Patent Application
20170044788
This Application claims priority to Japanese Patent Application No. JPA2014-122757, filed 13 Jun. 2014, now Japanese Patent No. 5661964, issued 12 Dec. 2014, the complete disclosure of which is incorporated herein by reference.
The present invention relates to a seismic isolation device capable of safely protecting a building from an earthquake, and especially a laminated rubber bearing equipped with a damper for absorbing energy.
A seismically isolated structure can reduce a response vibration of a building itself caused by strong earthquake ground motions. Therefore, the seismically isolated structure can enhance a holistic seismic safety of an entire building including a skeleton framework as a container and interiors such as furniture and equipment.
In order to realize the seismic isolation of structures, a seismic isolation device needs to have an isolator function capable of largely deforming in horizontal direction while supporting the weight of the building and a damper function for absorbing vibration energy of the building input by the earthquake. Some seismic isolation device systems have been already used practically. For example, several types using laminated rubber bearings are in practical use, such as 1) a combination system of laminated natural rubber bearings and hysteretic metal dampers separately provided from the rubber bearings, 2) a type of a laminated rubber bearings using a high damping rubber compound, and 3) a type of a laminated rubber bearing having a lead core, or the like. Further, 4) a sliding bearing type of seismic isolation device and 5) a rolling bearing type utilizing roller ad ball bearings of seismic isolation device are also in practical use.
Among the above seismic isolation devices, 3) so-called LRB (Lead Rubber Bearing), the laminated rubber bearing with lead core, which was invented and developed in New Zealand, has been highly evaluated in the world and applied to a lot of actual isolated structures (see Patent Documents 1 and 2). This device incorporates a lead core, which serves as a damper (an energy absorbing mechanism), at a center place or several places of the laminated rubber bearing as an isolator, in the plane view. This is one of the highly-evaluated seismic isolation devices in the world including Japan and other countries (including New Zealand, the United Stated, Italy, Taiwan, Turkey, China, and South America).
This seismic isolation devise is provided with both the isolator function and the damper function in one device. By changing a ration between the lead core having the damper function and the laminated rubber bearing having the isolator function, it becomes possible to rather freely control the seismic isolation performance i.e., a restoring force of the device.
However, a wave of a social recognition for an environmental problem in recent years causes a trend against a toxic potential of lead. Accordingly, it is suggested to employ a superplastic metal having a superior plastic deformation property like lead as a material of the core. Specifically, “a laminated rubber bearing having a tin core (lead plug) (Patent Document 3)” employing tin having a face-centered cubic lattice of crystalline structure same as lead, or tin-bismuth alloy, or a laminated rubber bearing employing zinc-aluminum alloy (Patent Document 4) are suggested.
Other than above, the following materials are suggested as core materials for absorbing energy; a polymer material such as a rubber having a high damping property, a mixed molding of two plastic resin materials each having different rigidities (Patent Documents 5 and 6); and an artificial damper material formed by molding a mixture of a polymer material such as a rubber and a granulated material such as iron powder or glass beads (Patent Document 7).
(Patent Document 1) Japanese patent application publication No. SH059-62742;
(Patent Document 2) Japanese patent No. 3024562;
(Patent Document 3) Japanese patent application publication No. 2008-082386;
(Patent Document 4 Japanese patent application publication No. 2007-139108;
(Patent Document 5) Japanese patent application publication No. 2005-009558;
(Patent Document 6) Japanese patent application publication No. 2007-092818; and
(Patent Document 7) Japanese patent application publication No. HEI9-177368.
A metal core incorporating type of seismic isolation device, for example, incorporating a lead-cored laminated rubber bearing called “LRB” or a tin-cored laminated rubber bearing called “SnRB”, and a seismic isolation device incorporating a core comprising artificially mixture of rubber and iron powder have the following configurations.
