearing members 12 (three).

Steel pipe ○ -318.5 × 6.9 (STK490), internal concrete thickness 70mm (Fc = 105N / mm ² ) was used for SC pile 2 of the test body, and ○ -for ring socket (outer steel pipe) 4. A circular steel pipe of φ457.2 × 12 (STK490) was used.

  Further, FB-6 × 6 (SS400) was used as the bearing members 11 and 12, and both side fillet welds were attached to predetermined positions on the outside of the SC pile 2 and the inside of the ring socket 4.

The embedded length of the SC pile 2 is 1.0 Dc (SC pile outer diameter: 318.5 mm), and the normal joint concrete (24-18-13-N) with the nominal strength of 24 N / mm ² is joined to the double steel pipe part. It was filled as filled concrete 6.

  Table 2 shows the mechanical properties of the steel materials used, and Table 3 shows the compressive strengths of the SC pile 2 and the joint filling concrete 6. The concrete strength of the SC pile 2 is a reference value, which is a test result using a test piece obtained by removing cores from the SC pile material manufactured in the same lot as the test body.

A method of applying force to the test body is shown in FIG.
The force applied was a static monotonic force applied up to the limit load (3MN) of the force applying device. The test body (10) was installed without restraining the lower end (ring socket 4) in the horizontal and rotational directions, and was applied to the upper end of the upper end of the test body (SC pile 2) with a hydraulic jack via a ball seat. ..

The experimental results will be described below.
(Destructive property)
FIG. 6 shows the relationship between the load of the test body SC-1 and the test body SC-2 and the displacement of the applied point. In addition, Table 4 shows the elastic limit proof stress and the ratio of the maximum load (load limit: 3MN) to the elastic limit proof stress of each test body.
Here, the elastic limit proof stress is defined as a load point (1/3 slope factor method) at which the tangential rigidity related to load deformation is reduced to 1/3 of the initial rigidity.

  After the elastic behavior was exhibited up to about 2 mm in the test body SC-1 and about 3 mm in the test body SC-2, the decrease in rigidity became remarkable. The displacement of both test bodies proceeded while the load increased, reaching the load limit of 3MN, and the load was terminated.

In the test body after completion of the loading, it was observed that the joint filling concrete 6 near the SC pile collapsed and the SC pile 2 sinked into the joint filling concrete 6. No cracks were observed in the joint-filled concrete 6 other than near the SC pile. Further, the SC pile 2 and the ring socket 4 were sound, and no residual deformation in the radial direction near the bearing members 11 and 12 was observed.
When observing the lower side of the test body, a deviation occurred between the SC pile 2 and the joint filling concrete 6, and no deviation occurred between the ring socket 4 and the joint filling concrete 6.

Here, FIG. 7 shows experimental values of elastic limit proof stress (test body SC-1, test body SC-2) and calculated values obtained by using the above-described evaluation formulas (5) to (8). The result of comparison is shown.
From this figure, the experimental values of elastic limit strength _e P _a and the ratio _e P Calculated _cal P _a by evaluation formula _a / _cal P _a mean 1.11, coefficient of variation (COV) be 0.24 Was confirmed. That is, it is confirmed that the experimental results can be accurately evaluated by the evaluation formulas of the above formulas (5) to (8), and that the application of the evaluation formulas of the above formulas (5) to (8) is appropriate. did it. It was also confirmed that the evaluation formulas of the above formulas (5) to (8) can be evaluated on the safety side.

  Therefore, according to the joint structure 10 of the SC pile and the steel frame column of the present embodiment, due to the compression strut generated between the bearing members 11 and 12 arranged in the SC pile 2 and the ring socket 4, as in the case of the steel pipe pile, Power can be transmitted effectively.

  Further, the elastic limit proof stress can be evaluated with high accuracy by the formulas (5) to (8), and can be evaluated on the safe side even when applied to the SC pile 2.

