JP3522415B2 - Steel tube column reinforcement structure - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing structure for a steel pipe column, and more particularly to a structure in which a circular steel pipe is used as a column member, such as a bridge pier, a steel tower, or a structure, when an external force such as an earthquake acts. In addition, the present invention relates to an economical and rational steel pipe column reinforcing structure that locally reinforces a portion of a column member where large stress is generated to dramatically improve the deformation performance.

[0002]

2. Description of the Related Art Generally, when a bending moment due to seismic force exceeding a design external force is applied to a steel pipe column that receives an axial compressive force, the edge stress on the compression side exceeds the yield point of the material. At the cross-section position, a local buckling 40 having a half-wave convex shape may occur in the tube axis direction (see FIG. 10A). Such local buckling does not completely return to the original state even if the bending moment is released, and deformation remains. When the bending moment next acts in the opposite direction to the above in this state, similar local buckling occurs on the opposite side of the cross section where the buckling occurred earlier. Furthermore, when the bending moment acts in a positive / negative alternating manner, each convex buckling deformation mode develops in the circumferential direction, and eventually both buckling modes fuse together to form a so-called lantern buckling 50 which goes around the steel pipe cross section. (See FIG. 10B). In this process, the load bearing capacity of the steel pipe column increases until local buckling occurs, and reaches a maximum value almost at the same time as the occurrence of local buckling, and thereafter the load bearing capacity decreases with the growth of buckling deformation. To go. The Great Hanshin Earthquake (1995.1.1)
Also in 7), convex local buckling or lantern buckling occurs at the weakest cross-section position of the member such as the plate thickness change part in the middle of the pillar, the manhole part, etc. just above the root-wrapping concrete at the base part of the steel pipe pier. It was

In considering a reinforcing structure for improving the seismic performance of a steel pipe column, how to suppress the occurrence of the above local buckling or bank light buckling is an important matter. Conventionally, a structure (the former) in which the inside of a steel pipe is filled with concrete is known as a reinforcing structure for preventing the occurrence of local buckling. Further, as disclosed in Japanese Patent Laid-Open No. 6-167073, a structure in which the outer surface of a steel pipe is wound with concrete or a steel plate (the latter), and a reinforcement having an inner surface larger than the outer surface of the steel pipe column. A reinforcing structure (the latter) in which a hardening material such as mortar or concrete is filled between the steel and the inner surface thereof is also known.

[0004]

However, in the former reinforced structure, although the strength of the steel pipe column can be increased in order to improve the load bearing capacity of the steel pipe column, on the contrary, it becomes a large acting force on the foundation. There is a risk that the weak parts such as the foundation and anchor bolts will be overloaded, causing damage to the weak parts. In addition, in the latter reinforced structure, problems due to an increase in load bearing capacity, and when an earthquake force exceeding the design external force acts, local buckling occurs in the unreinforced part near the reinforced part or in an unexpected part. Therefore, there is a problem that the reinforcing effect cannot be obtained as expected.

The present invention has been made in view of the above problems, and its object is to make the diameter of the steel pipe column larger than the outer diameter of the steel pipe column with respect to the site where the local buckling occurs. By installing a reinforced steel pipe having an inner diameter at a predetermined distance from the outer circumference of the steel pipe column, it is possible to deform the steel pipe column body without increasing the load-bearing force when receiving a large external force such as an earthquake. An object is to provide an economical and rational reinforcing structure that can improve the performance only and minimize the reinforcement of the foundation and anchor bolts.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a steel pipe column reinforcement structure where local buckling occurs when a large external force such as an earthquake is applied. A reinforcing steel pipe having an inner diameter larger than the outer diameter of the steel pipe column is installed at a predetermined interval without filling the outer periphery of the steel pipe column with a hardening material. Is. In the above-mentioned steel pipe column reinforcing structure,
In order to prevent corrosion and contamination by foreign materials,
Or is characterized by being filled with a compressible material.
It