As shown in
By increasing the size of the core having a function for absorbing energy, the damping performance of the seismic isolation device can be enhanced. However, if a ration of the diameter (plane size) of the core to that of the laminated rubber bearing body becomes greater than a predetermined ratio, a horizontal deformation mode of the laminated rubber bearing body can be broken, or a stability of the laminated rubber bearing body and a vertical load support capacity will be unsure when the laminated rubber bearing body is deformed horizontally. Accordingly, normally, the diameter of the core is limited to about 20% or less of the diameter of the laminated rubber bearing body.
The damping performance can be also controlled by choice of the core material. Therefore, as described in the above Patent Documents, various materials are suggested as the damper (core) material incorporated in the laminated rubber bearing body. However, the resistance force of the core comprising the resin material or the granular material (in examples of Patent Documents 5 to 7) is low (the shear resistance force (stress level) per unit sectional area is low).
Hence, if the resin material or the granular material is employed in the seismic isolation devise for a large and heavy building, a core having extremely large diameter is required, this being not realistic, although. Therefore, the resin material or the granular material can be employed in only a house having a small size and a light weight such as a single-family house or the like.
Accordingly, considering the resistance force (stress level) of the material, metals are suitable to the damper (core) of the seismic isolation device for the large and heavy building, after all.
In Patent Document 3, alloy materials, such as tin-bismuth alloy, and tin-indium alloy are suggested as the core material. However, those materials are melted at extremely low melting points (between 117 and 138° C.), as shown in Table 1
The core of the seismic isolation devise absorbs the earthquake energy by plastically deforming along with the shift of the plurality of isolator layers with one another. Therefore, at the time of the earthquake, the core generates heat due to the absorbed energy. Numerous experiments shows that the temperature increase of the core easily exceeds 100° C. when a great earthquake vibration occurs.
Accordingly, when exposed to a great earthquake vibration, the above alloy materials having the low melting points have a high possibility to be molted. Further, even before the alloy materials are melted, the resistance force of the alloy materials has declined due to the high temperature. As the result, the energy absorbing performance of the alloy materials drops greatly. Hence, these alloy materials having the low melting point, although being plastically deformable metals, are unsuitable as core materials for absorbing the energy at the time of a great earthquake.
Lead, tin, aluminum, zinc, copper, and an alloy of them are drawing attention as metal materials having superior plastic deformation performances. Table 2 shows basic (mechanical) properties (longitudinal elastic modulus E, shear elastic modulus G, volume elastic modulus K, Poisson's ratio v, melting point, density at room temperature and at melting point or the like) of these representative superplastic metal materials.
As is well known, among the above metal materials, the most widely employed as the core of the seismic isolator device is pure lead having purity of 99.99% or more. Lead is a superplastic metal having a mechanical property capable of greatly plastically deforming. However, as lead has toxicity to human body, there is a tendency to hesitate to use lead material, amid the trend of rising environmental health awareness. Further, the resistance force of lead is slightly low as the damper material. Therefore, improvement is desired.
On the other hand, tin draws attention as a nontoxic superplastic metal instead of lead having toxicity. Tin-cored ruminated rubber is put into practical use and steadily achieves results. However, the resistance force of tin is about two times of lead. Therefore, the resistance force of tin is slightly high when tin core is incorporated in the laminated rubber bearing.
Further, the resistance force of tin is linked its rigidity. Therefore, the resistance force of tin becomes high along with its deformation unlike lead capable of deforming with a constant resistance force in its plastic deformation region. This means that tin is inferior to lead in the plastic deformability.
Table 3 shows a comparison between lead and tin in thermal properties and in mechanical properties. In terms of the thermal properties, tin has a fatal drawback. That is, the melting point of tin is lower than lead by around 100° C., while the resistance force (shear yield stress intensity) of tin is about two times higher than that of lead.
Now, it is assumed that a laminated rubber bearing (diameter: 1000 mmφ), incorporating a core (diameter: 200 mmφ, height: 400 mm), which is the most standard (general) type of laminated rubber bearing used in a building, horizontally deforms ±300 mm due to a great earthquake. In this assumption, the cycle number of vibration applied to the metal core is calculated, starting at 20° C., which is an assumed temperature of plug before the earthquake occurs, up until at the melting point of the metal core. As shown in the lower half of Table 3, the cycle number of lead core is around 18 cycles, while the cycle number of tin core is 7.6 cycles, i.e. tin core reaches its melting point at one-thirds of cycle number of lead.
