JP6160043B2 - Steel pipe column structure and manufacturing method thereof - Google Patents

Description

  The present invention relates to a steel chimney, a bridge main tower, a wind power generation tower, a wind power generation support structure, a marine structure, a building structure, a bridge structure, and a steel pipe column structure, and a manufacturing method thereof.

Examples of the steel pipe column structure having a circular cross section include a steel chimney, a tower for wind power generation, an offshore wind power generation foundation, and the like.
When focusing on the steel pipe diameter in the height direction, such a steel pipe pillar structure is large in that the steel pipe diameter is uniform, and the steel pipe diameter is gradually reduced as it tapers in the height direction. Separated.
In addition, the plate thickness of the steel pipe is generally the same in the height direction or gradually decreased as it goes upward, but the plate thickness in the circumferential direction is the same (non-patent document). 1).

Moreover, like the circular steel pipe column which has the thick part disclosed by patent document 1, it devised so that it might become small gradually as the steel pipe diameter goes upwards, and it becomes thick as the plate | board thickness of a steel pipe goes down. There are also things.
Furthermore, like a steel member for a building structure disclosed in Patent Document 2, for example, a thick portion is disposed at a portion where the acting stress is large, such as a joint between a beam and a column, and a thin portion is disposed at a portion where the acting stress is small. Some parts are arranged.

The steel pipe column structure has a large diameter and thick steel pipe. In such a method of manufacturing a steel pipe column structure, a round steel pipe or a square steel pipe is manufactured by rolling a rolled steel plate. The height of the manufactured steel pipe is 3 to 5 m which is the width of the rolled steel sheet, and the steel pipe column structure is manufactured by sequentially stacking them upward and joining them with welding, bolts or the like.
The circular steel pipe is manufactured by bending a rolled steel sheet with a curvature in the rolling direction (L direction).

  If the diameter of the steel pipe is as large as 10m, it may not be possible to produce a round steel pipe with a single rolled steel sheet. In that case, the rolled steel sheet is connected to form a long sheet, which is then rolled into an annular shape. Produced.

In addition, in the case of a square steel pipe (rectangular steel pipe column structure) with a rectangular cross section, a rectangular steel pipe is manufactured by stacking and joining steel plates in the circumferential direction, and the rectangular steel pipes are stacked on top and joined. It is common to manufacture.
In addition, the production of square steel pipes is determined by the performance of the press machine, and square steel pipes with a height of about 3 to 15 m are sequentially stacked. In this case, the bending direction of the rolled steel sheet may be either.

JP 2005-264535 A JP-A-6-288033

Tower steel structure design guidelines and explanation (1980), Architectural Institute of Japan

The steel pipe column structure of the above-described conventional example is a device for a structure that mainly improves earthquake resistance.
However, in a tall steel pipe column structure, it is more important to improve wind resistance than earthquake resistance. In this case, as a general problem, a static problem is related to static wind load, and a dynamic problem is related to vortex excitation and gust response.
Among these, vortex excitation is vibration caused by Karman vortices, which occurs at a certain range of wind speed, and swing is also limited. When the magnitude of the shaking is larger than the allowable value, the main part that constitutes the steel pipe column structure is adopted as a countermeasure, either by changing the shape of the steel pipe column structure or by installing a vibration control device to suppress the shaking Increasing the plate thickness is not implemented because it is uneconomical.
Further, since the static wind load is proportional to the square of the wind speed, it becomes the maximum wind load at the design wind speed (the maximum wind speed during the service period). The gust response is a fluctuation caused by fluctuations in wind speed, and the response (amount of fluctuation) is proportional to the square of the wind speed. Therefore, the gust response is designed as an increment of the static wind load.

The above explanation is a problem for a general structure that receives a wind load. However, in the case of a steel pipe column that supports a wind turbine used for wind power generation, the wind applied to the general steel pipe column structure as described above. The situation is different from the load.
In the case of a windmill, the blades are tilted so as to receive wind in a region where the wind speed is relatively low (for example, 25 m / s or less). On the other hand, when the wind speed becomes high, the structure is configured to receive wind in order to prevent the power generation equipment from being overloaded.

