JP7162649B2 - Seismic reinforcement method for steel structures - Google Patents

Description

The present invention relates to a seismic reinforcement construction method for steel structures.

For example, a boiler steel frame (steel frame structure) installed in a thermal power plant comprises a plurality of columns, a plurality of beams, and a plurality of braces arranged obliquely between the columns and beams. . Braces include vertical braces and horizontal braces. A vertical brace indicates a brace installed in a vertical plane, and a horizontal brace indicates a brace installed in a horizontal plane. Henceforth, the term "brace" in this specification indicates a vertical brace. Since the boiler body is suspended from the ceiling beam of the boiler steel frame, the weight of the boiler body acts on the brace as a compressive load. In existing boiler steel frames, for example, braces made of H-shaped steel are attached, but in recent years, as part of seismic reinforcement work, work has been carried out to replace these braces with new damper structures (see Patent Document 1). ing. Because braces are fixed to columns or beams with multiple bolts via gusset plates, conventional seismic reinforcement work involves removing multiple bolts, removing the braces, and then installing a new damper structure. was used.

Japanese Patent No. 5216050

However, in existing boiler steel frames, the boiler body is suspended, and a large compressive load is applied to the braces, so it is often difficult to remove the multiple bolts that secure the braces. Moreover, when some bolts are removed, the remaining bolts are subjected to a large shearing force, so there is a possibility that some of the remaining bolts may break during the brace replacement work. Therefore, in the conventional seismic reinforcement work, the setup for ensuring the safety of the work becomes large-scale, and there is a problem that the work efficiency decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and its object is to provide a construction method capable of safely and efficiently performing seismic reinforcement work for existing steel structures.

In order to achieve the above object, a representative aspect of the present invention includes a plurality of columns extending in a vertical direction, a plurality of beams extending horizontally between the plurality of columns, and the plurality of columns and the plurality of columns. A seismic reinforcement construction method for a steel frame structure comprising a plurality of braces arranged obliquely between beams, and a first step of lifting the braces with a lifting member; and a third step of removing the brace melted in the second step and attaching a new damper structure.

ADVANTAGE OF THE INVENTION According to this invention, the seismic reinforcement work of the existing steel-frame structure can be performed safely and efficiently. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

The perspective view which shows schematic structure of a boiler steel frame. The figure which shows the detail of the A section of FIG. FIG. 2 is a model diagram showing changes in the point of application of axial force and changes in the amount of deformation of the brace due to fusing of the brace. The perspective view which shows the detailed structure of a brace. VV sectional view of FIG. The flowchart which shows the procedure of seismic reinforcement work of a boiler steel frame. The figure which shows the fusion|melting preparation stage of a brace. The figure which shows the fusion cutting procedure of a brace (flange). The figure which shows the state which melted the upper half of a brace (flange). The figure which shows the procedure which opens the cut end of a brace (flange) by fusion cutting (Case 1). The figure which shows the procedure which opens the cut end of a brace (flange) by fusion cutting (case 2). The figure which shows the fusion cutting procedure of a brace (web) (when a compressive load is small). The figure which shows the fusion cutting procedure of a brace (web) (when a compressive load is large). The figure which shows the procedure which melt-cuts a brace (flange) using two melters.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing a schematic configuration of a boiler steel frame 1. FIG. As shown in FIG. 1, a boiler steel frame (steel structure) 1 includes a plurality of columns 2 extending in the vertical direction, a plurality of beams 3 extending horizontally between the columns 2, and a plurality of columns 2 and a plurality of braces 4 obliquely arranged between the plurality of beams 3. A boiler steel frame 1 is installed, for example, in a thermal power plant. A boiler body (not shown) is suspended from the boiler steel frame 1, and the weight of the boiler body is supported by the columns 2, beams 3, and braces 4 of the boiler steel frame 1 (see FIG. 2).