Next, the operation of the present invention will be described.
Now, when a large earthquake occurs and a large external force is applied to the reinforcing structure, buckling occurs in the steel pipe column. The buckling is deformed to some extent, and no force is transmitted to the reinforced steel pipe until the outer surface of the buckling portion of the steel pipe column comes into contact with the inner surface of the reinforced steel pipe, and the steel pipe column behaves independently. Then, after the buckling deformation of the steel pipe column progresses and the outer surface of the buckling portion contacts the reinforcing steel pipe, the reinforcing steel pipe restrains the buckling deformation. And, the interval between the steel pipe column and the reinforced steel pipe is designed with a predetermined amount so as to match the amount of buckling deformation when the maximum load bearing capacity of the steel pipe column alone is indicated, so that the buckling is reinforced steel pipe. After the contact, it is possible to improve only the deformability and increase the energy absorption amount without increasing the load bearing capacity and the rigidity of the steel pipe column.

[0008]

1 is a schematic configuration diagram of a general viaduct leg to which an embodiment of a reinforcing structure for a steel pipe column of the present invention is applied. The viaduct leg 20 is a foundation 21 that contacts the ground, It consists of bridge piers 22 planted in the foundation 21 and bridge superstructures 23 installed above the bridge piers 22. The foundation 21 is composed of a footing 24, a plurality of piles 25 planted under the footing 24, a base plate 26 embedded in the footing 24, and anchor bolts 27 for fixing the pier 22. In the vicinity of the pier base 30 directly above the root winding part 28 of the foundation 21 and in the weak points such as the thickness change part 31 and the manhole 32 of the pier 22, local concentration of stress may occur at the time of a large earthquake and local buckling may occur. There is. The present invention is
The basic idea is to reinforce the parts where local buckling or levee lantern buckling may occur in the event of a large earthquake, and how to suppress the buckling. Therefore, the present invention is a reinforcing structure for a steel pipe column, wherein a reinforcing steel pipe having an inner diameter larger than the outer diameter of the steel pipe column is filled in a region where local buckling occurs, and a hardening material is filled in the outer periphery of the steel pipe column. By installing them with a certain interval without doing so, when a large external force such as an earthquake is received, the deformability is improved and reinforcement is performed without increasing the load bearing capacity of the steel pipe column body. I am trying to Here, the “deformation performance” means the performance of increasing the energy absorption without impairing the load bearing capacity even if a large displacement occurs. FIG. 2 is a diagram for explaining the outline of the reinforcing structure of the steel pipe column showing the embodiment of the present invention, and FIG.
2 is a perspective view of a reinforcing structure for a steel pipe column, and FIG.
It is sectional drawing cut | disconnected by the AA line of (a). In the figure, a reinforcing steel pipe 2 having an inner diameter larger than the outer diameter of the steel pipe column 1 is provided at the outer periphery of the steel pipe column 1 at the site of the steel pipe column 1 where local buckling occurs when a large external force such as an earthquake is applied. Is installed with a predetermined interval 3 maintained. The space 3 is determined by the outer diameter, wall thickness, etc. of the steel pipe column 1, but before the space 3 is too small and the load bearing capacity of the reinforcing structure becomes maximum, the inner surface of the reinforced steel pipe 2 buckles the steel pipe column 1. If the buckling deformation is restrained by coming into contact with the deformed portion, the load bearing capacity of the steel pipe column will increase. Therefore, the interval 3 is increased to some extent so as to allow the occurrence of the above-described local buckling up to a predetermined deformation amount, and the increase in load bearing capacity and rigidity is suppressed. And the size of the said space | interval 3 is made to correspond with the amount of buckling deformation at the time of showing the maximum load-bearing force of a steel pipe column alone, and after the said buckling contacts a reinforced steel pipe, the load-bearing force of the steel pipe column 1 and Only the deformation performance can be improved without increasing the rigidity.

3A and 3B show a first embodiment for attaching a reinforcing steel pipe to a steel pipe column. FIG. 3A is a perspective view thereof, and FIG. 3B is a partially cutaway sectional view thereof. Is. In the figure, an L-shaped metal fitting 4 made of a plurality of steel materials is welded to the outer peripheral surface of a steel pipe pillar 1 in the same plane, and the reinforcing steel pipe 2 is maintained at a predetermined distance 3 from the steel pipe pillar 1 while maintaining the L-shaped metal fitting. It is supported by 4.

