JP2014077321A - Earthquake strengthening method for existing steel bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an earthquake strengthening method for an existing steel bearing, which capable of eliminating the need for jack-up of a super structure, reducing the number of parts to be replaced, simplifying the construction, and suppressing manufacturing cost to be low.SOLUTION: An earthquake strengthening method for an existing steel bearing includes the steps of: hacking a weld part of a sole plate 8; widening both sides of a bottom flange 4a in a fitting part of an upper shoe 1; fitting stoppers 32, 33 provided so as to leave a predetermined interval apart from the upper shoe along a bridge axial direction and in the direction perpendicular to the bridge axis in an underside of the bottom flange 4a including widened parts 30; and fitting knock-off bolts 37 each having a breaking planned part at its bolt shank intermediate part as new set bolts instead of set bolts so that the breaking planned part is positioned at a boundary surface between the bottom flange and the sole plate 8.

Description

  The present invention relates to a seismic reinforcement method for existing steel bearings, and more particularly to a seismic reinforcement method for existing steel bearings installed between an upper structure and a lower structure in a bridge.

  According to the Road Bridge Specification and Explanation v Seismic Design (2002 Japan Road Association), there are two types of bridge support design methods, Type A and Type B. In addition, it is specified that the performance of the bearing is satisfied with respect to the horizontal force and vertical force generated by the level 2 earthquake motion. On the other hand, the former type A resists the horizontal force and vertical force generated by the level 1 seismic motion only by the bearing unit and complements the displacement limiting structure provided separately for the horizontal force generated by the level 2 seismic motion. It is prescribed.

  For this reason, steel bearings designed with Type A are significantly damaged by Level 2 earthquake motion. 5 to 7 show a multi-roller bearing which is one of steel bearings, where X indicates a bridge axis direction and Y indicates a direction perpendicular to the bridge axis. This roller support itself is well known, and has an upper collar 1, a lower collar 2, and a bottom plate 3.

  The upper arm is fixed to the steel girder 4. More specifically, a sole plate 6 is fixed to the lower surface of the lower flange 4a of the steel girder 4 by welding 5, and a boss 7 on the upper surface of the upper collar 1 is fitted into a boss hole provided in the sole plate 6. At the same time, the plurality of set bolts 9 penetrate the sole plate 6 from the upper surface of the lower flange 4 a and are attached to the plate portion 8 of the upper rod 1, whereby the upper rod 1 is fixed to the steel beam 4.

  The upper rod 1 has a semi-cylindrical portion 10 at the lower portion of the plate portion 8, and the lower rod 2 also has a semi-cylindrical portion 12 at the upper portion of the plate portion 11. These two semi-cylindrical portions 10 and 12 are arranged so that the end faces parallel to the axial direction face each other with a gap therebetween so as to form a cylindrical shape as a whole. As shown in FIG. 5, a pin 13 is fitted inside the two cylindrical portions 10 and 12, so that the upper rod 1 can rotate in a vertical angle range with respect to the lower rod 2 within a predetermined angle range, that is, the upper portion. The steel girder 4 which is a structure is rotatable.

  The pin 13 has a constricted portion 14 in the center, and the constricted portion 14 is fitted with projections 15 and 16 provided along the circumferential direction on the inner circumferences of the two semi-cylindrical portions 10 and 12. As a result, the horizontal load in the direction perpendicular to the bridge axis Y of the upper structure is transmitted to the lower structure 20 via the pins 13. Reference numeral 17 denotes a cap which is attached to both ends of the pin 13 and covers the end faces perpendicular to the axial direction of the two semi-cylindrical portions 10 and 12.

  The bottom plate 3 is fixed to a lower structure 20 such as a pier or an abutment via an anchor bolt 18. A plurality of rollers 21 are arranged between the bottom plate 3 and the plate portion 11 of the lower collar 2. Accordingly, the upper and lower rods 1 and 2 can move in the bridge axis direction X with respect to the bottom plate 3, that is, the steel girder 4 can move in the bridge axis direction X within a predetermined length range (movable support).

  Two side blocks 22 are provided on the bottom plate 3 so as to sandwich the plate portion 11 of the lower rod 2 in the direction Y perpendicular to the bridge axis. On the other hand, notches 23 are provided at both ends of the plate portion 11 along the bridge axis direction X, and the upper portions of the side blocks 22 are inserted into the notches 23. Therefore, the movement of the upper and lower rods 1 and 2 in the bridge axis direction X is limited to the length range of the notch 23. That is, stoppers 24 are formed on both side portions of the notch 23 in the plate portion 11.

  When the roller bearing as described above is subjected to an earthquake motion exceeding level 1, damage as shown in FIG. 8 occurs. That is, as shown in FIG. 5 (a), the seismic motion causes displacement exceeding the upper and lower cages 1 and 2 in the bridge axis direction X, and the stopper 24 shown in FIGS. If it exceeds the strength of the stopper 24, the stopper 24 is destroyed. As a result, the upper structure becomes free and the amount of movement exceeds the limit, so that the roller 21 deviates from the support body, and the support body loses its function.

