JP2000192422A - Wind-resistant bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the weight of a sheet-metal girder, and to improve the wind resistance of a bridge by forming a corner cut preventing separation at the lower end of the girder of a wind having a speed component in the bridge-axial orthogonal direction at the lower end of the girder. SOLUTION: A sheet-metal girder is formed in a corner cut shape by a flange under one girder and a corner cut 10, the shape of a sectional corner angle is changed slightly and a fluid pattern in the periphery of a cross section is altered largely, and aerodynamic characteristics are stabilized. Since a flow separated from the first separation point of a bridge girder collides with the next separation point and a separating flow is generated anew even from the next separation point at that time, both flows interfere. The separating flows are brought near to sectional side faces by an interference, and the generation of large separation is prevented and a harmful vibrations are damped. According to the bridge girder, the installation of the corner cuts 10 such as the installation of a fairing and the installation of a plate is made unnecessary, and the weight of the girder is lightened. Consequently, the corner cuts 10 are formed at the lower flange of the sheet-plate girder and vibrations are damped, and the weight of the girder is lightened and an economical design can be conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wind-resistant bridge capable of improving the wind resistance of a bridge (particularly an I-girder bridge).

[0002]

2. Description of the Related Art In the construction of suspension bridges and cable-stayed bridges, it is expected to adopt an I-girder structure used in general bridges from the viewpoint of cost reduction.

In the case of a suspension structure represented by a suspension bridge or a cable-stayed bridge, wind resistance often becomes a problem. Phenomena caused by the wind include flutter that causes divergent vibration at a high wind speed, and vortex excitation that occurs at a relatively low wind speed. As measures to prevent such vibrations, there are methods of increasing the torsional rigidity of the girders, changing the fairing shape as shown in FIG. 11, and installing dampers. Broadly speaking, it can be divided into the following methods. (Japan Road Association, Road Bridge Wind Resistant Design Handbook
p. 143 July 1991)

Increasing the rigidity of the bridge girder Increasing the weight of the bridge girder Method of changing the aerodynamic force caused by wind (change in cross-sectional shape) Method of increasing damping (by installing a damper)

Unlike the conventional truss girder and box girder, the I-girder has a low torsional rigidity and, from the viewpoint of economy, a method of improving the wind resistance by changing the cross-sectional shape is often adopted. There is a method of installing rings, flaps, side plates, etc. (Excerpt from Figure 6: Handbook of Road Bridge Wind Design p. 144-149. In addition, Kawasaki Heavy Industries Technical Report 1)
No. 13, April 1992).

[0006]

However, the prior art has the following problems.

In the method of installing corner cuts such as fairings and flaps, the girder weight is increased, so that the diameter of the cable supporting the girder, the rigidity of the main tower, and the rigidity of the base of the main tower are increased, resulting in an economical problem. Problems arise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of measures for stabilizing wind resistance, and it is an object of the present invention to provide a wind-resistant bridge which efficiently improves wind resistance without increasing the weight of a girder as much as possible. With the goal.

[0009]

SUMMARY OF THE INVENTION The present invention has the following arrangement to solve the above-mentioned problems. The gist of the invention according to claim 1 is that in a wind-resistant bridge having a bridge girder composed of a plurality of sheet girders, wind having a velocity component in a direction perpendicular to the bridge axis separates at the lower end of the sheet girder. A wind-resistant bridge characterized by the formation of corner cuts for preventing wind. The gist of the invention described in claim 2 is that the corner cut is provided at an edge of the lower end flange of the sheet girder at the width center side of the flange, and has a substantially L-shaped or substantially concave cross section. A wind-resistant bridge according to claim 1. The gist of the invention according to claim 3 resides in a wind-resistant bridge according to claim 2, wherein a side surface of the corner cut has a step shape.
The gist of the invention according to claim 4 is the wind-resistant bridge according to any one of claims 1 to 3, wherein the bottom of the corner cut changes in height toward the center of the width. The gist of the invention described in claim 5 is that the corner cut is provided outside the sheet girder.
Existing in the wind-resistant bridge described in any of the above. The gist of the invention according to claim 6 resides in the wind-resistant bridge according to any one of claims 1 to 5, wherein the corner cut has an I-shaped cross section. The gist of the invention according to claim 7 is that the corner cut is
The wind-resistant bridge according to any one of claims 1 to 6, wherein the bridge is provided below the sheet girder. The gist of the invention described in claim 8 is that the corner cut is made of a steel plate.
Existing in the wind-resistant bridge described in any of the above. The gist of the invention according to claim 9 resides in the wind-resistant bridge according to any one of claims 1 to 8, wherein the corner cut also serves as a guide rail for an inspection vehicle.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. The bridge girder of the wind-resistant bridge B according to the present embodiment includes a bridge girder composed of a plurality of I-girders as shown in FIG. A corner cut 10 is formed at the edge of the flange at the lower end of the I-girder, which is a kind of sheet girder, on the center side of the width. The corner cut 10 is formed in a concave shape with a thin cross section, and is formed continuously in the bridge axis direction. The corner cut 10 having such a shape is dimensioned so that a human can walk so that it can be used as a management road. Corner cut 10
It is necessary to block the flow of air with a member such as a steel plate. In the present embodiment, all are formed of steel plates. The corner cuts 10 are joined by a suitable method such as welding or bolting.

