JP3791478B2 - Pile head joint structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, piles and relates the structure of the pile head joint connecting the steel foundation beams steel post joined.
[0002]
[Prior art]
Conventionally, for pile head joints, it is common to use RC foundation beams and rigidly join the foundation beams and pile heads.
[0003]
For example, in order to join the steel pipe pile and footing joint more than the bending strength of the pile body, reinforcing bars are welded to the outer periphery of the pile and fixed to the foundation beam. Similarly, in the case of cast-in-place piles, the reinforcing bars of the pile body are extended and fixed to the foundation beam.
[0004]
However, the conventional rigid joint causes over-pile arrangement of pile head reinforcing bars, large cross-section of the foundation beam, and the like, leading to an increase in cost.
[0005]
On the other hand, in recent years, a technique for pin-joining or semi-rigidly joining the pile heads is spreading in order to reduce the pile head stress and solve the above problems.
[0006]
For example, Patent Document 1 describes a pile head structure that reduces the pile head moment by making the pile head spherical.
[0007]
In Patent Literature 2, the pile head and the foundation concrete slab are connected to each other through a column having a non-slip bar and having a smaller cross-sectional area than the pile head. Is made smaller than the pile body.
[0008]
In the case of using a steel foundation beam, for example, in Patent Document 3, a pile head is inserted inside a reinforced concrete column or a filled steel pipe concrete column, and the steel foundation beam and the column are welded to the foundation beam via a diaphragm. What is being described is described.
[0009]
[Patent Document 1]
JP 2001-73387 A [Patent Document 2]
Utility Model Registration No. 3058823 [Patent Document 3]
Japanese Patent Laid-Open No. 2001-248167
[Problems to be solved by the invention]
In the case of the invention described in Patent Literature 1, although the pile head has an uneven surface, it is effective in reducing the moment, but the number of man-hours for processing the support portion is large, resulting in a cost increase.
[0011]
The invention described in Patent Document 2 is an invention that targets a foundation concrete slab that is not easily affected by horizontal construction errors of piles as a superstructure, and is provided with a column with a closed cross section at the top of the pile In some cases, it is not possible to place a stiffening bar inside the column due to construction errors in the horizontal direction of the pile.
[0012]
The invention of Patent Document 3 is intended to insert the pile head inside the filled tubular concrete column, since the gap of the pillars and their inner pile is small, error absorption in the horizontal direction of the pile due to the pouring Is difficult, and is also disadvantageous in terms of simplifying the pile head joint.
[0013]
The present invention has been made to solve the problems in the prior art as described above, and aims to provide a pile head joint structure that is inexpensive, can easily absorb construction errors, and can reduce the pile head bending moment. It is what.
[0014]
[Means for Solving the Problems]
Pile joint structure according to a first aspect of the present invention, the pile at least at the junction of the steel columns concrete filled in the steel shell of column base, bonding steel foundation beam to column base of the column And a rod-shaped hardware extending in the axial direction of the pile and the column is arranged in the center portion of the concrete section constituting the pile head portion of the pile and the concrete constituting the column base portion of the column , The joining portion is configured to be in a semi-rigid joining state .
[0015]
When a bending moment exceeding a specified level is applied, the pile head joint becomes semi-fixed due to the removal of the rod-shaped hardware placed over the pile head and column base, reducing the bending moment of the pile head. The pile head joint can be made an inexpensive and simple structure.
[0016]
Moreover, due to the use of steel foundation beams, as compared with the case of the RC footing beams, are reduced bending moment of pile head is improved more effectively.
[0017]
In addition, since it has a structure in which a rod-shaped hardware is arranged in the center of the cross section of the pile, it is possible to install the rod-shaped hardware in the column even for a certain amount of construction error of the pile, and it is easy to absorb the construction error in the horizontal direction. is there.
[0018]
In addition, the structure of the present invention that reflects the joint deformation positively in the design can be said to be a semi-rigid joint structure compared to the conventional case where the pile head is considered as a rigid joint and the deformation of the pile head joint is not considered in the design. .
