JP2003049408A - Steel support and bridge supporting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel support movable only in a bridge axis direction normally and in case of an earthquake based on the seismic coefficient method and movable also in a right-angled direction to the bridge axis in case of an earthquake based on the ultimate horizontal strength method, and to provide a function separating type bridge supporting device jointly using the steel support and an elastic damper. SOLUTION: This steel support has a lower shoe 1 accommodating a rubber plate 15, an intermediate plate 17, and the like in a recessed part 3 provided at the center part, and fixed to a base plate 20 by bolts 41 directly or through a fixing member; lower shoe guide blocks 33a, 33b provided on the bridge axis direction side of the base plate 20 to guide the lower shoe 1; and an upper shoe 8 movably in the bridge axis direction held on to the lower shoe 1 through a sliding plate 18. The bolts 41 for fixing the lower shoe 1 to the base plate 20 directly or through the fixing member are set to such strength as to be broken when horizontal load exceeding horizontal load in case of the earthquake based on the seismic coefficient method is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel bearing installed between a lower structure and an upper structure of a bridge, and a bridge supporting device using the steel bearing and an elastic damper. is there.

[0002]

2. Description of the Related Art Conventionally, steel bearings have been generally used as bridge bearings, but steel bearings that counteract this due to an unexpectedly large earthquake force (horizontal force) in the recent Hyogoken Nanbu Earthquake. There was a case where the road was damaged, and at the same time the vertical bearing capacity was lost, resulting in a large step on the road surface and a bridge collapse. Therefore, taking this as a lesson, elastic dampers have come to be used instead of steel bearings.

However, when the elastic damper is used, the elastic damper, especially the elastic damper provided at the end fulcrum, is
Since deflection occurs in the vertical direction, vibration always occurs, and since the vertical rigidity is low, a step is generated on the road surface, which causes problems such as deterioration of traveling performance and noise, which is a problem. By using an elastic damper that supports horizontal force and a steel support as a support that supports vertical force, it is possible to implement a function-separated bearing device that separates the horizontal force support function from the vertical force support function. Has been.

FIG. 8 is a front view of an example of a conventional steel bearing, a part of which is shown in cross section (direction perpendicular to the bridge axis). FIG. 9 is a side view (direction of the bridge axis) of the same. In both figures, 61 is a lower shoe with a circular recess 62 provided in the center of the upper surface, and brackets 63 are provided on both sides (direction perpendicular to the bridge axis).
A rubber plate 66 and an intermediate plate 67 made of a metal plate such as a steel plate for preventing the bulging phenomenon of the rubber plate 66 and increasing the load bearing capacity are housed therein, and are provided on the upper surface of the intermediate plate 67. A sliding plate 68 made of a synthetic resin plate such as fluororesin is housed in the recess. 69 is a seal ring attached to the outer periphery of the intermediate plate 67.

Reference numeral 64 denotes an upper shoe which is substantially H-shaped in a plane, and is formed so that the central portion in the direction perpendicular to the bridge axis is high and both sides thereof are formed one step lower, and both sides in the bridge axis direction project outward and are respectively locked between them. The part 65 is formed. The upper shoe 64 is placed on the lower shoe 61 with the engaging portion 65 inserted between the brackets 63 of the lower shoe 61, and one piece of the upper shoe 64 is attached to the bracket 6 of the lower shoe 61.
L-shaped side block 7 fixed to 3 with bolts 71
The other piece of 0 is located on the engaging portion 65 of the upper shoe 64 and is integrally connected.

The steel bearing constructed as described above is installed between a bridge pier (abutment) which is a lower structure and a bridge girder which is an upper structure, and the vertical load is a slip between the upper shoe 64 and the lower shoe 61. The horizontal load is transmitted to the plate 68, and the horizontal load is transmitted between the locking portion 65 of the upper shoe 64 and the bracket 63 of the lower shoe 61.
The sliding plate 68 corresponds to horizontal movement in the bridge axis direction, and the rubber plate 66 corresponds to rotation.

[0007]

The steel bearing having the vertical force supporting function constructed as described above is constructed so as to be horizontally movable in the bridge axis direction, but is not horizontally movable in the direction perpendicular to the bridge axis. Since it is configured to be possible, even if an elastic damper that bears a horizontal force supporting function is provided in the bridge axis and the direction perpendicular to the bridge axis,
It was unable to follow the horizontal force in the direction perpendicular to the bridge axis during a large earthquake.

