JP2011153483A - Bridge fall preventing device with displacement limiting function for bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bridge fall preventing device with a displacement limiting function for a bridge by which the device as a whole is made compact, the construction cost is reduced, and the appearance is prevented from being spoiled. <P>SOLUTION: The bridge fall preventing device 1 with the displacement limiting function for the bridge includes a displacement limiting mechanism comprising a first member 8, a second member 14, and a displacement limiting plate 19. The first member 8 arranged on either an upper structure 2 or a lower structure 3 has a long hole 11 extending in the direction of a bride axis. The second member 14 is arranged on the other one of the upper structure 2 and the lower structure 3, and is provided with a pin 15 having an end penetrating the long hole 11 and relatively movable along the long hole 11. A lift force stopping member 17 having a diameter larger than the width of the long hole 11 is fixed to the end of the pin 15 penetrating the long hole 11. The displacement limiting plate 19 has a relatively movable distance between the first member 8 and the second member 14, which is shorter than the relatively movable distance corresponding to the length of the long hole in the direction of the bridge axis. When stress is loaded by horizontal displacement exceeding a predetermined value, the relatively movable distance in the direction of the bridge axis is increased. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a falling bridge prevention device for preventing an upper structure such as a bridge girder constituting a bridge from falling from a lower structure such as an abutment or a pier due to a large horizontal displacement at the time of a large earthquake, and an expansion and contraction of the upper structure due to a temperature change. The present invention relates to a falling bridge prevention device with a displacement restriction function for a bridge in which a displacement restriction function for restricting a horizontal displacement due to an earthquake and a horizontal displacement caused by a small and medium earthquake is arranged.

  Conventional fall-bridge prevention devices have been developed in which upper and lower structures are connected by chains, cables, steel bars, and the like. In addition, the conventional anti-falling bridge prevention device is intended to prevent the upper structure from falling from the lower structure when an unexpected large earthquake occurs. It was a thing. Recently, it has been required to provide a function for restricting displacement to the falling bridge prevention device, and a device that provides a displacement limiting mechanism separately from the falling bridge prevention device has been proposed.

JP 2002-97607 A JP 2004-36337 A Road Bridge Specification and Explanation, 5 Seismic Design Edition, December 1996, published by Japan Road Association, see pages 215-219

  However, none of the conventional anti-falling bridge devices using chains, cables, steel bars or the like has a problem of deteriorating aesthetics when attached to a bridge because the appearance is not smart. Moreover, what provided the displacement restriction | limiting mechanism separately from the fall bridge prevention apparatus had the problem that construction cost raised significantly.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a bridge-falling prevention apparatus with a displacement restriction function for a bridge that is compact in size, has a low construction cost, and does not impair the appearance.

  In order to solve the above-described problem, the bridge-preventing device with a displacement limiting function for a bridge according to the present invention includes a first member that is disposed in one of the upper structure and the lower structure and forms a long hole extending in the bridge axis direction, and the upper structure. Or a second member having a pin disposed at the other end of the lower structure and having one end penetrating the elongated hole and relatively movable along the elongated hole, and the elongated hole at one end of the pin penetrating the elongated hole. A lifting force stop member having a diameter larger than the width is fixed, and a relative movable distance shorter than a relative movable distance corresponding to the length of the long hole in the bridge axis direction is fixed between the first member and the second member. And having a displacement limiting mechanism that increases the relative movable distance in the bridge axis direction when stress due to a horizontal displacement of a certain level or more is applied.

