JP2020117999A - Sliding base isolation device and bridge - Google Patents

Abstract

To provide a sliding base isolation device capable of exerting suitable functions depending on respective earthquake levels and capable of inhibiting an upper structure and lower structure from being damaged at the time of a large earthquake, and a bridge comprising the sliding base isolation device, especially, as a fixed bearing.SOLUTION: A sliding base isolation device 40 including an upper shoe 41 and lower shoe 42 and a slider 48 slidable between the shoes includes a pair of movement direction limitation jigs 45 across the upper shoe 41 and lower shoe 42. The pair of movement direction limitation jigs are fixed on one of the upper shoe 41 or lower shoe 42 using knockoff bolts 60 having breaking parts 64 that are broken when horizontal force equal to or larger than a first predetermined value is applied, and are not fixed on the other of the upper shoe 41 or lower shoe 42. When the knockoff bolts 60 are not broken, a relative movement direction of the upper shoe 41 to the lower shoe 42 is limited by the pair of movement direction limitation jigs 45. When the knockoff bolts 60 are broken, the relative movement direction of the upper shoe 41 to the lower shoe 42 is not limited.SELECTED DRAWING: Figure 3

Description

The present invention relates to a slip isolation device and a bridge including the slip isolation device.

In Japan, which is an earthquake-prone country, various types of seismic resistance are being applied to various structures such as buildings, bridges, elevated roads, and detached houses, such as technology to withstand seismic force and technology to reduce seismic force entering structures. Technology, seismic isolation technology and seismic control technology have been developed and applied to various structures. Above all, the seismic isolation technology is a technology for reducing the seismic force itself entering the structure, and therefore the vibration of the structure during an earthquake is effectively reduced. An outline of this seismic isolation technology is to interpose a seismic isolation device between the lower structure and the upper structure to reduce the transmission of vibration of the lower structure due to an earthquake to the upper structure and to prevent the vibration of the upper structure. It reduces the amount and guarantees structural stability.

There are various types of seismic isolation devices such as a lead rubber laminated rubber bearing device, a high damping laminated rubber bearing device, a combined rubber bearing and damper device, and a sliding seismic isolation device. Among them, there are two types of slide seismic isolation devices, a plane slide seismic isolation bearing and a spherical slide seismic isolation bearing.The plane slide seismic isolation bearing has no restoring force, but the spherical slip seismic isolation bearing has restoring force. It has a self-centering function. Here, an example of the spherical slide base isolation bearing will be described, and its configuration will be described. The upper and lower shoes provided with a sliding surface having a curvature, and the respective shoes provided between the upper and the lower shoes. And a slider having an upper surface and a lower surface having the same curvature as that of each shoe, and this type of sliding seismic isolation device is called a double concave type seismic isolation device. Sometimes. In addition, as another form, for example, there is a slide seismic isolation device in which a slider is fixed to the upper shoe and the upper shoe and the slider slide against the lower shoe. It is also called a seismic isolation device.

By the way, the magnitude (level) of an earthquake includes level 1 in which the probability of occurrence in the near future is high, but damage is limited to small and medium-scale, and level 2 in which the probability of occurrence is not high but may cause major damage. In addition, recently, there is a case in which an earthquake that has a very low probability of occurrence but may cause serious damage is assumed to be level 3 and is assumed to be about 1.5 times the level 2 earthquake motion. It should be noted that Level 1 and Level 2 correspond to medium and large earthquakes, respectively, and Level 3 is not specified in the design standard, but is positioned as the largest earthquake level set when considering the worst case. Has been. In this specification, the level 3 earthquake may be referred to as a major earthquake, or both the level 2 and level 3 earthquakes may be referred to as a major earthquake.

If the seismic isolation device is designed assuming level 1 seismic motion, the level 2 seismic motion is an unexpected earthquake, and if the slip seismic isolation device is designed for level 2 seismic motion, the level is 3 Although the earthquake motion is an unexpected earthquake, when such an unexpected earthquake occurs, the conventional relative displacement of the lower structure and the upper structure causes the critical deformation in the conventional slip isolation device. There is a possibility of exceeding. When the relative displacement amount of the lower structure and the upper structure exceeds the limit deformation amount, for example, the upper structure may fall off from the upper shoe. In response to such a problem, when an unexpected earthquake occurs, the slider slides on the sliding surface, and the lower shoe and the upper shoe make a large horizontal relative displacement, resulting in a ring shape on the lower shoe or the upper shoe. There has been proposed a sliding bearing that restricts further relative displacement between the lower shoe and the upper shoe by the stopper abutting from the outside in the horizontal direction (see, for example, Patent Document 1).

JP, 2015-209730, A

According to the sliding bearing described in Patent Document 1, when an unexpected earthquake occurs, the horizontal relative displacement amount between the lower shoe and the upper shoe can be restricted by the stopper, so that the sliding bearing is fail-safe. A function can be added, excessive relative displacement of the lower structure and the upper structure in the horizontal direction can be regulated, and dropping of the upper structure from the upper shoe can be eliminated.

