JPS5944405A - Bridge vibration preventing apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a vibration damping device for a bridge.

When the wind hits a bridge, it depends on its cross-sectional shape.

Vortex-excited vibrations and flutter vibrations caused by Karman vortices.

Gear lopping vibration, etc. may occur.

It poses a danger to vehicles and people passing by, and in some cases, there is a risk that the clan school may be damaged due to destruction.

Among these vibration phenomena, gearropping vibration occurs as the angle between the wind direction 5 and the horizontal plane 4 of the bridge 1, which has a box-shaped cross section, increases, as the angle of attack 6 increases. This occurs when the lift cuff that receives the wind in an upward direction perpendicular to the wind is smaller due to the difference in the separation of the wind that occurs on the upper surface of the bridge, that is, the upper subgrade plate 2 and the lower surface 3.

Conventionally, a typical device for suppressing gear roping vibrations is a center barrier 9, which is a vertical plate provided in the center of an upper subgrade plate 2 of a bridge 1, as shown in FIG.

However, the center barrier 9 changes the separation state of the flow on the upper subgrade plate 2 of the bridge 1, causing the flow to increase as the angle of attack 6 increases as shown in FIG. 1, and suppresses gear lopping vibration. However, this increases the force that the bridge 1 receives in the direction of the wind flow, that is, the drag force 8, and it becomes necessary to increase the design strength of the bridge 1, such as by increasing the plate thickness. Moreover, the center barrier 9 also obstructs the view of vehicles and pedestrians passing through the bridge 1, which is not preferable.

The present invention was created in view of the above circumstances, and is a compact and simple device for damping gear-ropping vibrations that does not obstruct the view of vehicles and pedestrians passing on the bridge, and does not increase the drag force that the bridge receives from the wind. The purpose is to provide

Therefore, the bridge vibration damping device of the present invention can be applied to both sides of the lower part of a box-shaped bridge having an upper subgrade plate on the upper part.

It is characterized by a flat plate protruding horizontally at a certain distance from the lower end surface.

Below, a bridge vibration damping device as an embodiment of the present invention will be explained with reference to the drawings. Fig. 3 is a sectional view showing a bridge equipped with a damping device. A code is attached.

As shown in the figure, a flat plate 10 is provided on the lower side surface 11 of the bridge 1 protruding from the lower end surface at a slight height.

Others are the same as before.

Next, its effects will be explained.

The flow at the bottom of the bridge 1 flows between the flat plate 10 and the lower side surface 11 of the bridge.
By fixing the vortex at the corner formed by the vortex, the separation condition at the lower surface 3 of the bridge changes, and a flow is created in which the lift cuff increases with the increase in the angle of attack 6. This results in
Gearropping vibration will no longer occur.

Since the flat plate 10 is mounted so as to protrude horizontally, there is almost no increase in the drag force 8 as in the conventional case.

As a result of experiments, the optimum mounting position of the flat plate 10 is preferably a position upward from the lower end surface of the bridge 1 by the protruding length of the flat plate 10, but it may be slightly shifted vertically. The results of the experiment are shown in FIG.

When the protruding length of the flat plate 10 is measured and the mounting position is measured from the bottom end of the bridge 1 and H is the wind speed at which vibration occurs, it is expressed as the L/H ratio.

It was confirmed that when L/H=1, the oscillation wind speed was ~, and no vibration occurred.

As described above, according to the bridge vibration damping device of the present invention, gearlopping vibration can be distributed without obstructing the view of vehicles and pedestrians passing through the bridge, and without increasing the drag force that the bridge receives from the wind.

The advantage is that bridge safety is greatly improved.

[Brief explanation of drawings]

Figures 1 and 2 are sectional views showing a conventional bridge, Figure 3 is a sectional view showing a bridge equipped with an allocation device as an embodiment of the present invention, and Figure 4 is a graph showing the effects of the present invention. . 1...Bridge, 2...Upper road plate, 3...Bottom surface, 10
...Flat plate, 11... Lower side. 1st mouth 2nd rice 3 prongs 3

Claims (1)

[Claims] A bridge vibration damping device characterized by having flat plates protruding horizontally at a certain distance from the lower end surface on both sides of the lower part of a box-shaped cross-section bridge with an upper subgrade plate on the upper part.