Bearings – Linear bearing – Plain bearings
Reexamination Certificate
2000-07-31
2002-07-02
Dickson, Paul N. (Department: 3613)
Bearings
Linear bearing
Plain bearings
C384S036000, C014S073500
Reexamination Certificate
active
06412982
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an elastomeric bearing installed at an upper girder of a bridge or between upper and lower parts of a building, for supporting a load in a stable manner, and more particularly, to an elastomeric bearing for supporting a high load, which can enhance stability, while supporting a higher load, and which can reduce the construction cost by reducing its own width.
2. Description of the Related Art
A conventional elastomeric bearing
100
, as shown in
FIG. 7
, includes an upper plate
200
, a lower plate
300
and an elastomeric pad
110
disposed therebetween. The elastomeric pad
110
includes a body
11
made of rubber and a plurality of reinforcement plates
112
inserted into the body
111
to be parallel in a horizontal direction.
The elastomeric pad
110
is directly installed as a single member so as to allow buckling or sliding while supporting an upper load of a girder or building. Alternatively, occasionally, the elastomeric bearing
100
shown in
FIG. 7
is advantageously used in order to control buckling or sliding of the elastomeric pad
110
in a predetermined direction or at a predetermined angle. Here, the directions of movement of the elastomeric pad
110
are controlled by installing stoppers, guides, clamps or the like at the upper plate
200
and the lower plate
300
so as to correspond to each other, thereby suppressing buckling or sliding of the elastomeric pad
110
. This technology is known well and a detailed explanation thereof will not be made.
Since the body
111
of the elastomeric pad
110
is made of rubber, buckling or sliding occurs within the elastomeric pad I
10
due to physical properties of rubber at a predetermined angle according to the direction of a load applied. Also, since the elastomeric pad
110
includes a plurality of reinforcement plates
112
, excessive deformation due to compression can be prevented. Further, if an excessive horizontal load is applied like in the event of the earthquake, the work energy is turned into the deformation energy of the rubber body
111
, thereby reducing a shock due to the horizontal load. Thus, the elastomeric pad
110
must be designed so as to operate properly with an ultimate strength of rubber. Also, the elastomeric pad
110
must accommodate a temporary overload or deformation greater than a design load without being destroyed.
If a load is applied to the conventional elastomeric pad
110
, the deformation(expansion) of the body
111
incorporating reinforcement plates
112
is somewhat suppressed. However, the body
111
between the reinforcement plates
112
may undergo expansion in every direction, that is, susceptible to deformation, thereby degrading durability and a load-supporting stress. Thus, there is a limit in improving stability while supporting a high load. Also, since the height of an elastomeric pad is proportional to the moving distance of the upper plate of a bridge, various types of elastomeric pads must be fabricated according to the moving distances of the upper plates of various bridges.
Thus, an elastomeric bearing (or elastomeric pot) shown in
FIG. 8
has been proposed and used. According to the proposed elastomeric bearing, an elastomeric bearing
100
includes an upper plate
200
, a lower plate
300
having a cylindrical hollow
310
, and an elastomeric pad
120
. The elastomeric pad
120
includes an elastomeric member
121
made of rubber and seated in the cylindrical hollow
310
of the lower plate
300
, a piston
122
inserted into the cylindrical hollow
310
to be elastically supported upwardly by the elastomeric member
121
, a sliding plate
123
fixed on the top surface of the piston
122
, for allowing smooth sliding of the upper plate
220
, and sealing means fixed to the piston
122
, for sealing the elastomeric member
121
seated in the cylindrical hollow
310
. Here, the sliding plate
123
is generally made of polytetrafluoroethylene (PTFE) resin.
The elastomeric pad
120
cannot be used as a single member in view of its structure and is necessarily used in the elastomeric bearing
100
reinforced with the upper plate
200
and the lower plate
300
.
The elastomeric bearing
100
may be embodied in various types as necessary. For example, an omni-directionally movable elastomeric bearing is shown in FIG.
8
. In the case of an omni-directionally fixed elastomeric bearing, the sliding plate
123
is removed, and the upper plate
200
and the piston
122
of the elastomeric pad
120
are integrally formed, thereby preventing the upper plate
200
from sliding in every direction, by means of the piston
122
inserted into the cylindrical hollow
310
. Also, in the case of a uni-directionally movable elastomeric bearing, guide grooves are formed at the upper plate
200
and/or the piston
122
in one direction, and separate guide pins are inserted into the guide grooves or guide pins are installed at the upper plate
200
or the piston
122
positioned at locations corresponding to the guide grooves, thereby allowing the upper plate
200
to slide in one direction along the guide grooves.
When a vertical load is applied to the elastomeric bearing
100
having the elastomeric pad
120
, the piston
122
sways in every direction so that it is buckled in every direction like the elastomeric bearing
100
shown in FIG.
7
.
In the elastomeric bearing
100
shown in
8
, since the elastomeric member
121
is sealed on the cylindrical hollow
310
of the lower plate
300
, a vertical load is applied to the elastomeric bearing
100
so that expansion does not occur even if the elastomeric member
121
is pressed. Therefore, the elastomeric bearing
100
shown in
FIG. 8
is safer than the elastomeric bearing
100
having the elastomeric pad
110
shown in
FIG. 7
, while supporting a higher load.
In the elastomeric bearing
100
shown in
FIG. 8
, since the cylindrical hollow
310
, the elastomeric member
121
and the piston
122
are circular in terms of their mechanical structures, in the case where the size of the elastomeric bearing
100
is increased for the purpose of supporting a higher load, the diameter and depth of the cylindrical hollow
310
and the width of the lower plate
300
having the cylindrical hollow
310
are increased by predetermined increment based on the Hoop's formula which is well known in the art.
The length of a beam or truss constituting a girder is tensile or elastic due to its tare, external force or a change in the temperature. Thus, in order to support the beam or truss constituting a girder, an appropriate edge distance is required considering safety.
In the case of supporting a beam or truss constituting a girder using the elastomeric bearing, with the elastomeric bearing fixed on the top surface of a bridge pier, in order to secure an appropriate edge distance, a predetermined width of the elastomeric bearing is required. Also, in order to safely support the pier or elastomeric bearing, a predetermined width of the top surface of the pier is required. If the width of the elastomeric bearing for securing an edge distance and the width of the top surface of the pier for supporting the elastomeric bearing are unnecessarily increased, the overall width of the pier must be larger than is designed, which considerably increases the construction cost. Therefore, it is necessary to determine an appropriate width of the elastomeric bearing and an appropriate width of the top surface of the pier, that is, while obtaining an edge distance and ensuring safety.
In the case of supporting a beam or truss using the elastomeric bearing
100
shown in
FIG. 8
, the elastomeric bearing
100
must have a predetermined size in order to support a sufficiently high load. However, as described above, since the size of the elastomeric bearing
100
is increased, the length and width thereof are uniformly increased. Thus, as the width of the elastomeric bearing
100
becomes greater than a predetermined length for securing the edge distance, an unnecessary in
Anderson Kill & Olick
Dickson Paul N.
Hyup Sung Industrial Co., Ltd.
Lieberstein Eugene
Meller Michael N.
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