[(B) Joint test]
Next, the joint test (B) was performed using four test bodies shown in Table 5 and FIG. In addition, for comparison, it was decided to perform an experiment by adding a test body of a joint portion using the steel pipe pile 9.

In addition, all the test bodies are test bodies that model the pile head joints at 1/2 scale, and the parameters of the experiment are the embedded length of the piles 0.75D, 1.25D (D: pile diameter), the axis. Force (compression and tension 0.4N ₀ (N ₀ : axial yield strength of pile steel pipe), three pile types as SC pile 2 and one pile as steel pipe pile 9 (N0.1-No) . 3: SC pile 2, No. 4: Steel pipe pile 9).

◯ −457.2 × 12 (STK490) was used for the ring socket 4 of each test body. A circular steel pipe ◯ -318.5 × 6.9 (STK490) that models the column 3 was arranged at the inner lower end of the ring socket 4, and a non-shrink mortar (premix type) 5 was placed inside. After the non-shrink mortar 7 hardens, a pile (SC pile 2 or steel pipe pile 9) is installed at a predetermined position, and ordinary concrete (24-18-13N) having a nominal strength of 24 N / mm ² is filled in the joint. Filled as concrete 6.

  Further, FB-6 × 6 (SS400) was used as the bearing members 11 and 12, and both side fillet welds were attached to predetermined positions on the outside of the SC pile 2 and the inside of the ring socket 4.

  Table 2 shows the mechanical properties of the steel materials used, and Table 6 shows the compressive strength of the SC pile 2 and the joint filling concrete 6. Tables 2 and 6 also show the ring socket 4 and the SC pile 2.

A method of applying a force to the joint will be described.
FIG. 9 shows the force device used. Further, FIG. 10 shows an application program.

In this experiment, a skewered jack was installed on the upper end of the test body to introduce a predetermined axial force. While the constant axial force was being introduced as it was, the horizontal jack was used to repeatedly apply positive and negative alternating loads.
The deformation angle of the test body was a rotation angle obtained by dividing the displacement of the force application point by the height (h = 1600 mm) from the fixed position under the test body to the force application point. After confirming the elastic behavior by the force of θ = ± 1/800, the force program repeats the force twice each within ± 1/400, ± 1/200, ± 1/100 and ± 1/50. Then, the force was applied in one direction until θ = 1/25, and the process was terminated.

The experimental results will be described below.
(Destructive property)
FIG. 11 shows the relationship between the shearing force Q of the pile and the deformation angle θ. Table 7 shows the experimental values of the yield strength and the maximum yield strength of each test body.

The initial rigidity _e E is the secant rigidity with respect to 1/3 of the maximum proof stress _e Q _u , and the yield strength _e Q _y is the load point (1/3 slope) at which the tangential rigidity of the load deformation relationship is reduced to 1/3 of the initial rigidity. Factor method).

  Specimen No. No. 1 was sound with no damage to the concrete up to θ = 1/200. In the region of θ = 1/200 or less, a hysteresis loop is drawn due to friction, but slip properties due to damage to concrete have not been confirmed. The maximum yield strength was reached at the first positive / negative load of θ = 1/50, and cracking of the concrete on the joint surface proceeded. Since the horizontal load decreased during the loading of θ = 1/25, loading was terminated. Deformation in the radial direction of the steel pipe portion (compression side) at the pile end was observed, and it is considered that the steel pipe pile is locally buckled. Cracking and crushing were observed on the surface of the joint-filled concrete 6 after the application of force.

  Specimen No. No. 2 was healthy with no damage to the concrete up to θ = 1/200. Since the rigidity decreased at the first positive / negative loading of θ = 1/50, and the horizontal load decreased in the middle of θ = 1/25, the loading was terminated. Radial deformation with local buckling of the steel pipe was observed on the compression side of the pile. Some cracks were found in the joint-filled concrete after loading, and a gap between the pile and the concrete was observed. No significant crushing seen in 1 was observed.

