JP2009030243A - Base-isolated structure and base-isolating method for bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the relaxation of regulation on traffic on a bridge, associated with horizontal base-isolating work for an existing bridge pier. <P>SOLUTION: A base-isolated structure for the bridge 1 is additionally installed in the lower section of the bridge pier 20 so as to apply horizontal base-isolation to the existing bridge pier 20. The base-isolated structure comprises a new lower footing 30 which is integrally formed in the state of covering an upper section of the existing footing 22 of the bridge pier 20, and a new upper footing 50 which is supported on the lower footing 30 in such a manner as to be horizontally and relatively displaceable via a horizontal support member 40 and formed integrally with the bridge pier 20. The bridge pier 20 is cut along a horizontal support surface 42 of the horizontal support member 40, so that a section of the bridge pier 20, which is fixed to the upper footing 50, can be separated from the lower footing 30 and the existing footing 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a seismic isolation structure for seismic isolation of an existing bridge and a seismic isolation method.

  Currently, seismic reinforcement work for existing buildings is underway. This earthquake resistance measure is no exception for bridges over rivers and viaducts that cross roads and railways. For example, reinforcement work for wrapping reinforcement sheets around bridge piers and foundation ground improvement work are being carried out. .

Here, in some cases, it is advantageous in terms of cost to perform horizontal seismic isolation rather than performing such seismic reinforcement. And as this horizontal seismic isolation device, for example, a configuration in which a seismic isolation layer is interposed between a pier and a footing is disclosed, and the seismic isolation layer prevents the vibration of the ground from being transmitted to the pier. (See Patent Document 1).
JP 2004-293157 A

  However, in order to add such a seismic isolation layer to an existing bridge, it is necessary to lift the pier with a jack or the like, and the target bridge may have to be closed for a long period of time. There is.

  However, since such long-term traffic regulations have a large impact on surrounding traffic, even if it is disadvantageous in terms of cost, it is necessary to select the above seismic reinforcement work instead of horizontal seismic isolation. I won't get.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a bridge seismic isolation structure and a seismic isolation method that can relax the traffic regulation of the bridge due to the horizontal seismic isolation work of existing piers. And

In order to achieve this object, the invention shown in claim 1
A seismic isolation structure for a bridge added to the lower part of the pier to make the existing pier horizontal isolation
A new lower footing formed integrally with the upper part of the existing footing of the pier,
A new upper footing that is supported on the lower footing so as to be relatively movable in a horizontal direction via a horizontal support member, and formed integrally with the pier,
By cutting the pier along the horizontal support surface of the horizontal support member, the portion of the pier fixed to the upper footing is separated from the lower footing and the existing footing. .

  According to the first aspect of the present invention, the work requiring the passage restriction of the bridge for safety reasons is only the work of cutting the pier in the horizontal seismic isolation work of the existing pier. In other words, the new lower footing work and the new upper footing work as well as the new horizontal support member work other than these are not work accompanied by a decrease in the strength of the bridge, and the lower footing described above. During the construction work such as footing, the strength of the bridge is maintained at the existing level, and the traffic safety as a bridge is sufficiently secured. In addition, these new installation operations such as lower footing are all performed in the lower part of the bridge girder and do not hinder traffic on the bridge. Therefore, it is not necessary to restrict the passage of the bridge during a period other than the work of cutting the pier, and as a result, the restriction of the passage of the bridge can be relaxed.

The invention shown in claim 2 is the seismic isolation structure for a bridge according to claim 1,
The pier movement restricting member that restricts the relative movement between the upper footing and the lower footing until it receives a seismic motion of a predetermined level or higher and that allows the relative movement after receiving the seismic motion of the predetermined level or higher. It is characterized by having.

  According to the second aspect of the present invention, relative movement between the upper footing and the lower footing is allowed after receiving the earthquake motion of the predetermined level or higher. That is, at the time of receiving the seismic motion and thereafter, the existing pier on the upper footing side is edged so as to be relatively movable from the ground on the lower footing side. Therefore, the input of ground vibration to the pier is suppressed, and the collapse of the pier can be effectively prevented.

  On the other hand, the relative movement between the upper footing and the lower footing is restricted until an earthquake motion exceeding the predetermined level is received. Therefore, the bridge pier movement restricting member suppresses horizontal vibration of the pier with respect to the ground due to daily wind or vehicle traffic, and there is no seismic motion exceeding the predetermined level. In a peaceful state (normal time), the bridge is easy to pass.