[0019]
In addition to round bars such as steel bars and deformed bars, rods, square bars, polygonal bars with a cross section perpendicular to the longitudinal direction, round steel pipes, square steel pipes, very thick reinforcing bars, cross-shaped cross sections, cross H There is no particular limitation as long as it has a cross section and rigidity sufficient to bear the shearing force at the joint, such as a cross-sectional material. Further, the bar-shaped hardware is not limited to one, but may be a rebar rod or a bundle of a plurality of bars.
[0020]
The bar-shaped hardware is sized so that it can be installed in the pillar even if the construction error of the pile is taken into account. When installing a plurality of bar-shaped hardware, considering the overall diameter, the inner diameter of the pillar, and the construction error of the pile, the number of bar-shaped hardware to be bundled and the specifications such as the reinforcing bar can be determined. . When providing a base plate (described later) at the lower end of the column, it is necessary to consider the size of the through hole of the base plate instead of the inner diameter of the column.
[0021]
The rod-shaped hardware can be provided with means for increasing the adhesive force between the fixing force or concrete for concrete.
[0022]
Tensile force is generated in the rod-shaped hardware, but by providing means for increasing the fixing force to the concrete or the adhesion force with the concrete, it is possible to effectively prevent the rod-shaped hardware from coming out.
[0023]
As a means for increasing the fixing power to concrete, for example, a fixing plate attached to both ends or an intermediate portion of a rod-shaped hardware, which can obtain a large supporting pressure to concrete, means for increasing the adhesion to concrete Examples include studs, joints (including deformed steel bar joints), protrusions, holes, etc. provided on the outer periphery of the shaft part of a rod-shaped hardware, but it is necessary to clearly distinguish both functions of fixing force and adhesion force. There is no.
[0024]
Te pile joint structure odor of the present invention, piles may be at least the pile head and the concrete is filled structure in the steel shell.
[0025]
The piles to which the present invention is applied include on-site RC piles, steel pipe piles, and various other prefabricated piles, but since rod-shaped hardware must be embedded in concrete, for example, at least piles in the case of steel pipe piles The head is filled with concrete so that, for example, the lower half of the rod-shaped hardware is embedded in the concrete of the pile head.
[0026]
In this case, steel pipe piles as steel shells or steel pipes of SC piles, or steel pipes provided only on pile heads such as RC piles, RC piles as existing piles, PC piles, etc., restrain the concrete inside. Therefore, an increase in the fixing force or adhesion force of the rod-shaped hardware can be expected.
[0027]
Te pile joint structure odor of the present invention, the steel pillars, that have been at least column base concrete is filled into the steel shell structure.
[0028]
For steel post as an application subject of the present invention, the steel pipe column, although concrete filled steel tube column pillar of any type of construction contemplated, as with pile side, the rod-shaped fittings must be embedded in the concrete, for example, filled with concrete at least in the column base portion in the case of tubular columns, for example, about half the length of the portion of the top of the rod-shaped fittings are you to be embedded in the concrete of the columnar leg portion.
[0029]
Pillars and piles between axial force transmission is dispersed of smoothly purposes pillar lower end made of steel sheet or the like to the base plate is provided that if a performed at, the center of the base plate, provided with a through-hole rod-shaped fittings penetrates It is done.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a pile head joint structure of the present invention.
[0031]
In this embodiment, the superstructure is a steel structure, the column 2 is a square steel pipe column, the foundation beam 3 is an H-shaped steel beam, and the pile 1 is a cast-in-place RC pile.
[0032]
In the illustrated example, the steel base beam 3 and the column 2 are welded and joined, and the joined portion has a non-diaphragm type. A perforated base plate 4 is provided at the lower part of the pillar 2, and a metal round bar as a rod-shaped metal object 5 penetrates the hole 4 a from the pile 1 to the inside of the pillar 2.
[0033]
The lower part of the bar-shaped hardware 5 is buried in the concrete of the pile 1, and concrete 7 is placed in the vicinity of the joint portion of the pillar 2 with the foundation beam 3, and the upper part of the bar-shaped hardware 5 is placed in the concrete 7. Buried. A large number of studs 6 are welded to the rod-shaped hardware 5 over substantially the entire length located at the joint surface between the pile 1 and the column 2.
