JP2001055712A - Structure for reinforcing fatigue crack at horizontal girder connection of steel bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength of a horizontal girder connection by attaching a predetermined reinforcing material to the horizontal girder connection by means of a high tension bolt, when a lower flange of a horizontal girder and a lower flange of a main girder are not arranged at the same height. SOLUTION: A horizontal girder 12 formed of upper and lower flanges 12a and a web 12b extends in an orthogonal direction to the longitudinal direction of a bridge. The lower flange 12a is set to a hither location than a lower flange 11a of a main girder 21, and a connection which is a junction between the girder 12 and the main girder 11, is formed by welding the upper and lower flanges 12a and the web 12b onto a web 11b of the girder 11. In the connection of the horizontal girder, a reinforcing material 20 for directly transferring a force of the lower flange 12a to the lower flange 11a is fixed to the bridge concerned by means of a high tension bolt 30. By virtue of this reinforcing structure, the force of the lower flange 12a is directly transferred to the lower flange 11a by means of the reinforcing material 20 and the bolt 30, and therefore a force transferred from the girder 12 to the main girder web 11b can be drastically reduced. Thus, fatigue crack at the horizontal girder connection, stemming from the welded portion can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for reinforcing a fatigue crack in a connection part of a cross beam of a steel bridge.

[0002]

2. Description of the Related Art In a bridge, as shown in FIGS. 5 and 6, a cross beam 12 orthogonal to the main beam 11 is provided between a plurality of main beams 11 supported on an abutment via a bearing 10. There are various types of connecting portions (lateral girder connections) of the horizontal girder 12 to the main girder 11 such as a type that allows the main girder web to penetrate and a type that does not penetrate the main girder web. If not, the cross beam 12 is welded to the main beam web 11b. Reference numeral 13 denotes a weld. In this case, as shown in FIG. 7, in a long-term use, a fatigue crack 14 may be generated from a welded portion near both ends of the horizontal beam lower flange 12a at the horizontal beam connection. Conventionally, as a reinforcing measure against the fatigue crack, as shown in FIG.
Is sandwiched between the reinforcing members 15 from above and below and fastened with high-strength bolts 30, and the reinforcing members 15 are fastened to the web 11 b of the main girder 11 with high-strength bolts 30.
A force is applied to the web 11b of the main girder 11 from the
The concentration of the force on the weld near the end of the lower flange 12a was reduced.

[0003]

However, since the out-of-plane rigidity of the web of the main girder is low, in the conventional structure, fatigue cracks from the welded portion of the lower flange of the horizontal girder to the main girder web at the connection part of the horizontal girder. The problem was not completely solved.
An object of the present invention is to provide a reinforcing structure for a fatigue crack in a horizontal girder joint portion of a steel bridge, which can fundamentally solve the problem of a fatigue crack from a welded portion in the horizontal girder joint portion.

[0004]

The present invention which achieves the above object of the present invention is as follows. When the lower flange of the cross beam is not at the same height position as the lower flange of the main beam, the cross beam of the steel bridge to which the reinforcing material that transmits the force of the lower beam of the cross beam to the lower flange of the main beam is attached with high strength bolts. Reinforcement structure for fatigue cracks at the joint.

[0005] In the reinforcing structure for fatigue cracks in the connection part of the girder of the steel bridge of the present invention, the force of the lower flange of the girder is transmitted to the lower flange of the main girder by the reinforcing material and the high-strength bolt. The force conventionally applied to the main girder from the girder connection is reduced, and the problem of fatigue cracks from the weld at the girder connection can be drastically solved. Also, since the main girder lower flange has high rigidity in the out-of-plane direction of the main girder web, even if the force of the horizontal girder lower flange is transmitted to the main girder lower flange, the main girder web has the same surface as the conventional main girder web. The problem of fatigue cracking in the welded portion of the horizontal girder joint due to low external rigidity does not occur or hardly occurs. In addition, since the reinforcement is fixed to the existing bridge by high-strength bolts, it is possible to avoid welding the reinforcement directly to the current bridge, and to prevent fatigue cracks that may newly occur in the case of welding.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 4, a structure for reinforcing a fatigue crack in a lateral girder joint of a steel bridge according to an embodiment of the present invention will be described. 1 and 2 show a first embodiment of the present invention.
3 and 4 show a second embodiment of the present invention. Portions common to all embodiments of the present invention are denoted by the same reference numerals throughout all embodiments of the present invention.

