JP2000297480A - Reinforcing method for steel-pipe structure column base section - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the reinforcing method for a steel-pipe structure column base section, by which the mutual fitting conditions of members for a column base section are improved, the column base section can also be constructed easily and tensile strength can be increased. SOLUTION: In this reinforcing method for the steel-pipe structure column base section in which a steel-pipe column 1 and a base plate 2 integrally installed at the leg section of the steel-pipe column 1 are fixed onto foundation concrete 5 by using anchor bolts 3 buried into foundation concrete 5, one end side of a reinforcing bar 6c is buried into foundation concrete 5, an opening 7c larger than the diameter of the reinforcing bar by 10-20 mm is formed to the base plate 2 in the steel-pipe column 1, the other end side of the reinforcing bar 6c is inserted and arranged into the opening 7c, and concrete 8 is placed into the steel-pipe column 1 up to height in which the other end side of the reinforcing bar 6c is buried sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reinforcing a column-base portion of a steel pipe structure for reinforcing and arranging a column-base portion of a steel pipe structure.

[0002]

2. Description of the Related Art A column base of a steel pipe structure is a part for transmitting the force received by a steel pipe column to basic concrete, and a column base part is a part for fixing a steel pipe material to reinforced concrete (base concrete). In addition, the form of the column base includes an exposed form, a root-wound form, and the like.

The column base shown in the elevation view of FIG. 5 is of a conventional exposed type. In FIG. 5, the column base material is obtained by assembling a steel pipe column 20 and a base plate 21 by welding.
The column base members 20 and 21 are fixed by anchoring with anchor bolts 3 previously embedded in the foundation concrete 5. In the column base, a part of the steel pipe column 20 is cut out in order to keep the column base members 20 and 21 small (FIG. 6).
, The anchor bolts 30 are arranged in the steel pipe column 1. Anchor bolt 30 having a diameter of 16 to 32 is used, and the embedding length is 30 times or more the bolt diameter (40 mm when a tensile force is generated).
More than twice). The anchor bolt 30 is attached to the base plate 21 as shown in the plan sectional view of FIG.
It is buried by being equally allocated to about this book. In the case of the exposure type, the nuts 4 and 4 are detented to make them double.

[0004] In addition, in the case of the root winding method, after joining like the exposed method, concrete is cast and the lower part of the column is wrapped, and the root winding method is a stronger bonding method than the exposed method.

Meanwhile, in the Great Hanshin-Awaji Earthquake (Hyogoken-Nanbu Earthquake), there were cases where a large number of conventional steel column bases shown in FIG. 5 were destroyed. According to a survey of steel column bases damaged by the Hyogoken-Nanbu Earthquake, it is said that the damage to the column bases is mainly due to repeated large tensile and compressive forces during the earthquake. In other words, a large tensile force is applied during an earthquake, and the anchor bolts on the column bases are pulled down to cause plastic elongation, which is followed by a large compressive force. It is considered that when the tensile force and the compressive force are repeatedly generated in a short time, the anchor bolt buckles or breaks, and as a result, the column base is destroyed.

Therefore, in order to increase the fixing strength of the column base to the foundation concrete, a method of reinforcing the column base to increase the tensile strength of the column base has been proposed. For example, in the case of the exposure type, since the tensile strength is determined by the cross-sectional area of the screw portion of the anchor bolt, as shown in FIG. 7, the number of the anchor bolts 30 is increased (the cross-sectional area of the screw portion is increased).
This increases the tensile strength. In FIG. 7, as shown in the plan sectional view of FIG.
The number has been increased to six.

[0007]

However, when an anchor bolt is added to reinforce the steel pipe structure column base, the following problems occur.

