JP4500946B2 - Negative reaction force transmission structure in girder bridge - Google Patents

Description

  The present invention relates to a negative reaction force transmission structure in a girder bridge, and more particularly to a structure for transmitting a vertically upward force (negative reaction force) generated in a main girder during an earthquake to a substructure.

  If the girder bridge is a long span or an unequal span, it will be supported during an earthquake due to vibration of the girder accompanied by vertical displacement during a bridge axis earthquake or torsional deformation during a bridge axis perpendicular earthquake. There may be a vertical upward force (negative reaction force) that lifts up. If the bearing is damaged by the negative reaction force, the structural system will change suddenly, and unexpected stress may occur in each part of the bridge. For this reason, it is necessary to take measures to reliably transmit the negative reaction force generated in the main beam to the substructure.

Conventionally, there are the following methods for transmitting the negative reaction force, and these have some problems.
1) How to receive the main girder with Pendel support (Figure 7)
This method is a method in which the rocker 102 is disposed between the main girder 100 and the abutment 101, and the upper and lower ends thereof are pin-coupled. However, PC girders have no track record, and when applied, a large reaction force acting on the pins is received by the concrete, so a large-scale reinforcement is required.

2) Method using vertical cable (Fig. 8)
In this method, as shown in FIG. 5A, the main girder 100 is supported by the movable support 103, and the upper and lower ends of the vertical cable 104 are fixed to the main girder 100 and the abutment 101 to resist the negative reaction force. And has a track record in PC digits. However, in order not to restrict the expansion and contraction and horizontal displacement of the main girder 100, it is necessary to provide a large box opening 105 in the main girder 100 and the abutment 101, and it is necessary to consider the connection of the cross girder PC steel materials. Further, as shown in FIG. 4B, since secondary stress is generated in the vertical cable 104 when the main girder is deformed, there is a problem in its fatigue durability.

3) A method of providing a protrusion penetrating the parapet at the end of the beam (Fig. 9)
In this method, as shown in FIG. 2A, the main girder 100 is supported by a movable support 103, an opening 107 is provided in the parapet 106 of the abutment 101, a projection 108 is provided at the end of the girder, and the projection 108 is provided. This is a method of inserting into the opening 107 so that a gap is formed above and below. As a result, the protrusion 108 does not come into contact with the parapet 106 in a normal state, and attempts to transmit the negative reaction force to the parapet 106 by coming into contact with the parapet 106 as shown in FIG. . However, in this method, when the projection 108 comes into contact with the parapet 106 at the time of an earthquake, friction is generated and the horizontal displacement of the main girder 100 is constrained, or stress concentration occurs on the projection 108 and the parapet 106 to cause the damage. It becomes.

4) A method of installing a movable support between the upper surface of the protrusion and the parapet, with a protrusion penetrating the parapet at the end of the beam.
This method is an improvement over the method of 3). That is, as shown in FIG. 5A, in addition to the normal movable support 103 that supports a vertically downward force (positive reaction force), a negative is provided between the upper surface of the projection 108 provided at the end of the girder and the inner surface of the opening 107. This is a method of providing a movable support 109 for receiving a reaction force. However, in this method, as shown in FIG. 5B, since the negative reaction force acts by the rotation of the main beam 100 even in the normal state, the negative reaction force movable support 109 is also used for the positive reaction force. Deformation performance equivalent to that of the movable support 103 is required, which is uneconomical.

Prior art information relating to the invention of this application includes the following.
JP 2004-92269 A

The present invention has been made based on the technical background as described above, and achieves the following object.
The purpose of the present invention is to prevent the horizontal displacement and rotational displacement of the main girder in a normal state, transmit the negative reaction force generated in the main girder to the parapet during an earthquake, and relieve the stress and transmit the girder. It is to provide a negative reaction force transmission structure in a bridge.

  Another object of the present invention is a negative reaction force transmission structure in a girder bridge that can follow the displacement of the main girder without causing large friction or the like during an earthquake and without restraining the horizontal displacement or rotational displacement of the main girder. It is to provide.

The present invention employs the following means in order to achieve the above object.
That is, the present invention is a negative reaction force transmission structure for transmitting a negative reaction force acting on the main girder to the abutment in a girder bridge whose main girder end is supported by the abutment via a movable support. ,
A protrusion is provided at the tip of the main girder end, and this protrusion is disposed through an opening provided in a parapet of the abutment so that there is a gap above and below the protrusion,
Further, in the negative reaction force transmission structure in the girder bridge, a buffer member is provided on the upper surface of the projection, and a gap is provided between the upper surface of the buffer member and the inner surface of the opening.

