Abstract:
A base isolation device for a structure capable of efficiently and effectively suppressing the vibration of a structural body in surface outside direction, wherein a tension member having on overall length longer than an interval between support points provided on the structural body at a specified interval is disposed between the support points, one end parts of first link pieces are rotatably connected midway to the tension member directly or through rigid members, one end parts of second link pieces are rotatably connected to the structural body, the other end parts of the first link pieces are rotatably connected to the other end parts of the second link pieces, and an energizing member providing a tension to the tension member by energizing the first link piece and the second link piece and a damping member operated by the rotation of the first link piece and the second link piece are installed between the structural body forming the structure and connection parts between the first link pieces and the second link pieces.

Description:
This application is a national filing pursuant to 35 U.S.C Section 371 based on PCT/JP02/13630, filed Dec. 26, 2002. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a base isolation device for a structure, and more particularly to a base isolation device for a structure that is applied to a structure having structural members such as slabs in elevated freeways, elevated railway tracks, or bridge constructions, and suppresses vibration in the out-of-plane direction of the structural members. 
   Moreover, the invention can also be applied to a base isolation device that suppresses vibration in the out-of-plane direction of structural members of an inclined roof, or structural-support members of a vertically placed glass curtain wall. 
   2. Description of the Related Art 
   In recent years, various measures have been employed for suppressing damage such as collapse or failure of structures comprising structural elements such as the slabs in elevated freeways, elevated railway tracks, or bridge constructions due to vertical vibration of the structural members that occurs during traffic vibration or an earthquake, and one of the measures that has been proposed is the base isolation device shown in  FIG. 5 . 
   The base isolation device that is indicated by reference number  1  in this  FIG. 5 , is applied to a floor slab  3  that is arranged horizontally as a structural member that is supported by a plurality of bridge supports  2 , for example, and underneath the floor slab  3 , in about the center between the bridge supports  2 , an elastic member  4  comprising a spring or the like, and a damping member  5  comprising an oil damper or the like are suspended such that they are parallel with each other, and a weight member  6  is attached to the bottom section of the elastic member  4  and damping member  5 . 
   In this prior base isolation device  1  constructed in this way, when vibration in the out-of-plane direction (in the vertical direction in the example shown in the  FIG. 5 ) occurs in the floor slab  3 , the vertical vibration of the floor slab  3  is suppressed by damping the relative motion between the floor slab  3  and the weight member  6  by the elastic member  4  and damping member  5 . 
   In this kind of prior art, there still remain the following problems that must be improved. 
   In other words, in the prior art described above, in order to efficiently suppress the vertical vibration in the floor slab  3 , it is necessary to properly set the elastic coefficient of the elastic member  4  and the damping coefficient of the damping member  5  in accordance to the characteristic natural frequency of the floor slab  3 , however, in order to do this, there is a problem in that the range capable of obtaining an effective base isolation function is narrow, and the setting of which is difficult. 
   Moreover, the weight member  6  is more effective the heavier it is, however, in an actual structure, it was difficult to attach a weight that was 10% the weight of the entire structure. 
   Furthermore, since the weight member  6  acts only in the direction of gravitational acceleration, installing this prior base isolation device in the structural members of an inclined roof, or the structural-support members of a vertically placed glass curtain wall was impossible. 
   SUMMARY OF THE INVENTION 
   Taking these prior problems into consideration, the object of this invention is to provide a base isolation device for a structure that is capable of effectively suppressing vibration in the out-of-plane direction of the structural members of a structure. 
   In order to accomplish the object described above, the base isolation device for a structure according to the first embodiment of the invention is a base isolation device for a structure that suppresses vibration in the out-of-plane direction of a structural member of the structure and comprises: In the base isolation device for a structure according to the seventh embodiment of the invention, the damping member of any one of the described embodiments is an active damper, and together with locating a sensor for detecting shaking on said structural member, a controller is installed that adjusts the operation of said active damper based on the detection signal from the sensor. 
   In the base isolation device for a structure according to the eighth embodiment of the invention, the sensor of the seventh embodiment is an acceleration sensor. 
   In the base isolation device for a structure according to the ninth embodiment of the invention, the sensor of the seventh embodiment is a displacement sensor. 
   In the base isolation device for a structure according to the tenth embodiment of the invention, the sensor of the seventh embodiment is a velocity sensor. 
   In the base isolation device for a structure according to the eleventh embodiment of the invention, the damping member of any one of the described embodiments is a viscoelastic member or elasto-plastic member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view showing the main parts of a first embodiment of the present invention. 
       FIG. 2  is a plane view showing the main parts of a first embodiment of the present invention. 