Here, Patent Document 1 describes an embodiment in which the sliding bearing is provided between a bridge pier (lower structure) and a bridge girder (upper structure) of a girder bridge. Although this description example shows an example of movement in the direction orthogonal to the bridge axis, generally, there are a fixed bearing that absorbs only the rotation of the upper structure and a movable bearing that absorbs the rotation and expansion and contraction of the upper structure, In a plurality of bridge piers (including abutments) arranged apart from each other in the bridge axis direction, a movable bearing and a fixed bearing are installed, and a bridge girder is supported by each bearing. With this configuration, the movable bearing can handle expansion and contraction in the bridge axis direction due to temperature changes in the upper structure including the main girder and live load, while the bridge is always in service when combined with a fixed bearing and a movable bearing. Performance is guaranteed.

As described above, there are multiple levels of earthquakes. For example, in level 1 earthquake motion, relative movement of the upper shoe to the lower shoe that constitutes the fixed bearing is not allowed in the bridge axis direction, and a large earthquake such as a level 2 earthquake is not allowed. By permitting relative movement in various directions including the bridge axis direction and the bridge axis direction, it becomes possible to prevent damage to the piers during a large earthquake. In addition, the movable bearing should allow relative movement of the upper shoe to the lower shoe in the bridge axis direction at all times, while allowing relative movement in various directions in the same manner as the fixed bearing in the event of a large earthquake. With this, in combination with the action of the fixed bearing, damage to the bridge, especially to the pier, can be suppressed.

However, although Patent Document 1 describes a ring-shaped stopper having a fail-safe function, a sliding seismic isolation device that constitutes a fixed bearing, a movable bearing, etc. exerts a suitable function according to each earthquake level. Therefore, there is no disclosure of means for suppressing damage to the upper structure and the lower structure in the event of a large earthquake.

The present invention has been made in view of the above problems, and can exhibit suitable functions according to each earthquake level, and can prevent damage to the upper structure and the lower structure during a large earthquake. It is an object of the present invention to provide a seismic isolation device and a bridge having the sliding seismic isolation device, in particular, for a movable bearing.

In order to achieve the above object, one aspect of the slip isolation device according to the present invention is:
A sliding seismic isolation device having an upper shoe and a lower shoe, and a slider slidable between the upper shoe and the lower shoe,
A pair of movement direction regulating jigs straddling the upper shoe and the lower shoe are ruptured when a horizontal force of a first predetermined value or more acts on one of the upper shoe and the lower shoe. It is fixed by a knock-off bolt having a part, and is not fixed to the other of the upper shoe or the lower shoe,
When the knock-off bolt is not broken, the relative movement direction of the upper shoe to the lower shoe is regulated by the pair of movement direction regulating jigs,
When the knock-off bolt is broken, the relative movement direction of the upper shoe with respect to the lower shoe is not restricted.

According to this aspect, when the horizontal force equal to or more than the first predetermined value does not act, one of the upper shoe and the lower shoe is fixed with the knock-off bolt through the movement direction restricting jig, and the upper shoe and the lower shoe are secured. One of the other is not fixed to the pair of movement direction regulating jigs and is movable by using the pair of movement direction regulating jigs as guides. It is possible to allow the relative movement of the lower shoe while regulating the relative movement direction thereof. On the other hand, when a horizontal force equal to or greater than the first predetermined value is applied, the knock-off bolt breaks, so that the pair of movement direction regulation jigs are completely disengaged from the upper shoe and the lower shoe, and the upper shoe moves relative to the lower shoe. Since there is no restriction on the direction, the upper shoe can freely move relative to the lower shoe in the free direction (360° direction). The "relative movement of the upper shoe to the lower shoe" includes both movement of the upper shoe with respect to the lower shoe and movement of the lower shoe with respect to the upper shoe.

Here, examples of the “horizontal force having a first predetermined value” include a horizontal force that acts during a level 2 earthquake or a level 3 earthquake. The slip isolation device according to this aspect can be applied to any structure such as a bridge, an elevated road, a house, etc., but is preferably applied to a movable bearing of the bridge. When the horizontal force of the first predetermined value is set as the horizontal force in the case of a large earthquake such as a level 2 earthquake, in the case of constant or level 1 earthquake, the relative amount of the upper shoe to the lower shoe in the bridge axis direction, etc. Only movement is allowed and mobile bearings are maintained. On the other hand, when a horizontal force equal to or greater than the first predetermined value is applied, the knock-off bolt is broken, and the pair of movement direction restricting jigs are completely disengaged from the upper shoe and the lower shoe, which causes the upper shoe to move against the lower shoe. By moving the upper structure including the bridge girder supported by the upper shoe, the seismic isolation function of the slip isolation device is exerted. Also, for example, when an unexpected level 3 earthquake occurs, the knock-off bolts are also broken, and the pair of movement direction restricting jigs are completely disengaged from the upper shoe and the lower shoe, and the upper shoe against the lower shoe is removed. Since there is no restriction on the direction of movement and the upper shoe can move freely in any direction, it is possible to effectively prevent damage (damage) to the lower structure due to horizontal force due to an unexpected Level 3 earthquake. be able to.

