JPH1193114A - Emergent control method in stiffening girder type suspension bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a stiffening girder type suspension bridge from swinging and keep safety thereof by hanging a resistant disk from the central stiffening girder between main towers by a wire so as to be submerged in water below the suspension bridge at an emergency. SOLUTION: In a stiffening girder type suspension bridge 1, main towers 2, 3 are erected in sea water with a specified distance between them and stiffening girders 6 are suspended from main cables 4 through a number of hanging members 5 in the main towers 2, 3. When the stiffening girder type suspension bridge 1 constructed in such a way is exposed in a storm such as a typhoon, traffic of vehicles is regulated in advance and the hanging wires 9 are hung down to the sea level 10 and a steel resistant disk 11 is connected to the front end thereof and hung in the sufficiently deep sea. The resistant disk 11 is constituted of two upper and lower circular steel plates 12, 13 to form a circular shape with a specified thickness through a stiffening member 14 to keep the rigidity. When the suspension bridge 1 begins to vertically or rotatively vibrate, the resistant disk 11 receives a resistance of sea water to restrict the vibration. And hence, the flutter limit wind speed rises up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emergency vibration control method for a stiffened girder type suspension bridge, and more particularly, a relatively long suspension bridge suspended on a strait, lake, river, or the like is exposed to a strong wind such as a typhoon. It relates to an emergency vibration control method in the event of a failure.

[0002]

2. Description of the Related Art It is known that suspension bridges are subject to shaking and become unstable when wind is applied to the suspension bridge. As a countermeasure, the aerodynamic stability of the suspension bridge has been conventionally secured. In order to do so, the sides of the cross section in the width direction of the stiffening girder are mainly made into a triangular shape called fairing (shaping into a streamline etc.), or a flat plate is overhanged to devise the shape. Came. Further, as a vibration damping device, a device which aims at damping by using a relative motion with the main tower, such as installing rubber or a friction plate on a support for supporting a girder provided on the main tower has been proposed ( See Japanese Utility Model Laid-Open No. 1-136519). Of these, the former method of devising the shape cannot expect a remarkable effect against strong winds such as typhoons, and the latter method of damping using relative motion with the main tower, the stiffening girder near the main tower At present, the effect is not so high against strong winds as the former.

When a suspension bridge receives a strong wind, the suspension bridge shakes and the stiffening girders diverge, and the flutter phenomenon that eventually leads to collapse becomes a serious problem. In recent years, since the Akashi Kaikyo Bridge, a super-long suspension bridge with a distance between the main towers of over 2000 m is planned,
In such a long suspension bridge, there is concern about flutter that combines bending and torsion that occurs in the bridge when a strong wind is received, and the limit wind speed of the flutter that combines this bending and torsion is designed to be 80 m / s or more. There is a need. However,
If a very long suspension bridge is designed with the conventional design, the maximum wind speed of the flutter can be increased only to about 60 m / s, and countermeasures are required.

On the other hand, as a prior art focusing on increasing the value of the flutter limit wind speed, there is a proposal in Japanese Patent Publication No. 3-32643. In the gazette proposed in this publication, the cross-sectional shape of a stiffening girder of a suspension bridge is formed in a streamlined shape with sharp sides on both sides, and a predetermined widthwise width direction centered on a bridge axis in the streamlined stiffening girder. A fixed amount of additional load is fixedly provided along the bridge axis direction within the range, and even if weight is added to the stiffening girder along the bridge axis in this way, bending and twisting inherently occur. It says that the frequency does not increase very much, and that the total weight increases, which can raise the limit wind speed value of the flutter where bending and twisting are coupled. In order to sufficiently increase the flutter limit wind speed, the dead load of the suspension bridge
It is stated that it is preferable to apply a load of about 50 to 100% to the stiffening girder. However, an increase in the weight of the stiffening girder increases the load on the main cable and the suspending member for suspending the stiffening girder, and is uneconomical, for example, requiring a larger cable cross-sectional area. In particular, in the case of a very long suspension bridge having a long distance between the main towers as described above, the cable weight is increased by making the main cable thicker, and the burden on the main cable is increased more than the effect of the increase in the weight of the stiffening girder.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a relatively long suspension bridge suspended over a strait, lake, river, or the like, in a case of strong winds such as a typhoon. It is an object of the present invention to provide an emergency vibration control method for a stiffened girder-type suspension bridge capable of increasing a flutter limit wind speed value in an emergency evacuation.

