JPH1025745A - Anchoring structure of steel column base - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anchoring structure for a steel column pedestal in which the embedding depth of an anchor bolt is small, the degree of fixation of the steel column pedestal and the design of the rise of the foundation are improved, and the construction is easy. SOLUTION: A steel column base formed by integrally joining a column base hardware to a lower end portion of a steel column is embedded in a foundation concrete, and an anchor bolt formed into a U-shape when projected onto a vertical plane and the anchor bolt. In the anchoring structure of the steel column base fixed on the foundation concrete via the nut screwed to the upper end of the anchor bolt, the anchor bolt is formed of deformed steel bar, and the connecting portion between the upright portion of the anchor bolt and the horizontal portion is formed. And an inner radius (1.5 to 5) D (mm) (D is the name of a deformed steel bar).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing structure of a steel column base for fixing a steel column base constituting a building on foundation concrete.

[0002]

2. Description of the Related Art FIG. 5 is a longitudinal sectional view of an essential part showing an example of a conventional fixing structure for a steel column base. In FIG. 5, reference numeral 1 denotes a support, which is erected at an appropriate interval on a discarded concrete 3 provided on a split chestnut 2, and a support member 4 is horizontally fixed to an upper end of the support 1. . Next, reference numeral 5 denotes an anchor bolt, which is formed of a steel bar, and has screws (not shown) at upper and lower ends.

The anchor bolt 5 engages a nut 6 and a fixing plate 7 to be positioned and fixed to the support member 4.
The base concrete 9 is cast with the hollow cylindrical sleeve 8 inserted. After the foundation concrete 9 is cured and set, the steel column base 13 formed by joining the column base metal 11 to the lower end of the steel column 12 via the central mortar 10 is placed,
After positioning, the non-shrink mortar 14 is filled between the column base hardware 11 and the foundation concrete 9.

A washer 1 is provided at the upper end of the anchor bolt 5.
The steel column base 13 is fixed on the foundation concrete 9 by mounting the nut 5 and the nut 16 and tightening the nut 16. It is to be noted that reinforcing steel bars are usually provided in the foundation concrete 9, but are not shown in FIG.

[0005]

FIG. 6 is an explanatory view showing a state of an external force acting on the anchoring structure of a conventional steel column base.
The same parts are indicated by the same reference numerals as in FIG. In FIG. 6, when a bending moment MH acts on the steel column base 13, a tensile force QF acts on one of the anchor bolts 5. That is, since the sleeve 8 is inserted into the anchor bolt 5, the anchor bolt 5 is not restrained from the foundation concrete 9, and the tensile force QF acts to peel off the fixing plate 7.

The tensile force QF acts as a result to cause the foundation concrete 9 to break in a cone shape as shown by a broken line. Therefore, in order to counter this, the embedding depth H of the anchor bolt 5 is increased. In general, when the diameter of the shaft portion of the anchor bolt 5 is d, H ≧ 20d. In this case, as the strength of the foundation concrete 9 is lower, the embedding depth H is further increased, and the length of the anchor bolt 5 is also increased.

For this reason, there is a problem that the extension of the anchor bolt 5 becomes large and the degree of fixation of the steel column base 13 decreases. Even if the sleeve 8 is omitted in order to suppress the elongation of the anchor bolt 5 and the adhesion of the anchor bolt 5 to the foundation concrete 9 is to be increased, the anchor bolt 5 is usually formed of round steel and has a smooth surface. Therefore, the adhesive force is unstable. In addition, since the adhesion between the two is broken down with time from the upper end of the anchor bolt 5 and proceeds downward, it is difficult to set the above-mentioned adhesion at the time of design. For this reason, the anchor bolts 5 must be kept in a state of being unrestricted by the sleeve 8 with respect to the foundation concrete 9, and the above-mentioned problems are included.

[0008] In addition to the above problems, the basic concrete 9
Since the size of the rising portion of the base is large, the number of reinforcing bars to be provided in this portion is inevitably increased, and not only the design but also the production of the foundation concrete 9 becomes complicated, and the anchor bolt 5 In addition, the work of positioning and fixing the fixing plate 7 is also complicated, resulting in problems such as an increase in manufacturing cost and an increase in construction period.

In order to solve the above problems, there has been proposed a fixing structure for a steel column base using a U-shaped anchor bolt formed by a threaded bar (for example, Japanese Patent Application Laid-Open No. 7-197600). reference). According to this proposal, the U-shaped anchor bolt can fix the steel column base by the adhesive force between the upright portion and the foundation concrete and the resistance of the bent portion of the foundation concrete. It is stated that the embedding depth can be reduced, the degree of fixation of the steel column base and the design of the rising portion of the foundation are improved, and the effect of simplifying the construction of the anchoring portion is also described.

However, even in the above-mentioned anchoring structure for steel column bases, there is a slight problem that no technique has been established yet, and specific and quantitative guidelines for application to on-site work are not always clear. There is a point.