Further, in another aspect of the slip isolation device according to the present invention, the movement direction restricting jig has a U-shaped cross section for sandwiching the ends of the upper shoe and the lower shoe. And

According to this aspect, since the left and right ends of the upper shoe and the lower shoe are respectively sandwiched by the pair of movement direction restricting jigs having a U-shaped cross section, seismic motion in the vertical direction and For the flexural vibrations associated with it, and for the lifting force that can be generated due to the overturning moment at the top of the pier (installation position of the seismic isolation device) due to the eccentricity of the center of gravity, such as a curved girder. , It is possible to suppress the risk of falling the upper shoe from the lower shoe.

In addition, one aspect of the bridge according to the present invention is
The slip isolation device,
An upper structure and a lower structure in which the slip isolation device is interposed as a movable bearing,
It is characterized in that the pair of moving direction regulating jigs facing each other are arranged in a direction perpendicular to the bridge axis on the upper surface of the lower structure.

According to this aspect, since the slip isolation device of the present invention forms the movable bearing, for example, at the time of a normal earthquake or a level 1 earthquake, the function of the movable bearing is maintained, and a large earthquake such as a level 2 earthquake occurs. In this case, the upper shoe moves relative to the lower shoe in a free direction, so that the seismic isolation performance of the slip isolation device can be exhibited. In addition, even when an unexpected Level 3 earthquake occurs, by allowing the upper shoe to move freely relative to the lower shoe, the upper structure when the horizontal force from the Level 3 earthquake acts on the upper structure It is possible to effectively suppress the damage to the lower structure due to the shearing force caused by the vibration of.

As can be understood from the above description, according to the slip isolation device and the bridge of the present invention, it is possible to exhibit a suitable function in accordance with each earthquake level, and it is possible to realize the upper structure and the lower structure at the time of a large earthquake. It is possible to prevent damage.

It is a side view of an example of the bridge concerning an embodiment. It is a top view of an example of the slip isolation device concerning an embodiment. It is a III-III arrow line view of FIG. 2, Comprising: It is a longitudinal cross-sectional view of an example of the slip isolation device which concerns on embodiment. It is an enlarged view of the IV section of FIG. It is a perspective view of an example of the slip isolation device concerning an embodiment. It is the longitudinal cross-sectional view which looked at the sliding base isolation device which concerns on embodiment between the upper structure and the lower structure as a movable bearing in the bridge axial direction. It is a figure of a relative displacement of an upper shoe to a lower shoe and a horizontal force at the time of an earthquake, and is a figure showing the horizontal force at the time of a first knock off bolt and a second knock off bolt breaking. FIG. 6 is a plan view showing a state where the upper shoe is relatively moved in the bridge axis direction with respect to the lower shoe in a state where the second knock-off bolt is not broken in the slip isolation device (movable bearing) according to the embodiment. FIG. 9 is a view taken along the line IX-IX in FIG. 8, and is a vertical cross-sectional view showing a state in which the upper shoe is relatively moving in the bridge axis direction with respect to the lower shoe. FIG. 10 is a perspective view corresponding to FIGS. 8 and 9. FIG. 6 is a perspective view showing a state in which the second knock-off bolt is broken in the sliding seismic isolation apparatus (movable bearing) according to the embodiment, and the upper shoe moves relative to the lower shoe in a free direction. It is a top view of an example of the slide base isolation device used as a fixed bearing. FIG. 13 is a view taken in the direction of arrows XIII-XIII in FIG. 12, and is a vertical cross-sectional view of an example of a sliding base isolation device serving as a fixed bearing. It is an enlarged view of the XIV part of FIG. It is a perspective view of an example of the sliding base isolation device used as a fixed bearing. It is the longitudinal cross-sectional view which looked at the sliding base isolation device used as a fixed bearing between the upper structure and the lower structure in the bridge axis direction. FIG. 6 is a perspective view showing a state where the first knock-off bolt is broken and the upper shoe is relatively moved in the bridge axis direction with respect to the lower shoe in the sliding base isolation device serving as the fixed bearing. FIG. 7 is a perspective view showing a state in which the second knock-off bolt is broken and the upper shoe moves relative to the lower shoe in a free direction in the sliding base isolation device serving as the fixed bearing.

Hereinafter, a bridge according to an embodiment and a slip isolation device according to an embodiment that forms a movable bearing of the bridge will be described with reference to the accompanying drawings together with a slip isolation device that forms a fixed bearing of the bridge. In the present specification and the drawings, substantially the same components may be denoted by the same reference numerals to omit redundant description.