This difference is caused by the difference of the resistance force between lead and tin. That is, since the resistance force of tin is about two times of lead, the amount of absorbing energy per a cycle (calorific value) also becomes about two times of lead. Further, this difference is caused by the difference of the melting point between lead and tin. That is, the melting point of tin is lower than lead by at most 100° C.
Note that since the resistance force of tin becomes lower along with temperature rise caused by the energy absorption, the actual cycle number at which the temperature of tin core reaches its melting point becomes somewhat greater than the above cycle number. Anyway, it is clear that the energy absorption performance of tin is sharply deteriorated at an early stage due to the lowered resistance force.
Especially, assuming the case of a great earthquake of magnitude 9 level, which is likely to occur at Nankai Trough nearer to the mainland than Great East Japan earthquake in 2011, the metal core is likely to be subject to repeated vibrations with amplitude larger than expected, over a long period of time. Hence, tin-cored ruminated rubber has serious problems against the above earthquake.
The above arguments and questions on the core for the seismic isolation device (laminated rubber bearing) are summarized below.
Since the resistance force of the core comprising the polymer material is low, the damper function is also low. Further, even if a larger sized core comprising the polymer material is used to raise the resistance force, the devise itself becomes unstable in turn. Therefore, the polymer material is unsuitable as the core material for the seismic isolation device.
Further, the alloy materials having the low melting points (Table 1) easily reaches the melting points when absorbing energy. Therefore, the alloy material is similarly unsuitable as the core material for the seismic isolation device.
After all, lead and tin, which have made a lot of achievements, are viable options as the core material for the seismic isolation device. However, as shown in tables 2 and 3, it can be seen that there is wide differences in the elastic modules and the shear yield intensity between lead that is most flexible material and tin that is the second flexible material. Specifically, tin has more than three times of elastic modules and about two times of shear yield intensity compared with lead, although the other materials have greater difference in the elastic modules and the shear yield intensity from lead and tin.
In short, lead is rather flexible as the core material for the seismic isolation device, although having an excellent deformation property. On the other hands, since tin is too rigid, tin is also inferior to lead in deformation property. Other materials such as aluminum, zinc, and copper are more rigid than tin. Furthermore, lead has a problem of toxicity.
As described above, the demand of the rigidity forces the use of the metal material as the core for the seismic isolation device. However, when the some conditions (i.e. rigidity, deformation property, mechanical properties, environmental health, and safety handling (non-toxicity)) are considered, an idealistic metal core material, meeting all of the above conditions, does not exist.
The present invention employs following configurations to solve the problem discussed above.
Configuration 1
A seismic isolation device includes: a laminated rubber bearing body formed by alternately laminating a plurality of elastic materials and a plurality of rigid materials in a vertical direction, each elastic material and each rigid material having a thin plate shape; and a composite metal core disposed inside the laminated rubber bearing body and plastically deformable to absorb energy. The composite metal core includes an inner metal and an outer metal. The outer metal concentrically surrounds the inner metal in a horizontal cross-sectional view. The inner metal and the outer metal are disposed in close adherence with each other. The outer metal has an elastic modulus and an yield rigidity greater than the inner metal so that a shear deformability of the composite metal core becomes greater than a bending deformability of the composite metal core.
A horizontal shear resistance force QC of the composite metal core in a predetermined cross-sectional area is set to satisfy an equation: QB≦QC<QA, the QA being a horizontal shear resistance force in the predetermined cross-sectional area of a metal core A comprising the single outer metal, the QB being a horizontal shear resistance force in the predetermined cross-sectional area of a metal core B comprising the single inner metal.
Configuration 2
In the seismic isolation devise according to configuration 1, any one of Combinations 1 to 4 (Combination 1: tin for the outer metal and lead for the inner metal, Combination 2: aluminum for the outer metal and lead or tin for the inner metal, Combination 3: zinc for the outer metal and any one of lead, tin and aluminum for the inner metal, Combination 4: copper for the outer metal and any one of lead, tin, aluminum and zinc for the inner metal) is employed as a combination of a material composing the outer metal and a material composing the inner metal.