First, portions common to all embodiments of the present invention will be described with reference to FIGS. 1 and 2 (and FIG. 5 of a conventional example). The steel main girder 11 is installed on an abutment via a bearing (a shoe), and the floor slab is installed on the main girder 11. The bearings are designed to reliably transmit the load transmitted from the superstructure (girder) to the substructure (abutment, pier) and to ensure safety against changes due to earthquake, wind, temperature change, and live load. You.

The main girder 11 extends in the longitudinal direction of the bridge and includes upper and lower flanges 11a and a web 11b. A sole plate is fixed to the lower surface of the lower flange 11a of the main girder 11 by fillet welding or the like. The sole plate is the main girder 1
When the load is transmitted from 1 to the bearing, the flow of force is smoothed, and the stress concentration is reduced.

The cross beam 12 extends in a direction orthogonal to the longitudinal direction of the bridge, and includes upper and lower flanges 12a and webs 12b.
The lower flange 12a of the cross beam 12 is not at the same height position as the lower flange 11a of the main beam 11, but at a position higher than the lower flange 11a of the main beam 11. The horizontal girder 12 penetrates the web 11b of the main girder 11 and does not penetrate the web 11b.
Some stop at the site. The connecting portion (joint portion) of the horizontal girder 12 with the main girder 11 has upper and lower flanges 12 a and a web 12 b welded to the web 11 b of the main girder 11.

At or near the cross beam joint, a reinforcing member 20 for directly transmitting the force of the cross beam lower flange 12a to the main girder lower flange 11a and a high-strength bolt 30 (mainly friction is generated by tightening the high-strength bolt). A bolt that transmits power by force) is provided. The stiffener 20 is not welded to the existing bridge,
It is fixed to the existing bridge by high strength bolts 30.

Next, the operation of the parts common to all the embodiments of the present invention will be described. In the above-described structure for reinforcing fatigue cracks in the connection part of the girder of the steel bridge of the present invention, the force of the lower girder lower flange 12 a is directly transmitted to the main girder lower flange 11 a by the reinforcing member 20 and the high-strength bolt 30. Therefore, the force transmitted from the cross girder 12 to the main girder web 11b is greatly reduced, and it is possible to suppress the occurrence of fatigue cracks from the welded portion of the conventional girder connection to the main girder web. Further, since the main girder lower flange 11a has high rigidity in the out-of-plane direction of the main girder web 11b, the force of the horizontal girder lower flange 12a is applied to the main girder lower flange 11a.
a, the problem of fatigue cracking in the welded portion of the horizontal girder joint due to the low out-of-plane rigidity of the main girder web as in the conventional main girder web 11b does not occur or hardly occurs.

In addition, since the reinforcing member 20 is fixed to the existing bridge by the high-strength bolts 30 and reinforced, it is possible to avoid directly welding the reinforcing member 20 to the current bridge, and to directly weld the reinforcing member 20 to the current bridge. This prevents the occurrence of fatigue cracks from new welds that may newly occur.

Next, parts unique to each embodiment of the present invention will be described. In the first embodiment of the present invention, as shown in FIGS. 1 and 2, a stiffener 21,
The countermeasure against fatigue of the horizontal girder connection part is carried out by using No.3. The reinforcing member 20 is made of a steel material having an H-shaped cross section (for example, an H-shaped steel).
2a, the upper flange 20a of the reinforcing member 20 in close contact with the lower surface.
Is fixed to the lower side flange 12a of the cross beam by the high-strength bolt 30. The web 20b of the reinforcing member 20 is concentrically located just below the cross beam web 12b. The lower flange 20a of the reinforcing member 20 is at the same height position as the main girder lower flange 11a,
The end of the lower flange 20a of the reinforcing member 20 faces the end of the main girder lower flange 11a. Above and below the lower flange 20a and the main girder lower flange 11a of the reinforcement 20,
The attachment plate 22 is attached to both the lower flange 20a and the main girder lower flange 11a.
2 and lower flange 20 of reinforcement 20 sandwiched therebetween
a is tightened by the high-strength bolt 30,
The upper and lower attachment plates 22 and the main girder lower flange 11 a sandwiched therebetween are tightened by high-strength bolts 30. Thus, the lower flange 20a of the reinforcing member 20 and the lower flange 11a of the main girder are connected to the upper and lower attachment plates 22 by the high-strength bolts 30.

