JP2002322611A - Earthquake-proof structure of suspension bridge and earthquake-proof and reinforcing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an earthquake-proof structure of a suspension bridge and an earthquake-proof and reinforcing method for the suspension bridge improved in earthquake-proof performance. SOLUTION: In this earthquake-proof structure for the suspension bridge 15, 25, 32, 38, a bridge girder 2 is supported through a support member 6 by a pier 4, a main tower 8 is provided in a part corresponding to the pier on the bridge girder, and the main stupa hangs down the bridge girder through cables 10. The suspension bridge of the invention has a first and second brackets 16, 17 projected on the top part of the pier on both sides in the cross direction of the bridge, and at least one set of auxiliary cables 22 connecting the first and second brackets and the upper pat of the main tower, disposed substantially symmetrically in the cross direction of the bridge, and to which designated tension is applied. Further, the earthquake-proof reinforcing method is also provided for the suspension bridge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earthquake-resistant structure and a method for reinforcing a suspension bridge, and more particularly to a bridge girder supporting a bridge girder via a support member and a main tower provided on a portion corresponding to the bridge pier on the bridge girder. The present invention relates to an anti-seismic structure and an anti-seismic reinforcement method for a suspension bridge in which the main tower suspends the bridge girder via a cable.

[0002]

2. Description of the Related Art Since the Great Hanshin-Awaji Earthquake, the concept of earthquake resistance for suspension bridges has been reviewed using this as a lesson, and various seismic measures have been implemented for new and existing suspension bridges. In the case of a new suspension bridge, the design can be made considering seismic measures from the beginning, but in the case of an existing suspension bridge, there are many restrictions such as the connection of the members that make up the suspension bridge, and it is not easy to take seismic measures.

[0003] Next, with reference to Figs. 1 and 2, a description will be given of a conventional technique in which an earthquake-resistant reinforcement method is applied to a cable-stayed bridge which is an example of a suspension bridge. As shown in FIG. 1, the cable-stayed bridge 1 generally includes a bridge girder 2, which is supported on a pier 4 via a support member 6, and a main tower 8 on the bridge girder 2. The main tower 8 and the bridge girder 2 are connected by a plurality of cables 10 so that the bridge girder 2 is supported. FIG. 2 is a partially enlarged view showing a support structure of an existing cable stayed bridge. As shown in FIG. 2, conventionally, to improve the seismic resistance of a cable-stayed bridge, a method of newly interposing a seismic isolation device 12 between the bridge girder 2 and the pier 4, A method of directly reinforcing the main tower 8 by attaching a reinforcing material 14 to the main tower 8 is adopted.

[0004]

However, in the conventional seismic retrofitting method for these existing cable stayed bridges,
In the method of interposing the seismic isolation device 12 between the bridge girder 2 and the pier 4, the heavy bridge girder 2 must be jacked up, so that the construction becomes large and the construction cost becomes high, and the construction period is also reduced. There is a problem such as lengthening. In addition, the seismic isolation device itself requires a large area because it supports a large weight, and there is a problem that the upper surface of the pier has to be expanded because the displacement during an earthquake increases due to seismic isolation. Next, the method of reinforcing the main tower 8 with the reinforcing material 14 requires a traffic regulation depending on the number of reinforcing members or a reinforcing point, and a problem that the cost is increased because the scaffolding is extensively installed. There is.

On the other hand, in order to improve the seismic resistance of the newly installed cable-stayed bridge, it is necessary to increase the cross section of the main tower or to increase the thickness of the main tower, and to provide a seismic isolation device. In this case, the seismic isolation device must be a large-area device to support a large weight, and the seismic isolation increases displacement during an earthquake, so it must be large enough to cover the top of the pier. There is a problem in cost.

Accordingly, the present invention has been made to solve the problems of the prior art, and a seismic structure and an antiseismic reinforcement method for a suspension bridge capable of easily improving the seismic performance of a new suspension bridge and an existing suspension bridge. It is intended to provide.

