JP2013221576A - Laminated rubber bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated rubber bearing usable under high contact pressure and excelling in fatigue durability by reducing local shearing strain.SOLUTION: A laminated rubber bearing formed by alternately laminating rigid plates 2, 3 and rubber layers 4, 5, includes a center laminated part 1a and an outer peripheral laminated part 1b. The number of lamination of the center laminated part 1a is made larger than the number of lamination of the outer peripheral laminated part 1b, and each rubber layer 5 of the outer peripheral laminated part 1b is made softer than each rubber layer 4 of the center laminated part 1a.

Description

  The present invention relates to a laminated rubber bearing, and more particularly to a laminated rubber bearing that is installed between an upper structure and a lower structure in a bridge to transmit a vertical load of the upper structure to the lower structure.

  As a function required for the bearing using the laminated rubber, there is not only a vertical load support function for transmitting the load of the superstructure to the substructure, but also a rotation function that enables the superstructure to rotate. Since rubber has the property of elastically deforming when subjected to a load, the latter rotation function utilizes the elasticity of rubber. On the other hand, regarding the vertical load support function, the laminated rubber needs to generate compressive strain to such an extent that no tensile stress is generated in the rubber in order to follow the upper load when it rotates.

  When compressive strain occurs in the laminated rubber, the rubber does not change in volume even if it is deformed, so that a phenomenon occurs in which the rubber bulges greatly to the side. This swelling of the rubber generates a local shear strain (compression strain + rotational strain) in the rubber, which has an adverse effect. Therefore, when the laminated rubber is increased in surface pressure with the conventional structure, the local shear strain increases and the fatigue durability decreases.

  If the single layer thickness of the rubber layer is reduced to increase the number of laminated layers, the vertical rigidity of the laminated rubber can be increased and the compressive strain can be reduced. Moreover, vertical rigidity can be improved by using a rubber material having a large shear elastic modulus (G), that is, a hard rubber. However, as the vertical rigidity increases, more rubber layer thickness is required to follow the rotational deformation of the superstructure. That is, increasing the vertical rigidity and satisfying the rotation function are contradictory requirements. Further, since hard rubber has low elongation performance, the allowable value for local shear strain is smaller than that of soft rubber.

  Patent document 1 by the applicant of this application discloses a seismic isolation device in which an intermediate rigid plate is embedded in the rubber layer at the center of the laminated rubber (paragraph 0050 to paragraph 0052 and FIG. 11). According to such a laminated rubber, the vertical rigidity as a whole increases, and the layer thickness of the rubber layer at the end remains the same, so that an increase in rotational rigidity is suppressed (paragraph 0024). However, this document makes no mention of partially changing the hardness of the rubber material.

JP 2004-211837 A

The present invention has been made based on the technical background as described above, and achieves the following object.
An object of the present invention is to provide a bearing that satisfies the rotation function without increasing the rubber layer thickness while exhibiting a high vertical rigidity that can be used under a high surface pressure.

The present invention employs the following means in order to achieve the above object.
That is, this invention is a laminated rubber bearing formed by alternately laminating rigid plates and rubber layers,
Consisting of a central laminated part and an outer peripheral laminated part, the number of laminated parts in the central laminated part is larger than the number of laminated parts in the outer laminated part, and each rubber layer in the outer laminated part is made softer than each rubber layer in the central laminated part Laminated rubber bearing characterized by

  According to this invention, the laminated rubber bearing has a large number of laminated layers (thickness of the rubber layer is thin) in the central laminated portion, and since the rubber material is hard, the vertical rigidity is increased and the compressive strain can be reduced. . On the other hand, in the outer peripheral laminated part where rotational deformation dominates, the number of laminated layers is small (the rubber layer is thick) and the rubber material is soft, so it is possible to follow the rotational deformation and against local shear strain. The allowable value can be increased. Therefore, the fatigue durability can be increased while increasing the vertical rigidity, so that it can be used under a high surface pressure.