  In the bridge prevention device with a bridge displacement limiting function of the present invention, the first member has a displacement limiting plate having a displacement limiting elongated hole that is shorter than the length of the elongated hole in the bridge axis direction. It is fixed with a knock-off bolt that breaks when stress due to the above horizontal displacement is applied, the pin is penetrated through two elongated holes, and it is relatively movable along the two elongated holes in the bridge axis direction. And

  Further, in the bridge drop prevention device with a displacement restriction function for a bridge according to the present invention, the displacement restriction plate having a displacement restriction elongated hole that is shorter than the length of the elongated hole in the bridge axis direction is overlapped with the first elongated member. A friction member having a plurality of irregularities formed on a side portion of the displacement limiting plate, wherein the first member is prevented from moving in the bridge axis direction, and has an irregularity urged by the elastic member in the direction perpendicular to the bridge axis. Is arranged so as to engage with the unevenness of the displacement limiting plate, and when the stress due to a horizontal displacement of a certain level or more is applied, the displacement limiting plate can get over the engaging portion of the unevenness and be relatively movable in the bridge axis direction. It is characterized by.

  In addition, the bridge prevention device with a bridge displacement limiting function according to the present invention breaks when a stress due to a horizontal displacement of a certain level or more is applied to the first member with a stopper that limits the relative movement of the second member in the bridge axis direction. The distance between the stopper and the second member in the direction of the bridge axis is set to be shorter than the relative distance along the elongated hole of the pin.

  Further, according to the present invention, there is provided a bridge prevention device with a displacement restriction function for a bridge, wherein the pin is initially arranged with respect to the slot, and the end of the slot on the lower structure end side where the upper structure drops from the lower structure. The distance between the pin and the pin is set to be larger than the distance between the end of the long hole on the other side and the pin.

  In addition, the falling bridge prevention device with a displacement restriction function for a bridge according to the present invention has a shape of the end portion of the long hole of the pin so that a contact area between the pins and the end portion of the long hole is increased. It is formed according to the cross-sectional shape.

A first member which is disposed in one of the upper structure or the lower structure and forms a long hole extending in the direction of the bridge axis; and one end which is disposed in the other of the upper structure or the lower structure and penetrates the long hole along the long hole A second member having a relatively movable pin; and an upper lift stop member having a diameter larger than the width of the elongated hole is fixed to one end of the pin penetrating the elongated hole; and the first member and the second member Has a relative movable distance shorter than the relative movable distance corresponding to the length of the long hole in the bridge axis direction, and is capable of relative movement in the bridge axis direction when stress due to a horizontal displacement of a certain level or more is applied. With a configuration that includes a displacement limiting mechanism that increases the distance, it is possible to add a function to prevent the overcoiling force and to limit the displacement to the falling bridge prevention device with a simple configuration, and to prevent the falling bridge with a displacement limiting function that is compact and inexpensive in construction cost. An apparatus can be provided.
A displacement limiting plate having a displacement limiting slot which is shorter than the length of the long hole in the bridge axis direction is fixed to the first member with a knock-off bolt that is broken when two long holes overlap and a stress due to horizontal displacement exceeding a certain level is applied. The configuration in which the pin is passed through the two long holes and is relatively movable along the two long holes in the bridge axis direction can add a displacement limiting function to the falling bridge prevention device with a simple structure, Seismic energy can be absorbed by the knock-off bolt breaking during a major earthquake.
A displacement limiting plate having a displacement limiting elongated hole that is shorter than the length of the elongated hole in the bridge axis direction is arranged on the first member so that the two elongated holes overlap, and a plurality of irregularities are formed on the side of the displacement limiting plate. A friction member formed on the first member so as not to move in the direction of the bridge axis and formed with irregularities urged in the direction perpendicular to the bridge axis by the elastic member so as to engage with the irregularities of the displacement limiting plate, When the stress due to horizontal displacement is applied, the displacement limiting plate can move over the concave and convex engaging portions and can move relative to the bridge axis direction, thereby adding a displacement limiting function to the falling bridge prevention device with a simple configuration. It is possible to absorb the seismic energy when the displacement limiting plate moves over the concave and convex engaging portion with the friction member and moves relative to each other during a large earthquake.
A stopper that restricts relative movement of the second member in the bridge axis direction of the second member is fixed to the first member with a knock-off bolt that is broken when a stress due to a horizontal displacement of a certain level or more is applied, and the stopper and the second member in the bridge axis direction With the configuration in which the relative movable distance of the pin is set to be shorter than the relative movable distance along the elongated hole of the pin, a displacement limiting function can be added to the falling bridge prevention device with a simple configuration. By breaking, it becomes possible to absorb the seismic energy.
The distance between the end of the long hole on the end of the lower structure where the upper structure falls from the lower structure and the pin is the position of the pin on the other side and the pin. With a configuration arranged so as to be larger than the distance between the two, it is possible to ensure a relative movable distance of horizontal displacement on the falling bridge side at the time of a large earthquake.
In order to increase the contact area between the pin and the end of the elongated hole, the configuration of the shape of the end of the elongated hole according to the cross-sectional shape of the pin increases the contact area between the pin and the elongated hole at the time of collision. In addition, the stress load on the end portion of the long hole can be dispersed to prevent the end portion of the long hole from being broken.