[Bridge and slip isolation device according to the embodiment]
First, an example of the bridge according to the embodiment and an example of the slip isolation device according to the embodiment will be described with reference to FIGS. 1 to 11. Here, FIG. 1 is a side view of an example of the bridge according to the embodiment, and FIG. 2 is a plan view of an example of the slip isolation device according to the embodiment. 3 is a view in the direction of arrows III-III in FIG. 2, which is a vertical cross-sectional view of an example of the slip isolation device according to the embodiment, and FIG. 4 is an enlarged view of section IV in FIG. 3. .. FIG. 5 is a perspective view of an example of the slip isolation device according to the embodiment, and FIG. 6 shows the slip isolation device according to the embodiment as a movable bearing interposed between the upper structure and the lower structure. It is the longitudinal cross-sectional view which looked at the state which is doing in the bridge axis direction.

As shown in FIG. 1, a bridge 100 is a sliding seismic isolation device 30 that is a fixed bearing for a plurality of piers 20 (lower structure) made of, for example, reinforced concrete and arranged at intervals in the bridge axial direction. It is formed by supporting the upper structure 10 through a sliding base isolation device 40 which is a movable bearing. In the illustrated example, one continuous upper structure 10 is supported by five bridge piers 20, and among the five bridge piers 20, a fixed bearing 30 is arranged at the top of one bridge pier 20. The movable bearings 40 are arranged at the tops of the other four piers 20, but the number of the piers 20 supporting one superstructure 10 and the number of fixed bearings 30 are various.

As shown in FIG. 2, the sliding base isolation device 40 forming the movable bearing of the bridge 100 has an upper shoe 41, a lower shoe 42, and a slider 48 slidable between the upper shoe 41 and the lower shoe 42. ..

Both the upper shoe 41 and the lower shoe 42 are made of rolled steel for welding steel (SM490A, B, C, or SN490B, C, or S45C), or SUS material, cast steel, cast iron, or the like. The lower surface of the upper shoe 41 has a housing groove 41b in which a spherical surface above the slider 48 having a substantially hemispherical shape is housed and fixed, and a portion above the slider 48 is fitted into the housing groove 41b. On the other hand, the upper surface of the lower shoe 42 is a sliding surface 42b on which the lower surface (the surface having a curvature close to the flat surface) of the slider 48 having a substantially hemispherical shape slides, and the sliding surface 42b has a sliding surface made of stainless steel. A plate (not shown) or the like is fixed. Further, a stopper ring 43 for preventing the slider 48 from falling off is provided on the outer periphery of the lower shoe 42.

As described above, in the sliding seismic isolation device 40 of the illustrated example, the slider 48 is fixed to the upper shoe 41, and the slider 48 slides with respect to the lower shoe 42. The single concave type or the single pendulum type seismic isolation apparatus. However, the seismic isolation device may be such that the slider is fixed to the lower shoe and the slider slides on the lower sliding surface of the upper shoe. Furthermore, with a double-concave type in which the slider slides on both the upper and lower shoes, or a triple-concave type with more concaves in the double concave, or a seismic isolation device with more concaves. It may be.

The slider 48 has a substantially hemispherical shape with a lower surface having a curvature, and similarly to the upper shoe 41 and the like, it is a rolled steel material for welding steel (SM490A, B, C, or SN490B, C, or S45C), or SUS. It is made of steel, cast steel, cast iron or the like.

As clearly shown in FIG. 3, the left and right ends of the upper shoe 41 and the lower shoe 42 are fixed to each other by a pair of movement direction restricting jigs 45 extending over the upper shoe 41 and the lower shoe 42. More specifically, a recess 41a is provided above the end of the upper shoe 41, and a recess 42a is provided below the end of the lower shoe 42. A U-shaped steel movement direction restricting jig 45 is fitted from above and below to sandwich the ends of the upper and lower shoes 41 and 42.

As shown in FIG. 3, when the movement direction restricting jig 45 holds the ends of the upper shoe 41 and the lower shoe 42, the moving direction restricting jig 45 and the upper shoe 41 are not fixed, and the moving direction restricting jig 45 is not fixed. 45 and the lower shoe 42 are fixed by a second knock-off bolt 60 (an example of the “knock-off bolt” in the movable bearing 40).

As shown in FIG. 4, the second knock-off bolt 60 includes a steel rod 61 having a fractured portion 64 with a reduced diameter, and a nut 62 screwed to a screw thread formed at the upper and lower ends of the steel rod 61. , 63 and. The steel rod 61 is inserted through bolt holes provided in both the lower shoe 42 and the movement direction restricting jig 45, and nuts 62 and 63 are tightened at the upper and lower ends of the steel rod 61 to move the lower shoe 42. The direction regulating jig 45 is fixed.