       FIG. 3  is an enlarged view of the main parts for explaining the operation of a first embodiment of the present invention. 
       FIG. 4  is a front view showing another embodiment of the present invention. 
       FIG. 5  is a front view of the main parts of a prior example. 
       FIG. 6  is a front view showing another embodiment of the present invention. 
       FIG. 7  is a front view showing another embodiment of the present invention. 
       FIG. 8A  and  FIG. 8B  are front views showing examples of modifications to the present invention. 
       FIG. 9  is a plane view showing an example of a modification to the present invention. 
       FIG. 10  is a front view showing an example of a modification to the present invention. 
       FIG. 11  is a front view showing an example of a modification to the present invention. 
       FIG. 12  is a front view showing an example of a modification to the present invention. 
       FIG. 13A ,  FIG. 13B  and  FIG. 13C  are front views showing examples of modifications to the present invention. 
       FIG. 14  is a front view showing an example of a modification to the present invention. 
       FIG. 15  is a front view showing an example of a modification to the present invention. 
       FIG. 16  is a front view showing an example of a modification to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A first embodiment of the present invention will be explained below with reference to  FIG. 1  to  FIG. 3 . 
   The base isolation device  10  for a structure of this embodiment, which is indicated by the reference number  10  in  FIG. 1 , is applied to a floor slab  12 , which is a structural member that is supported by a plurality of bridge supports  11 , and is basically constructed by comprising: support points  13  that are located underneath the floor slab  12  and separated by a specified space (in this embodiment, they are located on adjacent bridge supports  11 ), and where a tension member  14  is placed in between these support points  13  having an overall length that is longer than the space, and where first link pieces  15  are connected to points along the tension member  14  such that they can rotate freely, and second link pieces  16  that are connected between the first link pieces  15  and the floor slab  12  such that they can rotate freely; an energizing member  17  that applies tension to the tension member  14  by energizing the first link pieces  15  and second link pieces  16  between the connections of the first link pieces  15  and second link pieces  16  and the structural member of the structure (floor slab  12  in this embodiment); and a damping member  18  that is operated by the rotation of the first link pieces  15  and second link pieces  16 . 
   Also, there is an added mass  25  located in the connections  21  between the first link pieces  15  and second link pieces  16 . 
   To explain these in more detail, in this embodiment, rope is used as the tension member  14  and both ends are fastened to the support points  13  that are located on the bridge supports  11 . 
   In this embodiment, the first link pieces  15  and second link pieces  16  are located underneath the floor slab  12 , and are located at two places separated by a space midway in the space between adjacent bridge supports  11  in the length direction of the tension member  14 , and one end of each of the first link pieces  15  is connected to the tension member  14  by way of a pin  19  such that it can rotate freely, and one end of each of the second link pieces  16  is connected to the bottom of the floor slab  12  by way of a pin  20  such that it can rotate freely. 
   Moreover, the other end of each of the first link pieces  15  and second link pieces  16  are connected together by way of a pin  21  such that they can rotate freely, as well as an added mass  25  is added, and furthermore, the first link pieces  15  are formed such that they are shorter than the second link pieces  16 , and the pins  21  of the connections between the first link pieces  15  and second link pieces  16  are located on the inside between both pins  19  of the connections between the first link pieces  15  and the tension members  14 . 
   Furthermore, in this embodiment, as shown in  FIG. 2 , base isolation devices  10  are mounted between a pair of bridge supports  11  that are located such that they are parallel in the plane direction of the floor slab  12 , and the two pins  21  that connect the first link pieces  15  and second link pieces  16  of each base isolation device  10  are shared, and they (pins  21 ) are made sufficiently heavy in order that they can take on the role of the added mass  25 , and a pair of energizing members  17  are located in parallel between these pins  21 , and furthermore a damping member  18  is located between these energizing members  17  and is connected to both pins  21 . 
   Also, both energizing members  17  are constructed using tension springs, and by energizing both pins  21  in a direction such that they approach each other, and by energizing the pins  19 , which are the connections of each of the first link pieces  15  with the tension members  14 , in a direction such that they become separated from the floor slab  12 , tension is applied to the tension members  14  and keeps the tension members  14  in a state of tension. 
   Next, the operation of the base isolation device  10  of this embodiment constructed in this way will be explained. 
   When an earthquake or the like occurs, the floor slab  12  vibrates in the vertical direction, which is the out-of-plane direction of the floor slab  12 , such that the bridge supports  11  are fixed ends, and the middle section bends. 
   Moreover, as shown in  FIG. 3 , when the floor slab  12  bends downward from the normal state as shown by the single-dot dashed line to the state shown by the double-dot dashed line, for example, each of the pins  20  moves downward together with the floor slab  12 , and each of the second link pieces  16  that are connected to the pins  20  receive a force that also similarly moves them downward. 