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  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are diagrams showing the installation status of a falling bridge prevention device with a displacement restriction function for a bridge according to the present invention.

  FIG. 1 shows an embodiment in which a falling bridge prevention device 1 with a displacement restriction function for a bridge is installed between an abutment 5 as a lower structure 3 and a bridge girder 4 as an upper structure 2. FIG. 2 shows an embodiment in which a falling bridge prevention device 1 with a bridge displacement limiting function is installed between a bridge pier 7 as a lower structure 3 and a bridge girder 4 as an upper structure 2. A support device (not shown) is disposed between the upper structure 2 and the lower structure 3. Since the falling bridge prevention device 1 with a bridge displacement limiting function is arranged in parallel with the bearing device, there is no problem of deteriorating the aesthetics as compared with a falling bridge prevention device using a chain, a cable, a steel rod, or the like.

  3 and 4 show a cross-sectional view and a plan view of the first embodiment of the falling bridge prevention device 1 with a bridge displacement limiting function of the present invention.

  In this embodiment, the first member 8 is fixed to the upper structure 2 with a set bolt 9. A base plate 12 is fixed to the lower structure 3 with anchor bolts 13. A second member 14 having pins 15 erected on the base plate 12 is fixed with fixing bolts 16.

  A step 10 is formed on the first member 8. An elongated hole 11 extending in the bridge axis direction is formed in the stepped portion 10. The displacement limiting plate 19 is fixed to the step portion 10 of the first member 8 with a knock-off bolt 21 that is broken by a stress load of a certain level or more. The displacement limiting plate 19 is formed with a displacement limiting slot 20 extending in the bridge axis direction. The displacement limiting plate 19 is fixed with a knock-off bolt 21 so that the displacement limiting slot 20 and the slot 11 of the first member 8 overlap. The length of the long hole 11 in the bridge axis direction is longer than the length of the displacement limiting long hole 20 in the bridge axis direction, and the width in the direction perpendicular to the bridge axis is the same in the long hole 11 and the displacement limiting long hole 20. The displacement restricting plate 19 is fixed so that the displacement restricting long hole 21 is positioned at the intermediate portion of the elongated hole 11 in the bridge axis direction.

  The pin 15 erected on the second member 14 passes through the long hole 11 of the first member 8 and the displacement limiting long hole 20 of the displacement limiting plate 19 and is formed by the step portion 10 of the first member 8. It extends to the void. An upper reed stop member 17 larger than the width of the long hole 11 and the displacement limiting long hole 20 in the direction perpendicular to the bridge axis is fixed to the tip of the pin 15 by means such as screwing. A cushioning material 18 such as rubber is wrapped around the outer periphery of the pin 15 so as to absorb the impact at the time of collision between the pin 15 and the end of the displacement limiting long hole 20 or the end of the long hole 11 in the event of an earthquake. May be. The outer diameter of the cross section of the pin 15 around which the cushioning material 18 is wound is made slightly smaller than the width of the elongated hole 11 and the displacement restricting elongated hole 20 in the direction perpendicular to the bridge axis, and can be relatively moved along the two elongated holes 11 and 20. To do.

