JPH0424485B2 - - Google Patents

Description

[Detailed description of the invention]

In a truss structure suspension bridge, as shown in Figure 1, a truss structure stiffening girder b is attached to a hanger rope c to a main cable a stretched between main towers (not shown).
A floor plate e is supported on the stiffening girder b via a girder d, and gratings f are provided near the median strip and on the sides of the floor plate e. In such bridges, flutter vibrations generally occur, and there is a risk of the bridge collapsing due to destruction. Conventionally, as a method of suppressing this flutter vibration or increasing the wind speed at which vibration begins to occur,
As shown in Fig. 2, a stabilizer g is installed on the median strip of the floor plate e over almost its entire length in the longitudinal direction, and as shown in Fig. 3, a stabilizer g is installed below the grating f of the median strip with a mid-height cross section. It has been proposed that a member h is installed. However, when the stabilizer g is installed as shown in Figure 2, the height of the stabilizer g is
Approximately 1.5m is required, and installing this over almost the entire length of the median strip will spoil the beauty of the suspension bridge.
Not only do they obstruct the view of cars and pedestrians passing through the suspension bridge, but because they are installed almost perpendicular to the direction of the wind, the air resistance of the entire suspension bridge increases. In addition, as shown in Fig. 3, a member h with a medium-high cross-sectional shape
When installed, the length of each side needs to be about 1.5m, and if it is installed in the longitudinal direction of the suspension bridge, the weight will increase considerably. As the air resistance of the suspension bridge increases and the weight increases, the strength of the suspension bridge must be improved, which increases construction costs. The present invention was proposed to solve these problems, and consists of arranging a plurality of girders extending in the axial direction of the bridge on a truss structure formed with the main structure arranged at the four corners. In the cross section of a bridge with floor plates mounted on the same girder, one edge of the main structure touches the upper main structure, and the other edge protrudes toward the bridge axis, so that the flat plate does not overlap with the edge of the floor plate. This invention relates to a bridge equipped with a flutter prevention device, which is characterized in that it is provided within a range. In the present invention, as described above, among the main structures arranged at the four corners of the truss structure of the bridge cross section, one edge is in contact with the upper main structure and the other edge is protruding toward the bridge axis. It was placed in a range that did not overlap with the edge of the floor plate, which was placed on multiple girders extending in the axial direction of the bridge installed in a row on the truss structure, so it was placed between the upper main structure and the floor plate. By means of a flat plate,
The angle of the flow hitting the front edge of the floor plate becomes smaller than when the flat plate is not provided, and the separation state of the flow changes,
The wind speed at which flutter vibrations occur will increase, greatly improving bridge safety. Moreover, since the flat plate is arranged almost parallel to the flow, there is almost no increase in air resistance, and installation is easy, and the flat plate does not obstruct the view of cars and pedestrians passing on the suspension bridge. The present invention has many advantages. The present invention will be described below with reference to the illustrated embodiments. 1 is a truss-structured stiffening girder suspended from a main cable 2 stretched between the main towers via a hanger rope 3, and a girder 4 extending in the bridge axis direction is installed on the stiffening girder 1. A floorboard 5 is mounted on the floorboard 5. Among the main structures 6 disposed at the four corners of the truss structure, a horizontal flat plate 7 extending in the bridge axis direction is interposed between the upper main structure 6 and the floor plate 5, and one end of the flat plate 7 is interposed between the upper main structure 6 and the floor plate 5. The edge contacts the upper main structure 6, and the other edge protrudes toward the bridge axis, and is disposed within a range that does not overlap the floorboard 5 in the vertical direction. Since the illustrated embodiment is constructed as described above, the flat plate 7 disposed between the main structure 6 and the floor plate 5
The angle of the flow hitting the front edge of the floor plate 5 is equal to that of the flat plate 7.
is smaller than when not provided, the flow separation state changes, the wind speed at which flutter vibration occurs increases, and the safety of the bridge improves. Next, an experimental example of a conventional bridge without the flat plate 7 and a bridge according to the present invention provided with the flat plate 7 will be given. FIG. 6 shows a cross section of a conventional bridge model without the flat plate 7, and FIG. 7 shows a cross section of a bridge model according to the present invention with the flat plate 7 provided, under the conditions shown in Table 1 below. An experiment was conducted and the experimental results shown in FIG. 5 were obtained.

[Table] In Figure 5, curve A is the angle of attack (angle of inclination of the entire bridge)
0°, curve B shows the experimental results of the cross section of a conventional bridge without a flat plate 7 shown in Figure 6 when the angle of attack is 3°, curve C shows the experimental results when the angle of attack is 0°, and curve D when the angle of attack is 3°. FIG. 7 shows experimental results of a cross section of a bridge according to the present invention equipped with a flat plate 7 shown in FIG. According to the above experimental results, the wind speed at which vibration occurs in the cross section of a conventional bridge is 48.5 m/s at 0° and 36 m/s at an angle of attack of 3°.
The wind speed at which vibration occurs in the cross section of the bridge according to the present invention is 96 m/s at an angle of attack of 0° and 100.5 m/s at an angle of attack of 3°. Therefore, it has been found that the vibration-generating wind speed of the bridge cross section according to the present invention is approximately twice as high as that of the conventional bridge cross section. Although the present invention has been described above with reference to embodiments, the present invention is, of course, not limited to such embodiments, and can be modified in various ways without departing from the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a bridge to which the present invention is applied;
2 and 3 are longitudinal cross-sectional views of a bridge equipped with a conventional flutter prevention device, respectively, and FIG. 4 is a vertical cross-section showing an embodiment of a bridge equipped with a flutter prevention device according to the present invention. Figure 5 is a chart showing the experimental results of the bridge according to the present invention and a conventional bridge, and Figures 6 and 7 are graphs showing the results of the experiment of the conventional bridge used in the above experiment and the bridge according to the present invention, respectively. It is a longitudinal cross-sectional view of each model. 1... Stiffening girder, 4... Girder, 5... Floor board, 6...
Main structure, 7... flat plate.

Claims (1)

[Claims] 1. In the cross section of a bridge where a plurality of girders extending in the bridge axis direction are installed in a row on a truss structure formed with the main structure arranged at the four corners, and the floor plate is mounted on the girder, the main structure is One edge touches the upper main structure,
1. A bridge equipped with a flutter prevention device, characterized in that a flat plate whose other edge protrudes toward the bridge axis is provided in a range that does not overlap the edge of the floor plate.