  In addition, as shown in FIG. 5B, when a seismic force exceeding level 1 is applied to the roller bearing in the direction Y perpendicular to the bridge axis, the constriction of the pin 13 disposed between the upper rod 1 and the lower rod 2 The part 14 cannot be tolerated and is destroyed. After destruction, the upper arm 1 is displaced from the support body in the direction perpendicular to the bridge axis Y, and the support function is lost.

  Patent document 1 can be mentioned as a prior art document relevant to this invention. However, the method described in this document requires jacking up the superstructure and has a large number of parts replacement points.

JP 2011-69191 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 seismic reinforcement method for an existing steel bearing that does not require jacking up of the superstructure, has a small number of parts replacement, is easy to construct, and can be reduced in cost. There is.

The present invention employs the following means in order to achieve the above object.
That is, according to the present invention, the sole plate is fixed to the lower surface of the lower flange of the steel girder by welding, and the upper flange is attached to the upper flange through the sole plate from the upper surface of the lower flange. A seismic reinforcement method for an existing steel bearing fixed by a plurality of set bolts,
Rolling the welded portion of the sole plate;
Widening both sides of the lower flange at the attachment site of the upper collar;
Attaching a stopper along the bridge axis direction and the bridge axis perpendicular direction to the lower surface of the lower flange including the widened portion at a predetermined interval from the upper flange; and
Instead of the set bolt, a knock-off bolt having a planned fracture portion at the middle portion of the bolt shaft portion is used as a new set bolt so that the planned fracture portion is located at the boundary surface between the lower flange and the sole plate. There is a method for seismic reinforcement of an existing steel bearing, characterized by comprising a mounting step.

  In the seismic reinforcement method, the stopper may be provided with a buffer material on a surface facing the upper collar. Moreover, the structure provided with the process of attaching the seat plate for reinforcement to the attachment hole periphery of the said set bolt of the said lower flange upper surface can also be employ | adopted.

  According to the steel bearing reinforced by earthquake resistance according to the present invention, when a horizontal force due to level 2 earthquake motion is applied to the bearing, the set bolt using the knock-off bolt having the planned fracture portion breaks earlier than other bearing components. Then, slip occurs with frictional damping between the lower flange and the sole plate.

  As a result, it is possible to avoid a horizontal force acting on the upper structure, the bearing, and the lower structure from acting. Moreover, the energy at the time of earthquake can be absorbed by friction damping. Moreover, since the upper collar collides with the stopper provided on the lower surface of the lower flange, it is possible to limit excessive movement of the beam due to the slip. Further, the impact force can be absorbed by the cushioning material.

  According to the present invention, when the seismic reinforcement of the existing steel bearing is performed, there is no need to jack up the upper structure, and there is no need to replace any parts other than the set bolt, and therefore the construction is simple and costly. It can be kept inexpensive.

The embodiment of this invention is shown, (a) is a bridge shaft perpendicular direction view of a roller bearing reinforced with earthquake resistance, and (b) is a bridge axis direction view of the support. It is a top view of the support. It is a front view of a knock-off bolt. It is a bridge-axis direction arrow view which shows the effect | action at the time of the earthquake of the same bearing. It is a perspective view of the roller bearing shown as an example of a seismic reinforcement object. It is sectional drawing which shows the pin fitted between an upper collar and a lower collar. The existing roller support is shown, (a) is a bridge axis perpendicular direction view, (b) is a bridge axis direction arrow view. The damage at the time of the earthquake of the existing roller bearing is shown, (a) is a bridge axis perpendicular direction arrow view, (b) is a bridge axis direction arrow view.

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of the present invention. In the plan view shown in FIG. 2, reinforcing ribs to be described later are omitted in order to avoid complication of the drawing. As described with reference to FIG. 7, in the existing roller support, the sole plate 6 on the lower surface of the lower flange 4 a of the steel girder 4 is fixed to the lower flange 4 a by welding 5. Scrape off. The welding operation of the weld 5 can be performed using a machine such as gouging.

  Next, the widening plates 30 and 30 are welded to both sides of the lower flange 4a at the attachment portion of the upper rod 1 to widen the width. The size of the widening plates 30 and 30 is determined with respect to the direction of the bridge axis in consideration of the movement width when further movement is required when the stopper 24 of the bearing works and breaks during a level 2 earthquake. To do. In addition, the direction perpendicular to the bridge axis is determined in consideration of the distance that the superstructure moves due to seismic motion after a new set bolt to be described later breaks. A plurality of reinforcing ribs 31 are attached to the widening plate 30. Specifically, as shown in FIG. 1B, the reinforcing ribs 31 are arranged in a direction perpendicular to the bridge axis and in a vertical direction, and the lower surfaces of the widening plates 30, 30 and the upper surfaces of the widening plates 30, 30 and the lower flange 4a. And these parts are fixed to the web 4b by welding or bolts.