  When the pin 15 is disposed in the center of the long hole 11 and the displacement limiting long hole 20 in the bridge axis direction, from the outer periphery of the pin 15 around which the cushioning material 18 is wound to the end of the displacement limiting long hole 20 in the bridge axis direction. L1 and the distance L2 from the outer periphery of the pin 15 around which the cushioning material 18 is wound to the end portion in the bridge axis direction of the long hole 11 have a relationship of L2> L1. L1 is a relative movable distance that allows expansion and contraction due to temperature change of the superstructure 2 and displacement in the bridge axis direction at the time of a medium and small earthquake. L2 is a relative movable distance of the pin 15 in the bridge axis direction at the time of a large earthquake.

  In the event of a large earthquake, the pin 15 collides with the end of the displacement limiting slot 20 of the displacement limiting plate 19 in the bridge axis direction due to a large horizontal displacement. When the load due to the collision exceeds a predetermined value, the knock-off bolt 21 is broken, the displacement limiting plate 19 can slide in the bridge axis direction, and the pin 15 can be displaced by a distance L2 exceeding the displacement limiting distance L1. In order to break the knock-off bolt 21 when the collision load exceeds a predetermined value, the number of the knock-off bolts 21, the bolt size, and the type of the washer portion are set. Part of the seismic energy is absorbed by breaking the knock-off bolt 21 that fixes the displacement limiting plate 19. Since only the knock-off bolt 21 breaks, the displacement limiting plate 19 can be reused after the earthquake.

  The pin 15, which can be relatively moved beyond the displacement limitable distance L 1, can move relative to the left and right in the bridge axis direction along the long hole 11 of the first member 8 by a distance L 2. The left and right relative movable distance L2 in the bridge axis direction is set so as to prevent the destruction of the first member 8 due to the collision of the end of the long hole 11 of the pin due to a large horizontal displacement at the time of a large earthquake. The upper structure 2 is prevented from falling from the lower structure 3 as long as the pin 11 fixed to the other structural part is held in the elongated hole 11 of the first member fixed to one of the upper and lower structural parts 2 and 3. Is done.

  The pin 15 that passes through the long hole 11 and the displacement limiting long hole 20 is provided with a fixing means such as a screwing or the like that has an upper reed stop member 17 larger than the width of the long hole 11 and the displacement limiting long hole 20 in the direction perpendicular to the bridge axis. It is fixed by. The upper arm stop member 17 has a function of maintaining the connection state between the upper structure 2 and the lower structure 3 against vertical movement during an earthquake. The upper arm stop member 17 is located in a space formed by the step portion 10 of the first member 8 and corresponds to the vertical movement at the time of an earthquake. 3 and 4 show an example in which the first member 8 is arranged on the upper structure 2 side and the second member 14 is arranged on the lower structure 3 side. It may be arranged on the lower structure 3 side, and the second member 14 may be arranged on the upper structure 2 side.

  According to the first embodiment of the present invention, the bridge prevention device 1 with a displacement restriction function for a bridge can be added with a function of stopping the upper anchoring force and the displacement restriction to the falling bridge prevention device with a simple configuration, and is compact and has a construction cost. It is possible to provide an inexpensive bridge prevention device with a displacement limiting function.

  5 and 6 show a plan view and a partial cross-sectional view of a second embodiment of the falling bridge prevention device 1 with a bridge displacement limiting function of the present invention.

  In this embodiment, similarly to the first embodiment shown in FIG. 3, a displacement limiting plate 19 having a displacement limiting long hole 20 formed in the step portion 10 of the first member 8 is disposed. A plurality of irregularities 23 are formed on both sides of the displacement limiting plate 19 in the bridge axis direction. In the frame member 24 fixed to the step portion 10 of the first member 8, a friction member 25 and an elastic member 26 such as rubber are disposed on the back portion thereof. The friction member 25 is restrained from moving in the bridge axis direction and the vertical direction by the frame 24 and is urged in the direction orthogonal to the bridge axis by an elastic member 26 such as rubber disposed on the back portion. The friction member 25 is formed with unevenness 27 that engages with the unevenness 23 formed on the side of the displacement limiting plate 19.

