JP2007297792A - Locking structure of side block in bridge bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a locking structure of a side block capable of releasing the limitation of the movement of a rubber bearing by horizontally moving the side block without rotating. <P>SOLUTION: This locking structure comprises a first locking means allowing the horizontal movement of the side block 8 in the direction perpendicular to the axis of a bridge but stopping the rotation thereof in the vertical direction and a second locking means normally limiting the horizontal movement of the side block 8 and allowing the horizontal movement of the side block 8 in the direction perpendicular to the axis of the bridge when a predetermined horizontal force or larger is applied to the side block. The first locking means comprises an elongated hole 11 formed at the side block 8 along the direction perpendicular to the axis of the bridge and a fastening member 12 inserted into the elongated hole 11 the upper end of which is engaged with the side block 8, and the lower end of which is secured to a base plate 4. The second locking means has a buckling member 20 deformed by buckling when a predetermined horizontal force or larger is applied to the side block. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure for fixing a side block in a bridge support. It relates to the fixing structure of the side block.

  Rubber bearings are known as one of the bridge supports. In general, the rubber bearing is movable in the bridge axis direction by shear deformation so as to absorb expansion and contraction and seismic motion due to temperature changes of the superstructure. On the other hand, in the direction perpendicular to the bridge axis, the movement is restricted by the side block supporting the rubber bearing.

  However, if the side block restricts the movement of the rubber bearing even when the seismic motion exceeds a predetermined level, that is, the horizontal force due to the seismic motion exceeding Level 1, excessive force is applied to the substructure such as the bridge pier, causing damage or the like. In view of this, a side block has been proposed that incorporates a mechanism for releasing the movement restriction on the rubber bearing when a predetermined horizontal force is applied to the upper structure (see Patent Documents 1 and 2). Level 1 seismic motion refers to the seismic motion shown in “Road Bridge Specification (V Seismic Design) / Description” (Japan Road Association).

According to these prior arts, the movement restriction by the side block can be released by rotating the side block supported by the buckling mechanism (Patent Document 1) or by breaking the side block by torsion. However, since these conventional techniques rotate the side block in the vertical direction, the height position of the support point of the side block with respect to the rubber bearing changes with rotation, so that the structure is only complicated. In addition, the calculation of the design strength becomes complicated.
JP-A-2005-76195 JP 2005-127031 A

The present invention has been made based on the technical background as described above, and achieves the following object.
An object of the present invention is to provide a fixing structure of a side block that can release the restriction of movement of the rubber bearing by horizontally moving the side block without rotating.

  Another object of the present invention is not to adversely affect the lower structure and the upper structure by gradually reducing the horizontal support force to the rubber bearing when releasing the movement restriction of the side block in addition to the above object. It is in providing the fixing structure of a side block.

The present invention employs the following means in order to achieve the above object.
That is, the present invention is a side block fixing structure that is installed on both sides in the bridge axis direction of the rubber bearing on the base plate and limits shear deformation in the direction perpendicular to the bridge axis of the rubber bearing,
First fixing means for allowing horizontal movement of the side block in a direction perpendicular to the bridge axis but preventing rotation in the vertical direction;
The horizontal movement of the side block is always limited, and when the horizontal force of a predetermined level or more is applied to the side block, the second fixing means for allowing the horizontal movement in the direction perpendicular to the bridge axis is provided. It is in a fixed structure.

  The first fixing means includes, for example, an elongated hole provided in the side block along a direction perpendicular to the bridge axis, an upper end portion inserted into the elongated hole and engaged with the side block, and a lower end portion of the base plate. The structure which consists of a fastening member fixed to can be employ | adopted.

  Further, the second fixing means may employ a configuration having a buckling member that buckles and deforms when a predetermined horizontal force is applied to the side block. In this case, the second fixing means has a slot having a stepped portion provided on the lower surface of the side block, and a slot provided on the upper surface of the base plate so as to align with the slot. The buckling member may employ a configuration comprising a shear key fitted over the stepped portion of the slot of the base plate and the slot of the side block.

  As the shear key, a normal steel material can be used, but a low yield point steel may be used.

  According to this invention, when a predetermined horizontal force or more is applied to the side block due to the earthquake motion, the side block moves only in the horizontal direction without rotating in the vertical direction. For this reason, the height position of the support point of the side block with respect to the rubber bearing does not change, and an ideal side block release pattern is obtained. Therefore, the overall structure of the side block is simplified, and the calculation of the design strength is also simplified.