[0007]

According to the present invention, a bridge girder is supported by a pier via a support member, and a main tower is provided at a portion corresponding to the pier on the bridge girder. Is a quake-resistant structure of a suspension bridge that suspends the bridge girder via a cable, and first and second brackets provided on an upper portion of a pier, respectively, protruding on both sides in a bridge width direction;
At least one set of auxiliary cables that connect the first and second brackets and the upper part of the main tower respectively and are provided substantially symmetrically in the bridge width direction and are given a predetermined tension in advance. Features. In the seismic structure of the suspension bridge of the present invention configured as described above, even if the main tower and the bridge girder vibrate in the bridge width direction due to the earthquake, at least one of the pre-set tension is applied.
The set of auxiliary cables connects the first and second brackets to the upper part of the main tower, respectively.
Since the set of auxiliary cables is provided substantially symmetrically, the swing of the main tower is suppressed, and the lifting and pushing operations of both ends of the bridge girder are also suppressed. This reduces the stress generated at the base of the main tower and the reaction force generated at the bearing member. As a result, an earthquake-resistant effect can be obtained in the entire suspension bridge.

[0008] The earthquake-resistant structure of the suspension bridge of the present invention is preferably further provided so as to connect the first and second brackets to the intermediate portion of the main tower, and to be provided substantially symmetrically in the bridge width direction and to have a predetermined tension. At least one with
It has a set of second auxiliary cables. Preferably, the earthquake-resistant structure of the suspension bridge according to the present invention further comprises at least one set of first and second brackets each connected to the pier and provided substantially symmetrically in the bridge width direction and given a predetermined tension in advance. Has a third auxiliary cable.

Further, the present invention provides an earthquake-resistant suspension bridge in which a bridge pier supports a bridge girder via a support member, and a main tower is provided on a portion of the bridge girder corresponding to the pier, and the main tower suspends the bridge girder via a cable. A reinforcing method for providing first and second brackets projecting on both sides of a bridge pier in an upper portion of a bridge pier, and connecting the first and second brackets to an upper portion of a main tower, respectively. Providing at least one set of auxiliary cables to which a predetermined tension is applied in advance, in a substantially symmetric manner in the bridge width direction.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 3 is an overall front view of the suspension bridge, and FIG. 4 is an enlarged side view taken along line IV-IV in FIG. As shown in FIG. 3 and FIG.
Reference numeral 5 denotes a cable-stayed bridge which is a type of suspension bridge to which the present embodiment is applied. The cable-stayed bridge 15 includes a bridge girder 2, a pier 4 for supporting the bridge girder 2 via a support member 6, and a bridge girder 2. A main tower 8 provided at a portion corresponding to the upper pier 4 and a cable 10 for connecting the main tower 8 to the bridge girder 2 and suspending the bridge girder 2 are provided. The main tower 8 is fixed to the bridge girder 2 at its base 8a. Further, the support member 6 includes a support member 6a provided at the center of the bridge girder 2 in the bridge width direction and support members 6b provided on both sides. 6c.

The cable-stayed bridge 15 further includes brackets 16 projecting in the bridge width direction on both sides of the bridge pier 4 in the bridge width direction.
17 are connected between tip mounting portions 16a, 17a located above the tips of the brackets 16, 17 and top mounting portions 20a, 21a provided on both sides of the top of the main tower 8. The auxiliary cable 22 is provided symmetrically in the bridge width direction. Furthermore, a predetermined tension is applied to these auxiliary cables 22 in advance so that excessive loosening does not occur when an earthquake occurs and the restraint by the auxiliary cables 22 is not lost.

Next, the operation of the first embodiment will be described. When constructing a new cable stayed bridge 15, the bridge girder 2, the pier 4 integrally provided with the brackets 16 and 17, the support members 6 (6 a, 6 b, 6 c), the main tower 8, the cable 10,
In addition, the auxiliary cables 22 are prepared and assembled to obtain an earthquake-resistant structure of the cable-stayed bridge 15 as shown in FIGS. 3 and 4.

On the other hand, when an existing cable-stayed bridge is to be subjected to seismic reinforcement, the bridge girder 2, the pier 4, and the support members 6 (6a, 6
b, 6c), for the existing cable-stayed bridge provided with the main tower 8 and the cable 10, the brackets 16 and 17 described above are provided so as to protrude on both sides in the bridge width direction above the pier 4, and In addition, the brackets 16 and 17 are connected by the auxiliary cable 22.
Are connected to the top mounting portions 20a and 21a provided on both sides of the top of the main tower 8, and these auxiliary cables 22 are provided so as to be symmetrical in the bridge width direction. At this time, when the earthquake occurs, the auxiliary cable 22 is excessively loosened and the auxiliary cable 2
A predetermined tension is applied in advance so as not to lose the constraint caused by the second member. Thus, the cable-stayed bridge 15 reinforced with earthquake resistance can be obtained.