[0006]

In order to achieve the above object, an emergency vibration damping method for a stiffening girder type suspension bridge according to the present invention comprises the steps of attaching a stiffening girder to a main cable extending between main towers. Emergency suspension damping method of a suspension bridge suspended through
In an emergency, a resistance board is suspended by wires at least in the stiffening girder at the center between the main towers so as to be submerged under the suspension bridge.

In the present invention, since the resistance board is suspended by wires on the stiffening girder in the center between the main towers of the suspension bridge so as to be submerged in the water below the suspension bridge, the stiffening girder acts on the resistance board. When the stiffening girder is going to vibrate vertically and rotationally due to wind and the like while the weight is subtracted from the buoyancy of water, the resistance board receives the resistance of water to suppress these vibrations. Therefore, in the event of an emergency due to a strong wind such as a typhoon, a resistive board with a weight that follows the vertical movement of the stiffening girder (particularly a weight that does not cause the wire tension to become zero when descending) is provided at the center between the main towers of the suspension bridge. By suspending the rigid girder with a wire so as to be immersed in the water below the suspension bridge, the vertical and rotational vibrations of the stiffening girder can be suppressed, and the flutter limit wind speed value can be increased.

[0008] In the emergency damping method for the stiffening girder type suspension bridge of the present invention, the resistance board may be hung on both lateral ends of the stiffening girder in the width direction. In this way, hanging the resistance board at both ends in the width direction of the stiffening girder can effectively suppress vertical and rotational vibrations at both ends in the width direction of the stiffening girder, and the flutter limit wind speed value Can be raised effectively.

Further, a plurality of resistance boards may be suspended at predetermined intervals along the stiffening girder. In this way, hanging a plurality of resistance boards at a predetermined interval along the stiffening girder can dispose the resistance boards in a more balanced manner than hanging only at the central portion, and costs per wire. The force can be reduced, and the load on the stiffening girder can be dispersed.

Further, as described above, the resistance plate according to the present invention receives the water resistance and the buoyancy in a well-balanced manner, and adjusts the weight so that the wire tension does not become zero when descending. May be formed.

The length of the stiffening girder suspension bridge to which the emergency vibration control method of the present invention is applied is not particularly limited. To make the shape of both ends of the stiffening girder streamlined,
Alternatively, it is possible to respond by increasing the main cable a little by using the technique proposed in Japanese Patent Publication No. 3-32643, etc., and if the distance between the main towers exceeds 1000 m, the cost increases with the conventional technique. This is because technical measures also become difficult. Therefore, more preferably, the distance between the main towers is 15
It is suitable to be applied to a long suspension bridge that exceeds 00 m, and even more than 2000 m.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view of a stiffening girder type suspension bridge to which the emergency vibration control method of the present invention is applied, and FIG. 2 is a sectional view of FIG.

The stiffening girder-type suspension bridge 1 has main towers 2 and 3 erected at a predetermined distance in the sea.
The main cable 4 to the main cable 4
The stiffening girder 6 is suspended from a plurality of suspension members 5. This stiffening girder type suspension bridge 1 has a flutter limit wind speed that can sufficiently withstand the wind speed that is constantly generated, for example, by forming both ends 7, 7 of the stiffening girder fairing and forming a triangular cross section. Value (for example, about 60 m / s). Further, in this example, suspension wires 9 are previously wound and attached to both end portions 7 of the stiffening girder 6 in the central portion 8 of the stiffening girder type suspension bridge 1.

In the stiffening girder suspension bridge 1, when the stiffening girder suspension bridge 1 is exposed to a strong wind such as a typhoon, the traffic of the vehicle is regulated in advance, and the suspension wire 9 is lowered to the sea surface 10, and A steel resistor board 11 shown in FIG. 3 is connected to the tip and suspended under the sea. This resistance board 11 is composed of two upper and lower circular steel plates.
The discs 12 and 13 are formed into a disk shape having a desired thickness with a stiffener 14 interposed therebetween to maintain rigidity. A connection for detachably attaching to the center hook of the upper steel plate 12 and the tip hook 15 of the suspension wire 9. A ring 16 is mounted. The weight of the resistance board 11 is designed to be such that the stiffening girder type suspension bridge 1 follows the sway that moves up and down in response to a strong wind such as a typhoon, and is particularly designed so that the wire tension does not become zero when descending. Have been.
The weight of the resistance board 11 from which the buoyancy has been subtracted is the weight of the stiffener 14.
, The load is applied to the main cable 4, but it is compensated by the amount of the vehicle acting as a live load during normal times. Therefore, it is not necessary to design the cross section of the main cable 4 large.