Configuration 3
In the seismic isolation device according to configuration 1 or 2, the composite metal core has a rectangular shape or a slightly tapered rectangular shape in a vertical cross-section, and both the outer metal and the inner metal have one of a circular shape, an approximately quadrate shape, and an approximately polygonal shape having fewer angles then octagon in the horizontal cross-sectional. When the outer metal has a circular shape in the plane view, two or more longitudinal ribs extending in the vertical direction are formed on the outer peripheral surface of the outer metal. When the inner metal has a circular shape in the plane view, two or more longitudinal engaging members are formed on the inner peripheral surface of the outer metal and the outer peripheral surface of the inner metal to be engaged with each other.
Configuration 4
In the seismic isolation devise according to any one of configurations 1 to 3, the outer metal comprises tin or tin alloy and the inner metal comprises lead or lead alloy. Both the outer metal and the inner metal have one of a circular shape, an approximately quadrate shape, and an approximately polygonal shape having fewer angles then octagon in the horizontal cross-sectional view. A thickness t1 of the outer metal in the cross-sectional plane view is set to satisfy an equation t1/dp≦0.35, the dp being a size of the composite metal core in the horizontal cross-sectional view.
Configuration 5
In the seismic isolation devise according to any one of configurations 1 to 4, one or
two lid member, which is screw-cut, for fixing a core is incorporated at a plane center part of an upper end and/or a lower end of the composite metal core. The lid member comprises copper or copper alloy.
Configuration 6
In a manufacturing method of the composite metal core of the seismic isolation device according to any one of configurations 1 to 5, when the outer metal has a melting point higher than the inner metal, the composite metal core is manufactured by injecting the inner metal, which is in a molten state at a temperature lower than the melting point of the outer metal, into a hollow formed by an inner surface of the outer metal formed in a prescribed size and shape, or when the outer metal has a melting point lower than the inner metal, the composite metal is manufactured by injecting the outer metal, which is in a molten state at a temperature lower than the melting point of the inner metal, into a hollow formed between a metal mold having an internal shape equal to an outer surface of the outer metal, and the internal metal which is formed in advance and disposed inside the hollow.
Configuration 7
In the manufacturing method according to any one of configurations 1 to 5, the composite metal core is manufactured as a metallic skin by immersing the inner metal, which is formed in a prescribed size and shape in advance, into a container in which the outer metal is in a molten state, or the composite metal core is manufactured as a thin film by thermal-splaying the outer metal, which is in a molten state, on at least a side surface of the inner metal, which is formed in a prescribed size and shape in advance.
Effect 1
In the present invention, the horizontal shear resistance force can be set arbitrary. Specifically, since the metal core incorporated in the laminated rubber bearing body is a hybrid core comprising two different kinds of metal materials, the horizontal shear resistance force can be set arbitrary between the shear resistance force when the metal core is formed of one metal and the shear resistance force when the metal core is formed of the other metal.
More specifically, the horizontal shear resistance force QC of a composite metal core C in a predetermined cross-sectional area can be arbitrarily set to satisfy the following equation: QB≦QC<QA. The QA is a horizontal shear resistance force in the predetermined cross-sectional area of a metal core A comprising the single outer metal. The QB is a horizontal shear resistance force in the predetermined cross-sectional area of a metal core B comprising the single inner metal.
Note that the QC is approximately equal to the QB (QC≈QB) when the outer metal core A is formed as a metallic skin or a thin film made by thermal-splaying as described in the composition 7.
Effect 2
In the present invention, the rigidity (horizontal shear resistance force per unit area) of the metal core can be also set freely, likewise the above first effect.
The average shear yield stress degree τ3 of the composite metal core per unit area is indicated with an equation τ3=τ1×RA1+τ2 (1−RA1). The τ1 indicates the shear yield stress degree of the outer metal. The τ2 indicates the shear yield stress degree of the inner metal. The RA1 (=A1/A0) indicates the ration of the cross-sectional area of the outer metal A1 to the total cross-sectional area A0 of the composite metal core.