  When the pin 15 collides with the end of the displacement limiting slot 20 of the displacement limiting plate 19 due to a horizontal displacement due to a large earthquake, and the stress load due to the collision is a certain value or more, the displacement limiting plate 19 is uneven with the friction member 25. Relative movement in the direction of the bridge axis over the 23, 27 engaging part. A large frictional force acts between the friction member 25 and the seismic energy to be absorbed during the relative movement over the uneven engagement portion. The relative movable distance of the pin 15 is a distance until the position of the end of the displacement limiting long hole 20 of the displacement limiting plate 19 reaches the position of the end of the long hole 11 of the first member 8. After the earthquake, the displacement limiting plate 19 and the friction member 25 can be reused. In the drawing, an embodiment in which the shape of the unevennesses 23 and 27 is a sawtooth shape is shown, but the unevenness shape may be a semicircular shape.

  According to the bridge falling prevention device 1 with a displacement restriction function for a bridge according to the second embodiment of the present invention, it is possible to add a function of stopping the upper anchoring force and the displacement restriction to the falling bridge prevention device with a simple configuration, and it is compact and has a construction cost. It is possible to provide a falling bridge prevention device with a displacement limiting function that is inexpensive and has an excellent seismic energy absorption capability during an earthquake.

  7 and 8 show a cross-sectional view and a plan view of the first embodiment of the falling bridge prevention device 1 with a bridge displacement limiting function of the present invention.

  In this embodiment, the first member 8 is fixed to the upper structure 2 with a set bolt 9. A base plate 12 is fixed to the lower structure 3 with anchor bolts 13. A second member 14 having pins 15 erected on the base plate 12 is fixed with fixing bolts 16. A step 10 is formed on the first member 8. An elongated hole 11 extending in the bridge axis direction is formed in the stepped portion 10.

  The pin 15 erected on the second member 14 passes through the long hole 11 of the first member 8 and extends to a space formed by the step portion 10 of the first member 8. An upper reed stop member 17 larger than the width of the long hole 11 in the direction perpendicular to the bridge axis is fixed to the tip of the pin 15 by means such as screwing. A buffer material 18 such as rubber may be wound around the outer periphery of the pin 15. The outer diameter of the cross section of the pin 15 around which the cushioning material 18 is wound is made slightly smaller than the width of the long hole 11 in the direction perpendicular to the bridge axis so that the pin 15 can move relative to the long hole 11.

  A pair of displacement limiting stoppers 22 are fixed to the lower part of the first member 8 by knock-off bolts 21 that are broken by a stress load of a certain level or more. A distance L1 in the bridge axis direction between the pair of displacement limiting stoppers 22 and both side surfaces of the second member 14 is the displacement limitable distance. On the other hand, the distance L2 from the outer periphery of the pin 15 around which the cushioning material 18 is wound to the end portion in the bridge axis direction of the long hole 11 is in a relationship of L2> L1. L1 has a function of restricting expansion and contraction due to temperature change of the superstructure 2 and horizontal displacement during a small and medium earthquake.

  During a major earthquake, the side surface of the second member 14 collides with the displacement limiting stopper 22 due to a large horizontal displacement. When the load due to the collision exceeds a predetermined value, the knock-off bolt 21 is broken, and the pin 15 can be displaced by a distance L2 exceeding the displacement limit distance L1. In order to break the knock-off bolt 21 when the collision load exceeds a predetermined value, the number of the knock-off bolts 21, the bolt size, and the type of the washer portion are set. A part of the seismic energy is absorbed by breaking the knock-off bolt 21 that fixes the displacement limiting stopper 22. Since only the knock-off bolt 21 is broken, the displacement limiting stopper 22 can be reused after the earthquake.