  Specimen No. No. 3 was healthy with no damage to the concrete up to θ = 1/200. At the loading of θ = 1/100, the concrete on the joint surface was cracked and slipped out. After that, a force was applied up to θ = 1/50 and 1/25, but a large load reduction did not occur. In the test body after the load was applied, the pile was pulled out by about 30 mm in the vertical direction, but the ability to transmit a horizontal load was retained.

  Specimen No. In No. 4, peeling of the surface concrete occurred at θ = 1/200, but up to θ = 1/200, the concrete was not damaged and was sound. The deformation angle θ = 1/25 was loaded and the loading was completed. Even at this deformation angle, a large load reduction did not occur, and the horizontal load transmission capability was maintained.

  Here, the guideline of the deformation angle of the pile assumed in design is considered to be about 1/200 rad = 0.5%. Therefore, in FIG. 11, the guideline of the deformation angle of the pile assumed in the design is 1/200 rad = 0. A range of 0.5% is shown. From these figures, it can be confirmed that all the test pieces exhibit stable hysteresis characteristics in this range.

Next, the influence of elasto-plastic properties and parameters will be described.
FIG. 12 shows a comparison result of the skeleton curves of the respective test bodies obtained from the relationship between the pile shear force and the deformation angle.
In addition, in the figure, the experimental values of yield strength and maximum proof stress, and the calculated value _p Q _u (N _i ) of the shear force corresponding to the ultimate bending proof strength considering the axial force of each pile are shown. N of N _i means the axial force is taken into consideration, and i means the specimen number.

_In the calculation of _p Q _u (N _i ), the yield point (= 450 N / mm ² ) of the SC pile steel pipe shown in Table 2 and the compressive strength of concrete (= 112.4 N / mm ² ) shown in Table 6 were used. ing. In the figure, the vertical axis and the horizontal axis represent shearing force _p Q _p (N _i ) corresponding to the total plastic bending strength in consideration of the axial force of the steel pipe portion, and its deformation angle θ _p (No. 1 to No. 1). (3: SC pile, No. 4: Calculated by bending rigidity of steel pipe pile) to make dimensionless.

_In the calculation of _p Q _p (N _i ), the yield point (= 450 N / mm ² ) of the SC pile steel pipe and the plastic section modulus Z _p of each steel pipe section shown in Table 2 are used.

Fig. 12 (a) shows a test piece No. with the embedded length of the pile in the ring socket joint as a parameter. 1 and No. 2 shows a comparison of two skeleton curves. In the figure, the calculated values _j Q _u1 and _j Q _u2 of the ultimate proof stress of the ring socket joint portion of each test body obtained based on the above formulas (5) to (8) are also shown.
Specimen No. that failed at the joint The maximum proof stress of No. ₁ is substantially in agreement with _j Q _u1 , and the yield proof stress and the maximum proof stress are both for the test piece No. Less than 2. No. 1 which caused fracture on the bending compression side of SC pile The maximum proof stress of the two test bodies roughly corresponds to _p Q _p (N ₂ ). It was confirmed that although the initial stiffness was similar for both test specimens, the yield strength was a value depending on the embedded length of the pile in the joint.

In Fig. 12 (b), the test body No. using the axial force of the pile as a parameter. 2, No. 3 shows a comparison of 3 skeleton curves.
No. The yield strength of ₃ is almost equal to _p Q _u (N ₃ ), and the maximum yield strength is higher than _p Q _u (N ₃ ). The calculated values using the above formulas (5) to (8) are experimental values. Has been evaluated as safe.
Regarding the initial rigidity, the test body No. No. 2 applied tensile axial force. It was over 3, and it was confirmed that there was an influence of the axial force. It is presumed that the cause is that a frictional force is generated according to the axial force.

