JP2021113421A - Rubber bearings for bridge - Google Patents

Abstract

To allow shear deformation of rubber shoes when an earthquake motion of level 2 or lower occurs, and to restrain shear deformation of rubber shoes when an unexpected earthquake motion exceeding level 2 or ground deformation occurs in order to prevent the rubber shoes from breaking.SOLUTION: In a rubber bearing 10 for bridge installed between an upper structure and a lower structure, and including an upper shoe 11 fixed to a lower surface of the upper structure, a lower shoe 12 fixed to the lower structure, and a rubber shoe 13 provided between the upper shoe 11 and the lower shoe 12, side blocks 21, 22 are provided on both sides holding the rubber shoe 13 along the lower shoe 12 in the bridge axis direction and the direction perpendicular to the bridge axis direction at a distance d, being approximately equivalent to the maximum design displacement during an earthquake assuming a level-2 earthquake motion of the rubber shoe from the upper shoe 11. The lower shoe 12 is fixed to an upper surface of a base plate 16 fixed to the lower structure by bolts 17. The bolts 17 are broken by an earthquake motion exceeding level 2.SELECTED DRAWING: Figure 1

Description

The present invention relates to a rubber bearing for a bridge, and more particularly to a rubber bearing which is one of the bearings installed between an upper structure and a lower structure in a bridge.

The rubber supports installed between the upper structure and the lower structure in the bridge are the upper sill fixed to the upper structure, the lower sill fixed to the lower structure, and the rubber sill provided between the upper sill and the lower sill. It has a structure equipped with. The rubber shoe is generally made of laminated rubber in which steel plates and rubber layers are alternately laminated, and is a main part of a bearing that has a vertical load support function, a horizontal load support function, and a rotation function.

In recent years, due to unexpected seismic motion exceeding level 2 and movement of the superstructure due to ground deformation, the rubber shoe that supports the load of the superstructure undergoes shear deformation more than expected, which exceeds the deformation capacity of the rubber shoe. There are cases of damage in which the rubber sill is broken and the superstructure is laterally displaced or steps are formed. As a result, it is a major obstacle to the restoration of bridges, which are important as infrastructure.

As the prior art document of the present invention, for example, Patent Document 1 can be mentioned. However, although the invention described in the technical document aims to quickly restore the function of the bearing after an earthquake, the target rubber bearing is not shear-deformed in the horizontal direction.

Japanese Patent No. 6091695

The present invention has been made based on the above technical background, and achieves the following object.
An object of the present invention is to allow shear deformation of the rubber bearing up to a seismic motion of level 2 or lower, but restrain the shear deformation of the rubber bearing when an unexpected seismic motion or ground deformation exceeding level 2 occurs. The purpose is to provide a rubber bearing for a bridge that can prevent the rubber bearing from breaking and easily restore the bearing function after an earthquake.

The present invention employs the following means in order to achieve the above object.
That is, the present invention includes an upper sill that is installed between the upper structure and the lower structure and is fixed to the lower surface of the upper structure, a lower sill that is fixed to the lower structure, and the upper sill and the lower sill. In the rubber support for bridges equipped with a rubber shoe provided between them,
A distance from the upper shoe on both sides of the rubber shoe in the direction of the bridge axis and the direction perpendicular to the bridge axis, which is substantially equivalent to the maximum design displacement during an earthquake assuming a level 2 seismic motion of the rubber shoe. A side block is provided at the position
The lower shoe is fixed to the upper surface of a base plate fixed to the lower structure by a bolt, and the bolt is in a rubber bearing for a bridge, which is broken by a seismic motion exceeding level 2.

In the rubber bearing, an eccentric washer is attached to the washer mounting hole formed in the lower shoe.
The eccentric washer can adopt a configuration including an outer eccentric washer fitted in the washer mounting hole and having an eccentric hole and an inner eccentric washer fitted in the eccentric hole and having an eccentric hole defining an insertion hole for the bolt.

