JP4145196B2 - Fall bridge prevention device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a falling bridge prevention device that prevents a bridge girder from falling from a lower structure such as a pier or an abutment during a large earthquake. More specifically, the present invention limits the displacement of a bridge girder during a normal earthquake and reduces energy during a large earthquake. The present invention relates to a falling bridge prevention device having a function of absorbing.
[0002]
[Prior art]
When a horizontal force acts on the pier or abutment due to a large earthquake, the bridge pier or the abutment will only be damaged, causing them to vibrate and causing the bridge girder to fall or drop. In order to prevent such a bridge girder from falling, there are known ones in which the girder on the pier and between the abutment and the girder are connected by a PC cable or by a link.
[0003]
However, these conventional falling bridge prevention devices are not provided with a mechanism for absorbing the energy in the event of a large earthquake, and have a structure in which a load acts suddenly. In addition, when a seismic reinforcement of an existing bridge is carried out, a displacement limiting device (energy absorbing device at the time of an earthquake) and a falling bridge prevention device are often installed, but it is often difficult to install these two separately.
[0004]
Under such a background, a device that has an energy absorption function in a fallen bridge prevention device has been proposed (see Patent Document 1). The fallen bridge prevention device described in this document has a metal cylinder loosely fitted to the connecting cable, a wedge plate is provided, and the wedge plate expands the diameter of the cylinder by the displacement of the bridge girder. It is designed to absorb energy.
[0005]
[Patent Document 1]
JP 2001-64914 A
[0006]
[Problems to be solved by the invention]
The present invention has been made based on the technical background as described above, and achieves the following object.
It is an object of the present invention to provide a falling bridge prevention device that has a function of limiting the displacement of a bridge girder and absorbing energy during an earthquake.
[0007]
[Means for Solving the Problems]
The present invention employs the following means in order to achieve the above object.
That is, according to the present invention, the bridge girder (3) is dropped from a lower structure such as a bridge pier or an abutment by a connecting cable (4) having one end attached to the bridge axial direction end of the bridge girder (3). A fallen bridge prevention device (1) for preventing,
A bracket (5) provided at an end of the bridge beam (3) and having an insertion hole (7) through which the connection cable (4) is inserted, and an end of the connection cable (4) protruding from the bracket (5) A stopper (9) fixed to the part,
A large number of disc spring-like members (16) are fitted and arranged on the outer periphery of the connecting cable (4) between the bracket (5) and the stopper (9) so that adjacent ones are opposite to each other. ,
Each of the disc spring-like members (16) is in a falling bridge prevention device characterized in that an outer peripheral edge with which adjacent ones contact each other is formed on a flat surface (17) .
[0009]
More specifically, a shock absorber (10) disposed on the surface of the bracket (5) on the stopper (9) side, through which the connecting cable (4) passes, and the shock absorber (10) and the stopper ( 9) and a press plate (13) which is disposed on the outer periphery of the connecting cable (4) so as to be movable in the axial direction, and between the press plate (13) and the stopper (9). A coil spring (15) surrounding the connecting cable (4), and the multiple disc spring-like members (16) are disposed between the pressing plate (13) and the shock absorber (10). Has been placed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of the present invention. FIG. 1 is an overall front view taken along a direction perpendicular to the bridge axis, and FIG. 2 is a cross-sectional view. This embodiment is an example in which a falling bridge prevention device according to the present invention is attached between bridge girders 3 and 3 which are installed at the upper part of the bridge pier 2 so that the ends in the bridge axial direction face each other.
[0011]
The falling bridge prevention device 1 is attached to each end of the bridge girder 3 and has a connecting cable 4 that is a member that connects these girder ends. Moreover, the falling bridge prevention device 1 has a bracket 5 for attaching to the bridge girder 3, and the bracket 5 is fixed to the bridge girder 3 via a sole plate 6. As shown in FIG. 2, the bracket 5 is provided with an insertion hole 7 through which the connection cable 4 is inserted. A male screw portion 8 is formed at the end of the connecting cable 4 protruding from the bracket 5, and a nut 9 constituting a stopper is screwed to the male screw portion 8.
[0012]
A shock absorber 10 is provided on the surface of the bracket 5 on the stopper 9 side. The shock absorber 10 includes a rubber body 11 and a pressure plate 12, and the connecting cable 4 passes through the shock absorber 10. A pressing plate 13 is disposed between the stopper 9 and the bearing plate 12. The pressing plate 13 is fitted to the connecting cable 4 so as to be movable in the axial direction. A locking cylinder 14 is screwed onto the male screw portion 8, and a coil spring 15 surrounding the connecting cable 4 is disposed between the distal end flange 14 a of the locking cylinder 14 and the pressing plate 13. The expansion / contraction stroke of the coil spring 15 can be changed by appropriately changing the mounting position of the locking cylinder 14.
[0013]
A large number of disc spring-like members 16 are fitted and arranged between the supporting plate 12 and the pressing plate 13 in the connecting cable 4. The disc spring-like member 16 has the same external shape as a well-known disc spring, and is a frustoconical member having a hole in the center. And when a load is applied, it shows elasticity until it reaches the yield point. However, unlike a normal disc spring, this invention is also called a disc spring-like member because it expects energy absorption by plastic deformation after yielding.
[0014]
The disc spring-like members 16 are arranged so that the adjacent ones are opposite to each other. As a result, when the connecting cable 4 is displaced to the left in FIG. 2, the disc spring-like member 16 is pressed by the pressing plate 13, and is elastically deformed and further plastically deformed. As the disc spring-like member 16, a low yield point steel such as SS400 having a large elongation after yielding is used.
[0015]
The disc spring-like members 16 are deformed when the outer peripheral edges of those adjacent to each other come into contact with each other and press in the axial direction. In order to ensure this deformation, the outer peripheral edge of each disc spring-like member 16 is formed on a flat surface 17 as shown in FIG.
[0016]
Referring to FIG. 2 again, the connecting cable 4 protruding from the shock absorber 10 is covered with a cylindrical cover 18. This cover 18 is fixed to the bearing plate 12 by bolts 19. A deflection block 20 is arranged on the opposite side of the stopper 9 across the bracket 5 as in the conventional case. The deflection block 20 is fixed to a pair of mounting plates 21 fixed to the bracket 5 by bolts 22. An insertion hole 22 that extends toward the entrance side is formed in the deflection block 20, and the connecting cable 4 is inserted through the hole 22. The connecting cable 4 includes a PC steel strand 23a, a steel condominium 23b into which the PC steel strand 23a is inserted and fixed, and a synthetic resin covering material 23c for covering the PC steel strand 23a. .
[0017]
In the above-described fallen bridge prevention device, the coil spring 15 is compressed and deformed in response to the displacement of the bridge girder 3 during a normal earthquake in which the displacement of the bridge girder 3 is small. On the other hand, when a large displacement occurs in the bridge girder 3 due to a large earthquake, the coil spring 15 reaches the compression limit and the pressing plate 13 presses the group of disc spring members 16. Thereby, the disc spring-like member 16 is elastically deformed, and after reaching the yield point, it is plastically deformed to absorb the energy of the earthquake. After the disc spring-like member 16 is plastically deformed, the buffer rubber body 11 is deformed to absorb energy, and a function to prevent a fallen bridge is performed for excessive displacement beyond that. In addition, the disc spring-like member 16 plastically deformed by a large displacement of the bridge girder can be replaced, and can satisfy two functions of a repeated energy absorption function and a displacement limiting function.
[0018]
4 (a) and 4 (b) are characteristic diagrams showing the relationship between the load and the displacement in the conventional and the falling bridge prevention device according to the present invention, respectively. In the characteristic diagram of the device according to the present invention shown in (b), the displacement areas a, b and c are the spring action range, the disc spring action range and the buffer rubber body action range, respectively. The amount of absorption could be increased.
[0019]
The above embodiment is merely an example, and the present invention can take various forms. For example, in the above-described embodiment, the structure for connecting the beams on the bridge piers is shown. However, the present invention can also be applied when connecting the abutment and the bridge beams.
[0020]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a falling bridge prevention device that has a function of limiting the displacement of a bridge girder and absorbing energy during an earthquake.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of the present invention, as viewed in a direction along a direction perpendicular to a bridge axis.
FIG. 2 is a sectional view of the same embodiment.
FIG. 3 is an enlarged sectional view showing a disc spring-like member.
FIGS. 4A and 4B are characteristic diagrams showing the relationship between load and displacement in a conventional and a fallen bridge prevention apparatus according to the present invention, respectively.
[Explanation of symbols]
1: Falling bridge prevention device 2: Bridge pier 3: Bridge girder 4: Connection cable 5: Bracket 7: Insertion hole 9: Nut (stopper)
10: shock absorber 11: buffer rubber body 12: bearing plate 13: pressing plate 15: coil spring 16: disc spring-like member 17: flat surface

