JP2016160696A - Reinforcement method of existing base-isolated building - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reinforcement method of an existing base-isolated building capable of securing both base isolation performance against a middle or small earthquake and an earthquake at an earthquake motion level of the original design and safety against a greater earthquake than was assumed in the original design.SOLUTION: In a base isolation layer 3, a displacement-changeover-type passive damper 10 that switches from a low attenuation mode to a high attenuation mode at a preset displacement is installed.SELECTED DRAWING: Figure 1

Description

  The present invention provides a method for reinforcing existing seismic isolation buildings to achieve both seismic isolation performance against small and medium earthquakes and earthquakes assumed at the beginning of design and safety against huge earthquakes exceeding the assumptions at the time of design. It is about.

  Following the occurrence of the 2011 off the Pacific coast of Tohoku Earthquake, the hypocenter region of a subduction-zone giant earthquake along the Nankai Trough has been reviewed, and an increase in the probability of an inland earthquake has been warned. By the way, there are concerns about the occurrence of long-period and long-time ground motions with large amplitudes and frequent repetitions in the subduction-zone giant earthquakes. In addition, large-scale pulsed ground motions are feared in inland earthquakes.

  On the other hand, in order to ensure the safety of the building against the earthquake before the occurrence of the Tohoku-Pacific Ocean Earthquake, as shown in FIG. 8, for example, the base 4 of the building 1 is seismically isolated by laminated rubber or a sliding bearing. A seismic isolation layer 3 with a device (laminated rubber bearing is shown in the figure) 2 is formed to reduce vibrations that are transmitted from the foundation 4 side to the building 1 due to an earthquake or the like. Between these, various passive seismic isolation systems are employed that actively dampen the above-described vibrations through dampers 5 such as viscoelastic dampers and oil dampers.

  However, the existing base-isolated building having the above-described structure has a feature that when the seismic force more than expected is applied, the deformation of the base-isolated layer 3 rapidly increases. If the earthquake motion greatly exceeds 1, the building 1 may collide with the retaining wall 6, or the seismic isolation device 2 may be damaged.

  As a conventional technique for suppressing the damage caused by the excessive deformation of the seismic isolation layer 3, for example, a fender or a shock absorber is used on the assumption that the building 1 collides with the retaining wall 6 in the event of a huge earthquake. Although there are attempts to reduce the impact force by interposing, there is a problem that the movable displacement in the seismic isolation layer 3 is narrowed and sufficient energy absorption cannot be realized.

  In addition, in order to suppress the above-described collision and improve the safety of the building 1, a reinforcing method for increasing the damping force by adding a damper 5 to the base isolation layer 3 has been proposed.

  However, in the above-described conventional reinforcing method, the damping force of the damper 5 can be increased to suppress the deformation of the seismic isolation layer 3 in the event of a huge earthquake that exceeds the expected level. There is a problem that the response acceleration of the building 1 at the time of an earthquake or an initial ground motion level (equivalent to level 2) increases and the seismic isolation performance deteriorates.

JP 2006-144346 A

  The present invention has been made in view of the above circumstances, and it is possible to achieve both seismic isolation performance against small and medium earthquakes and earthquakes assumed at the initial stage of design and safety against huge earthquakes exceeding the initial design assumptions. It is an object to provide a method for reinforcing existing seismic isolation buildings.

  In order to solve the above-mentioned problem, the invention described in claim 1 is a method for reinforcing an existing seismic isolation building, wherein the seismic isolation layer is a displacement switching type that switches from a low attenuation mode to a high attenuation mode with a preset displacement. The passive damper is installed.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the displacement for switching from the low attenuation mode to the high attenuation mode is set in a range of 20 cm to 40 cm. is there.

  Furthermore, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the displacement-switching passive damper is connected to the existing base isolated building with respect to the displacement direction at the time of the earthquake of the existing base isolated building. The displacement-switching passive damper located on the front side of the center of gravity is installed so that the damping force of the displacement-switching passive damper located on the rear side is smaller than the damping force of the displacement-switching passive damper located on the rear side. .

  According to the invention described in any one of claims 1 to 3, a displacement-switching passive damper that switches from a low attenuation mode to a high attenuation mode with a preset displacement is installed in a base isolation layer of an existing base isolation building. Therefore, in normal times, by keeping the damping coefficient of the displacement-switching passive damper at a small value, for small and medium-sized earthquakes and earthquakes of the ground motion level at the initial design stage, the seismic isolation structure is similar to that before the reinforcement. Seismic performance can be demonstrated and the response acceleration of the building can be reduced.