With this configuration, the horizontal shear yield stress degree τ3 can be arbitrary set to satisfy an equation τ2≦τ3<τ1, by changing the area ratio RA1.
Effect 3
A contribution of very small cross-sectional areas to a cross-sectional secondary moment I, which decides a bending rigidity of a metal core, is proportional to the square of the distance between a center of core and each very small cross-sectional area. Therefore, the very small cross-sectional area far from the center contributes the cross-sectional secondary moment I more than the very small cross-sectional area near the center.
Therefore, a relationship between an increase rate CEI (=EI3/EI2) (EI3: a bending rigidity of a composite metal core, where a material employed in the outer metal has a higher elastic modulus than a material employed in the inner metal, EI2: a bending rigidity of a metal core formed of the single inner metal core) and CGA (=GA3/GA2) (GA3: a shear rigidity of a composite metal core, where a material employed in the outer metal has a higher elastic modulus than a material employed in the inner metal, GA2: a shear rigidity of a metal core formed of the single inner metal core) is indicated CEI>CGA, generally.
Accordingly, a composite metal core of the present invention has a higher increase rate in the bending rigidity than the shear rigidity, and then a bending deformation is less likely to occur, when the composite metal core is subject to a horizontal force. In short, since the bending deformation is hard to occur, the composite metal core of the present invention becomes a shear deformation superior mode. This secures a stable shear deformability of the metal core, and the metal core becomes to show a stable energy absorbing property.
Effect 4
In the present invention, since the composite metal core employs lead for the inner metal and employs the other material such as tin instead of lead for the outer metal, the inner metal comprising lead having toxicity to human body is covered by nontoxic outer metal. This helps to improve the safety handling in manufacturing process, and to make operators' working environment safe and healthy.
In the present invention, when the outer metal is formed as thin film by thermal spraying or plating on the inner metal, the mechanic properties of the composite metal core becomes almost the same as the mechanic properties of the inner metal (i.e. lead). Then, the composite metal core of nontoxic in handling, while having almost the same mechanical properties as the inner metal, is materialized.
Effect 5
In the present invention, the weakness of the laminated rubber bearing body incorporating tin is overcome.
A seismic isolation devices including a laminated rubber bearing body incorporating tin is successfully employed recently as a seismic isolation device incorporating a metal core other than lead metal core. However, the device has a weakness in thermal properties as pointed out herein above.
However, in the present invention having the outer metal comprising tin and the inner metal comprising lead, the heat generated in tin part can be transferred to lead part having a large heat capacity and generating a low heat. This avoids the temperature rise in the tin part and increases the heat capacity of the whole the composite metal core. Lead having a high melting point compensates the thermal deterioration of tin. In this way, compared to the laminated rubber bearing body incorporating single tin, the vulnerability to generated heat of the whole device is improved greatly. As the result, the weakness of thermal properties of the tin metal core is overcome.
Effect 6
In the present invention, when the composite metal core has a circular plane shape, two or more longitudinal ribs are formed on the outer peripheral surface of the composite metal core (outer metal), and two or more engaging members are formed on the inner peripheral surface of the outer metal and the outer peripheral surface of the inner metal to be engaged with each other. However, no longitudinal rib and engaging member are required when the composite metal core has a polygonal shape such as a quadrate shape.
As a result, when the seismic isolation device is forcibly subject to deformation in two directions horizontally at a time, and especially when the seismic isolation device is forcibly subject to rotational excitation so that the top surface is twisted against the bottom surface, the metal core cannot rotate around a vertical axis inside the laminated rubber bearing. Therefore, the device shows stable energy absorption performance in a process of plastic deformation against any excitation mode including circular excitation.
Further, when a composite metal core has a quadrate plane shape (side length D), the cross-sectional area becomes 1.27 times (=4/π) larger than a conventional metal core having a circular plane shape (diameter d) in a condition of (D=d). Therefore, the damping performance (energy absorption performance) of the device is also improved.