  The pin 15 that can move relative to the displacement limit L1 can move relative to the left and right in the bridge axis direction along the long hole 11 of the first member 8 by a distance of L2. The left and right relative movable distance L2 in the bridge axis direction is set so as to prevent the destruction of the first member 8 due to the collision of the end of the long hole 11 of the pin due to a large horizontal displacement at the time of a large earthquake. The upper structure 2 is prevented from falling from the lower structure 3 as long as the pin 11 fixed to the other structural part is held in the elongated hole 11 of the first member fixed to one of the upper and lower structural parts 2 and 3. Is done.

  A pin 15 that passes through the long hole 11 is screwed with an upper reed stop member 17 that is larger than the width of the long hole 11 in the direction perpendicular to the bridge axis. The upper arm stop member 17 has a function of maintaining the connection state between the upper structure 2 and the lower structure 3 against vertical movement during an earthquake. The upper arm stop member 17 is located in a space formed by the step portion 10 of the first member 8 and corresponds to the vertical movement at the time of an earthquake. 5 and 6 show an example in which the first member 8 is disposed on the upper structure 2 side and the second member 14 is disposed on the lower structure 3 side. It may be arranged on the lower structure 3 side, and the second member 14 may be arranged on the upper structure 2 side.

  According to the falling bridge prevention apparatus 1 with a displacement restriction function for a bridge according to the third embodiment of the present invention, it is possible to add a function of stopping the upper anchoring force and the displacement restriction to the falling bridge prevention apparatus with a simple configuration, and it is compact and has a construction cost. It is possible to provide an inexpensive bridge prevention device with a displacement limiting function.

  FIG. 9 shows a time when an embodiment for preventing the falling bridge from the lower structure 3 of the upper structure 2 more reliably is shown. In this embodiment, the initial arrangement position of the pin 15 in the long hole 11 is the distance L3 between the outer periphery of the pin 15 and the end 11a located at the end of the lower structure 3 (the side on which the upper structure 2 falls). When the distance L4 between the outer periphery of the pin 15 and the other end 11b of the long hole 11 is set, the relationship of L3> L4 is established. By setting the relative movable distance L3 on the side where the bridge is dropped with respect to a large horizontal displacement at the time of a large earthquake to be larger than the other relative movable distance L4, it is possible to prevent the falling bridge more reliably.

  10 and 11 are views showing the shapes of the end portions 11c and 11d of the elongated hole 11 according to the difference in the cross-sectional shape of the pin 15. FIG.

  10 shows a case where the cross-sectional shape of the pin 15 is rectangular, the shape of the end 11c of the elongated hole 11 is linear, and when the pin 15 having a rectangular cross-section collides with the end 11c of the elongated hole 11, The contact area between the outer periphery and the end portion 11c of the elongated hole 11 is increased to prevent partial concentration of the stress due to the collision, and the stress of the collision is evenly transmitted to the end portion 11c of the elongated hole 11, and the first due to the stress concentration. It becomes possible to prevent the member 8 from being broken. The displacement limiting plate 19 may be applied to the shape of the end of the displacement limiting slot 20.

  11 shows a case where the cross-sectional shape of the pin 15 is circular, the shape of the end portion 11c of the long hole 11 is semicircular, and the pin 15 having a circular cross section collides with the end portion 11c of the long hole 11. The contact area between the outer periphery of the elongated hole 11 and the end 11c of the elongated hole 11 is increased to prevent partial concentration of stress due to the collision, and the stress of the collision is evenly transmitted to the end 11c of the elongated hole 11. It becomes possible to prevent the one member 8 from being broken. The displacement limiting plate 19 may be applied to the shape of the end of the displacement limiting slot 20.