The wind-resistant bridge B (bridge girder) according to the present embodiment is configured as described above, and has the following effects.

A corner cut shape is formed by the I-girder lower flange and the corner cut 10. The corner cut shape can stabilize the aerodynamic characteristics by slightly changing the shape of the corner portion of the cross section and largely changing the fluid pattern around the cross section as one of measures against the rectangular cross section. FIGS. 5 and 6 show changes in the flow pattern depending on the corner cut shape. Corner cut 1
In the wind-resistant bridge B having no zero, the wind in the direction perpendicular to the bridge axis separates on the lower surface of the bridge girder as shown in FIG. 5, so that the bridge girder vibrates. However, in the wind-resistant bridge B (bridge girder) according to the present embodiment, the flow separated from the first separation point (point a in the figure) hits the next separation point (point b in the figure), but is also newly added from the point b. Since a separated flow occurs, the two interfere. Due to this interference, the separation flow approaches the side surface of the cross section, and does not cause large separation as in the case of no countermeasure,
Harmful vibration can be suppressed. Such action
The effect has been confirmed by wind tunnel experiments when corner cuts are formed on the pier (literature: Shiraishi, Matsumoto et al., Aerodynamic stabilization effect of rectangular cross section by corner cut, wind engineering symposium 1986).

Further, according to the bridge girder, since the management path for inspection, for which installation is indispensable, is actively used,
Corner cutting 10 such as setting of fairing and setting of plate
Need not be installed. Therefore, it is possible to reduce the weight of the girder, and it is possible to design economically.

In the present embodiment, the shape is as described above, but the present invention is not limited to this, and can be applied to a shape suitable for applying the present invention.

For example, the corner cut 2 of the windproof bridge B shown in FIG.
Numeral 0 is a structure in which a portion hidden by the I-girder of the management road side member from the I-girder is removed, and the I-girder and the management road portion are connected by welding. This facilitates inspection of the inside of the I-girder and repair work on the surface.

Further, as shown in a corner cut 30 shown in FIG. 3, one side of the concave shape can be formed in a step shape. This example has a structure in which the management road is stepped when the amount of protrusion of the management road is large. Even in the case of a stepped shape, suppression of vibration can be expected due to interference of separation flows from a plurality of separation points, similarly to the corner cut shape. The step-like shape facilitates inspection of the inside of the I-girder and repair work on the surface.

Further, as in a corner cut 40 shown in FIG. 4, the base of the concave shape can be inclined. In this embodiment, a slope is provided on the bottom of the management road in the second embodiment, and the inside of the girder on the side of the management road is made of a wire mesh. By providing the slope, a structure that facilitates drainage while maintaining the corner cut shape is obtained, and a structure excellent in rust prevention of the management path is obtained.

Further, as shown in FIGS. 7 and 8, the lower flange of the I-shaped beam is formed so that the edge on the center side of the width extends downward.
It can also be keyed. The portions (reference numerals 50 and 60) extending vertically downward are corner cuts.

The corner cuts 70, shown in FIGS.
A structure in which the lower flange of the sheet girder is bent in a hook shape toward the center of the width, as in the case of 80, in other words, a structure in which the lower flange of the I-girder is moved to the center of the width is also conceivable.

Further, the present invention can be applied to a case where a plurality of girders are provided in the width direction.