This point will be described in more detail with reference to FIG. FIG. 24 is a graph showing the relationship between the wind speed and the wind load applied to the structure. The vertical axis represents the wind load applied to the structure, and the horizontal axis represents the wind speed. Moreover, in FIG. 24, the continuous line has shown the steel pipe pillar of the windmill support structure, and the broken line has shown the general conventional steel pipe pillar.
As shown in FIG. 24, in the steel pipe column as the wind turbine support structure, the wind load in the vicinity of the wind speed of 10 to 25 m / s is at the same level as the wind load at the high wind speed. The frequency of the wind speed region in the vicinity of the wind speed of 10 to 25 m / s is much higher than that of the high wind speed. Since the wind load is received at a high frequency, fatigue due to repeated external forces becomes a problem in the wind turbine support structure.

In fatigue, since the fatigue strength of the welded joint is weaker than that of the base metal, fatigue of the welded portion in the direction orthogonal to the axis of the steel tube column structure is particularly problematic in steel tube column structures that are repeatedly subjected to external force. In order to deal with such fatigue problems of welds, conventionally, a method of finishing the weld toes to increase the fatigue strength grade, a method of improving the structure near the weld to reduce the generated stress, or a steel pipe A method of increasing the thickness of the column structure has been performed.
Among such methods, regarding the method of increasing the plate thickness of the steel pipe column structure, increasing the plate thickness of the entire steel pipe column structure including not only the welded portion but also other portions is performed. For this reason, there exists a problem that the amount of steel materials used increases. That is, if the thickness of not only the welded portion but also other portions is increased, the portions other than the welded portion have a surplus in terms of stress, which is uneconomical in design.

  The present invention has been made to solve the above-described problems, and provides a steel pipe column structure that can be rationally designed and a method of manufacturing the steel pipe column structure when the welding surface is orthogonal to the axial direction. Objective.

(1) Tubular Column structure according to the present invention, have a thick portion at both ends, joined with a plurality of steel tubes arranged in so that stacked in the axial direction of the tube, the thick portion of the steel pipe Welding The thick-walled portion includes a steel pipe column set to a plate thickness determined from the fatigue strength of the welded portion as a part of the structure.

(2) Further, in the above (1), a difference in plate thickness between the thick part and the other part in the steel pipe is 4 mm or less, and the thick part and the other part An inclined portion in which the plate thickness gradually changes is provided between the portions, and the plate thickness gradient in the inclined portion is set to 1/100 or less.

(3) Further, in the above (1) or (2), the axial length of the thick portion is set to 2 m or less.

(4) A method for manufacturing a steel pipe column structure according to the present invention is the method for manufacturing a steel pipe column structure according to any one of the above (1) to (3), wherein both ends in the direction perpendicular to the rolling are welded portions. It is characterized by having a steel pipe manufacturing process in which a steel pipe formed by forming a thick steel plate determined from the fatigue strength of the ring into a ring shape and a steel pipe joining process in which the manufactured steel pipes are stacked and welded together is there.

(5) A method for manufacturing a steel pipe column structure according to the present invention is the method for manufacturing a steel pipe column structure according to any one of (1) to (3) above, wherein both ends in the rolling direction are welded portions. A steel pipe manufacturing process in which a plurality of steel plates formed in a thickness determined from fatigue strength are arranged in the circumferential direction and adjacent steel plates are welded together to produce a steel pipe, and a steel pipe joining process in which the manufactured steel pipes are stacked and welded together It is characterized by having.

  In the steel pipe column structure of the present invention, since a plurality of steel pipes having thick portions at both ends are stacked in the tube axis direction and the thick portions are welded to each other, the plate thickness other than the welded joint portion is formed. By reducing the thickness of the steel pipe, it is possible to provide an inexpensive steel pipe column structure with a rational structure in which the amount of steel used is reduced.