  In addition, if the seismic isolation device in the existing base isolation building is a sliding bearing, there will be no slip for small and medium-sized earthquakes. As a result, the damping effect will not be demonstrated. By applying an appropriate damping force corresponding to the magnitude of the displacement of the seismic isolation layer by the type passive damper, it is possible to improve the seismic isolation performance for the above-mentioned small and medium earthquakes.

  In contrast, when an excessive displacement occurs in the seismic isolation layer due to an earthquake exceeding the initial design assumption, the displacement switching side passive damper switches to the high attenuation mode, and the displacement of the seismic isolation layer is suppressed by a large reduction force. By doing so, it is possible to prevent collision with surrounding structures such as retaining walls and damage to the seismic isolation device.

  The set displacement for switching the displacement-switching passive damper from the low attenuation mode to the high attenuation mode is set to a value equal to or greater than the response displacement generated by the ground motion at the level assumed in the initial design of the existing base-isolated building. A large damping force should be exerted only when subjected to earthquake motion exceeding the design assumptions.

  By the way, in a general base-isolated building whose clearance with surrounding structures is about 60 cm, the response displacement of the base isolation layer with respect to the originally designed ground motion level (level 2) is often about 20 cm to 40 cm. . Therefore, when the reinforcement is applied to such a general existing base-isolated building, the displacement switching type passive damper has a displacement that switches from the low attenuation mode to the high attenuation mode as in the invention described in claim 2. It is preferable to set in the range of 20 cm to 40 cm.

  Furthermore, according to the invention described in claim 3, the displacement-switching passive damper is located on the front side of the center of gravity of the existing base isolated building with respect to the displacement direction at the time of the earthquake of the existing base isolated building. Since the damping force of the displacement-switching passive damper is set to be smaller than the damping force of the displacement-switching passive damper located on the rear side, it is located on the front side in the displacement direction from the center of gravity during a huge earthquake. It is possible to prevent the seismic isolation building from rocking due to the damping force of the displacement switching passive damper.

It is the front view seen from the longitudinal cross-section for demonstrating the 1st Embodiment of this invention. It is the schematic block diagram which looked at the longitudinal cross-section which shows the displacement switching type passive oil damper of FIG. It is a figure which shows the front-end | tip shape of the shut-off valve of FIG. 2, (a) is a perspective view, (b) is the side view. It is the schematic block diagram seen from the longitudinal cross-section which shows the operation state at the time of the big earthquake of the displacement switching type passive oil damper of FIG. It is the front view seen from the longitudinal cross-section for demonstrating the 2nd Embodiment of this invention. It is the schematic block diagram which looked at the longitudinal cross-section which shows the displacement switching type passive oil damper of FIG. It is a longitudinal cross-sectional view which shows the action | operation of the damping valve with a non-return valve of FIG. It is the front view which looked at the longitudinal cross-section which shows the existing seismic isolation building.

(First embodiment)
1-4 is for demonstrating 1st Embodiment which applied the reinforcement method of the existing seismic isolation building which concerns on this invention to reinforcement of the existing seismic isolation building shown in FIG. The same components are denoted by the same reference numerals and the description thereof is simplified.

  In this existing seismic isolation building reinforcement method, a displacement-switching passive oil damper (passive damper) is further added to the seismic isolation layer 3 formed by installing the damper 5 and installing the damper 5. It is characterized by doing.

  The displacement-switching passive oil damper 10 is set to a low attenuation mode in which the attenuation coefficient is smaller than that of the damper 5 in a normal state, and moreover than the damper 5 when a preset displacement occurs in the seismic isolation layer 3. Is switched to a high attenuation mode.

  2 to 4 show an example of the displacement switching type passive oil damper 10 described above. The displacement-switching passive oil damper 10 is composed of a cylinder 11 filled with working oil and a piston 12 movably provided in the cylinder 11 and extends outward from the cylinder. A displacement detection rod 14 is integrated in parallel with the rod 13 of the piston 12. At this time, the rod 13 of the piston 12 is fixed to the foundation 4 side, and the cylinder 11 is connected to the building 1 side.