The present invention has been made to solve the above problems, and can be moved only in the bridge axis direction at all times and in the seismic intensity method earthquake, and can also be moved in the direction orthogonal to the bridge axis in the case of the earthquake resistance method. The purpose is to provide steel bearings. Another object of the present invention is to provide a function-separated bridge support device that uses the above-mentioned steel support and elastic dampers in combination.

[0009]

In the steel bearing according to the present invention, a rubber plate, an intermediate plate and the like are housed in a recess provided in the center and fixed to a base plate directly or through a fixing member by a bolt. A shoe bottom, a lower shoe guide block that is provided on the bridge axis side of the base plate and that guides the lower shoe, and an upper shoe that is movably held on the lower shoe via a slide plate in the bridge axis direction. The bolt for fixing the lower shoe to the base plate directly or via a fixing member is set to have a strength to break when a horizontal load exceeding a horizontal load during a seismic intensity earthquake is applied.

Further, in the above-mentioned steel bearing, a bolt which is inserted into a bolt insertion hole provided in the lower shoe to fix the lower shoe directly to the base plate or through a fixing member, and the bolt insertion hole in the bridge axial direction. The gap t formed between
₁ was formed to be larger than the clearance t ₂ formed between the side surface of the lower shoe and the side surface of the lower shoe guide block.

Further, the bridge support device according to the present invention is a bridge in which a support is installed between a lower structure and an upper structure, wherein the steel support is provided between the lower structure and the upper structure. And the elastic damper is installed between these steel bearings.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 is a partial sectional view of a steel bearing according to a first embodiment of the present invention in a direction perpendicular to a bridge axis, and FIG. 2 is a partial cross section in the bridge axis direction. 3 and 4 are exploded perspective views of FIG. Incidentally, bolts and nuts are omitted in FIG. In the figure, reference numeral 1 denotes a lower shoe having a flat lower surface, a central upper portion formed to have a high height and provided with circular recesses 2, and bolt insertion holes 3 provided at four corners. In addition, brackets 4a, 4b are provided on both sides of the recess 2 (in the direction perpendicular to the bridge axis) at a space L so as to project above and on both sides.
Are provided, and screw holes 5 are provided in both outer side surfaces 4 of the brackets 4a and 4b. Denoted at 6 are locking steps provided on both sides of the recess 2 (in the bridge axis direction).

Numeral 8 is an upper shoe, a central portion in the direction perpendicular to the bridge axis is formed high and a plurality of screw holes 9 are provided, and a hexagon bolt 44
Are screwed in, and both sides (the direction perpendicular to the bridge axis) are formed one step lower to form the locking step portion 10. Reference numeral 11 denotes a fitting protrusion formed on the lower surface of the upper shoe 8 in the bridge axis direction, and its width L ₁ is formed to be slightly smaller than the interval L between the brackets 4a and 4b of the lower shoe 1. Reference numeral 12 is a sliding member integrally formed on the lower surface of the fitting convex portion 11 and made of a stainless plate or the like.

Reference numeral 15 is a rubber plate, 16 is a compression ring mounted on the outer periphery of the rubber plate 15, and 17 is a concave upper surface, which is a steel plate for preventing the rubber plate 15 from bulging and increasing the load bearing capacity. The rubber plate 15, the compression ring 16, and the intermediate plate 17 are intermediate plates made of such a metal plate, and are accommodated in the recess 2 of the lower shoe 1. Then, in the concave portion provided on the upper surface of the intermediate plate 17, the sliding plate 1 made of a synthetic resin material such as a fluororesin.
8 are accommodated. The upper portion of the sliding plate 18 projects upward from the recess 2 of the lower shoe 1, and a seal ring 19 is attached to the outer periphery of the intermediate plate 17 and the sliding plate 18.

Reference numeral 21 is a first base plate having an anchor bolt insertion hole 22, and 23 is a first base plate 2.
A flat top surface that is integrally joined to the top surface of the 1 by welding or the like.
Of the second base plate 23, screw holes 24 are provided at positions corresponding to the bolt insertion holes 3 of the lower shoe 1 of the second base plate 23, and a plurality of screw holes 25 are provided on both edge sides thereof. Has been. The second base plate 2
3 may be omitted and a plurality of screw holes 24 and 25 may be provided in the first base plate 21, and in the following description, the first and second base plates 21 and 23 will be collectively referred to as the base plate 20.

