JPH0432884B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of Application of the Invention] The present invention relates to a windproof and vibration isolating device for long square structures such as main towers and girders such as suspension bridges and cable-stayed bridges.

[Technical Background of the Invention] Long angular structures such as main towers and girders of suspension bridges, cable-stayed bridges, etc. have low rigidity and tend to be easily affected by wind action. Furthermore, since these structures are generally corner-shaped structures, they are susceptible to wind dynamic effects such as vortex excitation vibration due to Karman vortices generated from the corners and gear locking caused by separation of airflow from the corners. It often bothers me.

Measures to deal with these dynamic effects of wind include: (a) Increase the rigidity of the structure (b) Improving the damping performance of structures (c) Make the shape of the structure aerodynamically good and so on.

The method of increasing the rigidity of the structure in (a) is to increase the wind speed at which vortex-excited vibrations and gearropping occur, but if we focus too much on rigidity,
The steel weight may increase, resulting in uneconomic results.

The means to improve damping performance (b) is effective for damping dynamic effects of wind such as vortex-excited vibration and gearropping, but it is important to secure a place to install the damping device and to ensure reliability when using it for a long time. Problems remain in terms of performance and maintenance.

As a means of achieving an aerodynamically favorable shape in (c), proposals include making the structure's cross section streamlined, installing gratings (ventilation), installing flow guide plates, and installing a center barrier. has been done.

In particular, the method of attaching flow guide plates to the corners of a structure's cross section has the advantage that it does not depend on changing the basic cross section of the structure and does not cause cross-sectional defects like grating, and is a promising wind resistance measure. It is attracting attention as

A flow guide plate for the purpose of isolating the dynamic effects of wind such as vortex-excited vibration and gearropping in a square structure has already been published in Publications No. 52-7071 and Publication No. 7071 of the Utility Model Publication.
Several proposals have been made, as seen in Publication No. 58-53288, but these methods do not necessarily work effectively, as will be explained later, and are not particularly effective against the occurrence of gear locking, and are effective against gear locking. To counter this, the measures to increase the rigidity of the structure described in section (a) above are also used.

As an example of a corner structure, when assuming a cross section as shown in Figure 1, in such a cross section, when the period of the Karman vortex generated from the corner and the natural frequency of the structure match, The structure has a problem in that resonance, specifically vortex-excited vibration, occurs in a direction perpendicular to the direction of the wind, and as the wind speed further increases, gearlopping occurs due to separation of the airflow from the corners.

This will be explained using the results of wind tunnel experiments for structures. Figure 7 shows the wind resistance response of a rectangular structure without a flow guide plate as shown in Figure 1, that is, the V-A curve, which shows the relationship between the dimensionless amplitude A/D and the converted wind speed V/NηD. It shows. Here the wind speed, Nη
is the bending frequency, D is the width of the structure, and A is the amplitude of the structure.

As is clear from Figure 7, the converted wind speed V/
When NηD = 8 to 9, a large amplitude vortex excitation vibration with a dimensionless amplitude A/D > 0.17 is generated, and the converted wind speed V/NηD ≧
13, and the response vibration exhibits aerodynamically unstable behavior with A/D > 0.17.

Figure 2 shows a structure in which flat flow guide plates are arranged at the corners of the plane parallel to the direction of the wind indicated by arrows with a required gap, and the corresponding V-A curve is shown as Shown in Figure 8. This structure, as shown in Figure 8,
Dimensionless amplitude A/D near converted wind speed V/NηD=7.4
＞0.17 is generated, and in the region of converted wind speed V/NηD ≥ 33, the response amplitude A/D becomes ＞0.17 due to gearing, and the vortex excitation vibration with a large vibration amplitude of Although the wind speed range in which vibrations occur in the structure shown in Figure 1 has been reduced, it is still insufficient as a wind-resistant and vibration-proof device.

[Prior art and its problems] In order to solve these problems, in the past,
As mentioned above, Utility Model Publication No. 7071, Utility Model Publication No. 58-
As seen in Publication No. 53288, etc., the corner of the angular structure shown in Figure 3 has a structure that is parallel to two planes parallel to the direction of the wind and expands outward with respect to the other two planes. It has been proposed that a flow guide plate is provided with a rectangular cross-sectional shape.

Fig. 9 is the V-A curve of the structure shown in Fig. 3, and as is clear from Fig. 9, the vortex excitation vibration seen in Figs. 7 and 8 has disappeared. , gear locking occurs in the range of converted wind speed V/NηD≧22, resulting in large-amplitude vibration with dimensionless amplitude A/D>0.17, which is insufficient as a wind-resistant and vibration-proofing device.

The purpose of the present invention was made in view of the above circumstances, and it is an object of the present invention to solve the problems of the prior art by simple yet rational means, and to solve the problems of the prior art by simple but rational means. It is an object of the present invention to provide a windproof and vibration isolating device that can be used in a structure, reasonably prevents not only vortex-excited vibration, but also the gallop phenomenon, and is highly economically effective.