The stiffener 21 is made of a single plate extending in a direction perpendicular to the main girder web 11b. The stiffener 21 is located between the reinforcing member 20 and the main girder web 11b, and the horizontal girder lower flange 12a and the main girder lower flange 11a. And placed between. The stiffener 21 is arranged concentrically with the web 20 b of the reinforcing member 20, and an end of the stiffener 21 faces an end of the web 20 b of the reinforcing member 20. On both sides of the web 20b and the stiffener 21 of the reinforcing member 20, an adhering plate 23 is in contact with both the web 20b and the stiffener 21 of the reinforcing member 20. 2 of reinforcement 20 sandwiched between
0b is tightened by the high-strength bolt 30, and the attachment plates 23 on both sides and the stiffener 2
1 is fastened by a high-strength bolt 30. As a result, the web 20b of the reinforcing member 20 and the stiffener 21 are connected to the attachment plates 23 on both sides by the high-strength bolts 30. The end face of the stiffener 21 on the side opposite to the reinforcement 20 is the main girder web 1.
1b, the main girder web 11b is stiffened by preventing the main girder web 11b from being deformed in an out-of-plane direction. The stiffener 21 is also provided on the web 11b of the main girder 11 on the lower flange 11a.
Is not welded.

The operation of the first embodiment of the present invention is as follows. Most of the force of the cross girder lower flange 12a is transmitted to the upper flange of the reinforcing member 20, further transmitted to the lower flange 20a of the reinforcing member 20 via the reinforcing material web 20b, and added from the lower flange 20a of the reinforcing member 20. The power is transmitted to the main girder lower flange 11 a via the contact plate 22. Therefore,
The force transmitted from the cross beam 12 to the main girder web 11b is reduced, and the occurrence of cracks from the welded portion of the cross girder 12 with the main girder web 11b is suppressed. Further, since the stiffening plate 21 is provided, the out-of-plane rigidity of the main girder web 11b is also improved, and the generation of cracks from the welded portion of the horizontal girder 12 with the main girder web 11b is further suppressed.

In the second embodiment of the present invention, as shown in FIG. 3 and FIG. I have. The stiffener 21 of the first embodiment is not provided in the second embodiment. Reinforcing material 20
Is made of a steel material having an H-shaped cross section (for example, an H-shaped steel), and the upper flange 20a of the reinforcing member 20 is brought into close contact with the lower surface of the lower beam 12a, and the upper flange 20a of the reinforcing member 20 is raised to the lower flange 12a of the horizontal beam. It is fixed by a force bolt 30. The web 20b of the reinforcing member 20 is concentrically located just below the cross beam web 12b. Lower flange 20a of reinforcing material 20
Are cut out by the amount of extension of the main girder lower flange 11a so as not to interfere with the main girder lower flange 11a. The lower flange 20a of the reinforcing member 20 is a lower flange 11a of the main girder.
And the lower flange 20a of the reinforcing member 20
Is opposed to the end of the main girder lower flange 11a.
Lower flange 20a of reinforcing member 20 and lower flange 11a of main girder
Above and below, the attachment plate 24 is in contact with both the lower flange 20a of the reinforcing member 20 and the main girder lower flange 11a, and the lower and upper attachment plates 24 and the lower portion of the reinforcing member 20 sandwiched therebetween are attached. The flange 20 a is fastened by the high-strength bolt 30, and the upper and lower attachment plates 24 and the main girder lower flange 11 a sandwiched therebetween are fastened by the high-strength bolt 30. Thus, the lower flange 20a of the reinforcing member 20 and the lower flange 11a of the main girder are connected by the upper and lower attachment plates 24 and the high-strength bolts 30.