[0034]
In the present invention, the cross section of the pillar 2 may be circular, square, polygonal, etc., and is not limited to that shown in FIG. Further, the cross section of the foundation beam 3 may be a square, a circle, a double web H or the like in addition to the H shape of FIG.
[0035]
When the column 2 and the foundation beam 3 are joined by welding, any of a non-diaphragm type, an outer diaphragm type, an inner diaphragm type, and a through diaphragm type may be used. Moreover, in the case of bolt joining, it can join via joining hardware, such as a split tee, an angle, an end plate, and a channel steel.
[0036]
2 (a) to 2 (h) show modified examples of the rod-shaped hardware. FIG. 2 (a) shows a round bar 5a (round steel), and FIG. 2 (b) shows a polygonal bar 5b (square steel). 2), FIG. 2 (c) shows a case of a small diameter steel pipe 5c, FIG. 2 (d) shows a case of a small diameter square steel pipe 5d, FIG. 2 (e) shows a case of a cross-shaped cross section 5e, FIG. Is the case of the cross H-shaped cross-section material 5f. In addition, a plurality of reinforcing bars 5g as shown in FIG. 2 (g), or a plurality of bars, round bars, polygonal bars, etc., which are bundled densely with some gaps, or a reinforcing bar 5h as shown in FIG. 2 (h) May be used.
[0037]
3 (a) to 3 (c) show means for increasing the fixing force or adhesion of the rod-shaped hardware. FIG. 3 (a) shows a fixing plate 11 at both ends of the round bar as the rod-shaped hardware 5. FIG. 3 (b) shows a case where a round bar as a bar-shaped metal object 5 is provided with a node 12 such as a screw node, and FIG. 3 (c) shows a cross-shaped cross-section material (a cross H-shaped cross section as a bar-shaped metal object 5). In some cases, striped protrusions 13 (left side in the figure) or holes 14 (right side in the figure) are formed at both ends of the material.
[0038]
FIGS. 4 (a) and 4 (b) show the deformation modes related to the adhesion between the steel pipe constituting the column 2 and the concrete 7 filled therein, and FIG. 4 (a) shows the foundation of the steel tube column 2. When the inner diaphragm 21 provided on the inner surface of the height to which the beam 3 is attached is used for enhancing the adhesion force with the concrete 7, FIG. 4 (b) forms a number of protrusions 22 inside the steel pipe of the column 2, This is intended to increase the adhesion between the steel pipe of the column 2 and the concrete 7.
[0039]
FIG. 5 shows a modification of the embodiment of FIG. 1, in which the base plate 4 of the pillar 2 is embedded in the head of the pile 1. FIG. 6 shows an embodiment in which the pillar 2 has no base plate. 7, the foundation beam 3 as a comparative example is a case of RC structures.
[0040]
FIGS. 8 (a) and 8 (b) each show an example of the structure of a pile head in a specific embodiment of the present invention. FIG. 8 (a) shows the pile head outer periphery of the cast-in-place RC pile 31a. In the case of the earthquake-resistant cast-in-place pile 31 reinforced by winding the steel pipe provided by the steel pipe 31b, FIG. 8 (b) shows the case where the concrete 8 is filled in the head of the steel pipe pile 41. FIG.
[0041]
Below, the dimension example of a junction part at the time of examining the dimension shape of the pile head junction part by this invention is demonstrated about the pile head of a 10-story steel-frame building.
[0042]
The pile head joint is assumed to have the dimensional shape shown in FIG. The foundation beam is assumed to be a steel beam. The basic beam (assuming H-shaped steel with a width of 300 mm and a height of 700 mm) and a column (cold press-formed square steel pipe, assuming that the column base has an outer diameter of 600 mm and a plate thickness of 38 mm) are sufficient. It is assumed that Go is made. The round bar as the rod-shaped hardware is assumed to be a deformed reinforcing bar (SR235) having a diameter of 100 mm.
[0043]
As shown in Fig. 10, the pile head moment / rotation angle is infinitely rigid until the proof stress M _cr when the compressive stress of the outermost edge concrete part is 0, and after that, the metal round bar in the center is It is assumed that rotation is caused by pulling out.