  Next, along the bridge axis direction X and the bridge axis perpendicular direction Y so as to surround the upper rod 1 at a predetermined interval on the lower surface of the lower flange 4a including the widened portion by the widening plates 30, 30. The plurality of stoppers 32 and 33 are fixed by welding or bolts. These stoppers 32 and 33 are provided with a cushioning material 34 such as a rubber plate in advance on the surface facing the upper collar 1. A reinforcing rib 35 fixed to the lower surface of the lower flange 4a is attached to the stopper 33 along the direction Y perpendicular to the bridge axis. The stopper 32 along the bridge axis direction X is reinforced by being fixed to the reinforcing rib 31 of the widening plate 30.

  Next, the existing set bolt 9 shown in FIG. 7 is extracted. Further, a reinforcing seat plate 36 is fixed to the periphery of the set bolt mounting hole on the upper surface of the lower flange 4a by welding. Then, a knock-off bolt 37 as a new set bolt is attached to the hole of the set bolt through the hole of the seat plate 36, and the lower collar 1 and the sole plate 6 are fixed to the lower flange 4a.

  As shown in FIG. 3, the knock-off bolt 37 has an annular notch 39 formed in the middle portion of the bolt shaft portion 38, and the shear fracture strength with respect to the horizontal force of the notch 39 is not limited to other bearing components. It is set smaller than the constricted portion 14 of the pin 13 shown in FIG. 6, and this portion is a planned fracture portion. The knock-off bolt 37 is attached so that the notch portion 39 is located at the boundary surface between the lower flange 4 a and the sole plate 6. In parallel with the above seismic reinforcement work, a rejuvenation method recommended by the Japan Support Association will be implemented to improve the rust prevention and durability of the support.

  According to the roller bearing reinforced with earthquake resistance as described above, when a horizontal force due to level 2 earthquake motion is applied to the bearing, a knock-off bolt 37 is used as shown in FIG. 4 in the case of a horizontal force perpendicular to the bridge axis. The set bolt breaks before the other bearing components, and slips between the lower flange 4a and the sole plate 6 with frictional damping.

  For this reason, it is possible to avoid the application of a horizontal force that causes destruction to the upper structure, the bearing and the lower structure. Moreover, the energy at the time of earthquake can be absorbed by friction damping. Further, since the upper collar 1 collides with the stoppers 32 and 33 provided on the lower surface of the lower flange 4a, it is possible to limit excessive movement of the beam 4 due to slipping. Further, the impact force can be absorbed by the buffer material 34.

  Since the friction coefficient between the lower flange 4a and the sole plate 6 is generally a metal-to-metal friction, it is as large as 0.2, and a large damping force is generated by the friction. Moreover, the slip of both is only at the time of a big earthquake, and slip does not occur at all times. Therefore, it is not necessary to newly install a low friction material such as ethylene tetrafluoride as a sliding material. Further, it is not necessary to consider the lifting of the girders due to the lifting force after the set bolt breaks. This is because the upper part of the bearing is surrounded by the stoppers 33 and 34, so that it is unlikely that the bearing will come off the lower flange.

  In the above embodiment, the case of a roller bearing has been taken as an object of seismic reinforcement. However, this is only an example, and the present invention is fixed and movable if it is a steel bearing installed in a bridge bearing using a steel girder. Regardless of, it can be applied to other steel bearings such as pin bearings.

1 Upper rod 2 Lower rod 3 Bottom plate 4 Steel girder 4a Lower flange 5 Welding 6 Sole plate 9 Set bolt 22 Side block 30 Widening plate 33 Stopper 34 Buffer material 36 Seat plate 37 Knock-off bolt (new set bolt)
39 Notch

Claims (3)

A plurality of set bolts in which a sole plate is fixed to the lower surface of the lower flange of the steel girder by welding, and an upper flange is attached to the upper flange through the sole plate from the upper surface of the lower flange. A method for seismic reinforcement of an existing steel bearing fixed by
Rolling the welded portion of the sole plate;
Widening both sides of the lower flange at the attachment portion of the upper collar;
Attaching a stopper along the bridge axis direction and the bridge axis perpendicular direction to the lower surface of the lower flange including the widened portion at a predetermined interval from the upper flange; and
Instead of the set bolt, a knock-off bolt having a planned fracture portion at the middle portion of the bolt shaft portion is used as a new set bolt so that the planned fracture portion is located at the boundary surface between the lower flange and the sole plate. A method for seismic reinforcement of an existing steel bearing, characterized by comprising the step of attaching. 2. The method for seismic reinforcement of an existing steel bearing according to claim 1, wherein the stopper is provided with a cushioning material on a surface facing the upper collar.   The method for seismic reinforcement of an existing steel bearing according to claim 1 or 2, further comprising a step of attaching a reinforcing seat plate to the periphery of the mounting hole of the set bolt on the upper surface of the lower flange.

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