That is, in order to accommodate the column base material in the column base part, a part of the steel pipe column 1 may be cut out (see FIG. 5), and the anchor bolt 30 may be arranged in the steel pipe column 20. In this case, if the anchor bolts 30 are increased (the number of notches is increased), the strength of the steel pipe column 20 is reduced, and the steel pipe structural column base cannot be reinforced. Further, when the number of anchor bolts 30 is increased without providing the notch in the steel pipe column 20, as shown in FIG.
3 became large, and there was a problem that fitting of a pillar base part became bad. When the anchor bolts 30 are arranged outside the steel pipe columns 22 as shown in FIG. 7, a space is required between the anchor bolts 30 so that the nuts 4 can be tightened. There is a limit to the number of anchor bolts 30 that can be arranged. When the number of anchor bolts 30 increases,
When assembling the column base material, there arises a problem that the positioning work between the mounting hole of the base plate 23 and the anchor bolt 30 buried in advance becomes difficult.

In view of the above, the present invention has been made in view of the above-mentioned problems, and has a steel pipe structural column base in which the column base can be easily fitted, the column base can be easily constructed, and the tensile strength can be increased. It is an object to provide a method for reinforcing a part.

[0010]

Means for Solving the Problems A method for reinforcing a column-base portion of a steel pipe structure according to the present invention employs the following means to solve the above problems.

In other words, the method for reinforcing a steel pipe structural column base according to the present invention is characterized in that the steel pipe column and a base plate integrally provided on the leg portion of the steel pipe column are anchored by using anchor bolts embedded in the base concrete. In the method of reinforcing a steel pipe structure column base fixed to the base, one end of a reinforcing bar is buried in the foundation concrete, and an opening 10 to 20 mm larger than the diameter of the reinforcing bar is provided in a base plate inside the steel pipe column. The other end side is inserted and arranged, and concrete is poured into the steel pipe column to a height at which the other end side of the rebar is sufficiently embedded.

According to the structure of the present invention, in addition to the anchor bolts on the outer periphery of the steel pipe column, the reinforcing steel can be disposed inside the steel pipe column. By arranging the reinforcing bars inside the cross section of the steel pipe column in this way, the amount of reinforcing bars that can be arranged on the column bases can be increased more than twice as much as the conventional column bases, and the tensile strength can be doubled. It can be raised more than that.

Further, according to the present invention, when the reinforcing steel is arranged inside the cross section of the steel pipe column and the inside of the steel pipe column is filled with concrete, the internal concrete is restrained by the steel pipe on the outer peripheral portion, so that the inner surface of the steel pipe adheres. Strength and bond strength of rebar become very high. For this reason, the reinforcing bars arranged in the concrete inside the steel pipe can have higher strength than conventional large-diameter reinforcing bars when compared at the same anchoring length. Further, since the reinforcing bars arranged inside penetrate the base plate, the base plate acts as a supporting plate against the tensile force of the reinforcing bars, thereby increasing the fixing strength. As a result, the column base of the steel pipe structure can withstand a strong earthquake.

Further, due to the two synergistic effects, the reinforcing bar disposed inside the steel pipe column usually has a reinforcing bar diameter of 3 mm.
Sufficient fixing strength can be obtained with a fixing length that is less than half the fixing length, which was required about 0 to 40 times.

[0015] Therefore, the anchoring length (the portion protruding above the ground from the foundation concrete) can be shortened, so that the work of inserting a reinforcing bar into the opening of the base plate when building a steel pipe column is facilitated, and as a result, the method of building the steel pipe is easy. Construction at the time becomes easy.

Further, according to the structure of the present invention, since the tensile stress transmitted by the base plate and the anchor bolt is transmitted mainly by the reinforcing bar, the thickness of the base plate corresponds to the force shared by the supporting pressure of the base plate. Any thickness can be used as long as it can be made, and it can be relatively thin.

As described above, according to the reinforcing method of the present invention, the tensile strength of the column-base portion of the steel pipe structure can be increased twice or more as compared with the conventional case, and the transmission of stress can be made more reliable.

Further, according to the reinforcing method of the present invention, unlike the case where the number of anchor bolts is increased, it is not necessary to increase the size of the base plate, and even if the tensile strength of the column base becomes twice or more of the conventional one. The fit is the same as before.

