JPH0784814B2 - Seismic isolation rubber - Google Patents

Description

The present invention relates to a seismic isolation rubber in which a plurality of hard plates and soft plates having viscoelastic properties are alternately laminated,
In particular, the present invention relates to a seismic isolation rubber having excellent earthquake resistance and durability that can be stably fixed to both a building and a foundation by reducing a local strain generated near the flange.

[Conventional technology]

A structure (seismic isolation rubber) in which a hard plate such as a copper plate and a soft plate having a viscoelastic property such as rubber are laminated has recently attracted attention as a bearing member that satisfies the required vibration isolation and vibration absorption properties during an earthquake. I'm flying

This type of seismic isolation rubber inserts a seismic isolation rubber that is laterally soft, that is, has a low shear rigidity, between a rigid building such as concrete and the foundation, so that the natural period of a concrete building is Has the effect of shifting from the cycle,
Due to this action, the acceleration that the building receives due to the earthquake becomes extremely small.

In this way, the seismic isolation rubber used for the support member is inserted between the building and the base and functions to support the entire building, so it is difficult to replace it once it is installed, and
Even if it is technically replaceable, the cost is considerably high. For this reason, seismic isolation structures are required to have a durable life of 50 to 60 years, which is similar to that of concrete structures.

As shown in FIG. 2 (a), the seismic isolation rubber 10 usually includes upper and lower surfaces of a laminated structure 1 of soft plates R ₁ , R ₂ , R ₃ and hard plates S ₁ , S ₂ , S ₃ , That is, thick steel plates 4 and 5 called flanges are firmly adhered to a portion in contact with the building 2 and the foundation 3.

Such a seismic isolation rubber 10 is characterized by returning to its original position (elastic deformation) again after deformation due to an earthquake. Therefore, during a large earthquake, as shown in FIG. 2 (b), As the building shakes, the base isolation rubber 10 undergoes large shear deformation, and the soft plates R _{1 to} R ₃ sandwiched between the hard plates S _{1 to} S ₃ undergo large tensile deformation of several hundred percent. Especially, among soft plates, the part X near the surface layer of the soft plate R ₁ near the flange
Then, since the hard plate S ₁ bends in the direction of the arrow due to the shear deformation, an extremely large local strain occurs, and the seismic isolation structure is damaged.
It has been conventionally considered that it causes breakage.

In other words, to date, details of what kind of local stress and strain occur inside the seismic isolation rubber when a large shear deformation is applied to the seismic isolation rubber that supports the weight of the building for a long time during an earthquake Has not been parsed into
Conventionally, it has been speculated that the maximum local strain may occur in the X part, as described above, based on the approximate shape of the seismic isolation rubber actually deformed.

Therefore, in England and New Zealand, in order to prevent the seismic isolation rubber from being damaged by the maximum local strain near this flange, the recesses 8a, 8b are formed in the mounting flanges 8, 9 of the seismic isolation rubber 10 as shown in FIG. 3 (a). , 9a, 9b are provided, and the recesses 8a, 8b,
Holts 2a, 2b, 3 installed in 9a, 9b and building 2 and foundation 3
Seismic isolation rubber 10 is attached by fitting a and 3b. (This method is called "Dowel method.") By doing so, the flanges 8 and 9 bend in the direction of the arrow when the earthquake occurs, as shown in FIG. It was thought that a large local strain would be prevented from occurring in the ground, and damage and breakage of the seismic isolation rubber 10 would be prevented.

[Problems to be solved by the invention]

As is well known, when a flexible structure such as seismic isolation rubber is placed under a rigid building such as concrete, if it receives horizontal and vertical shaking from an earthquake, vertical and rotational movements will occur in addition to simple horizontal movement. Occurs, and the rocking phenomenon of the building easily occurs.

From such a point of view, it is desirable that the seismic isolation rubber used in an environment where the earthquake is severely shaken has a stable structure that is completely and firmly fixed to the base and the foundation via the flange.

However, in the conventional technique shown in FIGS. 3 (a) and 3 (b), the flanges 8 and 9 are not fixed to the foundation 3 or the building 2 and are bent according to shear deformation. The building becomes very unstable and may rock due to heavy rocking. That is, in the case of England and New Zealand, reduction of local strain near the flange was emphasized rather than stability of the building.