4A and 4B show a second embodiment for attaching the reinforcing steel pipe to the steel pipe column. FIG. 4A is a perspective view thereof, and FIG. 4B is a partially cutaway sectional view thereof. is there. In the figure, a gap 3 between the outer circumference of the steel pipe column 1 and the inner circumference of the reinforcing steel pipe 2
A plurality of rubber wedges 5 are driven in from both sides and sandwiched. The weight of the reinforcing steel pipe 2 is supported by the elastic force of the wedge 5 itself and the frictional force between the outer peripheral surface of the steel pipe column 1 and the inner peripheral surface of the reinforcing steel pipe 2 and the wedge 5, and the predetermined interval 3 is maintained. It is attached to the steel pipe pillar 1 while maintaining it. Two examples of mounting the steel pipe column 1 and the reinforced steel pipe 2 have been described, but it goes without saying that other mounting means can be adopted as long as the local buckling occurring in the steel pipe column 1 is not hindered. is there.

The present invention not only reinforces existing structures,
Of course, it can be applied to a new structure. And
When the present invention is applied to an existing structure, the reinforcing structure can be formed into a circular shape by welding and joining two or more divided arc-shaped steel plates on site. In the case of a new installation, a reinforcing structure can be obtained by the method described above or by attaching a reinforcing steel pipe formed into a circular shape in advance in a manufacturing factory to the main body. Further, in the existing structure or the new structure, if the load bearing capacity is sufficient, the gap 3 between the steel pipe column and the reinforced steel pipe may be made slightly smaller than that described above. In addition, a fluid material or a compressible material may be filled in the space 3 in order to prevent corrosion and foreign matter. Then, the plate thickness, axial length, etc. of the reinforced steel pipe are determined in consideration of the plate thickness of the steel pipe column main body, the strength, and the axial length of a place where buckling easily occurs.

Next, the operation of this embodiment will be described. Now, when a large earthquake occurs and a large external force is applied to the reinforcing structure, buckling occurs in the steel pipe column 1. The buckling is deformed to some extent, and no force is transmitted to the reinforcing steel pipe 2 until the outer surface of the buckling portion of the steel pipe column contacts the inner surface of the deformed reinforcing steel pipe 2, and the steel pipe column 1 exhibits independent behavior. . After the buckling deformation of the steel pipe column 1 progresses and comes into contact with the reinforcing steel pipe 2, the reinforcing steel pipe 2 restrains the buckling deformation. The gap 3 between the steel pipe column 1 and the reinforced steel pipe 2 is designed to have a predetermined amount so as to match the amount of buckling deformation when the maximum load bearing capacity of the steel pipe column 1 alone is exhibited. After coming into contact with the reinforced steel pipe, it is possible to improve only the deformability and increase the energy absorption amount without increasing the load bearing capacity and rigidity of the steel pipe column 1.

Next, the results of an experiment of applying a force to a bridge pier of an elevated bridge assuming seismic force will be described. Assuming a bridge pier, the specimen will be a cantilevered column of circular steel pipe that is reduced to about 1/3.
The test piece shown in Fig. 5 is the test piece No. 1 only for the main body of the steel tube column which is not reinforced, and is the standard for confirming the reinforcing effect. The test piece shown in FIG. 6 is the test piece No. 2 in which a reinforcing steel pipe is installed, and the size, shape, and material are the same as the test piece 1. The height of the reinforced steel pipe is 60
The thickness was 0 mm, the plate thickness was t9, and the distance between the specimen No. 2 and the reinforcing steel pipe was 10 mm. As a loading condition, while maintaining a state in which a constant vertical axial force is applied, a horizontal force corresponding to an earthquake load is repeatedly applied to the top of the column while gradually increasing. The loading direction for the specimen is shown in FIG. As a result of the experiment,
The loading history curves of horizontal load and horizontal displacement at the top of the column are shown in Fig. 7 (Specimen No. 1) and Fig. 8 (Specimen No. 2). In addition, the envelope for horizontal load and horizontal displacement is
Fig. 9 shows the results for No. 1 and specimen No. 2.