[Means for Solving the Problems] The configuration of the present invention that solves the problems of the prior art is to create a required ventilation flow in the longitudinal direction of the corner of a square structure such as the main tower or girder of a suspension bridge or cable-stayed bridge. In a wind and vibration isolation device for a structure in which a flow guide plate with an arcuate cross-sectional shape is arranged through a road gap, the center point of the arc of the flow guide plate is set relative to the central angle of the corner of the corner structure. On the other hand, the tangential direction of one end of the current guide plate is parallel to one side 1a of the square structure, and the tangential direction of the other end of the current guide plate is set at an acute angle θ so that the surface 1a is It is made by diagonally intersecting the line passing through it.

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. 4, 5, 6, and 10. FIG. 4 is a front view of the cable-stayed bridge, FIG. 5 is a sectional view of the main tower, which is a square structure, and FIG. 6 is a reference diagram shown for explaining FIG. 5.

As shown in Fig. 4, 1 is a main tower consisting of an angular structure with right-angled diagonals, 2 is a bridge girder, 3 is a cable-stayed cable, and 4
is a pier. The windproof and anti-vibration device shown in FIG. 5 will be explained. Flow guide plates 5 having an arcuate cross-section are attached to all corners of the main tower 1 with predetermined gaps therebetween. One of the tangential directions of the arcuate end of the flow guide plate 5 is parallel to the plane 1a in the airflow direction indicated by the arrow, and the tangential direction of the other arcuate end is on the inner side of the cross section with respect to the plane 1a in the airflow direction. facing the direction.

The center point 0 ₁ of the circle relative to the arc is not located at a symmetrical position with respect to the plane 1a in the airflow direction and the plane 1b in the perpendicular direction to the airflow, as shown in Fig. 5, but as shown in Fig. 5. , are arranged slightly eccentrically toward the plane 1b in the direction perpendicular to the air flow, so that the air passage between the flow guide plate 5 and the main tower 1 is prevented from suddenly decreasing at the corner of the cross section. Furthermore, by making the center points 0 _{and 1} of the circle eccentric, the arc-shaped flow guide plate 5 can fully extend to the inner side of the cross section of the main tower 1, and the tangential direction of the arc end is as shown in FIG. So, plane 1 in the airflow direction
Instead of being perpendicular to a, as shown in the figure, θ<
Consideration is given to making it 90° (acute angle) so that the flow guide plate 5 can easily guide the wind.

FIG. 10 is a wind resistance response diagram (VA curve) when the flow guide plate according to the present invention as shown in FIG. 5 is applied. As is clear from this Figure 10,
In the full range of equivalent wind speeds from 0 to 50, the occurrence of vortex excitation vibration and gearroping, which are observed in the case of the conventional flow guide plate described above, is not observed at all, indicating aerodynamically stable properties. Figure 10 is a response diagram when the angle of attack α = 0°, but wind tunnel tests have shown that it is aerodynamically stable at angles of attack α = 5°, 10°, and 20°. Confirmed by.

[Effects of the Invention] As described above, according to the configuration of the present invention, the following effects can be obtained.

(a) As is clear from the V-A curve diagram in Figure 10, it has a far more vibration-proofing effect than conventional wind-resistant and vibration-proof devices, and because the cross-sectional shape of the flow guide plate is arc-shaped, , wind direction (angle of attack or horizontal declination)
The anti-vibration effect can be effectively exerted over a wide range of changes in vibration.

(b) Furthermore, since the shape is a part of a circle (arc), it is easy to manufacture, implement and manage, and has excellent features such as being economically effective. As shown in FIG. 4, it is preferable that the flow guide plate of the present invention be attached to an area of 1/3 or more of the main tower structure.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the cross-sectional shape of the angular structure;
Figures 2 and 3 are cross-sectional views of conventional wind and vibration isolators;
The figure is a front view of a cable-stayed bridge showing the installed state of the windproof and vibration isolating device of the present invention, FIG. 5 is a sectional view of the main part, and FIG. 6 is shown to explain the device of the present invention shown in FIG. Reference explanatory drawings, Fig. 7 is a V-A curve diagram showing the wind tunnel test results of the angular structure in Fig. 1, Fig. 8 is a V-A curve diagram corresponding to the angular structure in Fig. 2, and Fig. 9 The figure is a V-A curve diagram corresponding to the angular structure shown in FIG. 3, and FIG. 10 is a V-A curve diagram corresponding to the angular structure of the present invention shown in FIG.
It is an A curve diagram. 1... Main tower, 1a... Main tower surface in the airflow direction, 1b
...Main tower surface in the direction perpendicular to the airflow, 5...Difficult plate.

Claims (1)

[Claims] 1. A flow guide plate having an arcuate cross-sectional shape is installed in the longitudinal direction of the corner of a corner structure such as the main tower or girder of a suspension bridge or cable-stayed bridge, with a required ventilation channel gap. In the wind and vibration isolation device for the installed structure, the center point of the arc of the flow guide plate is eccentric to the center angle of the corner of the square structure, while the tangent of one end of the flow guide plate is The direction is one side 1a of the above-mentioned angular structure.
Parallel to
1. A windproof and vibration-proof device for a structure, characterized in that the windproof and vibration-proofing device is made obliquely intersecting a line passing through one side surface 1a. 2. The wind and vibration isolating device for a structure according to claim 1, characterized in that a flow guide plate is disposed in a range of about 1/3 or more of the length of the angular structure.