An object of the present invention is to solve the above problems, clarify concrete and quantitative technical matters, and provide a higher-performance anchoring structure for a steel column base which can be easily applied to field work. And

[0012]

In order to solve the above-mentioned problems, in the present invention, a steel column base formed by integrally joining a column base metal to the lower end of a steel column is embedded in a foundation concrete. In an anchoring structure of a steel column base anchored on a foundation concrete via an anchor bolt formed into a U-shape projected on a vertical plane and a nut screwed to an upper end of the anchor bolt, the anchor bolt is deformed. In addition to the steel bar, the connecting portion between the upright portion and the horizontal portion of the anchor bolt is formed in an arc shape with an inner radius (1.5 to 5) D (mm) (D is the name of a deformed bar). Means were adopted.

[0013] By forming the connecting portion in an arc shape as described above, the pull-out resistance due to an increase in the projected area of the connecting portion on the horizontal plane with respect to the tensile force in the vertical direction of the anchor bolt is improved. Therefore, even if the upright portion has a shortage of adhesion with the foundation concrete, it is possible to sufficiently secure the anchoring force.

In the present invention, if the inward radius of the arc-shaped connection portion is less than 1.5 D (mm), the projected area of the connection portion on the horizontal plane is small, so that improvement in pull-out resistance cannot be expected. In addition, stress concentration may occur at the connection portion, which may cause undesired damage, and the U-shaped shaping operation may be complicated, which is not preferable. On the other hand, if the inward radius of the arc-shaped connecting portion exceeds 5 D (mm), the projected area of the connecting portion on the horizontal plane increases, but the degree of improvement in pull-out resistance is small, which is not preferable. That is, the share of the tensile force in the vertical direction in the connection portion is maximum near the upright portion, and is smaller as it is smaller in the horizontal portion.

Next, as the deformed steel bar forming the anchor bolt in the present invention, a reinforcing steel bar called a threaded joint, a bamboo joint, and a crossed joint can be used. Of these, the use of a threaded bar is preferred because the nut can be screwed directly to the upper end.

Further, in the above invention, it is preferable that the horizontal portions of the anchor bolts intersect in a projected state on a plane. By forming in this way, when a bending moment acts on the steel column base, a tensile force can be applied to only one upright portion of the U-shaped anchor bolt, and the other upright portion can have a tensile force. By applying a compressive force, the anchor bolt can be stabilized.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are a vertical sectional view and a plan view, respectively, showing a main part of an embodiment of the present invention. Indicated by In FIGS. 1 and 2, reference numeral 17 denotes an anchor bolt, for example, an SD490 deformed steel bar (threaded steel bar) for projecting a projected shape onto a vertical plane to an upright portion 17a and a connecting portion 17a.
b and a horizontal portion 17c, and is buried in the foundation concrete 9. The embedding depth H is
For example, it is 16 Dmm (D is the name of the deformed steel bar).

Next, the column base metal 11 is formed, for example, in a square shape with a projected contour shape to a plane, and is integrally joined to the lower end of a steel column 12 made of, for example, a square steel pipe by welding to form a steel column base 13. I do. The column base metal 11 is preferably formed of cast steel or forged steel, but may be formed of a thick steel plate.

For example, bolt holes (not shown) are provided at, for example, the corners of the column base hardware 11. The upper ends of the anchor bolts 17 are inserted through these bolt holes, and The column base metal 11 is fastened and fixed.
In this case, it is preferable that the anchor bolts 17 are arranged such that their horizontal portions 17c intersect in a projected state on a plane as shown in FIG.

With the above configuration, when a bending moment MH acts on the steel column base 13 as shown in FIG. 1, for example, a tensile force QF acts on the left side of the U-shaped anchor bolt 17. In this case, since the anchor bolt 17 is formed in a U-shape by the threaded rebar, the tensile force QF is opposed by the adhesive force at the upright portion 17a and the resistance of the foundation concrete 9 at the connecting portion 17b and the horizontal portion 17c. Then, the steel column base 13 can be fixed.

Therefore, in contrast to the prior art shown in FIGS. 5 and 6 where the embedding depth H required 20 Dmm or more, the embedding depth H shown in FIG.
Can be set to, for example, 16 Dmm, and the rising portion of the foundation concrete 9 can be greatly reduced.

In the present invention, the steel column base 1
The rotational rigidity of No. 3 can also be greatly improved. That is, FIG.
In the prior art shown in (1), since the anchor bolt 5 is formed in an unrestricted state over substantially the entire length of the foundation concrete 9 by the sleeve 8, the amount of elongation due to the action of the tensile force QF is large. On the other hand, in the case of the present invention, since the anchor bolts 17 are formed almost completely in the constrained state by the foundation concrete 9, even if the adhesion and peeling occur near the upper end face of the foundation concrete 9, for example, Is small, the amount of elongation due to the action of the tensile force QF remains at a small value.

FIG. 3 is an enlarged longitudinal sectional view of a main part showing the vicinity of the upper end of the anchor bolt 17 in FIG. 1, and the same parts are denoted by the same reference numerals as in FIGS. 1 and 2. In FIG. 3, reference numeral 21 denotes a bolt hole, which has an inner diameter slightly larger than that of a normal case in consideration of the fact that the U-shaped anchor bolt 17 deforms with time in the direction perpendicular to the axis after molding. Alternatively, it is preferable to form an elongated hole along a plane including the axis of the anchor bolt 17.