Further, the number, position, shape, etc. of the above-mentioned constituent members are not limited to the above-mentioned embodiment, but can be set to a suitable number, position, shape, etc. for carrying out the present invention.

The I-girder bridge shown in FIG.
It consists of two I digits I1 and I2. The inspection vehicle rails R1 and R2 are installed outside I1 and I2, respectively, and the inspection vehicle rails R1 and R2 are used to form corner cuts 90 that interfere with the separation of the inspection vehicle rail and the separation of the I-beams I1 and I2.
The height of R2 (RH in the figure) is lower than the height of the I digit (IH in the figure). A part of the base of the inspection car rails R1 and R2 is embedded in a PC floor slab, and is joined by a suitable stopper such as a stud. Note that I shown in FIG.
As for the effect of the girder bridge (wind flow in the width direction), as shown in FIG. 15, separation can be suppressed as compared with FIG.

The girder cross section shown in FIG. 13 is the same as the I-girder bridge shown in FIG. The method of supporting the inspection vehicle rails R1, R2 is different, and the bases of the inspection vehicle rails R1, R2 are joined to the lower surface of the upper flange of the main girder. Therefore, the upper flange of the main girder is longer than the lower flange. By arranging the inspection car rails R1 and R2, which are indispensable for inspection, at appropriate positions and also serving as corner cuts 100, harmful vibrations can be eliminated without adding a new member like a conventional wind-resistant stabilizing member. It becomes possible to suppress. Therefore, economical design is possible without increasing the weight of the girder.

The corner cut 110 shown in FIG. 14 is manufactured on a steel plate provided on the lower surface of the lower flange of the main girder. Here, the inspection vehicle rails R1, R2 are installed below the lower flange of the main girder.

In each of the drawings, the same components are denoted by the same reference numerals.

[0026]

Since the present invention is configured as described above, the following effects can be obtained. Since corner cuts are formed in the lower flange of the sheet girder, harmful vibration can be suppressed. In addition, it is also possible that the corner cut also serves as the management path, and in such a case, it is not necessary to add a new member for vibration isolation. Therefore, according to the present invention, economical design is possible without increasing the weight of the girder.

[Brief description of the drawings]

FIG. 1 is a front view of a wind-resistant bridge according to an embodiment of the present invention.

FIG. 2 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 3 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 4 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 5 is a visible view of a wind flow in a windproof bridge without corner cuts.

FIG. 6 is a visible view of a wind flow in the windproof bridge shown in FIG. 1;

FIG. 7 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 8 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 9 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 10 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 11 is a conceptual front view of a windproof means according to the related art.

FIG. 12 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 13 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 14 is a front view of a windproof bridge according to another embodiment of the present invention.

FIG. 15 is a visible view of a wind flow showing the effect of the wind-resistant bridge shown in FIG. 12;

[Explanation of symbols]

B Wind-resistant bridge I1, I2 I-girder S Floor slab R1, R2 Inspection car rail 10, 20, 30, 40, 50, 60, 70, 80, 9
0,100,110 corner cut

Claims (9)

[Claims] 1. A wind-resistant bridge having a bridge girder composed of a plurality of sheet girders, wherein a corner having a velocity component in a direction perpendicular to a bridge axis is prevented from separating at a lower end of the sheet girder at a lower end of the sheet girder. A wind-resistant bridge characterized by the formation of. 2. The method according to claim 1, wherein the corner cut is provided at an edge of the flange at the lower end of the sheet girder at the center of the width, and has a substantially L-shaped or substantially concave cross section. Wind-resistant bridge. 3. The wind-resistant bridge according to claim 2, wherein the side surface of the corner cut has a stepped shape. 4. The wind-resistant bridge according to claim 1, wherein the bottom of the corner cut changes in height toward the center of the width. 5. The wind-resistant bridge according to claim 1, wherein the corner cut is provided outside the sheet girder. 6. The wind-resistant bridge according to claim 1, wherein the corner cut has an I-shaped cross section. 7. The wind-resistant bridge according to claim 1, wherein the corner cut is provided below the sheet girder. 8. The wind-resistant bridge according to claim 1, wherein the corner cut is made of a steel plate. 9. The wind-resistant bridge according to claim 1, wherein the corner cut also serves as a guide rail for an inspection vehicle.