Brace 4 made of H-shaped steel is used in the existing boiler steel frame 1, and construction is being carried out to replace the brace 4 with a damper structure in order to reinforce the boiler steel frame 1 against earthquakes. In this seismic reinforcement work, the seismic reinforcement construction method according to the present invention will be used. As the damper structure, for example, a hysteretic damper structure described in Patent Document 1 can be used.

FIG. 2 is a diagram showing details of part A in FIG. In FIG. 2, the white arrow indicates the direction of the load. As described above, since the boiler body is suspended from the existing boiler steel frame 1, the column 2 and the brace 4 receive a compressive load in the direction of the white arrow. In the present embodiment, a method of fusing the brace 4 is used when replacing the brace 4 with a damper structure. Note that "fusion cutting" is a cutting technique for heating and cutting metal, and in this embodiment, gas cutting, arc cutting, gasoline cutting, etc. can be applied.

When the brace 4 is fused, the brace 4 bends and deforms as a result of the fuse. This will be explained in detail using FIG. FIG. 3 is a model diagram showing changes in the point of application of the axial force and changes in the amount of deformation of the brace 4a due to fusing of the brace 4a shown in FIG. FIG. 3(a) shows the brace 4a before fusing. As shown in FIG. 3(a), a compressive load is applied in the direction of the white arrow to the central portion (fusing position B) of the brace 4a in the longitudinal direction. FIG. 3(b) is an enlarged view of the left half of the brace 4a shown in FIG. 3(a). As shown in FIG. 3(b), before the brace 4a is fused, the point P of application of the compressive load is located on the center line CL of the brace 4a.

Since the compressive load acts on the cross-sectional center of the brace 4a, if the fused position B of the brace 4a is slightly fused from above as shown in FIG. Move down. As a result, the brace 4a is bent downward and deformed, and the center line of the brace 4a is deformed from the center line CL to the center line CL1. The difference between the center line CL before deformation and the center line CL1 after deformation is the amount of deformation of the brace 4a.

When the brace 4a is fused further, as shown in FIG. 3(d), the point P of application of the compressive load moves further downward, and the bending deformation of the brace 4a increases. If, as shown in FIG. 3(e), the brace 4a is fused only from the upper side, the point P of application of the compressive load moves to the lower end in the height direction of the brace 4a. It turns out to be even bigger. On the other hand, as shown in FIG. 3(e), the bending deformation of the brace 4a is smaller than that in FIG. 3(e).

In this way, when the brace 4a is fused at the fusing position B, if one half of the brace 4a in the height direction (upper side) is fused and then the remaining half is fused from the other side (lower side), the brace 4a is fused. Bending deformation in can be suppressed.

Next, the structure of the brace 4 attached to the existing boiler steel frame 1 will be described. 4 is a perspective view showing the detailed structure of the brace, and FIG. 5 is a cross-sectional view taken along line VV of FIG. As shown in FIG. 4, the brace 4 is obliquely attached between the column 2 and the beam 3 via the gusset plate 5. As shown in FIG. 5, the brace 4 is made of H-section steel having a pair of flanges (a first flange 11 and a second flange 12) and a web 13 connecting the pair of flanges 11 and 12. As shown in FIG. The brace 4 is arranged so that the pair of flanges 11 , 12 are parallel to the plane formed by the column 2 and the beam 3 . That is, the pair of flanges 11 and 12 are attached in an upright state. The brace 4 and the gusset plate 5 are fixed with a plurality of bolts 8 .

In order to remove the brace 4 from the gusset plate 5, all of the multiple bolts 8 must be removed. However, since a large compressive load is applied to the brace 4 as described above, it is not easy to remove the bolt 8 . Therefore, in this embodiment, a method of removing the brace 4 by removing the bolt 8 after the brace 4 is fused is adopted.

Next, a seismic reinforcement construction method for a steel frame structure according to an embodiment of the present invention will be described. FIG. 6 is a flow chart showing the seismic reinforcement work procedure for the boiler steel frame 1 .