The invention shown in claim 3 is the seismic isolation structure for a bridge according to claim 2,
One end and the other end of both ends of the bridge girder are respectively supported by a pair of the bridge piers arranged at intervals in the girder length direction of the bridge girder, and the one end is relatively moved in the horizontal direction. The other end is supported by the pier so as not to be relatively movable in the horizontal direction, while being supported by the pier.
The bridge girder movement restricting member that allows the relative movement of the one end portion until the earthquake motion of the predetermined level or more is received and that restricts the relative movement of the one end portion after receiving the earthquake motion of the predetermined level or more. It is characterized by that.

  According to the invention described in claim 3, the bridge is easy to pass after receiving the seismic motion of the predetermined level or more, and the bridge girder can be effectively prevented until it receives the seismic motion of the predetermined level. Can do. Details are as follows.

  When one end portion of the bridge girder is supported so as to be relatively movable in the horizontal direction with respect to the pier, if a large vibration is input to the bridge, one end portion of the bridge girder may be relatively moved relative to the pier. . Then, the positional deviation between the one end of the bridge girder and another bridge girder adjacent to the one end of the bridge pier in the girder length direction is large, that is, a large gap is formed between the bridge girder. The bridge becomes difficult to pass. In the worst case, the bridge girder may fall off the pier.

  In this regard, according to the bridge girder movement restricting member, since the bridge girder movement restricting member restricts relative movement between the bridge pier and one end of the bridge girder after receiving the earthquake motion of the predetermined level or higher, Misalignment with the other bridge girder adjacent in the girder length direction is suppressed, and as a result, the bridge is easy to pass even after receiving earthquake motion of the predetermined level or higher. In addition, dropping off the bridge girder from the pier is effectively prevented.

  By the way, in the ground motion above the specified level, as mentioned above, the bridge pier movement restriction member allows the relative movement of the pier to the lower footing of the pier, so that the bridge is seismically isolated at the pier, and this leads to the bridge girder. The vibration input of the ground is also suppressed, and damage to the bridge girder is effectively prevented. However, in the case of seismic motion below the predetermined level, the pier is restricted from moving relative to the lower footing by the pier movement restricting member, so there is a possibility that seismic motion may be input to the bridge girder via the pier, The bridge girder is supported at both ends by the pair of bridge piers. For this reason, when the phase of vibration between the pair of bridge piers due to an earthquake does not match, the bridge girder is pulled or compressed by the pair of bridge piers, and as a result, the bridge girder may be damaged. There is.

  In this regard, according to the bridge girder movement restricting member, relative movement between the bridge pier and one end of the bridge girder is permitted until an earthquake motion of the predetermined level or higher is received. Therefore, even if a tensile force or a compressive force acts on the bridge girder spanned by the pair of bridge piers due to an earthquake motion less than the predetermined level, these forces are flexibly changed by relative movement between one end of the bridge girder and the pier. This will ensure that bridge girder breakage is prevented.

The invention shown in claim 4 is the seismic isolation structure for a bridge according to any one of claims 1 to 3,
The horizontal support member slides while the horizontal lower surface of the sliding plate on the upper footing side and the horizontal upper surface of the sliding plate on the lower footing are in contact with each other so that the pier can be relatively moved in the horizontal direction. A sliding bearing member to support,
The sliding plate on the lower footing side is not arranged in a range from the pier to a predetermined distance so as to form a gap around the pier for arranging a wire saw for cutting the pier. .

  According to the fourth aspect of the present invention, a gap for arranging a wire saw for cutting is formed around the pier. Therefore, while using a sliding bearing member as the horizontal bearing member, the cutting of the pier is surely performed along the horizontal lower surface of the sliding plate on the upper footing side as the horizontal bearing surface of the horizontal bearing member. be able to.

  In addition, according to the sliding support member, a wide contact area between the sliding plates can be secured, so that the structure above the bridge pier can be reliably supported by the upper footing and the lower footing.

The invention shown in claim 5 is a seismic isolation method for a bridge,
A lower footing new installation step that covers an upper part of an existing footing of an existing pier and forms a new lower footing integrally with the existing footing;
An upper footing newly installing step, in which a new upper footing that is supported so as to be relatively movable in a horizontal direction via a horizontal support member is formed integrally with the pier on the lower footing,
Cutting the pier along a horizontal support surface of the horizontal support member, thereby separating a portion of the pier fixed to the upper footing from the lower footing and the existing footing; It is characterized by.

  According to the fifth aspect of the present invention, the work step that requires the passage of the bridge for safety reasons is only the pier cutting step. In other words, the lower footing new construction step and the upper footing new construction step, which are other steps, are not operations that involve a decrease in the strength of the bridge. Therefore, in these new steps, the strength of the bridge is already existing. At the same level, the safety of traffic as a bridge is ensured. Further, the lower footing new step and the upper footing new step are performed in the lower part of the bridge girder and do not hinder the passage on the bridge. Therefore, it is not necessary to restrict the passage of the bridge except for the pier cutting step, and as a result, the passage restriction of the bridge can be relaxed.