As shown in FIG. 3, when the base concrete 9 is cast and filled with the non-shrink mortar 14,
The anchor bolt 17 is restrained in the axial direction by the threaded portion formed on the outer peripheral portion of the anchor bolt 17, and has a large adhesive force between the foundation concrete 9 and the non-shrink mortar 14.

The gap between the anchor bolt 17 and the bolt hole 21 is filled into the column base metal 11 through a grout injection hole (not shown) with grout so that the anchor bolt 17 and the column base metal 11 are connected to each other. Can be integrated,
The horizontal load QH acting on the column base metal 11 can be counteracted, and the degree of fixation of the steel column base 13 (see FIGS. 1 and 2) can be further improved.

FIG. 4 is an explanatory view showing the state of the load and the stress acting on the anchor bolt in the embodiment of the present invention, and the same parts are indicated by the same reference numerals as in FIGS. 1 and 2. In FIG. 4, QR is a stress at the connection portion 17b, and this stress QR differs depending on the location of the connection portion 17b. That is, the vicinity of the upright portion 17a is the largest, and becomes smaller as approaching the horizontal portion 17c.
It is almost 0 near 7c. Therefore, it is considered that 1/2 to 2/3 of the connecting portion 17b on the side of the upright portion 17a contributes to improvement of the pull-out resistance.

The state of the stress distribution or load distribution at the connecting portion 17b and the anchor bolt 1
7, the inner radius R of the connection portion 17b is taken into consideration.
Is the designation D of the deformed steel bar forming the anchor bolt 17.
It is preferable that R = (1.5 to 5) D (mm).

In the embodiment of the present invention described above, an example in which the anchor bolt 17 is formed by a threaded bar is described. Alternatively, a bamboo bar or a barbed bar may be used as the deformed bar. However, when these deformed steel bars are used, a screw member is integrally joined to the open end of the U-shape by joining means such as friction welding, for example, so that the screw member can be screwed with the nut.

The present invention can be applied not only to square steel pipes but also to round steel pipes, polygonal steel pipes, and H-shaped steel pipes as steel columns. Naturally, it can be applied to anything that does.

[0030]

Since the present invention has the above-described configuration and operation, the following effects can be obtained.

(1) In the case of using a U-shaped anchor bolt, specific and quantitative technical matters are established, and a higher-performance anchoring structure for a steel column base can be obtained. (2) Compared to the conventional type using upright anchor bolts, the embedding depth can be greatly reduced and the proof stress can be reduced.
It can be improved by more than 1.5 times.

(3) The pitch of the anchor bolts in the horizontal direction can be reduced, and the area occupied by the column base hardware can be reduced. (4) The degree of fixation of the steel column base and the design of the rising portion of the foundation can be improved, and the construction of the anchoring portion can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional plan view of a main part showing an embodiment of the present invention.

FIG. 3 is an enlarged longitudinal sectional view of a main part showing the vicinity of an upper end of an anchor bolt 17 in FIG. 1;

FIG. 4 is an explanatory diagram showing a state of a load and a stress acting on the anchor bolt in the embodiment of the present invention.

FIG. 5 is a vertical sectional view of a main part showing an example of a conventional fixing structure for a steel column base.

FIG. 6 is an explanatory view showing a state of an external force acting on a fixing structure of a conventional steel column base.

[Explanation of symbols]

 11 Column base hardware 12 Steel column 17 Anchor bolt 17a Upright part 17b Connection part 17c Horizontal part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Hirakawa 1-9-1 Kitahama-ku, Wakamatsu-ku, Kitakyushu-shi, Fukuoka Hitachi Metals Co., Ltd. No. 2 Inside Hitachi Koki Co., Ltd. (72) Kazuyuki Noguchi Inventor Kazuyuki No. 2-4-2 Toyo, Koto-ku, Tokyo Inside Hitachi Koki Co., Ltd. (72) Kuniaki Sato 24-21 Yaesaki-cho, Hiratsuka-shi, Kanagawa Prefecture

Claims (3)

[Claims] 1. An anchor bolt having a steel column base formed by integrally joining a column base metal to the lower end of a steel column, embedded in base concrete, and having a U-shaped projected shape projected onto a vertical plane. In a fixing structure for a steel column base fixed on a foundation concrete via a nut screwed to an upper end of the bolt, the anchor bolt is formed of a deformed steel bar, and a connecting portion between an upright portion and a horizontal portion of the anchor bolt. Is formed in the shape of an arc having an inner radius (1.5 to 5) D (mm) (D is the name of a deformed steel bar). 2. The anchoring structure for a steel column base according to claim 1, wherein the deformed steel bar is a threaded bar. 3. The anchor bolt according to claim 1, wherein a horizontal portion of the anchor bolt intersects in a projected state with a plane.
The anchoring structure of the steel column base described.