From the experimental results, comparing FIG. 8 and FIG.
Reinforced specimen No. 2 (see Fig. 8) draws almost the same trajectory up to the maximum load-bearing capacity as specimen No. 1 without reinforcement (see Fig. 7). After the maximum load bearing capacity, Specimen 2 is less deteriorated per loop than Specimen No. 1 and horizontal displacement is extended. From this, the specimen No.
It was found that the specimen No. 2 had a significantly improved deformation performance and increased energy absorption after the maximum load bearing capacity compared to the specimen No. 1, and achieved the intended purpose. This can be said from the state of the envelope shown in FIG.

[0015]

As described above, the present invention has an inner diameter larger than the outer diameter of the steel pipe column with respect to the portion of the steel pipe column where local buckling occurs when a large external force such as an earthquake is applied. Since the reinforced steel pipe was installed at a predetermined distance from the outer circumference of the steel pipe column, when a large earthquake occurs and a large external force is applied to the steel pipe column, the steel pipe column will buckle and the buckling will occur. The force is not transmitted to the reinforcing steel pipe until it contacts the inner surface of the reinforcing steel pipe, but after the buckling contacts the reinforcing steel pipe, the reinforcing steel pipe restrains the deformation of the buckling. Then, since the interval has a predetermined amount so as to match the buckling deformation amount when the maximum load bearing capacity of the steel pipe column alone is shown, after the buckling contacts the reinforced steel pipe,
It is possible to improve only the deformation performance and increase the amount of energy absorption without increasing the load bearing capacity and rigidity of the steel pipe column, and therefore the reinforcement of the foundation, anchor bolts, etc. can be minimized. It is economical and rational.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a general viaduct leg to which an embodiment of a reinforcing structure for a steel pipe column of the present invention is applied.

FIG. 2 is a diagram for explaining an outline of a reinforcing structure for a steel pipe column showing an embodiment of the present invention, FIG. 2 (a) is a perspective view of the reinforcing structure for a steel pipe column, and FIG. A- in FIG.
It is sectional drawing cut | disconnected by the A line.

FIG. 3 shows a first embodiment for attaching a reinforced steel pipe to a steel pipe column, FIG. 3 (a) is a perspective view thereof, and FIG.
(B) is a partially cutaway sectional view thereof.

FIG. 4 shows a second embodiment for attaching a reinforced steel pipe to a steel pipe column, FIG. 4 (a) is a perspective view thereof, and FIG.
(B) is a partially cutaway sectional view thereof.

FIG. 5 is a front view showing sample No. 1 which is not reinforced.

[Fig. 6] Fig. 6 is a diagram showing Reinforced Specimen No. 2,
6 (a) is a front view thereof, and FIG. 6 (b) is B of FIG. 6 (a).
It is sectional drawing cut | disconnected by the -B line.

FIG. 7 is a diagram showing a loading history curve regarding a horizontal load and a horizontal displacement in a column top portion of the specimen No. 1;

FIG. 8 is a diagram showing a loading history curve regarding a horizontal load and a horizontal displacement at a column top portion of the specimen No. 2;

FIG. 9 is a view showing envelopes of the horizontal load and the horizontal displacement relationship of the sample No. 1 and the sample No. 2.

FIG. 10 is a perspective view showing an example of local buckling occurring in a steel pipe column, FIG. 10 (a) is a perspective view showing half-wave convex local buckling, and FIG. 10 (b) is a bank. It is a perspective view which shows a light buckling.

[Explanation of symbols]

1 ... Steel tube column 2 ... Reinforced steel pipe 3 ... interval 4 ... L-shaped metal fittings 5 ... rubber wedge

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiromichi Anba 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Masahiro Terada 20-1 Shintomi, Futtsu City, Chiba Japan (56) References Japanese Patent Laid-Open No. 6-167073 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) E01D 21/00 E01D 19/02 E04G 23/02

Claims (2)

(57) [Claims] 1. In a reinforcing structure for a steel pipe column, a reinforcing steel pipe having an inner diameter larger than the outer diameter of the steel pipe column is provided for a portion of the steel pipe column where local buckling occurs when a large external force such as an earthquake is applied. A reinforcing structure for a steel pipe column, which is installed at a predetermined interval without filling the outer periphery of the steel pipe column with a hardening material . 2. Corrosion prevention and contamination of foreign matter within the predetermined interval.
Do not fill with a fluid or compressible material to prevent entry.
The steel pipe column reinforcing structure according to claim 1.