The invention shown in claim 6 is the seismic isolation method for the bridge according to claim 5,
The horizontal support member slides while the horizontal lower surface of the sliding plate on the upper footing side and the horizontal upper surface of the sliding plate on the lower footing are in contact with each other so that the pier can be relatively moved in the horizontal direction. A sliding bearing member to support,
The sliding plate on the lower footing side is not arranged in a range from the pier to a predetermined distance so as to form a gap around the pier for arranging a wire saw for cutting the pier. Seismic isolation method for bridges.
According to the sixth aspect of the present invention, the same effect as that of the fourth aspect can be obtained.

The invention shown in claim 7 is the seismic isolation method for a bridge according to claim 6,
The wire saw is disposed on the lower footing before the upper footing-side sliding plate is disposed on the lower footing-side sliding plate.
According to the invention shown in claim 7, the wire saw is arranged on the lower footing in advance before the sliding plate on the upper footing side is arranged on the sliding plate on the lower footing side. There is no need to pass a wire saw through the gap formed between the sliding plate on the upper footing side and the lower footing.

  According to the seismic isolation structure and the seismic isolation method of the present invention, it is possible to relax the traffic regulation of the bridge accompanying the horizontal seismic isolation work of the existing pier.

  Hereinafter, embodiments of a seismic isolation structure for a bridge and a seismic isolation method according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a side view of an existing bridge 1 before horizontal isolation. This existing bridge 1 is, for example, a continuous viaduct. That is, a plurality of bridge piers 20 are arranged side by side along the girder length direction of the bridge girder 10, and the corresponding bridge girder 10 is bridged between the bridge piers 20, 20 adjacent to each other in the girder length direction. Thus, a plurality of bridge girders 10 are connected in the girder length direction to form one viaduct 1.

  A lower portion of each pier 20 is integrally connected to an upper surface 22 a of a footing 22 (hereinafter referred to as an existing footing) disposed corresponding to each pier 20, and a pile 24 is integrally formed below the existing footing 22. Is provided. These existing footings 22 and piles 24 are buried in the underground G, thereby functioning as the foundation of the bridge 1. The pier 20 and the existing footing 22 are each made of concrete such as RC (steel reinforced concrete) or SRC (steel reinforced concrete), and the pile 24 is made of prestressed concrete or steel.

  Each bridge girder 10 is supported at both ends by placing both end portions 10a, 10b in the girder length direction on the upper surface 20a of the pier 20. Here, the front end portion 10a in the girder length direction of each bridge girder 10 is supported on the upper surface 20a of the bridge pier 20 via the rotation support member 12, and is thereby supported so as not to be relatively movable in the girder length direction and the girder width direction. . On the other hand, the rear end portion 10b is supported on the upper surface 20a of the pier 20 via the movement support member 14, and thus cannot be relatively moved in the girder width direction but relatively moved in the girder length direction. Supported as possible. Therefore, even if the bridge pier 20 supporting the front end portion 10a of the bridge girder 10 and the pier 20 supporting the rear end portion 10b have different vibration phases in the girder length direction, the rear end of the bridge girder 10 can be obtained. When the portion 10b moves relative to the bridge pier 20, the tensile force and the compressive force in the girder length direction acting on the bridge girder 10 from the pier 20 are absorbed and suppressed. Incidentally, the bridge girder 10 is also made of concrete such as RC (steel reinforced concrete) or SRC (steel reinforced concrete).

  2A to 3B are explanatory views of the horizontal seismic isolation structure of the present embodiment that is additionally provided on the existing viaduct 1 described above. 2A and 2B respectively show a front view longitudinal sectional view of the lower portion of the pier 20 before the additional installation and a BB sectional view in the sectional view. 3A and 3B respectively show a front view longitudinal sectional view of the lower portion of the pier 20 after the additional installation and a BB sectional view in the sectional view.

  As can be seen from the comparison between FIG. 2A and FIG. 3A, after the additional installation, the following points are different from those before the additional installation. First, the lower footing 30 is newly provided so as to cover the upper surface 22 a of the existing footing 22. An upper footing 50 is newly provided on the lower footing 30 so as to be relatively movable in the horizontal direction via the sliding support member 40. The upper footing 50 is formed integrally with the existing bridge pier 20. Yes. Further, the pier 20 is cut along the sliding surface 42 b (corresponding to the horizontal bearing surface) of the sliding bearing member 40, so that the portion fixed to the upper footing 50 in the pier 20 is the lower footing 30. And the existing footing 22.

  Therefore, even if the ground G on the lower footing 30 side vibrates, the vibration is difficult to be input to the bridge pier 20 on the upper footing 50 side, and thus the viaduct 1 is subjected to horizontal seismic isolation.