  More specifically, the buffer member has a sliding function. For example, both the protrusion and the opening may have a rectangular cross section. The buffer member is a pad type.

  The buffer member is made of laminated rubber formed by laminating a steel plate and a rubber layer. In order to give the buffer member a slip function, a configuration in which a slide plate is provided on the upper surface of the buffer member and the inner surface of the opening can be employed. In addition, in order to hold the buffer member in a predetermined position, the protrusion is provided with a plurality of anchor bars protruding from the upper surface thereof, and the buffer member is inserted into the anchor bar to a predetermined depth position. It is also possible to adopt a configuration in which holes are provided. As the movable bearing, a sliding rubber bearing can be used.

  According to the present invention, since the gap is provided between the buffer member installed on the projection and the inner surface of the opening, the projection and the buffer member restrain the horizontal displacement of the main girder and the rotational displacement in the vertical direction in a normal state. There is nothing. On the other hand, in the event of an earthquake, the negative reaction force acting on the main girder is transmitted to the parapet via the buffer member, so that the stress is relieved and the protrusion and the parapet are not damaged.

  Further, by providing the buffer member with a sliding function, a large friction does not occur, and the main girder can be displaced without restraining the horizontal displacement and rotational displacement of the main girder. In addition, the buffer member is not subjected to a force at all times and acts only during an earthquake, so that it can be made simple and economical.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an embodiment of the present invention. FIG. 1 is a front view as viewed in the direction of the bridge axis direction, FIG. 2 is a cross-sectional view as viewed in the direction perpendicular to the bridge axis, and FIG. The abutment 1 has a vertical wall 2 and a parapet (chest wall) 3 formed so as to rise from a back side portion of the vertical wall 2.

  The main girder 4 is composed of a PC girder, and a pair of movable supports 5 are installed between the girder end 4 a that is the end of the main girder 4 and the vertical wall 2. The vertical load of the main girder 4 is transmitted to the abutment 1 via the movable support 5. In this embodiment, the movable support 5 is a sliding rubber support. The sliding rubber support 5 is a well-known one, and is installed on the upper plate 6 fixed to the lower surface of the beam end 4 a, the lower plate 7 fixed to the upper surface of the vertical wall 2, and the lower plate 7. It consists of pad-type laminated rubber 8. The upper plate 6 slips between the laminated rubber 8, and thereby the main girder 4 can be displaced horizontally. The structure for sliding is substantially the same as that employed in the buffer member described later. The block 9 provided on the vertical wall 2 so as to sandwich the beam end 4a is a member for limiting the movement of the main beam 4 in the direction perpendicular to the bridge axis.

  A pair of protrusions 10 having a quadrangular cross section extending in the bridge axis direction are provided on the beam end 4a at intervals in the direction perpendicular to the bridge axis. On the other hand, the parapet 3 is provided with a pair of openings 11 having a square cross section corresponding to the protrusions 10. The protrusion 10 is disposed in the opening 11 so that there is a gap above and below the protrusion 10 and penetrates the parapet 3. A buffer member 12 is provided on the upper surface of the protrusion 10, and a gap S is provided between the upper surface of the buffer member 12 and the inner surface of the opening 11. A water stop cover 25 is provided on the back side of the parapet 3 so as to cover the opening 11.

  4 and 5 show the detailed structure of the buffer member 12, FIG. 4 is a cross-sectional view taken along the direction of the bridge axis, and FIG. 5 is a cross-sectional view taken along the direction perpendicular to the bridge axis. In this embodiment, the buffer member 12 is made of a pad-type laminated rubber. The laminated rubber 12 is formed by alternately laminating rubber layers 13 and steel plates 14, 15, and 16 and vulcanizing and bonding them. The upper and lower steel plates 14 and 15 are thicker than the middle steel plate 16. used.

  The buffer member 12 is of a pad type as described above, and is of a type that is placed on the upper surface of the protrusion 10. For this reason, a means for holding the buffer member 12 in a predetermined position is provided. As the holding means, the protrusion 10 is provided with a plurality of anchor bars 17 protruding from the upper surface thereof. Further, the buffer member 12 is provided with an insertion hole 18 of the anchor bar 17 from the lower surface to the upper surface of the upper steel plate 15, and the anchor bar 18 is inserted to a predetermined depth position of the insertion hole 18. The predetermined depth position is a depth position at which the buffer member 12 can be deflected in the vertical direction while not causing shear deformation. Specifically, at the intermediate portion in the thickness direction of the upper steel plate 15. is there.