It is a perpendicular direction sectional view showing an embodiment of this invention. It is a top view which reduces and shows the thing of the same embodiment. It is a vertical direction sectional view showing local shear strain by rotation. It is a bridge axis perpendicular direction sectional view showing the example which applied the thing of the embodiment to a slide bearing. It is a bridge axial direction sectional view of the slide bearing. FIG. 6 is a cross-sectional view taken along line AA in FIG. 5.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an embodiment of the present invention. The laminated rubber support 1 is made by laminating steel plates 2 and 3 which are rigid plates and rubber layers 4 and 5 so that the planar shape is rectangular or circular. FIG. 2 shows an embodiment in which the planar shape is rectangular.

  More specifically, the laminated rubber support 1 includes a central laminated portion 1a and an outer circumferential laminated portion 1b surrounding the central laminated portion 1a. The steel plate 2 has a rectangular shape similar to the conventional one having side lengths a and b substantially equal to the planar external dimensions of the entire laminated rubber support 1. The steel plate 3 has a rectangular shape having side lengths a ′ and b ′ smaller than the side lengths a and b of the steel plate 2. These large-area steel plates 2 and small-area steel plates 3 are alternately arranged such that their centers coincide with the vertical center axis of the laminated rubber bearing 1.

  The central laminated portion 1a is defined by a portion where the steel plate 2 and the steel plate 3 overlap. That is, the planar area of the central laminated portion 1a is an area where the steel plate 3 is disposed. The outer peripheral laminated portion 1b is defined by a portion where only the steel plates 2 overlap. That is, the planar region of the outer peripheral laminated portion 1b is a rectangular annular region obtained by subtracting the planar region where the steel plate 3 is disposed from the planar region where the steel plate 2 is disposed. Therefore, as can be easily understood from FIG. 1, the number of the central laminated portions 1a is larger than the number of the laminated outer peripheral portions 1b.

  Since the number of laminated layers in the central laminated portion 1a is larger than the number of laminated layers in the outer laminated portion 1b, the rubber layer 4 in the central laminated portion 1a is thinner than the rubber layer 5 in the outer laminated portion 1b. In this invention, in addition to the above points, the rubber layer 5 of the outer peripheral laminated portion 1b is made softer than the rubber layer 4 of the central laminated portion 1a.

  As described above, the laminated rubber support 1 according to the present invention has a large number of laminated central laminated portions 1a (the thickness of the rubber layer is thin) and the rubber layer 4 is hard. Can be reduced. Conversely, the outer peripheral laminated portion 1b has a small number of laminated layers (thickness of the rubber layer is thick) and the rubber layer 5 is soft, so that it can follow rotational deformation, and local shear strain (shown by a chain line in FIG. 3). The permissible value for the circled portion can be increased. Therefore, according to the laminated rubber bearing 1 of the present invention, the fatigue durability can be enhanced while increasing the vertical rigidity, and therefore it can be used under a high surface pressure.

  Here, the number of laminated layers is preferably as small as possible in order to reduce the size and cost of the laminated rubber support. In the illustrated embodiment, a configuration in which the central laminated portion 1a has four layers and the outer laminated portion 1b has two layers is employed.

Moreover, about the area | region of the center laminated part 1a, the side length (diameter in the case of a circle) which prescribes | regulates this is 1/2 (a '= a) of the side length of the steel plate 2 which prescribes | regulates the outer periphery laminated part 1b. / 2, b '= b / 2) is desirable. Regarding the hardness of the rubber layers 4 and 5, for the required performance of a general bridge, the rubber layer 4 of the central laminated portion 1a has a shear elastic modulus G value of about 1.2 N / mm ² and the outer laminated portion 1b A rubber layer 5 of about 0.8 / mm ² is applied. If the required performance is different from normal, a different combination of numbers is applied.

  The laminated rubber support 1 is made by vulcanizing and bonding the steel plates 2 and 3 and the rubber layers 4 and 5 in the same manner as a known laminated rubber. As materials for the rubber layers 4 and 5, chloroprene-based synthetic rubber or natural rubber can be used, but it is desirable to use natural rubber from the viewpoint of fatigue durability. The outer periphery of the laminated rubber support 1 is covered with a covering rubber layer 6.