In Fig. 12 (c), the test body No. with the type of pile as a parameter is shown. 3 and No. 4 shows a comparison of four skeleton curves.
The initial stiffness of both test pieces is almost the same. Regarding the proof stress, _p Q _p (N _i ) used for dimensionlessization is a shearing force corresponding to the total plastic bending proof stress calculated only for the steel pipe portion, so that the specimen No. Specimen No. 3 is a steel pipe pile. It is larger than 4, and there is a difference due to the presence of the concrete part.

FIG. 13 shows the relationship between the pile deformation angle θ and the pile pull-out amount δ _v in the experiment.
Here, the slip-out amount δ _v of the pile was calculated from the measured displacement shown in FIG. 14. In FIG. 13, the range of ± 1/200 rad is also shown as a standard of the deformation angle assumed in design.

Specimen No. with compressive axial force applied 1, No. 2, the minimum value of δ _v was about −1.5 mm. Specimen No. to which tensile axial force was applied 3, No. 4, in the case of θ = ± 1/200 rad or less, δ _v = about 5 mm, and there are few structural performance problems. In the large deformation region of θ = 1/50 or more, the amount of the pile coming out from the ring socket joint is δ _v = about 20 mm to about 82 mm, which is remarkable, but for δ _v = 52 mm to 80 mm, even after the horizontal load is removed. The amount of slip-out was increased by continuing to load a constant tensile axial force (0.4N _{0 −S} ). This is an experimental result on the safe side, because the tensile axial force does not continue to act on the actual structure.

(Evaluation of yield strength and maximum strength)
Next, the evaluation of yield strength and maximum strength will be described.
The yield strength and maximum strength of the joint of each test body were estimated by the existing strength evaluation formula. Tables 8 and 9 and Fig. 15 show the correspondence between the estimated values of the yield strength and the maximum strength and the experimental values.

Here, the steel pipe and concrete material test results (yield point 460 N / mm ² , compressive strength 112.4 N / mm ² ) shown in Tables 2 and 6 were used to estimate the yield strength of the joint. Similarly, the steel pipe material test results (yield point 450 N / mm ² ) shown in Table 2 were used for estimating the yield strength of the steel pipe pile (test body No. 4). For estimating the yield strength _p Q _y and the maximum strength _p Q _u of the SC pile, the yield point of the SC pile steel pipe and the compressive strength of concrete (tensile strength 450 N / mm ² , compressive strength 112. 4 N / mm ² ) was used.

Specimen No. 1 becomes ultimate state in the destruction of the joint filling concrete _6, it has a _{e Q u / cal Q u =} 1.02, the joint strength by Strength evaluation formula of the above formula (5) to (8) It was confirmed that the evaluation was possible with high accuracy.

Specimen No. 2 becomes ultimate state of bending compression fracture SC piles _2, and has a _{e Q u / cal Q u =} 1.00. The experimental and calculated values correspond well.

Specimen No. In 3, the SC pile 2 was observed to slip out due to the tensile axial force, but the shear force transmission mechanism was retained. _e Q _u / _cal Q _u = a 1.86, also not occur the destruction of SC piles 2 estimated from ultimate strength value. Here, it was confirmed that the SC pile 2 has a proof stress equal to or higher than the calculated value.

Specimen No. In No. 4, the pull-out of the steel pipe pile 9 due to the tensile axial force was observed, but the shear force transmission mechanism is retained. _e Q _u / _cal Q _u = 1.37, that the steel pipe pile 9 has a calculated value or yield strength was confirmed here.

  Therefore, in any of the test bodies, the experimental value shows a good correspondence with the calculated value, and in the joint structure 10 of the SC pile and the steel column of the present embodiment, it can be accurately evaluated by the formulas (5) to (8). .. Moreover, it was confirmed that the experimental value of the ultimate yield strength of the SC pile under the tensile axial force exceeds the calculated value by about 1.8 times, and it can be evaluated on the safety side.