Therefore, conventionally, even if the seismic isolation rubber is extremely fixed and installed on the building and the foundation via the flange, the occurrence of local stress and local strain is extremely small. The appearance of "fixed seismic isolation rubber" was strongly desired.

[Means for solving problems]

INDUSTRIAL APPLICABILITY The present invention solves the above conventional problems and can be stably fixed and installed on a building and a base. In this state, the occurrence of local strain is reduced, and damage and damage due to local strain are significantly An improved seismic isolation rubber, which is reduced to, is provided on the upper and lower surfaces of a laminated structure in which a plurality of hard plates having rigidity and soft plates having viscoelastic properties are alternately laminated. A seismic isolation rubber provided with a flange, which is a seismic isolation rubber provided with means for averaging the local strain of the entire structure by reducing the local strain in the vicinity of the flange. The seismic isolation rubber is characterized in that a portion in contact with the flange has a curved surface whose inner surface is curved inward in an arcuate shape or a shape similar to an arcuate longitudinal section so that the cross-sectional area gradually increases toward the flange. To Than it is.

The inventors of the present invention, when studying a base fixed type seismic isolation rubber that does not cause problems such as damage and damage due to local strain, firstly compressive deformation due to the seismic isolation rubber supporting a building and an earthquake. Considering that it is important to analyze which part of the seismic isolation rubber and what size local strain occurs when it is subjected to shear deformation due to horizontal shaking during We started to analyze the stress.

In order for the seismic isolation rubber to support the building for a long period of time and to be a structure that is sufficiently safe against shaking due to a large earthquake, theoretical and quantitative design is indispensable, not empirical design based on conventional intuition. I can't wait.

By the way, it is general to use FEM (Finite Element Method) analysis by computer to perform stress analysis of materials, but when performing this FEM analysis, the stress-strain relationship of materials is displayed by linear approximation. In addition, in the analysis for small deformation, the calculated value and the actual measurement result match, but at the present time, the agreement between the calculated value and the actual measurement value is very poor at large deformation.

Therefore, in the research in the present invention, a method of displaying the nonlinearity of the rubber material as faithfully as possible for a structure that undergoes an extremely large deformation such as a base isolation rubber was used, and as a result, a compressive strain of 8.5% and a shear strain of 100 were obtained. At the time of% deformation, as shown in FIG. 4, it was possible to obtain an analysis result in which the deformed states by actual measurement (broken line) and calculation (solid line) were sufficiently coincident.

And thus, in this way, a quantitatively reliable FEM
After confirming that the analysis results can be obtained, first, as shown in FIG. 5, five layers of rubber (R ₁₁ , R ₁₂ , R ₁₃ , R
₁₂ , R ₁₁ ), 4 layers of steel plates (S ₁₁ , S ₁₂ , S ₁₂ , S ₁₁ ) and flanges 4 and 5 on the base isolation rubber, compressive strain 6%, shear strain 100
The deformation state and the principal strain of each part were examined when%. As a result, A to E in the deformed state (schematic diagram) as shown in FIG.
At each point, the strain value as shown in Comparative Example 1 in Table 1 below was analyzed. That is, A point = B point = 138%, C point = D point = 5
1%, E point = 80%. From this result, it was confirmed that a larger strain appeared in R ₁₁ near the flange than in the center R ₁₃ .

As described above, many people have empirically believed that a large local strain appears on the tensile side (that is, A in FIG. 6) near the flange due to the shear deformation of the seismic isolation rubber. Is. However, what is more important in the above-mentioned analysis by the present inventors is that not only the tensile side A but also the compressive side B of the rubber R ₁₁ near the flange show a large local strain equal to or larger than A. .

As a result of further studies, when compressive deformation and shear deformation were applied to the base isolation rubber, large local strains were generated on the tensile side A and the compressive side B near the flange. Since it extends to not only the adjacent rubber layer R ₁₁ but also the rubber layer of R ₁₂ (if the number of rubber layers is very large, it further affects the rubber layer on the center side). In order to enable the development of a base-fixation type base isolation rubber in which damage and breakage due to local strain have been greatly reduced, which is the main purpose of the invention, it is essential to reduce the local strain particularly unevenly distributed near this flange. That is, the present invention has been completed.