Reference numerals 31a and 31b are U-shaped side blocks having bolt insertion holes 32 on the side walls corresponding to the screw holes 5 of the brackets 4a and 4b of the lower shoe 1, and the lower piece is the bracket 4a of the lower shoe 1. 4b is locked to the lower end, and the upper piece is located on the locking step 10 of the upper shoe 8. Reference numerals 33 a and 33 b are inverted L-shaped lower shoe guide blocks having bolt insertion holes 34 provided corresponding to the screw holes 25 of the base plate 20, and are provided with a step portion 35.

Next, an example of an assembling procedure of the steel bearing made of the above members will be described. First, the lower shoe 1 is placed on the base plate 20, and the bolt 41 inserted into the bolt insertion hole 3 is provided in the screw hole 24 provided in the base plate 20.
It is screwed into and fixed to the base plate 20. Next, the step portion 35 of the lower shoe guide blocks 33a and 33b is positioned on the locking step portion 6, and the bolt 42 inserted into the bolt insertion hole 34 is screwed into the screw hole 25 of the base plate 20 to attach to the base plate 20. Fix it. At this time, the upper and side surfaces of the locking step portion 6 of the lower shoe 1 and the lower shoe guide blocks 33a, 3
A slight gap is formed between the lower surface and the side surface of the step portion 35 of 3b. In addition, the bolts 41 that fix the lower shoe 1 to the base plate 20 are seismic intensity earthquakes (medium-scale earthquakes).
When a horizontal load that exceeds the horizontal load at that time is applied, the one that breaks is used.

Then, the rubber plate 15, the compression ring 16 and the intermediate plate 17 are accommodated in the recess 2 of the lower shoe 1, the sliding plate 18 is accommodated in the recess of the intermediate plate 17, and the seal ring 19 is provided on the outer periphery thereof. To arrange. And
The fitting protrusion 11 of the upper shoe 8 is fitted between the brackets 4a, 4b of the lower shoe 1 to mount the upper shoe 8 on the lower shoe 1 and bring the sliding member 12 into contact with the sliding plate 18. . Next, lower shoe 1
Lower portions of the brackets 4a and 4b of the vehicle and the locking step portion 1 of the upper shoe 8
The side blocks 31a and 31b are provided between the bracket 4 and the side blocks 31a and 31b, and the bolts 43 inserted into the bolt insertion holes 32 are attached to the bracket 4
It is screwed into the screw holes 5 of a and 4b and fixed to the lower shoe 1. At this time, a slight gap is formed between the upper pieces of the side blocks 31a and 31b and the upper shoe 8. As a result, the upper shoe 8 can move along the brackets 4a and 4b in the bridge axis direction, but the side blocks 31a, 4b in the bridge axis orthogonal direction.
It is held by 31b so that it cannot move, and the side blocks 31a and 31b prevent the floating.

The lower part of the steel bearing constructed as described above has an anchor bolt insertion hole 22 formed in the base plate 20.
Is fixed to the anchor bolt 45 provided on the bridge pier or abutment, which is a lower structure, with a nut, and the upper part is an upper structure via a hexagon bolt 44 screwed into the screw hole 9 of the upper shoe 8. It is fixed and fixed on the bridge girder.

Next, the operation of the steel bearing constructed as described above and fixed between the lower structure and the upper structure will be described. The vertical load acting on the bridge is supported by plane contact between the steel material such as the lower shoe 1 and the upper shoe 8 and the sliding plate 18, the rubber plate 15 and the like. The upper lift is supported by the side blocks 31a and 31b, the lower shoe guide blocks 33a and 33b, and the base plate 20, and is fixed to the upper and lower structures by the hexagon bolt 44 and the anchor bolt 45. Further, with respect to rotation, the recess 2 of the lower shoe 1
It is supported by the deformation of the rubber plate 15 housed inside and sealed by the intermediate plate 17.

Between the sliding member 12 provided on the upper shoe 8 and the sliding plate 18 provided on the lower shoe 1 against displacement of the bridge in the axial direction of the bridge due to temperature change, action of live load, or earthquake. Due to the sliding action of the upper shoe 8, the upper shoe 8 is guided by the brackets 4a, 4b of the lower shoe 1 and moves in the bridge axis direction to follow. At this time, since the lower shoe 1 is fixed to the base plate 20 by the bolts 41 and is restrained by the lower shoe guide blocks 33a and 33b, the lower shoe 1 hardly moves in the bridge axis direction. The amount of movement of the upper shoe 8 in the bridge axis direction is adjusted by changing the length of the sliding member 12, and thus the length of the upper shoe 8.