  Incidentally, on the side of the upper footing 50 and the lower footing 30, a return spring 60 for returning the upper footing 50 moved relative to the lower footing 30 is additionally provided. The restoring spring 60 is, for example, an elastic body 60 such as a laminated rubber connected to the upper footing 50 and the lower footing 30.

  Such additional installation of the horizontal seismic isolation structure to the viaduct 1 is achieved by the following seismic isolation method. FIG. 4A to FIG. 4C are explanatory diagrams of the procedure of the seismic isolation method. In each figure, the upper part shows a longitudinal sectional view in front view, and the lower part shows a plan view.

  First, the ground of FIG. 4A is excavated to expose the upper surface 22a of the existing footing 22 buried in the ground G. Then, a new lower footing 30 is integrally formed covering the upper surface 22a. That is, the mold is placed on the upper surface 22a of the existing footing 22 while enclosing the lower part of the pier 20 from the side, and concrete is placed after placing reinforcing bars, anchor members, etc. (not shown) inside these molds. Then, after the concrete is hardened, the mold is removed, and thereby the lower footing 30 is newly provided.

  Next, the lower sliding plate 41 of the components of the sliding support member 40 is fixed to the upper surface 30a of the newly installed lower footing 30. The lower sliding plate 41 is, for example, a Teflon plate having a flat upper surface, and is arranged and fixed so that the flat upper surface is horizontal. Here, a plurality of lower sliding plates 41 having a smaller area than the upper surface 30a of the lower footing 30 are arranged with an appropriate space between each other, and particularly around the pier 20 The area | region where the lower side sliding plate 41 is not arrange | positioned over the perimeter is set. In this region, the wire saw 65 is placed. That is, the upper space of the region is arranged when the upper slide plate 42 is placed on the lower slide plate 41 thereafter. Gap (see FIG. 4B). The wire saw 65 is used for the cutting work of the pier 20 performed at the end of the seismic isolation method.

  After the lower sliding plate 41 and the wire saw 65 are arranged on the upper surface 30a of the lower footing 30 in this way, the components of the sliding support member 40 are then placed on the upper surface of the lower sliding plate 41 as shown in FIG. 4B. The upper sliding plate 42 is placed. The upper sliding plate 42 is a plate material having an area covering the entire arrangement range of the lower sliding plate 41 and a material having a low sliding resistance with the lower sliding plate 41. Here, because the lower sliding plate 41 is a Teflon plate, a stainless plate having a low friction coefficient is used, but the present invention is not limited to this.

  Further, since the upper footing 50 is formed on the upper surface 42a of the upper sliding plate 42 after that, the upper footing 50 is formed (see FIG. 4C). A cutout portion 42c having a shape is formed, and two or more (in the example shown in the figure) are formed by a dividing line 42d crossing the cutout portion 42c so that the upper sliding plate 42 can be arranged from the side of the pier 20. It is divided into two pieces. Then, the upper sliding plates 42 and 42 are placed on the lower sliding plate 41 while adjusting the position so that the pier 20 is positioned inside the notch 42c. At this time, if the gap formed between the notch portion 42c and the pier 20 is large, the gap is sealed with a sealant such as a sealant, and thereby the upper footing 50 to be placed later. You may prevent the leakage of concrete.

  Then, while placing the formwork on the upper surface 42a of the upper sliding plate 42 while surrounding the pier 20, concrete is placed after arranging appropriate reinforcing bars and the like inside these formwork. At this time, the upper sliding plate 42 functions as a formwork on the lower surface side of the burying. And if it demolds after hardening of the said concrete, as shown to FIG. 4C, it will be in the state by which the newly installed upper footing 50 was supported on the lower footing 30 via the sliding bearing member 40. As shown in FIG.

  In addition, since this upper footing 50 functions as a foundation of the pier 20 after horizontal isolation, it must be integrated with the pier 20. Therefore, before the concrete is placed, a fixing member (not shown) such as a stud bolt is planted on the outer peripheral portion of the pier 20 and these stud bolts are also used for the upper footing 50 during the concrete placement. Thus, the upper footing 50 is fixedly integrated with the pier 20.

  Next, the restoring spring 60 is disposed around the upper footing 50 and the lower footing 30 so as to straddle the upper footing 50 and the lower footing 30.

  Then, finally, the pier 20 is cut along the sliding surface which is the lower surface 42 b of the upper sliding plate 42, whereby the portion of the pier 20 fixed to the upper footing 50 is separated from the lower footing 30 and the existing footing 22. To do. That is, as described above, the wire saw 65 is arranged in advance in the gap around the pier 20 (see FIG. 4B), and the wire saw 65 causes the lower surface 42b of the upper sliding plate 42 and the upper surface 30a of the lower footing 30 to be disposed. Cut the part between. As a result, the upper sliding plate 42 and the lower sliding plate 41 can move relative to each other to function as a sliding bearing, and the horizontal seismic isolation work is completed.