The results of this analysis provided extremely important findings in the research relating to the present invention. That is, as shown in FIGS. 3 (a) and 3 (b), in the case of the dowel system in which the flange on the tension side is bent, which is used in the United Kingdom and New Zealand, the local strain of the A portion is surely reduced, but , Such a structure results in further increasing the local distortion of the B section,
As a whole, it causes the breakage from the portion B near the flange. Therefore, it can be said that the dowel method does not reduce the local strain near the flange to increase the safety factor against breakage, but only introduces the risk of locking.

The present invention was made possible and successful for the first time in the world,
It is based on such analysis results.

[Action]

 The seismic isolation rubber of the present invention has the following features.

Large local strains such as maximum local strain are not concentrated near the flange, and are widely and evenly distributed over the entire seismic isolation rubber.

The maximum local strain generated in the seismic isolation rubber is greatly reduced.

From this, damage to the seismic isolation structure due to local strain,
Problems such as damage are eliminated.

Furthermore, when a special rubber is used for the surface portion of the laminated structure of the seismic isolation rubber, the durability and safety of the seismic isolation rubber can be further improved.

〔Example〕

 Embodiments will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view of a base isolation rubber 20 according to an embodiment of the present invention. This seismic isolation rubber 20 includes flanges 4, 5 on the upper and lower surfaces of a laminated structure 13 in which a soft plate 11 such as a rubber having a viscoelastic property and a hard plate 12 having a rigidity such as a steel plate are alternately laminated.
Is provided.

In the seismic isolation rubber 20 of this embodiment, the outer surface of the laminated structure 13 in contact with the flanges 4 and 5 has an arcuate vertical cross section so that the cross-sectional area gradually increases toward the flanges. Or, it is a curved surface that is curved like an arc.

If the radius of the arc of the arcuate longitudinal section of the curved surface formed in the portion contacting the flanges 4 and 5 of the laminated structure 13 is too small, the local strain reducing effect due to the provision of the curved surface is low, and conversely it is large. If it is too much, it will be very difficult to manufacture seismic isolation rubber.

Therefore, the arcuate shape of this curved surface has a radius L with respect to the thickness k of the soft plate 11 and the thickness h of the hard plate 12 as shown in FIG. ,Preferably More preferably Above all Is desirable.

In the present embodiment, the arcuate shape or the arcuately similar shape of the curved surface means, in addition to the arcuate shape as shown in FIG. 7, a shape similar to this and having an effect of reducing local stress. Well, for example, as shown in FIGS. 8 (a) and 8 (b), 1
Alternatively, a shape such as a combination of a plurality of straight lines and a combination of a straight line and an arc as shown in FIG.

By the way, in a supporting member that is a laminated body of a hard plate such as a steel plate and a soft plate such as rubber, excessive stress and strain occur in the portion of the soft plate that is in contact with the edge portion of the hard plate, and in this portion, It is a well-known fact that damage is likely to occur.

Therefore, conventionally, in order to reduce the local stress of the soft plate that comes into contact with the edge portion of such a hard plate, as shown in FIG. A rubber support piece having a concavely curved concave portion is known (Jitsuko Sho 58-30818).

However, in a base isolation rubber having a structure in which a large number of hard plates and soft plates are pasted together, providing a concave curved surface on each soft plate deteriorates the releasability from the mold and increases the cost of the mold. I have a problem. Especially when the thickness of the soft plate is small, such a problem becomes more serious.

Further, in the above-mentioned conventional laminated structure, since the end face of the hard plate such as a steel plate is exposed to the outside, there is a problem that corrosion easily progresses from this end face portion. In addition, in order to prevent such corrosion, it is possible to coat the peripheral surface of the metal plate exposed to the outside with anti-vibration rubber etc., but in the case of seismic isolation rubber, the period of use is extremely long. Considering that (for example, in the case of a concrete structure, durability of about 60 years must be satisfied), it is difficult to guarantee durability for a long period of time by such a coating method.