According to the present invention, the shear deformation of the rubber bearing is allowed up to the earthquake motion of level 2 or less, but the shear deformation of the rubber bearing is restrained when an unexpected earthquake motion or ground deformation exceeding the level 2 occurs. This prevents the rubber shoe from breaking and makes it easy to restore the bearing function after an earthquake.

It is a figure (A view of FIG. 2) which shows the embodiment of this invention and looked at the direction perpendicular to the bridge axis. It is a figure (B view view of FIG. 1) seen in the bridge axis direction of the same embodiment. It is a partially cutout plan view (C view of FIG. 2) of the same embodiment. The operation of the same embodiment is shown, where (a) shows a state at the time of a level 1 to level 2 earthquake, and (b) shows a state at the time of an earthquake exceeding level 2. It is a front view which shows the knock-off type bolt for fixing the lower shoe to a base plate, and also for fixing a displacement limiting plate to a side block. An eccentric washer attached to the lower sill is shown, (a) is a plan view, and (b) is a cross-sectional view.

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an embodiment of the present invention, FIG. 1 is a view of a rubber bearing 10 for a bridge viewed in a direction perpendicular to the bridge axis, and therefore X indicates a direction in the bridge axis. FIG. 2 is a view of the rubber bearing 10 in the direction of the bridge axis, and therefore Y indicates the direction of the bridge axis. FIG. 3 is a plan view of the rubber bearing 10.

The rubber bearing 10 is installed between the superstructure (bridge girder) and the substructure (pier or abutment) of the bridge. The rubber bearing 10 includes an upper shoe 11 fixed to the upper structure, a lower shoe 12 fixed to the lower structure, and a rubber shoe 13 fixed between the upper shoe 11 and the lower shoe 12.

The upper shoe 11 is a rectangular plate made of steel, and a shear key 14 for transmitting the horizontal force of the superstructure is provided in the center of the upper surface. Although not shown, the upper shoe 11 is fixed to the superstructure by bolts. The lower shoe 12 is fixed to the base plate 16 which is fixed to the lower structure via the anchor bolt 15. The lower shoe 12 is a rectangular plate made of steel like the upper shoe 11, but has larger dimensions in the bridge axis direction X and the bridge axis perpendicular direction Y than the upper shoe 11. The lower shoe 12 is fixed to the base plate 16 by a plurality of knock-off type bolts 17.

As shown in FIG. 5, the knock-off type bolt 17 is a bolt in which an annular notch 19 is formed in the shaft portion 18. The notch 19 is formed so as to be located at the interface between the lower shoe 12 and the base plate 16. Further, the knock-off type bolt 17 is formed with a pilot hole 20 at the axial center from the bolt head to the shaft portion 18 for raising a tap for extraction described later.

The knock-off type bolt 17 is attached to the lower shoe 12 via an eccentric washer 31. As shown in FIG. 6, the eccentric washer 31 is composed of a double tubular one having an outer eccentric washer 32 and an inner eccentric washer 33, and has eccentric holes 34 and 35, respectively. The outer eccentric washer 32 is fitted into the washer mounting hole 36 formed in the lower shoe 12, and the inner eccentric washer 33 is fitted into the eccentric hole 34 of the outer eccentric washer 32. The eccentric hole 35 of the inner eccentric washer 33 defines the insertion hole of the knock-off type bolt 17.

According to such an eccentric washer 21, the center position of the bolt insertion hole 35 is moved within a circle having a radius r shown in FIG. 6A by appropriately rotating the outer eccentric washer 32 and the inner eccentric washer 33. Can be made to.

Although not shown in detail, the rubber shoe 13 is made of laminated rubber in which steel plates and rubber layers are alternately laminated. The upper and lower thick steel plates of the rubber shoe 13 are fixed to the upper shoe 11 and the lower shoe 12 by mounting bolts, respectively.