  Moreover, since the supporting force of the side block is imposed on the buckling member, the supporting force is gradually reduced instead of abruptly. Therefore, no impact force is applied to the upper structure and the lower structure, and no adverse effect is caused.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view in the direction of the bridge axis showing a bridge support using a rubber support, and FIG. 2 is a view in the direction perpendicular to the bridge axis. The rubber bearing 1 is installed between a lower structure 2 such as a pier or an abutment and an upper structure 3 including a bridge girder.

  A base plate 4 is fixed on the lower structure 2 by anchor bolts (not shown). The rubber support 1 includes a laminated rubber 5 formed by alternately laminating rubber layers and steel plates, and an upper rod 6 and a lower rod 7 fixed to the upper and lower portions thereof. The lower rod 7 is fixed to the base plate 4, and the upper rod 6 is fixed to the upper structure 3.

  The side blocks 8 are fixed on the base plates 4 on both sides along the bridge axis direction of the rubber bearing 1. The side block 8 includes a base portion 9 and an upright portion 10 that rises from the center thereof. By engaging the end portion of the upper flange 6 protruding from the laminated rubber 5 with the upright portion 10, shear deformation in the direction perpendicular to the bridge axis of the rubber bearing 1, that is, horizontal movement of the upper structure 3 in the same direction is limited.

  3 is a cross-sectional view showing the fixing structure of the side block, FIG. 4 is a plan view, and FIG. 5 is a cross-sectional view taken along line A in FIG. A plurality of elongated holes 11 are provided on both sides of the base portion 9 with the upright portion 10 interposed therebetween, on the rubber support 1 side. These long holes 11 are provided along the direction perpendicular to the bridge axis, and open at the end surface facing the rubber bearing 1. Bolts 12 are inserted into the deep portions of the long holes 11, and screw portions 13 formed at the lower end portions of the bolts 12 are screwed to the base plate 4.

  For each of the two long holes 11 groups on both sides of the upright portion 10, a seat plate 14 is disposed so as to cross each long hole. Each bolt 12 is inserted into the elongated hole 11 through a hole in the seat plate 14, and the bolt head 16 is engaged with the seat plate 14 through a washer 15. The tightening of the bolt 12 is not strong, and instead, an adhesive for preventing loosening is applied to the screw portion 13.

  A slot 17 is provided along the bridge axis direction on the lower surface of the base portion 9 on the side opposite to the rubber support 1. The slot 17 is a two-stage slot having a stepped portion 18. In the drawing, a slot portion deeper than the stepped portion 18 is indicated by reference numeral 17a. On the other hand, a slot 19 is provided on the upper surface of the base plate 4 in contact with the base portion 9 so as to align with the slot 17. A shear key 20 that is a buckling member is fitted over the slot 19 and the stepped portion 18 of the slot 17 of the base portion 9. As the shear key 20, a normal steel material can be used, but a low yield point steel may be used. This is because low yield point steel has little variation in yield load, and buckling occurs smoothly at a load close to the design value.

  Next, the operation of the side block will be described with reference to FIGS. FIG. 8 is a load-displacement curve showing the relationship between the load (supporting force) acting on the side block and the displacement. When a horizontal force in the direction perpendicular to the bridge axis acts on the upper structure 3 due to the earthquake motion, the force is transmitted to the side block 8 via the upper arm 6 of the rubber bearing 1. Here, if the seismic motion is level 1 or less, as shown in FIG. 6A, the shear key 20 generates only a slight elastic strain in the elastic region, and the side block 8 is hardly displaced ( (Refer the (a) part of the load-displacement curve of FIG. 8).

  On the other hand, when a seismic motion exceeding level 1 occurs and the horizontal force acts on the side block 8, the shear key 20 buckles and the bent portion is behind the stepped portion 18, as shown in FIG. It deform | transforms in the form which penetrates into the slot part 17a. When the buckling of the shear key 20 starts, the support force of the side block 8 reaches the maximum support force. As shown in FIG. 7, the side block 8 starts to move horizontally in the direction perpendicular to the bridge axis, and the rubber bearing 1 Shear deformation is possible in the direction perpendicular to the bridge axis.

  At this time, a vertical rotational moment acts on the side block 8, but the bolt 12 resists by its tensile force, and therefore the side block 8 does not rotate. On the other hand, since the bolt 12 is inserted into the elongated hole 11 extending in the direction perpendicular to the bridge axis, after all, slip occurs between the seat plate 14 and the side block 8, and the side block 8 moves only in the horizontal direction. . The frictional force during the horizontal movement of the side block 8 has a weak bolt tightening force as described above and is negligible compared to the earthquake force. Does not give. In order to further reduce the frictional resistance, a thin Teflon (registered trademark) plate may be provided on the lower surface of the side block 8 and the lower surface of the seat plate 14.