FIG. 1 is an explanatory diagram of a steel pipe column structure according to an embodiment of the present invention. FIG. 2 is a side view of a circular steel pipe constituting the steel pipe column structure shown in FIG. FIG. 3 is an explanatory view of a differential thickness steel plate used for manufacturing a circular steel pipe constituting the steel pipe column structure according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of a steel pipe column structure according to Embodiment 2 of the present invention. 5 is a cross-sectional view taken along the line AA in FIG. 6 is a side view of a circular steel pipe constituting the steel pipe column structure shown in FIG. FIG. 7 is an explanatory view of a differential thickness steel plate used for manufacturing the circular steel pipe shown in FIG. FIG. 8 is an explanatory diagram of a steel pipe column structure according to Embodiment 3 of the present invention. 9 is a cross-sectional view taken along the line AA in FIG. FIG. 10 is a side view of an octagonal steel pipe constituting the steel pipe column structure shown in FIG. FIG. 11 is an explanatory view of a differential thickness steel plate used for manufacturing the octagonal steel pipe shown in FIG. FIG. 12 is an explanatory diagram of a pier as a steel pipe column structure according to Embodiment 4 of the present invention. 13 is a cross-sectional view taken along line AA in FIG. FIG. 14 is a side view of the pier shown in FIG. FIG. 15 is an explanatory view of a differential thickness steel plate used for manufacturing the pier shown in FIG. FIG. 16 is an explanatory diagram of a pier as a steel pipe column structure according to Embodiment 5 of the present invention. 17 is a cross-sectional view taken along the line AA in FIG. 18 is a side view of the pier shown in FIG. FIG. 19 is an explanatory view of a differential thickness steel plate used for manufacturing the pier shown in FIG. 16. FIG. 20 is an explanatory diagram of a pier as a steel pipe column structure according to Embodiment 6 of the present invention. 21 is a cross-sectional view taken along the line AA in FIG. FIG. 22 is a side view of the pier shown in FIG. FIG. 23 is an explanatory view of a differential thickness steel plate used for manufacturing the pier shown in FIG. 20. FIG. 24 is a diagram for explaining the operation of the first embodiment of the present invention, and is a graph showing the relationship between the wind load and the wind speed. FIG. 25 is a diagram for explaining the operation of the first embodiment of the present invention, and is a diagram showing a moment distribution when the steel pipe column structure receives a wind load. FIG. 26 is an explanatory diagram for explaining the relationship between the plate thickness and fatigue strength of a conventional steel pipe column as a comparative example. FIG. 27 is an explanatory diagram for explaining the relationship between the plate thickness of the steel pipe column and the fatigue strength of the first embodiment. FIG. 28 is an explanatory diagram of an offshore structure according to the seventh embodiment. 29 is a cross-sectional view taken along line AA in FIG. FIG. 30 is an explanatory diagram of a steel pipe column structure according to the eighth embodiment.

[Embodiment 1]
This embodiment will be described with reference to FIGS.
The steel pipe column structure 1 of the present embodiment is constituted by a steel pipe column formed by stacking a plurality of steel pipes having thick portions at both ends in the tube axis direction and welding the thick portions. is there.
This will be specifically described below.

In the present embodiment, as an example of the steel pipe column structure 1, a tower in which wind turbine equipment is installed in the upper part is taken as an example, and such a tower generates a vibration perpendicular to the axial direction due to the wind. The problem is the fatigue strength of the welded surface orthogonal to.
As shown in FIG. 1, the steel pipe column structure 1 is formed by stacking 18 circular steel pipes (first circular steel pipe 1a to 18th circular steel pipe 1r) on the foundation 3 in the height direction. The parts are joined by butt welding. The part shown with the broken line in a figure is a position of a welding surface, and the welding surface is orthogonal to the axial direction of the steel pipe column structure 1. FIG.
The circular steel pipes are, in order from the bottom, a first circular steel pipe 1a, a second circular steel pipe 1b,..., And an eighteenth circular steel pipe 1r. For simplification, the diameter of each steel pipe is not tapered in the height direction.

FIG. 2 is an enlarged side view showing a side surface of the first circular steel pipe 1a. As shown in FIG. 2, the thickness of the first circular steel pipe 1a changes in the vertical direction. The portions where the plate thickness changes are the upper thick portion 5 (upper weld joint portion), the upper tapered portion 7, the thin portion 9, the lower tapered portion 11, and the lower thick portion 13 in order from the top. In this example, the diameter of the first circular steel pipe 1a is 6000 mm.
In the upper thick part 5 and the lower thick part 13 (lower weld joint part), in order to increase the fatigue strength, the plate thickness is increased to reduce the stress generated in the welded part. Since the fatigue strength grade of butt welding is the D grade and the base material is the A grade, considering only the fatigue strength, a stress about twice as large as that of the base material is required in the welded portion even with the same number of repetitions. In other words, considering only the fatigue strength, the base material portion may be half as thick as the welded portion. Therefore, in the present embodiment, the steel weight is reduced by setting the plate thickness of the welded joint as a necessary plate thickness and making other portions thinner than this plate thickness.