  By the way, as is clear from the above description, the work that requires the passage restriction of the viaduct 1 for safety reasons in this seismic isolation method is only the work of cutting the pier 20 performed last. In other words, any other work is not a work that causes a decrease in the strength of the viaduct 1, and the strength of the viaduct 1 is also maintained at the existing level, and traffic safety as the viaduct 1 is sufficiently secured. ing. In addition, any work is performed at a position below the bridge girder 10 at a position far from the bridge girder 20, and does not hinder traffic on the bridge. Therefore, according to the above-mentioned seismic isolation method, it is not necessary to regulate the passage of the viaduct 1 during the period other than the work of cutting the pier 20, and as a result, the traffic regulation of the viaduct 1 can be relaxed.

=== First Modification ===
5A and 5B are explanatory views of a first modified example of the seismic isolation structure. FIG. 5A shows a longitudinal sectional view of the lower part of the pier 20 and FIG. 5B shows a B- in FIG. 5A. B sectional drawing is shown.

  In contrast to the above-described embodiment, the first modification is different in that a stopper 70 (hereinafter referred to as a first stopper) is additionally provided with respect to the sliding support member 40. That is, since the configuration other than the first stopper 70 is substantially the same as that of the above-described embodiment, the description of the same configuration is omitted.

  The first stopper 70 is a member that prevents the sliding support member 40 from functioning until it receives an earthquake motion of level 2 or higher. In other words, the relative movement between the upper footing 50 and the lower footing 30 is restricted until a level 2 or higher earthquake motion is received, and after the level 2 or higher earthquake motion is received, the relative movement is allowed. By the way, level 2 ground motion here means “level 2 ground motion” as shown in “Road Bridge Specification (V Seismic Design) / Description” (Japan Road Association), etc. is there.

  As shown in FIGS. 5A and 5B, the first stopper 70 includes a bracket 71 fixed to the side of the upper footing 50, and a bracket 72 fixed to the side of the lower footing 30 so as to correspond to the bracket 71. It has. The horizontal flange portions 71a and 72a of the brackets 71 and 72 that are opposed to each other are formed with through holes H through which the shear pins 73 are passed, respectively. Retaining members 74, 74 such as nuts are provided to prevent 73 from falling off.

  If at least two or more such first stoppers 70 are installed, the upper footing 50 and the lower footing 30 are constrained in a substantially completely non-relative state where not only translation but also rotation is impossible. become. Therefore, in the example of FIG. 5B, the first stopper 70 is provided at four locations around the upper footing 50 and the lower footing 30.

  Here, the shear strength of the shear pin 73 is set to such a strength that the shear pin 73 is not broken by the level 1 earthquake motion but is broken at all four locations when the shear motion of the level 2 is received.

  Therefore, the shear pin 73 is not broken until an earthquake motion of level 2 or higher is received, and the relative movement between the upper footing 50 and the lower footing 30 is restricted. As a result, the first stopper 70 suppresses the horizontal vibration of the bridge pier 20 with respect to the ground G due to wind or vehicles that can occur on a daily basis, so that there is no seismic motion of level 2 or higher. In a substantially calm state (approximately normal time), the fluctuation of the viaduct 1 becomes small and the viaduct 1 becomes easy to pass.

  On the other hand, after receiving the earthquake motion of level 2 or higher, the shear pin 73 is broken and the first stopper 70 does not function, and the sliding support member 40 functions accordingly, and the upper footing 50 and the lower footing 30 are operated. Relative movement with is allowed. That is, at the time of receiving earthquake motion of level 2 or higher and thereafter, the pier 20 on the upper footing 50 side is cut so as to be relatively movable from the ground G on the lower footing 30 side. The input to 20 is suppressed, and the collapse of the pier 20 can be effectively prevented.

=== Second Modification ===
FIG.6 and FIG.7 is explanatory drawing of the 2nd modification of a seismic isolation structure. In any of the figures, a plan view of the viaduct 1 is shown in the upper stage, and a side view thereof is shown in the lower stage. In FIGS. 6 and 7, the moving support member 14 of the bridge girder 10 is omitted in order to prevent complication of the drawings.

  In the second modification, a stopper 80 (hereinafter referred to as a second stopper) is additionally provided at the rear end portion 10b of the bridge beam 10 in the first modification described above. That is, as described above with reference to FIG. 1, the rear end portion 10 b of the bridge girder 10 is supported by the bridge pier 20 so as to be relatively movable in the girder length direction by the movement support member 14. The second stopper 80 maintains a state in which the rear end portion 10b can be relatively moved until the above-described earthquake motion is received. The relative movement of the end 10b is restricted.