In order to solve such a problem, in the embodiment shown in FIG. 1, the side end surface of the hard plate 12 is made to have an arcuate cross section or an arc-like shape which bulges outward, and the hard plate The hard rubber 11
Was embedded in the outer skin layer.

In this case, the radius of the arc of the arcuate cross section of the bulging portion formed on the side end surface of the hard plate 12 is the value of r shown in FIG. 7, preferably 0.1 mm ≦ r, more preferably 0.3 mm ≦ r It is desirable that 0.5 mm ≦ r.

The arcuate shape or arcuately similar shape of the bulging portion means, in addition to the above-mentioned arcuate shape, an arcuate function for reducing local stress, for example, as shown in FIGS. 10 (a) and (b), One consisting of a plurality of straight cutting surfaces, or one consisting of a combination of straight cutting surfaces and arcs, as shown in FIG. 10 (c),
Includes various arc-like shapes.

As in the present embodiment, by making the edge portion of the hard plate 12 smooth by combining a curved line or a straight line, the stress or strain generated in the soft plate 11 portion in contact with the edge portion is significantly reduced. It becomes possible.

By the way, since the seismic isolation rubber is constantly exposed to the outside air during use, it is subject to long-term deterioration due to oxygen, humidity, ozone, ultraviolet rays, radiation for nuclear power, and sea breeze at the seaside. Further, since it supports the building, it is constantly subjected to a compressive load, and even under normal conditions, a considerable tensile stress is applied to the surface portion of the rubber layer. Especially when the creep amount becomes large due to long-term use, even if the compressive strain is several% to 10%.
However, the tensile strain at the surface portion reaches 100 to 300%. Moreover, in the event of a major earthquake,
Since the shear strain of 0 to 200% is applied, this strain is compounded and the surface portion of the base isolation rubber is also subjected to a very large strain. Deterioration of the surface rubber of the seismic isolation rubber due to the outside air further progresses as the tensile stress and tensile strain increase.

From the above, it is important for the surface rubber of the seismic isolation rubber to: a) make the tensile strain as small as possible; and b) use a rubber with excellent weather resistance.

Therefore, the present inventors have conducted the following study on the tensile strain and weather resistance of the surface portion of the seismic isolation rubber based on the structure of the conventional seismic isolation rubber.

The seismic isolation rubbers currently proposed include the following.

As shown in FIG. 11, a rubber layer 21 and a metal plate 22 are laminated, and an edge portion 22a of the metal plate 22 is exposed on the surface or covered with a thin (about 0.5 to 1 mm) rubber layer.

As shown in FIG. 12, a rubber layer 21 and a metal plate 22 are laminated, and an edge portion 22a of the metal plate 22 is covered with a thick surface rubber 23.

The rubber materials used for these seismic isolation structures are roughly classified into natural rubber type in England and New Zealand and chloroprene rubber type in France.

That is, in France, chloroprene rubber is used as a result of emphasis on weather resistance, while in England and New Zealand, natural rubber is used with emphasis on the fracture resistance of rubber. In the United Kingdom, in order to compensate for the poor weather resistance (heat aging resistance, ozone resistance, oxidation deterioration resistance, etc.) of natural rubber, a method of forming a thick surface rubber layer is adopted as shown in Fig. 12. ing. (For example, in the case of a British seismic isolation rubber used in a court built in the suburbs of Los Angeles, the surface rubber layer thickness is 75 mm.) The present inventors first isolated seismic isolation during static load and during an earthquake. In order to reduce the tensile strain generated on the outer surface of the rubber, the outer surface rubber 23 that covers the outside of the laminated structure of FIG. The part up to (the part of thick layer T in FIG. 12) is referred to as “outer skin layer”.

Then, the local strain generated on the outer surface of the outer skin layer exposed to the outside air gradually decreases as the outer skin layer thickness T increases, but when it reaches a certain thickness, the local strain is reduced even if the thickness is further increased. It was recognized that the effect of the action was extremely poor. On the other hand, as the thickness of the outer skin layer increases, not only the material cost increases, but also in order to significantly delay vulcanization,
The overall cost is considerably high.

For this reason, the thickness T of the outer skin layer is preferably 1 to 30 mm, preferably 2 to 20 mm, and more preferably 3 to 15 mm. However, when the seismic isolation rubber is required to have other properties such as fire resistance, the outer skin layer may have a thickness of more than 30 mm.