As shown in FIG. 5, in the sliding seismic isolation device 40 of the illustrated example, the left and right ends of the upper shoe 41 are engaged by the movement direction restricting jig 45 so as to be movable in a certain direction, and the lower shoe 42 is The left and right ends are fixed by a movement direction restricting jig 45 and three second knock-off bolts 60, respectively.

As shown in FIG. 6 in which the movable bearing 40 is interposed between the lower structure 20 and the upper structure 10, the bridge pier 20 is viewed from the bridge axis direction, as shown in FIG. Two movable bearings 40 are fixed. A steel base plate (not shown) with an anchor bolt is fixed to the top end of the pier 20 by embedding the anchor bolt in the pier 20, and the movable bearing 40 is bolted to the base plate. It is fixed by

As shown in FIG. 6, in the movable bearing 40, a pair of movement direction restricting jigs 45 for fixing the upper shoe 41 and the lower shoe 42 so as to be movable in the bridge axis direction are provided on the upper surface of the bridge pier 20 which is the lower structure. It is arranged in a right angle direction.

The upper structure 10 is composed of a steel main girder 11 formed of I-shaped steel having upper and lower flanges and a web, and a steel cross girder 12 connecting the webs of the left and right main girders 11 to each other. A reinforcing rib (not shown) may be projected from the web, and the reinforcing rib and the cross beam 12 may be bolted to each other via a splice plate (not shown). Reinforcing ribs may be attached at intervals. Further, the upper structure 10 is not limited to the combination of the main girder 11 and the cross girder 12 made of the I-shaped steel in the illustrated example, and may be formed of a main girder or a box girder of a truss structure, a concrete girder, or the like.

As shown in FIG. 6, when the horizontal force P at the time of an earthquake acts on the movable bearing 40, it acts as a shearing force on the second knock-off bolt 60 extending in the vertical direction.

Further, due to vertical seismic motions and flexural vibrations associated therewith, and due to the overturning moment at the top end of the pier 20 due to the center of gravity becoming an eccentric portion such as a curved girder, an upward lift is applied to the movable bearing 40. Can act. In the illustrated movable bearing 40, since the left and right ends of the upper shoe 41 and the lower shoe 42 are respectively clamped by the pair of movement direction restricting jigs 45 having a U-shaped cross section, It is possible to suppress the risk of the upper shoe 41 dropping off from the lower shoe 42 against the upward lift force that may act due to these various factors.

In addition to the shape of the moving direction regulating jig having a U-shaped cross section as in the illustrated example, for example, the cross section has an L shape, and the lower part and the lower shoe 42 are The second knock-off bolt 60 may be fixed in a configuration similar to that of the illustrated example, and the upper side thereof may not be fixed to the side surface of the upper shoe 41. As still another form, an upper part thereof is not fixed to the side surface of the upper shoe 41 and a lower part thereof is fixed to the side surface of the lower shoe 42 by a second knock-off bolt 60 via a flat plate-shaped movement direction restricting jig. May be

In the movable bearing 40, the upper shoe 41 is not fixed to the pair of moving direction regulating jigs 45, and the relative movement of the upper shoe 41 in the bridge axis direction with respect to the lower shoe 42 is performed using the pair of moving direction regulating jigs 45 as guides. Is allowed. Therefore, when the upper structure 41 including the main girder 11 expands and contracts in the bridge axis direction due to the temperature change, the upper structure 41 relatively moves in the bridge axis direction with respect to the lower structure 42, so that the upper structure It is possible to deal with expansion and contraction of the body 10 in the bridge axis direction.

Here, FIG. 7 shows a relationship diagram of the relative displacement amount of the upper shoe 41 with respect to the lower shoe 42 and the horizontal force at the time of the earthquake, in which the first knock-off bolt 50 and the second knock-off bolt 60 break. It also shows the horizontal force. The first knock-off bolt 50 is a knock-off bolt included in the fixed bearing 30 (see FIG. 13 and the like) described below. Here, the breaking strength of both knock-off bolts will be described.

In FIG. 7, the level 1 earthquake, the level 2 earthquake, and the level 3 earthquake are indicated by P1, P2, and P3, respectively, and the maximum displacement that interferes with the stopper ring due to the relative displacement between the upper and lower shoes is umax, and the first knock-off is performed. The relative displacement at which the bolt breaks is u2, and the relative displacement at which the second knock-off bolt breaks is u3. In the fixed bearing 30 shown in FIG. 13 and the like, the breaking strength of the breaking portion 54 of the first knock-off bolt 50 is set as the horizontal force P2 (an example of the second predetermined value) of the level 2 earthquake, and the movable bearing 40 The breaking strength of the breaking portion 64 of the second knock-off bolt 60 included in the fixed bearing 30 is set as the horizontal force P3 (an example of the first predetermined value) of the level 3 earthquake. The seismic level and the breakage of each knock-off bolt can be set as appropriate, and the first knock-off bolt 50 is broken by the horizontal force P1 of the level 1 earthquake and the second knock-off bolt 60 is broken by the horizontal force P2 of the level 2 earthquake. It may be set to break. Further, each relative displacement amount and each horizontal force at each earthquake, u1 and P1, u2 and P2, u3 and P3, are appropriately set depending on the earthquake motion applied at the time of design, the place where the bridge 100 is constructed, and the like. It