FIG. 25 is an explanatory diagram for explaining the moment distribution when a wind load is loaded on the steel pipe column structure 1 shown in FIG. 1, and FIG. 25 (a) shows the relationship between the steel pipe column structure 1 and the wind, FIG. 25B shows the moment distribution.
As shown in FIG. 25 (b), the moment distribution when the wind load is loaded on the steel pipe column structure 1 shown in FIG. 1 is larger on the lower side and smaller on the upper side.
Therefore, if it is a prior art which changes plate | board thickness according to action stress, when a circular steel pipe is assumed as a steel pipe pillar structure, if it is the same diameter, plate | board thickness will become thick, so that it is close to a foundation. That is, when considering the steel tube column structure of the simple cantilever structure shown in FIG. 1, the plate thickness of the first circular steel tube 1a is the largest, and the plate thickness gradually increases in the order of the second circular steel tube 1b and the third circular steel tube 1c. As shown in FIG. 2, the thickness of each circular steel pipe is changed in the vertical direction as shown in FIG. 2 as in the embodiment of the present invention. Completely different.

Here, the relationship between the fatigue strength of the welded joint and the plate thickness of the steel pipe column structure 1 will be described.
FIG. 26 shows the relationship between the thickness (FIG. 26 (a)) and the fatigue strength (FIG. 26 (b)) in the case where circular steel pipes having the same thickness are stacked and joined in the height direction (comparative example). Yes. FIG. 27 shows the relationship between the plate thickness (FIG. 27 (a)) and the fatigue strength (FIG. 27 (b)) for the steel pipe column structure 1 of the present embodiment.

In the case of a steel pipe column structure manufactured by welding a plurality of round steel pipes in the height direction, assuming that the plate thickness of each round steel pipe is the same, as shown in FIG. Decrease dramatically. In normal design, the thickness of the lower circular steel pipe is thicker than the thickness of the upper circular steel pipe because the cross section is changed according to the bending moment to determine the cross section. It is clear that the fatigue strength is significantly reduced.
On the other hand, in the steel pipe column structure of the present embodiment, the plate thickness of the welded portion of each circular steel pipe is designed with a plate thickness determined from the fatigue strength of the welded portion. Since it is designed with a plate thickness determined from the fatigue strength of the base metal in general (see FIG. 27A), the fatigue strength is constant for the entire steel pipe column structure (see FIG. 27B), which is very reasonable. Design.

Specifically, the upper and lower welded joints are thick (30 mm) to ensure the necessary fatigue strength, and the upper taper part 7 and the lower taper part 11 that gradually reduce the thickness of the parts connected to this are provided. The middle part is a thin part 9 (thickness: 26 mm). An upper taper portion 7 is provided at a portion connecting the upper weld joint portion and the thin portion so that the plate thickness gradually changes so that stress concentration does not occur at the portion where the plate thickness changes. The same applies to the lower taper portion connecting the lower welded portion and the thin portion.
The thickness gradient on the taper surface at the upper and lower taper portions is sufficient if the stress concentration is small, and in the usual design, the thickness gradient is 1/5 (the length is 5 mm or more with respect to 1 mm thickness reduction). Although mildness is preferred, stress concentration still occurs even with a 1/5 thickness gradient, so in order to achieve the maximum effect of the present invention without stress concentration, 1/100 ( It is preferable to provide a thickness gradient of not more than 100 mm with respect to a reduction of 1 mm in thickness.
In this example, the thickness gradient is set to 1/100.
Since the thickness of the upper and lower welded joints is 30 mm, the thickness of the thin part is 26 mm, and the thickness gradient is 1/100, the length of the upper taper part and the lower taper part is 400 mm.
The plate thickness gradient indicates the relationship between the amount of change in plate thickness and the length of the plate where the plate thickness changes. For example, when the length of the plate at the portion where the plate thickness changes is 100 mm and the plate thickness changing is 1 mm, the plate thickness gradient is 1/100. In this case, regardless of whether the portion where the plate thickness changes is a single-sided taper or a double-sided taper, only the amount of change in the plate thickness is considered.

  In the first circular steel pipe 1a of the present embodiment, the tapered portions are provided on both the outer surface side and the inner surface side. By doing in this way, it is because the structural axis in the 1st circular steel pipe 1a turns into a plate | board thickness center, and is preferable on a design. However, as shown in the embodiments described later, the tapered surface may be provided on either the outer surface side or the inner surface side.

  Moreover, since stress concentration occurs in the vicinity of the welded portion due to the shape of the weld finish, it is desirable that the plate thickness be constant in the vicinity of the welded portion. In that sense, the upper welded joint part and the lower welded joint part preferably have a predetermined length, but if this part is made too long, the thick part will become longer and the cost will increase, and from the viewpoint of production The length of the upper weld joint and the lower weld joint is preferably 2 m or less. In this example, the length of the upper weld joint and the lower weld joint is set to 0.5 m.