Further, the present invention has an economic effect. One of the problems of tin core is a cost. Since tin is extremely expensive, the price of tin core becomes also extremely expensive. However, the composite metal core of the present invention employs lead for the inner metal and tin for the outer metal, and further the thickness of tin of outer metal can be controlled appropriately. By this way, material cost can be reduced to an appropriate level, while overcoming the problems of toxicity and improving the rigidity.
Embodiments of the present invention are explained based on the drawings. The same number will be used to indicate the same part in the respective embodiments.
A seismic isolation device according to the first embodiment is a damper built-in type of laminated rubber bearing seismic isolation device. The seismic isolation devise includes a laminated rubber bearing body 1 and at least one plastic metal core 30. The laminated rubber bearing body 1 is formed by alternately laminating a plurality of elastic layers (elastic materials) 11 and a plurality of inner steel plates (rigid materials) 2 in the vertical direction, each elastic layer 11 and each inner steel plate 2 having a thin plate shape. The plastic metal core 30 is plastically deformable to absorb energy and is disposed inside the laminated rubber bearing body 1. Thus, the plastic metal core 30 serves as a damper mechanism.
The plastic metal core 30 includes two kinds of metals (an inner metal 32 and an outer metal 31) having different plastic deformability in yield rigidity and elastic modulus with each other. These metals are arranged in concentric in a horizontal cross-sectional view. In other words, the outer metal 31 concentrically surrounds the inner metal 32 in the horizontal cross-sectional view.
The outer metal 31 and the inner metal 32 are disposed in close adherence with each other and integrated. The integrated outer metal 31 and inner metal 32 forms a composite metal core 30. The outer metal 31 has an elastic modulus and an yield intensity greater than the inner metal 32. The composite metal core 30 has an approximately square shape in the plane view, as shown in the
By composing the outer metal 31 of the material with the vertical elastic modulus and the yield intensity greater than the inner metal 32, it becomes possible to greatly raise an increase rate of a bending rigidity of the composite metal core 30 rather than an increase rate of a shear rigidity of the composite metal core 30 (see
Thick steel plates 25 are disposed near the upper and lower ends of the composite metal core 30. Flanged steel plates 4 are disposed outside of the thick steel plates 25 in the upper-lower direction.
Any one of Combinations 1 to 4 (Combination 1: tin for the outer metal 31 and lead for the inner metal 32, Combination 2: aluminum for the outer metal 31 and lead or tin for the inner metal 32, Combination 3: zinc for the outer metal 31 and any one of lead, tin and aluminum for the inner metal 32, Combination 4: copper for the outer metal 31 and any one of lead, tin, aluminum and zinc for the inner metal 32) are employed as a combination of a material composing the outer metal 31 and a material composing the inner metal 32.
Combination 1, (i.e. tin for the outer metal 31 and lead for the inner metal 32) is a representative example, although any combination of the above can be employed. Note that each material described above can include alloy of them.
With this construction, a horizontal shear resistance force QC of a composite metal core C in a predetermined cross-sectional area can be arbitrarily set to satisfy an equation: QB≦QC<QA, the QA being a horizontal shear resistance force in the predetermined cross-sectional area of a metal core A comprising the single outer metal 31, the QB being a horizontal shear resistance force in the predetermined cross-sectional area of a metal core B comprising the single inner metal 32.
The composite metal core 30 has a rectangular shape or a slightly tapered rectangular shape in the vertical cross-section. Both the outer metal 31 and the inner metal 32 have one of a circular shape, an approximately quadrate shape, or an approximately regular polygonal shape having angles fewer than or equal to octagon in the horizontal cross-section (in the plane view).
As shown in
Further, as shown in
The pair of lid member 36 has a “protrusion preventing function” for preventing the materials composing the composite metal core 30 from protruding upward and downward due to an earthquake vibration.
Further, the pair of lid member 36 has a “deformation correcting function.” When the pair of lid member 36 comprises copper or copper alloy, it becomes possible to apply current to the composite metal core 30 thorough the pair of lid member 36. By applying current to the composite metal core 30, it is possible to raise the temperature of the composite metal core 30. When the temperature of the composite metal core 30 is raised, the composite metal core 30 becomes soft. Therefore, even if the composite metal core 30 is deformed by the earthquake, the deformation of the composite metal core 30 can be easily corrected by applying current.