Next, a mode of relative movement of the upper shoe 41 with respect to the lower shoe 42 in the movable bearing 40 will be described with reference to FIGS. To do. Here, FIG. 8 shows a state in which the first knock-off bolt is not broken and the upper shoe is relatively moving in the bridge axis direction with respect to the lower shoe in the slip isolation device (movable bearing) according to the embodiment. It is a top view. FIG. 9 is a view taken along the line IX-IX in FIG. 8, and is a vertical cross-sectional view showing a state in which the upper shoe is relatively moving in the bridge axis direction with respect to the lower shoe, and FIG. FIG. 10 is a perspective view corresponding to FIGS. 8 and 9. Further, FIG. 11 is a perspective view showing a state in which the second knock-off bolt is broken in the slip isolation device (movable bearing) according to the embodiment, and the upper shoe moves relative to the lower shoe in a free direction. It is a figure.

As shown in FIGS. 8 to 10, when the level 1 earthquake, the level 2 earthquake, or the expansion/contraction in the bridge axis direction due to the temperature change of the upper structure 10, the second knock-off bolt 60 is broken. However, since the fixed state of the lower shoe 42 and the movement direction restricting jig 45 is maintained, the main girder 11 and the upper shoe 41, which are bolt-bonded to each other, are moved by the slider 48 sliding on the lower shoe 42. The pair of left and right movement direction restricting jigs 45 serve as guides and can move in the bridge axis direction. That is, the upper shoe 41 is relatively movable in the bridge axis direction with respect to the lower shoe 42. However, since the stopper ring 43 is provided on the outer periphery of the sliding surface of the lower shoe 42, it is possible to prevent the slider 48 from sliding excessively and falling off.

On the other hand, as shown in FIG. 11, when the second knock-off bolt 60 breaks due to a level 3 earthquake, the upper shoe 41 and the lower shoe 42 are completely unlocked. Therefore, when a large earthquake of level 3 occurs, it is possible to allow the upper shoe 41 to move freely in the free direction with respect to the lower shoe 42. As a result, the horizontal force due to the level 3 earthquake is suppressed from acting on the upper structure 10 via the movable bearing 40, and due to the seismic isolation effect, the horizontal force due to the level 3 earthquake acts on the upper structure 10. It is possible to suppress the shearing force caused by the vibration of the upper structure 10 and effectively prevent the lower structure 20 from being damaged.

[Example of fixed bearing for bridge]
Next, an example of a fixed bearing applied together with the movable bearing 40 in the bridge 100 shown in FIG. 1 will be described with reference to FIGS. 12 to 18. Here, FIG. 12 is a plan view of an example of a sliding base isolation device serving as a fixed bearing, and FIG. 13 is a view taken along the arrow XIII-XIII of FIG. 12, showing an example of a sliding base isolation device serving as a fixed bearing. 14 is a vertical cross-sectional view of FIG. 14, and FIG. 14 is an enlarged view of the XIV portion of FIG. 13. FIG. 15 is a perspective view of an example of a sliding base isolation device serving as a fixed bearing, and FIG. 16 is a sliding base isolation device serving as a fixed bearing interposed between an upper structure and a lower structure. It is the longitudinal cross-sectional view which looked at the state in the bridge axis direction.

In the bridge 100 shown in FIG. 1, of the five bridge piers 20 supporting one continuous upper structure 10, a fixed bearing 40 is arranged at the top end of one bridge pier 20.

As shown in FIG. 12, the sliding base isolation device 30 forming the fixed bearing of the bridge 100 has an upper shoe 31 and a lower shoe 32, and a slider 38 slidable between the upper shoe 31 and the lower shoe 32. .. The lower surface of the upper shoe 31 has a housing groove 31b in which a spherical surface above the slider 38 having a substantially hemispherical shape is housed and fixed, and a part above the slider 38 is fitted into the housing groove 31b. On the other hand, the upper surface of the lower shoe 32 is a sliding surface 32b on which the lower surface (sliding surface having a curvature) of the substantially hemispherical slider 38 slides. A stopper ring 33 is provided on the outer circumference of the lower shoe 32 to prevent the slider 38 from falling off.