Side blocks 21, 21, 22, and 22 are provided on both sides of the lower shoe 12 with the rubber shoe 13 sandwiched in the direction of the bridge axis and the direction perpendicular to the bridge axis. The two side blocks 21 and 21 are side blocks in the direction perpendicular to the bridge axis, and the two side blocks 22 and 22 are side blocks in the direction in the bridge axis direction.

The side blocks 21 and 21 in the direction perpendicular to the bridge axis and the side blocks 22 and 22 in the direction of the bridge axis are all made of steel, and are formed on the base 23 and the base 23 at almost the same height level as the upper sill 11. It is provided with an upright portion 24 to reach. Further, the side blocks 21 and 21 in the direction perpendicular to the bridge axis and the side blocks 22 and 22 in the direction of the bridge axis are located at positions separated from the upper shoe 11 by a predetermined distance d, and more specifically, the standing portion 24 is located from the end surface of the upper shoe 11. It is arranged at a position separated by a predetermined distance d, and the base portion 23 is fixed to the lower shoe 12 by a bolt 25.

Here, the predetermined distance d is a distance substantially corresponding to the maximum design displacement at the time of an earthquake assuming a level 2 seismic motion of the rubber shoe 13. The rubber bearings are shear deformed during an earthquake and the maximum design shear strain during a Level 2 earthquake is designed to be below the permissible value (generally 250%). From the relationship between this maximum design shear strain and the total rubber layer thickness of the rubber shoe 13, the maximum design displacement at the time of an earthquake assuming a level 2 earthquake motion can be obtained.

In addition to the above configurations, the following known displacement limiting structures are added to the side blocks 21 and 21 in the direction perpendicular to the bridge axis. A guide recess 26 is provided at the top of the upright portion 24 of the side blocks 21 and 21 in the direction perpendicular to the bridge axis in the direction perpendicular to the bridge axis. The displacement limiting plate 27 is fitted in the guide recess 26 so as to be movable in the direction perpendicular to the bridge axis.

The displacement limiting plate 27 has a length at which the tip thereof is close to the upper shoe 11 with a small gap (about 5 mm), and is fixed to the upright portion 24 by a knock-off type bolt 28. As shown in FIG. 5, the knock-off type bolt 28 is similar to the knock-off type bolt 17 described above, and is formed so that the annular notch 19 is located at the interface between the displacement limiting plate 27 and the upright portion 24. ..

At the top of the upright portion 24 of the side blocks 21 and 21 in the direction perpendicular to the bridge axis, a holding plate 29 that covers the portion of the displacement limiting plate 27 fitted in the guide recess 26 is fixed by a bolt 30. Although not shown, a friction sheet such as a thin copper plate or a rubber plate is provided on the upper surface of the displacement limiting plate 27 in order to increase the friction between the displacement limiting plate 27 and the holding plate 29.

In a bridge provided with the rubber bearing 10 as described above, when a seismic motion of level 1 or less occurs at all times or in the case of a seismic motion of level 1 or less, the rubber shoe 13 is freely sheared and deformed in the direction of the bridge axis. As a result, the expansion and contraction of the superstructure due to the temperature change is absorbed. In addition, vibration in the bridge axis direction of the superstructure is suppressed from being transmitted to the substructure.

On the other hand, in the direction perpendicular to the bridge axis, the displacement of the upper shoe 11 in the same direction is constrained by the displacement limiting plate 27, so that the shear deformation of the rubber shoe 13 is constrained. As a result, the slow rolling of the superstructure due to strong winds and earthquake motions of level 1 or lower at all times is prevented, and the operation of the vehicle is not hindered.

When a seismic motion exceeding level 1 but level 2 or lower occurs, the rubber shoe 13 is freely sheared and deformed in the direction of the bridge axis as in the case of level 1 or lower. As a result, the vibration of the superstructure in the bridge axis direction is suppressed from being transmitted to the substructure, and an excessive load is prevented from being applied to the substructure.