The attachment plate 25 is made of, for example, an angle iron. One side of the attachment plate 25 is welded to the end of the reinforcing member 20 on the side facing the main girder web 11b. The other side of the attachment plate 25 extends in parallel with the main girder web 11b and extends in a direction perpendicular to the web 20b of the reinforcing member 20, and is arranged in close contact with the main girder web 11b (however, the main girder web is provided). 1
1b is not welded). The other side of the attachment plate 25 is fastened to the main girder web 11b by a high-strength bolt 30.
Accordingly, the attachment plate 25 stiffens the main girder web 11b while preventing the main girder web 11b from being deformed in an out-of-plane direction.

The operation of the second embodiment of the present invention is as follows. Most of the force of the cross girder lower flange 12 is transmitted to the upper flange 20 of the reinforcing member 20, further transmitted to the lower flange 20a of the reinforcing member 20 via the web 20b of the reinforcing member 20, and from the lower flange 20a of the reinforcing member 20. It is transmitted to the main girder lower flange 11a via the attachment plate 24. Therefore,
The force transmitted from the cross beam 12 to the main girder web 11b is reduced, and the occurrence of cracks from the welded portion of the cross girder 12 with the main girder web 11b is suppressed. Further, since the attachment plate 25 is provided, the out-of-plane rigidity of the main girder web 11b is also improved, and the occurrence of cracks from the welded portion of the horizontal girder 12 with the main girder web 11b is further suppressed.

[0019]

According to the reinforcing structure for fatigue cracks in the connection part of the girder of the steel bridge according to the first aspect, the force of the lower flange of the girder is transmitted to the lower flange of the main girder by the reinforcing material and the high-strength bolt. Therefore, the force conventionally applied to the main girder web from the horizontal girder connection portion is reduced, and the problem of fatigue cracks from the welded portion in the horizontal girder connection portion can be drastically solved. Also, since the main girder lower flange has high rigidity in the out-of-plane direction of the main girder web, even if the force of the horizontal girder lower flange is transmitted to the main girder lower flange, the main girder web has the same surface as the conventional main girder web. The problem of fatigue cracking in the welded portion of the horizontal girder joint due to low external rigidity does not occur or hardly occurs. In addition, since the reinforcement is fixed to the existing bridge by high-strength bolts, it is possible to avoid welding the reinforcement directly to the current bridge, and to prevent fatigue cracks that may newly occur in the case of welding.

[Brief description of the drawings]

FIG. 1 is a side view of a part of a steel bridge of a reinforcing structure for a fatigue crack in a lateral girder connection part of a steel bridge according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view in a direction orthogonal to FIG. 1 of a structure for reinforcing a fatigue crack in a lateral girder connection part of a steel bridge according to the first embodiment of the present invention.

FIG. 3 is a side view of a part of a steel bridge in a structure for reinforcing a fatigue crack in a lateral girder connection part of the steel bridge according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view in a direction orthogonal to FIG. 1 of a structure for reinforcing a fatigue crack in a lateral girder connection part of a steel bridge according to a second embodiment of the present invention.

FIG. 5 is a plan view showing an arrangement of a main girder and a cross girder of a conventional steel bridge.

FIG. 6 is a cross-sectional view of a connection part of a cross beam of a conventional steel bridge.

FIG. 7 is a side view of a part of the lateral girder connection viewed in a direction orthogonal to FIG. 6, and is a side view of a part of the steel bridge showing crack generation from a weld.

FIG. 8 is a side view of a part of a conventional steel bridge having a crack prevention structure.

[Explanation of symbols]

 Reference Signs List 11 main girder 11a main girder upper and lower flanges 11b main girder web 12 horizontal girder 12a horizontal girder upper and lower flanges 12b horizontal girder web 20 reinforcing material 21 stiffener 22, 23, 24, 25 attachment plate 30 high strength bolt

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Nagashima 5-9, Yonbancho, Chiyoda-ku, Tokyo Topy Industries Co., Ltd. (72) Inventor Hiroki Harada 5-9, Yonbancho, Chiyoda-ku, Tokyo Topy Industries Co., Ltd. F-term (reference) 2D059 AA07 CC05 GG01 GG40 GG55

Claims (1)

[Claims] 1. A steel to which a reinforcing member for transmitting the force of the lower girder flange to the lower flange of the main girder is attached by a high-strength bolt when the lower flange of the cross girder is not at the same height position as the lower flange of the main girder. Reinforcement structure for fatigue cracks in the bridge girder connection.