  According to the second stopper 80 having such a function, the bridge girder 10 can be effectively prevented from being damaged after it is easily passed after receiving a level 2 or higher earthquake motion, and before receiving the level 2 earthquake motion. High crosslink 1 can be obtained. Details are as follows.

  When a large level 2 earthquake motion is input to the viaduct 1, the rear end portion 10 b of the bridge girder 10 is relatively moved relative to the pier 20 in the girder length direction. That is, the state of FIG. 8A is changed to the state of FIG. 8B. As a result, the positional deviation between the rear end portion 10b of the bridge girder 10 and the front end portion 10a of the bridge girder 10 adjacent to the rear end of the rear end portion 10b on the bridge pier 20 increases, that is, between the bridge girders 10 and 10. As a result, the viaduct 1 becomes difficult to pass. In the worst case, the bridge girder 10 may drop off from the pier 20.

  In this regard, according to the second modification, after receiving the earthquake motion of level 2 or higher, as shown in FIG. 7, the second stopper 80 has a relative relationship between the rear end portion 10 b of the bridge girder 10 and the pier 20. Since the movement is restricted, the expansion of the gap S between the front end portion 10a of the bridge girder 10 adjacent to the rear of the girder length direction on the same pier 20 is suppressed, and as a result, the viaduct 1 is subjected to level 2 or higher earthquake motion. It will be easy to pass even after. In addition, dropping of the bridge girder 10 from the pier 20 is effectively prevented.

  Note that in this level 2 or higher earthquake motion, as described above with reference to FIG. 5A, the first stopper 70 of the first modification is broken, and the pier 20 is relatively moved with respect to the lower footing 30 as shown in FIG. Therefore, the viaduct 1 is seismically isolated by the bridge pier 20, thereby suppressing the input of the vibration of the ground G to the bridge girder 10 and effectively preventing the bridge girder 10 from being damaged. However, in the case of an earthquake motion less than level 2, as shown in FIG. 6, since the pier 20 is restricted from moving relative to the lower footing 30 by the first stopper 70, the earthquake motion is applied to the bridge girder 10 via the pier 20. Further, the bridge girder 10 is supported at its both ends 10a and 10b by a pair of bridge piers 20 and 20 adjacent to each other in the bridge girder direction. For this reason, for example, when the phase of vibration between the pair of piers 20 and 20 due to an earthquake does not coincide, the bridge girder 10 is pulled or compressed at both ends 10a and 10b by the pair of piers 20 and 20. As a result, the bridge girder 10 may be damaged.

  In this regard, the second stopper 80 according to the second modification allows relative movement between the bridge pier 20 and the rear end portion 10b of the bridge girder 10 until receiving a level 2 or higher earthquake motion. Therefore, even if a tensile force or a compressive force acts on the bridge girder 10 spanned between the pair of piers 20 and 20 due to an earthquake motion of level 2 or less, these forces are applied to the rear end portion 10b of the bridge girder 10 and the pier. As a result, the bridge girder 10 is reliably prevented from being damaged.

  As a specific configuration of the second stopper 80 having such a function, for example, as shown in FIG. 6, a bracket 81 fixed to the rear end portion 10 b of the bridge girder 10 and a through-hole penetrating the bracket 81 up and down The pin member 82 is inserted into the pier 20 so that its lower end is in contact with and supported by the upper surface 20a of the pier 20 and the upper surface 20a of the pier 20 corresponds to an allowable limit of relative movement of the rear end portion 10b of the bridge girder 10. The structure provided with the pit 83 formed in the position is mentioned. The allowable limit of relative movement is an assumed displacement amount between the bridge pier 20 and the bridge girder 10 that may occur when subjected to level 2 earthquake motion, and is calculated by an appropriate calculation method.

  According to such a configuration, when the rear end portion 10b of the bridge girder 10 is relatively moved with respect to the pier 20, the pin member 82 is connected to the pier as shown in FIG. 20 is supported on the upper surface 20a of the bridge girder by sliding the lower end portion thereof, and moves relative to the pier 20 together with the rear end portion 10b of the bridge girder 10. When the relative movement amount reaches the allowable limit, as shown in FIG. The pin member 82 falls into the pit 83 formed at the position, and the lower part of the pin member 82 is caught in the pit 83. At this time, the upper part of the pin member 82 is inserted into the through hole of the bracket 81. Yes. Therefore, the pin member 82 is engaged with both the bracket 81 and the drop hole 83, and the rear end portion 10b of the bridge girder 10 is restricted from further relative movement.