As described above, when the stiffening girder type suspension bridge 1 is exposed to a strong wind such as a typhoon, the traffic of the vehicle is regulated in advance, and the resistance board 11 is connected to the suspension wire 9 at the tip and sufficient resistance is provided. Depth (depth that does not come out of the sea due to vertical movement of suspension bridge due to wind)
Hanging under the sea. Thereby, when the stiffening girder type suspension bridge 1 is going to vibrate vertically and rotationally due to strong wind, etc.,
The resistance board 11 receives the resistance of the seawater and suppresses these vibrations, so that the flutter limit wind speed value increases, the stiffening girder type suspension bridge 1 is suppressed, and the stiffening girder type suspension bridge 1 can be kept safe.

Incidentally, in the case of the stiffening girder type suspension bridge 1 having the above-mentioned structure having a distance of 1220 m between the main towers 2 and 3 and a flutter limit wind speed of 60 m / s, when a pair of resistance boards 11 are suspended at the center part, Flutter with respect to the area of the resistance board 11 in the case of a total of 3 pairs, one pair is hung in front and back along the stiffening girder and a total of 20 pairs are hung at 61m intervals along the stiffening girder. The change of critical wind speed was simulated using a computer. FIG. 4 shows the results. Also, as a result of a trial calculation based on FIG. 4 when 20 pairs were hung, the flutter limit wind speed was 80 m /
It can be seen that a diameter of about 15 m is required to increase the value to s.

In the above example, the resistance board 11 has been described as being hung from the both ends 7, 7 of the stiffening girder 6 in the central portion 8 of the stiffening girder type suspension bridge 1. , 7 alone, or a plurality of units may be suspended along the stiffening girders 6 at predetermined intervals as shown in FIG.

Further, in the above example, the resistance disk 11 has been described as a hollow disk, but may be a solid disk.
In addition, the shape is an example of a circle when viewed from above, but this is a preferred example as a shape in which the resistance plate 11 can move in a stable posture in the sea, and is an axisymmetric polygonal shape. Is also good. Further, when viewed from the side, the lower surface side may be formed in a mortar shape with a central portion projecting slightly downward.

Further, in the above-described example, the example in which the hook 15 and the connection ring 16 are used to hang the resistance board 11 at the tip of the hanging wire 9 has been described, but the present invention is not limited to this. In short, any structure may be used as long as it is relatively easy to attach and detach and the resistance board 11 can be hung horizontally in the sea.

[0020]

As described above, according to the emergency damping method for the stiffened girder type suspension bridge according to the present invention, when a strong wind such as a typhoon or the like is applied, a relatively large strait, lake, river or the like is suspended. For a long suspension bridge, the flutter limit wind speed value can be raised in an emergency evacuation, thereby suppressing the swing of the stiffening girder suspension bridge and maintaining the safety of the stiffening girder suspension bridge.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a stiffening girder type suspension bridge to which the emergency vibration control method of the present invention is applied.

FIG. 2 is an explanatory sectional view taken along line XX of FIG. 1;

FIG. 3 is a schematic view showing a partially broken resistance plate according to the present invention.

FIG. 4 is a graph showing a relationship between a resistance board area and a flutter limit wind speed.

FIG. 5 is an explanatory view of another embodiment of a stiffening girder type suspension bridge to which the emergency vibration control method of the present invention is applied.

[Explanation of symbols]

1: Suspension girder suspension bridge 2, 3: Main tower
4: Main cable 5: Suspension member 6: Stiffening girder
7: Both ends 8: Central part of suspension bridge 9: Suspension wire 1
0: Sea surface 11: Resistance board 12, 13: Circular steel plate 1
4: Stiffener 15: Hook 16: Connecting ring

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masao Hirosawa Kobe Steel Co., Ltd. Kobe Head Office, 1-3-18 Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture

Claims (4)

[Claims] An emergency damping method for a suspension bridge in which a stiffening girder is suspended via a suspending member from a main cable stretched between main towers, wherein at least a central portion between the main towers is stiffened in an emergency. An emergency vibration control method for a stiffened girder type suspension bridge, wherein a resistance board is suspended by a wire so as to be submerged in the water below the suspension bridge. 2. The emergency vibration damping method for a stiffened girder type suspension bridge according to claim 1, wherein the resistance board is hung on both lateral ends of the stiffened girder. 3. The emergency vibration damping method for a stiffened girder type suspension bridge according to claim 1, wherein a plurality of resistance boards are hung at predetermined intervals along the stiffened girder. 4. The emergency damping method for a stiffened girder-type suspension bridge according to claim 1, wherein the resistance board is formed in a hollow disk shape.