[0044]
Rotational stiffness after the M _cr is determined and the tensile at yield strength M _y of round bar of the central portion than the rotation angle θ _y. M _y is calculated base plate as an RC section. θ _y is a value obtained by integrating the axial strain distribution in the material axis direction of the round bar when yielding the round bar shown in FIG. 11 and dividing the deformation of the protruding portion by the distance x _n to the neutral axis of the cross section.
[0045]
FIG. 12 shows the relationship between the pile head moment M calculated in this way and the rotation angle. In the figure, the case where the horizontal construction error e is 100 mm is also shown.
[0046]
As shown in FIG. 13, the analysis model is calculated with the upper and lower parts integrated, assuming an infinite uniform frame. The rotation deformation of the pile head is evaluated by providing a rotation spring on the pile head.
[0047]
The ground conditions are a clay layer with N value = 5 from GL to −12 m, a fine sand layer with N value = 20 from −12 m to −16 m, and a gravel layer with N value = 50 from the depth.
[0048]
Apply horizontal force during an earthquake (short term) to such a model. In this case, the shear force applied to the pile head is 7.03 × 10 ⁵ N.
[0049]
FIG. 14 shows a pile moment distribution at the time of earthquake (short term) as a result of using the analysis model. Compared with the case where the pile head is rigidly connected, the pile head moment when the pile head is semi-rigidly connected is reduced to about 60%.
[0050]
FIG. 15 shows the results when the foundation beam is RC as a comparative example . Compared to the case where the pile head is rigidly connected, the pile head moment when the pile head is semi-rigidly connected is reduced to about 20%.
[0051]
FIG. 16 shows the relationship between the short-term allowable axial force N and the bending moment M of the pile head. The generated moment is within the short-term tolerance regardless of whether the steel foundation beam or the RC foundation beam, and there is no structural problem. I understand that.
[0052]
At this time, the axial stress generated in the round bar is 7.64 × 10 ³ N / cm ² . Assuming that the round bar bears all the pile head shear force, the shear stress generated in the round bar is: pile head shear force / round bar cross-sectional area = (7.03 × 10 ⁵ N) / (78.5 cm ² ) = It becomes 8.92 × 10 ³ N / cm ² .
[0053]
Consider the following as yield conditions for round bars.
(Κ · τ _mean / τ _y ) ² + (σ / σ _y ) ²
here,
κ: Shape factor (since it is circular, 1.3)
τ _mean : Average shear stress τ _y : Yield shear stress (= σ _y / √3)
σ: axial stress σ _y : yield stress (2.35 × 10 ⁴ )
Substituting the specifications into the above equation gives the following, and the round bar does not yield even if it bears axial and shear forces.
[0054]
(Κ · τ _mean / τ _y ) ² + (σ / σ _y ) ² = 0.83 <1.0
Considering that there is no round bar and that the shear force is borne only by the concrete part inside the column, it is assumed that concrete F _c = 2.35 × 10 ³ N / cm ² and the short-term allowable shear force is 2.94 × 10 ^5. It is clear that there is only about half of the required value 7.03 × 10 ³ N / cm ² , and it is obvious that it is difficult to bear with only the shear resistance of the concrete part.
[0055]
Thus, in the present gun invention can reduce the pile head moment, there is sufficient resistance to moment and shear forces.
[0056]
Next, consider the case where horizontal construction errors occur.
[0057]
FIGS. 17 and 18 are pile moment distributions when the relationship between the pile head moment M and the rotation angle in FIG. 12 is used. The foundation beam is considered both steel and RC as a comparative example .
[0058]
Compared to the case of e = 0, the rotational rigidity of the pile head increases, but in the case of the steel foundation beam, the increase in the pile head moment is hardly observed, and in the case of the RC foundation beam, when e = 0. about 20% moment than is you increase.
[0059]
FIG. 19 shows the relationship between the short-term allowable axial force N and bending moment M of the pile head in consideration of the construction error. Regardless of the construction type of the foundation beam, even within a construction error of 100 mm, it is within the short-term tolerance. It can be seen that there is no structural problem even if a horizontal error occurs.