Furthermore, the pair of lid member 36 has a “metal structure regenerating function.” By heating and thereafter cooling the composite metal core 30, it becomes possible to eliminate the plastic distortion of the composite metal core 30, and then restore the structure of the composite metal core 30 (prompt the composite metal core 30 to be re-crystallized).
When the composite metal core 30 has a quadrate or polygonal plane shape, the peripheral side surface of the composite metal core 30 (outer metal 31) is engaged with the inner steel plates 2, the thick steel plates 2, and the flanged steel plates 4 (depending on the shape). Therefore, in such case, the longitudinal ribs 33 are unnecessary, since the rotational shift around a vertical axis does not occur in the composite metal core 30. Further, in such case, the outer metal 31 and the inner metal 32 are also engaged with one another. Therefore, in such case, the four longitudinal engaging members 34 are also unnecessary, since the rotational shift around the vertical axis does not occur.
In
As shown in
In the configuration 6, a method for manufacturing the composite metal core 30 by utilizing the difference in the melting point between the outer metal 31 and the inner metal 32 is described.
When the outer metal 31 has a melting point higher than the inner metal 32, the composite metal core 30 is manufactured by injecting the inner metal 32, which is in a molten state at a temperature lower than the melting point of the outer metal 31, into a hollow formed by the inner surface of the outer metal 31 formed in a prescribed size and shape.
On the other hand, when the outer metal 31 has a melting point lower than the inner metal 32, the composite metal 30 is manufactured by injecting the outer metal 31, which is in a molten state at a temperature lower than the melting point of the inner metal 32, into a hollow formed between a metal mold having an internal shape equal to the outer surface of the outer metal 31, and the internal metal 32 which is formed in advance and disposed inside the hollow.
In this embodiment, the composite metal core 30 is manufactured as a metallic skin by immersing the inner metal 32, which is formed in prescribed size and shape in advance, into a container in which the outer metal 31 is in a molten state. Further, the composite metal core 30 is also manufactured as a thin film by thermal-splaying the outer metal 31, which is in a molten state, on at least the side surface of the inner metal 32, which is formed in prescribed size and shape in advance.
As the outer metal 31 is formed as the metallic skin or the thin film with the above manufacturing methods, the outer metal 31 is illustrated as an outline 311 in the figure, and the plan area is mainly accounted for the inner metal 32.
With this construction, by covering/coating the inner metal 32 comprising lead with tin, aluminum or other non-toxic metal composing the outer metal 31 (311), an environment/health-friendly seismic isolation device, while having the mechanical property of lead, is materialized. Through this embodiment, the problem of toxicity of the lead-cored laminated rubber bearing is overcome. In this embodiment, since the outer metal 31 is formed as the thin film, the resistance force QA of the outer metal 31 becomes very low, and the resistance force QC of the composite metal core C becomes closer to the resistance force QB of the inner metal B (QC≈QB).
In
As shown in
As is shown in the
Note that this graph can be also applied when the composite metal core 30 has either one of a circle or quadrate plane shape, and further when the composite metal core 30 has a polygonal plane shape, as long as the outer metal 31 and the inner metal 32 are concentric and the thickness t1 of the outer metal 31 is even.
The plug diameter dp is set in the range of 100 mm to 300 mm. Among several curves in
The side length dp is set in the range between 100 mm to 300 mm. Among several curves, the bottom curve represents the horizontal shear resistance force Qd when the whole composite metal core 30 comprises single lead (the inner metal 32), and the top curve represents the horizontal shear resistance force Qd when the whole composite metal core 30 comprises single tin (the outer metal 31). Same as
Further, by employing the quadrate shape instead of the circle shape, the horizontal shear resistance force Qd can be more efficiently increased.