(Evaluation of rotational rigidity of joint)
Next, based on the evaluation of the initial rigidity of each test body obtained in this experiment, the results of examining the rotational rigidity of the joint will be described.

  Here, for each test body, the rigid contact position of the pile was changed from the upper end position of the ring socket to 0 to 1.5D, and the rigidity in which the rigidity was replaced by the rigidity of only the pile was obtained and compared with the initial rigidity of the experimental result. The correspondence is as shown in Table 10.

The test body No. which gave the compressive axial force. 1, No. 2, the initial stiffness _e E in the experimental result is that the value _e E + at the time of the positive force applied first is much larger than the value _e E− at the time of the negative force, which is in the initial state. This is because the influence of friction is particularly remarkable.

Therefore, the specimen No. 1, No. In 2, the initial rigidity _e E was evaluated by the value of _e E−. Specimen No. which gave tensile axial force 3, No. In 4, the values of _e E + and _e E− are almost the same, so the initial stiffness _e E was evaluated by the average value of _e E + and _e E−.

The rigidity when the rigid contact position of the pile was 1.0 D below and the rigidity when it was 1.5 D below was compared with the skeleton curve of each test body. The result is shown in FIG.
From Table 10 and FIG. 16, although the influence of the axial force is recognized on the value of the rotational rigidity, the rotational rigidity of the pile is within the range of θ = ± 1/200 rad which is a guideline of the deformation angle assumed in the design. It was confirmed that it is almost equivalent when the rigid joint position is set to 1.0 D below.

  Although one embodiment of the joint structure of the SC pile and the steel frame column according to the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and can be appropriately changed without departing from the gist thereof. ..

1 Support pile (pile foundation)
1a Upper pile part 1b Middle pile part 1c Lower pile part 2 SC pile 3 Steel column 4 Ring socket 5 Pile head filling concrete 6 Joint filling concrete 7 No shrinkage mortar 8 Level concrete 9 Steel pipe pile 10 SC pile and steel column joining Structure 11 Ring socket side bearing 12 SC pile side bearing 13 Steel column side bearing

Claims (2)

A structure for joining an SC pile forming at least an upper pile portion of a support pile and a steel frame column,
A tubular ring socket provided so as to internally arrange and include the pile head of the SC pile and the lower end of the steel frame column disposed on the pile head,
A ring socket-side pressure-bearing member that is integrally provided on the ring socket and that projects inward from the inner surface of the ring socket;
An SC pile-side pressure member that is integrally provided on the pile head of the SC pile and projects outward from the outer peripheral surface of the pile head;
A steel-pillar-side pressure-bearing member that is integrally provided at the lower end of the steel-column and projects outward from the outer surface of the steel-column,
Filling between the ring socket, the pile head of the SC pile, and the lower end of the steel column to fill the joint between the ring socket, the pile head of the SC pile, and the lower end of the steel column. is constituted by a concrete,
A joint structure of an SC pile and a steel column, wherein elastic limit proof stress is set according to the following formulas (1), (2), (3), and (4).

Here, the total area of _{P a} elastic limit strength _is, I _{F C} 'is Bearing Strength of SC piles (inner steel pipe) side pressure bearing member near the _concrete, I _{A R} is SC piles (inner steel pipe) side pressure bearing member , O _F C _'ring socket Bearing strength (external steel pipe) side pressure bearing member near the concrete, _O a _R is the total area of the ring socket (outer steel pipe) side pressure bearing member, F _C is the joint filling concrete Compressive strength, _I D is the outer diameter of the steel pipe of the SC pile, _I t is the thickness of the steel pipe of the SC pile, _O D is the outer diameter of the ring socket, and _O t is the thickness of the ring socket. In the joint structure of the SC pile and the steel frame column according to claim 1 ,
The ring socket side bearing member and the SC pile side bearing member use bearing members of the same shape,
A joint structure of an SC pile and a steel column, wherein the number of the ring socket side bearing members is larger than the number of the SC pile side bearing members.

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