On the other hand, as described above, the seismic isolation rubber is always used in a state where it is exposed to the outside air, so that the outer surface of the seismic isolation rubber needs to be swollen and protected with rubber having excellent weather resistance.

On the other hand, of the conventional seismic isolation rubbers, when chloroprene rubber with good weather resistance is used as the rubber material, chloroprene rubber has large hysteresis loss, which results in large creep and poor cold resistance and low temperature crystallinity. Since the hardness of the rubber increases at low temperatures,
The seismic isolation rubber using chloroprene rubber has the drawbacks that the original seismic isolation performance cannot be exhibited, and the use of expensive chloroprene rubber significantly increases the product cost.

On the other hand, as is well known, natural rubber has poor weather resistance. In the case of deteriorated natural rubber, not only visible changes such as ozone cracks occur, but also the elastic modulus significantly increases, and the breaking strength and the elongation at break greatly decrease. That is, due to long-term deterioration in the atmosphere, natural rubber has numerous ozone cracks on its surface and is transformed into a brittle material.

Therefore, even when the structure shown in Fig. 12 is used, the rubber layer on the surface deteriorates, and if it is covered with such a deteriorated layer, even if the internal rubber layer is not deteriorated, it will be repeated due to the earthquake. When subjected to a large deformation or the like, first, the deteriorated layer on the surface is easily broken, and further, there is a possibility that it may cause the entire rubber layer inside to be broken. (For example, when a rubber B having a poor heat-deteriorating property is thinly applied to the surface of a rubber A having an excellent heat-degrading property and thermally deteriorated, a heat-deteriorating layer of the rubber B formed on the surface of the A-rubber causes A rubber may be easily broken just by bending it.) Also, if water enters through cracks such as ozone cracks that have occurred in the surface rubber layer of the seismic isolation rubber, rust will occur on the metal of the hard plate, and As a result, there is a risk that the metal plate and the rubber layer will be separated.

As mentioned above, the seismic isolation rubber is required to have durability over a long period of about 60 years, and if any deteriorated part occurs, it will rupture and cause the seismic isolation rubber to rupture. It may not be connected, it may not be subjected to any unexpected deformation at the time of an earthquake, and it is not possible to neglect some deterioration because of this, and because the seismic isolation rubber supports the building and human life, Considering that safety should always be perfect, it is desired that the seismic isolation rubber has extremely little deterioration in the environment of its use. Moreover, it is always required to keep the product cost low, which is required for every factory production.

Therefore, in the case of a seismic isolation rubber made of rubber having poor weather resistance such as natural rubber, its outer surface is covered with a coating rubber having excellent weather resistance (hereinafter sometimes referred to as "special rubber"). You are required to do so.

In the embodiment of the present invention shown in FIG. 1, as the rubber having excellent weather resistance suitable as the special rubber 14 on the outer surface of the laminated structure 13, for example, butyl rubber, acrylic rubber, polyurethane, silicone rubber, fluorine Examples thereof include rubber, polysulfide rubber, ethylene propylene rubber (EP and EPDM), hypalon, chlorinated polyethylene, ethylene vinyl acetate rubber, epichlorohydrin rubber, chloroprene rubber and the like. Of these, butyl rubber, polyurethane, ethylene propylene rubber, hypalon, chlorinated polyethylene, ethylene vinyl acetate rubber, and chloroprene rubber are particularly effective from the viewpoint of weather resistance. Further, in consideration of adhesiveness with rubber or the like constituting the soft plate, butyl rubber, ethylene propylene rubber, and chloroprene rubber are preferable, and ethylene propylene rubber is particularly preferable.

These rubber materials may be used alone or in combination of two or more. Further, in order to improve elongation and other physical properties, it may be blended with a commercially available rubber such as natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber and the like. Further, these rubber materials may be mixed with various fillers, antioxidants, plasticizers, softeners, oils and other compounds commonly used in rubber materials.
In particular, by adding cyclopentadiene or dicyclopentadiene resin in an amount of 10 to 40 parts by weight and 100 parts by weight of a rubber material, and further adding 5 to 20 parts by weight of a rosin derivative, the breaking property and the adhesion to a metal can be significantly Improved and highly advantageous. In this case, as the rosin derivative, the main components are abietic acid, pimaric acid and a mixture of carboxylic acids having a similar structure to various rosin-based esters, polymerized rosin, hydrogenated rosin, cured rosin, hyrosin, resin acid. Examples thereof include zinc and modified rosin.