Among several straight lines, the bottom straight line (A1/A0=0), which is set to a reference value (=1), represents the rising rate EI/EIpb when the whole composite metal core 30 comprises single lead, and the top straight line (A1/A0=1) represents the rising rate EI/EIpb when the whole composite metal core 30 comprises single tin. The rising rate EI/EIpb of the bending rigidity EI corresponds to the ratio of the longitudinal elastic modulus of tin and lead. The rising rate EI/EIpb of the shear rigidity GA corresponds to the ratio of the shear elasticity modulus of tin and lead. The middle lines shows the ratio A1/A0 of the area A1 of the outer metal 31 (tin) to the whole cross-sectional area A0 of the composite metal core 30.
It is clear that the rising rate EI/EIpb of the bending rigidity EL is higher than the rising rate GA/GAbp of the shear rigidity GA when compared in the same area ratio A1/A0. This is one of the important points of the present invention.
As shown in
Accordingly, by setting the thickness t1 of the outer metal 31 in the range of t1/dp=0 to 0.35 when the outer metal 31 comprises tin and the inner metal 32 comprises lead, the shear deformation tends to occur more than the rigidity deformation in the composite metal core 30 of the present invention. Therefore, a stable energy absorption performance is expected.
This graph is also applied when the composite metal core 30 has either circular plane shape or quadrate plane shape, and when the composite metal core 30 has a polygonal plane shape as long as the outer metal 31 and the inner metal 32 are concentric, the thickness of the outer metal 31 is even, and the plane shape of the outer metal 31 is symmetric to the central axis (a neutral axis) of the outer metal 31 in the cross-section.
Considering the
If the composite metal core 30 comprising single tin is repeatedly largely deformed by a large earthquake, the horizontal shear resistance force Qd is drastically declined. As the result, in a possible worst case, the composite metal core 30 may be melted due to a temperature rise caused the repeated large deformations.
However, in the shear deformation superior mode described above, a large heat capacity is secured in the whole composite metal core 30 due to lead composing the inner metal 32 (lead account for 90 to 81% of the plane area of the composite metal core 30). Therefore, heat generated at the outer metal 31 comprising tin is promptly transmitted to the inner metal 32 comprising lead, thereby inhibiting the temperature rise in the whole composite metal core 30. Thus, in the composite metal core 30 of the present invention, the risk of the decline of the horizontal shear resistance force Qd or the risk of melting itself, caused by the temperature rise, is drastically improved and overcome.
If, after this movement, the top surface 38 of the laminated rubber bearing body 1 is shifted in a direction 6 (shown in
However, in the present invention, the composite metal core 30 is designed to have a polygonal (quadrate or the like) plane shape. Otherwise, when the composite metal core 30 is designed to have a circular plane shape, two or more longitudinal ribs 33 are formed on the outer peripheral surface of the composite metal core 30 (outer metal 31) as shown in
In this way, even when the seismic isolation device is forced to deform in horizontal two directions at a time, especially when the seismic isolation device receives an excitation for the top surface 38 to horizontally rotate in the direction of arrow 7 against the position of the bottom surface 37, the composite metal core 30 is prevented from rotating around the own vertical axis inside the laminated rubber bearing body 1. Thus, the composite metal core 30 attains an excellent performance for absorbing energy by the plastic deformation, even when the composite metal core 30 is subject to any excitation including circular excitation.
As described above, in the laminated rubber bearing body 1 of the present invention, it becomes possible to control the horizontal shear resistance force Qd of the composite metal core 30 at an appropriately level, although it is not possible when a conventional metal core comprises a single metal. Therefore, a stable energy absorption performance is provided. As the result, a performance and reliability of a conventional type of damper built-in laminated rubber bearing body is greatly improved.
Since the Great East Japan Earthquake (M9.0), which hit Japan in 2011, a catastrophic earthquake of the level of M 9.0 has been recognized as a realistic one to occur. Therefore, the effect of the seismic isolation devise of the present invention is expected to play an effective role, assuming that a long-period and continuous severe earthquake vibration, or a severe input earthquake vibration in horizontal two directions occurs.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-122757 | Jun 2014 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14727025 | Jun 2015 | US |
| Child | 15271969 | US |