  Further, the piston 12 is formed with a piston flow path 16 in which cylinder chambers 11a and 11b before and after the piston 12 are communicated and a damping valve 15 for high damping mode is interposed. Further, an external flow path 17 for communicating the cylinder chambers 11a and 11b is provided outside the cylinder chambers 11a and 11b. The external flow path 17 includes a damping valve 18 for a low attenuation mode and the external flow path 17. A shut-off valve 19 for opening and closing is provided.

  On the other hand, a displacement detection groove 20 is formed on the upper surface of the detection rod 14, and a shutoff valve 19 is arranged in the displacement detection groove 20 in normal times. As shown in FIG. 3, the shutoff valve 19 is provided in parallel with the external flow path 17 in which the damping valve 18 is interposed in a state of being disposed in the displacement detection groove 20 as shown in FIG. 3. Through holes 19a and 19b for communicating the external channel 21 thus formed are formed, and other portions are formed in a solid cylindrical shape.

  As a result, the displacement-switching passive oil damper 10 operates in a normal state in which the shutoff valve 19 is arranged in the displacement detection groove 20 as shown in FIG. The oil is set to a low damping coefficient by flowing through the damping valve 15 in the piston 12 and the damping valve 18 in the external flow path 18.

  Further, as shown in FIG. 4, the seismic isolation layer 3 is displaced more than expected, and the shutoff valve 19 rises from the displacement detection groove 20 onto the upper surface 14a of the displacement detection rod 14 and rises. , 21 is switched so that the hydraulic oil flows only through the damping valve 15 in the piston 12 to switch to a high damping coefficient.

  Here, in the present embodiment, the length of the displacement detection groove 20 is such that when the shutoff valve 19 is displaced from the normal position in the displacement detection groove 20 by 20 cm to 40 cm relative to the displacement detection rod 14. Are set to run on the upper surface 14a.

  The displacement-switching passive oil damper 10 is maintained when the shut-off valve 19 rides on the upper surface 14a of the displacement detection rod 14 and closes the external flow paths 18 and 21, and the state is maintained manually after the earthquake. It is made to return to the state shown in FIG.

  As described above, according to the method for reinforcing an existing base-isolated building having the above-described configuration, the displacement-switching passive oil damper 10 is newly added to the base-isolated layer 3 of the existing base-isolated building 1. In some cases, the damping coefficient of the displacement-switching passive oil damper 10 is kept smaller than the damping coefficient of the existing damper 5, so that it can be used for small and medium-sized earthquakes and earthquakes at the initial ground motion level. The seismic isolation performance of the base-isolated building 1 before reinforcement can be exhibited by the damper 5 and the response acceleration of the building 1 can be reduced.

  In addition, when an excessive displacement occurs in the seismic isolation layer 3 due to an earthquake exceeding the initial design assumption, the displacement switching side passive oil damper 10 is switched to the high damping mode, and the seismic isolation layer is larger than the damper 5 by a reduced force. By suppressing the displacement 3, it is possible to prevent collision with surrounding structures such as the retaining wall 6 and damage to the seismic isolation device.

(Second Embodiment)
5-7 is a figure for demonstrating the 2nd Embodiment of this invention, and uses the same code | symbol similarly about the component which is common in 1st Embodiment shown in FIGS. 1-4. The description is omitted. This existing seismic isolation building reinforcement method is characterized in that a displacement switching type passive oil damper 30 is added to the seismic isolation layer 3 instead of the displacement switching type passive oil damper 10 shown in the first embodiment. is there.

  As shown in FIGS. 6 and 7, the displacement-switching passive oil damper 30 includes a high-damping mode damping valve 15 and a low-damping mode damping valve in the displacement-switching passive oil damper 10 shown in FIGS. 2 and 3. The damping valve 18 is changed to a damping valve 31 with a check valve for a high damping mode and a damping valve 32 with a check valve for a low damping mode, respectively.

  As shown in FIG. 6, these damping valves 31 and 32 with check valves are shown in FIG. 7A when the compression force is applied from the rod 13 to the piston 12 and the cylinder chamber 11 a side becomes high pressure. As shown in FIG. 7B, when the cylinder 13b is opened by the high pressure hydraulic oil acting from the piston flow path 16 or the external flow path 17 and a tensile force acts on the rod 13 to increase the pressure on the cylinder chamber 11b side. As shown in (2), a large damping force acts only on the tension side by closing with high-pressure hydraulic oil acting from the cinder chamber 11b side.