  Incidentally, such a second stopper 80 is provided for each bridge girder 10. Therefore, after receiving the earthquake motion of level 2 or higher, as shown in FIG. 7, the rear end portions 10b of all the bridge girders 10 are fixed to the corresponding piers 20 by the second stoppers 80. As a result, all the bridge girders are fixed. 10 and the bridge pier 20 are connected and integrated, and in the connected and integrated state, the sliding support member 40 under the bridge pier 20 is horizontally isolated. Here, in this connected and integrated state, all the bridge girders 10 and piers 20 in the viaduct 1 behave as one large mass point, so that the vibration period of the viaduct 1 becomes longer and slowly vibrates. Even during the vibration, the viaduct 1 can be easily passed.

  9A and 9B are side views of modified examples of the second stopper 80 described above. In the second stopper 80 described above, as shown in FIG. 7, the pin member 82 directly engages both the rear end portion 10 b and the pier 20 of the bridge girder 10, whereby the rear end portion 10 b moves relative to the pier 20. 9A and 9B, the second stopper 90 is engaged with the rear end portion 10b of the bridge girder 10 and the front end portion 10a of the bridge girder 10 adjacent to the rear end of the rear end portion 10b. In addition, the rear end portion 10b and the front end portion 10a are connected to prevent the separation thereof, and in addition to the prevention of the separation, the front end portion 10a is further connected to the pier 20 by the rotation support member 12. Therefore, the relative movement of the rear end portion 10b with respect to the pier 20 is indirectly restricted by utilizing the fact that the relative movement is impossible.

  Specifically, as shown in FIG. 9A, when the relative movement amount of the rear end portion 10b is within an allowable limit, the rear end portion 10b of the bridge girder 10 and the front end portion 10a of the bridge girder 10 adjacent to the rear thereof are straddled. Thus, both end portions 90a and 90b of the second stopper 90 are spanned and supported. That is, both end portions 90a and 90b in the girder length direction of the second stopper 90 are respectively placed and supported on the cradle 92 of the rear end portion 10b of the bridge girder 10 and the cradle 92 of the front end portion 10a of the bridge girder 10. Yes. Further, in the rear end portion 10b of the bridge girder 10 and the front end portion 10a of the bridge girder 10, recessed portions 94, 94 facing upward are respectively formed in portions located below the second stopper 90. A pair of convex portions 96, 96 are formed on the lower surface of the two stoppers 90 so as to correspond to the pair of concave portions 94, 94.

  Therefore, when the rear end portion 10b relatively moves and reaches the relative movement amount of the allowable limit, the rear end portion 90b and the front end portion 90a of the second stopper 90 are detached from the pedestals 92 and 92 and fall downward. . When the rear end portion 10b vibrates in the digit length direction due to seismic motion or the like, when the relative movement amount of the rear end portion 10b returns to the vicinity of the original zero, as shown in FIG. 90 convex portions 96, 96 are fitted into the rear end portion 10b and the concave portions 94, 94 of the front end portion 10a, whereby the rear end portion 10b of the bridge girder 10 and the front end portion 10a of the bridge girder 10 are connected. Thus, further separation of the rear end portion 10b from the front end portion 10a is restricted. Here, the front end portion 10a is restricted by the rotation support member 12 so as not to move relative to the pier 20; Through the rotation support member 12, the relative movement of the rear end portion 10b with respect to the pier 20 is indirectly restricted. Incidentally, examples of the shapes of the concave portion 94 and the convex portion 96 include shapes such as a cone and a triangular prism whose top portions are directed downward.

=== Other Embodiments ===
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, The deformation | transformation as shown below is possible in the range which does not deviate from the summary.

(A) In the above-described embodiment, the sliding support member 40 is illustrated as an example of the horizontal support member. However, the sliding support member 40 is not limited to this, and a so-called rolling support member (a plate member and a horizontal surface of the plate member in contact with the plate member). And a roller member such as a roller member such as a rolling sphere or a cylinder).

(B) In the above-described embodiment, the continuous viaduct 1 is illustrated as an example of the bridge, but the present invention is not limited to this. That is, a plurality of bridge girders 10 are not continuous but may be a single bridge girder 10 or may be an ordinary bridge passed over a river instead of a road or railroad.