In performing the seismic reinforcement work of the boiler steel frame 1, first, the worker attaches the lug 7 to the web 13 of the brace 4 by welding, and attaches the lug 6 to the beam 3 located above the brace 4 by welding (Work 1). . Then, the worker attaches the chain block (suspension member) 20 using the lugs 6 and 7 and lifts the brace 4 (operation 2/first step). FIG. 7 shows the state after these works 1 and 2 have been performed. That is, FIG. 7 is a diagram showing the preparation stage for fusing the brace 4. As shown in FIG. The member (device) for lifting the brace 4 is not limited to the chain block 20, and any lifting means may be used.

Next, the worker fuses the fused position B of the brace 4 while lifting the brace 4 (operation 3/second step). A procedure for fusing the brace 4 will be described in detail with reference to FIGS. 8 to 13. FIG. First, the operator fuses the upper half 11a of the first flange 11 of the brace 4 (FIG. 8(a)).

The reason why the upper half 11a of the first flange 11 is fused earlier than the lower half 11b is as follows. That is, when the brace 4 is fused from above, the brace 4 tends to bend downward as shown in FIGS. 3(c) and 3(d). However, as shown in FIG. 7, since the brace 4 is lifted by the chain block 20, the downward bending deformation of the brace 4 is restrained. Therefore, when the brace 4 is fused from above, the brace 4 can be fused safely and efficiently while suppressing downward bending deformation of the brace 4 . This is the reason why it is preferable to fuse the upper half 11a of the first flange 11 before the lower half 11b.

Next, the worker fuses the upper half 12a of the second flange 12 (FIG. 8(b)). 9 shows a state in which the upper half 11a of the first flange 11 and the upper half 12a of the second flange 12 are fused.

Here, the boiler steel frame 1 installed in the thermal power plant is very large, and for example, the length of the braces 4 is about 10 m or longer. Therefore, when the flange 11 (upper half 11a) or the flange 12 (upper half 12a) is fused at the fused position B as shown in FIG. may close. Therefore, in this embodiment, when the flanges 11 and 12 are fused, a fused opening method is used so that the cut ends 15 are not closed. In the following, two cases will be described in detail with reference to FIG. 10 and FIG. Note that FIG. 11 is a diagram showing a procedure different from that of FIG.

(Case 1)
10A and 10B are diagrams showing a procedure for opening the cut end 15 of the brace 4 (flanges 11 and 12) by fusing. As shown in FIG. 10(a), first, the operator forms cuts 15a in the flanges 11 and 12 by fusion cutting. Next, as shown in FIG. 10(b), the operator fuses and cuts the cut 15a so as to expand the required maximum width in the longitudinal direction of the brace 4 (horizontal direction in FIG. 10) to form a cut 15b. Next, as shown in FIG. 10(c), the operator forms a cut 15c by fusion cutting in the same manner as the cut 15a. Next, as shown in FIG. 10(d), the operator fuses the cut 15c so as to expand it in the longitudinal direction of the brace to form a cut 15d.

By repeating this procedure, a cut edge 15e as shown in FIG. 10(e) is formed. In addition, although the shape of the cut end in FIG. 10 is an inverted triangle (▽) shape, it may be an inverted trapezoid shape. As a result, the incision 15 is prevented from closing due to the compressive load acting on the brace 4 in the axial direction, and the fusing operation of the brace 4 can be performed efficiently.

(Case 2)
11A and 11B are diagrams showing a procedure for opening the cut end 15 of the brace 4 (flanges 11 and 12) by fusing. As shown in FIG. 11(a), first, the operator forms an inverted trapezoidal cut 15k in the flanges 11 and 12 by fusion cutting. Next, as shown in FIG. 11(b), the operator fuses the cut 15k so as to expand it in the longitudinal direction of the brace 4 (horizontal direction in FIG. 11) to form a cut 15l. Next, as shown in FIG. 11(c), the operator fuses the cut 15l so as to expand it in the longitudinal direction of the brace 4 to form a cut 15m. By repeating this procedure, a large incision 15n is formed as shown in FIG. 11(d). As a result, the incision 15 is prevented from closing due to the compressive load acting on the brace 4 in the axial direction, and the fusing operation of the brace 4 can be performed efficiently.