By the way, the bridge is repeatedly displaced in the axial direction of the bridge due to the live load.
Therefore, the bolt 41 for fixing the bolt is repeatedly subjected to a horizontal force due to a live load, which may cause fatigue and disconnection. Therefore, in the present embodiment, as shown in FIG. 4, the clearance t ₁ formed in the bridge axial direction between the bolt insertion hole 3 provided in the lower shoe 1 and the bolt 41 inserted therein is defined as follows. , greater than the gap t ₂ which is formed between the side surfaces and Shitakutsu guide block 33a, 33a stepped portion 35 of the locking stepped portion 6 of the lower shoe 1, was formed on the t _1> t _2. In this case, the bolt insertion hole 3 may be formed in an elliptical shape whose major axis is the bridge axis direction.

With this construction, even if the lower shoe 1 is displaced in the bridge axial direction, the lower shoe guide blocks 33a, 3
3b is prevented from further displacing and hitting the bolt 41, so that a horizontal load is not applied to the bolt 41 and fatigue can be prevented.

As described above, the steel bearing according to the present embodiment moves only in the bridge axis direction at all times and at the time of an earthquake, and does not move in the direction perpendicular to the bridge axis. However, the strength is selected so that the bolts 41 that fix the lower shoe 1 to the base plate 20 will break when a horizontal load that exceeds the horizontal load during the seismic intensity earthquake is applied. ) Sometimes, the horizontal load breaks the bolt 41, and the lower shoe 1 moves along the lower shoe guide blocks 33a and 33b.
Move on 0 in the direction perpendicular to the bridge axis. At this time, the lower shoe 1 is prevented from rising by the lower shoe guide blocks 33a and 33b. The amount of movement of the lower shoe 1 in the direction perpendicular to the bridge axis is determined by the base plate 20 (second base plate 23 in the figure).
It can be adjusted by changing the length in the direction perpendicular to the bridge axis.

[Second Embodiment] In the first embodiment, the lower plate 1 is attached to the base plate by the bolt 41 which is broken when a horizontal load which is inserted into the bolt insertion hole 3 exceeds a horizontal load at the seismic intensity earthquake. Although the case where the lower shoe 1 is fixed to the base plate 20 is not directly fixed to the base plate 20 by the bolts 41 as shown in FIG. A fixing member 36 made of a steel plate is arranged along the wall.
The above-mentioned bolts 41 are inserted into the plurality of bolt insertion holes 34 provided in the base plate 20, and are screwed into and fixed in the screw holes 24 provided in the base plate 20.

Also in the present embodiment, as in the case of the first embodiment, the steel bearing moves only in the bridge axis direction at all times and at the time of an earthquake, and does not move in the direction perpendicular to the bridge axis. When a horizontal load exceeding the horizontal load is applied, the bolt 41 that fixes the fixing member 36 to the base plate 20 breaks and the fixing member 36 separates, and the lower shoe 1 moves on the base plate 20 in the direction perpendicular to the bridge axis. .

As is clear from the above description, in the steel bearing according to the present invention, the upper shoe 8 moves in the bridge axis direction when the road surface expands or contracts due to temperature changes, the live load acts or an earthquake occurs. In general, the sliding surface is separated so that the lower shoe 1 can move in the direction perpendicular to the bridge axis during a earthquake-resistant earthquake in the direction perpendicular to the bridge axis, so that it can follow displacements in all directions.
It is possible to reliably follow horizontal displacement in the direction perpendicular to the bridge axis at the time of a load bearing earthquake. For this reason, it is possible to prevent the bridge from being damaged such that a step is generated on the road surface or a bridge is dropped.

[Third Embodiment] FIG. 6 is a schematic sectional view of a bridge support device according to a third embodiment of the present invention in a direction perpendicular to the bridge axis. In the figure, 50 is a bridge pier or abutment (hereinafter referred to as bridge pier) which is a lower structure, 51 is a bridge girder which is an upper structure, 52 is a main girder, and 53 is a transverse girder. A is pier 5
The steel bearing according to the first embodiment fixed between 0 and the bridge girder 51, and B is an elastic damper different from the steel bearing A fixed between the bridge pier 50 and the bridge girder 51.