Furthermore, according to the reinforcing method of the present invention, since the fixing length of the connecting reinforcing bar to the steel pipe column is relatively short, the work of assembling the steel pipe column base is easy. In addition, there is no need to perform a tightening operation such as an anchor bolt on the connecting rebar, and only concrete is injected and cast into the steel pipe, so that workability is good.

The cross-sectional shape of the steel pipe may be, for example, a square steel pipe or a round steel pipe. Further, as a type of the reinforcing bar, a deformed reinforcing bar having an uneven shape can be exemplified. In addition, the present invention can be exemplified by a case of a root winding type in addition to the exposure type. In the case of the root winding type, a rigid connection method is used.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for reinforcing a steel pipe structural column base according to an embodiment of the present invention will be described below with reference to FIGS. This embodiment is applied to a column base of an exposed steel pipe structure, and FIG. 1 shows a longitudinal sectional view of the column base, and FIG. 2 shows a plan sectional view.

First, the structure of the steel pipe column base of this embodiment will be described. Four anchor bolts 3a to 3d are embedded in the foundation concrete 5 in a state where respective screw portions are left on the ground. Anchor bolt 3a
3 to 3d, the bolt diameter is 16 mm, and the length of the embedded portion is about 700 mm (40 times or more the bolt diameter). The anchor bolts 3a to 3d are evenly allocated and arranged as shown in a plan sectional view of FIG.

Also, five connecting rebars 6a to 6e are preliminarily embedded in the foundation concrete 5 while leaving a predetermined length on the ground. These connection reinforcing bars 6a to 6e
Is a deformed reinforcing bar having irregularities, and D25 (rebar diameter 2
5 mm). The length of the portion remaining on the ground is 500 mm (20 times the rebar diameter), and the length of the embedded portion is 1000 m in consideration of the tensile stress.
m (40 times the rebar diameter). In addition, connection rebar 6a-6
As shown in the plan sectional view of FIG. 2, e is equally allocated and disposed.

The column base material is composed of a steel tube column 1 and a base plate 2 and is formed by welding the base plate 2 to the leg portion of the steel tube column 1. The base plate 2 has four anchor bolt openings 2a to 2d, and the anchor bolt openings 2a to 2d are opened corresponding to the positions where the anchor bolts 3a to 3d are embedded.

The base plate 2 has five connecting-bar openings 7a to 7e, and the connecting-bar openings 7a to 7e.
e is also opened corresponding to the embedding positions of the five connecting reinforcing bars 6a to 6e. The connection rebar openings 7 a to 7 e formed in the base plate 2 have opening diameters of the connection rebar 6.
35mm that is 10mm larger than the diameter of a to 6e (25mm)
It is.

The base plate 2 is connected to the anchor bolts 3a to 3d and the connecting reinforcing bars 6a to 6e when the steel pipe is to be built.
Is inserted and arranged, and the nut 4 is fastened to the anchor bolts 3a to 3d in a double manner, and is fixed to the foundation concrete 5. The reason why the nut 4 is double-tightened is to prevent detent.

As shown in a plan sectional view of FIG. 2, the steel pipe column 1 has four notches 1a to 1 at positions where the anchor bolts 3a to 3d and the base plate 2 are tightened with the nut 4.
d. The steel pipe column 1 has a concrete filling opening 9 at the upper end of the column base.

The concrete filling opening 9 provided in the steel pipe column 1 is used to fill concrete 8 into the steel pipe column 1 from this opening and bury the portions of the five connecting reinforcing bars 6a to 6e that have come out above the ground. It is. Therefore, the concrete filling opening 9 is provided at a position of the steel pipe column 1 higher than the portions of the connecting reinforcing bars 6a to 6e that have come out above the ground. After the concrete is filled in the column base, the concrete filling opening 9 is closed.