<Manufacturing method>
An example of the manufacturing method of the steel pipe column structure 1 is shown below.
FIG. 3 shows the manufacturing method of the circular steel pipe which comprises the steel pipe pillar structure 1, FIG. 3 (a) is explanatory drawing explaining the difference thickness steel plate 15 to be used, and its bending direction, FIG.3 (b). These are sectional drawings of the differential thickness steel plate 15 shown to Fig.3 (a).
In FIG. 3A, the L direction indicated by the arrow indicates the rolling direction, and the C direction indicates the rolling orthogonal direction.
As shown in FIG. 3, the differential thickness steel plate 15 used in the present embodiment is a steel plate (referred to as “CP steel plate” in the present specification) in which the plate thickness is changed in the rolling orthogonal direction (C direction).
The circular steel pipe of the present embodiment is manufactured by roll-forming the CP steel plate shown in FIG. 3 in the L direction to form an annular shape and welding the ends. The steel pipe column structure 1 is manufactured by stacking the circular steel pipes thus manufactured and joining the upper and lower thick welded joint portions by butt welding.
In addition, even if it is not a CP steel plate, you may manufacture the steel plate which has the same board thickness distribution by cutting a center part from a normal steel plate.

  In the steel pipe column structure 1 of the present embodiment, circular steel pipes (first circular steel pipe 1a to 18th circular steel pipe 1r) are stacked in the height direction on the foundation 3, and the ends of the circular steel pipes are butt welded. When joining and forming, the thickness of the welded joints at the top and bottom of each circular steel pipe is made thicker, and the other parts are made thinner than this, so the steel weight can be reduced and a rational design can be achieved. A steel pipe column structure is realized.

[Embodiment 2]
The second embodiment will be described with reference to FIGS.
As in the first embodiment, the steel pipe column structure 21 of the present embodiment is formed by stacking circular steel pipes (first circular steel pipe 21a to twentieth circular steel pipe 1t) on the foundation 3 in the height direction, and circular ends. It is formed by joining the parts by butt welding. Similarly to the first embodiment, the steel pipe column structure 21 of the present embodiment is also subject to fatigue due to repeated stress, and a predetermined plate thickness is required to ensure this strength from the relationship of fatigue strength. This is a steel pipe column structure.

The main difference between the steel pipe column structure 21 of the present embodiment and the steel pipe column structure of the first embodiment is that, in the first embodiment, the upper taper portion 7 and the lower taper portion 11 of the circular steel pipe are arranged on the outer surface side and the inner surface. However, in the steel pipe column structure 21 of the present embodiment, as shown in FIGS. 6 and 7, the tapered portion is a single taper provided only on the outer surface side of the circular steel pipe. is there. In addition, when providing a one side taper, you may make it provide in the inner surface side of a circular steel pipe.
As shown in FIG. 6, the portions of the circular steel pipe 21 a where the plate thickness changes are the upper weld joint portion 23, the upper piece taper portion 25, the thin portion 27, the lower piece taper portion 29, and the lower weld joint portion 31. .
As shown in FIG. 7, the differential thickness steel plate 33 used for manufacturing the circular steel pipe of the present embodiment is a CP steel plate whose thickness is changed in the rolling orthogonal direction (C direction). The differential thickness steel plate 33 is provided with a tapered surface only on one side thereof.

  Specific dimensions of the steel pipe column structure 21 of the present embodiment are as follows: the steel pipe diameter is 6000 mm, the height of each circular steel pipe constituting the steel pipe column structure 21 is 4 m, the upper weld joint portion 23 and the lower weld joint portion 31. The thickness of the upper welded joint portion 23 and the lower welded joint portion 31 is 0.5 m, the thickness of the thin portion 27 is 25 mm, and the thickness of the upper welded joint portion 23 and the lower welded joint portion 31 and the thinned portion 27 is The gradient is 1/100. By adopting such a specification, it is possible to make a part of the plate thickness thinner than the conventional plate thickness of 30 mm, and the steel weight is reduced by about 10%.