FIG. 7 shows an example of the elastic damper B. 52
Is a columnar or prismatic main body, and a plurality of steel plates 53 are arranged at predetermined intervals in the vertical direction, and the spaces between and around the steel plates 53 are integrally fixed by an elastic body 54 such as rubber.
This elastic body 54 has a horizontal spring function. In addition, a material having a high damping property may be used. A thick steel plate 53 is used for the lower end portion and the upper end portion, and each has a plurality of screw holes.

Then, the main body 52 is connected to the lower plate 55.
The bolt 57, which is placed on the lower plate 55 and is inserted into the screw insertion hole provided in the lower plate 55, is screwed into the screw hole provided in the steel plate 53 at the lower end portion of the main body 52 to be integrally connected. Also, the main body 5
The upper plate 56 is placed on the upper end portion of 2, and the bolt 57 inserted through the screw insertion hole provided on the upper plate 56 is screwed into the screw hole provided on the steel plate 53 at the upper end portion of the main body 52 to integrally form. Join. Reference numeral 58 is a plurality of hexagon bolts screwed into the upper surface of the upper plate 56, and 59 is an anchor bolt provided in the bridge pier 50 and inserted into a plurality of bolt insertion holes provided in the lower plate 55.

The elastic damper B constructed as described above is
As with the steel bearing A, the lower plate 55 is attached to the pier 5
It is fixed by an anchor bolt 59 provided at 0, and the upper plate 56 is fixed to the bridge girder 51 via a hexagon bolt 58 so that it is fixed between the two. And this elastic damper B does not support a vertical load, but supports only a horizontal load.

Next, the operation of the present embodiment configured as described above will be described. When the bridge girder 51 is displaced in the bridge axis direction due to temperature change, live load action, or earthquake, the steel bearing A moves the upper shoe 8 in the bridge axis direction as described above, and the elastic damper B also elastically deforms and follows this. As to the displacement of the bridge girder 51 in the direction perpendicular to the bridge axis due to the earthquake in the direction perpendicular to the bridge axis, the steel bearing A is not displaced with respect to the seismic intensity earthquake as described above.

Further, when the bridge girder 51 is displaced in the bridge axis direction during a large earthquake (conservative earthquake), it follows the same action as described above. With respect to the displacement in the direction perpendicular to the bridge axis, the steel bearing A moves in the direction perpendicular to the bridge axis when the bolt 41 that fixes the lower shoe 1 to the base plate 20 directly or through the fixing member 36 breaks, and the elastic damper B Also elastically deforms and follows this.

As is clear from the above description, in the present embodiment, mainly vertical loads such as dead loads and live loads are supported by the steel bearing A having extremely high vertical rigidity, and are deformed during an earthquake. The elastic damper B having damping performance and horizontal spring characteristics (horizontal damper function) is configured to support mainly horizontal loads such as absorption of energy and energy,
It is the one that separates each state so that it can exert its function.

Then, a steel bearing A is mounted on the bridge piers and abutments.
Is installed and the elastic damper B is installed separately from it, so it is possible to reliably follow horizontal loads in all directions during an earthquake, and when the horizontal load disappears, it will return to its original state. be able to. Further, if a steel support having high rigidity is installed at the end fulcrum, it is possible to prevent problems such as a step being generated on the road surface at any time to reduce the running performance and noise.

In the above description, the case where the elastic damper as shown in FIG. 7 is used is shown, but the present invention is not limited to this, and an elastic damper having another structure may be used. Further, in the above description, the case where the steel bearings are installed at both end fulcrums and one rubber bearing is installed between these steel bearings is shown, but the installation place and the number of the steel bearings and the elastic dampers are also set. It can be changed appropriately.

[0037]

In the steel bearing according to the present invention, a rubber plate, an intermediate plate, and the like are housed in a recess provided in the center, and a lower shoe which is fixed to the base plate directly or by a fixing member and a base plate. Has a lower shoe guide block that is provided on the bridge axis side of the lower shoe and that guides the lower shoe, and an upper shoe that is movably held on the lower shoe via a sliding plate in the bridge axis. Since the bolts that are fixed directly to or through the fixing members are set to have a strength that breaks when a horizontal load that exceeds the horizontal load during a seismic intensity earthquake is applied, the following effects can be obtained.