It is a side view of the existing bridge 1 before horizontal isolation. 2A and 2B are respectively a front view longitudinal sectional view of a lower portion of the pier 20 before the horizontal seismic isolation structure according to the present embodiment is additionally installed, and a BB sectional view in the sectional view. 3A and 3B are respectively a front view longitudinal sectional view of the lower part of the pier 20 after the horizontal seismic isolation structure according to the present embodiment is additionally installed, and a BB sectional view in the sectional view. FIG. 4A to FIG. 4C are explanatory diagrams of the procedure of the seismic isolation method. In each figure, the upper part shows a longitudinal sectional view in front view, and the lower part shows a plan view. 5A and 5B are explanatory views of a first modification of the seismic isolation structure. It is explanatory drawing of the 2nd modification of a seismic isolation structure. It is explanatory drawing of the 2nd modification of a seismic isolation structure. FIGS. 8A and 8B are diagrams for explaining that the rear end portion 10b of the bridge girder 10 relatively moves in the girder length direction with respect to the pier 20 when a large level 2 earthquake motion is input to the viaduct 1. It is. 9A and 9B are side views of a further modification of the second stopper 80 according to the second modification described above.

Explanation of symbols

1 viaduct, 10 bridge girder, 10a front end, 10b rear end,
12 rotation support member, 14 movement support member, 20 bridge pier, 20a upper surface,
22 existing footing, 22a top surface, 24 piles,
30 Lower footing, 30a Upper surface, 40 Horizontal bearing member (sliding bearing member),
41 lower support plate, 42 upper support plate, 42a upper surface,
42b bottom surface (horizontal bearing surface), 42c notch, 42d dividing line,
50 upper footing, 60 spring for restoring, 65 wire saw,
70 first stopper (pier pier movement restriction member), 71 bracket,
71a flange, 72 bracket, 72a flange, 73 shear pin,
74 retaining member, 80 second stopper (bridge girder movement restricting member),
81 bracket, 82 pin member, 83 pit,
90 second stopper (bridge girder movement restriction member), 90a front end, 90b rear end,
92 cradle, 94 concave portion, 96 convex portion, G ground, H through hole, S gap

Claims (7)

A seismic isolation structure for a bridge added to the lower part of the pier to make the existing pier horizontal isolation
A new lower footing formed integrally with the upper part of the existing footing of the pier,
A new upper footing that is supported on the lower footing so as to be relatively movable in the horizontal direction via a horizontal support member, and is formed integrally with the pier,
By cutting the pier along the horizontal bearing surface of the horizontal bearing member, the portion of the pier fixed to the upper footing is separated from the lower footing and the existing footing. Seismic isolation structure of the bridge. A seismic isolation structure for a bridge according to claim 1,
The pier movement restricting member that restricts the relative movement between the upper footing and the lower footing until it receives a seismic motion of a predetermined level or higher and that allows the relative movement after receiving the seismic motion of the predetermined level or higher. A seismic isolation structure for bridges. A seismic isolation structure for a bridge according to claim 2,
One end and the other end of both ends of the bridge girder are respectively supported by a pair of the bridge piers arranged at intervals in the girder length direction of the bridge girder, and the one end is relatively moved in the horizontal direction. The other end is supported by the pier so as not to be relatively movable in the horizontal direction, while being supported by the pier.
The bridge girder movement restricting member that allows the relative movement of the one end portion until the earthquake motion of the predetermined level or more is received and that restricts the relative movement of the one end portion after receiving the earthquake motion of the predetermined level or more. Seismic isolation structure for the bridge. A seismic isolation structure for a bridge according to any one of claims 1 to 3,
The horizontal support member slides while the horizontal lower surface of the sliding plate on the upper footing side and the horizontal upper surface of the sliding plate on the lower footing are in contact with each other so that the pier can be relatively moved in the horizontal direction. A sliding bearing member to support,
The sliding plate on the lower footing side is not arranged in a range from the pier to a predetermined distance so as to form a gap around the pier for arranging a wire saw for cutting the pier. Seismic isolation structure of the bridge. A lower footing new installation step that covers an upper part of an existing footing of an existing pier and forms a new lower footing integrally with the existing footing;
An upper footing newly installing step, in which a new upper footing that is supported so as to be relatively movable in a horizontal direction via a horizontal support member is formed integrally with the pier on the lower footing,
Cutting the pier along a horizontal support surface of the horizontal support member, thereby separating a portion of the pier fixed to the upper footing from the lower footing and the existing footing; Seismic isolation method for bridges, which is characterized by A seismic isolation method for a bridge according to claim 5,
The horizontal support member slides while the horizontal lower surface of the sliding plate on the upper footing side and the horizontal upper surface of the sliding plate on the lower footing are in contact with each other so that the pier can be relatively moved in the horizontal direction. A sliding bearing member to support,
The sliding plate on the lower footing side is not arranged in a range from the pier to a predetermined distance so as to form a gap around the pier for arranging a wire saw for cutting the pier. Seismic isolation method for bridges. A seismic isolation method for a bridge according to claim 6,
A bridge seismic isolation method, wherein the wire saw is placed on the lower footing before the upper footing-side sliding plate is placed on the lower footing-side sliding plate.