  The cushioning member 12 is provided with a sliding function, and a sliding plate 19 is provided on the cushioning member 12 as a structure for that purpose. Specifically, the slip plate 19 is fitted in a recess provided in the upper steel plate 15. A Teflon (registered trademark) plate is used as the slide plate 19. On the other hand, a slide plate 20 is also provided on the inner surface of the opening 11 facing the upper surface of the protrusion 10. A stainless plate is used as the slide plate 20. The slide plate 20 is fixed to the lower surface of the mounting plate 21, and the mounting plate 21 is fixed to the inner surface of the opening 11 through stud bolts 22 embedded in the parapet 3.

  According to the above structure, since the gap S is provided between the buffer member 12 and the inner surface of the opening 11, the protrusion 10 and the buffer member 12 do not restrain the behavior of the main beam 4 in a normal state. That is, the main girder 4 can be displaced horizontally and can also be rotated in the vertical direction. On the other hand, during an earthquake, as shown in FIG. 6, the negative reaction force acting on the main beam 4 is transmitted to the parapet 3 via the buffer member 12. For this reason, the stress transmitted to the parapet 3 is relieved, and the protrusion 10 and the parapet 3 are not damaged. Further, since the buffer member 12 slips between the slide plates 19 and 20, a large friction does not occur, and the displacement of the main girder 4 can be followed without restraining the horizontal displacement and rotational displacement of the main girder. . Further, the buffer member 12 does not always have a force, and only has a force when an earthquake occurs. Therefore, the buffer member 12 can be made simple and economical.

  Further, since the buffer member 12 is held by the protrusion 10 by the anchor bar 17 inserted into the insertion hole 18, no shear deformation occurs at the time of an earthquake, and slip occurs immediately between the slide plates 19 and 20. Can be made. On the other hand, since the anchor bar 17 is inserted up to a predetermined depth position of the insertion hole 18, it can be flexibly deformed in the vertical direction without impairing the buffer function of the buffer member 12.

  The above embodiment is merely an example, and various modifications can be made to the present invention. For example, in the above-described embodiment, two protrusions and two openings are provided. However, the present invention is not limited to this, and an aspect in which one or three or more openings are provided is also included in the present invention.

It is a front view by showing an embodiment of this invention and a bridge axis direction arrow. It is sectional drawing by the bridge axis perpendicular direction arrow of the embodiment. It is a top view of the embodiment. It is sectional drawing which shows the detail of a buffer member and is a bridge-axis direction arrow view. It is sectional drawing by the bridge axis orthogonal direction arrow of the buffer member. It is sectional drawing for demonstrating the effect | action of embodiment. It is a figure which shows a prior art example. It is a figure which shows another prior art example. It is a figure which shows another prior art example. It is a figure which shows another prior art example.

Explanation of symbols

1 Abutment 2 Vertical wall 3 Parapet 4 Main girder 4a Girder end 5 Movable bearing (slip rubber bearing)
6 Upper plate 7 Lower plate 8 Laminated rubber 10 Protrusion 11 Opening 12 Buffer member (laminated rubber)
13 Rubber layer 14, 15, 16 Steel plate 17 Movement prevention frame 19, 20 Slip plate 25 Water stop cover

Claims (8)

In a girder bridge whose main girder end is supported by an abutment via a movable support, a negative reaction force transmission structure for transmitting a negative reaction force acting on the main girder to the abutment,
A protrusion is provided at the tip of the main girder end, and this protrusion is disposed through an opening provided in a parapet of the abutment so that there is a gap above and below the protrusion,
A negative reaction force transmission structure in a girder bridge, wherein a buffer member is provided on the upper surface of the projection, and a gap is provided between the upper surface of the buffer member and the inner surface of the opening.   The negative reaction force transmission structure in a girder bridge according to claim 1, wherein the buffer member has a sliding function.   The negative reaction force transmission structure in a girder bridge according to claim 1, wherein each of the protrusion and the opening has a rectangular cross section.   4. The negative reaction force transmission structure in a girder bridge according to claim 3, wherein the buffer member is of a pad type.   5. The negative reaction force transmission structure in a girder bridge according to claim 4, wherein the buffer member is made of a laminated rubber formed by laminating a steel plate and a rubber layer.   The girder bridge according to any one of claims 2 to 5, wherein a slip plate is provided on an upper surface of the buffer member and an inner surface of the opening in order to give the buffer member a slip function. Negative reaction force transmission structure.   5. The projection is provided with a plurality of anchor bars protruding from an upper surface thereof, and the buffer member is provided with an insertion hole into which the anchor bar is inserted to a predetermined depth position. , 5 or 6 negative reaction force transmission structure in girder bridge.   The negative reaction force transmission structure in a girder bridge according to any one of claims 1 to 7, wherein the movable bearing is a sliding rubber bearing.

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