Base isolation device for structure

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.

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 inFIG. 5.

The base isolation device that is indicated by reference number1in thisFIG. 5, is applied to a floor slab3that is arranged horizontally as a structural member that is supported by a plurality of bridge supports2, for example, and underneath the floor slab3, in about the center between the bridge supports2, an elastic member4comprising a spring or the like, and a damping member5comprising an oil damper or the like are suspended such that they are parallel with each other, and a weight member6is attached to the bottom section of the elastic member4and damping member5.

In this prior base isolation device1constructed in this way, when vibration in the out-of-plane direction (in the vertical direction in the example shown in theFIG. 5) occurs in the floor slab3, the vertical vibration of the floor slab3is suppressed by damping the relative motion between the floor slab3and the weight member6by the elastic member4and damping member5.

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 slab3, it is necessary to properly set the elastic coefficient of the elastic member4and the damping coefficient of the damping member5in accordance to the characteristic natural frequency of the floor slab3, 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 member6is 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 member6acts 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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will be explained below with reference toFIG. 1toFIG. 3.

The base isolation device10for a structure of this embodiment, which is indicated by the reference number10inFIG. 1, is applied to a floor slab12, which is a structural member that is supported by a plurality of bridge supports11, and is basically constructed by comprising: support points13that are located underneath the floor slab12and separated by a specified space (in this embodiment, they are located on adjacent bridge supports11), and where a tension member14is placed in between these support points13having an overall length that is longer than the space, and where first link pieces15are connected to points along the tension member14such that they can rotate freely, and second link pieces16that are connected between the first link pieces15and the floor slab12such that they can rotate freely; an energizing member17that applies tension to the tension member14by energizing the first link pieces15and second link pieces16between the connections of the first link pieces15and second link pieces16and the structural member of the structure (floor slab12in this embodiment); and a damping member18that is operated by the rotation of the first link pieces15and second link pieces16.

Also, there is an added mass25located in the connections21between the first link pieces15and second link pieces16.

To explain these in more detail, in this embodiment, rope is used as the tension member14and both ends are fastened to the support points13that are located on the bridge supports11.

In this embodiment, the first link pieces15and second link pieces16are located underneath the floor slab12, and are located at two places separated by a space midway in the space between adjacent bridge supports11in the length direction of the tension member14, and one end of each of the first link pieces15is connected to the tension member14by way of a pin19such that it can rotate freely, and one end of each of the second link pieces16is connected to the bottom of the floor slab12by way of a pin20such that it can rotate freely.

Moreover, the other end of each of the first link pieces15and second link pieces16are connected together by way of a pin21such that they can rotate freely, as well as an added mass25is added, and furthermore, the first link pieces15are formed such that they are shorter than the second link pieces16, and the pins21of the connections between the first link pieces15and second link pieces16are located on the inside between both pins19of the connections between the first link pieces15and the tension members14.

Furthermore, in this embodiment, as shown inFIG. 2, base isolation devices10are mounted between a pair of bridge supports11that are located such that they are parallel in the plane direction of the floor slab12, and the two pins21that connect the first link pieces15and second link pieces16of each base isolation device10are shared, and they (pins21) are made sufficiently heavy in order that they can take on the role of the added mass25, and a pair of energizing members17are located in parallel between these pins21, and furthermore a damping member18is located between these energizing members17and is connected to both pins21.

Also, both energizing members17are constructed using tension springs, and by energizing both pins21in a direction such that they approach each other, and by energizing the pins19, which are the connections of each of the first link pieces15with the tension members14, in a direction such that they become separated from the floor slab12, tension is applied to the tension members14and keeps the tension members14in a state of tension.

Next, the operation of the base isolation device10of this embodiment constructed in this way will be explained.

When an earthquake or the like occurs, the floor slab12vibrates in the vertical direction, which is the out-of-plane direction of the floor slab12, such that the bridge supports11are fixed ends, and the middle section bends.

Moreover, as shown inFIG. 3, when the floor slab12bends 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 pins20moves downward together with the floor slab12, and each of the second link pieces16that are connected to the pins20receive a force that also similarly moves them downward.

However, by keeping the tension members14in a state of tension, the positions of the pins19, which are one of the connections with the first link pieces15, are restricted, so as the second link pieces16move downward as described above, the second link pieces16are rotated around the center of the pins19.

The direction of rotation of the first link pieces15is in a direction such that the pins21, which are the connections with the second link pieces16, move away from each other, and inertial force acts together with the gravitational force on the added mass25connected directly to the pins21.

As a result, both of the energizing members17located between both pins21expand and together with keeping the tension members14in a state of tension, the damping member18is expanded, and the damping function occurs.

From this, the vertical vibration of the floor slab12described above, is converted to motion of the added mass25, and due to the occurrence of the damping function, the vertical vibration of the floor slab12is suppressed.

On the other hand, as shown inFIG. 3, when the amount of bending of the floor slab12is taken to be X, and the amount of displacement in the horizontal direction of the pin21is taken to be βX, by constructing an amplification mechanism with the first link pieces15and second link pieces16, ‘β>>1’, and as a result, the amount of operation of the damping member18increases, and by taking the mass of the added mass25to be m′, then that movement is βm′··X, from lever theory, the inertial force acting on the floor slab12is β2m′··X, and the added mass25has actual motion m′β2, so the mass effect increases.