  4 to 6 show an example of use in which the laminated rubber bearing 1 is incorporated as a main body (rubber rod) of a sliding bearing in a bridge. A rectangular sole plate 13 having a boss hole 14 in the center is fixed to the lower surface of the flange 12 of the bridge girder 11 (steel girder), which is an upper structure, by welding. An upper collar 15 made of a rectangular steel plate is fixed to the lower surface of the sole plate 13 with bolts 17. The upper collar 15 has a shear key 16 that fits into the boss hole 14.

  A stainless steel plate 18 as a sliding member is provided on the lower surface of the upper collar 15. The stainless steel plate 18 is fitted into a recess formed on the lower surface of the upper collar 15 so that the surface thereof is flush with the upper collar 15, and is fixed to the upper collar 15 by welding. Notches 20 and 20 having step portions 19 extending in the bridge axis direction are formed on both sides of the upper rod 15 in the bridge axis direction (X direction).

  A lower rod 21 made of a rectangular steel plate is fixed to an upper surface of the pier 22 which is a lower structure via an anchor bolt 23. Side blocks 24, 24 are detachably fixed to both sides of the lower rod 21 in the bridge axis direction via fixing bolts 25. The side block 24 has an overhang portion 26 at the upper end, and the overhang portion 26 is loosely engaged with the step portion 19 of the upper collar 15. By this engagement, the movement of the bridge girder 11 in the direction perpendicular to the bridge axis (Y direction) and the lifting movement of the bridge girder 11 are restricted.

  The laminated rubber bearing 1 according to the present invention is placed on the upper surface of the lower collar 21. The lower collar 21 is provided with a plurality of displacement prevention plates 28 for suppressing the displacement of the laminated rubber support 1 and for positioning so as to be positioned on the outer periphery of the lower end portion of the laminated rubber support 1.

  An intermediate plate 30 made of a rectangular steel plate is placed on the upper surface of the laminated rubber support 1. A Teflon (registered trademark, hereinafter the same) plate 32 as a sliding member is provided on the upper surface of the intermediate plate 30, and the Teflon plate 32 is slidably pressed against the stainless steel plate 18. The Teflon plate 32 is formed into a flat circular shape, and is fitted into a recess formed on the upper surface of the intermediate plate 30 and bonded thereto. In this state, the surface of the Teflon plate 32 protrudes from the upper surface of the intermediate plate 30.

  Both sides 31 and 31 in the bridge axis direction of the intermediate plate 30 protrude from the upper surface of the laminated rubber bearing 1. Cutouts 34, 34 are formed on both side parts 31, 31. The side blocks 24 and 24 are loosely fitted and engaged with the notches 34 and 34.

  In the sliding bearing as described above, when a horizontal load acts on the upper structure 11 due to an earthquake or the like, the upper structure 11 moves in the bridge axis direction. At that time, a horizontal load is also applied to the intermediate plate 30 through the frictional force between the stainless steel plate 18 and the Teflon plate 32. However, the intermediate plate 30 is engaged and restrained by the side block 24, so that it moves. Can not do it. Therefore, the horizontal movement of the bridge girder 11 is realized only by the sliding of the stainless steel plate 18 and the Teflon plate 32 against the frictional force, and no horizontal load is transmitted to the laminated rubber support 1, and shear deformation is not caused. It will not wake up. That is, the laminated rubber bearing 1 does not have a function of transmitting a horizontal load, but has a function of transmitting a vertical load of the upper structure 11 to the lower structure 22 and a function of following the rotation of the upper structure 11.

1: Laminated rubber bearing 1a: Central laminated portion 1b: Outer circumferential laminated portion 2: Rigid plate (steel plate)
3: Rigid plate (steel plate)
4: Rubber layer 5: Rubber layer

Claims (1)

A laminated rubber bearing in which rigid plates and rubber layers are alternately laminated,
Consisting of a central laminated part and an outer peripheral laminated part, the number of laminated parts in the central laminated part is larger than the number of laminated parts in the outer laminated part, and each rubber layer in the outer laminated part is made softer than each rubber layer in the central laminated part Laminated rubber bearing characterized by

Images