  As described above, according to the bridge falling prevention device with a displacement limiting function of the present invention, it is possible to add the function of the upper anchoring force prevention and displacement limiting to the falling bridge prevention device with a simple configuration, which is compact and inexpensive in construction cost. Therefore, it is possible to provide a bridge prevention device with a displacement limiting function for bridges that has excellent seismic energy absorption performance.

  1: Bridge fall prevention device with displacement restriction function for bridge, 2: Upper structure, 3: Lower structure, 4: Bridge girder, 5: Abutment, 6: Parapet, 7: Bridge pier, 8: First member, 9: Set bolt, 10 : Stepped part, 11: Long hole, 12: Base plate, 13: Anchor bolt, 14: Second member, 15: Pin, 16: Fixing bolt, 17: Upper arm stop member, 18: Buffer rubber, 19: Displacement limit Plate: 20: Displacement restriction slot, 21: Knock-off bolt, 22: Displacement restriction stopper, 23: Displacement restriction plate, 24: Frame member, 25: Friction member, 26: Elastic member, 27: Friction member Unevenness

Claims (6)

A first member that is disposed in one of the upper structure and the lower structure and forms a long hole extending in the bridge axis direction;
A second member provided with a pin disposed on the other of the upper structure or the lower structure and having one end penetrating the elongated hole and relatively movable along the elongated hole;
An upper lifting force stopping member having a diameter larger than the width of the elongated hole is fixed to one end of the pin penetrating the elongated hole,
The first member and the second member have a relative movable distance shorter than the relative movable distance corresponding to the length of the elongated hole in the bridge axis direction, and are subjected to stress due to a horizontal displacement of a certain level or more. Then, a falling bridge prevention device with a displacement restriction function for a bridge, in which a displacement restriction mechanism that increases a relative movable distance in the bridge axis direction is arranged.   A displacement-reducing plate having a displacement-restricting elongated hole that is shorter than the length of the elongated hole in the bridge axis direction on the first member is a knock-off bolt that is broken when two elongated holes are overlapped and a stress due to horizontal displacement exceeding a certain level is applied. The bridge prevention with a bridge displacement limiting function according to claim 1, wherein the pin is passed through the two long holes and is relatively movable along the two long holes in the bridge axis direction. apparatus.   A displacement limiting plate having a displacement limiting elongated hole that is shorter than the length of the elongated hole in the bridge axis direction is disposed on the first member so that the two elongated holes overlap, and a plurality of irregularities are formed on the side of the displacement limiting plate. Forming a friction member formed on the first member to prevent the movement in the bridge axis direction and forming an unevenness biased by the elastic member in the direction perpendicular to the bridge axis, so as to engage with the unevenness of the displacement limiting plate, 2. The bridge displacement limiting function according to claim 1, wherein when a stress due to a horizontal displacement of a certain level or more is applied, the displacement limiting plate can move over the concave and convex engaging portions and can be relatively moved in the bridge axis direction. Fall bridge prevention device.   A stopper that restricts relative movement of the second member in the bridge axis direction of the second member is fixed to the first member with a knock-off bolt that breaks when stress due to a horizontal displacement of a certain level or more is applied, and the bridge between the stopper and the second member 2. The falling bridge prevention device with a displacement restriction function for a bridge according to claim 1, wherein a relative movable distance in the axial direction is set shorter than a relative movable distance along the elongated hole of the pin.   The initial arrangement position of the pin with respect to the elongated hole is the distance between the end of the elongated hole on the end of the lower structure where the upper structure is dropped from the lower structure and the end of the elongated hole on the other side. The bridge falling prevention device with a displacement limiting function for a bridge according to any one of claims 1 to 4, wherein the bridge prevention device is disposed so as to be larger than a distance between a portion and the pin.   The shape of the end of the elongated hole is formed in accordance with the cross-sectional shape of the pin so that the contact area between the pin and the end of the elongated hole is increased when the pin collides. The falling bridge prevention device with a displacement limiting function for a bridge according to any one of 5.

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