On the other hand, in a cable-stayed bridge having a conventional structure without a bracket and an auxiliary cable, the main tower 8 is not affected by an earthquake.
Vibrates in the bridge width direction, the both ends of the bridge girder 2 alternately lift and lower alternately in conjunction with the vibration of the main tower 8, and a large stress is generated in the base 8 a of the main tower 8. A large reaction force is generated in the support member 6 (particularly, the support members 6b and 6c) provided between the bridge 2 and the pier 4. For this reason,
It is feared that the cable-stayed bridge will be destroyed, collapsed, and come into contact with nearby structures. However, in the cable-stayed bridge 15 according to the present embodiment, even if an earthquake occurs and the main tower 8 vibrates in the bridge width direction, the auxiliary cable 22 is not excessively loosened so that the restraint is not lost. Since a predetermined tension is applied in advance, the swinging of the main tower 8 and the lifting and lowering operations of the both ends of the bridge girder 2 are suppressed, and the stress generated at the base 8a of the main tower 8 and the bearing member 6, especially , Bearing members 6b, 6c on both sides
The reaction force or the like generated in the above is greatly reduced.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 5, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted. The cable-stayed bridge 25 to which the second embodiment is applied includes a second auxiliary cable 2 in addition to the structure of the above-described first embodiment.
8 is provided. The second auxiliary cable 28 is connected to the front end mounting portions 16a of the brackets 16 and 17,
17a and the intermediate mounting portions 30a and 31a of the main tower 8 are provided symmetrically in the vehicle width direction so as to be connected to each other. A predetermined tension is also applied to the second auxiliary cable 28 in advance so that the second auxiliary cable 28 is not loosened excessively when an earthquake occurs and the restraint by the second auxiliary cable 28 is not lost.

Next, the operation of the second embodiment will be described. In the earthquake-resistant structure of the cable-stayed bridge 25 of the second embodiment configured as described above, it is natural that the operation and effect of the above-described first embodiment can be obtained. In addition, a predetermined tension is applied in advance. Since the main tower 8 and the brackets 16 and 17 are symmetrically connected to each other by the two sets of auxiliary cables 22 and 28, a greater seismic effect can be obtained.
Furthermore, since two sets of auxiliary cables 22 and 28 are used, the width of the tension that can be applied to these auxiliary cables 22 and 28 is widened, and there is an effect that the degree of freedom in design is widened. In the second auxiliary cable 28, the positions of the attachment portions 30a and 31a may be changed or the number (the number of sets) may be increased in accordance with the required earthquake resistance.

Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 6, the same components as those shown in FIG. 4 (first embodiment) are denoted by the same reference numerals, and description thereof will be omitted. The cable stayed bridge 32 to which the third embodiment is applied has a structure in which a third auxiliary cable 34 is provided in addition to the structure of the above-described first embodiment (see FIG. 4). The third auxiliary cable 34 is connected to the bracket 1
Tip attachment portions 16b, 1 located below the tips of 6, 17
7b are provided symmetrically in the bridge width direction so as to connect the mounting portions 36a, 37a located below the brackets 16, 17 of the pier 4. Note that this third
A predetermined tension is also applied to the auxiliary cable 34 in advance so that excessive loosening does not occur when an earthquake occurs and the restraint by the third auxiliary cable 34 is not lost.

Next, the operation of the third embodiment will be described. In the earthquake-resistant structure of the cable-stayed bridge 32 of the third embodiment configured as described above, the operation and effect of the first embodiment described above are exerted. Furthermore, in the cable stayed bridge 32 of the third embodiment, when an earthquake occurs, the force received by the auxiliary cable 22 can be reduced by balancing with the third auxiliary cable 34. The stress value (response value) generated in the bases 16c, 17c of the 17 can be reduced. As a result, according to the present embodiment, the structure of the brackets 16 and 17 can be reduced, and the cost is reduced. In the present embodiment, as for the third reinforcing cable 34, the positions of the mounting portions 36a and 37a may be changed or the number (the number of sets) of the third reinforcing cable 34 may be increased according to the required seismic performance.