As shown clearly in FIG. 13, the left and right ends of the upper shoe 31 and the lower shoe 32 are fixed to each other by a pair of movement direction restricting jigs 35 that straddle the upper shoe 31 and the lower shoe 32. More specifically, a recess 31a is provided above the end of the upper shoe 31 and a recess 32a is provided below the end of the lower shoe 32. A U-shaped steel movement-direction restricting jig 35 is fitted from above and below to sandwich the ends of the upper shoe 31 and the lower shoe 32.

As shown in FIG. 13, when the movement direction restricting jig 35 holds the ends of the upper shoe 31 and the lower shoe 32, the moving direction restricting jig 35 and the upper shoe 31 are fixed by the first knock-off bolt 50. The moving direction regulation jig 35 and the lower shoe 32 are fixed by the second knock-off bolt 60.

As shown in FIG. 14, the first knock-off bolt 50 includes a steel rod 51 having a fractured portion 54 with a reduced diameter, and a nut 52 screwed to a screw thread formed at the upper and lower ends of the steel rod 51. , 53, and the steel rod 51 is inserted through the bolt holes provided in both the upper shoe 31 and the movement direction restricting jig 35, and the nuts 52, 53 are tightened at the upper and lower ends of the steel rod 51. As a result, the upper shoe 31 and the movement direction restricting jig 35 are fixed.

On the other hand, the second knock-off bolt 60 also has a steel rod 61 having a fractured portion 64 with a reduced diameter, and nuts 62 and 63 screwed to the threads formed on the upper and lower ends of the steel rod 61. Then, the steel rod 61 is inserted through the bolt holes provided in both the lower shoe 32 and the movement direction restricting jig 35, and the nuts 62 and 63 are tightened at the upper and lower ends of the steel rod 61, thereby lowering the lower shoe 32. The moving direction regulation jig 35 is fixed. The steel rod 61 has a larger diameter than the steel rod 51, and the breaking strength of the breaking portion 64 is set higher than the breaking strength of the breaking portion 54.

As shown in FIG. 15, in the sliding seismic isolation device 30 of the illustrated example, the left and right ends of the upper shoe 31 are fixed by the movement direction restricting jig 35 and the three first knock-off bolts 50, respectively. The left and right ends of are fixed by the movement direction restricting jig 35 and three second knock-off bolts 60, respectively.

As shown in FIG. 6 in which the fixed support 30 is interposed between the lower structure 20 and the upper structure 10 and the bridge pier 20 is viewed from the bridge axis direction, at the top end of the bridge pier 20, the bridge piers 20 are spaced at right angles to the bridge axis. Two fixed bearings 30 are fixed. A steel base plate (not shown) with an anchor bolt is fixed to the top end of the pier 20 by embedding the anchor bolt in the pier 20, and the fixed bearing 30 is bolted to the base plate. It is fixed by

As shown in FIG. 16, a pair of movement direction restricting jigs 35 for fixing the upper shoe 31 and the lower shoe 32 in the fixed bearing 30 are arranged in the direction perpendicular to the bridge axis on the upper surface of the pier 20 which is the lower structure. There is. When the horizontal force P at the time of an earthquake acts on the fixed bearing 30, both the first knock-off bolt 50 and the second knock-off bolt 60 extending in the vertical direction act as a shearing force.

In addition, due to vertical earthquake motions and flexural vibrations associated therewith, and also due to the overturning moment at the top end of the pier 20 due to the center of gravity becoming an eccentric portion such as a curved girder, the lifting force on the fixed bearing 30 is increased. Can act. In the illustrated fixed bearing 30, the left and right ends of the upper shoe 31 and the lower shoe 32 are respectively clamped by the pair of movement direction restricting jigs 35 having a U-shaped cross section. It is possible to suppress the risk of the upper shoe 31 falling off from the lower shoe 32 against the upward lift force that may act due to these various factors.

The fixed bearing 30 in the illustrated example has a form in which the movement direction restricting jig 35 is fixed to the upper shoe 31 and the lower shoe 32 by the first knock-off bolt 50 and the second knock-off bolt 60. The restricting jig 35 and the lower shoe 32 may be fixed by a bolt having no breakage portion. In this form, the fixed state of the movement direction restricting jig 35 and the lower shoe 32 is maintained against an earthquake of any scale, and the first knock-off bolt 50 breaks and the lower shoe 32 is broken, for example, in a level 2 earthquake. Relative movement of the upper shoe 31 and the upper structure 10 in the bridge axis direction is allowed.

As already described with reference to FIG. 7, the relative displacement and the horizontal force at the time of the level 1 earthquake, the level 2 earthquake, and the level 3 earthquake are u1 and P1, u2 and P2, u3 and P3, respectively. is there. Then, in the fixed bearing 30, the breaking strength of the breaking portion 54 of the first knock-off bolt 50 is set as the horizontal force P2 of the level 2 earthquake (an example of the second predetermined value), and the breaking portion of the second knock-off bolt 60 is set. The breaking strength of 64 is set as the horizontal force P3 of the level 3 earthquake (an example of the first predetermined value).