  Due to the horizontal movement of the side block 8, as shown in FIG. 6C, the shear key 20 is further plastically deformed. For this reason, the supporting force of the side block 8 is not lost suddenly but gradually decreases (see the portions (b) to (c) of the load-displacement curve in FIG. 8). As shown in FIG. 6 (d), the shear key 20 eventually breaks in shear, and the supporting force of the side block 8 (the amount borne by the shear key 20) becomes zero (the load of FIG. 8− (See (d) of the displacement curve). The supporting force of the side block 8 becomes completely zero when the bolt 12 is pulled out of the elongated hole 11 and the side block 8 is detached from the base plate 4.

  As described above, when a horizontal force is applied to the side block 8 due to the earthquake motion exceeding level 1, the side block 8 moves only in the horizontal direction without rotating in the vertical direction. For this reason, the height position of the support point of the side block 8 with respect to the upper collar 6 does not change, and an ideal side block release pattern is obtained. Therefore, the overall structure of the side block is simplified, and the calculation of the design strength is also simplified.

  Further, since the supporting force of the side block 8 is borne by the shear key 20 that buckles and deforms, the supporting force is gradually reduced instead of abruptly. Therefore, no impact force is applied to the upper structure 3 and the lower structure 2, and no adverse effects are caused. Further, since the shear key 20 is fitted in the slots 17 and 19 provided in the side block 8 and the base plate 4 respectively, it is not exposed to the outside, and its function can be maintained for a long time. Furthermore, for the restoration of the side block after a large earthquake, it is only necessary to replace the shear key 20 with a new one, so that the restoration work can be easily performed.

  The above embodiment is merely an example, and the present invention can take various aspects. For example, in the above embodiment, only one slot for fitting the shear key is provided for each of the side block and the base plate, but a plurality of slots may be provided.

It is a bridge-axis direction arrow directional view which shows the bridge bearing using a rubber bearing. It is a bridge axis perpendicular direction view of the same bearing. It is sectional drawing which shows the detail of a side block. It is a top view of the side block. FIG. 4 is an arrow view taken along line A in FIG. 3. It is a figure which shows the deformation | transformation of the shear key accompanying the horizontal movement of a side block. It is a bridge-axis direction arrow directional view which shows the horizontal movement state of a side block. It is a figure which shows the load-displacement curve of a side block.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rubber support 2 Lower structure 3 Upper structure 4 Base plate 5 Laminated rubber 6 Upper collar 7 Lower collar 8 Side block 9 Base part 10 Standing part 11 Long hole 12 Bolt 13 Screw part 14 Seat plate 16 Bolt head 17 Groove hole 17a Stepped Slot part at the back of the part 18 Stepped part 19 Slot 20 Shear key

Claims (5)

A side block fixing structure that is installed on both sides of the rubber bearing in the bridge axis direction on the base plate and restricts shear deformation in a direction perpendicular to the bridge axis of the rubber bearing,
First fixing means for allowing horizontal movement of the side block in a direction perpendicular to the bridge axis but preventing rotation in the vertical direction;
The horizontal movement of the side block is always limited, and when the horizontal force of a predetermined level or more is applied to the side block, the second fixing means for allowing the horizontal movement in the direction perpendicular to the bridge axis is provided. Fixed structure.   The first fixing means includes an elongated hole provided in the side block along a direction perpendicular to the bridge axis, and the upper end portion is inserted into the elongated hole to engage the side block, and the lower end portion is fixed to the base plate. The fixing structure of the side block in the bridge support according to claim 1, wherein the fixing structure is a fastening member.   3. The side block of the bridge support according to claim 1, wherein the second fixing means includes a buckling member that is buckled and deformed when a predetermined horizontal force is applied to the side block. 4. Fixed structure. The second fixing means includes a slot having a stepped portion provided on the lower surface of the side block, and a slot provided on the upper surface of the base plate so as to be aligned with the slot.
4. The structure for fixing a side block in a bridge support according to claim 3, wherein the buckling member comprises a shear key fitted over the stepped portion of the slot of the base plate and the slot of the side block.   The structure for fixing a side block in a bridge support according to claim 4, wherein the shear key is made of low yield point steel.

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