Next, the operation of this embodiment will be described.
According to the configuration of this embodiment, in addition to the anchor bolts 3 on the outer periphery of the steel pipe column 1, the connecting reinforcing bars 6 a to 6 e are provided inside the steel pipe column 1.
Can be inserted through the base plate 2. As described above, the connecting reinforcing bars 6a to 6e are inserted and arranged inside the steel pipe column 1 and fixed inside the steel pipe column 1 with the concrete 8, so that the amount of the reinforcing bar that can be arranged on the column base compared with the conventional column base is reduced. It can be increased about twice or more, and the tensile strength is about 2
It can be more than doubled.

Further, according to this embodiment, when the connecting reinforcing bars 6a to 6e are arranged inside the steel pipe column 1 and the concrete 8 is filled in the steel pipe column 1, the internal concrete 8 becomes the steel pipe column of the outer peripheral portion. 1 steel pipe column 1
The adhesion strength on the inner surface is increased, and the adhesion strength on the fixing length L (see FIG. 1) of the connection reinforcing bars 6a to 6e is extremely increased. For this reason, the connecting reinforcing bars 6a to 6e arranged in the concrete 8 inside the steel pipe column 1 are made to have higher strength than the conventional main reinforcing bar used in the reinforced concrete structure when compared with the case of the same anchoring length. Can be. Further, since the connecting reinforcing bars 6a to 6e arranged inside penetrate the base plate 2, the base plate 2 acts as a supporting plate against the tensile force of the connecting reinforcing bars 6a to 6e, thereby increasing the fixing strength.

Due to this synergistic effect, the connecting reinforcing bars 6a to 6e disposed inside the steel pipe column 1 have a fixing length of less than half the fixing length conventionally required about 30 to 40 times the diameter of the reinforcing bar. And sufficient fixing strength can be obtained.

Therefore, the portion above the ground concrete 5 including the fixing length L can be shortened.
The work of inserting the connection reinforcing bars 6a to 6e into the opening of the base plate 2 when the steel pipe column is to be built becomes easy, and as a result, the construction when building the steel pipe column becomes easy.

Further, according to the configuration of this embodiment, the tensile stress transmitted by the base plate and the anchor bolt is transmitted mainly by the connecting reinforcing bars 6a to 6e.
The thickness of the base plate 2 may be any thickness as long as it can cope with the force shared by the supporting pressure of the base plate 2, and can be relatively thin.

As described above, according to the reinforcing method of this embodiment, the tensile strength of the column-base portion of the steel pipe structure can be increased twice or more as compared with the conventional case, and the transmission of stress can be made more reliable.

Further, according to this embodiment, it is not necessary to increase the number of anchor bolts or increase the size of the base plate as in the conventional case, so that the column base can be accommodated well.

In this embodiment, the case where five connecting rebars of D25 are used and the opening diameter of the base plate 2 is set to 35 mm has been described. However, the connecting rebars are not limited to deformed rebars. The number, type and diameter of the reinforcing bars and the opening diameter of the base plate can be set according to the reinforcing bar strength and the concrete strength to be used. The opening diameter of the base plate is 10 mm from the diameter of the connecting rebar.
It can be set appropriately within a range larger by 20 mm.

[Another Embodiment] Next, another embodiment will be described with reference to FIGS. This alternative embodiment is applied to a column-base portion of a steel tube structure of a root-winding type. FIG. 3 shows a vertical cross-sectional view of the column-base portion, and FIG. 4 shows a plan cross-sectional view. In addition, the steel pipe structure column base of the root winding type, the column main reinforcement is set up outside the steel pipe structure column base of the exposed type described in the above-mentioned embodiment, and further the column shear reinforcement is arranged, and coated concrete is used. It is a nemaki. Therefore, in the description of another embodiment, it is assumed that an exposed steel pipe structure column base has been assembled in advance. In FIGS. 3 and 4, those having the same reference numerals as those in FIGS. 1 and 2 have the same functions, and therefore description thereof will be omitted.