Returning to FIG. 14, the breaking strength of the second knock-off bolt 60 is higher than the breaking strength of the first knock-off bolt 50. Therefore, in the illustrated example, the steel rod 61 having a relatively large diameter is applied, and the breaking portion 64 is broken. The strength is also set relatively high.

Next, a mode of relative movement of the upper shoe 31 with respect to the lower shoe 32 in the fixed bearing 30 during the level 2 earthquake and the level 3 earthquake will be described with reference to FIGS. 17 and 18. Here, FIG. 17 is a perspective view showing a state in which the first knock-off bolt is broken and the upper shoe moves relative to the lower shoe in the bridge axis direction in the sliding base isolation device serving as the fixed support. .. FIG. 18 is a perspective view showing a state where the second knock-off bolt is broken and the upper shoe moves relative to the lower shoe in a free direction in the sliding base isolation device serving as the fixed support.

As shown in FIG. 17, when the first knock-off bolt 50 breaks and the second knock-off bolt 60 does not break due to a level 2 earthquake, the fixed state of the lower shoe 32 and the movement direction restricting jig 35 is maintained. Therefore, the main girder 11 and the upper shoe 31 which are bolted to each other can be freely moved in the bridge axis direction by the pair of left and right movement direction restricting jigs 35 serving as guides by the sliding of the slider 38 with respect to the lower shoe 32. Becomes That is, the upper shoe 31 is relatively movable in the bridge axis direction with respect to the lower shoe 32. However, since the stopper ring 33 is provided on the outer periphery of the sliding surface of the lower shoe 32, the slider 38 is prevented from sliding excessively and falling off.

When a level 2 earthquake occurs and a horizontal force equal to or greater than the second predetermined value (horizontal force P2) is applied, the first knock-off bolt 50 breaks, and the pair of movement direction regulating jigs 35 cause the lower shoe 32 to move. Since the upper shoe 31 can move while the movement direction is restricted to the bridge axis direction, the seismic isolation function of the slip isolation device 30 is exerted by the movement of the upper structure 10 including the main girder 11 supported by the upper shoe 31. ..

On the other hand, as shown in FIG. 18, when the second knock-off bolt 60 breaks due to a level 3 earthquake, the first knock-off bolt 50 also breaks, and therefore the upper shoe 31 and the lower shoe 32 are completely fixed. Will be released. Therefore, when a large-scale earthquake of level 3 occurs, it is possible to allow the upper shoe 31 to move freely relative to the lower shoe 32. As a result, due to the seismic isolation effect, the horizontal force due to the level 3 earthquake is suppressed from acting on the upper structure 10 via the fixed bearing 30, and the horizontal force on the upper structure 10 via the movable bearing 40 described above. The lower structure 20 is damaged by the shearing force resulting from the vibration of the upper structure 10 when the horizontal force due to the level 3 earthquake acts on the upper structure 10 in combination with the suppression of the action of Can be effectively suppressed.

It should be noted that other embodiments in which other constituent elements are combined with the above-described configurations and the like may be combined, and the present invention is not limited to the configurations shown here. This point can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form.

For example, the slip isolation devices 30 and 40 of the illustrated example may have a ring-shaped stopper that has the fail-safe function described in Patent Document 1.

10: Upper structure 11: Main girder 12: Transverse girder 20: Lower structure (pier)
30: Sliding seismic isolation device (fixed bearing)
31: Upper shoe 32: Lower shoe 38: Slider 40: Sliding base isolation device (movable bearing)
41: Upper shoe 42: Lower shoe 48: Slider 50: First knock-off bolt 54: Breaking portion 60: Second knock-off bolt (knock-off bolt)
64: Broken part 100: Bridge

Claims (3)

A sliding seismic isolation device having an upper shoe and a lower shoe, and a slider slidable between the upper shoe and the lower shoe,
A pair of movement direction regulating jigs straddling the upper shoe and the lower shoe are ruptured when a horizontal force of a first predetermined value or more acts on one of the upper shoe and the lower shoe. It is fixed by a knock-off bolt having a part, and is not fixed to the other of the upper shoe or the lower shoe,
When the knock-off bolt is not broken, the relative movement direction of the upper shoe to the lower shoe is regulated by the pair of movement direction regulating jigs,
A sliding seismic isolation device characterized in that, when the knock-off bolt is broken, the relative movement direction of the upper shoe with respect to the lower shoe is not restricted. 2. The sliding seismic isolation device according to claim 1, wherein the movement direction restricting jig has a U-shaped cross-sectional shape for sandwiching the ends of the upper shoe and the lower shoe. A slip isolation device according to claim 1 or 2,
An upper structure and a lower structure in which the slip isolation device is interposed as a movable bearing,
A bridge, characterized in that a pair of said moving direction regulating jigs facing each other are arranged in the direction perpendicular to the bridge axis on the upper surface of said lower structure.