[Embodiment 3]
A third embodiment will be described with reference to FIGS.
As with the first and second embodiments, the steel pipe column structure 41 of the present embodiment also has a problem of fatigue due to repeated stress, and due to the relationship between fatigue strength, a predetermined plate thickness is required to secure this strength. It is a steel pipe column structure that is required.
The steel pipe column structure 41 of this embodiment is constructed by stacking octagonal steel pipes 41a, 41b,... Having an octagonal cross section in the axial direction and joining them by butt welding.
Each octagonal steel pipe forms eight octagonal steel plates in the circumferential direction by arranging eight 16m long steel plates in the circumferential direction, and the adjacent parts of the eight steel plates are welded in the height direction (the axial direction of the octagonal steel pipe). It is manufactured by. For this reason, each octagonal steel pipe has eight weld lines in the axial direction. However, since these weld lines are parts perpendicular to the axis of the steel pipe column structure, fatigue strength is not a problem. In addition, the parts where the plate thickness changes in the axial direction are welded to each other, and a gap is formed at the part where the plate thickness changes.However, since the amount of change in the plate thickness is small, Can be absorbed, so there is no problem.

As shown in FIG. 11, a steel plate constituting the octagonal steel pipe uses a differential thickness steel plate 53 (LP steel plate (Longitudinally Profiled Steel Plate)) whose thickness changes in the rolling direction (L direction).
As shown in FIG. 10, the thickness distribution of the LP steel sheet with a length of 16 m in the rolling direction is such that the upper weld joint 43 and the lower weld joint 51 at both ends have a length of 1 m, a plate thickness of 30 mm, an upper taper 45 and The length of the lower taper portion 49 is 1 m (plate thickness gradient 1/200), the length of the thin portion is 12 m, and the plate thickness is 25 mm.
As a result, the steel weight is reduced by about 14% from the cross section of the same thickness. Furthermore, the welded locations orthogonal to the steel pipe column axis are 16 m apart, which is less than in Example 1 and the prior art, and can be said to be a preferable design because the number of design critical sites can be reduced.

  In the first to third embodiments, the steel pipe column structures 1, 21, and 41 have the same pipe diameter in the height direction, but the present invention is not limited to this. For example, a mode in which the diameter on the lower side is increased and the pipe diameter is gradually decreased toward the upper side, or the pipe diameter is changed in the middle of the height direction may be employed.

[Embodiment 4]
A fourth embodiment will be described with reference to FIGS.
The fourth embodiment is an example in which a steel pipe column structure is applied to a bridge pier 61. In this example, the bridge pier 61 and the bridge girder 63 are integrated into a ramen structure, and the bending moment acting on the pier 61 is maximized at the upper part and the lower part (border part) of the pier 61. The upper end of the pier 61 is welded to the bridge girder 63, and the lower end of the pier 61 is welded to the gantry. The size of the pier is 20 m in height and a rectangular cross section, and the rectangular cross section is 2 m in the bridge axis direction (arrow A direction in FIG. 12) and 4 m in the bridge axis orthogonal direction (see FIG. 13). The distance between the two piers is 30m.
The bridge pier 61 of this embodiment is manufactured by arranging four steel plates having a length of 20 m in the circumferential direction to form a rectangular steel pipe and welding adjacent portions of the four steel plates. For this reason, although four weld lines can be made in the axial direction on the pier, the fatigue strength is not a problem because these weld lines are parts orthogonal to the axis of the steel pipe column structure.

As shown in FIG. 15, the steel plate constituting the rectangular steel pipe uses a differential thickness steel plate 67 (LP steel plate) whose thickness changes in the rolling direction (L direction).
As shown in FIG. 14, the thickness distribution of the difference thickness steel plate 67 with a length of 20 m in the rolling direction is as follows. The upper end weld joint portion 69 and the lower end weld joint portion 77 at both ends are 2 m in length and 30 mm thick, and the upper taper portion. 71 and the lower taper portion 75 have a length of 1 m (plate thickness gradient 1/200), the thin portion 73 has a length of 14 m and a plate thickness of 25 mm.
In the pier 61 of this embodiment, the steel weight is reduced by about 12% compared to the conventional example in which the plate thickness is equal.

[Embodiment 5]
The fifth embodiment will be described with reference to FIGS.
The fifth embodiment is an example in which a steel pipe column structure is applied to a bridge pier as in the fourth embodiment.
The main difference between the pier 81 of the present embodiment and the pier 61 of the fourth embodiment is that, in the fourth embodiment, the taper portion of the differential thickness steel plate 67 constituting the pier 61 is changed to the outer surface side of the differential thickness steel plate 67 and Although the difference thickness steel plate 83 of the present embodiment is provided on both inner surfaces, the taper portion is provided only on the outer surface side of the steel plate as shown in FIGS.