  When the displacement-switching passive oil damper 30 is added, the displacement-switching passive oil located on the front side of the center of gravity of the existing seismic isolation building 1 with respect to the displacement direction during the earthquake of the existing seismic isolation building 1. The damper 30 is installed so that the damping force is smaller than the damping force of the displacement switching passive oil damper 30 located on the rear side.

  Specifically, in this embodiment, as shown in FIG. 5, the displacement switching type passive oil damper 30 is configured such that the cylinder chamber 11 b of the cylinder 11 is positioned on the outer peripheral side of the building 1, and the cylinder chamber 11 a is It arrange | positions so that it may be located in the gravity center side of the building 1.

  As a result, when a relative displacement indicated by a hollow arrow in the figure occurs in the existing base-isolated building 1 during an earthquake, the displacement-switching passive oil on the right side in the figure is located in front of the center of gravity with respect to the displacement direction. In the damper 30, since the compression force acts on the piston 12 from the rod 13, as shown in FIG. 7A, the damping valves 31 and 32 with check valves are opened by the high-pressure hydraulic oil from the cylinder chamber 11 a. The damping force becomes smaller.

  On the other hand, in the displacement switching type passive oil damper 30 on the left side in the figure located behind the center of gravity with respect to the displacement direction, a tensile force acts on the rod 13, so that FIG. As shown, the damping valves 31 and 32 with check valves are closed by the high pressure hydraulic oil from the cylinder chamber 11b, and the damping force increases.

  Next, when the building 1 is displaced in the direction opposite to the direction indicated by the white arrow, in the displacement switching type passive oil damper 30 on the left side in the figure, which is located in front of the center of gravity with respect to the displacement direction, The compression force is applied from the rod 13 to the piston 12, and the damping valves 31 and 32 with check valves are opened by the high pressure hydraulic oil from the cylinder chamber 11a, so that the damping force is reduced.

  On the other hand, in the displacement switching type passive oil damper 30 on the right side in the drawing, which is located behind the center of gravity with respect to the displacement direction, a tensile force acts on the rod 13 and the reverse is caused by the high pressure hydraulic oil from the cylinder chamber 11b. The damping valves 31 and 32 with stop valves are closed to increase the damping force.

  Therefore, according to the reinforcement method of the existing seismic isolation building shown in 2nd Embodiment, in addition to the effect similar to what was shown in 1st Embodiment, it is further a displacement switching type passive oil damper. 30 with respect to the direction of displacement of the existing base-isolated building 1 when the displacement switching type passive oil damper 30 is located on the rear side of the displacement switching type passive oil damper 30 located on the front side of the center of gravity. Therefore, the building 1 is prevented from rocking due to the damping force of the displacement switching type passive oil damper 30 located in front of the center of gravity in the displacement direction in the event of a huge earthquake. The effect that it can be obtained.

  In the first and second embodiments described above, only the case where the displacement-switching passive oil dampers 10 and 30 are added to the base isolation layer 3 of the existing base isolation building 1 has been described. The present invention is not limited to this, and the present invention can be similarly applied to a case where a part of the existing damper 5 is removed and replaced with the displacement switching passive oil dampers 10 and 30 described above.

  Moreover, in the said embodiment, although it showed about the case where the passive oil dampers 10 and 30 were used as a displacement switching type passive damper, it is not restricted to this, If it has a function which suppresses the shaking of a building, Steel dampers, lead dampers, friction dampers and the like can also be used.

1 building (existing seismic isolation building)
2 Seismic isolation device 3 Seismic isolation layer 5 Damper 10, 30 Displacement switching passive oil damper 31, 32 Damping valve with check valve

Claims (3)

  A method of reinforcing an existing base-isolated building, wherein a displacement-switching passive damper that switches from a low attenuation mode to a high attenuation mode with a preset displacement is installed in the base isolation layer.   The method for reinforcing an existing seismic isolation building according to claim 1, wherein the displacement for switching from the low attenuation mode to the high attenuation mode is set in a range of 20 cm to 40 cm.   The damping force of the displacement-switching passive damper, which is located on the front side of the center of gravity of the existing base-isolated building with respect to the displacement direction at the time of the earthquake of the existing base-isolating building, is The method for reinforcing an existing seismic isolation building according to claim 1, wherein the existing seismic isolation building is installed so as to be smaller than a damping force of the displacement-switching passive damper located in the center.