Returning to FIG. 8, the operator fuses the lower half 11b of the first flange 11 (FIG. 8(c)) and fuses the lower half 12b of the second flange 12 (FIG. 8(d)). Fusing of the flanges 11 and 12 is completed by the work shown in FIGS. 8(a) to (d). In FIG. 8, after the lower half 11b of the first flange 11 is fused, the lower half 12b of the second flange 12 is fused, but this order may be reversed. That is, if the upper halves 11a and 12a of the flanges 11 and 12 are fused first and then the lower halves 11b and 12b of the flanges 11 and 12 are fused, the lower halves 11b and 12b can be fused in any order.

Next, a procedure for fusing the web 13 of the brace 4 will be described. 12A and 12B are diagrams showing the procedure for fusing the web 13. FIG. When the compressive load acting on the braces 4 is not so large, the web 13 is fused only in one direction, as shown in FIG. That is, as shown in FIGS. 12(a) to 12(e), the web 13 can be finally melted by cutting the web 13a to the web 13d in order from one direction (the right side in FIG. 12). .

Further, when the compressive load acting on the brace 4 is large, the web 13 is greatly deformed due to fusing. Therefore, the web 13 may be fused according to the fuse-cutting procedure as shown in FIG. That is, as shown in FIGS. 13A to 13E, the web 13 is fused in half (13a, 13b) from one direction (the right side in FIG. 13) in the width direction, and then the web 13 is cut in the other direction (the right side in FIG. The remaining half (13c, 13d) is fused from the left side of 13). In this way, by alternately cutting the web 13 in the width direction, the deformation of the web 13 can be minimized, so that the cutting work can be performed safely and efficiently.

When the bracing work for the brace 4 is completed in this way, as shown in FIG. 6, the worker removes the bolts 8 fixed to the gusset plate 5 and removes the brace 4 which has been separated in half. Then, if a newly prepared damper structure is installed in place of the brace 4, the seismic reinforcement work for the boiler steel frame 1 is completed (operation 4/third step). Here, the brace 4 is fused and the compressive load acting on the brace 4 is released, so the bolt 8 can be removed safely and easily.

As described above, according to the seismic reinforcement construction method according to the present embodiment, the central portion (fusion cutting position B) of the brace 4 in the longitudinal direction is fused, so that the fused work can be performed safely and efficiently. If the brace 4 is fused except for the central portion in the longitudinal direction, the bending deformation of the brace 4 due to fuse-cutting increases, impairing the workability and safety of the fuse-cutting work, which is not preferable.

In addition, in this embodiment, after the brace 4 is lifted by the chain block 20, the upper halves 11a and 12a of the flanges 11 and 12 of the brace 4 are melted first, so bending deformation accompanying the melt-cutting of the brace 4 does not occur. Suppressed. As a result, the fusing work can be performed more safely and efficiently.

Further, by fusing the brace 4 so as to expand the cut 15, it is possible to prevent the cut 15 from closing due to the compressive load acting on the brace 4 in the brace axial direction. As a result, the fusing work can be performed more efficiently.

In addition, depending on the magnitude of the compressive load acting on the brace 4, the web 13 can be fused only in one direction or fused alternately in one direction and the other direction. It can be done more efficiently.

The present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention. Subject to invention. Although the above embodiments show preferred examples, those skilled in the art can realize various alternatives, modifications, variations or improvements from the contents disclosed in this specification, These are included in the technical scope described in the appended claims.