[0060]
【The invention's effect】
In the present invention, the rod-shaped hardware placed in the concrete in the center of the pile and the column base bears a shearing force, and when a bending moment exceeding a predetermined level is applied, the semi-rigid connection is caused by the axial strain of the rod-shaped hardware. Since the bending moment of the pile head joint can be reduced by the shape, the pile head joint can be made an inexpensive and simple structure.
[0061]
In addition, because it has a structure in which a rod-shaped hardware is placed in the center of the cross section of the pile, it is possible to install a column even for a certain degree of construction error, it is easy to absorb horizontal construction error, and the pile head joint There is little influence on the function due to construction errors.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view showing an embodiment of a pile head joint structure of the present invention.
2 (a) to (h) are cross-sectional views perpendicular to the axial direction, each showing a variation of a rod-shaped hardware relative to the embodiment of FIG.
FIGS. 3A to 3C are vertical sectional views showing means for increasing the fixing force or adhesion force of the rod-shaped hardware.
FIGS. 4A and 4B are vertical sectional views showing deformation modes related to adhesion between a steel pipe constituting a column and concrete, respectively.
FIG. 5 is a vertical cross-sectional view showing an embodiment in which a column base plate is embedded in a pile head with respect to the embodiment of FIG. 1;
FIG. 6 is a vertical cross-sectional view showing an embodiment in the case where there is no base plate in the column, compared to the embodiment of FIG.
[7] footing beams as a comparative example relative to the embodiment of FIG. 1 is a vertical sectional view showing a case of RC structures.
FIGS. 8A and 8B are vertical cross-sectional views showing other embodiments of the present invention, respectively.
FIG. 9 shows a design model for explaining a pile head joint structure of the present invention, in which (a) is a vertical sectional view and (b) is a horizontal sectional view.
FIG. 10 is a graph for explaining a relationship between a moment of a pile head and a rotation angle in a design model.
FIG. 11 is a diagram for explaining a relationship between a bending moment and an axial force, a rotation angle, and a strain in an axial direction of a rod-shaped metal object in a design model.
FIG. 12 is a graph showing the relationship between the calculated pile head moment M and the rotation angle.
FIG. 13 is an explanatory diagram of an analysis model assuming an infinite uniform frame.
14 is a graph showing a pile moment distribution during an earthquake (short term) when the analysis model of FIG. 13 is used.
FIG. 15 is a graph showing a pile moment distribution at the time of an earthquake (short-term) when a foundation beam is an RC structure as a comparative example .
FIG. 16 is a graph showing the relationship between the short-term allowable axial force N and the bending moment M of the pile head.
FIG. 17 is a graph showing a comparison of pile moment distribution when the horizontal construction error e is 0 (solid line) and 100 mm (dotted line) when the foundation beam is a steel beam.
FIG. 18 is a graph showing a comparison of pile moment distributions when the horizontal construction error e is 0 (solid line) and 100 mm (dotted line) when the foundation beam has an RC structure as a comparative example . .
FIG. 19A is a graph showing a relationship between a short-term allowable axial force N of a pile head and a bending moment in consideration of a construction error, and FIG. 19B is an explanatory diagram of the construction error in the examination.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Pile, 2 ... Column, 3 ... Foundation beam, 4 ... Base plate, 4a ... Hole, 5 ... Bar-shaped metal, 6 ... Stud, 7 ... Concrete, 8 ... Concrete,
11 ... fixing plate, 12 ... node, 13 ... striped protrusion, 14 ... hole,
21 ... Inner diaphragm, 22 ... Protrusions,
31 ... Earthquake-resistant cast-in-place pile, 31a ... RC pile, 31b ... Steel pipe,
41 ... Steel pipe pile,
w ... Welding point

Claims (1)

In the joint between the pile and the steel column filled with concrete in the steel shell of at least the column base, a steel foundation beam is bonded to the column base of the column and constitutes the pile head of the pile A rod-shaped hardware extending in the axial direction of the pile and the column is arranged in the concrete constituting the center of the concrete section and the column base of the column, and the pile head joint is configured to be in a semi-rigid joint state. Pile head joint structure characterized by that.

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