That is, when the road surface expands or contracts due to a change in temperature, or when a live load is applied, or an earthquake occurs, the upper shoe moves in the axial direction of the bridge and follows them, and at the time of an earthquake-resistant earthquake in the direction perpendicular to the bridge, the lower shoe bridge The sliding surface is separated so that it can move in the direction perpendicular to the axis so that it can follow displacements in all directions, so it is possible to reliably follow horizontal loads in the direction perpendicular to the bridge axis during a load bearing earthquake. You can For this reason, it is possible to prevent the bridge from being damaged such that a step is generated on the road surface or a bridge is dropped.

Further, it is formed between a bolt which is inserted into a bolt insertion hole provided in the lower shoe and which fixes the lower shoe directly to the base plate or through a fixing member, and a bolt axial direction of the bolt insertion hole. The clearance t ₁ is defined as the clearance t formed between the side surface of the lower shoe and the side surface of the lower shoe guide block.
_Since it is formed larger than ₂ , fatigue of the bolt due to repeated horizontal load can be prevented.

Further, the bridge support device according to the present invention is a bridge in which a support is installed between a lower structure and an upper structure, wherein the steel support is provided between the lower structure and the upper structure. Since the elastic damper was installed separately from these steel bearings, it is possible to reliably follow horizontal loads in all directions, and by installing a steel bearing with high rigidity at the end fulcrum, It is possible to prevent problems such as a step being generated on the road surface at all times to deteriorate the traveling performance and noise.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a steel bearing according to a first embodiment of the present invention in a direction perpendicular to a bridge axis.

FIG. 2 is a partial cross-sectional view in the bridge axis direction of FIG.

FIG. 3 is an exploded perspective view of FIG.

FIG. 4 is an enlarged view of a main part of FIG.

FIG. 5 is a sectional view showing a main part of a steel bearing according to a second embodiment of the present invention in a direction perpendicular to a bridge axis.

FIG. 6 is a schematic cross-sectional view of a bridge support device according to a third embodiment of the present invention in a direction perpendicular to the bridge axis.

7 is a vertical cross-sectional view of an example of the elastic damper of FIG.

FIG. 8 is a partial cross-sectional view of a conventional steel bearing in the direction perpendicular to the bridge axis.

9 is a partial cross-sectional view in the bridge axis direction of FIG.

[Explanation of symbols]

A steel bearing B Elastic damper 1 lower shoe 2 recess 4a, 4b bracket 6 locking step 8 Kamito 11 Fitting convex part 12 sliding members 15 rubber plate 17 Intermediate plate 18 sliding plates 20 base plate 31a, 31b Side block 33a, 33b Lower shoe guide block 36 Fixing member 41 bolts 50 piers 51 bridge girder

Continued front page    (71) Applicant 592074049             Kureha Steel Co., Ltd.             5-4-41 Takeshima, Nishiyodogawa-ku, Osaka-shi, Osaka (71) Applicant 000103644             Oiles Industry Co., Ltd.             1-3-2 Shibadaimon, Minato-ku, Tokyo (71) Applicant 000175582             Sankyo Oilless Industry Co., Ltd.             5-1-1 Nisshin-cho, Fuchu-shi, Tokyo (72) Inventor Takashi Harada             2-1, Shiraishi-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             Inside Hon Foundry Co., Ltd. F term (reference) 2D059 AA37 GG01

Claims (3)

[Claims] A rubber plate, an intermediate plate and the like are housed in a recess provided in the center, and a lower shoe which is fixed to the base plate directly or through a fixing member and a bridge shaft side of the base plate. A lower shoe guide block that guides the lower shoe and an upper shoe that is movably held in the bridge axis direction on the lower shoe via a slide plate, and the lower shoe is directly or fixed to a base plate. A steel bearing characterized in that the bolts that are fixed through are set so that they will break when a horizontal load that exceeds the horizontal load during the seismic intensity method is applied. 2. A bolt which is inserted into a bolt insertion hole provided in the lower shoe and which fixes the lower shoe to the base plate directly or via a fixing member, and the bolt which is formed between the bolt insertion hole and the bridge axial direction. The steel bearing according to claim 1, wherein the clearance t ₁ is formed larger than the clearance t ₂ formed between the side surface of the lower shoe and the side surface of the lower shoe guide block. 3. A bridge in which a bearing is installed between a lower structure and an upper structure, wherein the steel bearing according to claim 1 or 2 is installed between the lower structure and the upper structure. At the same time, an elastic damper is installed between the steel bearings to support the bridge.