On the other hand, in the direction perpendicular to the bridge axis, as shown in FIG. 4A, the knock-off type bolt 28 is broken by the seismic force acting on the displacement limiting plate 27 from the upper structure via the upper shoe 11, and the displacement limiting plate 27 Is pushed out of the side block 21. As a result, the restraint of the upper shoe 11 by the displacement limiting plate 27 is released, so that the rubber shoe 13 is freely sheared and deformed, and an excessive load is prevented from being applied to the lower structure. In this way, the rubber bearing 10 can be freely shear-deformed in all directions up to the level 2 earthquake motion, that is, up to the maximum design displacement d at the time of an earthquake.

When an unexpected seismic motion or ground motion exceeding level 2 occurs, the upper sill 11 directly collides with the upright portion 24 of the side block 22 in the direction of the bridge axis, and FIG. 4B is shown in the direction perpendicular to the bridge axis. As shown in the above, the upper bridge 11 pushes the displacement limiting plate 27 outward of the side block 21 and then collides with the upright portion 24 thereof.

As a result, the knock-off type bolt 17 fixing the lower shoe 12 and the base plate 16 is broken, and the lower shoe 12 slides on the base plate 16. As a result, even in an unexpected seismic motion exceeding level 2, the rubber shoe 13 does not break and the seismic force is released by the slip of the lower shoe 12, and it is possible to prevent damage to the superstructure and the substructure. In this way, damage to the rubber bearing 10, the superstructure and the substructure is prevented, so that the bridge can be easily restored after the earthquake.

Since the displacement limiting plate 27 is provided with a friction sheet on the upper surface as described above, the frictional force acting on the pressing plate 29 is enhanced, and the displacement limiting plate 27 is prevented from suddenly popping out when pushed out by the upper shoe 11. can.

As shown in FIG. 5, pilot holes 20 are formed in the knock-off type bolts 17 and 28. When restoring a bridge after an earthquake, if a left-hand screw tap is set up using the pilot hole 20 and a left-hand screw bolt is screwed in, the broken knock-off type bolts 17 and 28 will come out in the loosening direction, so the bridge will break. The bolt can be easily pulled out.

Further, since the knock-off type bolt 17 is attached to the lower shoe 12 via the eccentric washer 31, the center position of the bolt insertion hole 35 is moved by appropriately rotating the outer eccentric washer 32 and the inner eccentric washer 33. It is possible to easily align the holes through which the bolts are passed at the time of restoration.

10: Rubber bearing 11: Upper shoe 12: Lower shoe 13: Rubber shoe 16: Base plate 17: Knock-off type bolt 19: Notch 21, 22: Side block 23: Base 24: Standing part 27: Displacement limiting plate 28: Knock-off type bolt 29: Holding plate 31: Eccentric washer

Claims (2)

Rubber installed between the upper structure and the lower structure and fixed to the lower surface of the upper structure, the lower sill fixed to the lower structure, and the rubber provided between the upper sill and the lower sill. In the rubber support for bridges equipped with shoes
A distance from the upper shoe on both sides of the rubber shoe in the direction of the bridge axis and the direction perpendicular to the bridge axis, which is substantially equivalent to the maximum design displacement during an earthquake assuming a level 2 seismic motion of the rubber shoe. A side block is provided at the position
A rubber bearing for a bridge, wherein the lower shoe is fixed to the upper surface of a base plate fixed to the lower structure by a bolt, and the bolt is broken by a seismic motion exceeding level 2. An eccentric washer is attached to the washer mounting hole formed in the lower shoe.
The eccentric washer is characterized by including an outer eccentric washer fitted into the washer mounting hole and having an eccentric hole, and an inner eccentric washer fitted into the eccentric hole and having an eccentric hole defining an insertion hole for the bolt. The rubber bearing for a bridge according to claim 1.

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