In the present invention, basically, it is preferable that the outer skin layer is made of the above-mentioned special rubber having excellent weather resistance, and the thickness thereof is matched with the outer skin layer thickness T. If this is not possible due to other reasons, this special rubber 13
, The thickness t in FIG. 7 is not necessarily the outer skin layer thickness T
Does not have to match. In that case, the special rubber thickness t
Is 1 to 20 mm, preferably 2 to 15 mm, especially 2 to 10 mm
Is preferred. Such a special rubber B is a soft plate.
11, it is important to firmly adhere to the hard plate 12 and the flanges 4 and 5, but the adhesion is a. The rubber material of the soft plate 11 (hereinafter sometimes referred to as "internal rubber") and the special rubber 13 are simultaneously bonded. How to vulcanize and bond.

b A two-stage vulcanization bonding method in which only the internal rubber is vulcanized first and then the special rubber is vulcanized and bonded.

c Internal rubber and special rubber are separately vulcanized and then bonded with an adhesive.

It can be done easily. When the internal rubber and the special rubber are poorly adhered at the time of adhesion, a third rubber layer having good adhesiveness to both may be interposed therebetween.
Further, an additive for improving adhesiveness may be blended with the internal rubber and / or the special rubber.

As in the embodiment shown in FIG. 1, the edge portion of the hard plate is bulged into an arc shape or a shape similar to an arc and covered with a special rubber having an appropriate thickness, so that the local strain near the flange of the seismic isolation rubber is reduced. Further, it is possible to further reduce the average of the strain of the seismic isolation rubber and to reduce the absolute value of the local strain.

By the way, with the configuration shown in FIG. 1, even when the local strain in the vicinity of the flange becomes small, the local strain in other parts of the seismic isolation rubber becomes large, and the maximum local strain is reduced as a whole. It is also possible that nothing is common.

Therefore, it has been described above that the local strain in the vicinity of the flange is reduced, the local strain of the entire seismic isolation rubber is averaged, and the absolute value of the local strain in each part is reduced.

(I) The shape of the curved surface formed in the portion of the laminated structure that contacts the flange.

(Ii) Shape of the bulging part formed on the side end surface of the hard plate (iii) It is necessary to keep the balance of each element in order to sufficiently bring out the improvement effect due to the thickness of the special rubber covering the outer surface of the laminated structure. Most important However, the balance can be kept good only by the FEM calculation for large deformation developed by the present inventors.

In the present invention, as the material of the hard plate 12, metal, ceramics, plastics, FRP, polyurethane, wood, paper plate, slate plate, decorative plate, and the like can be used, and among them, steel plate is preferable. The soft plate 11 has rubber-like elasticity, and various vulcanized rubbers, organic materials such as unvulcanized rubber, and various materials such as foams thereof can be used. Is preferred.

To bond such a hard plate and a soft plate, an adhesive or co-vulcanization may be used.

Such a seismic isolation rubber of the present invention has characteristics such as vibration isolation (vibration prevention and vibration control) in addition to the seismic isolation action.

Hereinafter, the present invention will be described in more detail with reference to experimental examples.

Experimental Example 1 With respect to the seismic isolation rubber of the present invention as shown in FIG. 1, principal strains at various positions during deformation were determined.

The soft plate is a vulcanized rubber mainly composed of natural rubber,
A vulcanized rubber containing 27 parts by weight of dicyclopentadiene resin, 10 parts by weight of rosin, and carbon black, etc. for 100 parts by weight of rubber mainly composed of EPDM as a special rubber is used as a hard plate. I was there.