Claims (2)

Bridge bridge prevention to prevent the bridge girder (3) from dropping from the lower structure of the bridge pier, abutment, etc., by the connecting cable (4) having one end attached to the bridge axial end of the bridge girder (3) A device (1) comprising:
A bracket (5) provided at an end of the bridge beam (3) and having an insertion hole (7) through which the connection cable (4) is inserted, and an end of the connection cable (4) protruding from the bracket (5) A stopper (9) fixed to the part,
A large number of disc spring-like members (16) are fitted and arranged on the outer periphery of the connecting cable (4) between the bracket (5) and the stopper (9) so that adjacent ones are opposite to each other. ,
Each of the disc spring-shaped members (16) has a flat surface (17) with an outer peripheral edge on which adjacent ones are in contact with each other . A shock absorber (10) disposed on the surface of the bracket (5) on the stopper (9) side, through which the connecting cable (4) passes;
A pressing plate (13) disposed between the shock absorber (10) and the stopper (9) and fitted to the outer periphery of the connecting cable (4) so as to be axially movable;
A coil spring (15) disposed between the pressing plate (13) and the stopper (9) and surrounding the connecting cable (4);
The fall bridge prevention device according to claim 1, wherein the plurality of disc spring-like members (16) are arranged between the pressing plate (13) and the shock absorber (10).

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