In the column-base portion of the steel pipe structure of the root winding type, four anchor bolts 3a to 3
In addition to d and the five connecting reinforcing bars 6a to 6e, twelve main column reinforcing bars 11a to 11l are preliminarily embedded with a predetermined length left on the ground. The pillar main bars 11a to 11
1 is a deformed reinforcing bar having irregularities, and uses D19 (rebar diameter 19 mm). The length of the embedded portion is set to 400 mm (40 times the diameter of the reinforcing bar) in consideration of the tensile stress. In addition, as shown in the plan cross-sectional view of FIG.
Except for the nut tightening positions a to 3d, the steel pipe columns 1 are evenly allocated at the four corners so as to surround the steel pipe columns 1 at four corners.

After the exposed steel pipe structural column base is constructed, column shear reinforcing bars 12 are arranged at intervals of 10 cm so as to be orthogonal to the column main bars 11a to 11l. The base-winding type steel pipe structure column base has a column shear reinforcing bar around it.
After the reinforcing bars 2 are arranged, a formwork (not shown) is arranged around the column bases and the reinforcing bars, and the coated concrete 10 is cast to form a reinforced steel frame concrete structure.

According to the structure of another embodiment, in addition to the effect of the method of reinforcing the column base of the exposed steel pipe structure, the tensile strength of the column base of the steel pipe structure is further increased, and the transmission of stress is further improved. It can be assured.

[0041]

As described above, according to the reinforcing method of the present invention, the tensile strength of the column-base portion of the steel pipe structure is reduced by the conventional two.
In addition to increasing the stress more than twice, the transmission of stress can be made more reliable. As a result, the column base of the steel pipe structure can withstand a strong earthquake.

According to the reinforcing method of the present invention, unlike the case where the number of anchor bolts is increased, it is not necessary to increase the size of the base plate, and even if the tensile strength of the column base is twice or more the conventional one. The fit is the same as before.

Further, according to the reinforcing method of the present invention, the fixing length of the connecting rebar to the steel pipe column is relatively short, so that the work of assembling the steel pipe column base is easy. In addition, there is no need to perform a tightening operation such as an anchor bolt on the connecting rebar, and only concrete is injected and cast into the steel pipe, so that workability is good.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a steel pipe column base to which a method of reinforcing a column base of a steel pipe structure according to an embodiment of the present invention is applied.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a vertical sectional view of a steel pipe column base when the method of the present invention is applied to a filled-coated steel pipe concrete structure as another embodiment.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is an elevation view showing a conventional method of reinforcing a steel pipe structural column base.

FIG. 6 is a sectional view taken along line AA of FIG. 5;

FIG. 7 is an elevation view showing a conventional method of reinforcing a steel pipe structural column base.

8 is a sectional view taken along line AA of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel pipe column 2 ... Base plate 3a-3d ... Anchor bolt 4 ... Nut 5 ... Foundation concrete 6a-6e ... Reinforcing bar (connecting rebar) 7a-7e ... Opening for connecting reinforcing bar 8 ... Filling concrete 9 ... Opening for concrete filling 10 ... Coating Concrete 11a-11l ... Column main reinforcement 12 ... Column shear reinforcement L ... Connection reinforcement anchoring length

Claims (3)

[Claims] 1. A method of reinforcing a steel pipe structural column base for fixing a steel pipe column and a base plate integrally provided on a leg portion of the steel tube column to the basic concrete using anchor bolts embedded in the basic concrete. One end of the rebar is buried in the foundation concrete, and the base plate inside the steel pipe column is 10
A steel pipe structure, wherein an opening larger by about 20 mm is provided, the other end of the rebar is inserted and arranged in the opening, and concrete is poured into the steel pipe column to a height at which the other end of the rebar is sufficiently embedded. How to reinforce the column base. 2. The method according to claim 1, wherein the reinforcing bar is a deformed reinforcing bar having irregularities. 3. The method according to claim 1, wherein reinforced concrete is wrapped around the steel pipe column of the steel pipe structure column base.