   However, by keeping the tension members  14  in a state of tension, the positions of the pins  19 , which are one of the connections with the first link pieces  15 , are restricted, so as the second link pieces  16  move downward as described above, the second link pieces  16  are rotated around the center of the pins  19 . 
   The direction of rotation of the first link pieces  15  is in a direction such that the pins  21 , which are the connections with the second link pieces  16 , move away from each other, and inertial force acts together with the gravitational force on the added mass  25  connected directly to the pins  21 . 
   As a result, both of the energizing members  17  located between both pins  21  expand and together with keeping the tension members  14  in a state of tension, the damping member  18  is expanded, and the damping function occurs. 
   From this, the vertical vibration of the floor slab  12  described above, is converted to motion of the added mass  25 , and due to the occurrence of the damping function, the vertical vibration of the floor slab  12  is suppressed. 
   On the other hand, as shown in  FIG. 3 , when the amount of bending of the floor slab  12  is taken to be X, and the amount of displacement in the horizontal direction of the pin  21  is taken to be βX, by constructing an amplification mechanism with the first link pieces  15  and second link pieces  16 , ‘β&gt;&gt;1’, and as a result, the amount of operation of the damping member  18  increases, and by taking the mass of the added mass  25  to be m′, then that movement is βm′··X, from lever theory, the inertial force acting on the floor slab  12  is β2m′··X, and the added mass  25  has actual motion m′β2, so the mass effect increases. 
   Also, when the floor slab  12  vibrates upward, movement is in the direction that will do away with the state of tension of the tension members  14 , however, by always having both pins  21  be energized by the energizing members  17  in the direction toward each other, the state of tension in the tension members  14  described above is maintained. 
   Therefore, the movement of the first link pieces  15  or the damping member  18  is in the opposite direction from the direction described above, and by the same amplification mechanism, the damping effect is increased. 
   As a result, an effective damping function for vertical vibration, which is the out-of-plane direction of the floor slab  12 , is obtained, and thus it is possible to obtain an elevated isolation function. 
   The shape and dimensions of the components shown for the embodiment described above are examples, and various modifications are possible based on the design requirements. 
   For example, in the embodiment described above, an example was given of constructing the tension member  14  with rope, however, instead of this, it is also possible to construct it using a plurality of steel rods  14   a ,  14   b ,  14   c  as shown in  FIG. 4 . 
   Also, an oil damper was shown as an example of the damping member  18 , however, instead of this, it is also possible to use a viscoelastic member or elasto-plastic member. 
   Also, as shown in  FIG. 6 , it is also possible to install connection legs  22  to the tension member  14 , and to connect the ends of the first link pieces  15  to these connection legs  22  by way of pins  19  such that they can rotate freely, and it is also possible to install, for example, weights  23  to the pins  21  to increase the inertial mass of the moving parts of the base isolation device  10 . 
   Moreover, it is possible to used an active damper for the damping element  18 , and as shown in  FIG. 7 , to install a sensor  24  to the floor slab  12  that detects shaking of the floor slab  12 , and further, it is possible to install a controller  25  that adjusts the opening of a variable orifice based on a detection signal from the sensor  24 , and adjust the damping force of the damping member  18  to a proper value by adjusting the opening of the variable orifice with this controller  25  according to the amount of shaking detected by the sensor  24 . 
   Also, a displacement sensor that detects the amplitude of vibration of the floor slab  12  during vibration, or an acceleration sensor that detects the acceleration of shaking of the floor slab  12  can be used as the sensor  24 . 
   Besides the example of structural members described above, man-made ground such as that of a footbridge, bridge over railway tracks, multi-level parking structure, or elevated walkway is also feasible. 
   An example was given in which support points  13  were located on the bridge supports  11 , however, they could also be located on the floor slab  12 , which is the structural member. 
   This embodiment could also be used as a base isolation device that suppresses the vibration in the out-of-plane direction of the structural members of an inclined roof, or the structural-support members of a vertically standing glass curtain wall. 
   On the other hand, the connected state of the first link pieces  15  and second link pieces  16 , and tension member  14 , as well as the position of the energizing member  17  and damping member  18  can be changed as appropriate. 