Further, a soft plate thickness, a hard plate thickness h, a hard plate length l, a special rubber thickness t, a shape ratio, a radius r of an arc serving as a bulge portion of a side end of the hard plate, and a laminated structure in contact with a flange. The radius L of the arc forming the curved surface of is as follows.

k = 10mm h = 2mm l = 70mm t = 5mm Shape ratio = 1 / 4k = 1.75 r = 1mm L = 0.92 × (h + k) = 11.04mm The seismic isolation rubber with this structure has compressive strain of 6% and shear strain. 100
A schematic view of the deformed shape when% is added is shown in FIG. Table 1 shows the FEM analysis values of the principal strain at each point shown in Fig. 13.

As a comparative example, the seismic isolation rubber (material shape ratio,
The same experiment was performed for the same rubber thickness and steel plate thickness), and the measured values of the principal strain at each point shown in FIG. 6 are also shown in Table 1.

From Table 1, it can be seen that the seismic isolation rubbers of the examples show a significant reduction in local strain on the tensile side and compression side near the flange. Averaging of the local strain of the seismic isolation rubber as a whole has been achieved. The effect of the invention is quite clear.

〔The invention's effect〕

Since the occurrence of local strain is extremely effectively reduced in the seismic isolation rubber of the present invention, damage and breakage of the seismic isolation rubber due to local strain are reduced, and the seismic isolation rubber has extremely excellent durability. Moreover, since it can be fixed to the building and the foundation via the flange, the building and the like can be supported stably.

Such a seismic isolation rubber of the present invention has been realized for the first time in the research relating to the present invention because it has become possible to quantitatively analyze the local strain generated in the seismic isolation rubber during deformation. It should be clearly distinguished from seismic rubber, and its academic and industrial significance is extremely large.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a seismic isolation rubber according to an embodiment of the present invention, and FIGS. 2 and 3 are sectional views showing a conventional example, in which (a) is normal and (b) is an earthquake. Indicates when it occurred. Fig. 4 is a diagram showing the FEM analysis results of general seismic isolation rubber, Fig. 5 is a cross-sectional view of the conventional seismic isolation rubber used for the analysis of principal strain, and Fig. 6 is the seismic isolation rubber of Fig. 5. It is a schematic diagram at the time of deformation. Figure 7 shows the first
FIG. 8 is an enlarged view of the VII part of the figure, FIG. 8 is a diagram showing an example of a curved surface near the flange, FIG. 9 is a partial sectional view of a conventional seismic isolation rubber, and FIG. a) to (c) are diagrams showing examples of the bulging portion of the side end surface of the hard plate, FIGS. 11 and 12 are sectional views of a conventional seismic isolation rubber, and FIG. 13 is a diagram of an example rubber in an experimental example. It is a schematic diagram at the time of deformation. 4, 5 ... Flange, 11 ... Soft plate, 12 ... Hard plate, 13 ... Laminated structure, 14 ... Special rubber, 20 ... Seismic isolation rubber.

Claims (5)

[Claims] 1. A seismic isolation rubber in which flanges are provided on the upper and lower surfaces of a laminated structure in which a plurality of rigid hard plates and soft plates having viscoelastic properties are alternately laminated.
A seismic isolation rubber provided with means for averaging the local strain of the entire structure by reducing the local strain in the vicinity of the flange.
As the cross-sectional area gradually increases toward the flange,
A seismic isolation rubber, the outer surface of which is a curved surface that is curved inward in an arcuate section or a shape similar to an arcuate section. 2. The arcuate longitudinal cross-section of the curved surface formed in the portion of the laminated structure which contacts the flange, with respect to the thickness h of the hard plate and the thickness k of the soft plate. The seismic isolation rubber according to claim 1, wherein the seismic isolation rubber has an arc shape having a radius L that satisfies the above condition. 3. The side end of the hard plate has a shape bulging outward in an arcuate shape or an arcuate shape in cross section, and the outer surface of the laminated structure is covered with a coated rubber having excellent weather resistance. The seismic isolation rubber according to claim 2, wherein 4. The arc-shaped cross section of the bulging portion formed on the side end surface of the hard plate is an arc shape having a radius r satisfying r ≧ 0.1 mm. The seismic isolation rubber described. 5. The rubber according to claim 3 or 4, characterized in that a rubber having a weather resistance that covers the outer surface of the laminated structure has a thickness of 1 to 30 mm. Seismic isolation rubber.