Also, when the floor slab12vibrates upward, movement is in the direction that will do away with the state of tension of the tension members14, however, by always having both pins21be energized by the energizing members17in the direction toward each other, the state of tension in the tension members14described above is maintained.

Therefore, the movement of the first link pieces15or the damping member18is 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 slab12, 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 member14with rope, however, instead of this, it is also possible to construct it using a plurality of steel rods14a,14b,14cas shown inFIG. 4.

Also, an oil damper was shown as an example of the damping member18, however, instead of this, it is also possible to use a viscoelastic member or elasto-plastic member.

Also, as shown inFIG. 6, it is also possible to install connection legs22to the tension member14, and to connect the ends of the first link pieces15to these connection legs22by way of pins19such that they can rotate freely, and it is also possible to install, for example, weights23to the pins21to increase the inertial mass of the moving parts of the base isolation device10.

Moreover, it is possible to used an active damper for the damping element18, and as shown inFIG. 7, to install a sensor24to the floor slab12that detects shaking of the floor slab12, and further, it is possible to install a controller25that adjusts the opening of a variable orifice based on a detection signal from the sensor24, and adjust the damping force of the damping member18to a proper value by adjusting the opening of the variable orifice with this controller25according to the amount of shaking detected by the sensor24.

Also, a displacement sensor that detects the amplitude of vibration of the floor slab12during vibration, or an acceleration sensor that detects the acceleration of shaking of the floor slab12can be used as the sensor24.

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 points13were located on the bridge supports11, however, they could also be located on the floor slab12, 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 pieces15and second link pieces16, and tension member14, as well as the position of the energizing member17and damping member18can be changed as appropriate.

For example, as shown inFIG. 8A, construction is also possible in which a rectangular-shaped frame member26as shown inFIG. 9, is placed underneath the floor slab12, and this frame member26is supported by running tension members14between each corner of this frame member26and the bridge supports11or floor slab12, and the end sections of a pair of parallel sides of this frame member26and the floor slab12are connected by the first link pieces15and second link pieces16, which are connected such that they can rotate freely, and furthermore, the energizing members17and damping members18are located between the pins21, which make up the connections between the first link pieces15and the second link pieces16, and the pins27, which are located on the parallel sides of the frame member26and between the pins21. It is also possible to reverse the top and bottom as shown inFIG. 8B.

Here, the pins21that connect the first link pieces15and second link pieces16are located further on the inside of the frame member26than the straight lines that connect the pins19and pins20.

Moreover, the energizing members17comprise compression springs, and by energizing both pins21with these energizing members17in a direction such that they move apart from each other, the frame member26is energized downward, and a constant tensile force acts on the tension members14.

Furthermore, as shown inFIG. 10, construction is also possible in which pins20are located underneath the floor slab12and separated by a set space, the second link pieces16are connected to these pins20such that they can rotate freely, and the first link pieces15are connected to the other end of the second link pieces16by way of pins21such that they can rotate freely, and furthermore the other ends of the first link pieces15are connected to the ends of a connection link piece28, which is placed such that it is parallel with the line that connects both pins20, by way of pins19, the energizing member17and damping member18are located between the pins21, and the tension members14running between both ends of the connecting link28and the floor slab12or bridge supports11.

Here, the pins21are located further on the outside than the lines that connect the pins19and pins20, and the energizing member17comprises a tension spring, such that by having the energizing member17energize the pins21in a direction approaching each other, the connection link piece28is energized downward and constant tensile force is applied to the tension members14.

Also, as shown inFIG. 11, construction is also possible in which the pins21are located further on the inside than the lines that connect the pins19and pins20, and the energizing member17is a compression spring that energizes both pins21such that they move apart from each other.

Also, as shown inFIG. 12, construction is also possible in which the pair of second link pieces16shown in the modification ofFIG. 10are connected by one pin20, and furthermore, the other ends of the pair of first link pieces15, which are connected to the other ends of these second link pieces16such that can rotate freely, are connected to the tension member14by way of one pin19.

Also, a damping member18and energizing member17are placed between the pins21that connect the first link pieces15and the second link pieces16, and in this example, this energizing member17is constructed using a tension spring.

Furthermore, as shown inFIG. 13A, construction is also possible in which the other ends of the pair of first link pieces15shown inFIG. 12are connected on the inside of the pair of second link pieces16by pin19, which is above both pins21, and a downward facing connection rod29is connected to this pin19, and this connecting rod29is connected to the tension member14.

Also, as shown inFIG. 13B, the energizing member17can be placed between the pin20and the pin19, or the position of this energizing member17and the damping member18could be switched.

Also, the tension member14can be connected to the first link pieces15,15as shown inFIG. 13C.

Moreover, as shown inFIG. 14, construction is possible in which the other ends of the pair of first link pieces15shown inFIG. 13are located further on the outside than the second link pieces16, and the other ends of these first link pieces15and the tension member14are connected by a connection plate30shown by the dot dashed line inFIG. 14such that they can rotate freely.

Furthermore, as shown inFIG. 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 members17can be installed as shown inFIG. 16.

In any of these modifications, the same functional effect as the embodiment described above can be obtained.

Furthermore, the case of the floor slab12being 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.