   For example, as shown in  FIG. 8A , construction is also possible in which a rectangular-shaped frame member  26  as shown in  FIG. 9 , is placed underneath the floor slab  12 , and this frame member  26  is supported by running tension members  14  between each corner of this frame member  26  and the bridge supports  11  or floor slab  12 , and the end sections of a pair of parallel sides of this frame member  26  and the floor slab  12  are connected by the first link pieces  15  and second link pieces  16 , which are connected such that they can rotate freely, and furthermore, the energizing members  17  and damping members  18  are located between the pins  21 , which make up the connections between the first link pieces  15  and the second link pieces  16 , and the pins  27 , which are located on the parallel sides of the frame member  26  and between the pins  21 . It is also possible to reverse the top and bottom as shown in  FIG. 8B . 
   Here, the pins  21  that connect the first link pieces  15  and second link pieces  16  are located further on the inside of the frame member  26  than the straight lines that connect the pins  19  and pins  20 . 
   Moreover, the energizing members  17  comprise compression springs, and by energizing both pins  21  with these energizing members  17  in a direction such that they move apart from each other, the frame member  26  is energized downward, and a constant tensile force acts on the tension members  14 . 
   Furthermore, as shown in  FIG. 10 , construction is also possible in which pins  20  are located underneath the floor slab  12  and separated by a set space, the second link pieces  16  are connected to these pins  20  such that they can rotate freely, and the first link pieces  15  are connected to the other end of the second link pieces  16  by way of pins  21  such that they can rotate freely, and furthermore the other ends of the first link pieces  15  are connected to the ends of a connection link piece  28 , which is placed such that it is parallel with the line that connects both pins  20 , by way of pins  19 , the energizing member  17  and damping member  18  are located between the pins  21 , and the tension members  14  running between both ends of the connecting link  28  and the floor slab  12  or bridge supports  11 . 
   Here, the pins  21  are located further on the outside than the lines that connect the pins  19  and pins  20 , and the energizing member  17  comprises a tension spring, such that by having the energizing member  17  energize the pins  21  in a direction approaching each other, the connection link piece  28  is energized downward and constant tensile force is applied to the tension members  14 . 
   Also, as shown in  FIG. 11 , construction is also possible in which the pins  21  are located further on the inside than the lines that connect the pins  19  and pins  20 , and the energizing member  17  is a compression spring that energizes both pins  21  such that they move apart from each other. 
   Also, as shown in  FIG. 12 , construction is also possible in which the pair of second link pieces  16  shown in the modification of  FIG. 10  are connected by one pin  20 , and furthermore, the other ends of the pair of first link pieces  15 , which are connected to the other ends of these second link pieces  16  such that can rotate freely, are connected to the tension member  14  by way of one pin  19 . 
   Also, a damping member  18  and energizing member  17  are placed between the pins  21  that connect the first link pieces  15  and the second link pieces  16 , and in this example, this energizing member  17  is constructed using a tension spring. 
   Furthermore, as shown in  FIG. 13A , construction is also possible in which the other ends of the pair of first link pieces  15  shown in  FIG. 12  are connected on the inside of the pair of second link pieces  16  by pin  19 , which is above both pins  21 , and a downward facing connection rod  29  is connected to this pin  19 , and this connecting rod  29  is connected to the tension member  14 . 
   Also, as shown in  FIG. 13B , the energizing member  17  can be placed between the pin  20  and the pin  19 , or the position of this energizing member  17  and the damping member  18  could be switched. 
   Also, the tension member  14  can be connected to the first link pieces  15 ,  15  as shown in  FIG. 13C . 
   Moreover, as shown in  FIG. 14 , construction is possible in which the other ends of the pair of first link pieces  15  shown in  FIG. 13  are located further on the outside than the second link pieces  16 , and the other ends of these first link pieces  15  and the tension member  14  are connected by a connection plate  30  shown by the dot dashed line in  FIG. 14  such that they can rotate freely. 
   Furthermore, as shown in  FIG. 15 , this embodiment can be applied to a wall structure such as a curtain wall to suppress vibration of the curtain wall or the like. Also, damping members  17  can be installed as shown in  FIG. 16 . 
   In any of these modifications, the same functional effect as the embodiment described above can be obtained. 
   Furthermore, the case of the floor slab  12  being in a horizontal state was explained, however, the present invention can all be used as a base isolation device for suppressing vibration in the out-of-plane direction of structural members of an inclined roof, or the structural-support members of a vertically standing glass curtain wall. 
   INDUSTRIAL APPLICABILITY 
   As explained above, with the base isolation device for a structure of this present invention, by transmitting vibration in the out-of-plane direction of a structure such as a floor slab directly to a damping member, the operation of this damping member is performed, and by magnifying the vibration in the out-of-plane direction of a structural member and transmitting it to the damping member, the amount of operation of this damping member is greatly increased, and it absorbs the energy that accompanies the vibration of the structural member, and thus it is possible to maintain the function of base isolation of the structural member.