Specifically, the dimensions of the bridge pier 81 of the present embodiment are 20 m in height, 2 m in the bridge axis direction (arrow A direction in FIG. 16) in the rectangular cross section, and 4 m in the bridge axis orthogonal direction.
As shown in FIG. 18, the thickness distribution of the difference thickness steel plate 83 with a length of 20 m in the rolling direction is as follows. The upper end weld joint 85 and the lower end weld joint 93 are 2 m in length and 30 mm in thickness, and have an upper taper portion. 87 and the lower taper portion 91 have a length of 1 m (plate thickness gradient 1/200), the thin portion 89 has a length of 14 m and a plate thickness of 25 mm.
In the bridge pier 83 of the present embodiment, the steel weight is reduced by about 12% compared to the conventional example in which the plate thickness is equal.

[Embodiment 6]
Embodiment 6 will be described with reference to FIGS.
The sixth embodiment is an example in which a steel pipe column structure is applied to a bridge pier as in the fourth and fifth embodiments.
The pier 101 of the present embodiment is composed of a circular steel pipe having a height of 20 m and a diameter of 2500 mm.
The circular steel pipe is manufactured by bending a differential thickness steel pipe 103 having a thickness changed in the rolling direction (L direction) as shown in FIG. 23 in the rolling orthogonal direction (C direction). In this case, the length in the direction perpendicular to the rolling is 7850 mm (for the circumferential length of 2500 mm in diameter), but due to restrictions in steel plate manufacturing, it cannot be manufactured with one steel plate, A round steel pipe is manufactured by bending the steel sheets as a single steel sheet by welding the L directions together.

As shown in FIG. 22, the thickness distribution of the difference thickness steel plate 103 used in Embodiment 6 with a length of 20 m in the rolling direction is 1 m in length at the upper end weld joint portion 105 and the lower end weld joint portion 113 at both ends. The plate thickness is 25 mm, the length of the upper taper portion 107 and the lower taper portion 111 is 3 m (plate thickness gradient 1/300), the length of the thin portion is 12 m, and the plate thickness is 15 mm.
In the bridge pier 101 of this embodiment, the steel weight is reduced by about 30% compared to the conventional example in which the plate thickness is equal.

[Embodiment 7]
The seventh embodiment will be described with reference to FIGS.
In the seventh embodiment, the steel pipe column structure of the present invention is applied to the offshore structure 115.
As shown in FIGS. 28 and 29, the offshore structure 115 according to the seventh embodiment includes three connecting portions 119 that connect the three leg portions 117 standing in the sea and the upper end portions of the three leg portions 117. And a marine tower portion 121 erected on the connecting portion 119 material.
The three leg portions 117 and the offshore tower portion 121 are formed by stacking a plurality of steel pipes having thick portions at both ends in the tube axis direction and welding the thick portions to each other (hereinafter referred to as “main”). The steel pipe column according to the invention ”).

  As shown in the offshore structure 115 of the present embodiment, the steel pipe column structure of the present invention may use a plurality of steel pipe columns according to the present invention, or may be connected to a part of the structure. A steel pipe column according to the present invention may be coupled with the portion 119 interposed. That is, the steel pipe column structure of the present invention only needs to have the steel pipe column according to the present invention as a part of the structure portion.

[Embodiment 8]
The eighth embodiment will be described with reference to FIG.
A steel pipe column structure 123 according to the eighth embodiment includes a vertical steel pipe column 125 erected on a foundation 122 (ground), and a horizontal steel pipe column 127 joined in the middle in the height direction of the vertical steel pipe column 125. And is configured.
A steel pipe column according to the present invention is applied to the vertical steel pipe column 125 and the horizontal steel pipe column 127.
The vertical steel pipe column 125 is a cantilever having a lower end fixed to a foundation 122 (ground) and an upper portion free. Further, the horizontal steel pipe column 127 can also be regarded as a cantilever beam when the connection portion with the vertical steel pipe column 125 is considered as a fixed end.

Since the joint portion of the vertical steel pipe column 125 with the horizontal steel pipe column 127 has a large acting stress, the plate thickness in the vicinity of the connection portion is increased. In this case, the thickness of the circular or rectangular steel pipe disposed at the joint with the horizontal steel pipe column 127 may be thicker at the connection with the horizontal steel pipe column 127 than at the weld joint. Thus, even if the plate thickness of some circular or rectangular steel pipes constituting the vertical steel pipe column 125 in relation to the joining with other members is not a steel pipe having thick portions at both ends, The vertical steel pipe column 125 is included in the steel pipe column according to the present invention.
Further, with respect to the horizontal steel pipe column 127, the base portion, that is, the joint portion with the vertical steel pipe column 125 has a large acting stress, so that the plate thickness is increased. On the other hand, in the part away from the base, the acting stress is small, but only the welded part with a low weld fatigue strength grade is made thick.