Next, a fourth embodiment of the present invention will be described with reference to FIG. This fourth embodiment is similar to the second embodiment shown in FIG.
This is an embodiment in which the embodiment and the third embodiment shown in FIG. 6 are combined. Therefore, the same parts as those shown in FIGS. 5 and 6 are denoted by the same reference numerals, and their description is omitted. The cable stayed bridge 38 to which the fourth embodiment is applied includes the brackets 16 and 17, the reinforcing cable 22, and the second
A reinforcing cable 28 and a third reinforcing cable 34 are provided. As described above, a predetermined tension is applied to each of the reinforcing cables 22, 28, and 34 so that excessive loosening does not occur when an earthquake occurs and the cables are not restrained.

Although an example of a cable-stayed bridge has been described as an embodiment of the present invention, the present invention is not limited to a cable-stayed bridge, but can be applied to other types of suspension bridges.

[0021]

As described above, according to the earthquake-resistant structure of the suspension bridge of the present invention, the seismic performance of the new suspension bridge and the existing suspension bridge can be easily improved. Also, in the seismic retrofitting method of the suspension bridge of the present invention, similarly, the seismic performance of the suspension bridge can be easily improved.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a general structure of a conventional cable stayed bridge.

FIG. 2 is an enlarged front view showing a conventional support structure of the cable stayed bridge shown in FIG.

FIG. 3 is a schematic front view showing an earthquake-resistant structure of the cable-stayed bridge according to the first embodiment of the present invention.

FIG. 4 is an enlarged side view taken along the line IV-IV in FIG. 3;

FIG. 5 is a side view showing an earthquake-resistant structure of a cable-stayed bridge according to a second embodiment of the present invention.

FIG. 6 is a side view showing an earthquake-resistant structure of a cable-stayed bridge according to a third embodiment of the present invention.

FIG. 7 is a side view showing an earthquake-resistant structure of a cable-stayed bridge according to a fourth embodiment of the present invention.

[Explanation of symbols]

 15, 25, 32, 38 Cable-stayed bridge 2 Bridge girder 4 Bridge pier 6 Support member 8 Main tower 10 Cable 16, 17 Bracket 16a, 17a Tip mounting part 20a, 21a Top mounting part 22 Auxiliary cable 28 Second auxiliary cable 30a, 31a Intermediate Mounting part 34 Third auxiliary cable

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Koichi Inoue 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Inside the Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Hisaya Myojin 4-chome Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture No. 6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory F-term (reference) 2D059 AA41 BB06 BB08 GG05

Claims (4)

[Claims] The bridge girder is supported by a bridge pier via a support member, and a main tower is provided at a portion corresponding to the pier on the bridge girder, and the main tower has an earthquake-resistant structure of a suspension bridge for suspending the bridge girder via a cable. A first and a second bracket protrudingly provided on both sides in the bridge width direction above the pier; connecting the first and second brackets to the upper part of the main tower, respectively; At least one of which is provided substantially symmetrically in the width direction and is given a predetermined tension in advance.
A suspension bridge having a pair of auxiliary cables. Further, at least one pair of the first and second brackets and the intermediate portion of the main tower, which are respectively provided and are provided substantially symmetrically in a bridge width direction and are given a predetermined tension in advance. The earthquake-resistant structure of the suspension bridge according to claim 1, further comprising a second auxiliary cable. Further, at least one set of a third auxiliary member which connects the first and second brackets to the pier and is provided substantially symmetrically in the bridge width direction and is given a predetermined tension in advance. The earthquake-resistant structure of the suspension bridge according to claim 1 or 2, further comprising a cable. 4. A seismic reinforcement method for a suspension bridge in which a bridge girder is supported by a bridge pier via a bearing member, and a main tower is provided at a portion corresponding to the pier on the bridge girder, and the main tower suspends the bridge girder via a cable. A step of providing first and second brackets projecting on both sides in the bridge width direction above the pier, respectively, and connecting these first and second brackets to the upper part of the main tower in advance. Providing at least one set of auxiliary cables to which a predetermined tension is applied, substantially symmetrically in the bridge width direction.