For example, if two fusing machines can be prepared, the fusing work can be performed more efficiently. In FIG. 8, the upper half 11a of the first flange 11 and the upper half 12a of the second flange 12 are fused simultaneously, followed by the lower halves 11b and 12b. 13 is fused from both sides (first example). Moreover, FIG. 14 shows the procedure for fusing the flanges 11 and 12 using two fusing machines showing the second example. As shown in FIG. 14, the upper half 11a and the lower half 11b of the first flange 11 are simultaneously fused by two fusers (FIG. 14(a)). After the first flange 11 is fused, the upper half 12a and the lower half 12b of the second flange 12 are simultaneously fused (Fig. 14(b)). Then, the remaining web 13 is fused by the above method. Also by this construction method, bending deformation of the brace 4 can be suppressed, and the brace 4 can be fused and cut safely and efficiently. Moreover, according to this construction method, the work process is halved compared to work using a single cutting machine, so there is an advantage that the construction period for seismic reinforcement work can be shortened.

1 Boiler steel frame (steel structure)
2 Column 3 Beam 4 Brace 5 Gusset Plate 6,7 Lug 8 Bolt 11 First Flange 11a Top Half of First Flange 11b Bottom Half of First Flange 12 Second Flange 12a Top Half of Second Flange 12b Bottom of Second Flange Half 13 Web 15 Cut 20 Chain block (hanging member)

Claims (8)

a plurality of columns extending in a vertical direction, a plurality of beams extending horizontally between the plurality of columns, and a plurality of braces arranged obliquely between the plurality of columns and the plurality of beams; A seismic reinforcement method for a steel structure comprising
a first step of lifting the brace with a lifting member;
a second step of fusing the central portion in the longitudinal direction of the brace lifted in the first step;
and a third step of removing the brace fused in the second step and attaching a new damper structure. In the seismic reinforcement construction method for the steel structure according to claim 1,
The brace consists of an H-section steel with a web connecting a first flange and a second flange, the first flange and the second flange being parallel to the plane formed by the column and the beam. are arranged as
In the second step,
First, the half above the web of the first flange is fused,
Then, the half of the second flange above the web is fused;
Then, the lower half of the web of one of the first flange and the second flange is fused,
A seismic reinforcement construction method for a steel frame structure, wherein the lower half of the web of the other of the first flange and the second flange is then fused. In the seismic reinforcement construction method for the steel structure according to claim 1,
The brace consists of an H-section steel with a web connecting a first flange and a second flange, the first flange and the second flange being parallel to the plane formed by the column and the beam. are arranged as
In the second step,
First, the upper sides of the first and second flanges sandwiching the web of the first and second flanges are fused simultaneously,
A seismic reinforcement construction method for a steel frame structure characterized by simultaneously fusing the lower sides of the first and second flanges sandwiching the web of the first and second flanges. In the seismic reinforcement construction method for the steel structure according to claim 1,
The brace consists of an H-section steel with a web connecting a first flange and a second flange, the first flange and the second flange being parallel to the plane formed by the column and the beam. are arranged as
In the second step,
First, the upper and lower halves of the first flange are simultaneously fused across the web,
Next, a seismic reinforcement construction method for a steel frame structure, wherein the upper half and the lower half of the second flange are fused at the same time with the web interposed therebetween. In the steel structure seismic reinforcement method according to any one of claims 2 to 4,
In the second step, the first flange and the second flange are fused so that the cut ends of the first flange and the second flange expand in the longitudinal direction of the brace. reinforcement method. In the steel structure seismic reinforcement method according to any one of claims 2 to 5,
In the second step, after the first flange and the second flange are fused, the web is fused from one direction in the width direction. In the steel structure seismic reinforcement method according to any one of claims 2 to 5,
In the second step, after the first flange and the second flange are fused, the web is alternately fused in one direction and the other in the width direction. In the steel structure seismic reinforcement method according to any one of claims 1 to 7,
The steel structure is a boiler steel frame for supporting the boiler body,
A seismic reinforcement construction method for a steel frame structure, wherein the first step, the second step, and the third step are performed in a state in which the boiler body is suspended from the boiler steel frame.

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