  In addition, as to which part of the welded joint portion having a weld surface orthogonal to the axial direction in the steel pipe column structure is to be thicker than other parts, the use of the steel pipe column structure, for example, a steel chimney And the bridge main tower, wind power generation tower, marine structure, architectural structure, bridge structure, and the like.

DESCRIPTION OF SYMBOLS 1 Steel pipe pillar structure 1a 1st round steel pipe 1b 2nd round steel pipe 1k 11th round steel pipe 1r 18th round steel pipe 3 Foundation 5 Upper thick part 7 Upper taper part 9 Thin wall part 11 Lower taper part 13 Lower thick part 15 Difference Thick steel plate 21 Steel pipe column structure 21a 1st circular steel pipe 21b 2nd circular steel pipe 21c 3rd circular steel pipe 21s 19th circular steel pipe 21t 20th circular steel pipe 23 Upper weld joint part 25 Upper piece taper part 27 Thin part 29 Lower piece taper part 31 Lower Welded Joint Part 33 Differential Thickness Steel Plate 41 Steel Pipe Column Structure 41a First Octagonal Steel Pipe 41b Second Octagonal Steel Pipe 43 Upper Welded Joint Part 45 Upper Tapered Part 47 Thin Wall Part 49 Lower Tapered Part 51 Lower Welded Joint Part 53 Differential Thickness Steel plate 61 Bridge pier 63 Bridge girder 65 Mount 67 Differential thickness steel plate 69 Upper end weld joint 71 Upper taper part 73 Thin wall part 75 Lower taper part 77 Lower end weld joint part 81 Bridge Leg 83 Differential thickness steel plate 85 Upper end weld joint 87 Upper taper portion 89 Thin wall portion 91 Lower taper portion 93 Lower end weld joint portion 101 Bottom pier 103 Differential thickness steel plate 105 Upper end weld joint portion 107 Upper taper portion 109 Thin wall portion 111 Lower taper portion 113 Lower end Welded joint 115 Marine structure 117 Leg 119 Connection part 121 Marine tower part 123 Steel pipe pillar structure 122 Foundation 125 Vertical steel pipe pillar 127 Horizontal steel pipe pillar

Claims (5)

A steel pipe column structure that supports a windmill used for wind power generation,
Thick wall portions of each steel pipe having thick wall portions at both ends and having a plurality of steel pipes arranged so as to be stacked in the direction of the pipe axis, and welded joint portions joining the thick wall portions of the respective steel pipes Is set to the plate thickness determined from the fatigue strength of the welded portion, and the portion other than the welded portion is set to the plate thickness determined from the fatigue strength of the base metal in general, and the fatigue strength of the steel pipe column structure as a whole is constant Steel tube pillar structure characterized by   The difference between the thickness of the thick portion and the other portion in the steel pipe is 4 mm or less, and the inclined portion where the thickness gradually changes between the thick portion and the other portion. The steel pipe column structure according to claim 1, wherein a thickness gradient at the inclined portion is set to 1/100 or less.   The steel pipe pillar structure according to claim 1 or 2, wherein an axial length of the thick part is set to 2 m or less. It is a manufacturing method of the steel pipe pillar structure in any one of Claims 1 thru | or 3, Comprising: Both ends of a rolling orthogonal direction are formed in the thick wall determined from the fatigue strength of a welding part, and parts other than the said welding part are mother. It features a steel pipe manufacturing process for manufacturing steel pipes by annularly forming a steel plate set to a thickness determined from the general fatigue strength of the material, and a steel pipe joining process for stacking the manufactured steel pipes and welding them together. Manufacturing method of steel pipe column structure. It is a manufacturing method of the steel pipe pillar structure in any one of Claims 1 thru | or 3, Comprising: Both ends of a rolling direction are formed in the thickness decided from the fatigue strength of a welding part, and parts other than the said welding part are base materials. A steel pipe manufacturing process in which a plurality of steel plates set to a thickness determined by general fatigue strength are arranged in the circumferential direction and adjacent steel plates are welded together to produce a steel pipe, and steel pipe joining in which the manufactured steel pipes are stacked and welded together The manufacturing method of the steel pipe pillar structure characterized by including the process.